<?xml version="1.0" encoding="utf-8" standalone="no"?><Search><pages Count="198"><page Index="1" isMAC="true"><![CDATA[]]></page><page Index="2" isMAC="true"><![CDATA[Ancient Greek
Scientific Latin
Scientific Latin
Modern English
haematologica Journal of the European Hematology Association
Published by the Ferrata Storti Foundation
The origin of a name that reflects Europe’s cultural roots.
aÂma [haima] = blood
a·matow [haimatos] = of blood lÒgow [logos]= reasoning
haematologicus (adjective) = related to blood
haematologica (adjective, plural and neuter, used as a noun) = hematological subjects
The oldest hematology journal, publishing the newest research results. 2017 JCR impact factor = 9.090
Haematologica, as the journal of the European Hematology Association (EHA), aims not only to serve the scientific community, but also to promote European cultural identify.
]]></page><page Index="3" isMAC="true"><![CDATA[haematologica Journal of the European Hematology Association
Published by the Ferrata Storti Foundation
Editor-in-Chief
Luca Malcovati (Pavia)
Managing Director
Antonio Majocchi (Pavia)
Associate Editors
Omar I. Abdel-Wahab (New York), Hélène Cavé (Paris), Simon Mendez-Ferrer (Cambridge), Pavan Reddy (Ann Arbor), Andreas Rosenwald (Wuerzburg), Monika Engelhardt (Freiburg), Davide Rossi (Bellinzona), Jacob Rowe (Haifa, Jerusalem), Wyndham Wilson (Bethesda), Paul Kyrle (Vienna), Swee Lay Thein (Bethesda), Pieter Sonneveld (Rotterdam)
Assistant Editors
Anne Freckleton (English Editor), Cristiana Pascutto (Statistical Consultant), Rachel Stenner (English Editor), Kate O’Donohoe (English Editor), Ziggy Kennell (English Editor)
Editorial Board
Jeremy Abramson (Boston); Paolo Arosio (Brescia); Raphael Bejar (San Diego); Erik Berntorp (Malmö); Dominique Bonnet (London); Jean-Pierre Bourquin (Zurich); Suzanne Cannegieter (Leiden); Francisco Cervantes (Barcelona); Nicholas Chiorazzi (Manhasset); Oliver Cornely (Köln); Michel Delforge (Leuven); Ruud Delwel (Rotterdam); Meletios A. Dimopoulos (Athens); Inderjeet Dokal (London); Hervé Dombret (Paris); Peter Dreger (Hamburg); Martin Dreyling (München); Kieron Dunleavy (Bethesda); Dimitar Efremov (Rome); Sabine Eichinger (Vienna); Jean Feuillard (Limoges); Carlo Gambacorti-Passerini (Monza); Guillermo Garcia Manero (Houston); Christian Geisler (Copenhagen); Piero Giordano (Leiden); Christian Gisselbrecht (Paris); Andreas Greinacher (Greifswals); Hildegard Greinix (Vienna); Paolo Gresele (Perugia); Thomas M. Habermann (Rochester); Claudia Haferlach (München); Oliver Hantschel (Lausanne); Christine Harrison (Southampton); Brian Huntly (Cambridge); Ulrich Jaeger (Vienna); Elaine Jaffe (Bethesda); Arnon Kater (Amsterdam); Gregory Kato (Pittsburg); Christoph Klein (Munich); Steven Knapper (Cardiff); Seiji Kojima (Nagoya); John Koreth (Boston); Robert Kralovics (Vienna); Ralf Küppers (Essen); Ola Landgren (New York); Peter Lenting (Le Kremlin-Bicetre); Per Ljungman (Stockholm); Francesco Lo Coco (Rome); Henk M. Lokhorst (Utrecht); John Mascarenhas (New York); Maria-Victoria Mateos (Salamanca); Giampaolo Merlini (Pavia); Anna Rita Migliaccio (New York); Mohamad Mohty (Nantes); Martina Muckenthaler (Heidelberg); Ann Mullally (Boston); Stephen Mulligan (Sydney); German Ott (Stuttgart); Jakob Passweg (Basel); Melanie Percy (Ireland); Rob Pieters (Utrecht); Stefano Pileri (Milan); Miguel Piris (Madrid); Andreas Reiter (Mannheim); Jose-Maria Ribera (Barcelona); Stefano Rivella (New York); Francesco Rodeghiero (Vicenza); Richard Rosenquist (Uppsala); Simon Rule (Plymouth); Claudia Scholl (Heidelberg); Martin Schrappe (Kiel); Radek C. Skoda (Basel); Gérard Socié (Paris); Kostas Stamatopoulos (Thessaloniki); David P. Steensma (Rochester); Martin H. Steinberg (Boston); Ali Taher (Beirut); Evangelos Terpos (Athens); Takanori Teshima (Sapporo); Pieter Van Vlierberghe (Gent); Alessandro M. Vannucchi (Firenze); George Vassiliou (Cambridge); Edo Vellenga (Groningen); Umberto Vitolo (Torino); Guenter Weiss (Innsbruck).
Editorial Office
Simona Giri (Production & Marketing Manager), Lorella Ripari (Peer Review Manager), Paola Cariati (Senior Graphic Designer), Igor Ebuli Poletti (Senior Graphic Designer), Marta Fossati (Peer Review), Diana Serena Ravera (Peer Review)
Affiliated Scientific Societies
SIE (Italian Society of Hematology, www.siematologia.it)
SIES (Italian Society of Experimental Hematology, www.siesonline.it)
]]></page><page Index="4" isMAC="true"><![CDATA[Information for readers, authors and subscribers
Haematologica (print edition, pISSN 0390-6078, eISSN 1592-8721) publishes peer-reviewed papers on all areas of experi- mental and clinical hematology. The journal is owned by a non-profit organization, the Ferrata Storti Foundation, and serves the scientific community following the recommendations of the World Association of Medical Editors (www.wame.org) and the International Committee of Medical Journal Editors (www.icmje.org).
Haematologica publishes editorials, research articles, review articles, guideline articles and letters. Manuscripts should be prepared according to our guidelines (www.haematologica.org/information-for-authors), and the Uniform Requirements for Manuscripts Submitted to Biomedical Journals, prepared by the International Committee of Medical Journal Editors (www.icmje.org).
Manuscripts should be submitted online at http://www.haematologica.org/.
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Rates of the International edition for the year 2018 are as following:
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Disclaimer. Whilst every effort is made by the publishers and the editorial board to see that no inaccurate or misleading data, opinion or statement appears in this journal, they wish to make it clear that the data and opinions appearing in the articles or advertisements herein are the responsibility of the contributor or advisor concerned. Accordingly, the publisher, the editorial board and their respective employees, officers and agents accept no liability whatsoever for the consequences of any inaccurate or misleading data, opinion or statement. Whilst all due care is taken to ensure that drug doses and other quantities are presented accurately, readers are advised that new methods and techniques involving drug usage, and described within this journal, should only be followed in conjunction with the drug manufacturer’s own published liter- ature.
Direttore responsabile: Prof. Edoardo Ascari; Autorizzazione del Tribunale di Pavia n. 63 del 5 marzo 1955. Printing: Press Up, zona Via Cassia Km 36, 300 Zona Ind.le Settevene - 01036 Nepi (VT)
haematologica Journal of the European Hematology Association
Published by the Ferrata Storti Foundation
]]></page><page Index="5" isMAC="true"><![CDATA[13th Congress of the Albanian Association of Hematology Albanian Association of Hematology
Chairs: A Ivanaj, M Dimopoulos, G Gaidano, X Pivot November 5-6, 2018
Tirana, Albania
EBMT Severe Aplastic Anaemia and Autoimmune Diseases Working Parties - Joint Educational Course EBMT
Chairs: C Dufour, J Snowden, RP de la Tour, A Tobias November 15-17, 2018
Firenze, Italy
7th National Symposium "Young Hematologist" - "Hemostasis and Thrombosis"
Bulgarian Medical Society of Hematology Chairs: V Kaleva, M Guenova
November 16-17, 2018
Saints Constantine and Helena, Bulgaria
The American Society of Hematology 60th ASH Annual Meeting and Exposition
American Society of Hematology (ASH)
Chairs: A Thompson, M Crowther, M Sekeres, J Crispino, M Sola-Visner
December 1-4, 2018 San Diego, USA
EHA-SLCH Hematology Tutorial on Myeloid Malignancies and MDS
Chairs: G Ossenkoppele, V Gunawardena, HW Goonasekera
February 8-9, 2019 Colombo, Sri Lanka
haematologica Journal of the European Hematology Association
Published by the Ferrata Storti Foundation
EHA-SWG Scientific Meeting on Immunotherapy: The Advent of CAR T Cell Therapy for Hematological Malignancies
Chair: H Einsele, Co-chair: M Hudecek
February 14-16, 2019
Amsterdam, The Netherlands
EHA-AORK Hematology Tutorial on Lymphoma and Multiple Myeloma
Chair: D Kaidarova, Co-chairs: S Gabbasova
& B Afanasyev
March 14-16, 2019 Almaty, Kazakhstan
EHA Pediatric Course 2019 April 3-6, 2019
Sorrento, Italy
EHA-ROHS-RHS Hematology Tutorial on Real World Challenges and Opportunities in Diagnostics and Management of Onco-Hematological Patients Today Chairs: I Poddubnaya, E Parovnichikova
April 12-13, 2019 Moscow, Russia
24th Congress of EHA
European Hematology Association June 13-16, 2019
Amsterdam, The Netherlands
Calendar of Events updated on October 11, 2018
calendar of events
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Volume 103, Issue 11: November 2018
Cover Figure
haematologica Journal of the European Hematology Association
Published by the Ferrata Storti Foundation
Bone marrow smear from a patient with myelodysplastic syndrome showing a group of micromegakaryocytes. Courtesy of Prof. Rosangela Invernizzi.
Editorials
1753 Loss-of-function ferroportin disease: novel mechanistic insights and unanswered questions L. Tom Vlasveld and Dorine W. Swinkels
1756 To what extent can mathematical modeling inform the design of clinical trials? The example of safe dose reduction of tyrosine kinase inhibitors in responding patients with chronic myeloid leukemia
Joshua T. Schiffer and Charles A. Schiffer
1758 Older adults with acute myeloid leukemia treated with intensive chemotherapy: “old” prognostic algorithms may not apply Richard M. Stone and Coleman Lindsley
Review Article
1760 Preclinical human models and emerging therapeutics for advanced systemic mastocytosis Michel Arock et al.
Guideline Article
1772 European Myeloma Network recommendations on tools for the diagnosis and monitoring of multiple myeloma: what to use and when Jo Caers et al.
Articles
Hematopoiesis
1785 Alas1 is essential for neutrophil maturation in zebrafish Junwei Lian et al.
Iron Metabolism & its Disorders
1796 The SLC40A1 R178Q mutation is a recurrent cause of hemochromatosis and is associated with a novel pathogenic mechanism Chandran Ka et al.
Bone Marrow Failure
1806 Novel lineage depletion preserves autologous blood stem cells for gene therapy of Fanconi anemia complementation group A Jennifer E. Adair et al.
Phagocyte Biology & its Disorders
1815 Prognostic factors of Erdheim–Chester disease: a nationwide survey in Japan Takashi Toya et al.
Chronic Myeloid Leukemia
1825 Reduced tyrosine kinase inhibitor dose is predicted to be as effective as standard dose in chronic myeloid leukemia: a simulation study based on phase III trial data
Artur C. Fassoni et al.
1835 Treatment-free remission after two-year consolidation therapy with nilotinib in patients with chronic myeloid leukemia: STAT2 trial in Japan
Naoto Takahashi et al.
Acute Myeloid Leukemia
1843 Inhibition of protein disulfide isomerase induces differentiation of acute myeloid leukemia cells Justyna Chlebowska-Tuz et al.
Haematologica 2018; vol. 103 no. 11 - November 2018 http://www.haematologica.org/
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Published by the Ferrata Storti Foundation
1853 Genetics of acute myeloid leukemia in the elderly: mutation spectrum and clinical impact in intensively treated patients aged 75 years or older
Victoria V. Prassek et al.
1862 MDM2- and FLT3-inhibitors in the treatment of FLT3-ITD acute myeloid leukemia, specificity and efficacy of NVP-HDM201 and midostaurin
Katja Seipel et al.
Acute Lymphoblastic Leukemia
1873 Radiation exposure from computerized tomography and risk of childhood leukemia: Finnish register-based case-control study of childhood leukemia (FRECCLE)
Atte Nikkilä et al.
Chronic Lymphocytic Leukemia
1881 Adherence to the Western, Prudent, and Mediterranean dietary patterns and chronic lymphocytic leukemia in the MCC-Spain study Marta Solans et al.
1889 Safety of obinutuzumab alone or combined with chemotherapy for previously untreated or relapsed/refractory chronic lymphocytic leukemia in the phase IIIb GREEN study
Véronique Leblond et al.
Non-Hodgkin-Lymphoma
1899 Inferior survival in high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements is not associated with MYC/IG gene rearrangements
Ellen D. McPhail et al.
1907 PD-L1+ tumor-associated macrophages and PD-1+ tumor-infiltrating lymphocytes predict survival in primary testicular lymphoma
Marjukka Pollari et al.
Stem Cell Transplantation
1915 A phase II/III randomized, multicenter trial of prednisone/sirolimus versus prednisone/sirolimus/calcineurin inhibitor for the treatment of chronic graft-versus-host disease: BMT CTN 0801
Paul A. Carpenter et al.
Coagulation & its Disorders
1925 N-linked glycosylation modulates the immunogenicity of recombinant human factor VIII in hemophilia A mice Jesse D. Lai et al.
Letters to the Editor
Letters are available online only at www.haematologica.org/content/103/11.toc
e496 L-leucine increases translation of RPS14 and LARP1 in erythroblasts from del(5q) myelodysplastic syndrome patients Erica Bello et al.
http://www.haematologica.org/content/103/11/e496
e501 The long non-coding RNA landscape in juvenile myelomonocytic leukemia Mattias Hofmans et al.
http://www.haematologica.org/content/103/11/e501
e505 Loss of DEP-1 (Ptprj) promotes myeloproliferative disease in FLT3-ITD acute myeloid leukemia Anne Kresinsky et al.
http://www.haematologica.org/content/103/11/e505
e510 Concomitant WT1 mutations predict poor prognosis in acute myeloid leukemia patients with double mutant CEBPA Feng-Ming Tien et al.
http://www.haematologica.org/content/103/11/e510
Haematologica 2018; vol. 103 no. 11 - November 2018 http://www.haematologica.org/
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Published by the Ferrata Storti Foundation
e514 Phase 3 results for vosaroxin/cytarabine in the subset of patients ≥60 years old with refractory/early relapsed acute myeloid leukemia Farhad Ravandi et al.
http://www.haematologica.org/content/103/11/e514
e519 Reducing mortality in newly diagnosed standard-risk acute promyelocytic leukemia in elderly patients treated with arsenic trioxide requires major reduction of chemotherapy: a report by the French Belgian Swiss APL group (APL 2006 trial)
Ramy Rahmé et al.
http://www.haematologica.org/content/103/11/e519
e522 Transcriptional activities of DUX4 fusions in B-cell acute lymphoblastic leukemia Yosuke Tanaka et al.
http://www.haematologica.org/content/103/11/e522
e527 Pentraxin-3 polymorphisms and invasive mold infections in acute leukemia patients receiving intensive chemotherapy Anne-Sophie Brunel et al.
http://www.haematologica.org/content/103/11/e527
e531 A reversible carnitine palmitoyltransferase (CPT1) inhibitor offsets the proliferation of chronic lymphocytic leukemia cells Elena Gugiatti et al.
http://www.haematologica.org/content/103/11/e531
e537 In vitro and in vivo activity of a new small-molecule inhibitor of HDAC6 in mantle cell lymphoma Montserrat Pérez-Salvia et al.
http://www.haematologica.org/content/103/11/e537
e541 Lenalidomide plus bendamustine-rituximab does not overcome the adverse impact of TP53 mutations in mantle cell lymphoma Christian Winther Eskelund et al.
http://www.haematologica.org/content/103/11/e541
e544 Mutational screening of newly diagnosed multiple myeloma patients by deep targeted sequencing Yanira Ruiz-Heredia et al.
http://www.haematologica.org/content/103/11/e544
Case Reports
Case Reports are available online only at www.haematologica.org/content/103/11.toc
e549 A double Philadelphia chromosome-positive chronic myeloid leukemia patient, co-expressing P210BCR-ABL1 and P195BCR-ABL1 isoforms Raquel Vinhas et al.
http://www.haematologica.org/content/103/11/e549
e553 Clonally related diffuse large B-cell lymphoma and interdigitating dendritic cell sarcoma sharing MYC translocation Yotaro Ochi et al.
http://www.haematologica.org/content/103/11/e553
e557 Comprehensive molecular characterization of a heavy chain deposition disease case Sébastien Bender et al.
http://www.haematologica.org/content/103/11/e557
Haematologica 2018; vol. 103 no. 11 - November 2018 http://www.haematologica.org/
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L. Tom Vlasveld1 and Dorine W. Swinkels2
1Department of Internal Medicine, Haaglanden Medical Center, Location Bronovo, The Hague and 2Translational Metabolic Laboratory, Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, the Netherlands
E-mail: dorine.swinkels@radboudumc.nl doi:10.3324/haematol.2018.203315
Ferroportin, a 571 amino acid cation transporter encoded by the SLC40A1 gene, is the only known human cellular iron exporter and primarily expressed in the basolateral membrane of duodenal enterocytes, macrophages, and hepa- tocytes.1,2 By regulating ferroportin-mediated iron export in these cells, the hepatocyte-derived peptide hormone hepcidin plays a central role in intestinal iron resorption, macrophage iron recycling and hepatic iron storage (Figure 1A).3 Functional studies reveal the internalization of ferroportin upon hepcidin binding with subsequent ubiquitination of the protein result- ing in the diminution of cellular iron export. The mechanism of the inhibition of cellular iron efflux is not fully elucidated.4 Genetic ferroportin variants result in autosomal dominantly inherited hereditary hemochromatosis (HH) type 4 or ferro- portin disease which is traditionally divided into two entities primarily based on the pattern of cellular iron distribution. Classical ferroportin disease (type 4A) is characterized by macrophage iron retention and decreased circulating iron avail- ability for erythropoiesis, and is clinically recognized by the presence of elevated serum ferritin concentrations with low to normal transferrin saturation (TSAT) and poor tolerance to phlebotomy. Non-classical (atypical, type 4B or ferroportin- associated HH) ferroportin disease is characterized by parenchymal (hepatocellular) iron overload with both elevated serum ferritin and TSAT and is indistinguishable from other forms of HH.5
To assess the pathogenicity of a ferroportin variant function- al studies on iron export and/or ferroportin expression are per- formed in cell-lines (mostly HEK293T, a human embryonic kidney cell line) transfected with the variant. However, inter- pretation of results may be hampered by these studies being done in non-enterocyte and non-macrophage cell lines. Moreover, comparability between reports may have short- comings, since iron loading and hepcidin exposure protocols, the mode of iron export measurements and the determination of ferroportin expression differ largely between studies. Nevertheless, the results obtained are quite consistent, in that patients with the type 4A phenotype are mostly associated with loss-of-function ferroportin variants which display decreased membrane expression and/or iron transport in func- tional assays, while patients with the type 4B phenotype have gain-of-function variants with preserved membrane expres- sion and iron export capacity even after hepcidin exposure. Notwithstanding a different pattern of cellular iron distribu- tion, a review of numerous case series of ferroportin disease reveals that in those patients who underwent magnetic reso- nance imaging (MRI) or liver biopsy, hepatic iron content is increased for both types of ferroportin disease. These observa- tions indicate that loss-of-function variants also result in body iron overload.
Variety in iron parameters reported for patients with ferro- portin variants is large and the correlation between iron export capacity in functional studies and clinical phenotype is poor,
especially on an individual level. The establishment of the pathogenicity of ferroportin variants may not only be impeded by the presence of iron homeostasis modulating co-morbidi- ties such as alcohol consumption and liver steatosis, but also by the limited applicability of in silico prediction models in the absence of a fully elucidated three-dimensional (3D) structure of ferroportin. In the most widely accepted secondary struc- ture, ferroportin comprises 12 helices located in 12 transmem- brane (TM) domains bound via six extracellular (ES) and five intracellular (IS) segments with a large intracellular loop between the 6th and 7th transmembrane helix and an intracellu- larly located N- and C-terminus. The available 3D models are based on a comparison with membrane transport proteins from a wide range of other species with only a 10 - 24% sequence homology and a maximal 40% similarity. Two stud- ies, using E. coli glycerol-3-phosphate transporter GlpT and lac- tose permease LacY or the Bdellovibrio bacteriovorus Bd2019 iron transporter as template, respectively, reveal an open inward and an open outward structure with an intra- and extracellular gate between the 6th and 7th transmembrane domain.6,7 Site mutagenetic and conformational studies revealed the residues, located at IS1, IS2 and IS5, that are important in intracellular gate interaction and the residues, located at TM1, TM12 and ES1 and ES4, that are involved in extracellular gate interaction. These studies also identified ferroportin residues that are essential for binding and ubiquitination of hepcidin and may be involved in iron binding and egress. The unequivocally hep- cidin-resistant gain-of-function ferroportin variants Cys326Ser, Tyr501Cys, Asp504Asn and Tyr64Asn and His507Arg are reported to have impaired hepcidin binding and hepcidin- dependent ubiquitination, respectively. In the open outward structure, variants causing impaired hepcidin binding were found to be localized within the extracellular gate, while vari- ants causing impaired ubiquitination were found in the periph- ery of the molecule, suggesting that these latter variants inter- fere with appropriate folding after hepcidin binding.8 These findings provide a molecular basis for the observed cellular dis- tribution pattern of the type 4B iron overload in patients and the behavior in functional tests performed for these hepcidin- resistant gain-of-function variants (Figure 1B).
The study by Ka et al., published in this issue, provides inter- esting insights into the pathophysiologic mechanisms involved in ferroportin disease caused by loss-of-function variants. They describe 22 patients from six independent families with hyper- ferritinemia, a normal TSAT and the heterozygous presence of the Arg178Gln variant. The serum hepcidin levels determined in two patients were above the reference range. The hepatic iron content, estimated by MRI methodology in three of the patients, was mildly elevated and a liver biopsy, performed in one patient, revealed predominant iron deposition in Kupffer cells. Although Arg178Gln displayed a reduced export of 55Fe out of transfected HEK293T cells, the variant was properly localized on the cellular membrane with disappearance after
haematologica | 2018; 103(11)
EDITORIALS
1753
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hepcidin exposure. Based on both the clinical phenotype and functional tests the variant was assigned as a hepcidin sensitive loss-of-function variant. In the open outward con- formation of the 3D structure, using Bdellovibrio bacteriovorus Bd2019 as the template, the demonstrated non-covalent interaction between Arg178 and Asp473 (located on the N- and C-lobe, respectively) was assumed to be involved in the stabilization of the open outward conformation needed to preserve iron egress. Indeed, the Asp473Ala ferroportin
variant was also properly expressed on the membrane with a nearly total loss of iron export capacity. In most loss-of- function variants the abolished iron transport is attributed to defective expression of ferroportin on the membrane. Ka et al., however, provide evidence for interference in the sta- bilization of the conformation state, i.e., the open outward state, in the Arg178Gln variant as an alternative mechanism for diminished iron transport, despite the proper membrane expression of this variant. Further exploration of the amino-
Figure 1. Model displaying cellular iron flows in patients with loss-of-function ferroportin variants as compared to physiological conditions and patients with gain- of-function ferroportin variants and IRIDA. Ferroportin activity in the enterocyte, macrophage and hepatocyte in physiological steady state conditions (A), hepcidin- resistant gain-of-function (GOF) (B), iron refractory iron deficiency anemia (IRIDA) (C), loss-of-function (LOF) with mislocalisation on the membrane (D), membrane expressed destabilized and hepcidin sensitive LOF (E), membrane expressed destabilized LOF (F). Physiologically, iron availability for erythropoiesis (in the form of transferrin bound iron ( ) is systemically regulated by the inhibitory effects of the hepatocyte-derived hormone hepcidin ( ) on the activity of ferroportin (  ). This regulatory system contributes to the regulation of intracellular iron ( ) and ferritin bound iron (  ) levels, serum iron (  ) concentration, transferrin saturation (TSAT) (  ) and serum ferritin (  ) concentration. In hepcidin-resistant GOF, there is an increased non-impressionable iron export out of macrophages with continuous ente- rocyte iron transport with iron deposition in hepatocytes. In IRIDA, ferroportin action is inhibited by (for body iron status) inappropriately elevated hepcidin leading to decreased enterocyte iron resorption and diminished ferric-transferrin availability for the erythroblast with the sequestering of some iron, derived from ery- throphagocytosis, within the macrophage. In patients with LOF variants there is decreased iron transport out of the macrophage leading to iron sequestration in these cells, but the mechanism of the apparently relatively increased enterocyte iron export with subsequent body iron overload is not yet fully elucidated. Clinically observed changes in serum iron, and ferritin concentration and TSAT in the various conditions are depicted by the size of the rectangles in the lower right-hand side of the panels. DMT: divalent metal transporter; tfr: transferrin receptor-1; fe: iron. Transferrin (  ).
1754
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acid interaction network in various ferroportin conforma- tion states may reveal additional sites essential for stabiliza- tion and provide molecular explanation for defective iron egress in variants without defective membrane expression, such as Arg88Gly, Leu129Pro, Ile152Phe and Asn174Ile.9-11
Notwithstanding the importance of this finding, it does not clarify the iron overload observed in these patients. Moreover, as reported by Ka and colleagues, it is notable that the patients with a loss-of-function variant ferroportin, that completely disappears from the cellular membrane after exposure to hepcidin, have no anemia and intensive phlebotomy regimens were reported to be well tolerated. In patients with defective iron export transport due to a loss- of-function variant, either due to mislocalization or improp- er folding, one might expect diminished enterocyte iron absorption leading to a phenotype similar to that described for iron-refractory iron deficiency (IRIDA). In IRIDA, muta- tions in the TMPRSS6 gene result in inappropriately elevat- ed serum hepcidin levels with diminished ferroportin activ- ity and a variable degree of iron deficiency anemia, unre- sponsive to oral iron treatment, and intra-enterocyte iron retention in experimental animals (Figure 1C).12,13 Experimental animals with diminished ferroportin activity due to monoallelic wild-type ferroportin expression also display iron deficiency anemia.2 This is in contrast to the situation in patients with diminished ferroportin activity due to loss-of-function ferroportin variants which is char- acterized by iron overload, normal circulating hemoglobin concentrations and absence of intra-enterocyte iron (evalu- ated in a limited number of patients) (Figure 1D,E).14 It appears that in the enterocyte diminished ferroportin activ- ity due to decreased activity of wild-type ferroportin has a different effect on iron export capacity than decreased fer- roportin activity caused by a loss-of-function variant. In addition, the impact of loss-of-function variants on iron export capacity may be different between macrophages and enterocytes, and the results of the functional studies in HEK293T cells are more predictive for macrophage iron handling. It has been suggested that in patients with loss- of-function variants the remaining monoallelic expressed wild-type ferroportin protein would be sufficient to pre- serve iron export in cells with low iron turnover, such as enterocytes, but insufficient to maintain iron export capac- ity in cells with high iron turnover, such as macrophages, with subsequent intracellular iron retention in these cells.5 However, this theory may not provide a full explanation for the state of iron overload in these patients. While the activity of ferroportin in both enterocytes and macrophages in the systemic regulation of iron homeosta- sis is mediated by hepcidin, there is a considerable amount of experimental data indicating that the regulation of ferro- portin expression and activity differ between enterocytes and macrophages. These data include differences in intra- cellular regulatory mechanisms that fine-tune ferroportin membrane expression as well as differences in ferroportin
activity upon various systemic stimuli.15-20 The study by Ka et al. contributes to our understanding of the pathogenic mechanisms involved in decreased ferroportin activity by loss-of-function variants. Studies focused on the conse- quences of these variants on enterocyte iron handling are warranted to further comprehend the pathophysiology of this intriguing iron overload disorder.
References
1. Abboud S, Haile DJ. A novel mammalian iron-regulated protein involved in intracellular iron metabolism. J Biol Chem. 2000;275 (26):19906-19912.
2. Donovan A, Lima CA, Pinkus JL, et al. The iron exporter ferroportin/Slc40a1 is essential for iron homeostasis. Cell Metab. 2005;1(3):191-200.
3. Ganz T, Nemeth E. Hepcidin and iron homeostasis. Biochim Biophys Acta. 2012;1823(9):1434-1443.
4. NemethE,TuttleMS,PowelsonJ,etal.Hepcidinregulatescellulariron efflux by binding to ferroportin and inducing its internalization. Science. 2004;306(5704):2090-2093.
5. Pietrangelo A. The ferroportin disease: pathogenesis, diagnosis and treatment. Haematologica. 2017;102(12):1972-1984.
6. Bonaccorsi di Patti MC, Polticelli F, Cece G, et al. A structural model of human ferroportin and of its iron binding site. FEBS J. 2014;281 (12):2851-2860.
7. Taniguchi R, Kato HE, Font J, et al. Outward- and inward-facing struc- tures of a putative bacterial transition-metal transporter with homology to ferroportin. Nat Commun. 2015;6:8545.
8. Aschemeyer S, Qiao B, Stefanova D, et al. Structure-function analysis of ferroportin defines the binding site and an alternative mechanism of action of hepcidin. Blood. 2018;131(8):899-910.
9. Moreno-CarraleroMI,Munoz-MunozJA,Cuadrado-GrandeN,etal.A novel mutation in the SLC40A1 gene associated with reduced iron export in vitro. Am J Hematol. 2014;89(7):689-694.
10. Le Gac G, Ka C, Joubrel R, et al. Structure-function analysis of the human ferroportin iron exporter (SLC40A1): effect of hemochromato- sis type 4 disease mutations and identification of critical residues. Hum Mutat. 2013;34(10):1371-1380.
11. Callebaut I, Joubrel R, Pissard S, et al. Comprehensive functional anno- tation of 18 missense mutations found in suspected hemochromatosis type 4 patients. Hum Mol Genet. 2014;23(17):4479-4490.
12. DeFalcoL,SanchezM,SilvestriL,etal.Ironrefractoryirondeficiency anemia. Haematologica. 2013;98(6):845-853.
13. FolguerasAR,deLaraFM,PendasAM,etal.Membrane-boundserine protease matriptase-2 (Tmprss6) is an essential regulator of iron home- ostasis. Blood. 2008;112(6):2539-2545.
14. Corradini E, Montosi G, Ferrara F, et al. Lack of enterocyte iron accu- mulation in the ferroportin disease. Blood Cells Mol Dis. 2005;35(3):315-318.
15. ZhangDL,GhoshMC,RouaultTA.Thephysiologicalfunctionsofiron regulatory proteins in iron homeostasis - an update. Front Pharmacol. 2014;5:124.
16. Drakesmith H, Nemeth E, Ganz T. Ironing out ferroportin. Cell Metab. 2015;22(5):777-787.
17. Canonne-HergauxF,DonovanA,DelabyC,etal.Comparativestudies of duodenal and macrophage ferroportin proteins. Am J Physiol Gastrointest Liver Physiol. 2006;290(1):G156-163.
18. Theurl I, Aigner E, Theurl M, et al. Regulation of iron homeostasis in anemia of chronic disease and iron deficiency anemia: diagnostic and therapeutic implications. Blood. 2009;113(21):5277-5286.
19. Jacolot S, Ferec C, Mura C. Iron responses in hepatic, intestinal and macrophage/monocyte cell lines under different culture conditions. Blood Cells Mol Dis. 2008;41(1):100-108.
20. Chaston T, Chung B, Mascarenhas M, et al. Evidence for differential effects of hepcidin in macrophages and intestinal epithelial cells. Gut. 2008;57(3):374-382.
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Editorials
To what extent can mathematical modeling inform the design of clinical trials? The example of safe dose reduction of tyrosine kinase inhibitors in responding patients with chronic myeloid leukemia
Joshua T. Schiffer1,2 and Charles A. Schiffer3
1Vaccine and Infectious Diseases and Clinical Research Divisions, Fred Hutchinson Cancer Research Center, Seattle, WA; 2Department of Medicine, University of Washington, Seattle, WA and 3Department of Oncology Wayne State University School of Medicine, Karmanos Cancer Institute, Detroit, MI, USA
E-mail: schiffer@karmanos.org doi:10.3324/haematol.2018.201897
The development of the tyrosine kinase inhibitors (TKIs) that inhibit the BCR/ABL oncoprotein driving the growth and persistence of chronic myeloid leukemia (CML) is one of the most remarkable advances in anti-cancer treatment in recent decades, and has served as the model, if not the Platonic ideal, for targeted therapies of other cancers. It remains standard practice to administer TKIs indefinitely because of concern about relapse should compliance be erratic or therapy stopped. However, a number of recent trials have demonstrated that approxi- mately 50% of patients whose transcript levels were either extremely low or undetectable for at least 2-3 years using sensitive polymerase chain reaction (PCR) assays, have not relapsed after therapy was stopped with many patients relapse free for more than five years after discontinuation.1,2 Remarkably, almost all relapses occurred within the first 6- 8 months after therapy cessation. The mechanism(s) by which CML remains dormant is not known, although immunological explanations are proposed, and the only predictors of continued remission are longer durations of TKI therapy and PCR negativity.
The benefits of these so-called “treatment-free remis- sions”3 are obvious, and include substantially reduced costs (CML-directed TKIs also served as the prototype for the obscene pricing of “targeted” agents),4 decreases in the potential for serious longer term organ toxicities (fortunate- ly very rare with imatinib5), elimination of the often both- ersome, low-grade chronic side-effects such as fatigue and diarrhea, as well as the ability to plan for pregnancies in younger patients. But, it is estimated that less than 20% of patients who are started on TKI treatment will be able to successfully discontinue therapy. It is likely, however, that some of these same benefits would be achieved if it were possible to reduce the dose of the TKIs without loss of dis- ease control. Indeed, the selection of doses and schedule for many drugs is often based on very small, under-pow- ered trials with relatively few subsequent attempts to deter- mine whether lower doses might result in similar out- comes. In this regard, it was recently shown in a large phase II trial in newly diagnosed patients in chronic phase that a starting dose of 50 mg of dasatinib seems to produce the same response rate as the “standard” dose of 100 mg with perhaps fewer side-effects.6,7
In this issue of the Journal, Fassoni et al. propose what they consider to be a safe strategy of dose reduction of TKIs for CML patients in chronic phase based on mathematical models generated from large recently generated clinical trial data.8 The authors evaluated patients who were in major molecular response (MMR) for at least one year, defined as
a greater than 3 log reduction in transcripts from baseline, and who had received imatinib therapy for more than three years. Their model concludes that, for most patients, halv- ing the dose of the TKI will maintain the current level of response, albeit with a high likelihood of a temporary increase in transcript levels which return to baseline after continued treatment with the reduced dose.
Fassoni et al.’s paper8 highlights the crucial role that math- ematical models can play in providing a mechanistic under- pinning of observed data, and in influencing therapeutic strategies. As a general principle, differential equation- based models are a necessary tool to capture non-linearity in biomedical datasets. CML treatment involves the cou- pling of mechanisms governing tumor cell division, transi- tion rates between progenitor cells and terminally differen- tiated tumor cells, anti-tumor immune responses and the selective pressure of TKIs. The non-linearity inherent in a model which captures the dynamics of this system can yield counterintuitive and useful predictions, such as Fassoni et al.’s calculation that the increase in BCR/ABL lev- els that may occur following TKI dose reduction is transito- ry.8 Fassoni et al. hypothesize that an increase in transcripts is due to a self-limited increase in proliferating leukemia stem cells (LSCs), rather than mutations leading to TKI resistance or changes in the underlying dynamics of quies- cent, non-proliferating LSCs.8
Mathematical modeling as a field would benefit from some demystification. Well-designed models represent nothing more than in silico experiments where models with competing structures and mechanistic assumptions are compared for their ability to fit to observed data. Fassoni et al.’s model recapitulates data from selected patients from the IRIS and CML IV trials in whom the pattern of second phase decrease in transcripts is thought to result from slow depletion of quiescent LSCs. This depletion is predicted to occur independently of TKI dose reduction because the transition from quiescent to proliferating LSC, rather than incomplete efficacy of TKIs, is the rate-limiting step for CML eradication during MMR. The model’s generalizabili- ty to patients with an adequate treatment response is fur- ther supported by the scalability of its key parameters gov- erning transitions between quiescent and proliferating LSCs across all patients. Finally, the model’s main prediction, that TKI dose reduction will not usually lead to loss of MMR, is qualitatively consistent with interim analyses from the DESTINY trial, a study in which 174 participants under- went 50% dose reduction as the initial phase of a “stop- ping” trial.9 It is not known whether the transcript increases seen in some of these patients at the reduced dose would
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have resolved, because the protocol called for restarting therapy if MMR was lost. Thus, to implement their recom- mendation in a subsequent clinical trial, clinicians would have to resist the current dogma to resume the higher dose or to switch to another TKI should the levels increase.
How then should the model’s enticing predictions be interpreted? Similar to in vitro models or animal models which aim to recapitulate key features of human disease, the primary role of mathematical models is to generate a hypothesis for a definitive test of concept studies in humans, rather than providing “proof” of the concept. Accordingly, mathematical model simulations of clinical tri- als can critically inform the design of clinical trials them- selves, but should never replace them. Indeed, the fact that Fassoni et al.’s model neglects several potential reasons for treatment failure in patients following dose reduction, such as de novo loss of immunological control or TKI resistance, highlights the point that the model’s novel hypotheses need to be tested.
Fassoni et al.’s simulations validate the concept that effec- tive TKI dose reduction is biologically plausible. Moreover, the output of the model provides useful information for TKI dose selection and sampling frequency in subsequent clini- cal trials. Model output suggests that the amount of TKI dose reduction may be individualized, based partly on observed BCR/ABL kinetics during the initial phase of ther- apy, which can then be used to derive two key parameters: 1) leukemic stem cell activation; and 2) TKI efficacy. Estimation of these parameters will require frequent BCR/ABL measurements during both primary and second phases of TKI therapy, an important consideration for trial design.
Most importantly, the modeling provides informed crite- ria for assessing treatment failure after dose reduction, and specifically recommends that investigators should not immediately classify increases in BCR-ABL transcripts as treatment failures. Rather, the model suggests that increases in BCR-ABL ratio could be permitted for as long as a year, at which point second phase decay would be expected to occur. Again, sampling following dose reduction must be frequent enough to allow model fitting that precisely char- acterizes this phenomenon. A third critical parameter, the LSC proliferation rate, can only be estimated following TKI dose reduction and could theoretically be leveraged to
make dose adjustments in real time. Finally, because the model predicts effect size, it could also theoretically be used to inform power calculations to project an adequate sample size for ‘proof of concept’ trials.
To understand the importance of these findings, one only need consider the situation in which a priori mathematical modeling is not performed, and TKI dose reduction is for- mally tested and labeled a failure based on what could have been only a temporary increase in BCR/ABL transcript lev- els. This would represent a spurious rejection of an impor- tant and valid scientific hypothesis, as well as a waste of resources. It is likely that these types of errors are not uncommon in clinical trial design, and that many could be predicted a priori with the use of strategic mathematical modeling.
References
1. Mahon FX, Réa D, Guilhot J, et al. Discontinuation of imatinib in patients with chronic myeloid leukaemia who have maintained com- plete molecular remission for at least 2 years: the prospective, multi- centre Stop Imatinib (STIM) trial. Lancet Oncol. 2010;11(11):1029- 1035.
2. RossDM,BranfordS,SeymourJF,etal.Safetyandefficacyofimatinib cessation for CML patients with stable undetectable minimal residual disease: results from the TWISTER study. Blood. 2013;122(4):515-522.
3. Hughes TP, Ross DM. Moving treatment-free remission into main- stream clinical practice in CML. Blood. 2016;128(1):17-23.
4. Experts in Chronic Myeloid Leukemia. The price of drugs for chronic myeloid leukemia (CML) is a reflection of the unsustainable prices of cancer drugs: from the perspective of a large group of CML experts. Blood. 2013;121(22):4439-4442.
5. Gambacorti-PasseriniC,AntoliniL,MahonFX,etal.Multicenterinde- pendent assessment of outcomes in chronic myeloid leukemia patients treated with imatinib. J Natl Cancer Inst. 2011;103(7):553-561.
6. NaqviK,JabbourE,SkinnerJ,etal.Earlyresultsoflowerdosedasatinib (50 mg daily) as frontline therapy for newly diagnosed chronic-phase chronic myeloid leukemia. Cancer. 2018;124(13):2740-2747.
7. Schiffer CA. The evolution of dasatinib dosage over the years and its relevance to other anticancer medications. Cancer. 2018;124(13):2687- 2689.
8. Fassoni AC, Baldow C, Roeder I, Glauche I. Reduced tyrosine kinase inhibitor dose is predicted to be as effective as standard dose in chronic myeloid leukemia: a simulation study based on phase III trial data. Hematologica. 2018 Jun 28. [Epub ahead of print]
9. Clark RE, Polydoros F, Apperley JF, et al. De-escalation of tyrosine kinase inhibitor dose in patients with chronic myeloid leukaemia with stable major molecular response (DESTINY): an interim analy- sis of a non-randomised, phase 2 trial. Lancet Haematol. 2017;4(7): e310-e316.
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Editorials
Older adults with acute myeloid leukemia treated with intensive chemotherapy: “old” prognostic algorithms may not apply
Richard M. Stone and Coleman Lindsley
Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
E-mail: rstone@partners.org doi:10.3324/haematol.2018.201848
The notion that older adults with acute myeloid leukemia (AML) represent a major therapeutic chal- lenge due to host biological factors and intrinsic dis- ease features leading to poor outcomes is accepted by con- sensus. Older adults have diminished stem cell reserve, more frequent comorbid medical conditions, and decreased ability to excrete chemotherapy compared to younger patients, in part leading to a relatively increased rate of mor- tality from induction treatment.1 Moreover, AML that arises in the older population can exhibit features of intrinsic chemo-resistance exemplified by a higher expression of proteins that extrude chemotherapy, a higher proportion of adverse cytogenetic abnormalities,2 and a higher frequency of gene mutations associated with antecedent myeloid dis- ease, which are, in turn, associated with an elevated rate of disease resistance.3 Based on this unfavorable balance of response and toxicity, many believe that older patients, especially those over the age of 75, should as a whole be treated with less intensive therapies: usually a hypomethy- lating agent (azacytidine or decitabine) in the USA or low- dose cytarabine.4 In counterpoint, a population-based study from Sweden suggested that older adults may benefit from intensive treatment, while others have shown that the genetic characteristics5 of AML in older patients may dis- criminate subgroups with distinct clinical responses to intensive therapy.3 For example, patients with de novo AML genetic alterations have a higher likelihood of responding to induction therapy, while both ‘secondary-type’ AML muta- tions (those associated with AML arising after a prodromic myelodysplastic syndrome) and TP53 mutations are associ- ated with more resistant disease.3 The challenge facing the field is how to incorporate contrasting data from large stud- ies of heterogeneous patient populations that may lack suf- ficient data with regards to genetic variables and smaller studies with detailed clinical information and genetic anno- tation, but limited statistical power to identify independent genetic effects. The debate about ‘3+7’ chemotherapy ver- sus non-intensive therapy for older adults with AML contin- ues.6
How do the data provided by the German Austrian AML Study Group7 add to the discussion? Their study has several important strengths. First, only patients older than the age of 74 were included, enabling a distinct and focused evalu- ation of this under-studied population. Second, all patients received the same intensive induction chemotherapy on an AML Cooperative Group protocol,8 which compared stan- dard induction chemotherapy with thioguanine, daunoru- bicin, and cytarabine (TAD9) with a high-dose cytara- bine/mitoxantrone induction. Patients whose bone marrow samples showed residual AML on day 15 were to receive high-dose cytarabine/mitoxantrone. The doses of chemotherapy were attenuated in older adults. Third, the
authors performed targeted, next-generation sequencing of 64 genes known to be mutated in AML, paired with focused assessment of FLT3-ITD, NPM1, and CEBPA muta- tions by standard laboratory-validated methodologies. They looked at outcomes according to number and type of mutations along with other potentially relevant data such as patient’s age, cytogenetics, risk group by one of two clas- sifications systems, and randomized treatment assignment. More details about why these older adults received chemotherapy as opposed to other therapies would have been welcome. Were they particularly fit? Some actually had a performance status worse than 2, which is an adverse prognostic factor for response to chemotherapy.2 Obviously, no comparative group of patients treated con- temporaneously with less intensive chemotherapy can be provided.
The analysis highlights that some commonly employed prognostic factors in younger adult AML patients, including FLT3-ITD and NPM1, did not have the same relevance in the older patients. The European LeukemiaNet9 and Medical Research Council10 prognostic algorithms simply were not developed based on data from intensively treated patients in this age group. Given the distinct clinical and molecular features in this age group, one can begin to grasp why the ‘usual prognostic rules’ noted in younger patients may not apply. The findings in this cohort of 151 patients aged over 74 years old confirm those of published studies showing that there is a preponderance of gene mutations associated with myelodysplastic syndromes and clonal hematopoiesis of indeterminate potential in AML in older individuals.3,11,12 In a previous study, outcomes after 3+7- based chemotherapy were particularly poor in patients with histologically confirmed secondary AML or de novo AML harboring myelodysplastic syndrome-associated gene mutations.3 Although few patients in this study were older tha 74, it raised the idea that gene mutations suggestive of antecedent myelodysplastic syndromes (SRSF2, SF3B1, U2AF1, ZRSR2, BCOR, EZH2, ASXL1, STAG2) may high- light a subgroup of older patients with more chemoresis- tant disease. By contrast, older patients without such muta- tions had a much more favorable induction success rate and a 50% event-free survival.3
In the cohort reported by Prassek et al.,7 35% of the patients died during induction. This finding has important clinical implications, as older patients among a group of seemingly fit-for-chemotherapy patients may experience elevated treatment-related mortality due to a poor stem cell reserve, subtle organ dysfunction, and increased co-morbid disease, which may sometimes overwhelm the effect of disease biology. This finding offers important context for the interpretation of genetic results. In AML, the most prominent and reproducible associations between specific
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gene mutations (FLT3, TP53, CEBPA, NPM1) and overall survival are related to the mutations’ differential impact on relapse risk.13 In fact, there are limited data available regard- ing the potential association between disease genetics and induction mortality. Notably, ten out of 13 patients with IDH1 mutations experienced early death during induction, while just two had refractory disease. This detail is central to the interpretation of the results and to contemplating clinical actionability. Do IDH1 mutations drive specific chemoresistance in older patients, thereby suggesting aug- mentation of induction with IDH1-directed therapy? Are IDH1 mutations causally or non-causally associated with clinical features that have been linked to increased trans- plant-related mortality?14 A combination of the two? In younger adults the prognostic impact of IDH mutations is unclear. One study suggested that those with both NPM1 and IDH mutations enjoyed a high event-free survival rate when treated with aggressive chemotherapy,15 while others showed a neutral or negative impact.16,17 The simplest expla- nation for the disparate literature regarding IDH1 mutations is that related to the random noise in small samples. Alternatively, the clinical impact of IDH mutations may be ‘context-dependent’, and different depending on its place in the clonal hierarchy (progression mutation in some cases and a founder or ‘early’ mutation in others), the co-occur- ring gene mutations, or undefined clinical characteristics. Does this group of patients in their 70’s and 80’s have IDH1 mutations that reflect a distinct group with particularly chemoresistant disease? If so, one could speculate that such individuals might have fared better with an IDH inhibitor than with chemotherapy. Indeed the single-agent studies with these drugs,18,19 mainly conducted in patients with advanced disease, include some previously untreated patients with comparable outcomes.
In summary, the German Austrian AML Study Group research is important because it confirms the commonality of secondary or stem cell type mutations in adults aged over 74 with AML. It further reminds us that prognostic charac- teristics cannot necessarily be applied with abandon across the age spectrum. However, we remain in the same conun- drum about the utility of aggressive versus less intensive therapy in this age group.
References
1. Klepin HD, Geiger AM, Tooze JA, et al. Geriatric assessment predicts survival for older adults receiving induction chemotherapy for acute myelogenous leukemia. Blood. 2013;121(21):4287-4294.
2. Leith CP, Kopecky KJ, Godwin J, et al. Acute myeloid leukemia in the
elderly: assessment of multidrug resistance (MDR1) and cytogenetics distinguishes biologic subgroups with remarkably distinct responses to standard chemotherapy. A Southwest Oncology Group study. Blood. 1997;89(9):3323-3329.
3. Lindsley RC, Mar BG, Mazzola E, et al. Acute myeloid leukemia ontogeny is defined by distinct somatic mutations. Blood. 2015;125(9):1367-1376.
4. Ferrara F, Barosi G, Venditti A, et al. Consensus-based definition of unfitness to intensive and non-intensive chemotherapy in acute myeloid leukemia: a project of SIE, SIES and GITMO group on a new tool for therapy decision making. Leukemia. 2013;27(5):997-999.
5. Juliusson G, Antunovic P, Derolf A, et al. Age and acute myeloid leukemia: real world data on decision to treat and outcomes from the Swedish Acute Leukemia Registry. Blood. 2009;113(18):4179-4187.
6. Ossenkoppele G, Lowenberg B. How I treat the older patient with acute myeloid leukemia. Blood. 2015;125(5):767-774.
7. Prassek VV, Rothenberg-Thurley M, Sauerland MC, et al. Genetics of acute myeloid leukemia in the elderly: mutation spectrum and clinical impact in intensively treated patients aged 75 years or older. Haematologica. 2018;103(11):1853-1861.
8. BuchnerT,BerdelWE,HaferlachC,etal.Long-termresultsinpatients with acute myeloid leukemia (AML): the influence of high-dose AraC, G-CSF priming, autologous transplantation, prolonged maintenance, age, history, cytogenetics, and mutation status. Data of the AMLCG 1999 trial. Blood. 2009;114(22):485.
9. DöhnerH,EsteyE,GrimwadeD,etal.Diagnosisandmanagementof AML in adults: 2017 ELN recommendations from an international expert panel. Blood. 2017;129(4):424-447.
10. GrimwadeD,HillsRK,MoormanAV,etal.Refinementofcytogenetic classification in acute myeloid leukemia: determination of prognostic significance of rare recurring chromosomal abnormalities among 5876 younger adult patients treated in the United Kingdom Medical Research Council trials. Blood. 2010;116(3):354-365.
11. PapaemmanuilE,GerstungM,BullingerL,etal.Genomicclassification and prognosis in acute myeloid leukemia. N Engl J Med. 2016;374(23):2209-2221.
12. Metzeler KH, Herold T, Rothenberg-Thurley M, et al. Spectrum and prognostic relevance of driver gene mutations in acute myeloid leukemia. Blood. 2016;128(5):686-698.
13. Marcucci G, Haferlach T, Döhner H. Molecular genetics of adult acute myeloid leukemia: prognostic and therapeutic implications. J Clin Oncol. 2011;29(5):475-486.
14. WalterRB,OthusM,BorthakurG,etal.Predictionofearlydeathafter induction therapy for newly diagnosed acute myeloid leukemia with pretreatment risk scores: a novel paradigm for treatment assignment. J Clin Oncol. 2011;29(33):4417-4423.
15. PatelJP,GönenM,FigueroaME,etal.Prognosticrelevanceofintegrat- ed genetic profiling in acute myeloid leukemia. N Engl J Med. 2012;366(12):1079-1089.
16. Green CL, Evans CM, Zhao L, et al. The prognostic significance of IDH2 mutations in AML depends on the location of the mutation. Blood. 2011;118(2):409-412.
17. Paschka P, Schlenk RF, Gaidzik VI, et al. IDH1 and IDH2 mutations are frequent genetic alterations in acute myeloid leukemia and confer adverse prognosis in cytogenetically normal acute myeloid leukemia with NPM1 mutation without FLT3 internal tandem duplication. J Clin Oncol. 2010;28(22):3636-3643.
18. SteinEM,DiNardoCD,PollyeaDA,etal.EnasidenibinmutantIDH2 relapsed or refractory acute myeloid leukemia. Blood. 2017;130(6):722- 731.
19. DiNardo CD, Stein EM, de Botton S, et al. Durable remissions with ivosidenib in IDH1-mutated relapsed or refractory AML. N Engl J Med. 2018;378(25):2386-2398.
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Ferrata Storti Foundation
Preclinical human models and emerging therapeutics for advanced systemic mastocytosis
Michel Arock,1,2 Ghaith Wedeh,1 Gregor Hoermann,3,4 Siham Bibi,1 Cem Akin,5 Barbara Peter,4,6 Karoline V. Gleixner,4,6 Karin Hartmann,7 Joseph H. Butterfield,8 Dean D. Metcalfe9 and Peter Valent4,6
1LBPA CNRS UMR8113, Ecole Normale Supérieure Paris-Saclay, Cachan, France; 2Laboratory of Hematology, Pitié-Salpêtrière Hospital, Paris, France; 3Department of Laboratory Medicine, Medical University of Vienna, Austria; 4Ludwig Boltzmann Cluster Oncology, Medical University of Vienna, Austria; 5Michigan Medicine Allergy Clinic, University of Michigan, Ann Arbor, MI, USA; 6Department of Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Austria; 7Department of Dermatology, University of Luebeck, Germany; 8Mayo Clinic, Division of Allergic Diseases, Rochester, MN, USA and 9Laboratory of Allergic Diseases, NIAID, NIH, Bethesda, MD, USA
ABSTRACT
Mastocytosis is a term used to denote a group of rare diseases characterized by an abnormal accumulation of neoplastic mast cells in various tissues and organs. In most patients with sys- temic mastocytosis, the neoplastic cells carry activating mutations in KIT. Progress in mastocytosis research has long been hindered by the lack of suitable in vitro models, such as permanent human mast cell lines. In fact, only a few human mast cell lines are available to date: HMC-1, LAD1/2, LUVA, ROSA and MCPV-1. The HMC-1 and LAD1/2 cell lines were derived from patients with mast cell leukemia. By contrast, the more recently established LUVA, ROSA and MCPV-1 cell lines were derived from CD34+ cells of non-mastocytosis donors. While some of these cell lines (LAD1/2, LUVA, ROSAKIT WT and MCPV-1) do not harbor KIT mutations, HMC-1 and ROSAKIT D816V cells exhibit activating KIT mutations found in mastocytosis and have thus been used to study dis- ease pathogenesis. In addition, these cell lines are increasingly employed to validate new therapeutic targets and to screen for effects of new tar- geted drugs. Recently, the ROSAKIT D816V subclone has been successfully used to generate a unique in vivo model of advanced mastocytosis by injection into immunocompromised mice. Such a model may allow in vivo validation of data obtained in vitro with targeted drugs directed against mastocytosis. In this review, we discuss the major characteristics of all available human mast cell lines, with particular emphasis on the use of HMC-1 and ROSAKIT D816V cells in preclinical therapeutic research in mastocytosis.
Introduction
Mast cells (MC) are tissue-fixed cells found in all vascularized organs. These cells are involved in a number of physiological processes, such as adaptive and innate immune responses.1 Moreover, MC play a central role in many pathological conditions, including allergic reactions and mastocytosis.2 MC develop from bone marrow CD34+/CD117+ progenitor cells,3 which enter the circulation and migrate into tissues, where they mature into MC in response to their major growth factor, stem cell factor (SCF), the ligand of KIT, also known as CD117. KIT is a transmem- brane receptor with intrinsic tyrosine kinase activity (Figure 1).4 Besides, mature tissue MC express the high affinity receptor for IgE (FcεRI) and can be activated through this receptor during allergic reactions.5
Correspondence:
arock@ens-cachan.fr
Received: May 4, 2018. Accepted: June 27, 2018. Pre-published: July 5, 2018.
doi:10.3324/haematol.2018.195867
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1760
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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Mastocytosis designates a group of rare disorders char- acterized by a pathological accumulation of MC in one or more organs.6 Clinical presentations of mastocytosis range from skin-limited disease (cutaneous mastocytosis) occurring mainly in childhood and often regressing spon- taneously, to systemic disease categories (systemic mas- tocytosis; SM), mostly seen in adults. SM variants usually involve the bone marrow and sometimes other internal organs, such as the spleen, liver, and/or gastrointestinal tract.
According to the World Health Organization (WHO), mastocytosis can be classified into three major categories: cutaneous mastocytosis, the most common variant, fol- lowed by SM, and MC sarcoma, a rare localized MC tumor (Online Supplementary Table S1).7 SM is subdivided into five distinct categories: indolent SM (ISM), smolder- ing SM (SSM), SM with an associated hematologic neo- plasm (SM-AHN), aggressive SM (ASM) and MC leukemia (MCL) (Online Supplementary Table S1).7 While patients with ISM have a normal or near-normal life expectancy, patients with SM-AHN, ASM or MCL, col- lectively termed advanced SM, share a poor prognosis.8 The diagnosis of SM is based on WHO criteria and is established when one major criterion and one minor cri- terion or at least three minor criteria are present (Online Supplementary Table S2).9 Once the diagnosis of SM has been established, patients are further graded according to the presence of B-findings reflecting a high MC burden, and of C-findings reflecting organ damage related to MC infiltration (Online Supplementary Table S3).10 The patho- physiology of mastocytosis is complex and if acquired activating mutations in KIT (mostly KIT D816V: NM_000222.2(KIT):c.2447A>T, p.Asp816Val) seem to be major drivers of disease in ISM, the same cannot be said for advanced SM in which, in addition to KIT mutants, KIT-independent signaling pathways are activated and additional genetic defects are frequently found.
Given the complex pathophysiology of mastocytosis, in
vitro models mimicking neoplastic MC found in SM
patients could be useful for developing new therapeutic
approaches. To date only a few human MC lines have
been described, namely HMC-111 and its subclones
(HMC-1.1 and HMC-1.2),12 LAD (subclones 1 through
5),13 LUVA,14 ROSAKIT WT and its subclone ROSAKIT D816V,15
Pathophysiology of mastocytosis
The pathophysiology of mastocytosis is governed by the presence of KIT activating mutations in neoplastic MC.18 Indeed, various KIT activating mutations have been described, initially in patients with SM,19 then in children with cutaneous mastocytosis.20 In adult SM patients, KIT mutations affect primarily exon 17 encoding for the phos- photransferase domain, usually D816V (>80% of all
exons 13 and 14 encoding for kinase domain 1.21 By con- trast, in children, KIT mutations are found in nearly 75% of biopsies of skin lesions, but the KIT D816V mutation is found in only 30% of all cases.20 Indeed, a significant percentage of children present with KIT mutants located in the extracellular domain (codons 8 and 9) (Figure 1).20
In KIT D816V+ SM patients, the development of neo- plastic MC is principally governed by the PI3K/AKT and JAK/STAT5 signaling pathways activated downstream of KIT.22,23 Indeed, AKT and STAT5 are constitutively acti-
Figure 1. Normal structure of the KIT receptor and KIT mutations described in human mast cell leukemia-like cell lines and in patients with mastocytosis. In humans, KIT, located on chromosome 4q12, contains 21 exons transcribed/translated into a transmembrane receptor with tyrosine kinase activity (145 kDa and 976 amino acids). KIT is presented in its monomeric form, but dimerizes as a result of stem cell factor (SCF) ligation. The extracellular domain, in yellow, comprises five immunoglobulin (Ig)-like subunits where the lig- and binding site (SCF for KIT) and the dimerization site are located. The cytoplas- mic region contains a transmembrane domain (TMD) made by a single helix, in blue. The intracellular portion of KIT, in gray, contains an auto-inhibitory jux- tamembrane domain (JMD) and a kinase domain (in dark gray) which is split into two parts: an ATP-binding domain (ABD) and a phosphotransferase domain (PTD) linked by a large kinase insert (KI) domain of ~ 60–100 residues. For the sake of clarity and readability, only the most frequent mutations found in patients and/or in human MC lines are represented. In red, mutants found in adult patients and in cell lines (KIT D816V found in >80% of adult patients with sys- temic mastocytosis and 30% of children with cutaneous mastocytosis, as well as in HMC-1.2 and ROSAKIT D816V MCL-like cell lines, and KIT V560G found in the MCL- like cell lines HMC-1.1 and HMC-1.2, but only in a very few adult patients). In black, three of the KIT defects most frequently found in pediatric patients: KIT Del419 (NM_000222.2(KIT):c.1255_1257del, p.Asp419del), KIT ITD501-502 (NM_000222.2(KIT):c.1500_1505dup, p.Ser501_Ala502dup) and KIT ITD502- 503 (NM_000222.2(KIT):c.1503_1508dup, p.Ala502_Tyr503dup) and in brown, the KIT K509I mutant found in several familial cases of the disease. For a complete overview of the various KIT mutations found in pediatric and adult mastocytosis patients, see Valent et al.7 Del, deletion; ITD, internal tandem dupli- cation.
and MCPV-1.1 through MCPV-1.4.16 While LAD, LUVA KIT WT
and ROSA cells express KIT wild-type (WT), HMC- 1.1, HMC-1.2 and ROSAKIT D816V cells harbor KIT activating mutations,15,17 and MCPV-1 are RAS-mutated cells.16 Although these molecular aberrancies do not recapitulate all the characteristics of neoplastic MC found in advanced SM, these last four cell lines are currently the best avail- able models for identifying molecular targets and defining the effects of several interventional (targeted) drugs cur- rently used to treat advanced SM.
21
exons 2, 8 and 9 encoding for the extracellular domain or
patients) (Figure 1).
Other less frequent mutations affect
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vated in neoplastic MC in such patients and in KIT- mutated MCL-like cell lines, and inhibition of these path- ways induces growth arrest in such cells.22,24 Other intra- cellular pathways and molecules, such as the Feline sarco- ma oncoprotein,25 or the mechanistic target of rapamycin (mTOR) complex,26 are also potential triggers of oncogen- esis. In addition, the KIT mutant activates ERK independ- ently of SRC, in contrast to KIT WT.27 Finally, LYN and BTK are found activated in neoplastic MC in a KIT-inde- pendent manner.28
Because KIT-activating mutations are found in most SM patients, several KIT-targeted tyrosine kinase inhibitors (KIT-TKI) have been developed. However, the nature of the mutation influences the sensitivity of the mutant to these TKI. For instance, the KIT D816V mutant is insensi- tive to imatinib.29 By contrast, patients presenting with KIT WT, or KIT mutant outside exon 17, may potentially respond to imatinib.30 While in ISM the KIT D816V mutant seems to be the unique molecular abnormality found, addi- tional and recurrent somatic mutations of myeloid malig- nancy-related genes have been reported in advanced SM. The genes most frequently affected are TET2, SRSF2, ASXL1, RUNX1, JAK2, N/KRAS and CBL,31-35 while EZH2, IDH2, ETV6, U2AF or SF3B1 are less often affected.36 All these mutations may be co-expressed with KIT D816V in the same cells or may be expressed in other myeloid cells but not in MC, especially in (A)SM-AHN with TET2, SRSF2 and ASXL1 mutants, in which acquisition of KIT D816V is often a late event conferring a mastocytosis phe- notype on a pre-existing clonal condition.37 These defects, and particularly the SRSF2, ASXL1 and RUNX1 (S/A/R) mutations, have a negative impact on the disease progno- sis.31-34,35 Thus, targets other than KIT and drug combina- tions might be considered in order to develop more effec- tive therapies for advanced SM. The potential of new tar- gets and of new targeted drugs or drug combinations is cur- rently investigated using the available human MCL-like MC lines, which will be described hereafter.
Major characteristics of available human mast cell leukemia-like mast cell lines
It is beyond the scope of this review to develop all the applications of the available human MC lines. We will only provide a detailed description of the cell lines that qualify as MCL-like, namely HMC-1, ROSA and MCPV- 1. Indeed, these cell models have been and are still used in vitro and/or in vivo to evaluate the potential effects of drugs and drug combinations to treat mastocytosis. Table 1 shows a summary of the major characteristics of all available human MC lines, while Tables 2 and 3 provide detailed phenotypic information.
The HMC-1 cell line and subclones (HMC-1.1 and HMC-1.2)
The origin, major characteristics and phenotype of HMC-1 cells are presented in Tables 1 through 4. HMC-1 cells are metachromatic cells containing histamine and tryptase.11 The original cell line presented with a complex karyotype (Table 1), which might have potentially played a role in the cells’ immortalization. However, despite this fact, HMC-1 cells remained sensitive to KIT inhibitors, in favor of a critical role of the KIT mutants in their mainte- nance. Indeed, in HMC-1 cells, KIT is constitutively phos- phorylated on tyrosine residues in the absence of SCF.17 Sequencing of the coding region of KIT cDNA revealed that KIT in HMC-1 cells is composed of a normal WT
allele and a mutant allele with two point mutations, KIT V560G (NM_000222.2(KIT):c.1679T>G, p.Val560Gly) and KIT D816V.38
Seven years later, two HMC-1 subclones, namely HMC-1.1 and HMC-1.2, were described.12 Both sub- clones have a heterozygous KIT V560G mutation,12 but only HMC-1.2 cells display the KIT D816V mutation.12 In both subclones, KIT was found constitutively phosphory- lated in the absence of SCF, although the presence of the KIT D816V mutation seemed to confer a slight growth advantage to HMC-1.2 cells over HMC-1.1 cells.12
HMC-1 cells have been extensively used to study KIT mutant-related and KIT mutant-independent signaling pathways and to evaluate anti-neoplastic effects of cytore- ductive/targeted drugs developed to treat advanced SM.
The ROSAKIT WT and ROSAKIT D816V subclones
The SCF-dependent ROSAKIT WT cell line was established from a CD34+ fraction of normal umbilical cord blood cells.15 CD34+ cord blood cells were cultured in the pres- ence of human SCF and, after an 8-week culture period, cells continued to proliferate, with virtually all cells being MC. The doubling time was relatively short (48-72 h) in the presence of SCF.15 ROSAKIT WT cells are round cells with a relatively high nuclear-to-cytoplasm ratio and metachromatic cytoplasmic granules.15 ROSAKIT WT cells stain strongly positive for tryptase and KIT, but express only little if any chymase.15
KIT WT
ROSA cells were found to express FcεRI, KIT
(CD117), CD33, CD4, CD9, CD203c, and CD300a, con- sistent with a MC phenotype, while they did not express CD2 or CD25 (Tables 2 and 3).15 Moreover, similar to pri- mary cord blood-derived MC, incubation of ROSA cells with interleukin-4 and IgE for 4-5 days enhanced surface expression of FcεRI. In addition, ROSA cells sensitized with interleukin-4 and IgE were fully activated by anti- IgE.15 However, over long periods of continuous culture, expression of FcεRI tends to fade on the cells, which become less sensitive to FcεRI cross-linking (unpublished observation).
ROSAKIT WT cells have a normal KIT structure, but harbor a complex karyotype, with a derivative chromosome 1 [der(1)inv(1)(p31q21)del(1)(q24q32)]. In fact, the cell line consists of two subclones: one minor subclone carrying a complete trisomy 5, and the other predominant subclone carrying a partial trisomy 5 [+del(5)(q14q34)].15 In addi- tion, molecular studies revealed that both ROSAKIT WT sub- clones have a P53 deletion and a hot spot K700E mutation in SF3B1 (unpublished observation). We assume that these alterations contributed to the immortalization of ROSAKIT WT cells and provide a premalignant (permissive) cellular background sufficient to trigger proliferation when a driv- er, such as KIT D816V, is introduced.
Indeed, when ROSAKIT WT cells were further transfected with a lentivirus encoding for GFP + KIT D816V, the resulting subclone proliferated independently of SCF. This subclone, termed ROSAKIT D816V, has the same dou- bling time as ROSAKIT WT cells cultured in SCF.15 Similar to their parental cells, ROSAKIT D816V cells have a rather mature morphology with numerous cytoplasmic granules.15
ROSAKIT D816V cells exhibit the same complex karyotype and the same SF3B1 K700E mutation as ROSAKIT WT cells.15 Moreover, the phenotype of ROSAKIT D816V cells is similar to that of the parental cell line, including expression of the FcεRI and negativity for CD2 and CD25 (detailed in
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2011
2014
PB of a patient with allergic disease
Normal CB-derived CD34+ cells
Short (48-72 h)
Short (48-72 h)
KIT WT
KIT WT
No
Yes
Yes
Preclinical models of mastocytosis
Tables 1-4), although, in contrast to ROSAKIT WT cells, repeated attempts to activate ROSAKIT D816V cells by cross- linking FcεRI failed in our hands.15 Interestingly, KIT (CD117) is expressed at higher levels in ROSAKIT D816V cells than in ROSAKIT WTcells.15 While KIT phosphorylation in ROSAKIT WT cells needs the presence of SCF, KIT is consti- tutively phosphorylated in ROSAKIT D816V cells.15 In addi- tion, STAT5 and AKT are constitutively phosphorylated in ROSAKIT D816V cells, as in primary neoplastic MC.22,24,39 Interestingly, inhibition of AKT or STAT5 decreases ROSAKIT D816V cell proliferation.15 As expected, ROSAKIT WT cells responded to imatinib, while ROSAKIT D816V cells were resistant to imatinib, but sensitive to dasatinib or midostaurin (PKC412),15 making these couple of cell lines a convenient tool for determining the relative selectivity of TKI towards the two forms of KIT (WT versus D816V).
Table 1. Major characteristics of the available human mast cell lines.
Of note, ROSAKIT D816V cells were reported to engraft NOD/SCID IL-2Rγ−/− (NSG) mice efficiently, giving rise to an ASM/MCL-like disease in vivo,15 described later in this manuscript. Thus, the ROSAKIT D816V cell line is a unique model of human KIT D816V+ ASM/MCL useful for in vitro and in vivo studies.
Finally, ROSA cells also appear well suited to investi- gating the transforming potential of KIT mutants found in other categories of mastocytosis. For example, starting from ROSAKIT WT, we created ROSA subclones stably expressing the mutant KIT Del417-419insY (NM_000222.2(KIT):c.1249_1255delinsT, p.Thr417_Asp419delinsTyr), or the mutant KIT K509I (NM_000222.2(KIT):c.1526A>T, p.Lys509Ile), both found in pediatric patients.20 In each case, the cells became SCF-independent, and KIT was found constitu-
Cell line
HMC-1
Subclones HMC-1.1 HMC-1.2
Date of first description
1988
Origin
PB of a patient with MCL
Doubling time
Short (48-72 h)
KIT
status
SCF- dependence
FcεRI expression
Authentication by DNA fingerprinting
Karyotype
Presence of non-KIT somatic mutation(s)
u.k.
KIT V560G
and (46<2n>XX,
KIT D816V
ins(10;16) (q25;q22q12), add(13)(q33))
No
No
No
No
Complex
LAD subclones (1-5)*
LUVA
2003
2003
BM cells of a patient with KIT D816G+ MCL
Long (2 weeks)
KIT V560G
KIT V560G and KIT D816V
KIT WT
Yes
Yes
Yes
Complex (41-72,XXY, -[7],+2[11], +4[2],+5[6],+7[2], +16[3], +18[2], -21[14] cp15)§
u.k.
u.k.
u.k.
MCPV-1 subclones (1.1-1.4)
BM: bone marrow; CB: cord blood; MC: mast cell; MCL: mast cell leukemia; PB: peripheral blood; SCF: stem cell factor; u.k.: unknown. *Only the LAD2 subclone has been widely distributed since its description. §Karyotype of the LAD2 subclone.
SF3B1 K700E
ROSAKIT D816V
2014
ROSAKITWT cells transduced with a KIT D816V construct
Normal CB-derived MC progenitors transduced with HRAS G12V
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Short (48-72 h)
KIT D816V
KIT WT
No
No
Yes
No
No
No
Complex (see description in the text)
u.k.
HRAS G12V
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Table 2. Expression of activation-induced antigens, cytokine receptors and molecular targets† by the human mastocytosis-like mast cell lines.
CD Name HMC-1 ROSAKIT D816V MCPV-1.1
Table 3. Expression of lineage-related markers and adhesion mole- cules† by the human mastocytosis-like mast cell lines.
CD16 FcγRIII _ _ _ CD2 LFA2 +
n.t. _
_ _
+ _ n.t. _ + _ + _ + _ n.t. _ + _ n.t. _ n.t. _ _ _ _ _ _ _ n.t. + _ _ + _ + + + + + + + _ n.t. + + _ _ + _ _ _ _ _ _ _ _ _ _ _ _ _ + _ _
FcεRII _ DPP4 _ TNFRSF7 _ FcγRII + MIRL + LAMP-3 + FcγRI _ BGP-1 +
_ _
CD3
CD4
CD5
CD8
CD9
CD10
CD14
CD15
CD17
CD19
CD20
CD22
CD24
CD31
CD38
CD45
CD48
CD50
CD54
CD56
CD58
CD90
CD96
CD133
CD134
CD144
CD146
CD150
CD153
CD166
CD326
TCR _ T4 _ T1_ T8 _
MRP-1 +
CALLA _
LPSR _
LeX _
LacCer _
B4 _
B1 _
SIGLEC-2 _
BA-1 +
PECAM-1 +
T10 _
LCA +
BLAST1 +
ICAM-3 +
ICAM-1 +
NCAM _
LFA-3 +
THY1 _
TACTILE _
AC133 _
OX-40 _
VE-CADHERIN _
MUC18 _
SLAM _
CD30L _
ALCAM +
EPCAM _
CD23
CD26
CD27
CD32
CD59
CD63
CD64
CD66a
CD69
CD71 TfR1 + CD95 FAS +
n.t. n.t. + n.t. + +/- + + + _ _ _ _ _ _ n.t. n.t.
_ _ + + + _ _ + + + _ +/- _ _ _ + +/-
CD Name HMC-1
ROSAKIT D816V
MCPV-1.1
AIM +/-
CD105
CD114
CD115
CD116
CD127
CD129
CD135
CD138
CD164
CD184
CD203c
CD213a1
CD218a
CD243
CD304
CD309 VEGFR2 _
ENDOGLIN _ G-CSFR _ M-CSFR _
GM-CSFRa _ IL-7R _ IL-9R _ FLT3 _
SYND1 _ MGC-24 +
_ _ +/- + n.t. _
+ + _ _ _ _
n.t. _
n.t. +
_ _
CXCR4 +/-
ENPP3 _ IL-13Ra1 _ IL-18Ra _ MDR-1 _ NRP1 _
†some of the related antigens are also listed in Table 4. n.t.: not tested; +: strong expres- sion; +/-: weak expression; -: no expression.
tively phosphorylated. In addition, both subclones remained, as expected, sensitive to the growth inhibitory effects of imatinib (unpublished observations). These addi- tional data demonstrate that ROSA cells are reasonable tools for investigating the oncogenic potential of newly discovered KIT mutants as well as for screening for their sensitivity to TKI.
The MCPV-1 subclones
The human MCPV-1 subclones (MCPV-1.1 through - 1.4) were generated from cord blood-derived CD34+ pro- genitors by culturing these cells with SCF and interleukin- 6 for 8 weeks and then stably transducing HRAS G12V, SV40 TAg and TERT.16 Single-cell clones were then isolat- ed and cultured for more than 2 years to demonstrate immortalization. Light microscopy of Wright-Giemsa- stained MCPV-1.1 cells reveals large, immature cells with bi-, tri-, or multi-lobed (often cloverleaf-like-shaped) nuclei characteristic of MC precursors.16 MCPV-1 cells contain a basophilic cytoplasm, cytoplasmic protrusions and sparse granulation. Moreover, MCPV-1.1 cells exhibit an immunophenotype consistent with MC progenitors (Tables 2 and 3).16 MCPV-1 cells express tryptase but lack
†some of the related antigens are also listed in Table 4. n.t.: not tested; +: strong expres- sion; +/-: weak expression; -: no expression.
surface FcεRI.16 MCPV-1 cells grow independently of SCF and produce a MCL-like disease in NSG mice.
Human mast cell leukemia-like cell lines as models for in vitro testing of growth-inhibiting drugs
Treatment of ISM mainly aims at symptomatic relief of MC mediator symptoms.40 By contrast, treatment of advanced SM is challenging and relies principally on non- targeted and/or targeted cytoreductive therapy.41 In unusual cases (rare KIT-mutant forms or WT KIT) the dis- ease may respond to imatinib or masitinib.30,42,43 In a sub- group of patients with slowly progressing ASM, low-dose prednisolone and interferon-a may be efficacious.44 In addition, low-dose methylprednisolone and cyclosporine A may show some (usually minor) effects in ASM patients.45 Cladribine (2CdA) is often recommended as first-line therapy in patients with advanced SM with multi-organ involvement and slow progression.46,47 A
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forthcoming new standard of therapy in advanced SM is midostaurin (PKC412).48,49 This drug was approved for treatment of advanced SM by the American Food and Drug Administration and the European Medicines Agency in 2017. For ASM/MCL patients with rapid pro- gression and those resistant to 2CdA or midostaurin, poly-chemotherapy is usually recommended, followed, when possible, by allogeneic hematopoietic stem cell transplantation.50 Almost all drug-based cytoreductive therapies have been validated preclinically in vitro using MCL-like MC lines. The most widely used cells for this purpose have been (and still remain) the two HMC-1 sub- clones. However, the newly emerging MCL-like human MC lines, ROSA and MCPV-1, have also been used repeatedly in such drug-testing studies. A summary of drug-testing approaches and of results obtained with these cell lines is provided in the following paragraphs.
HMC-1 cell lines and their responses to targeted and non-targeted cytoreductive drugs
Numerous antineoplastic drugs have been tested for their effects on HMC-1 cells.51 Among conventional anti- neoplastic drugs, doxorubicin and cytosine arabinoside were the most active agents.51 Other effective agents were vinblastine, etoposide and mitomycin.51 The potent effects of these chemotherapy-type drugs, otherwise used to treat acute myeloid leukemia, formed the basis to suggest treatment of patients with rapidly progressing ASM and MCL as well as patients with SM-acute myeloid leukemia with standard induction chemothera- py, often as preparation for allogeneic stem cell transplan- tation.
The effects of interferon(s) on the growth of HMC-1 cells have also been analyzed.52 HMC-1 cell numbers decreased in the presence of interferon-γ but were unaf- fected by interferon-a,52 contrasting with the activity of interferon-a in a subset of patients with advanced SM.44 This example highlights the fact that not all drug effects observed in vitro can be translated into clinical practice and that in each case, drugs and drug combinations need to be tested in additional disease models and finally in interventional clinical trials.
Studies of the in vitro anti-proliferative activity of 2CdA on HMC-1 cells were published after this drug was used in vivo to treat patients with advanced SM. Indeed, the first reports on the in vivo effects of 2CdA in patients were published between 2001 and 2004,53-55 but it was not until 2006 that the in vitro effects of 2CdA on HMC-1 cells were described.56 While 2CdA alone produced growth- inhibitory effects on HMC-1 cells, the drug was also found to cooperate with midostaurin.56 The observation that midostaurin can induce apoptosis and growth inhibi- tion in HMC-1 cells and that efficacy was identical in HMC-1.1 and HMC-1.2 cells prompted further investiga- tions and led to the initiation of clinical trials.48,49
Human mast cell leukemia-like cell lines as models of drug resistance
Because most patients with SM harbor an activating point mutation in KIT (mostly KIT D816V) which is asso- ciated with disease pathology, considerable efforts have been made to identify drugs capable of inhibiting the kinase activity of the KIT mutant. The effects of imatinib, a drug targeting KIT WT, on cell lines harboring various KIT mutations, were investigated soon after the drug was
Table 4. Expression by the human mastocytosis-like mast cell lines of antigens aberrantly expressed or overexpressed on malignant mast cells and/or their neoplastic progenitors in patients with systemic mastocytosis.
CD Name HMC-1
ROSAKIT D816V
MCPV-1
CD13 APN +
+ +
- - - - + + - - + + + + + + + + +/- -
CD25
CD30
CD33
CD34
CD44
CD52
CD87
CD117
IL-2Ra - KI-1 - SIGLEC-3 + HPCA-1 -
PGP-1 + CAMPATH-1 +/-
UPAR +
KIT +
IL-3Ra -
+: strong expression; +/-: weak expression; -: no expression.
CD123
found to block growth of leukemic cells in Philadelphia chromosome-positive chronic myeloid leukemia. In 2000, Ma et al. reported that imatinib inhibited KIT WT at low concentrations, without significant effects on the KIT D816V mutant.57 In 2003, these findings were confirmed using HMC-1.2 cells and patient-derived KIT D816V+ MC.29,58 More recently, it was also confirmed that ROSAKIT D816V cells are insensitive to imatinib.15 Masitinib, another TKI active on KIT WT, although devoid of activity on KIT D816V in vitro,59 was administered in a randomized, dou- ble-blind, placebo-controlled, phase 3 study in a cohort of severely symptomatic ISM or SSM patients resistant to classical anti-mediator therapy.60 Interestingly, masitinib improved mediator-related symptoms in a subset of patients as compared to placebo-treated patients, regard- less of KIT mutational status.60 This clinical activity was linked to the in vitro inhibitory effects of masitinib on two molecules involved in MC activation, namely LYN and FYN.59
Given the inefficacy of imatinib on the KIT D816V mutant, several other TKI have been evaluated in vitro (and for a few of them in vivo) for their potential activity in the SM context. Dasatinib is a multikinase inhibitor highly active on BCR-ABL1, KIT and PDGFRa.61,62 The potential activity of this drug against KIT D816V was investigated in vitro in HMC-1 cells, SM patient-derived KIT D816V+ cells and ROSA cells.15,63 In each instance, dasatinib exerted in vitro cytotoxic effects at relatively low half maximal inhibitory concentrations (IC50), although the IC50 for dasatinib was higher in KIT D816V+ cells than in KIT D816V– cells.15,63 However, when evaluated in vivo in clinical trials or in individual SM patients, dasatinib unexpectedly demonstrated only marginal activity.64-66 While the in vivo effects of dasatinib have been disap- pointing, midostaurin, a potent multikinase inhibitor, has proven to be highly promising. Indeed, midostaurin decreased the proliferation of KIT D816V+ cell lines at pharmacological concentrations.15,56,63,67 In addition, the drug abrogated KIT phosphorylation in MCL-like cell lines harboring KIT D816V and induced their apopto- sis.15,56,68 Moreover, midostaurin suppressed the growth of primary human KIT D816V+ neoplastic MC.68 Finally, midostaurin was found to block IgE-dependent histamine release from MC and basophils.67,69,70 Based on these data,
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clinical trials have been conducted to determine the effi- cacy of midostaurin in patients with advanced SM, with promising results.48,49,71 An overview of the effects of midostaurin and of several other TKI on the growth of HMC-1 and ROSA cells is presented in Figure 2 and Online Supplementary Table S4.
Several other TKI with different mechanisms of action were also found to exert antineoplastic effects in vitro on KIT D816V+ neoplastic MC, including HMC-1 cells. These drugs include 17-AAG (17-allylamino-17- demethoxygeldanamycin),72 EXEL-0862 (a TKI active against fibroblast growth factor receptors, vascular endothelial growth factor receptors, platelet-derived growth factor receptors, FLT3 and KIT),73 triptolide (a diterpenoid),74 ponatinib (a multi-kinase blocker),68 and bosutinib (a LYN/BTK-inhibiting TKI),28 which was administered to a patient with advanced SM, with no benefit.75 Nilotinib, which showed some effects in vitro on mutant KIT,76 was recently administered to 61 SM patients, with transient activity in some patients.77
More recently, several new KIT-TKI with inhibitory activity in vitro on several KIT mutants, including KIT D816V, have been developed. DCC-2618 (Deciphera Inc.) is a switch control type II KIT inhibitor, which arrests KIT in an inactive state, regardless of activating mutations, such as KIT D816V.78 In a recent study, it was found that DCC-2618 inhibits proliferation and survival of HMC- 1.1, HMC-1.2 and ROSAKIT D816V cells at IC50 <1 mM.79 BLU- 285 is a TKI developed by Blueprint Medicines. At low concentrations, BLU-285 selectively inhibited KIT D816V enzymatic activity (IC50 = 0.27 nM).80 The cellular activity of BLU-285 on this mutant was also measured by autophosphorylation in HMC-1.2 cells with an IC50 of 4.0 nM.80 Finally, BLU-285 inhibited in vitro the proliferation
of KIT D816V+ HMC-1.2 cells with an IC50 of 125 nM, while being less active on KIT D816V– HMC-1.1 cells (IC50 = 344 nM).81
Human mastocytosis-like mast cell lines and drugs targeting KIT- dependent or KIT-independent signaling pathways
Since KIT D816V is equally present in ISM and advanced SM patients, who have different life expectan- cies,82 the current assumption is that additional, KIT-inde- pendent pathways and pro-oncogenic hits and lesions are responsible for disease progression in advanced SM. Such pathways and pro-oncogenic molecules include LYN, BTK, STAT5, PI3-K, mTOR and members of the BCL-2 family.
For instance, LYN and BTK are phosphorylated in HMC-1.1 and HMC-1.2 subclones independently of KIT, and short interfering RNA against LYN and BTK decreased the survival of both subclones.28 In the same set of experiments, dasatinib blocked not only the kinase activity of KIT, but also LYN and BTK activation in neo- plastic MC, while bosutinib inhibited LYN and BTK acti- vation without decreasing KIT kinase activity.28
Another molecule, STAT5, seems critical for KIT D816V-driven proliferation in MCL-like MC lines as well as in neoplastic MC in SM patients.24,83 Chaix et al. report- ed that the KIT D816V mutant can directly phosphorylate STAT5 in vitro.83 Interestingly, STAT5 is transcriptionally active in the HMC-1 cell line and in ROSAKIT D816V cells,15,24 and drugs targeting STAT5 are effective in decreasing the growth rate of these cells.84,85 Figure 3 shows representa- tive curves of dose-dependent inhibition of the viability of MC lines by STAT5 inhibitors.
Gabillot-Carre et al. reported constitutive activation of the mTOR signaling pathway in both HMC-1 sub-
Figure 2. Dose-dependent inhibition of the proliferation of wild-type and mutant KIT human mast cell lines by various tyrosine kinase inhibitors in vitro. Human mast cell lines expressing KIT D816V (HMC-1.2 or ROSAKIT D816V; black lines) or lacking KIT D816V (HMC-1.1 or ROSAKIT WT; gray lines) were incubated in control medium (Co) or in medium containing various concentrations of tyrosine kinase inhibitors (as indicated) at 37°C for 48 h. Thereafter, 3H-thymidine uptake was measured. Results are expressed as percent of 3H-thymidine uptake compared to the control and represent the mean ± standard deviation of three different experiments.
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clones.86 However, the mTOR inhibitor rapamycin induced apoptosis only in HMC-1.2 cells.86 To support this unexpected selectivity, the authors demonstrated that rapamycin inhibited the phosphorylation of 4E-BP1, a downstream substrate of the mTOR pathway, only in HMC-1.2 cells.86 More recently, it was reported that the dual PI3-kinase/mTOR blocker NVP-BEZ235 has similar growth inhibitory effects in HMC-1.1 and HMC-1.2 cells.87 However, despite these encouraging data, no objective response was observed in a study in which everolimus, an oral mTOR inhibitor, was given at a dose of 10 mg daily to ten SM patients.88
Finally, aberrant accumulation of neoplastic MC in SM might result from deregulation of apoptosis pathways.89 Indeed, the anti-apoptotic molecules BCL-2, BCL-xL and MCL-1 are overexpressed in KIT D816V+ neoplastic MC in SM patients,90-92 while the expression of the pro-apop- totic molecule BIM is suppressed in these cells.93 It has also been reported that MCL-1 is detectable in HMC-1.1 and HMC-1.2 cells.93 Moreover, exposure of these cells to MCL-1-specific antisense oligonucleotides or to MCL-1- specific short interfering RNA resulted in reduced cell sur- vival and increased apoptosis.93 In further studies, evi- dence was provided that the pan-BCL-2 family blocker obatoclax inhibited the proliferation of HMC-1 cells, together with increased expression of PUMA, NOXA, and BIM mRNA, and apoptosis.94
Human mastocytosis-like mast cell lines and drugs targeting surface antigens or epigenetic regulators
Although drugs targeting KIT D816V have demonstrat- ed activity on MC in vitro and in vivo, these agents do not cure patients with advanced SM.48,49,71 Apart from several different mechanisms of resistance, neoplastic cells in these patients may exhibit a complex pattern of genetic alterations together with, or even often preceding the appearance of, the KIT mutant, as it is the case for TET2, SRSF2 and ASXL1 mutants,37 which could explain resist- ance to TKI. For this reason, attention has been focused recently on alternative targets which could help to over- come such resistance, namely surface antigens specifical- ly or aberrantly expressed by neoplastic MC and epige-
netic targets. Antibodies or drugs directed against these targets may also be able to overcome intrinsic neoplastic stem cell resistance, often associated with quiescence and altered drug influx or rapid drug efflux. Antibody-based drugs may exert antineoplastic effects independently of such mechanisms of resistance.
Targeting surface antigens
Several antigens are aberrantly expressed or overex- pressed on neoplastic MC and on their progenitors in SM, including CD13, CD25, CD30, CD33, CD44, CD52, CD117 and CD123,95-97 and might, therefore, be consid- ered as potential therapeutic targets. Table 4 provides an overview of cell surface targets expressed on human MCL-like cell lines.
CD30 is aberrantly expressed by neoplastic MC in a subset of patients with SM, but not by normal/reactive MC.98 In a recent study, it was observed that the MCPV- 1.1 subclone expressed high levels of CD30, while HMC- 1.1 cells expressed low CD30 levels, and HMC-1.2 cells did not express CD30.99 The CD30-targeting antibody- conjugate brentuximab-vedotin inhibited the in vitro pro- liferation of neoplastic MC, with lower IC50 values obtained for MCPV-1.1 cells (10 mg/mL) than for HMC- 1.2 cells (>50 mg/mL).99 In addition, brentuximab-vedotin produced apoptosis in primary CD30+ neoplastic MC.99 However, overall, the effects of brentuximab-vedotin on neoplastic MC are relatively weak. Correspondingly, no major clinical activity has been reported in clinical trials to date. In addition, neoplastic stem cells in advanced SM usually lack CD30 (personal information, PV).
In contrast to normal MC and MC from ISM patients, CD52 is abundantly expressed on neoplastic MC in most patients with advanced SM.16 Recently, it was reported that the CD52-targeting antibody alemtuzumab counter- acts growth of MCPV-1.1 cells.16 Additionally, MCPV-1.1 cells were injected into NSG mice which were then treat- ed with alemtuzumab or control vehicle. The alem- tuzumab-treated mice had increased survival compared to controls, and reduced organ infiltration by neoplastic MC.16 Given that neoplastic (leukemic) stem cells identi- fied in advanced SM may also express CD52,100 it can be
Figure 3. Dose-dependent inhibition of the proliferation of KIT D816V+ human mast cell lines by STAT5 inhibitors in vitro. ROSAKIT D816V and HMC-1.2 cells were cultured in 96-well plates for 72 h in control medium containing 0.1% dimethylsulfoxide (DMSO) or with increasing con- centrations (between 1.0 and 50.0 mM) of SF-1066, a very weak STA5 inhibitor (Ki >25 mM on STAT5), and of more specific and potent STAT5 inhibitors BP-1-102 and BP-1-108 (Ki >10 mM on STAT5).74 Viability was calculated in each condition by the MTT method. Results are expressed as percent of control and represent the mean ± standard deviation of triplicate experiments. The half maximal inhibitory concentration (IC50) at day 3 of each compound for each cell line was calculated using Prism GraphPad 4.0 software after plotting log concentration versus response. As expected, while the IC50 for SF-1066 was >50 mM, IC50 values for the more STAT5-specific com- pounds were lower: 11 mM for BP-1-102 on both KIT D816V+ neoplastic human MC lines and 34 and 22 mM for BP-1-108 for, respectively, HMC-1.2 and ROSAKIT D816V cells. Although these values are still irrelevant at the pharmacological level, they open hopes that drug opti- mization might lead in a near future to the design of more potent small molecules inhibiting STAT5 activity.
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AB
CD
Figure 4. Engraftment of ROSAKIT D816V-Gluc cells in NSG mice. Increasing numbers of ROSAKIT D816V-Gluc cells (1x106, 5x106 or 10x106) were injected into the tail vein of NOD-SCID IL-2Rγ- /- (NSG) mice (3 groups; 6 mice per group) 24 h after irradiation at 2.5 Gy from a cesium-137 source.113 After 10 weeks, engraftment was assessed using (A) quanti- tative measurements of Gluc activity in plas- ma and (B) in vivo bioluminescence imaging (IVIS) on engrafted mice. Ten weeks after engraftment, mice were sacrificed and (C) bone marrow and (D) spleen sections from the three groups of mice were stained by immunohistochemistry with an anti-human tryptase antibody. Staining was visualized by a Histomouse Kit, showing human MC with a brownish stain, which massively invaded the bone marrow and to a lesser extent the spleen. (C) and (D) are from one representative mouse from the group inject- ed with 10x106 ROSAKIT D816V-Gluc cells. Original magnification, x100.
hypothesized that a combination of a KIT-TKI and a monoclonal antibody against CD52 might help to achieve major antineoplastic effects in advanced SM.
Another potential surface target is CD33. In fact, CD33 is invariably expressed on neoplastic MC and their stem cells in patients with advanced SM.95 In addition, it has been described that the CD33-targeted antibody-con- struct gemtuzumab-ozogamicin is able to suppress growth and survival of neoplastic MC.101 In the light of the revival of gemtuzumab-ozogamicin, its clinical effica- cy in patients with acute myeloid leukemia and its effects on neoplastic MC,102 it might be reasonable to propose clinical trials testing the effects of gemtuzumab-ozogam- icin alone or in combination with other antineoplastic drugs or stem cell transplantation in advanced SM.
Targeting epigenetic regulators
The epigenetic reader bromodomain-containing 4 pro- tein (BRD4), a member of the BET family proteins, has recently been identified as a promising target in acute myeloid leukemia.103,104 In addition, highly selective BET bromodomain inhibitors, including JQ1,105 I-BET151,106,107 and I-BET762,106,108 have demonstrated in vitro and in vivo activity against several hematopoietic malignancies. It has also been evaluated whether BRD4 might be a target in advanced SM. Indeed, BRD4 was found to be expressed in HMC-1.1, HMC-1.2, ROSAKIT WT and ROSAK- IT D816V cells as well as in primary neoplastic MC.109 Independently of the grade or variant of disease, neoplas- tic MC exhibit nuclear BRD4.109 However, in ASM and MCL, neoplastic MC also express substantial amounts of cytoplasmic BRD4.109 In line with this observation, HMC- 1 and ROSA cells express cytoplasmic and nuclear BRD4 as well.109 The KIT-TKI midostaurin and dasatinib sup- pressed the expression of BRD4 in all MC lines.109 BRD4- specific short hairpin RNA and JQ1 decreased the prolif- eration of HMC-1 and ROSA cells.109 Based on these data,
BRD4 is a promising target in advanced SM, although this needs to be confirmed in forthcoming clinical studies.
Human mast cell leukemia-like cell lines as tools to develop in vivo models
In vivo models have been developed in order to under- stand the pathophysiology of SM better. In addition to transgenic mouse models,110,111 another approach is to cre- ate a SM-like disease in vivo by transplanting human neo- plastic MC into immunodeficient mice.
The HMC-1 cell line engrafts immunodeficient mice after intravenous or subcutaneous injection, giving rise to subcutaneous tumors after 2 to 5 months.11, 112 The reason why intravenous injection does not give rise to a MCL- like disease is unknown, but limits the usefulness of HMC-1 cells to establish an in vivo model of advanced SM. More recently, an in vivo model of advanced SM was established using ROSA cells. Indeed, we engineered a ROSA subclone, termed ROSAKIT D816V-Gluc, which naturally secretes Gaussia princeps luciferase (Gluc), used as a reporter.113 In this study, intravenous injection of NSG mice with ROSAKIT D816V-Gluc cells led to an advanced SM phenotype, with neoplastic MC invading the bone mar- row, spleen and liver, as testified by the quantification of engrafting cells by measuring Gluc reporter activity in peripheral blood and by an in vivo imaging system (IVIS).113 The detailed characteristics of this in vivo model are presented in Figure 4. All in all, this in vivo model of advanced SM is potentially the best available to date for in vivo testing of drugs previously identified as active in vitro on neoplastic MC.
Summary and future perspectives
Despite decades of intensive research, only a few human MC lines have been established to date: HMC-1, LAD-2,
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LUVA, ROSA and MCPV-1. While none of these cell lines simultaneously expresses the KIT D816V mutant and a functional FcεRI, making them useless for testing MC-sta- bilizing drugs or drugs interfering with FcεRI-induced sig- naling in the context of KIT D816V+ SM, some of these cell lines may qualify as MCL-like since they harbor SM-relat- ed KIT variants and/or other oncogenic molecules relevant to SM. Among all MC lines, HMC-1 cells have been most frequently used, but other more recently established MC lines, such as ROSA and MCPV-1, are now available and are being used in various preclinical studies. For example, these cell lines have been used to analyze in vitro the growth-inhibitory effects of antineoplastic drugs, including various KIT-TKI, on neoplastic MC. However, because neoplastic MC in advanced SM are triggered by KIT-inde- pendent signaling pathways and additional genetic lesions that confer resistance against KIT-TKI, it might be interest- ing to establish in vitro models of multi-mutated neoplastic MC, starting from established human KIT mutant-positive MC lines in which additional lesions, such as the S/A/R
combination of molecular lesions might be introduced. Such multi-mutated neoplastic MC lines should be useful to test combination therapies in vitro, and later in clinical tri- als in patients with advanced SM. With these approaches, new therapeutic concepts should be established in order to improve therapy in advanced SM.
Acknowledgments
The authors would like to thank Dr Patrick T. Gunning (Department of Medical Biophysics, University of Toronto, Ontario, Canada) for kindly providing the STAT-specific inhibitors presented in the manuscript. We also express our deep thanks to Dr Fawzia Louache (Inserm UMRS-1170, CNRS GDR 3697 Micronit, Institut Gustave Roussy, Université Paris- Sud, Université Paris-Saclay, Villejuif, France) for her invalu- able help with the in vivo studies presented in the manuscript. K.H. is supported by a research grant from the German Research Council (DFG; HA 2393/6-1). DM is supported by the DIR, NIAID, and PV is supported by the Austrian Science Fund (FWF) grants F 4701-B20 and F 4704-B20.
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76. Manley PW, Drueckes P, Fendrich G, et al. Extended kinase profile and properties of the protein kinase inhibitor nilotinib. Biochim Biophys Acta. 2010;1804(3):445-
61. Schittenhelm MM, Shiraga S, Schroeder A,
et al. Dasatinib (BMS-354825), a dual
SRC/ABL kinase inhibitor, inhibits the
kinase activity of wild-type, juxtamem- 453.
brane, and activation loop mutant KIT iso- forms associated with human malignancies. Cancer Res. 2006;66(1):473-481.
62. Shah NP, Lee FY, Luo R, Jiang Y, Donker M, Akin C. Dasatinib (BMS-354825) inhibits KITD816V, an imatinib-resistant activating mutation that triggers neoplastic growth in most patients with systemic mastocytosis. Blood. 2006;108(1):286-291.
63. Gleixner KV, Mayerhofer M, Sonneck K, et al. Synergistic growth-inhibitory effects of two tyrosine kinase inhibitors, dasatinib and PKC412, on neoplastic mast cells expressing the D816V mutated oncogenic variant of KIT. Haematologica. 2007;92(11):1451-1459.
64. Aichberger KJ, Sperr WR, Gleixner KV, Kretschmer A, Valent P. Treatment respons-
77. Hochhaus A, Baccarani M, Giles FJ, et al. Nilotinib in patients with systemic masto- cytosis: analysis of the phase 2, open-label, single-arm nilotinib registration study. J Cancer Res Clin Oncol. 2015;141(11):2047- 2060.
78. Bai Y, Bandara G, Ching Chan E, et al. Targeting the KIT activating switch control pocket: a novel mechanism to inhibit neo- plastic mast cell proliferation and mast cell activation. Leukemia. 2013;27(2):278-285.
79. Schneeweiss M, Peter B, Bibi S, et al. The KIT and PDGFRA switch-control inhibitor DCC2618 blocks growth and survival of multiple neoplastic cell types in advanced mastocytosis. Haematologica. 2018;103(5): 799-809.
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80. Evans E, Gardino A, Hodous B, et al. Blu-285, a potent and selective inhibitor for hemato- logic malignancies with KIT exon 17 muta- tions. Blood. 2015;126(23):568-568.
81. Evans EK, Gardino AK, Kim JL, et al. A pre- cision therapy against cancers driven by KIT/PDGFRA mutations. Sci Tran Med. 2017;9(414).
82. Lim KH, Tefferi A, Lasho TL, et al. Systemic mastocytosis in 342 consecutive adults: sur- vival studies and prognostic factors. Blood. 2009;113(23):5727-5736.
83. Chaix A, Lopez S, Voisset E, Gros L, Dubreuil P, De Sepulveda P. Mechanisms of STAT protein activation by oncogenic KIT mutants in neoplastic mast cells. J Biol Chem. 2011;286(8):5956-5966.
84. Page BD, Khoury H, Laister RC, et al. Small molecule STAT5-SH2 domain inhibitors exhibit potent antileukemia activity. J Med Chem. 2012;55(3):1047-1055.
85. Peter B, Bibi S, Eisenwort G, et al. Drug- induced inhibition of phosphorylation of STAT5 overrides drug resistance in neoplastic mast cells. Leukemia. 2018;32(4):1016-1022.
86. Gabillot-Carre M, Lepelletier Y, Humbert M, et al. Rapamycin inhibits growth and sur- vival of D816V-mutated c-kit mast cells. Blood. 2006;108(3):1065-1072.
87. Blatt K, Herrmann H, Mirkina I, et al. The PI3-kinase/mTOR-targeting drug NVP- BEZ235 inhibits growth and IgE-dependent activation of human mast cells and basophils. PLoS One. 2012;7(1):e29925.
88. Parikh SA, Kantarjian HM, Richie MA, Cortes JE, Verstovsek S. Experience with everolimus (RAD001), an oral mammalian target of rapamycin inhibitor, in patients with systemic mastocytosis. Leuk Lymphoma. 2010;51(2):269-274.
89. Baldus SE, Zirbes TK, Thiele J, Eming SA, Henz BM, Hartmann K. Altered apoptosis and cell cycling of mast cells in bone marrow lesions of patients with systemic mastocyto- sis. Haematologica. 2004;89(12):1525-1527.
90. Cervero C, Escribano L, San Miguel JF, et al. Expression of Bcl-2 by human bone marrow mast cells and its overexpression in mast cell leukemia. Am J Hematol. 1999;60(3):191- 195.
91. Hartmann K, Artuc M, Baldus SE, et al. Expression of Bcl-2 and Bcl-xL in cutaneous and bone marrow lesions of mastocytosis. Am J Pathol. 2003;163(3):819-826.
92. Aichberger KJ, Mayerhofer M, Gleixner KV, et al. Identification of MCL1 as a novel tar- get in neoplastic mast cells in systemic mas- tocytosis: inhibition of mast cell survival by MCL1 antisense oligonucleotides and syner- gism with PKC412. Blood. 2007;109(7): 3031-3041.
93. Aichberger KJ, Gleixner KV, Mirkina I, et al. Identification of proapoptotic Bim as a tumor suppressor in neoplastic mast cells: role of KIT D816V and effects of various tar- geted drugs. Blood. 2009;114(26):5342-5351.
94. Peter B, Cerny-Reiterer S, Hadzijusufovic E, et al. The pan-Bcl-2 blocker obatoclax pro- motes the expression of Puma, Noxa, and Bim mRNA and induces apoptosis in neo- plastic mast cells. J Leukoc Biol. 2014;95(1): 95-104.
95. Valent P, Cerny-Reiterer S, Herrmann H, et al. Phenotypic heterogeneity, novel diagnos- tic markers, and target expression profiles in normal and neoplastic human mast cells. Best Pract Res Clin Haematol. 2010;23(3): 369-378.
96. Teodosio C, Mayado A, Sanchez-Munoz L, et al. The immunophenotype of mast cells and its utility in the diagnostic work-up of systemic mastocytosis. J Leukoc Biol. 2015;97(1):49-59.
97. Pardanani A, Lasho T, Chen D, et al. Aberrant expression of CD123 (interleukin- 3 receptor alpha) on neoplastic mast cells. Leukemia. 2015;29(7):1605-1608.
98. Sotlar K, Cerny-Reiterer S, Petat-Dutter K, et al. Aberrant expression of CD30 in neoplas- tic mast cells in high-grade mastocytosis. Mod Pathol. 2011;24(4):585-595.
99. Blatt K, Cerny-Reiterer S, Schwaab J, et al. Identification of the Ki-1 antigen (CD30) as a novel therapeutic target in systemic masto- cytosis. Blood. 2015;126(26):2832-2841.
100. Florian S, Sonneck K, Hauswirth AW, et al. Detection of molecular targets on the sur- face of CD34+/CD38-- stem cells in various myeloid malignancies. Leuk Lymphoma. 2006;47(2):207-222.
101. Krauth MT, Bohm A, Agis H, et al. Effects of the CD33-targeted drug gemtuzumab ozogamicin (Mylotarg) on growth and mediator secretion in human mast cells and blood basophils. Exp Hematol. 2007;35(1): 108-116.
102. Alvarez-Twose I, Martinez-Barranco P, Gotlib J, et al. Complete response to gem-
tuzumab ozogamicin in a patient with refractory mast cell leukemia. Leukemia. 2016;30(8):1753-1756.
103. Zuber J, Shi J, Wang E, et al. RNAi screen identifies Brd4 as a therapeutic target in acute myeloid leukaemia. Nature. 2011;478(7370):524-528.
104. Herrmann H, Blatt K, Shi J, et al. Small-mol- ecule inhibition of BRD4 as a new potent approach to eliminate leukemic stem- and progenitor cells in acute myeloid leukemia AML. Oncotarget. 2012;3(12):1588-1599.
105.Filippakopoulos P, Qi J, Picaud S, et al. Selective inhibition of BET bromodomains. Nature. 2010;468(7327):1067-1073.
106. Chaidos A, Caputo V, Gouvedenou K, et al. Potent antimyeloma activity of the novel bromodomain inhibitors I-BET151 and I- BET762. Blood. 2014;123(5):697-705.
107. Wyspianska BS, Bannister AJ, Barbieri I, et al. BET protein inhibition shows efficacy against JAK2V617F-driven neoplasms. Leukemia. 2014;28(1):88-97.
108. Mirguet O, Gosmini R, Toum J, et al. Discovery of epigenetic regulator I-BET762: lead optimization to afford a clinical candi- date inhibitor of the BET bromodomains. J Med Chem. 2013;56(19):7501-7515.
109. Wedeh G, Cerny-Reiterer S, Eisenwort G, et al. Identification of bromodomain-contain- ing protein-4 as a novel marker and epige- netic target in mast cell leukemia. Leukemia. 2015;29(11):2230-2237.
110. Zappulla JP, Dubreuil P, Desbois S, et al. Mastocytosis in mice expressing human Kit receptor with the activating Asp816Val mutation. J Exp Med. 2005;202(12):1635- 1641.
111. Gerbaulet A, Wickenhauser C, Scholten J, et al. Mast cell hyperplasia, B-cell malignancy, and intestinal inflammation in mice with conditional expression of a constitutively active Kit. Blood. 2011;117(6):2012-2021.
112. Schumacher U, van Damme EJ, Peumans WJ, Butterfield JH, Mitchell BS. Lectin histo- chemistry of human leukaemic mast cells (HMC-1) transplanted into severe combined immunodeficient (scid) mice. Acta Histochem. 1998;100(1):1-9.
113. Bibi S, Zhang Y, Hugonin C, et al. A new humanized in vivo model of KIT D816V+ advanced systemic mastocytosis monitored using a secreted luciferase. Oncotarget. 2016;7(50):82985-83000.
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European Myeloma Network recommendations on tools for the diagnosis and monitoring of multiple myeloma: what to use and when
Haematologica 2018 Volume 103(11):1772-1784
Jo Caers,1,2 Laurent Garderet,3 K. Martin Kortüm,4 Michael E. O’Dwyer,5 Niels W.C.J. van de Donk,6 Mascha Binder,7 Sandra Maria Dold,8 Francesca Gay,9 Jill Corre,10 Yves Beguin,1,2 Heinz Ludwig,11 Alessandra Larocca,9 Christoph Driessen,12 Meletios A. Dimopoulos,13 Mario Boccadoro,9 Martin Gramatzki,14 Sonja Zweegman,6 Hermann Einsele,4 Michele Cavo,15 Hartmut Goldschmidt,16,17 Pieter Sonneveld,18 Michel Delforge,19 Holger W. Auner,20 Evangelos Terpos13 and Monika Engelhardt8
1Department of Hematology, University Hospital of Liege, Belgium; 2Laboratory of Hematology, GIGA-I3, University of Liège, Belgium; 3Department of Hematology, Hopital Saint Antoine, Paris, France; 4Department of Internal Medicine II, University Hospital of Wuerzburg, Germany; 5Department of Hematology, National University of Ireland Galway, Ireland; 6 Department of Hematology, VU University Medical Center, Amsterdam, the Netherlands, 7Department of Internal Medicine II, University Medical Center Hamburg- Eppendorf, Hamburg, Germany; 8Department of Medicine I, Hematology, Oncology & Stem Cell Transplantation, Medical Center, Faculty of Medicine, University of Freiburg, Germany; 9Department of Hematology-Oncology, University Hospital Città della Salute e della Scienza, Torino, Italy; 10Unit for Genomics in Myeloma, Institut Universitaire du Cancer – Oncopole, Toulouse, France; 11Wilhelminen Cancer Research Institute, Vienna, Austria; 12Department of Oncology and Hematology, Cantonal Hospital St. Gallen, Switzerland; 13School of Medicine, National and Kapodistrian University of Athens, Greece; 14Division of Stem Cell Transplantation and Immunotherapy, University of Kiel, Germany; 15Seragnoli 'Institute of Hematology, Bologna University School of Medicine, Italy; 16Department of Hematology, Rheumatology and Oncology, University Hospital Heidelberg, Germany; 17National Center for Tumor Diseases, Heidelberg Medical University, Germany; 18Department of Hematology, Erasmus MC Cancer Institute, Rotterdam, the Netherlands; 19Department of Hematology, University Hospital Leuven, Belgium and 20Centre for Haematology, Hammersmith Hospital, Imperial College London, UK
ABSTRACT
The diagnosis of multiple myeloma can be challenging, even for experienced physicians, and requires close collaboration between numerous disciplines (orthopedics, radiology, nuclear medicine, radiation therapy, hematology and oncology) before the final diagnosis of myeloma is made. The definition of multiple myeloma is based on the presence of clinical, biochemical, histopathological, and radiological markers of disease. Specific tests are needed both at presentation and dur- ing follow-up in order to reach the correct diagnosis and characterize the disease precisely. These tests can also serve prognostic purposes and are useful for follow-up of myeloma patients. Molecular analyses remain piv- otal for defining high-risk myeloma and are used in updated patient strat- ifications, while minimal residual disease assessment via flow cytometry, molecular techniques and radiological approaches provides additional prognostic information on patients’ long-term outcome. This pivotal information will guide our future treatment decisions in forthcoming clinical trials. The European Myeloma Network group updated their guidelines on different diagnostic recommendations, which should be of value to enable appropriate use of the recommendations both at diagno- sis and during follow-up.
Correspondence:
jo.caers@chu.ulg.ac.be
Received: January 21, 2018. Accepted: August 27, 2018. Pre-published: August 31, 2018.
doi:10.3324/haematol.2018.189159
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1772
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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GUIDELINE ARTICLE
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Introduction
The classification and differential diagnosis of mono- clonal gammopathies is based on clinical, biological and radiological criteria but remains challenging in certain cases. Multiple myeloma (MM) is the most common malignant gammopathy and is associated with a wide spectrum of signs and symptoms.1 In the past decade, the treatment options for patients with MM have increased considerably. Together with improved supportive care, these new regimens significantly prolong the survival of both younger and older patients.2 The 2014 revision of the diagnostic criteria for MM allows the initiation of treat- ment in patients defined only by biomarkers, annotated as SLIM criteria [bone marrow (BM) infiltration >60%, involved/uninvolved serum free light-chain (SFLC) ratio >100 or >1 focal lesion >5 mm as determined by magnetic resonance imaging (MRI)], without waiting for conven- tional CRAB criteria (hypercalcemia, renal impairment, anemia, bone disease) to occur.3,4 Both the SLIM biomark- er and CRAB criteria are listed in Figure 1. Given the recent evolution in diagnosis and response assessment, members of the European Myeloma Network (EMN) agreed to review and recommend diagnostic and response criteria to allow their discriminating use in daily practice and current care of patients’ .
Methodology
These recommendations were developed by a panel of clinical experts on MM based on evidence of published data through August 2017. Expert consensus was used to suggest recommendations, where sufficient data were lacking. The final recommendations were classified based
on the GRADE criteria,5 which incorporates the strength and quality of evidence (Online Supplementary Table S1). Based on discussions at the 2017 EMN Trialist meeting (Baveno, Italy) guidelines were prepared and circulated among all panel members. The manuscript subsequently underwent revision in three rounds until the EMN experts reached consensus. In line with the guidelines of the International Committee of Medical Journal Editors, authorship was based on active contribution during dis- cussion, writing and revision of the guidelines.
European Myeloma Network recommendations
Diagnostic tools
Blood tests
A defining feature of plasma cell (PC) disorders is the secretion of monoclonal immunoglobulins, often referred to as a monoclonal M-protein, which can be used as a diagnostic marker, but also for the follow-up of the dis- ease. Its heavy- and light-chain components can be identi- fied by immunofixation and further quantified by serum protein electrophoresis and/or a serum free light-chain (SFLC) assay. It should be kept in mind that with persist- ing disease and possible de-differentiation of myeloma cells, the capacity to produce M-proteins may decrease or be completely lost (light-chain escape). In those patients, low M-protein levels, the presence of light chains only, or even complete absence of M-proteins and light chains may be mistaken as an ongoing or evolving response.6
Of note, immunofixation is approximately 10-fold more sensitive than serum protein electrophoresis and is required at diagnosis to characterize the phenotype of the M-protein, and for confirmation of a complete response, which is defined as being immunofixation-negative.7
Figure 1. The differential diagnosis between monoclonal gammopathy of undetermined significance, smoldering myeloma and multiple myeloma. The discrimi- nation between these monoclonal gammopathies is based on: (i) the plasma cell infiltration in the bone marrow, (ii) the presence of clinical symptoms related to myeloma disease and (iii) the existence of biomarkers of disease that allow initiation of treatment. MGUS: monoclonal gammopathy of undetermined significance; SMM: smoldering multiple myeloma; MM: multiple myeloma; BM: bone marrow; PC: plasma cells; FLC: free light chain; MRI: magnetic resonance imaging.
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Serum electrophoresis and immunofixation may not be able to detect light-chain aberrations in patients with oligo-secretory disease, such as light-chain MM. Due to their low molecular weight, these SFLC are rapidly cleared by the kidneys. In such cases, the monoclonal burden should be measured in a 24 h urine collection or in the serum by an automated SFLC immunoassay (Grade 1A), the latter having a higher sensitivity to detect and quanti- fy the involved free light chains.7 In concordance with the International Myeloma Working Group (IMWG), we rec- ommend the performance of serum immunofixation and electrophoresis on serum and urine samples and a SFLC assay for the diagnosis of a monoclonal PC disorder (Grade 1A).
Additional laboratory tests should be performed for the diagnosis and follow-up of MM patients, such as a com- plete blood count to evaluate possible cytopenias, blood smears to look for circulating PC and general biochem- istry tests (renal and liver function tests, calcium, phos- phate, uric acid, albumin, creatinine, lactate dehydroge- nase, C-reactive protein, β2-microglobulin). Quantification of serum immunoglobulins by nephelom- etry enables an indirect measurement of the M-protein or the recognition of a secondary hypogammaglobinemia and is recommended for any patient presenting with a gammopathy (oligo-, poly- or monoclonal) (Grade 1A).
The HevyLite® immunoassay quantifies both the involved and uninvolved intact immunoglobulin chains and quantifies them separately (IgGκ/λ, IgAκ/λ, IgMκ/λ).8 This assay has prognostic value for progression-free and overall survival9 and seems particularly useful when the M- protein is difficult to measure via serum protein elec- trophoresis. This assay is not yet part of the routine workup of MM patients, but may be of value in the follow- up of patients and has been included in clinical trials.10
Urine analysis
Proteinuria should be assessed on urine samples from all patients at diagnosis and during the follow-up. If pro- teinuria is present, it should be quantified in a 24 h urine collection. Total 24 h protein and Bence-Jones proteinuria should be evaluated by densitometry, electrophoresis and immunofixation. To detect low amounts of monoclonal proteins, it is recommended that the urine is concentrated 200-fold.11 These 24 h urine collections are often inconsis- tently performed, resulting in incomplete urine collection. In addition, renal function can influence the accuracy of the results, a fact which should be taken into considera- tion when interpreting laboratory values. The SFLC assay can be used for the follow-up of patients with light-chain MM. A recent French study, focusing on patients with light-chain MM, demonstrated that the SFLC assay is superior to 24 h urine collection for: (i) identifying patients with measurable disease, (ii) following their response to initial therapy, and (iii) giving a prognostic indication of the patients’ response and overall survival.12 This study included 113 patients with light-chain MM, all of whom had an abnormal SFLC ratio and measurable disease parameters in serum, while only 64% patients had measurable M-proteins in the urine, as determined by urine protein electrophoresis. Similar results were found in 576 patients with light-chain MM from the UK Myeloma IX and XI trials. The disease burden of the patients with light-chain MM could be measured and monitored by urine protein electrophoresis in 80% of
cases. Of the remaining patients 113 (97%) had involved free light chains >100 mg/L, which was sufficient to measure response to therapy.13 These two studies con- firmed the importance of SFLC measurements to diag- nose and monitor patients with light-chain or oligosecre- tory MM. The replacement of urine studies by the SFLC assay for all myeloma patients remains controversial, since an Eastern Cooperative Oncology Group study on 399 MM patients (of whom only a minority had light- chain MM disease) found only a weak correlation between results of the SFLC assay and 24 h protein analy- sis.14
In line with the IMWG guidelines,15 we recommend the SFLC assay for the diagnosis and monitoring of patients with oligosecretory disease (Grade 2B). However, for patients with measurable urinary M-proteins, MM should be monitored by 24 h urine collections. When albumin is the dominant protein found in the urine, a glomerulopathy (such as AL-amyloidosis or light-chain deposition disease) should be excluded. The 24 h urine collection remains important when results are discordant.
Bone marrow studies
A BM aspirate enables quantification of infiltrating PC and cytogenetic studies on purified PC. Unfortunately, dilution by peripheral blood during aspiration or the pres- ence of patchy disease (uneven distribution of MM cells throughout the BM) may result in an underestimation of tumor infiltration.16 We therefore recommend an addi- tional BM trephine biopsy, which may generate comple- mentary information (Grade 1B). A BM biopsy correctly identified MM disease in 95% of symptomatic patients with a low PC count on the initial BM smears.16 The cor- rect quantification of BM PC is also important because of the 60% cut-off as a biomarker of malignancy. The IMWG earlier recommended retaining the highest PC infiltration in case of discrepancy. Finally, the monoclon- ality of PC in the diagnostic sample should be confirmed by multiparameter flow cytometry or by immunohisto- chemistry confirming light-chain restriction.
Flow cytometry of bone marrow cells
In cases of monoclonal gammopathies, the most rele- vant information provided by multiparameter flow cytometry is the identification and enumeration of neo- plastic versus polyclonal BM PC. Regardless of the disease category, these neoplastic PC share similar immunophe- notypic features, which are distinct from those of normal PC. Typically, CD38, CD138 and CD45 (together with light scatter characteristics) are the best backbone mark- ers for the discrimination of PC. In addition, expression of CD19, CD56, CD117, CD20, CD28, CD27 and CD81, together with cytoplasmic immunoglobulin light-chain restriction, allows a clear discrimination between nor- mal/reactive versus monoclonal PC17 and was used by the EuroFlow consortium to create a standardized panel allowing the quantification and immunophenotypic char- acterization of neoplastic PC.18
Due to dilution and the sometimes patchy disease dis- tribution, multiparameter flow cytometry often underes- timates the infiltration but remains important for detec- tion of monoclonal PC in the peripheral blood and for the detection of minimal residual disease (MRD) in the BM. The Mayo Clinic group reported on the prognostic importance of circulating neoplastic cells in patients with
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newly diagnosed or relapsing MM.19,20 They recently monitored circulating MM cells at diagnosis and after induction therapy by multiparameter flow cytometry and confirmed inferior progression-free and overall survival for patients with persistent circulating MM cells before transplantation.21
Molecular studies
Cytogenetics
MM remains a heterogeneous disease with some patients progressing rapidly, while others survive more than 10 years. This clinical diversity is mainly driven by genetic abnormalities affecting the biological characteris- tics of MM cells.22 These alterations, summarized in Table 1, are important prognostic factors and can be divided into primary, disease-initiating abnormalities (hyper- diploidy and translocations involving the IGH locus) and secondary events, related to further progression of the disease.23 Fluorescence in situ hybridization on interphase cells, performed after purification of CD138+ cells or after counterstaining for the monoclonal light chains, is the technique required to detect these abnormalities.24 Alternative techniques that can be used are single- nucleotide polymorphism arrays, which are able to detect loss of heterozygosity and numerical chromosome abnor- malities, and comparative genomic hybridization arrays, which mainly reveal numerical abnormalities.
Up to 65% of patients with MM have translocations that involve the immunoglobulin heavy chain gene (IGH) on chromosome 14q32. The prevalence and prognostic impact of these IGH translocations vary according to the partner chromosome (Table 1). Hyperdiploidy generally consists of numerical gains (of the odd chromosomes)
with a few structural changes, and is usually associated with longer overall survival. Not all trisomies have the same prognostic impact: trisomy 21 impairs, while tri- somies 3 and 5 improve overall survival and may partially abrogate the negative impact of del17p and t(4;14).25
The most recurrent secondary alterations are dele- tion/monosomy of chromosome 13, deletion of chromo- some 17p13, chromosome 1 abnormalities (1p deletions and 1q gains/amplifications), and C-MYC translocations. Deletion 17p13 is considered the most detrimental prog- nostic factor (due to short remission after high-dose ther- apy and an increased incidence of extramedullary dis- ease) and is present in 8-10% of untreated patients.26 This deletion becomes clinically relevant when identified in the majority of PC. Different percentages (varying from 10%-60%) have been proposed to define a thresh- old that is associated with an impaired prognosis.27-29 The presence of a biallelic inactivation (i.e. by an additional mutation) of TP53 may particularly shorten overall sur- vival.30 Aberrations of chromosome 1 (either 1q21 gains/amplifications or deletions of 1p32) are common and associated with shorter progression-free and overall survival, particularly the less frequent del(1p32).31 Patients with adverse cytogenetics may have additional aberrations: in the British MRC IX trial patients with two adverse cytogenetic lesions had a median overall survival of 2 years, while the survival of patients with three aber- rations (an adverse IGH translocation, +1q21 and del17p13) was only 9 months.32 This inferior survival of patients with additional genetic abnormalities was also found in an Intergroupe Francophone du Myelome study that focused on patients with either del17p13 or t(4;14): for patients harboring t(4;14), multivariate analyses showed
Table 1. Recommended cytogenetic studies with implicated gene alterations and related prognosis.
Cytogenetics
Del17p13 P53
t(4;14)(p16.3;q32)
Gain 1q21 CKS1B
Del 1p32, Del 1p22
t(11;14)(q13;q32)
t(14;16)(q32;q23)
Hyperdiploidy of odd chromosomes
Genetic event Frequency
5-15% Independent marker,
FGR3 15% MMSET
34-40% Independent marker,
Prognosis
with negative impact on PFS and OS
Independent marker, with negative impact on PFS and OS
with negative impact on PFS and OS
Independent marker, with negative impact on PFS and OS
Good prognosis
Controversial
Standard prognosis, unless associated with other negative prognostic markers
Response to PI
Negative prognostic factor
Improves survival compared to classic agents
Negative prognostic factor
Negative prognostic factor
Good prognosis
Standard prognostic factor
Response to IMiD
Negative prognostic factor
Pomalidomide seems beneficial
Unfavorable for any IMiD
Negative prognostic factor
Good prognosis
Remarks
Most important prognostic factor
Ref
31, 60, 97
27, 98-100
Might be directly implicated in bortezomib resistance
CDKN2C
CCND1
CMAF
7-17%
20%
2-3%
60%
Sensitive
to venetoclax
101
102
103
Considered as a 104 negative prognostic
factor, but not confirmed in IFM study
May neutralize the 25 negative prognostic impact of del17p
or t(4;14)
PFS: progression free survival, OS overall survival, FGFR3: fibroblast growth factor receptor 3, MMSET: multiple myeloma SET domain, PI proteasome inhibitor, IMiD: immunomodulatory drug, CKS1B: CDC28 protein kinase regulatory subunit 1B, CDKN2C: cyclin-dependent kinase 4 inhibitor C, CCND1: cyclin-D1, MAF: musculoaponeurotic fibrosarcoma, IFM: Intergroupe Francophone du Myelome
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a shorter overall survival for patients with a combined del(13q14) or del(1p32). Among patients with del17p13, overall survival was shorter in those with del(1p32).33
Next-generation genome sequencing
Next-generation sequencing allows the detection of baseline clonal heterogeneity,34 clonal tiding35 and linear and branching evolution and contributes to a better under- standing of MM disease biology.36 The availability of more than 2000 sequenced MM genomes has essentially defined the genomic landscape. These data revealed a high incidence of clinically relevant genomic aberrations, including oncogenic RAS mutations, but also a number of rarer and potentially actionable lesions, such as BRAF mutations.37,38 Of note, the vast majority of available genomic data in MM is still derived from samples obtained at diagnosis and does not, therefore, necessarily reflect the situation during disease progression. In addi- tion, the clinical relevance of most mutations has not yet been determined and is undergoing investigation in large sequencing programs (CoMMpass, The Myeloma Genome Project and others).39,40 No mutation screening has yet been implemented in standard clinical workflows, but mutational analyses may help to identify potential therapeutic targets (such as BRAF mutations) and to strat- ify of patients in clinical trials.
Gene expression profiling
Based on microarrays to study mRNA expression, gene expression profiling gives a global snapshot of disease biology and may help clinicians to classify patients into separate groups with distinct outcomes. The University of Arkansas pioneered this technique to stratify MM patients
and to characterize individuals’ disease at the molecular level.41 They identified gene expression profiling patterns that allowed MM patients to be grouped in seven disease classes. Further correlation of their microarray results with survival data of individual patients identified a list of 70 genes (GEP70) that had strong prognostic information.41 Similarly, the HOVON group identified a 92-gene signa- ture (termed SKY92), based on the gene expression profil- ing results of the Hovon-65 trial.42,43 Other gene expression profiling-based risk models have been developed, such as the IFM-15 and MRC-IX-6 gene signatures44,45 Although not routinely determined in the majority of laboratories within or outside Europe, both the GEP70 and the SKY92 profiles are commercially available.
Imaging
Traditionally, osteolytic bone disease was investigated by conventional skeletal radiography. The 2014 IMWG disease criteria also considered small osteolytic lesions (≥5 mm), detected by computed tomography (CT) or com- bined 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET/CT) as symptoms of myeloma-induced bone disease.3 Taking into account these definitions, in 2015 the EMN proposed a relevant algorithm for guiding the choice of imaging technique.46,47 Different European centers have integrated CT into their diagnostic work-up based on its superior sensitivity and its ease of operation This choice was supported by the recent implementation as a national standard of care in the diagnostic workup of patients with suspected MM in the UK and elsewhere.48 Whole-body CT has also been integrated into the diagnos- tic work-up of the European Society of Medical Oncology49 and the upcoming IMWG guidelines.
Table 2. Recommendations on further examinations at diagnosis, for response assessment, during follow-up and at relapse.
Diagnostic site
Bone marrow
Blood
Urine
Imaging
Tool
BM cytology and biopsy to confirm plasmacytosis and monoclonality
Flow cytometry
Cytogenetics Obligatory
Diagnosis
Obligatory
At response
Obligatory*
Optional
Not required
Not required Obligatory Obligatory Recommended *** Obligatory Obligatory Obligatory Obligatory Recommended
Obligatory Recommended†
Not required Optional††† Not required
At follow-up
Not required
Not required
Not required
Not required Obligatory Obligatory
At relapse
Obligatory**
Optional
Optional
Not required Obligatory Obligatory Recommended *** Obligatory Obligatory Obligatory Obligatory Obligatory
Obligatory Recommended†
Recommended Optional Optional
Recommended
Advanced techniques: GEP, NGS Blood count and blood smear Serum electrophoresis and IF Serum free light chain
Serum immunoglobulin levels Renal and liver function tests Calcium
Lactate dehydrogenase Albumin, β2-microglobulin
Urine sample to check for proteinuria and Bence-Jones proteins
24 h urine collection
Low dose whole-body CT PET/CT
Whole-body MRI
Optional Obligatory Obligatory
Recommended Obligatory Obligatory Obligatory Obligatory Obligatory
***
Recommended Obligatory Obligatory Obligatory Obligatory
***
Obligatory Recommended†
Recommended†† Optional Optional
Recommended Obligatory
Recommended†
When symptomatic When symptomatic When symptomatic
BM: bone marrow; GEP: gene expression profiling; IF: immunofixation; NGS: next generation sequencing; CT: computed tomography; PET: positron emission tomography; MRI: magnetic resonance imaging; *Obligatory for patients in complete response. **Obligatory for patients with light chain escape, oligosecretory disease, *** SFLC monitoring is obligatory for patients with light-chain disease.†Obligatory in the case of proteinuria.††Obligatory when radiographs do not show osteolytic lesions †††PET/CT is required for con- firmation of minimal residual disease negativity.
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The risk of pathological fractures or neurological com- plications should be assessed in patients with lytic lesions. In this regard, MRI is the preferred examination to detect spinal cord compression. If whole-body CT is not avail- able, conventional radiographs can still be used but must be interpreted with their limited sensitivity in mind. In asymptomatic patients without lytic lesions, axial MRI or whole-body MRI should be considered to assess the pres- ence of focal lesions (Grade 1B). Addition of dynamic con- trast enhancement or diffusion weighted imaging to a whole-body MRI protocol provides additional informa- tion on BM vascularization, cellularity, and composition and improves the sensitivity of MRI.50,51 Two or more focal lesions on MRI are considered as a MM-defining biomark- er.52 18F-FDG PET/CT can replace whole-body CT, if image acquisition of CT allows a detailed evaluation of the bone structures from vertex to knees, including both arms (Grade 1B).53 18F-FDG PET/CT is important to assess the presence of extramedullary disease, known to be an inde- pendent prognostic factor.54 The integration of MRI, PET- CT and whole-body CT always requires experience, inter- disciplinary consensus and reflection and needs to be cor- related with blood, urine and BM results. Finally, baseline 18F-FDG PET/CT scans enable post-treatment follow-up of hypermetabolic regions with a greater sensitivity than MRI.54,55 PET/CT is also useful in confirming MRD.56
European Myeloma Network recommendations for the diagnosis of multiple myeloma:
The initial work-up should include: complete blood count, kidney function tests, serum protein electrophoresis with immunofixation, serum albumin, β2-microglobulin, lactate dehydrogenase, C-reactive protein, calcium, serum free light chains (especially useful in the case
of light-chain multiple myeloma), 24 h protein collection with protein quantification, electrophoresis and urine immunofixation, and bone marrow (aspiration only is acceptable) studies to quantify and char- acterize abnormal plasmacytosis (Table 2). The intervals between follow-up studies depend on the response obtained and the patients’ characteristics, as proposed in Table 3 (Grade 2C). After CD138+ plasma cell sorting, fluorescence in situ hybridization analysis should include at least t(4;14) and del17p; analysis of t(14;16), 1q21 gain and del(1p32) are also recommended. In addition, bone integrity needs to be evaluated with whole-body computed tomography and/or whole-body magnetic resonance imaging (at least axial). Quantification of the level of plasma cell infiltration, serum free light chains and magnetic resonance imaging assessment are required to assess the SLIM-CRAB biomarkers that define early active multiple myeloma. At relapse, the extent of myeloma-induced bone disease should be re-evaluated, especially if the relapse occurs late after the initial diagnosis.
Staging and prognosis
Disease-specific prognostic scores
The variable outcome of MM patients depends on dif- ferences in disease biology, global disease burden and the health status of the patient. Researchers have developed clinical scoring systems in order to estimate individual prognosis. The degree of anemia, renal failure and osteol- ysis were the first disease-related prognostic biomarkers described in MM and were all included in the Salmon & Durie staging system. Subsequently, β2-microglobulin, albumin and C-reactive protein levels, and proliferative activity of MM cells were found to be additional prognos- tic factors, and albumin and β2-microglobulin levels were incorporated in the International Staging System (ISS) in
Table 3. Follow-up of multiple myeloma patients according to response and patients’ characteristics (general strength of these recommendation GRADE 2C).
Patient risk group
General myeloma population
Special patient groups
Response to prior treatment
In CR or VGPR
In PR
With biological progression
Frail patients
LC-MM and patients with renal failure
Patients with extramedullary disease
Blood and urine tests
Follow-up with blood and urine samples, initially every 1-3 months* with
gradually increasing intervals (max 6 months)
Follow-up with blood and urine samples, initially every 1-2 months* with gradually increasing intervals (max 6 months)
Regular follow-up with blood and urine samples, initially every month. Consider treatment initiation for patients with high-risk disease
Follow-up with blood and urine samples,
every 2 months; if stable increase intervals
to 3 months. Involve family doctor for follow up
Blood, SFLC and 24 h urine collection.
Follow-up with SPEP, UPEP and SFLC every month; if stable, increase intervals to 3 months
Imaging
Imaging studies should be performed when there are signs of bone disease. Consider PET/CT for high-risk patients
Imaging studies should be performed when there are signs of bone disease. Consider PET/CT for high-risk patients.
Imaging using the whole body approach is recommended.
Imaging directed to the affected region only when signs of progressive bone disease.
Imaging studies should be performed when there are signs of bone disease
PET/CT is the preferented technique for follow-up. Recommended every 6 months and obligatory in the case of progression
CR: complete response;VGPR: very good partial response; PR: partial response, PET/CT: positron emission tomography–computed tomograph; max: maximum , SPEP: serum pro- tein electrophoresis; UPEP: urine protein electrophoresis; SFLC: serum free light chain, LC-MM: light-chain multiple myeloma, 24 h: 24 hours * The monitoring intervals are gen- erally shorter for patients with high-risk disease (monthly follow-up) than for patients with standard-risk disease (every 2 to 3 months).
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Table 4. The Revised-International Staging System is one of the best stratification methods; it is based on routinely available cytogenetic and biochem- istry tests (Palumbo et al.).56
R-ISS definitions
R-ISS stage I
R-ISS stage II R-ISS stage III
Determinants
ISS stage I, no high-risk CA, and normal LDH
Other combinations
ISS stage III plus high-risk
CA or high LDH
Number
871 (28%)
1894 (62%)
295 (10%)
OS (5 years)
82%
62%
40%
Median OS
NR
83 months
43 months
PFS (5 years)
55%
36%
24%
Median PFS
66 months
42 months
29 months
R-ISS Revised- International Staging System; ISS: International Staging System; OS: overall survival; PFS: progression free survival; CA; cytogenetic abnormalities; LDH: lactate dehy- drogenase; NR: not reported.
2005. Other biomarkers have been identified and include markers of tumor cell proliferation, cytokines, pro-angio- genic factors, indicators of bone remodeling, circulating (exosomal) miRNA and imaging abnormalities. Another promising biomarker is the serum level of shed B-cell mat- uration antigen, which correlates well with BM PC infil- tration and declines according to tumor response.57 Follow-up of serum B-cell maturation antigen levels seems of interest in patients with non-secretory disease, for whom we lack reliable parameters in the blood; future studies are therefore warranted.
Apart from the often still reported Salmon & Durie stag- ing system, the ISS and revised (R)-ISS are frequently used as staging systems; in the latter systems, the β2- microglobulin and albumin levels reflect patients' tumor burden, turnover rate, presence of renal impairment, and nutritional and performance status.58 In order to improve the prognostic performance of the ISS score, the IMWG updated it, adding high-risk cytogenetics [t(4;14), t(14;16), and del17p determined by interphase fluorescence in situ hybridization] and elevated serum lactate dehydrogenase (Table 4).59 These factors had been previously identified as relevant risk factors for early progression after autologous transplantation.60 Of note, the ISS and R-ISS give prognos- tic information at diagnosis, but have not been validated in relapsed/refractory MM.
Frailty and co-morbidities
Once a treatment has started, adherence to the estab- lished protocol remains a major clinical concern in elderly and frail patients. This requires an individualized approach in which therapeutic decisions should be driven by both disease features and the patient’s characteristics. As in other malignancies, comprehensive geriatric assess- ments have been evaluated to assess patients’ functional, cognitive and mental status, comorbidities, nutrition and presence of geriatric symptoms. Palumbo and co-workers developed a retrospective simplified geriatric assessment, named the IMWG-Frailty Index, in which age, the Charlson Comorbidity Index, activities of daily living and instrumental activities of daily living were used to dis- criminate between fit, intermediate-fit and frail patients, showing different incidences of severe adverse events, progression-free survival and overall survival.61 Expectedly, more severe adverse events and treatment discontinua- tions were reported in frail patients. The most extensive retrospective and prospective tests and validation analyses were performed within the German study group, who prospectively assessed the IMWG-Frailty Index with the revised Myeloma Comorbidity Index (R-MCI) and other comorbidity indices.62 A second prospective German
study including 801 MM patients determined that impaired renal and pulmonary function, poorer Karnofsky performance status, frailty and age were independent, multivariate risk factors for overall survival. Addition of cytogentic abnormalities resulted in the weighted revised Myeloma Comorbidity Index, which is able to assess patients' physical condition accurately and is simple to apply in the clinic.63 Although not yet proven via random- ized treatment algorithms, there is circumstantial evi- dence that limited induction therapy, careful dose modifi- cations and reductions, sensible use of supportive care and watchful surveillance of unfit and frail patients may improve patients’ outcome further.64 The EMN insists on developing trials, specifically designed for frail patients, for further refinement of frailty-related diagnostics and best treatment selection.65
Drug-related biomarkers
While prognostic factors regarding disease evaluation are listed above, drug-related biomarkers are being assessed to predict response to treatment and, possibly, to facilitate optimal treatment while avoiding ineffective therapies and unnecessary toxicity. Recent pharmacogenomic studies revealed gene signatures that could predict the clinical out- come after treatments based on immunomodulatory drugs66 or bortezomib.67 The expression of cereblon, an intracellular binding partner of immunomodulatory drugs has been intensively studied as a biomarker and initial studies corre- lated cereblon levels with the outcome of MM patients receiving treatment with such drugs.68-71 These studies used quantitative real time PCR analysis, gene expression profil- ing or immunohistochemistry to quantify cereblon expres- sion and showed that loss of cereblon expression was asso- ciated with resistance to immunomodulatory drugs. Further investigations revealed limitations of these assays, because both splice variants of cereblon and point mutations were described.72,73 When exploring predictors for tumor respons- es to daratumumab, higher CD38 expression was found on MM cells of responsive patients. However, good responses were also seen in patients with lower CD38 expression, an observation confirmed in a second study that showed that CD38 expression level was not necessarily predictive of response in advanced MM; nevertheless attempts to assess agents that keep CD38 upregulation increased, e.g., all-trans retinoic acid and histone deacetylase inhibitors, are being pursued pre-clinically and clinically.74,75
Finally, expression of anti-apoptotic proteins, BCL-2, BCL-XL or MCL-1, measured by quantitative real-time PCR, predict pharmacological responses to the bcl-2 inhibitor venetoclax, which is mostly active in patients harboring t(11,14) translocations.76
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European Myeloma Network recommendations:
The International Staging System score and, whenever possible, the Revised International Staging System score, should be determined at diagnosis to assess prognosis. At least a minimal frailty assessment should be performed to aid the choice of induction therapy, dose amendments and supportive care. Although of interest due to their prognostic and predictive value, biomarkers, such as cereblon and CD38 protein expression, are not routinely assessed in daily multiple myeloma care, while fluorescence in situ hybridization for t(11;14) should be performed if treatment with venetoclax is a clinical option.
Response assessment
The implication of the results of an SFLC assay and MRD assessment prompted the IMWG to update MM response criteria.77 In 2011, two new categories, stringent complete response and very good partial response, were added. Correct disease assessment is not only crucial for reporting in clinical trials, it also indicates prognosis in individual cases.77,78 It is well known that patients who obtain a com- plete response following induction have improved progres- sion-free and overall survival after intensive treatment.79
Patients should, therefore, be evaluated before initiation of each treatment cycle to determine their response to ther- apy. For MM patients with intact immunoglobulins, the recommended method for monitoring is quantification of serum and urinary M-protein. Whether all serum (and urine) parameters have to be checked after each cycle, rather than after every two or three cycles is left to the dis- cretion of each physician, taking into account disease aggressiveness, organ (i.e. renal) impairment and various other factors. To confirm a stringent complete response, normalization of the SFLC values and disappearance of monoclonal PC infiltration in the BM should be added to negative immunofixation on serum and urine samples. The BM must be evaluated in order to confirm a complete response, but this can be done at some time after the end of treatment, allowing full recovery of the BM. Of note, BM infiltration can be heterogeneous with persisting focal lesions in an otherwise recovered BM (earlier referred to as patchy disease). The follow-up of patients with light-chain MM and measurable M-protein levels in urine should include 24 h urine collections. The SFLC assay generally allows response assessment in patients with oligosecretory disease with unmeasurable serum and urine M-protein lev- els [serum M-protein <1 g/dL (10 g/L) or urine M-protein <200 mg/24 h]. If the SFLC assay is not informative, BM plasmacytosis should be assessed.77
The definition of relapse applies to a patient in complete response who experiences reappearance of MM, while pro- gression refers to patients with an increasing disease burden from a baseline or persistent residual disease. An additional assessment for confirmation is mandatory before initiating a new line of therapy. MM progression can be determined biochemically (increase in an existing monoclonal peak), or by radiological and clinical criteria. The interested reader can find the criteria for relapse and disease progression recently described by the IMWG.77 Response assessment can be challenging, especially in cases of deep response after the use of monoclonal antibodies, which may interfere with quantification of the M-protein and may require spe- cific assays.80
Minimal residual disease
Current induction regimens, in association with autolo- gous stem cell transplantation, achieve very high
response rates and the responses are often deep. Unfortunately, however, MM often recurs due to residual MM cells, drug resistance and/or persistence of resistant dormant subclones.81 MRD can be assessed by multipara- meter flow cytometry, polymerase chain reaction (PCR)- based methods or next-generation sequencing to identify persistent clonal cells. Recent studies, listed in Table 5, confirmed the prognostic impact of MRD status as an independent variable for outcome.82 In the future, MRD will be more widely used in clinical trials to guide treat- ment choices and probably as a surrogate marker for pro- gression-free and overall survival.56
Conventional flow-MRD approaches, based on multi- ple institutional non-standardized protocols, can reliably identify malignant PC and discriminate aberrantly expressed cell surface markers in approximately 90% of patients (with a sensitivity of detecting 10−4 atypical PC in normal BM). Recent studies conducted by Spanish and UK groups have shown that negative MRD by multipara- meter flow cytometry is predictive for both progression- free survival and overall survival, even in patients who achieved a complete response.83,84 Recent technical advances have increased the sensitivity of next-genera- tion flow cytometry protocols down to the 10–6 range.85
MRD analysis by PCR detects persistent residual tumor cells through the amplification of a tumor-specific molec- ular marker. The IGH rearrangement is used as a marker of clonality in various B-cell malignancies.86 Allele-specific oligonucleotide PCR with primers complementary to the heavy chain variable sequence remains one of the most sensitive approaches to detect residual malignant PC, reaching a sensitivity of 10−5.87 Unfortunately, it is a labo- rious, time-consuming approach that is not widely avail- able because of its dependence on patient-specific primers and probes for quantitative PCR.
Next-generation sequencing of the IGH rearrangement segments provides insights into the architecture of the B- lineage repertoire with consensus primers. Since the B- lineage repertoire includes the malignant PC clone in BM, next-generation sequencing of IGH enables a quantitative determination of MRD, without per-patient customiza- tion, provided that the malignant clone was identified in a diagnostic sample or a sample taken during active dis- ease.88 Results from next-generation sequencing are high- ly concordant with flow-based MRD detection, highly reproducible and reach a sensitivity of 10−6.89-91 A lack of standardization and limited commercial availability are the main restraints for next-generation sequencing. Flow cytometry and molecular techniques both require an appropriate BM sample. Heterogeneous BM infiltration and peripheral blood dilution can be major hurdles to the evaluation of MRD. Since neither of these techniques is able to detect extramedullary disease, they should be combined with imaging studies.
Imaging is a third approach to evaluate MRD in MM. Both PET/CT and MRI have been evaluated in this set- ting.53,55 Regarding PET/CT, two large studies assessed the prognostic value of negative PET/CT after induction and autologous stem cell transplantation.55,92 Both studies found that PET/CT-negative patients had a better pro- gression-free and overall survival compared to PET/CT- positive patients (52 versus 38 months and 5-year esti- mates of 90% versus 71%, respectively).92 In the French IMAJEM study, MRD was evaluated in 86 patients via PET-CT and flow cytometry. Although the concordance
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Table 5. Recent studies on minimal residual disease and the implications for progression-free and overall survival of patients with multiple myeloma.
N. Reference
#1 Lahuerta et al., JCO 2017.105
#2 Chakraborty et al., Biol Blood Marrow
Transplant 2017.106
#3 Nadiminti et al., OncoTargets and
Therapy 2017.107
#4 Paiva et al.; Blood 2016.108
#5 Ludwig et al.; BJH 2015.109
#6 Roussel et al.; JCO 2014.110
#7 Mateos et al.; Blood 2014.111
#8 Oliva et al., Oncotarget 2017.112
#9 Puig et al.; Leukemia 2014.113
#10 Ferrero et al.; Leukemia 2015.114
#11 Martinez-Lopez
et al.; Blood 2014.90
#12 Chari et al.; Blood 2017.115
#13 Korde et al.;
JAMA Oncol. 2015.116
Number of patients
609
185
100
162
93
31
260
50
170
39
133
103
45
Method used for MRD assessment
MFC
MFC
MFC
MFC
MFC
MFC
MFC
MFC and ASO-RQ-PCR
ASO RQ- PCR; MFC
PCR
MFC and NGS
NGS
MFC, NGS, FGD-PET/CT
Study question
PFS and OS in MRD– pts
PFS and OS in post-transplant sCR patients with HR cytogenetic MM
Toxicity, safety, PFS and OS of
VTD + HD melphalan
Monitor MRD in transplant-ineligible pts
VTD and VTCD induction in NDMM
VRD induction and consolidation for ASCT pts
VMP vs. VTP as induction
Consolidation with ASCT or CRD plus R maintenance
→ MRD
Applicability, sensitivity and prognostic value of
ASO RQ-PCR
MRD kinetics’ impact on survival
Prognostic value of MRD in pts with VGPR after front-line therapy
Safety, OS/PFS and MRD
Tolerability and impact on MRD
negativity
Patient cohorts
NDMM
NDMM
NDMM and pre-treated
NDMM elderly
Untreated MM, elderly
Untreated MM,
<65 years
NMDD, >65 years
NDMM
NDMM with and without
ASCT
NDMM with ASCT
NDMM
≥2 treatment lines
NDMM and HR SMM
Time point of MRD assessment
9 months after treatment
3 months post-ASCT
6 months post-ASCT
At ID after 9,18 cycles
At baseline and at suspected CR
ID + pre-ASCT, post-ASCT, post-consolidation, end of treatment
6 cycles of induction
After 3 and 6 courses of maintenance and then every
6 months till PD
ID and after treatment
ID, study entry, after 2 cycles
CTD, end of treatment, every 6 months until PD
After induction for elderly, after ASCT for
<65 years
PtsinCRor better after treatment
ID, achievement of CR and/or completion of cycles 8, 20 and 32, end of treatment
Results
MRD– prolonged PFS and OS; MRD+ in CR similar PFS
and OS to MRD+ in nCR and PR.
56% MRD– with superior OS
and PFS; del17 pts no difference
in PFS and OS between
sCR and MRD–; t(4;14) pts superior PFS and OS in MRD– pts than sCR
MRD– in 85% 6 months after transplantation, sCR in56%andCRin20%
Determines 3 MRD groups, with significant longer
PFS and OS for MRD– group
OS and PFS longer in
MRD– vs. MRD+ pts
with BM CR. Same results for MRD– in VGPR or PR group
58% in CR, 68% MRD–.
22% MRD– with longer PFS
and OS. VMP better than VTP. 70% in CR after VMP also MRD– only 45% in VTP group.
Lower MRD in ASCT vs. CRD pts. Differences between HR vs. SR and relapse vs. non-relapse pts
MRD assessed in 103 pts.; 54% MRD+ by PCR, 46% by MFC. MRD– pts had prolonged PFS
and OS
OS 72% at 8 years median FU in MRD– and 48% in MRD+
pts. PFS for MRD– 38 months and MRD+ 9 months
MRD– pts had significantly longer PFS and OS; median PFS: MRD≥10-3 27 months, 10-3-10-5 48 months;
<10-5 80 months.
29% of pts in CR are MRD–;
nCR or better pts were MRD– in 100% NDMM /92% SMM by MFC, 67%/75% by NGS and 41%/26% by FGD-PET/CT
Lesson learnt
MRD– status surpasses CR in all risk groups. MRD negativity most relevant endpoint for elderly fit pts with ASCT.
MRD status important markers for survival but differs according to cytogenetics
MRD and sCR excellent markers for PFS and OS
MRD is a relevant prognostic factor in elderly and MRD status correlates with OS and PFS
MRD surpasses conventional SFLC and BM CR
None of the MRD– group relapsed during a FU of 39
months
MRD surpasses CR and is a prognostic factor for OS and PFS
MRD identifies a low-risk group, response independently, better characterizes activity
of treatment.
ASO RQ-PCR less applicable than MFC but powerful to assess treatment efficacy and risk stratification
Long-term MRD monitoring is useful and maintenance therapy ensures responses
MRD surpasses CR and depth of MRD level showed significant
differences in pts with CR
MRD surpasses CR
High rates of MRD negativity with longer PFS in NDMM/HR SMM
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continued from the previous page
N. Reference
#14 Zagmani et al.; Clin Cancer
Res 2015.92
#15 Patriarca et al., Biol Blood Marrow
117 Transplant 2015.
#16 Lapa et al.; Oncotarget 2014.118
Number of patients
76
54
37
Method used for MRD assessment
FGD-PET/CT
FGD-PET/CT
FGD-PET/CT
Study question
Role of FGD-PET/CT on PFS and OS
Prognostic significance of PET/CT
Prognostic
value of FGD-PET/CT
Patients cohort
NDMM
AlloSCT pts
Pretreated, and progression after SCT
Time points of MRD assessment
Baseline, during post-treatment FU, PD
Before and/or within 6 months after alloSCT.
At relapse, after treatment
Results
PET-negativity post-treatment in 70%, CR in only 53%.
PET-negativity influenced PFS and OS favorably.
Persistence of EMD at transplantation → poor PFS. EMD and <CR or VGPR after alloSCT →shorter PFS/OS. PET CR pts prolonged PFS/OS.
Absence of foci positive factor
for PFS/OS. EMD and intense uptake associated with
shorter PFS/OS. 30% of pts' management changed after PET/CT
Lesson learnt
PET-CT more careful evaluation of CR. PET-negativity independent predictor of prolonged PFS/OS PET/CT imaging significantly associated with outcome.
Prognostic value of PET/CT in post-SCT relapse patients important and significant impact on
pt management
AlloSCT: allogenic stem cell transplantation; ASCT: autologous stem cell transplantation; ASO RQ-PCR: allele-specific oligonucleotide real-time quantitative polymerase chain reaction; BM: bone marrow; CR: complete remission; CRD: cyclophosphamide, lenalidomide, dexamethasone; d: day; EMD: extramedullary disease; FGD-PET/CT: fluorodeoxyglucose positron emission tomography- computed tomography; FU: follow-up; HD: high dose; HR: high risk; ID: initial diagnosis; MFC: multiparameter flow cytometry; MM: multiple myeloma; MRD: minimal residual disease; nCR: near- complete remission; NGS: next generation sequencing; NDMM: newly diagnosed multiple myeloma; OS: overall survival; PCR: polymerase chain reaction; PD: progressive disease; PFS: progression freesurvival;PR: partialremission;pts:patients;R: lenalidomide;sCR:stringentcompleteremission;SCT:stemcelltransplantation;SFCL:serumfreelightchain;SMM:smoulderingmultiplemyelo- ma; SR: standard risk; TTP: time to tumor progression; VGPR: very good partial remission; VMP: bortezomib, melphalan, prednisone; VRD: bortezomib, lenalidomide, dexamethasone; vs.: versus; VTCD: bortezomib, thalidomide, cyclophosphamide, dexamethasone;VTD: bortezomib, thalidomide, dexamethasone;VTP: bortezomib, thalidomide, prednisone.
between the two tests was low, progression-free survival was better in patients who were negative according to both techniques compared to those who were positive by PET and/or flow cytometry (3-year progression-free sur- vival, 86.8% versus 52.9%), indicating that both tech- niques are complementary. A major advantage of PET/CT is its capacity to assess MRD outside the BM; its disadvan- tages are high cost and the lack of reimbursement in cer- tain countries, insufficient standardization and reduced tracer uptake in some MM patients. Evaluation via PET/CT has been incorporated into the new IMWG MRD criteria.77 In the future, the increased capabilities of diffu- sion weighted MRI to detect small lesions and diffuse infiltration may offer advantages that merit prospective evaluation in MRD assessment studies.50
In addition, recent studies have demonstrated that cir- culating DNA fragments carrying tumor-specific sequence alterations can be detected and quantified in the blood of patients with solid tumors.93,94 In MM, various studies have provided evidence that - much like in solid tumors - MM-specific alterations (VDJ rearrangements or somatic genomic alterations) can also be identified and tracked in cell-free DNA circulating in blood.95,96
European Myeloma Network recommendations:
Response assessment is an essential part of myeloma manage- ment. Patients under treatment should be evaluated before the initi- ation of each cycle and according to international guidelines. Minimal residual disease testing is not currently recommended in routine follow-up of patients but is likely to be incorporated in stan- dard response/progression evaluation soon. Valid options for the assessment of minimal residual disease are based on bone marrow cells (next-generation flow cytometry) or molecular analysis (next-
generation sequencing), often also combined with an imaging-based evaluation. These methods require appropriate expertise.
Conclusion
While novel agents have certainly improved the out- comes of patients with myeloma, prompt diagnosis and close follow-up of MM patients remain highly relevant and contribute to better survival. In most cases, the diag- nosis of MM is straightforward, being based on biological and radiological evidence when evocative clinical signs are present. During response assessment, the evaluation of MRD will become increasingly important and, within the next few years, will guide treatment choices in clinical trials and possibly also outside trial scenarios. International efforts are needed to standardize the differ- ent techniques that can be used to evaluate MRD. Guidelines on appropriate follow-up and patient-tailored monitoring have been updated in this EMN consensus paper and should help to improve the outcome and prog- nosis of our patients.
Acknowledgments
The authors thank distinguished IMWG, EMN, DSMM and GMMG experts for their advice and recommendations that have helped us to improve this paper. This work was supported by the Deutsche Krebshilfe (grants 1095969 and 111424 to ME), the Foundation against Cancer, the Fonds National de la Recherche Scientifique and the Fonds d'Investissement de Recherche Scientifique (FIRS) du CHU de Liège (grants to JC), the NIHR Imperial Biomedical Research Centre and the Cancer Research UK Imperial Centre (grants to HWA).
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]]></page><page Index="45" isMAC="true"><![CDATA[Hematopoiesis
Alas1 is essential for neutrophil maturation in zebrafish
Ferrata Storti Foundation
Junwei Lian,1 Jiakui Chen,1 Kun Wang,1 Lingfeng Zhao,1 Ping Meng,1
Liting Yang,1 Jiayi Wei,1 Ning Ma,1 Jin Xu,2 Wenqing Zhang2 and Yiyue Zhang1,2
1Key Laboratory of Zebrafish Modeling and Drug Screening for Human Diseases of Guangdong Higher Education Institutes, Department of Developmental Biology, School of Basic Medical Sciences, Southern Medical University and 2Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou, P.R. China
Haematologica 2018 Volume 103(11):1785-1795
ABSTRACT
Neutrophils play essential roles in innate immunity and are the first responders to kill foreign micro-organisms, a function that partial- ly depends on their granule content. The complicated regulatory network of neutrophil development and maturation remains largely unknown. Here we utilized neutrophil-deficient zebrafish to identify a novel role of Alas1, a heme biosynthesis pathway enzyme, in neutrophil development. We showed that Alas1-deficient zebrafish exhibited prop- er neutrophil initiation, but further neutrophil maturation was blocked due to heme deficiency, with lipid storage and granule formation defi- ciencies, and loss of heme-dependent granule protein activities. Consequently, Alas1-deficient zebrafish showed impaired bactericidal ability and augmented inflammatory responses when challenged with Escherichia coli. These findings demonstrate the important role of Alas1 in regulating neutrophil maturation and physiological function through the heme. Our study provides an in vivo model of Alas1 deficiency and may be useful to evaluate the progression of heme-related disorders in order to facilitate the development of drugs and treatment strategies for these diseases.
Introduction
Neutrophils are the most abundant leukocytes in the circulation and the first responders to sites of infection, where they attack pathogens by phagocytosis, degranulation, and by generating neutrophil extracellular traps.1,2 Neutrophil devel- opment is highly conserved in vertebrates, making zebrafish a suitable model for investigation. Neutrophils are derived from granulocyte-monocyte progenitors, and undergo determination and differentiation from myeloblasts to mature neu- trophils.1,3 During neutrophil differentiation and maturation, neutrophil granules are formed and assembled.1 Anti-microbial proteins are thought to be the major constituents of neutrophil granules, and they play important roles in neutrophil diapedesis, chemotaxis, and the phagocytosis of micro-organisms.1,4
Several transcription factors have been reported to be involved in neutrophil development and physiological function in mammals, including SPI.1/PU1 and C/EBP-ε.3 A recent study of embryonic myelopoiesis revealed that the Pu.1-Runx1 regulatory loop controlled embryonic myeloid cell fate in zebrafish.5,6 We previous- ly demonstrated that c-Myb and Cebp1 co-operatively acted in parallel to govern neutrophil maturation.7 In addition to these transcription factors, zebrafish defi- cient for the neutrophil granule protein myeloperoxidase (Mpx) or the neutrophil- specific marker nephrosin (Npsn) have altered neutrophil maturation and inflam- matory responses to fungal and bacterial infection, respectively.8,9 Nevertheless, the complicated regulatory network of neutrophil maturation, as well as the impact on physiological function remain poorly understood.
Heme (iron protoporphyrin IX) functions as a prosthetic group on various pro- teins, so-called hemoproteins, such as hemoglobin, myoglobin, cytochromes, cata- lases, and peroxidases.10 Hemoproteins are involved in diverse biological functions, including oxygen transport, energy metabolism, and drug biotransformation.11 Moreover, heme also plays important roles in the regulation of transcription,12-14
Correspondence:
yiyue@smu.edu.cn or mczhangyy@scut.edu.cn or mczhangwq@scut.edu.cn
Received: March 27, 2018. Accepted: June 27, 2018. Pre-published: June 28, 2018
doi:10.3324/haematol.2018.194316
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1785
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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translation,15,16 protein degradation,17,18 and microRNA pro- cessing.19 The accumulation of excess heme and its precur- sors in tissues can cause oxidative damage via the genera- tion of reactive oxygen species.11 Thus, cellular heme homeostasis must be tightly controlled.
The 5-aminolevulinate synthase 1 (ALAS1) is a mito- chondrial enzyme that catalyzes the condensation of glycine and succinyl-CoA, forming 5-aminolevulinic acid. ALAS1 is the first and rate-limiting enzyme of the heme biosynthetic pathway, which is conserved from lower to higher organisms.20 ALAS1 (also called hepatic ALAS or non-specific ALAS) is ubiquitously expressed throughout the body, whereas another isoform, ALAS2 (also called ALAS-E), is predominantly expressed in erythroid cells, to meet the need of the large amounts of heme required for hemoglobin synthesis.11 It has been reported that human ALAS2 mutations cause X-linked sideroblastic anemia;21 ALAS2-deficient mice and zebrafish also display severe anemia,22,23 revealing the major contribution of ALAS2 to erythroid heme biosynthesis, and hence how it is essential to erythroid differentiation. In contrast to ALAS2, there are no reported human diseases directly caused by muta- tions in ALAS1. In mice, Alas1-null embryos are lethal by embryonic day 8.5 (E8.5),24 thus, the in vivo physiological role of ALAS1 is unclear. Using GFP knock-in mice (Alas1+/GFP), ALAS1 was found to be highly expressed in the liver, exocrine, endocrine glands, and myeloid cells, where large amounts of heme are required to meet the needs of tissue-specific hemoproteins, such as MPO, NADPH oxi- dase, and CYP450.24 Notably, Alas1 is also expressed high- er in neutrophils than macrophages,24 suggesting cell-spe- cific roles in neutrophils. However, the function of ALAS1 in neutrophils is still unknown.
Taking advantage of their transparent body, we can observe neutrophil morphology to trace neutrophil behav- iors in live zebrafish. Zebrafish is an ideal model for study- ing neutrophil biology.25,26 Here we report a novel role of Alas1 in regulating neutrophil development using a neu- trophil lineage-deficient mutant zebrafish line (previously named smu350) that was isolated from our ENU mutant collection.27 We demonstrated that alas1 was the causative gene for the mutant and revealed that alas1 was essential for neutrophil development and physiological function.
Methods
Fish maintenance
Zebrafish were raised and maintained under standard condi-
tions.28 Embryos were maintained in egg water containing 0.2 mM
N-phenylthiourea (Sigma-Aldrich, St. Louis, MO, USA) to prevent
pigment formation. All work involving zebrafish was approved by
Southern Medical University Animal Ethics Committee. The fol-
lowing strains were used: AB, Tg(lyz:DsRed),29 Tg(gata1:DsRed), vltm651/+ and alas1smu350/+.
Treatment with succinylacetone
Succinylacetone (SA) (Sigma-Aldrich, St. Louis, MO, USA) was dissolved in egg water. Zebrafish embryos were placed in culture dishes containing 1 mM SA at 5 hours (h) post fertilization (hpf) till the desired stage.
Bacterial infection
The eGFP-labeled E. coli strain XL10 was cultured in LB broth with 50 mg mL-1 ampicillin at 37°C until reaching an optical den-
sity at 600 nm between 0.5-0.8. Bacteria were washed with sterile phosphate buffered saline (PBS) three times, harvested by centrifu- gation at 5000 x g for 5 minutes (min) and resuspended in sterile PBS. The working concentration of E. coli was 2x109 mL-1, and approximately 0.5 nL of bacterial suspension was subcutaneously injected over a somite into 3-day-post-fertilization (dpf) embryos with 0.02% tricaine using a PLI-100A Pico-Injector (Warner Instruments, Hamden, CT, USA) as previously described.26,30 For bacterial colony forming assays, every injected embryo was washed with sterile PBS three times, and then homogenized in 200 mL of sterile PBS at the desired time points. Then, 10 mL of homogenate was plated on LB medium with ampicillin and cul- tured at 37°C overnight. The results are the average of two sepa- rate experiments.
Statistical analysis
Data were recorded and analyzed using GraphPad Prism 7 and IBM SPSS v.23. Two-tailed Student t-test and Mann-Whitney U test were used for comparisons between parametric and non-para- metric data, respectively. One-way analysis of variance (with Bonferroni or Dunnett T3 post-test adjustment) was used for para- metric data to make multi-comparisons. Differences were consid- ered significant at P<0.05. Data are expressed as the mean±Standard Deviation (SD).
Results
Neutrophil deficiency in smu350 mutant zebrafish
To identify new regulators of neutrophil development, we conducted a genetic screen for neutrophil-deficient zebrafish mutants using Sudan black B (SB) staining. From this screen, we isolated the neutrophil-deficient smu350 mutant, which lacked the SB signal as early as 36 hpf (Figure 1A). The early loss of the SB signal in smu350 mutants suggested defects in embryonic neutrophils, as SB+ cells represent embryonic neutrophils that are initiat- ing from embryonic myelopoietic tissue.31 Because myeloid progenitors that are derived from rostral blood islands will progress to neutrophils during embryonic myelopoiesis, we first determined if there were defects in the formation of myeloid progenitors. The results showed that pu.1 expression at 22 hpf was normal (Figure 1B), sug- gesting the presence of myeloid progenitors in smu350 mutants. Therefore, we speculated that the loss of the SB signal was due to defects in neutrophil maturation. To test this possibility, we detected the transcript and protein activity of the myeloid-specific peroxidase (Mpx), which is an abundant granule protein in neutrophils.2 Whole- mount in situ hybridization (WISH) showed that mpx mRNA expression was intact (Figure 1C), suggesting the presence of neutrophils in smu350 mutants. To further examine Mpx enzyme activity, diaminobenzidine (DAB, a peroxidase substrate) staining was performed. The results showed that while the signal in the yolk sac (representing hemoglobin peroxidase activity32) was present, signals rep- resenting neutrophil peroxidase activity were absent in smu350 mutants (Figure 1D), suggesting that Mpx lost its catalytic activity. As neutrophil granules are abundant with Mpx, we directly monitored neutrophil granule mor- phology via video-enhanced differential interference con- trast (VE-DIC) analyses of live embryos. The results showed that neutrophils from siblings (alas1smu350/+ and alas1+/+ embryos from a heterozygous alas1smu350/+ in-cross) had abundant visible and highly mobilized granules, while neutrophils from smu350 mutants lacked such granules
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(Figure 1E and Online Supplementary Appendix, Movies 1 and 2). These results suggest that neutrophil maturation is defective in smu350 mutants.
The alas1 mutation was responsible for neutrophil defects of smu350 mutant
Positional cloning was then performed to identify the causative gene in smu350 mutants. Initial mapping with bulk segregation analysis located the mutated site to link-
age group 11 (data not shown), then fine mapping placed the mutated gene within a region between two simple sequence length polymorphism markers, CU633745-M and CU929297-M, from the Massachusetts General Hospital panel (Figure 2A). The mutation was then mapped to a 100-kb region partly covered by two bacterial artificial chromosomes (BACs) (Figure 2A). There were 9 predicted genes in this region (Figure 2A). By sequencing, we found a T-to-A mutation in alas1 intron 7 next to the
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Figure 1. Neutrophil deficiency in smu350 mutants. (A) The Sudan black B (SB) signal was totally absent in smu350 mutants. SB staining in siblings (left) and smu350 mutants (right) at 3 days post fertilization (dpf). The boxed regions are magnified in the lower right-hand corner. (B) Whole-mount in situ hybridization (WISH) of pu.1 expression in siblings (left) and smu350 mutants (right) at 22 hours post fertilization (hpf). (C) WISH of mpx expression in siblings (left) and smu350 mutants (right) at 2 dpf. (D) DAB staining in siblings (left) and smu350 mutants (right) at 2 dpf. Signal points represent- ing neutrophil peroxidase activity (black arrowheads) were absent in smu350 mutants. Red arrowheads indicate the hemoglobin signal. The boxed regions are magnified in the lower right-hand corner. (E) Neutrophil granules were absent in smu350 mutants. In vivo imaging of neutrophils in 2-dpf Tg(lyz:DsRed);smu350 embryos by VE-DIC microscopy. Neutrophils of siblings had abundant visible and highly mobilized granules (29 of 31 embryos), while neutrophils of smu350 mutants lacked granules (12 of 12 embryos). White arrowheads indicate neutrophil granules. (Left) Bright-field DIC image; (right) an overlay of bright-field DIC and fluorescent images. See also Online Supplementary Appendix, Movies 1 and 2. (F) Quantifications of SB+ cells in the poste- rior blood island (PBI), pu.1+ cells (B), mpx+ cells in the PBI (C), and DAB+ cells in the PBI (D). Mean±Standard Deviation (SD), n>15; Student t-test: ****P<0.0001. ns: not sig- nificant; nd: not detectable. Scale bars: 200 mm (A-D) and 5 mm (E).
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Figure 2. The alas1 gene was mutated in smu350 mutants. (A) The mutated gene in smu350 mutants mapped to a 100-kb region between two simple sequence length polymorphism markers, CU633745-M (two recombinants in 6160 smu350 mutant embryos) and CU929297-M (three recombinants in 6160 smu350 mutant embryos), on linkage group 11. The 100-kb region, partly covered by two bacterial artificial chromosomes (BACs) (CU633745 and CU929297), contains 9 predicted genes. (B) The structure of the zebrafish alas1 gene. The red asterisk indicates a T-to-A mutation in intron 7 of alas1 in smu350 mutants. The black arrow indicates the position of the CRISPR/Cas9 target in alas1. Numbers of constitutive exons are indicated. (C) Agarose gel electrophoresis of alas1 RT-qPCR amplification prod- ucts from 3-day post fertilization (dpf) wild-type zebrafish, siblings, and smu350 mutants. Four major products (indicated by black arrows) were identified in smu350 mutants compared with wild-type transcripts (461 bp). The actb2 was used as an internal control. (D) The mutated alas1 transcripts and their predicted translation products in smu350 mutants. The blue arrow indicates the position of the transcriptional start site. Black arrows indicate the RT-qPCR primers used in (C), and black boxes indicate the wild-type peptides. Red boxes indicate the incorrect peptides generated by the altered splicing. Pink boxes indicate the pre-sequence domain (pfam09029). Green boxes indicate the aspartate aminotransferase superfamily domain (fold type I) of pyridoxal phosphate-dependent enzymes (cl18945). Boxes with zigzag edges indicate truncated regions. Blue boxes with white numbers indicate exons. Black and red numbers denote distances to the start codon in wild- type and mutants, respectively. (E) alas1 expression was up-regulated in smu350 mutants. Relative expression of alas1 transcript assessed by RT-qPCR in smu350 mutants (gray column) and wild-type (black column) at 2, 3, 5, and 7 dpf [mean±Standard Deviation (SD); n=10 in each group, performed in triplicate]. Statistical significance was determined using Student t-test, ***P<0.001. (F) Alas1 protein was absent in smu350 mutants. Alas1 protein expression in the whole fish body assessed by western blotting at 5 dpf. GAPDH was used as the loading control.
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exon-intron boundary in smu350 mutants (Figure 2B), which is likely to be a splicing mutation. By amplifying alas1 cDNA from smu350 mutants, we found at least four unexpected alas1 transcripts (Figure 2C), which were con- firmed by sequencing analysis following TA cloning. These unexpected transcripts were predicted to produce truncated Alas1 proteins or in-frame-insertion Alas1 pro- teins, all of which would interrupt the enzyme activity domain of Alas1 (Figure 2D). Expression analyses by reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) showed elevated alas1 mRNA expression in smu350 mutants compared with siblings throughout development (Figure 2E). However, we found that neither the wild-type form nor the abnormal variants of Alas1 protein were present in smu350 mutants, as deter- mined by western blotting (Figure 2F). These data strongly suggest that this alas1 mutation is responsible for the smu350 mutant (hereafter named alas1smu350/smu350) phenotype and that the alas1smu350/smu350 mutant is a loss-of-function mutant.
To confirm that the alas1smu350/smu350 mutant phenotype was indeed caused by the alas1 mutation, we used CRISPR/Cas9 to create alas1-knock-out mutants. A homozygous alas1 mutant (alas1Δ2/Δ2) with a 2-bp deletion
within exon 7 of alas1 was obtained, and the mutation resulted in a frameshift of the alas1 product, causing a loss of Alas1 protein in the alas1Δ2/Δ2 mutant (Figure 3A and B). Similar to the alas1smu350/smu350 mutant, the alas1Δ2/Δ2 homozy- gous mutant and the alas1smu350/Δ2 bi-allelic mutant also showed loss of SB staining (Figure 3C and D), indicating that alas1 is indeed the causative gene for the altered neu- trophil development phenotype.
The alas1 mutation caused heme deficiency
ALAS1 is the first and rate-limiting enzyme for heme biosynthesis, and heme negatively regulates ALAS1 expression through a feedback mechanism.10 As the Alas1 protein was undetectable (Figure 2F), we postulated that the heme levels of alas1smu350/smu350 mutants might be decreased. To test this hypothesis, we measured heme levels in alas1smu350/smu350 mutants using a fluorescence heme assay. Surprisingly, total heme levels of alas1smu350/smu350
mutants were abnormally elevated (Figure 4A).
As erythroid tissue is the major site of heme production in the body and depends on the isozyme Alas2,33 we then checked if this elevated heme was derived from erythro- cytes. We first compared the erythrocyte numbers between 4-dpf alas1smu350/smu350 mutants and their siblings and
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Figure 3. The alas1 was the causative gene of the smu350 mutant. (A) Sequencing analysis revealed a 2-bp deletion within exon 7 of alas1 in CRISPR/Cas9 gen- erated alas1Δ2/Δ2 mutants. Uppercase sequences highlighted blue indicate exons; sequences in lowercase indicate introns. Sequences underlined in red indicate the CRISPR/Cas9 target in alas1. The red asterisk indicates the smu350 mutation site. Black boxes indicate the wild-type peptides, and the red box indicates the incor- rect peptide generated by the altered splicing. The pink box indicates the pre-sequence domain (pfam09029). The green box indicates the aspartate aminotrans- ferase superfamily (fold type I) domain of pyridoxal phosphate-dependent enzymes (cl18945). The box with zigzag edges indicates the truncated region. Black and red numbers denote distances to the start codon in wild type and mutants, respectively. (B) Alas1 protein was absent in alas1Δ2/Δ2 mutants. Examination of Alas1 protein expression in the whole fish body by western blotting at 5 days post fertilization (dpf). GAPDH was used as the loading control. (C) The Sudan black B (SB) signal was absent in alas1Δ2/Δ2 mutants. SB staining in siblings (upper) and alas1Δ2/Δ2 mutants (lower) at 3 dpf. Boxed regions are magnified in the lower right-hand corner. Scale bars: 200 mm. (D) SB signal was absent in alas1smu350/Δ2 mutants. SB staining in siblings (upper) and alas1smu350/Δ2 mutants (lower) at 3 dpf. Boxed regions are magnified in the lower right-hand corner. Scale bars: 200 mm.
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Figure 4. The alas1 mutation caused heme deficiency. (A) Whole fish heme levels of alas1smu350/smu350 mutants were significantly higher than those of siblings. Relative whole fish heme levels in siblings (circles) and alas1smu350/smu350 mutants (squares) at 4 days post fertilization (dpf). Lines show mean±Standard Deviation (SD), 6 indi- vidual data points in each group, each data point was based on 3 measurements for 5 embryos; Student t-test, ***P<0.001. The relative heme level was normalized to per-fish level. (B) No significant differences in erythrocyte numbers between siblings and alas1smu350/smu350 mutants. gata1:DsRed+ erythrocyte numbers were meas- ured by flow cytometric analysis using 4-dpf self-progeny of Tg(gata1:DsRed)+/+;alas1smu350/+ transgenic line. Numbers were normalized to per-fish level in siblings (black column) and alas1smu350/smu350 mutants (gray column). Mean±SD; performed in triplicate; Student t-test, ns: not significant. (C) Cellular heme levels of alas1smu350/smu350 mutant neutrophils were decreased compared with those of siblings. Relative cellular heme levels in sorted neutrophils (lyz:DsRed+ cells) of siblings (black column) and alas1smu350/smu350 mutants (gray column) at 4 dpf. Mean±SD; performed at least in triplicate; Student t-test, *P<0.05. The relative heme level was normalized to per-cell level. (D) Cellular heme levels of alas1smu350/smu350 mutant erythrocytes were increased compared with those of siblings. Relative cellular heme levels in sorted erythrocytes (gata1:DsRed+ cells) of siblings (black column) and alas1smu350/smu350 mutants (gray column) at 4 dpf. Mean±SD; performed in triplicate; Student t-test, *P<0.05. The relative heme level was normalized to per-cell level. (E) Aberrant whole fish heme increment was dampened in alas1smu350/smu350 mutants without erythrocytes. Relative whole fish heme levels in 4-dpf alas1;gata1a siblings, alas1 single mutants, gata1a single mutants, and alas1;gata1a double mutants from alas1smu350/+;gata1am651/+ in-cross. Lines show mean±SD, 4 individual data points in each group, each data point was based on 3 measurements for 5 embryos; one-way ANOVA followed by Dunnett T3 post test, *P<0.05. ns: not significant; nd: not detectable. The relative heme level was normalized to per-fish level. (F) Relative expressions of alas2 and genes related to heme degradation and transport. The assay was performed by RT-qPCR in 4-dpf siblings (black column) and alas1smu350/smu350 mutants (gray column). Mean±SD; n=8 in each group, performed in triplicate. Statistical significance was determined using Student t-test; ****P<0.0001, **P<0.01, *P<0.05. ns: not significant.
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found no significant differences (Figure 4B), indicating the elevated whole heme in mutants was not due to increased erythrocyte numbers. We next isolated neutrophils and erythrocytes of alas1smu350/smu350 mutants and their siblings by fluorescence-activated cell sorting (FACS) using 4-dpf self- progeny of Tg(lyz:DsRed)+/+;alas1smu350/+ and Tg(gata1:DsRed)+/+;alas1smu350/+ transgenic lines, respectively, to directly measure heme levels in the two cell types. By comparing relative heme levels in neutrophils or erythro- cytes between alas1smu350/smu350 mutants and their siblings, we found that heme was less abundant in neutrophils of alas1smu350/smu350 mutants than that of siblings (Figure 4C), while in erythrocytes, heme was more accumulated in erythrocytes of mutants (Figure 4D). These data indicate that alas1 mutation results in heme insufficiency in neu- trophils but abnormal accumulation in erythrocytes. To further confirm that the elevated heme of the whole body was derived from erythrocytes in alas1smu350/smu350 mutants, we introduced vltm651,34 (a gata1a mutant with a 'bloodless' phenotype having no erythrocytes but intact white blood cells) into the smu350 mutant background to eliminate the effect of erythrocytes. As expected, whole fish heme lev- els of alas1smu350/smu350 mutants were almost undetectable compared with those of siblings in the gata1a mutant background (Figure 4E). These data indicate that the aber- rant heme accumulation of the whole body is indeed derived from erythrocytes in alas1smu350/smu350 mutants.
Alas2, the other isozyme of Alas1, is essential for the heme biosynthesis in erythrocytes and predominantly expressed in erythrocytes.10 To test whether the erythroid heme increment resulted from the elevated alas2 expres-
sion, we checked alas2 expression in alas1smu350/smu350 mutants. The data showed that alas2 was not altered com- pared with that in siblings (Figure 4F), suggesting that the erythroid heme accumulation was not due to the compen- satory of alas2, at least at the transcription level. Since heme content is tightly controlled by the homeostasis of heme biosynthesis, degradation, and transport path- ways,35 we then detected the expression of heme oxyge- nase enzymes (hmox1a and hmox2a),10,36 which encode the rate-limiting enzymes for heme degradation. The results showed that both gene expressions were down-regulated in alas1smu350/smu350 mutants (Figure 4F), suggesting the impaired heme degradation in the absence of alas1. The results suggest that the dysregulation of heme biosynthe- sis affects the heme degradation in alas1smu350/smu350 mutants, and the elevated heme might be attributed to the reduced heme degradation. The elevated heme in erythrocytes could not be utilized by heme-deficient neutrophils in alas1 mutants, which is likely due to the fact that the syn- thesized heme in erythrocytes could not be transported to neutrophils. To test this hypothesis, we further detected the expressions of genes encoding heme transporters. Flvcr1a is reported to export heme out of the cell as a plas- ma membrane heme exporter.37 Hpx, a high-affinity heme-binding protein, is reported to interact with FLVCR in heme transfer.35 HRG-1 is reported to deliver heme to the cytosol,38 which is encoded by slc48a1a (heme trans- porter hrg1-B) and slc48a1b (heme transporter hrg1-A) in zebrafish. MRP-5/ABCC5 is reported to reside on the plas- ma membrane and endosomal compartments and regulate the export of cytosolic heme.39 RT-qPCR showed that the
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Figure 5. Heme was essential for neutrophil maturation. (A) Whole fish heme levels of succinylacetone (SA)-treated embryos were significantly decreased than those of untreated control. Relative whole fish heme levels in untreated control (circles) and SA-treated embryos (triangles) at 2 days post treatment (dpt). Lines show Mean±Standard Deviation (SD), 6 individual data points in each group, each data point was based on 3 measurements for 5 embryos; Student t-test: ***P<0.001. The relative heme level was normalized to per-fish level. (B) The o-Dianisidine signal was totally absent in SA-treated embryos. o-Dianisidine staining in untreated wild-type (left, 11 of 11 embryos) and SA-treated (right, 10 of 10 embryos) embryos at 2 dpt. (C) The Sudan black B (SB) signal was totally absent in SA-treated embryos. SB staining in untreated wild-type (left, 20 of 20 embryos) and SA-treated (right, 17 of 17 embryos) embryos at 2 dpt. Black arrowheads indicate the neu- trophil signals. The boxed regions are magnified in the lower right-hand corner. (D) The DAB signal was totally absent in SA-treated embryos. DAB staining in untreat- ed wild-type (left, 18 of 18 embryos) and SA-treated (right, 14 of 14 embryos) embryos at 2 dpt. Black arrowheads indicate the neutrophil peroxidase signals. The boxed regions are magnified in the lower right-hand corner. (E) WISH of lyz expression in untreated wild-type (left, 21 of 21 embryos) and SA-treated (right, 25 of 25 embryos) embryos at 2 dpt. (F) WISH of mpx expression in untreated wild-type (left, 23 of 23 embryos) and SA-treated (right, 15 of 15 embryos) embryos at 2 dpt. Scale bars: 200 mm (B-F).
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Figure 6. alas1 deficiency caused impaired host immunity against E. coli infection. (A) Arrowhead indicates the site of bacteria injection. The imaged region is boxed. (B-E) The in vivo behavior of neutrophils against E. coli was monitored by confocal microscopy. eGFP+ E. coli were subcutaneously injected over one somite into 3-day post fertilization (dpf) sibling (upper panels) and alas1smu350/smu350 mutant (lower panels) larva of the Tg(lyz:DsRed) background. Neutrophil behavior was analyzed through live imaging at 0.5 hours post injection (hpi) (B), 3 hpi (C), 5 hpi (D), and 24 hpi (E). All images are maximum-intensity projections from 25 steps x 2 mm. Scale bars: 50 mm. (F) Bacterial burden of embryos injected with E. coli. Significantly more bacterial cells were detected in alas1smu350/smu350 mutants (gray col- umn) compared with siblings (black column) at 5 and 24 hpi. Mean±Standard Deviation (SD), n>10 in each group; Mann-Whitney U test: ****P<0.0001, **P<0.01, ns: not significant. (G) Quantification of recruited DsRed+ neutrophils at infection sites in live embryos injected with E. coli. Significantly more neutrophils were observed at the infection sites of alas1smu350/smu350 mutants (gray column) compared with siblings (black column) at 24 hpi. Mean±SD; n>19 in each group; Student t-test: ****P<0.0001. nd: not detectable, ns: not significant. (H) Relative il1b expression assessed by RT-qPCR. il1b expression was up-regulated in alas1smu350/smu350 mutants (gray column) compared with siblings (black column) at 3, 5, and 24 hpi. Mean±SD; n=4 in each group, performed in triplicate. Expression levels were adjusted for trauma [phosphate buffered saline (PBS) injection only]. Statistical significance was determined using Student t-test: **P<0.01, *P<0.05. ns: not sig- nificant. (I) Relative cxcl8a expression assessed by RT-qPCR. cxcl8a expression was up-regulated in alas1smu350/smu350 mutants (gray column) compared with siblings (black column) at 3 and 5 hpi. Mean±SD; n=4 in each group, performed in triplicate. Expression levels were adjusted for trauma (PBS injection only). Statistical sig- nificance was determined using Student t-test: **P<0.01. ns: not significant.
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expressions of these heme transporter genes were decreased in alas1smu350/smu350 mutants compared with their siblings (Figure 4F), probably due to the feedback regula- tion of aberrant heme contents in alas1smu350/smu350 mutants. Thus, the heme transport deficiency might be one of the reasons that the elevated erythroid heme could not be uti- lized by neutrophils in alas1smu350/smu350 mutants.
Heme was essential for neutrophil maturation
To confirm whether the neutrophil maturation defects were caused by inadequate heme levels, we next treated wild-type zebrafish embryos with SA, an inhibitor of δ-aminolevulinic acid dehydratase, which catalyzes the second step in heme biosynthesis pathway,40 to inhibit the endogenous heme levels. Total heme levels of SA-treated embryos were significantly decreased compared with untreated control embryos (Figure 5A). As reported, the o-Dianisidine staining signal was decreased as hemoglobin synthesis is inhibited without heme (Figure 5B).23,40 When we monitored the neutrophil phenotypes, we found that SA-treated embryos showed loss of SB and DAB staining but intact lyz and mpx expression (Figure 5C-F), which mimics the neutrophil maturation defects in Alas1-defi- cient mutants. These data suggest that the neutrophil defects in alas1smu350/smu350 mutant are indeed caused by inad- equate effective heme in neutrophils.
Neutrophil bactericidal defects in alas1smu350/smu350 mutants
Neutrophils play key roles in various functions, includ- ing action against certain infections, largely depending on granule proteins.1 The neutrophil granule defects suggest that the anti-infection ability of alas1smu350/smu350 mutant neu- trophils may be attenuated. To detect whether alas1 defi- ciency affected neutrophil bactericidal function, alas1smu350/smu350 mutants were challenged with a bacterial infection.26,30 We subcutaneously injected eGFP labeled E. coli over one somite in 3-dpf Tg(lyz:DsRed);alas1smu350/+ inter- crossed embryos, in which DsRed was expressed specifi- cally in neutrophils (Figure 6A). Neutrophil behavior and immune responses were then monitored. We first moni- tored in vivo bacterial growth and detected the kinetic curves of the bacterial burden of infected embryos. In sib- ling embryos, bacteria growth was inhibited effectively in the host, as green fluorescent bacteria decreased rapidly in the infection site (Figure 6B-E). By further plating the homogenized embryos/larvae on LB medium for quantifi- cation, we found that bacterial colonies were gradually decreased from 5 h post injection (hpi) and eventually became almost absent at 24 hpi (Figure 6F), suggesting the inhibition of bacterial growth in the host. In mutant embryos, the eGFP+ bacterial load was similar to siblings within the first 3 hpi (Figure 6B and C), but fluorescent bacteria were still accumulating at 5 hpi and persisted at 24 hpi, when clearance had been completed in the siblings (Figure 6D-E). Quantification data consistently showed that the plated colony numbers from mutants were similar to those of siblings within the first 3 hpi, but the numbers were significantly higher at 5 and 24 hpi than those of the siblings (Figure 6F), suggesting antimicrobial activity was impaired in alas1smu350/smu350 mutants. We further counted the number of neutrophils recruited to the infection site. Within the first 5 hpi, alas1smu350/smu350 embryos showed sim- ilar neutrophil recruitment to sibling embryos (Figure 6B-
D, G). However, neutrophils were still accumulating at the infection site in alas1smu350/smu350 larvae at 24 hpi, when recruited neutrophils had almost completely disappeared in the siblings (Figure 6E and G), confirming the defect in neutrophil-specific antibacterial response in alas1smu350/smu350 mutants.
To gain further insight into the infection-induced inflammatory alterations, we detected the expression of inflammatory factors il1b and cxcl8a,41,42 which induce neu- trophil chemotaxis and promote immune responses. Expression analyses showed that both genes were signifi- cantly up-regulated in infected alas1smu350/smu350 mutants com- pared with siblings. The il1b and cxcl8a expressions peaked in the mutants at 5 hpi, at which point their expressions had already been down-regulated in the sib- lings (Figure 6H and I), suggesting a more dramatic inflam- matory response in alas1smu350/smu350 mutants. Taken together, these data demonstrate that alas1 deficiency causes impaired immune responses to bacterial infection.
Discussion
In this study, we showed a role for the heme biosynthe- sis pathway enzyme Alas1 in regulating neutrophil matu- ration and function. Neutrophils in Alas1-deficient zebrafish had heme deficiency, which led to the loss of heme-related granule protein activities, defective granule formation, and altered immune responses against patho- genic bacteria.
Here, we found that the heme dysregulation caused by the alas1 mutation led to neutrophil defects in zebrafish. Given the important role of neutrophils in immunity, it was expected that Alas1-deficient zebrafish would show impaired bactericidal ability. Inflammatory factors, such as il1b and cxcl8a,41,42 mediate neutrophil recruitment and promote immune responses. The over-elevated expression of inflammatory factors in infected alas1smu350/smu350 mutants might be explained by the ineffectiveness of killing bacte- ria, thereby leading to greater pathogen growth and stronger immune responses in the host. We also noticed that the inflammatory responses eventually subsided while the bacterial burden and recruited neutrophils were still present at 24 hpi in Alas1-deficient zebrafish, so it was likely that the inflammatory factors had been excessively depleted.
As far as we know, the regulatory genes and pathways of heme biosynthesis, degradation and transport are large- ly conserved between mammals and zebrafish in gener- al.20,23,35,36,43 Vertebrates contain two ALAS isozymes encod- ed by 2 distinct genes located on different chromosomes; ALAS2 is expressed in erythrocytes, whereas ALAS1 is ubiquitously expressed.11 By searching the integrated RNA-seq database on BloodSpot,44 we found that, in humans and mice, ALAS1 is highly expressed in myeloid cells, which is consistent with our zebrafish data and part- ly explains the importance of alas1 for neutrophils. In mice, ALAS1 is also highly expressed in the liver, exocrine, and endocrine glands, suggesting specific roles in those tis- sues.24 Accordingly, even though alas1 is ubiquitously expressed, we suspect that alas1 may play specific roles in certain tissues to meet the need of hemoproteins. It is reported that ALAS1-null mice died in utero until E8.5, with a severely retarded morphology, indicating that ALAS1 is essential for the early development of mouse embryos.24
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It is likely that because of the lethality resulting from ALAS1 deficiency, no reported human diseases directly caused by mutations in ALAS1 have been reported so far. Although the Alas1-deficient zebrafish were indistin- guishable on morphology from wild type at embryonic stages, the Alas1-deficient zebrafish are not viable past 8 dpf and showed some morphological defects from 4 dpf onwards, such as delayed disappearance of the yolk sac, abnormal liver, and failed swim bladder formation (data not shown). Thus, the specific functions of ALAS1 in differ- ent tissues and organs remain to be clarified.
Alas1-deficient zebrafish showed impaired heme levels in neutrophils but elevated heme levels in erythrocytes. It is known that in addition to mitochondrial heme synthe- sis within all cells, heme can also be transported in and out of cells from the plasma.11 Intracellular heme levels are tightly controlled through the co-ordination of heme syn- thesis, degradation, and trafficking.35 In this study, we found that the expression of alas2, encoding the other rate-limiting enzyme of heme synthesis, was not changed, while the expressions of heme degradation and trans- porter genes were down-regulated in alas1smu350/smu350 mutants. In Alas1-deficient zebrafish, cellular heme levels were unexpectedly elevated in erythrocytes, partly due to the decrease in heme degradation. The excessive heme could not be effectively used by neutrophils, probably because the heme transport was impaired. Similar to mice,24 the over-produced heme by alas2 in erythrocytes
could not compensate for the function of alas1 in zebrafish, indicating the essential roles of alas1. The feed- back mechanisms for heme homeostasis remain unclear, so future studies will be needed to elucidate the molecular mechanisms of heme metabolisms and trafficking.
Impaired heme biosynthesis or heme deficiency leads to heme-related disorders, such as anemias, acute por- phyrias, and leukemia.11 Acute intermittent porphyria is characterized by the accumulation and/or excretion of excess heme precursors.11 As Alas1 is the key enzyme in heme biosynthesis, repressing Alas1 activity by RNAi is now being used to prevent acute porphyria attacks.45,46 Thus, Alas1-deficient zebrafish may serve as an in vivo animal model for evaluating the risks of therapeutic strategies, since Alas1 deficiency causes neutrophil defects, as well as other potential defects in Alas1-abun- dant tissues. This study may also contribute to the devel- opment of new drugs or treatment strategies for heme- related diseases.
Acknowledgments
We thank Dr. Zilong Wen for sharing the Tg(gata1:DsRed) line and eGFP-labeled E. coli strain XL10.
Funding
This work was supported by the National Natural Science Foundation of China (31471378) and the Team Program of the Guangdong Natural Foundation (2014A030312002).
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23. Brownlie A, Donovan A, Pratt SJ, et al. Positional cloning of the zebrafish sauternes gene: a model for congenital sideroblastic anaemia. Nat Genet. 1998; 20(3):244-250.
24. Okano S, Zhou L, Kusaka T, et al. Indispensable function for embryogenesis, expression and regulation of the nonspecific form of the 5-aminolevulinate synthase gene in mouse. Genes Cells. 2010;15(1):77-
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26. Colucci-Guyon E, Tinevez JY, Renshaw SA, Herbomel P. Strategies of professional phagocytes in vivo: unlike macrophages, neutrophils engulf only surface-associated microbes. J Cell Sci. 2011;124(18):3053- 3059.
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33. Sadlon TJ, Dell'Oso T, Surinya KH, May BK. Regulation of erythroid 5-aminolevulinate synthase expression during erythropoiesis. Int J Biochem Cell Biol. 1999;31(10):1153- 1167.
34. Lyons SE, Lawson ND, Lei L, Bennett PE, Weinstein BM, Liu PP. A nonsense mutation in zebrafish gata1 causes the bloodless phe-
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36. Holowiecki A, O'Shields B, Jenny MJ. Spatiotemporal expression and transcrip- tional regulation of heme oxygenase and biliverdin reductase genes in zebrafish (Danio rerio) suggest novel roles during early developmental periods of heightened oxidative stress. Comp. Biochem. Physiol. C Toxicol. Pharmacol. 2017;191:138-151.
37. Mercurio S, Petrillo S, Chiabrando D, Bassi ZI, Gays D, Camporeale A, et al. The heme exporter Flvcr1 regulates expansion and dif- ferentiation of committed erythroid progen- itors by controlling intracellular heme accu- mulation. Haematologica. 2015; 100(6):720- 729.
38. Rajagopal A, Rao AU, Amigo J, Tian M, Upadhyay SK, Hall C, et al. Haem home- ostasis is regulated by the conserved and concerted functions of HRG-1 proteins. Nature. 2008;453(7198):1127-1131.
39. Korolnek T, Zhang J, Beardsley S, Scheffer GL, Hamza I. Control of metazoan heme homeostasis by a conserved multidrug resistance protein. Cell Metab. 2014; 19(6):1008-1019.
40. Beru N, Sahr K, Goldwasser E. Inhibition of heme synthesis in bone marrow cells by succinylacetone: effect on globin synthesis. J Cell Biochem. 1983;21(2):93-105.
41. Dinarello CA. Interleukin-1 in the pathogen- esis and treatment of inflammatory diseases. Blood. 2011;117(14):3720-3732.
42. de Oliveira S, Reyes-Aldasoro CC, Candel S, Renshaw SA, Mulero V, Calado A. Cxcl8 (IL- 8) mediates neutrophil recruitment and behavior in the zebrafish inflammatory response. J Immunol. 2013;190(8):4349- 4359.
43. Cao C, Fleming MD. The ins and outs of erythroid heme transport. Haematologica. 2015;100(6):703.
44. Bagger FO, Sasivarevic D, Sohi SH, et al. BloodSpot: a database of gene expression profiles and transcriptional programs for healthy and malignant haematopoiesis. Nucleic Acids Res. 2016;44(D1):D917-924.
45. Chan A, Liebow A, Yasuda M, et al. Preclinical development of a subcutaneous ALAS1 RNAi therapeutic for treatment of hepatic porphyrias using circulating RNA quantification. Mol Ther Nucleic Acids. 2015;4(11):e263.
46. Balwani M, Wang B, Anderson KE, et al. Acute hepatic porphyrias: recommendations for evaluation and long-term management. Hepatology. 2017; 66(4):1314-1322.
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Iron Metabolism & its Disorders
The SLC40A1 R178Q mutation is a recurrent cause of hemochromatosis and is associated with a novel pathogenic mechanism
Chandran Ka,1,2,3* Julie Guellec,1,3,4* Xavier Pepermans,5 Caroline Kannengiesser,3,6,7 Cécile Ged,7,8 Wim Wuyts,9 David Cassiman,10
Victor de Ledinghen,11 Bruno Varet,12 Caroline de Kerguenec,13 Claire Oudin,6 Isabelle Gourlaouen,1,3 Thibaud Lefebvre,6 Claude Férec,1,2,7
Isabelle Callebaut14 and Gérald Le Gac1,2,3,7
Haematologica 2018 Volume 103(11):1796-1805
1UMR1078, INSERM, Université Bretagne Loire – Université de Bretagne Occidentale, Etablissement Français du Sang – Bretagne, Institut Brestois Santé-Agro-Matière, Brest, France; 2Laboratoire de Génétique Moléculaire et Histocompatibilité, CHRU de Brest, Hôpital Morvan, France; 3Laboratory of Excellence GR-Ex, Paris, France; 4Association Gaetan Saleun, Brest, France; 5Center for Human Genetics, University Hospital of St- Luc, Brussels, Belgium; 6UMR1149, INSERM, Centre de Recherche sur l'Inflammation, Université Paris Diderot, AP-HP, Hôpital Bichat, Département de Génétique, France; 7On behalf of the French National Network for the Molecular Diagnosis of Inherited Iron Overload Disorders (J. Rochette, E. Cadet, C. Kannengiesser, H. Puy, C. Ged, H. de Verneuil, G. Le Gac, C. Férec, S. Pissard, V. Gérolami), Brest, France; 8INSERM U1035, BMGIC, CHU de Bordeaux, Laboratoire de Biochimie et Biologie Moléculaire, France; 9Department of Medical Genetics, University and University Hospital of Antwerp, Edegem, Belgium; 10Department of Gastroenterology-Hepatology and Metabolic Center, University Hospital of Leuven, Belgium; 11Department of Gastroenterology and Digestive Oncology, University Hospital of Bordeaux, France; 12Université Paris Descartes et AP-HP, Hôpital Necker, Service d’Hématologie, France; 13AP-HP, Hôpital Beaujon, Département d'Hépatologie, Clichy, France and 14UMR7590, CNRS, Sorbonne Universités, Université Pierre et Marie Curie-Paris, France
*CK and JG contributed equally to this work
ABSTRACT
Hemochromatosis type 4 is one of the most common causes of pri- mary iron overload, after HFE-related hemochromatosis. It is an autosomal dominant disorder, primarily due to missense muta- tions in SLC40A1. This gene encodes ferroportin 1 (FPN1), which is the sole iron export protein reported in mammals. Not all heterozygous mis- sense mutations in SLC40A1 are disease-causing. Due to phenocopies and an increased demand for genetic testing, rare SLC40A1 variations are fortuitously observed in patients with a secondary cause of hyperfer- ritinemia. Structure/function analysis is the most effective way of estab- lishing causality when clinical and segregation data are lacking. It can also provide important insights into the mechanism of iron egress and FPN1 regulation by hepcidin. The present study aimed to determine the pathogenicity of the previously reported p.Arg178Gln variant. We pres- ent the biological, clinical, histological and radiological findings of 22 patients from six independent families of French, Belgian or Iraqi decent. Despite phenotypic variability, all patients with p.Arg178Gln had elevat- ed serum ferritin concentrations and normal to low transferrin saturation levels. In vitro experiments demonstrated that the p.Arg178Gln mutant reduces the ability of FPN1 to export iron without causing protein mis- localization. Based on a comparative model of the 3D structure of human FPN1 in an outward facing conformation, we argue that p.Arg178 is part of an interaction network modulating the conformation- al changes required for iron transport. We conclude that p.Arg178Gln represents a new category of loss-of-function mutations and that the study of “gating residues” is necessary in order to fully understand the action mechanism of FPN1.
Correspondence:
gerald.legac@univ-brest.fr
Received: January 29, 2018. Accepted: July 6, 2018. Pre-published: July 12, 2018.
doi:10.3324/haematol.2018.189845
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1796
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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ARTICLE
]]></page><page Index="57" isMAC="true"><![CDATA[Ferroportin structure and function
Introduction
Hemochromatosis type 4 (OMIM #606069), also called ferroportin disease, is an inborn error of iron metabolism transmitted through autosomal dominant inheritance and associated with mutations in the gene encoding the solute-carrier family 40 member 1 (SLC40A1). Although rare, hemochromatosis type 4 is observed in different eth- nic groups and is considered to be the second most com- mon cause of hereditary iron overload after HFE-related hemochromatosis.1,2
SLC40A1, also known as ferroportin 1 (UniProt acces- sion number Q9NP59), is the sole iron export-protein reported in mammals. It is expressed in all types of cells that handle major iron flow, including macrophages, duo- denal enterocytes, hepatocytes and placenta syncytiotro- phoblasts.3 Expression of ferroportin 1 on the cell surface is predominantly regulated by the liver-derived peptide hepcidin, which induces internalization and degradation of ferroportin 1 and thereby decreases the delivery of iron to plasma.4 The hepcidin-ferroportin axis plays an impor- tant role in the pathogenesis of inherited and acquired iron metabolism disorders, including iron overload diseases and iron-restricted anemia.5
Mutations that alter ferroportin 1 function are expected to produce stronger effects in reticuloendothelial macrophages than in enterocytes or hepatocytes. These macrophages acquire most of their iron by recycling senescent red blood cells and account for >80% of the daily iron flux within the body.6 In line with this expecta- tion, and at variance with HFE-related hemochromatosis, patients with loss-of-function mutations usually present with mesenchymal or mixed iron overload (correspond- ing to early iron deposition within Kupffer cells) and markedly elevated serum ferritin levels, contrasting with normal or low transferrin saturation values.7,8 Aggressive phlebotomy regimens can be a problem in the early stages of the disease, when patients often display border- line anemia.9,10
Although a majority of SLC40A1 mutations reported as being causally linked to hemochromatosis type 4 are true “pathogenic variants”,11 there may be some doubt in the case of variants for which phenotypic, population, segre- gation, functional and/or computational data are lacking or not fully convincing. The problem is not specific to hemochromatosis type 4, but includes all Mendelian dis- orders associated with large allelic heterogeneity, and can be mimicked by non-genetic conditions.12,13 Assessing the pathogenicity of 18 non-synonymous SLC40A1 variants found in 44 suspected hemochromatosis 4 patients, we previously demonstrated that eight very rare missense mutations had no noticeable effects on ferroportin 1 func- tion or interaction with hepcidin.14 All these variants were identified in single cases showing moderate serum ferritin elevation and normal transferrin saturation, a biological condition that is common in clinical practice and is largely related to lifestyle and environmental factors.15
The present study provides strong evidence that the SLC40A1 p.Arg178Gln missense mutation is recurrent in the SLC40A1 gene of patients showing typical reticuloen- dothelial iron overload. We further demonstrate that the p.Arg178Gln ferroportin 1 mutant shows reduced ability to export iron out of the cell. This is likely a direct conse- quence of salt bridge disruption between Arg178 and Asp473, thereby affecting the stable formation of the
intracellular gate present in the ferroportin 1 outward fac- ing state. Such a molecular mechanism of pathogenesis has never been reported in the context of hemochromato- sis type 4.
Methods
Genetic studies
DNA was extracted from the peripheral blood of patients and unaffected family members. The complete coding sequence of SLC40A1 and intron/exon boundaries was investigated by Sanger sequencing in the probands, while family members were only assessed for exon 6 (containing codon p.Arg178). All probands were negative for genotypes known to cause hemochromatosis types 1-3 (in the HFE, HFE2, HAMP and TFR2 genes) and for mutations in the FTL and BMP6 genes (hyperferritinemia cataract syndrome: OMIM#600886; hyperferritinemia without iron over- load and cataract: OMIM#134790; BMP6-related iron overload: OMIM#112266). Polymerase chain reaction and sequencing con- ditions are available upon request.
A total of 734 DNA samples from healthy subjects, exclusively from north-western France (Brittany), were investigated to control the frequency of the SLC40A1 p.Arg178Gln variant.
Informed consent for molecular studies was obtained from all patients and family members, in accordance with the Declaration of Helsinki; in line with French ethical guidelines, the Clinical Research Ethics Committee of the University Hospital of Brest approved the study on October 25, 2010.
Hepcidin measurement in human serums
Serum hepcidin concentrations were measured using liquid chromatography coupled with tandem mass spectrometry (LC- MS/MS), as previously described.16 The 95% reference interval obtained for normal hepcidin (200 serum samples from healthy subjects) ranged from 1.0 and 20.8 ng/mL (mean: 8.2 ng/mL).
Human-25 hepcidin synthesis and secretion by T-Rex-293 cells
Human HAMP cDNA was amplified with reverse-transcription polymerase chain reaction (RT-PCR) from total ribonucleic acid (RNA) isolated from human liver hepatocellular carcinoma HepG2 cells. The PCR product was cloned into the PCR2.1 vector using the TA Cloning Kit (Thermo Fisher Scientific), subcloned into the pcDNA4TM4/TO tetracycline-regulated mammalian expression vector (Thermo Fisher Scientific), and checked by sequencing.
T-Rex-293 cells (Thermo Fisher Scientific) were stably transfect- ed with calcium phosphate, and colonies were selected in the presence of 1.5 mg/ml blasticidin and 100 mg/ml zeocin for four weeks. Tetracycline (Sigma, St. Louis, MO, USA) was used to induce expression of the 84 hepcidin pre-propeptide amino acids from 1.106 T-Rex-293 cells. After 48h the cell supernatant was col- lected, filtered through a hydrophilic nylon membrane (pore size: 0.2 mm), and measured for hepcidin-25 levels using a commercially available competitive enzyme-linked immunosorbent assay kit (ELISA; Peninsula Laboratories International, San Carlos, CA, USA). The supernatant was stored at -20°C until used.
In vitro experiments
In vitro investigations were performed as previously described14,17
and are presented in detail in the Online Supplementary Data.
3D structure modeling and analysis
Models of the 3D structure of human ferroportin 1 were built using Modeller v9.15,18 considering the sequence alignment
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Table 1. Biological and clinical data of index cases and their relatives.
FamilyCountry Family Gender Age* SF TS HIC AST ALT GGT CRP RBC Hb Ht MCV Clinical Alcohol
1
2
3
relationships
(years) (mg/L) (%) ( mol/g) (IU/L) (IU/L) (IU/L) (mg/L)(Tera/L) (g/dL) (%) (fL) observations consumption**
Belgium Index case M Father M Daughter F Son M France Index case M Son M France Index case M Brother M Father M Grandmother F Uncle M First cousin F First cousin M 4 Belgium Indexcase M
39
61
11
7
55
20 976 27
15,7 45 Fatigue Moderate 15,2 42,5
12,6 Abstinent 12,9 Abstinent 15.6 45,8 96,5 Digestive problems Abstinent 18.4 52.1 90.9 Obesity Abstinent
Abstinent Abstinent
1873 33 1190
322 552
1452 36
180
85 60
37 58 61 1.5 4.75
54 98 23 2.3 5.73
12 6 35 72 45 21 22 54 29
773 33 382
1200
284
487
367
584 28
1114 26
Daughter F Son M Brother M Godson M
Goddaughter F
Iraq Index case M
France Index case M
Son M
reported by Taniguchi et al. in 201519 and, as templates, the exper- imental 3D structures of Bdellovibrio bacteriovorus (Bb) iron trans- porter Bd2019 in outward and inward facing conformations (pdb 5aym and 5ayo,19 respectively).
Statistical analysis
Data are presented as scatter dot plots and means. Comparisons used a one-tailed Student’s t-test.
Results
Clinical data and segregation analysis
The SLC40A1 p.Arg178Gln (c.533G>A) variant was identified in 22 patients from six independent families (Figure 1). It co-segregated with hyperferritinemia (defined as serum ferritin > 300 mg/L in males and > 200 mg/L in females) in all the tested patients, irrespective of age at testing, and was absent in three non-affected mem- bers of families 3 and 4.
Index cases comprised six males, aged 12-72 years at diagnosis, who displayed significant hyperferritinemia and non-elevated transferrin saturation (Table 1). Hepatic Iron Concentration (HIC) was evaluated using the Gandon’s magnetic resonance imaging (MRI) method20 in three patients with values between 60 (youngest case) and 250 mmol/g (oldest case) dry weight. Liver biopsy, performed in the index case of family 1, confirmed iron
263 21 25 613
5
6
59 1164 28 35 1354 36 32 372 25 71 2306 29 57 1386 43 27 1066 33
250
3830436
25112235
14,4 97 Fatigue Abstinent
15,4 45,3 91 Hepatomegaly Moderate
*Age at diagnosis. **Moderate: up to 1 drink per day for women and up to 2 drinks per day for men. SF: serum ferritin (normal value ≤ 200 μg/L in females, ≤ 300 in males); TS: transferrin sat- uration (normal value < 45%); HIC: hepatic iron concentration (normal value < 36 mmol/g); AST: aspartate aminotransferase (normal range: 5-50 IU/L); ALT: alanine aminotransferase (normal range: 5-50 IU/L); GGT: gamma-glutamyl transferase (normal range: 5-55 IU/L); CRP: C-reactive protein; RBC: red blood cell (normal range: 4.0-5.7 x 1012/L); Hb: hemoglobin (normal range: 12.0- 18.0 g/dL); Ht: hematocrit (normal range: 37-52%); MCV: mean corpuscular volume (normal range: 80-95 fL).
overload, with a predominance of iron deposition in Kupffer cells (Figure 2). The patient showed no clinical symptoms, except for persistent fatigue. The platelet count (178x109/L; normal range: 120-369x109/L) was not suggestive of a fibrotic liver disease. The patient started a phlebotomy program. After 24 phlebotomies (450 mL every three weeks), the hemoglobin level dropped to 13.6 g/dL, from 15.7 g/dL at diagnosis (normal range: 13.5 – 17.5).
In total, the cohort consisted of 17 males and five females. Women had lower serum ferritin levels than men (263-372 versus 487-2306 mg/L), while four children exhib- ited increased iron store between the ages of six and 12. Carrier testing in families identified 16 patients for whom no clinical manifestations of iron overload were reported.
Serum hepcidin measurements were obtained before therapeutic phlebotomy in two affected individuals of family 3 (3.II.5 and 3.III.4). They were above the reported range in healthy individuals for the assay used (1.0-21 ng/mL; liquid chromatography coupled with tandem mass spectrometry).16 The proband’s grandmother (3.I.1) start- ed therapeutic phlebotomy (1-2 venesections per year; well tolerated) several years before family screening. She showed moderately increased ferritin (280 μg/L) at the time of serum hepcidin evaluation (41.6 ng/mL). In con- trast, normal serum hepcidin levels (8.2 ng/mL) were detected in the proband’s brother who was negative for
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Figure 1. Family studies and pedigrees with the p.Arg178Gln missense mutation. Arrows indi- cate the index case. Biological data of family members are present- ed, when available. TS: transferrin saturation; SF: serum ferritin.
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Figure 2. Liver histology of the index case of family 1 at diagnosis. Perls’ stain of liver biopsy shows significant amounts of stainable iron in Kupffer macrophages, while mild iron overload is observed in hepatocytes.
the SLC40A1 p.Arg178Gln missense mutation and had normal iron indices (3.III.1).
It is noteworthy that the index case of family 2 and his son had two co-existing conditions of hyperferritinemia: hemochromatosis type 4 and hepatic steatosis. Transient Elastography-based Controlled Attenuation Parameter (TE-CAP) measurements revealed grade 3 severe steatosis in both family members (CAP scores: 396 and 363 dB/m, respectively). The index case was a 55-year-old male with 36% transferrin saturation and a serum ferritin level of 1,452 mg/L at diagnosis. He presented with a waist circum- ference of 104 cm, in a context of subnormal laboratory metabolic and liver tests: uric acid (453 mol/L; normal range: 240-420), total cholesterol (7 mmol/L; normal range: 3.5-6.0), alanine aminotransferase (58 IU/L; normal range: 5-50) and gamma-glutamyl transferase (61 IU/L; normal range: 5-55). Blood pressure, aspartate aminotrans- ferase, triglycerides, HDL cholesterol and fasting blood glucose were within normal ranges. Abdominal magnetic MRI showed significantly reduced liver signal intensity, consistent with advanced iron overload (HIC: 180 μmol/g). The patient started venesection therapy when he turned 60 years old, after being diagnosed with prostate cancer and colon polyps. The phlebotomy program (500 mL every two weeks for eight months, then monthly for four months) was well tolerated. His son, who became overweight during infancy (waist circumference at diag- nosis: 105 cm; Body Mass Index: 31.7 kg/m2), presented
similar iron indices at the age of 20 years (transferrin satu- ration: 27%; serum ferritin: 976 mg/L). MRI, however, revealed a moderate increase in hepatic iron store (HIC: 85 mmol/g).
Functional characterization of the ferroportin 1 p.Arg178Gln variant
The functional significance of the p.Arg178Gln variant was determined by first investigating its subcellular local- ization. Wild-type (WT) and mutant ferroportin 1-V5 con- structs were expressed in HEK293T cells, and plasma membrane localization of the V5-tagged proteins was assayed by Western blot and densitometry. HLA-A was used as the control and standard for normalization, being a cell-surface protein with no known role in iron metabo- lism. The p.Ala77Asp missense mutation, which signifi- cantly damages ferroportin 1 structure and is known to prevent cell-surface localization,17,21 was used as the nega- tive control. The p.Arg178Gln mutant was properly local- ized on the cell surface, comparable to the WT protein (Figure3A).
Next, the iron-exporting function of the ferroportin 1 p.Arg178Gln variant was assessed using radioactively labeled iron. HEK293T cells were grown in 20 mg/L 55Fe-transferrin for 24 hr, washed, transiently transfected, and placed in a serum-free medium. The amount of 55Fe exported into the supernatant was measured after a period of 36 hr using cells transfected with the commercial
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A
B
pcDNA3.1-V5-His vector as negative control (no FPN1). As shown in Figure 3B, cells transfected with WT ferro- portin 1-V5 displayed a 3-fold increase in iron release. The p.Arg178Gln variant was not able to export iron 55Fe in amounts comparable with WT ferroportin 1, but was more active than the p.Ala77Asp control; Student’s t-tests highlighted significant differences between both variants and WT ferroportin 1 (P<0.001 and 0.0001, respectively) and between the two variants (P<0.0001).
To investigate whether the p.Arg178Gln missense mutation could modify response to hepcidin, transiently transfected HEK293T cells were cultured for 24 hr with conditioned media derived from T-Rex-293 cells stably transfected with full-length human HAMP cDNA. Supernatant human-25 hepcidin concentration was deter- mined using a competitive enzyme-linked immunosor- bent assay. Two known ferroportin 1 mutants served as positive controls: p.Asn144His, which shows partial resistance to hepcidin inhibition,22 and p.Cys326Tyr, which abolishes hepcidin binding to ferroportin 1 and is responsible for complete resistance.23 As expected, the addition of hepcidin to cells expressing WT ferroportin 1 resulted in the disappearance of the iron exporter from the plasma membrane. The Western blot pattern of the p.Asp178Gln variant, unlike the p.Cys326Tyr and p.Asn144His mutants, was similar to that of the WT pro- tein (Figure 4).
Structural and functional investigation of the intermolecular interaction between the N and C lobes of human ferroportin 1 – 3D structure form I (outward facing)
In order to understand the possible impact of the p.Arg178Gln mutation, we modeled the 3D structure of human ferroportin in both the outward and inward facing conformations, based on the recent 3D structures of the Bb iron transporter Bd2019, which shares 24% sequence identity with human ferroportin 1.19
As illustrated in Figure 5, Arg178 forms an inter-lobe salt bridge with Asp473 in the outward facing conformation of human ferroportin 1. We hypothesized that this non- covalent interaction between helix TM5 and helix TM8, located respectively in the N and C lobes, might be impor- tant in stabilizing the outward facing conformation of fer- roportin 1, and that its disruption might cause a significant reduction in iron egress.
To check this hypothesis, we replaced arginine 178 and aspartic acid 473 with alanine, which is the smallest amino acid after glycine and is neutral, being non-polar and devoid of any strong hydrophobic character. Moreover, it has the highest propensity of the 20 amino acids for the a-helical state;24 thus this modification was likely to have limited impact on local structure. As shown in Figure 6, the Asp473Ala mutant did not cause obvious mislocalization of the protein, which was, however, total- ly inoperative for iron export. Indeed, cells expressing the Asp473Ala mutant retained 55Fe in amounts comparable to cells expressing the two known p.Asn77Asp and p.Val162del loss-of-function mutations. The Arg178Ala mutant reduced cell surface expression to half that of the WT, but with less influence in iron export ability.
We then examined whether charge swapping could restore the iron export function of ferroportin 1, and whether Arg178Gln dysfunction could be corrected by a p.Asp473Arg mutation. The p.Arg178Asp and
Figure 3. The ferroportin p.Arg178Gln mutant shows normal cell surface
expression, but substantial loss of iron export. (A) HEK293T cells were tran-
siently co-transfected with plasmids encoding either a V5-tagged ferroportin pro-
tein (WT or variant) or a V5-tagged HLA-A protein. Human leukocyte antigen
(HLA)-A was used as control and standard for normalization, being a cell surface
protein with no known role in iron metabolism. At 24h after transfection, cell sur-
face proteins were selectively purified and analyzed by Western blotting using a
peroxidase conjugated mouse anti-V5 antibody. Densitometric scans of
SLC40A1 levels (normalized to HLA-A) are shown in the lower part of the figure.
The results of three independent experiments are presented. (B) HEK293T cells
were grown in 20 mg/mL 55Fe-transferrin for 24h before being washed and tran-
siently transfected with WT or mutated SLC40A1-V5 expression plasmids. After
Fe exported into the supernatant was collected at 36h. Data are presented as percentage of cellular radioactivity at time zero. Each point represents the average value (from tripli- cate) of five independent experiments. P values were calculated with the
15h, cells were washed and then serum-starved. The Student’s t-test; **P<0.01 and ****P<0.0001. WT: wild-type.
55
p.Asp473Arg substitutions almost abolished cell surface expression of the protein. Introducing the two p.Arg178Asp and p.Asp473Arg missense mutations did not rescue the membrane expression level decreased by single mutations. The Arg178Gln/Asp473Arg double mutant also resulted in a strong reduction in cell surface expression (Online Supplementary Figure S1).
Taken together, these results suggested that the salt bridge between arginine 178 and aspartic acid 473 is essential for ferroportin 1 iron export function. Any subtle changes in charge or size on the side chains may cause loss of function.
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Discussion
The p.Arg178Gln missense mutation is typical of the fer- roportin 1 variants for which evidence remains inadequate and clinical pathogenicity doubtful. Herein, we provide a comprehensive genotype-phenotype analysis, and argue
that p.Arg178Gln substitution abolishes a salt bridge between the N and C lobes of human ferroportin 1, leading to a less stable outward facing state and, thus, to an altered equilibrium between the different conformational states.
The p.Arg178Gln missense mutation was first reported in a 70-year-old female with hyperferritinemia and normal
Figure 4. The ferroportin p.Arg178Gln mutant is not resistant to hepcidin. HEK293T cells were tran- siently co-transfected with plasmids expressing HLA(A)-V5 and either wild-type SLC40A1-V5 (WT) or SLC40A1-V5 variants. At 16h post-transfection, the cells were incubated in the presence or absence of hepcidin for 3h. Plasma membrane proteins were purified and analyzed by Western blotting and den- sitometry. Data are expressed as the percentage of ferroportin in cells not treated by hepcidin, accord- ing to the formula 100 x (SLC40A1 – hepcidin / SLC40A1 + hepcidin). Error bars are the standard deviation of three independent experiments.
TM8
TM1
N174 D473
TM10
TM7 TM12
TM5
R178 Q481
TM4
D157 R489
TM11
TM6
TM3
TM2
TM9
R88 E486
D84
Figure 5. Ribbon representation of a human ferroportin-1 3D structure model in an outward facing conformation, with atomic representation of amino acids involved in non-covalent bonds, likely leading to the stabilization of this conformation. The iron within the iron-binding site is represented as a red ball at the top of the figure. This figure was drawn using Chimera.38
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transferrin saturation,25 and then observed with incom- plete penetrance in members of an independent Greek family. Serum ferritin was found to be markedly elevated in the proband (a 25-year-old female), but only slightly in her 53-year-old mother and within the normal range in her 87-year-old grandfather.26,27 We observed the p.Arg178Gln missense mutation in 11 adult males with high serum fer- ritin concentrations (>970 mg/L) and normal plasma iron levels (transferrin saturation: 26-43%). Three adult females from the larger pedigrees (3.III.4, 4.II.1 and 4.II.6) displayed a mild phenotype, with serum ferritin concen- trations ranging between 200 and 400 mg/L at diagnosis, while two males presented an intermediate phenotype (584 and 613 mg/L) in their third decade (3.III.6 and 4.II.3). Liver biopsy was available for the index case of family 1, and showed tissue iron overload, with iron deposits pri- marily observed in non-parenchymal cells. The index case
had two children who exhibited increased iron stores at 11 and seven years of age, respectively. Similar pheno- types were observed in two children from family 3 (3.III.2 and 3.III.3). None of the patients were reported to have developed significant fibrosis or cirrhosis. Taken together, these data indicate that the p.Arg178Gln substitution is responsible for the classic form of ferroportin disease, or hemochromatosis type 4A. The expressivity of the SLC40A1 p.[Arg178Gln];[=] genotype is variable, with milder phenotypes observed in women. High serum fer- ritin levels can be observed in young patients, highlighting the fact that tissue iron overload may appear early in life and that, in contrast to HFE hemochromatosis, diagnosis of ferroportin disease should not be restricted to adults.28 This recapitulates some previous observations on the rela- tionship between ferroportin loss-of-function mutations and mild to severe reticuloendothelial iron overload.2,11,29
A
B
Figure 6. Effect of p.Arg178Ala and p.Asp473Ala ferroportin variants on cell surface expression and iron export. (A) HEK293T cells were transiently co-transfected with plasmids encoding either a V5-tagged ferroportin protein (WT or variant) or a V5-tagged HLA-A protein. At 24h after transfection, cell surface proteins were selec- tively purified and analyzed by Western blotting using peroxidase-conjugated mouse anti-V5 antibody. Densitometric scans of SLC40A1 levels (normalized to HLA-A) are shown. The error bars represent the standard deviation of three independent experiments. (B) HEK293T cells were grown in 20 mg/mL 55Fe-transferrin for 24h before being washed and transiently transfected with WT or mutated SLC40A1-V5 expression plasmids. After 15h, cells were washed and then serum-starved for up to 36h. 55Fe exported into the supernatant was collected at various time points. Data are presented as a percentage of cellular radioactivity at time zero. Each point represents the mean standard deviation; n=3 in each group. The data are representative of three separate experiments. WT: wild-type.
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In contrast to all other types of hemochromatosis,
which are characterized by hepcidin deficiency, we found
increased serum hepcidin levels in three affected individu-
als from family 3. This recapitulates previous observations
in seven patients with the recurrent and well-character-
ized p.Val162del loss-of-function ferroportin 1 muta- tion.11,30,31
M. Speletas et al. and S. Cunat et al. failed to detect the p.Arg178Gln missense mutation in the DNA of 253 bone marrow donors from central Greece27 and 50 French con- trols.25 The results presented herein of 730 DNA samples from healthy subjects born in the western part of France (Brittany) were identical. The variant was also absent in GnomAD, which is an extension of the Exome Aggregation Consortium (ExAC) database and includes 123,136 exome sequences and 15,496 whole-genome sequences from unrelated individuals sequenced as part of various disease-specific and population genetic stud- ies. The p.Arg178Gln missense mutation can thus be expected to be very rare; nevertheless, it has now been associated with hyperferritinemia in 25 patients from France, Belgium, Greece and Iraq. This provides another indication of the pathogenicity of the SLC40A1 p.Arg178Gln allele, which is not restricted to European populations.
We and others have previously shown that the p.Arg88Gly, p.Ile152Phe and p.Asn174Ile clinical muta- tions are defective in terms of iron egress while being nor- mally addressed to the cell surface.14,17,32,33 In the present study, we demonstrated that the p.Arg178Gln substitu- tion follows an identical trend (Figure 3). This was not a typical situation of loss of ferroportin 1 function, which is usually associated with protein mislocalization.14,21 This prompted us to look at the 3D structure of human ferro- portin 1 and examine the molecular mechanism responsi- ble for reduced iron export.
Ferroportin 1 is a member of the major facilitator super- family (MFS),17 which is the largest group of secondary active membrane transporters, essential for the movement of a wide range of substrates across biological membranes.34 In recent years, the number of experimental 3D structures has increased dramatically, leading to a bet- ter appreciation of the conformational changes that are needed for effective MFS-mediated transport.35,36 All MFS transporters share a common and characteristic core fold that is organized in two similar domains (N and C lobes), each consisting of six consecutive transmembrane seg- ments (TM1-TM6 and TM7-TM12). They progress through a conformational cycle that involves at least four conformational states: inward open state, the ligand- bound and ligand-free occluded states, and outward open state.36 These conformational changes are orchestrated by
a set of specific residues that mediate interactions between the N and C lobes.35
The recent report of the crystal structures of a putative bacterial homologue of ferroportin 1 (BbFPN) and the description of inter- and intra-domain conformational rearrangements during the transport of iron open up new avenues for predicting the atomic details of the organiza- tion of human ferroportin transmembrane helices and elu- cidating the detailed mechanisms of iron egress.19 Such structural investigation has already been conducted, using more distant 3D structures as a template.14,17,37 In the pres- ent study, we built an outward-open conformation of human ferroportin 1, using the experimental structure of BbFPN as a template. This allowed us to specifically inves- tigate interactions between TM3, TM4 and TM5 of the N lobe and TM8 and TM9 of the C lobe (Figure 5). We demonstrated that Arg178 (TM5) forms a salt bridge with Asp473 (TM8). This bond may act in the same way as those observed between Asn174 (TM5) and Gln481 (TM10), or between Arg88 (TM3) and Glu486 (TM11) and between Asp157 (TM4) and Arg489 (TM11), thus extend- ing the definition of an interaction network on the intra- cellular side of the outward facing structure of BbFPN.19 That the interaction between Arg178 and Asp473 is important in stabilizing human ferroportin 1 in the out- ward facing state is further supported by the results pre- sented in Figure 6, where replacing arginine 178 or aspartic acid 473 by alanine strongly decreased the ability of ferro- portin 1 to export iron. The reason why the Asp473Ala mutant showed a smaller impact on protein trafficking than Arg178Ala, despite its stronger effect on iron egress, remains to be elucidated. One possibility is that the inter- ruption of the charge-helix dipole interaction (Arg178 – Asp 181) may destabilize the local structure of TM3.
To conclude, the present study demonstrates the causali- ty of the p.Arg178Gln missense mutation, which is now considered to be one of the most frequent SLC40A1 loss-of- function mutations. It also reveals a new molecular mecha- nism of disease, involving residues that participate in the stabilization of the different conformational states and thus mediate iron export. These findings can be extended to the functional interpretation of other rare missense mutations that are associated with typical reticuloenthelial iron over- load but do not significantly alter the cell surface expression of ferroportin 1. They also confirm that it is essential to identify so-called “gating residues” in order to fully under- stand the action mechanism of MFS transporters.35
Funding
The authors would like to thank the French Hospital Clinical Research Program (Progamme Hospitalier de Recherche Clinique 2009) for funding; Brest University Hospital UF0857.
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*JEA and H-PK contributed equally to this work.
Ferrata Storti Foundation
Bone Marrow Failure
Novel lineage depletion preserves autologous blood stem cells for gene therapy of Fanconi anemia complementation group A
Jennifer E. Adair,1,2* Devikha Chandrasekaran,1 Gabriella Sghia-Hughes,1 Kevin G. Haworth,1 Ann E. Woolfrey,1,2 Lauri M. Burroughs,1,2 Grace Y. Choi,1 Pamela S. Becker1,2 and Hans-Peter Kiem1,2*
Fred Hutchinson Cancer Research Center and 2University of Washington School of Medicine, Seattle, WA, USA
ABSTRACT
Ahallmark of Fanconi anemia is accelerated decline in hematopoi- etic stem and progenitor cells (CD34+) leading to bone marrow failure. Long-term treatment requires hematopoietic cell trans- plantation from an unaffected donor but is associated with potentially severe side-effects. Gene therapy to correct the genetic defect in the patient’s own CD34+ cells has been limited by low CD34+ cell numbers and viability. Here we demonstrate an altered ratio of CD34Hi to CD34Lo cells in Fanconi patients relative to healthy donors, with exclusive in vitro repopulating ability in only CD34Hi cells, underscoring a need for novel strategies to preserve limited CD34+ cells. To address this need, we developed a clinical protocol to deplete lineage+ (CD3+, CD14+, CD16+ and CD19+) cells from blood and marrow products. This process depletes >90% of lineage+ cells while retaining ≥60% of the initial CD34+ cell fraction, reduces total nucleated cells by 1-2 logs, and maintains transduction efficiency and cell viability following gene transfer. Importantly, transduced lineage– cell products engrafted equivalently to that of purified CD34+ cells from the same donor when xenotransplant- ed at matched CD34+ cell doses. This novel selection strategy has been approved by the regulatory agencies in a gene therapy study for Fanconi anemia patients (NCI Clinical Trial Reporting Program Registry ID NCI- 2011-00202; clinicaltrials.gov identifier: 01331018).
Introduction
Fanconi anemia (FA) is a rare monogenic disease with a wide array and variable presence of clinical symptoms, the hallmark of which is bone marrow (BM) failure.1 The genetic basis of FA is a mutation in any one of 21 genes2 whose protein com- ponents make up the FA/breast cancer pathway responsible for DNA repair of inter- strand crosslinks through nucleotide excision followed by homologous recombina- tion. Resulting compromises in genetic integrity are associated with a nearly uni- form decline in hematopoietic stem and progenitor cells (HSPCs), a 50% incidence of myelodysplastic syndrome or acute myeloid leukemia by adolescence, and a 25% lifetime incidence of head and neck squamous cell carcinoma or gynecological cancer.3 In some patients, blood cell clones demonstrate spontaneous reversion to wild type (i.e. somatic mosaicism) leading to improved and stable blood cell counts for up to 27 years.4-6 Thus, correction of the FA hematopoietic defect could signifi- cantly alter the disease’s clinical course, and this has driven decades of research in HSPC gene therapy for FA.
While FA was recognized as an early candidate disorder for gene therapy, several obstacles have been identified that have delayed clinical success.3 Initial clinical tri- als demonstrated a dramatic approximately 50-fold reduction in the number of true HSPCs in FA patients relative to other gene therapy patients, such as those treated for primary immune deficiencies.7 Moreover, FA HSPCs were exceptionally fragile when manipulated ex vivo for gene transfer. No treated patient has demonstrated
Correspondence:
hkiem@fredhutch.org or jadair@fredhutch.org
Received: April 6, 2018. Accepted: July 4, 2018. Pre-published: July 5, 2018.
doi:10.3324/haematol.2018.194571
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1806
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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Table 1. Clinical characteristics of 3 patients with Fanconi Anemia A genetic defect enrolled in clinical trial NCT01331018.
Patient
1
2
3
Age (years)
22
10
5
Weight (kg) Sex
70.7 Male
19.6 Male
14.7 Male
Baseline average ANC/platelet count (thousand/mL)
1.3/65
1.0/62
1.7/32
Marrow cellularity
10-30%
~20%
~30%
FANCA defect
Exon22 splice variant
(c. 1827-1 G>A)
Exons6-31
Not determined
One adult and 2 pediatric patients were treated with lentivirus gene therapy for Fanconi Anemia-A (FA-A) defect. Three patients demonstrated steadily declining: absolute neu- trophil count (ANC) and platelet counts in the peripheral blood prior to treatment and less than 30% marrow cellularity. Molecular characterization of the FANCA gene defect performed by gene sequencing demonstrated that Patient 1 was homozygous in the FANCA gene for the splicing variant. For Patient 2, Multiplex Ligation-dependent Probe Amplification (MLBA) on the FANCA gene identified a homozygous gross deletion of exons 6-31.No sequence analysis was performed for Patient 3, but complementation test- ing confirmed FANCA defect.
stable improvements in blood cell counts with long-term persistence of gene-corrected blood cells. These studies highlighted two needs for innovation in FA gene therapy: 1) to increase the number of available HSPCs for gene transfer and infusion; and 2) to increase the engraftment potential of these cells after gene transfer and infusion. Following the recommendations of the International FA Gene Therapy Working Group,8 we launched a phase I clinical trial of gene therapy for FA complementation group A (FA-A) patients in 2011 (clinicaltrials.gov identifier: 01331018). This trial design incorporates several features aiming to improve HSPC numbers and fitness. These include: i) a self-inactivating (SIN) lentiviral vector (LV) for transfer of the FANCA cDNA regulated by a human phos- phoglycerate kinase (hPGK) promoter; ii) a short, overnight transduction to minimize ex vivo manipulation, as well as addition of the antioxidant N-acetylcysteine (NAC) throughout manipulation; and iii) culture under reduced oxygen (5%) to limit oxidative DNA damage.9
The target HSPC population for gene transfer expresses the CD34 cell surface protein (CD34+). When stained with fluorophore-conjugated antibody against CD34 and ana- lyzed by flow cytometry, a small proportion of BM cells are CD34+, representing both primitive stem cells and more committed progenitors.10 The standard clinical pro- cedure for isolating these cells first involves either BM col- lection or mobilization of the cells into circulation through cytokine stimulation with granulocyte colony stimulating factor (G-CSF) or, in certain clinical scenarios, a combina- tion of G-CSF and the chemokine receptor CXCR4 antag- onist plerixafor, followed by peripheral blood leukaphere- sis (mAPH). Initial isolation technologies relied on CD34 antigen expression on the cell surface and utilized biotin- avidin affinity, panning, or immununomagnetic bead- based approaches. Expected yields were 50% of available CD34+ cells with highly variable purities, ranging from 20- 90% across techniques.11 Of these, immunomagnetic bead-based positive selection is the most widely-applied today, with the first US Food and Drug Administration (FDA) approval of a clinical device for human use in 2014. Advances in this technology to include automation have improved reliability in recovery to a mean yield of 70% with purities regularly over 90%.12,13 However, these val- ues are based on BM and mAPH products wherein 1-3% of total cells express CD34 antigen, and the majority of these cells display high levels of CD34. For FA patients, the frequency of CD34+ cells is much lower: 0.1-1.5% in BM.14,15 This implies that non-standard processes may be
required to preserve the limited numbers of HSPCs for gene transfer in FA.
Here we report HSPC collection results for the first 3 patients treated on our study. Initially, this protocol pro- posed direct isolation of CD34+ cells from BM without prior attempts at mobilization. The addition of a mobi- lization regimen with subsequent leukapheresis collec- tions has permitted the evaluation of CD34 expression patterns in both product types and provided evidence for the need for alternative HSPC isolation strategies.
Methods
Patientselection
This study was approved by an Institutional Review Board at Fred Hutchinson Cancer Research Center (Fred Hutch) in accor- dance with the Declaration of Helsinki and the FDA, and con- formed to the National Institutes of Health Guidelines for Research Involving Recombinant DNA Molecules. Informed con- sent was obtained from all patients or guardians. FA patients aged 4 years or over were diagnosed by a positive test for increased sen- sitivity to chromosomal breakage with mitomycin C (MMC) or diepoxybutane. Correction of melphalan hypersensitivity follow- ing retroviral transduction of the FANCA cDNA identified Patient 3 as belonging to the FA-A complementation group. (Online Supplementary Table S1). FA-A patients who demonstrated normal karyotype in BM analyses as defined in the trial were considered eligible for the study. Characteristics of enrolled patients are avail- able in Table 1.
Lentiviral vectors
All SIN lentiviral (LV) vectors were produced with a third-gen- eration split packaging system and pseudotyped with vesicular stomatitis virus glycoprotein. LV used to transduce healthy donor cells encoded either an enhanced green fluorescent protein (eGFP) transgene (pRSC-PGK.eGFP-sW) or the full-length FANCA cDNA (pRSC-PGK.FANCA-sW), both regulated by an hPGK promoter. Research-grade vectors were produced by the Fred Hutch Vector Production Core (Principal Investigator: HPK). Clinical-grade LV (pRSC-PGK. FANCA-sW), was produced by the Indiana University Vector Production Facility (IUVPF, IN, USA) using a large-scale, validated process following Good Manufacturing Practices standards under an approved Drug Master File held by IUVPF. Infectious titer was determined by serial transduction of HT1080 human fibrosarcoma-derived cells and evaluated either by flow cytometry for eGFP expression or by quantitative poly- merase chain reaction (qPCR).
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Table 2. Isolation and lentiviral vector transduction of autologous Fanconi Anemia A genetic defect HSPC.
Patient
1
2 3
Product Product collected volume
processed
BM 1278 mL
BM 534 mL mAPH 513 mL
Total CD34+ cells collected
1.69E+08
1.59E+07 9.5E+07
CD34+ cell purification method
Direct
enrichment
None
Lineage
depletion
CD34+ cells transduced
5.34E+06
8.15E+06 5.28E+07
CD34+ cell dose/kg
3.57E+04
3.57E+05 2.44E+06
CD34Hi cell dose/kg
1.77E+04
4.62E+04 3.69E+05
% Gene transfer in CFCs,
CD34Lo cell dose/kg
1.65E+04
3.15E+05 2.06E+06
% Gene transfer in CFCs,
CD34Hi: high CD34 expression; CD34Lo: low CD34 expression; BM: bone marrow product; mAPH: mobilized apheresis product.
Table 3. Transduction efficiency.
Patient
1
2
MOI (IU/cell)
10 IU/ cell
10 IU/ cell
Viability of infusion product (%)
79
99.5
VCN of infusion product
0.33
1.83
Plating efficiency in CFCs,
Plating efficiency in CFCs,
0nMMMC(%) 10nMMMC(%) 0nMMMC(%) 10nMMMC(%
4.14 0.22 17.7 80
3.8 0.03 42.73 100
3 5IU/cell 99.3 0.67 2.75 0.04 26.23 100
Viability of the infusion product was determined by trypan blue dye exclusion.The vector copy number (VCN) in the bulk transduced population was determined by quanti- tative polymerase chain reaction (qPCR) method against a reference standard curve.Plating efficiency of the infusion product was determined as the percentage of CD34+ cells plated with colony-forming capacity. Functional correction of the FANCA gene defect was determined by calculating the plating efficiency under stress of various concentra- tions of MMC. Gene transfer in colony-forming cells (CFCs) was determined as the percentage of colonies analyzed positive for the presence of lentivirus backbone by PCR analysis on DNA extracted from individual colonies. MOI: multiplicity of infection.
Study design and HSPC isolation
Patients underwent either BM harvest with a target collection goal of 15 cc/kg body weight or were administered daily G-CSF (filgrastim; 16 mg/kg BID; days 1-6) and plerixafor (240 mg/kg/day; days 4-6) subcutaneously to mobilize CD34+ cells. Mobilized patients were subjected to large volume leukapheresis when circu- lating CD34+ blood cell counts were ≥5 cells/mL. Healthy donor blood products were purchased from a commercial source (BM products; StemExpress, Folsom, CA, USA) or institutional shared resources (mAPH products). Immunomagnetic beads were from Miltenyi Biotech, GmbH (Auburn, CA, USA). For BM products, RBC were debulked by hetastarch sedimentation prior to labeling on a CliniMACS ProdigyTM device (Miltenyi Biotec GmbH, Germany). For mAPH products, an initial platelet wash was per- formed prior to labeling. Custom programming for lineage deple- tion was designed and executed on the CliniMACS ProdigyTM device (Miltenyi Biotec, GmbH). Complete processing methods are included in the Online Supplementary Materials and Methods.
Transduction
Transplantation in NSG mice
All animal work was performed under protocol 1864 approved by the Fred Hutch Institutional Animal Care and Use Committee. NOD.Cg-PrkdcscidIL2rγtmlWj/Szj (NOD/SCID/IL2rγnull, NSG) mice were housed at Fred Hutch in pathogen-free conditions approved by the American Association for Accreditation of Laboratory Animal Care. 8-12-week old mice received 275 cGy total body irradiation (TBI) from a Cesium source. Four hours after TBI, 1x106 gene-modified total nucleated cells (TNCs) re-suspended in 200 mL phosphate buffered saline (D-PBS, Life Technologies Corporation, Grand Island, NY, USA) containing 1% heparin (APP) were infused via tail vein. Blood samples were collected into ethylenediaminete- traacetic acid (EDTA) Microtainers (BD Bioscience, San Jose, CA, USA) by retro-orbital puncture and diluted 1:1 with PBS prior to analysis. At necropsy, spleen and BM were collected. Tissues were filtered through 70 mm mesh (BD Bioscience) and washed with Dulbecco’s PBS (D-PBS).
Colony-forming cell assays
Transduced cell products were seeded in standard CFC assays in methylcellulose media (H4230, Stem Cell Technologies) as previously described16 with the following exceptions: to assess FANCA gene function, MMC (Sigma Aldrich, St. Louis, MO, USA) was added at concentrations of 0 nM, 5 nM, 10 nM, or 20 nM. Complete colony DNA extraction and PCR methods are included in the Online Supplementary Materials and Methods.
Quantitative real-time PCR-based measurement of vector copy number
Vector copy number (VCN) per genome equivalent was assessed by TaqMan 5' nuclease quantitative real-time PCR assay in duplicate reactions with an LV-specific primer/probe combination [forward, 5'-TGAAAGCGAAAGGGAAACCA;
CD34-enriched cells were cultured on RetroNectin (Takara Bio, Mountain View, CA, USA)-coated culture flasks at a density of 1x106 cells/mL and 2.9x105 cells/cm2 in StemSpanTM ACF media (StemCell Technologies, Vancouver, BC, Canada), supple- mented with 4 mg/mL of protamine sulfate (American Pharmaceutical Partners; APP, East Shaumburg, IL, USA), 100 ng/mL each of recombinant human stem cell factor (rhSCF), thrombopoietin (rhTPO) and Flt-3 ligand (rhFLT3L) (all from CellGenix GmbH, Freiburg, Germany), and 1 mM NAC (Cumberland Pharmaceuticals, Nashville, TN, USA). Cells were immediately transduced at a multiplicity of infection (MOI) of 5- 10 infectious units (IU)/cell. Following 12-24 hours of incubation at 37°C, 5% CO2 and 5% O2 , cells were harvested for infusion and/or analyses.
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Figure 1. Diminished CD34Hi hematopoietic cells from Fanconi Anemia A genetic defect (FA-A) patients. CD34 expression in baseline bone marrow (BM) (Patients 1, 2, 3, and healthy donor 1) or mobilized leukapheresis (mAPH) (Patient 3 and healthy donor 2) products was determined by fluores- cence staining and flow cytometry analysis. Positive cell fractions are gated based on unstained and isotype stained control samples into two levels of CD34 expression: low expression, CD34Lo, or high expression, CD34Hi. The average mean fluorescence intensity (MFI) of CD34Lo population = 3453; standard error of the mean (SEM) = 516 and CD34Hi population = 19731; SEM = 4103.
reverse, 5'-CCGTGCGCGCTTCAG; probe, 5'-AGCTCTCTC- GACGCAGGACTCGGC (Integrated DNA Technologies; IDT, Coralville, IA, USA)] and in a separate reaction with a β-globin- specific primer/probe combination [forward, 5’-CCTATCA- GAAAGTGGTGGCTGG; reverse, 5'-TTGGACAGCAA- GAAAGTGAGCTT; probe, 5'-TGGCTAATGCCCTGGCCCA- CAAGTA (IDT)]. Two standard curves were established by seri- al dilution of gDNA isolated from a human cell line (HT1080) confirmed to contain a single integrant of the same LV backbone and from peripheral leukocytes collected from a healthy donor using both primer-probe sets independently.
Individual colony gDNA samples were subjected to multiplex real-time TaqMan qPCR to amplify the LV-specific product and an endogenous control (TaqMan Copy Number Reference assay RNaseP, Thermo Fisher Scientific, Pittsburgh, PA, USA). Samples with an average VCN ≥0.5 were considered transduced.
Flow cytometry analysis of hematopoietic subsets
Stained cells were acquired on a FACSCantoTM II, FACSAriaTM II or FACS LSR II (all from BD Bioscience) and analyzed using FlowJo software v.10.0.8 (Tree Star Inc., Ashland, OR, USA). Analysis was performed on up to 20,000 cells. Gates were estab- lished using Full Minus One stained controls.
Antibodies included anti-human CD34 (clone 563), CD16 (clone 3G8), CD3 (clone UCHT1), CD4 (clone L200), CD8 (clone RPA-T8), all from BD Biosciences; CD14 (clone 61D3, Thermo Fisher Scientific, Pittsburgh, PA, USA); CD19 (clone 4G7, BD Pharmingen, San Diego, CA, USA); CD90 (clone 5E10), CD20 (clone 2H7), CD15 (clone W6D3), all from Biolegend (San Diego, CA, USA); CD133 (clone 293C3, Miltenyi Biotec, GmbH); CD45 (clone D058-1283) and CD45RA (clone 5H9), both from BD Horizon (San Jose, CA, USA).
For mouse samples, antibodies were anti-mouse CD45-V500 (561487, clone 30-F11), anti-human CD45-PerCP (347464, clone 2D1), CD3-FITC (555332, clone UCHT1), CD4-V450 (560345, clone RPA-T4), CD8-APCCy7 (557834, clone SK1), CD20-PE (555623, clone 2H7), and CD14-APC (555824, clone 581), all from BD Biosciences.
Results
Diminished CD34Hi expressing cells in FA-A BM and mAPH
Two enrolled patients underwent BM harvest to collect available CD34+ HSPCs (Patients 1 and 2). The third patient underwent mobilization with filgrastim and pler- ixafor followed by peripheral blood leukapheresis (Patient 3). All 3 patients demonstrated reduced CD34 expression and estimated numbers of CD34+ cells in screening BM aspirate samples prior to collection and treatment, relative to healthy donor BM products, as well as in cell products collected for CD34+ cell isolation and gene transfer (Figure 1). Two levels of CD34 expression were observed, CD34Lo [mean fluorescence intensity (MFI)=3453±516], and CD34Hi (MFI=19731±4103). Notably, the proportion of CD34Hi cells were markedly reduced in FA-A patients relative to those observed in healthy donors (Figure 1).
FA-A CD34Hi cells, but not CD34Lo cells, demonstrate in vitro repopulating capacity
To determine which CD34+ cells demonstrated repopu- lation potential, we used colony-forming cell (CFC) poten- tial as a surrogate. This required sufficient blood product to flow-sort CD34Lo and CD34Hi cells for in vitro assays. Only the mAPH product collected from Patient 3 was suf- ficient for this study. For direct comparison, we sort-puri- fied CD34Lo and CD34Hi cells from a healthy donor mAPH product. Only CD34Hi cells from the FA-A patient demon- strated colony-forming potential (Figure 2A). In the healthy donor, CD34Hi cells also demonstrated the major- ity of CFC capacity in comparison with CD34Lo cells, and at much higher levels as compared to the FA-A patient (Figure 2B). These data suggest repopulating capacity is restricted to CD34Hi cell fractions, underscoring the need to preserve as many of these cells as possible for gene transfer processes.
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Extensive loss of FA-A CD34Hi cells with direct clinical purification protocols
The current clinical standard for CD34+ cell enrichment is optimized for collection of CD34Hi cells. However, in Patient 1, direct enrichment of CD34+ cells using this pro- tocol was inefficient, resulting in an approximately 3% yield and only 5.34x106 total CD34+ cells available for gene transfer (Table 2). Moreover, the purity of the enriched cell product was only 58.9%, and approximately 47% loss in viable cells was observed during culture and gene transfer. Resulting gene-modified cells retained colony-forming capacity and demonstrated acquired resistance to the potent DNA crosslinking agent MMC following LV-medi- ated FANCA gene transfer (Table 3).
In Patient 2, estimated losses during direct CD34 enrich- ment and gene transfer were expected to reduce the cell product available for transduction to a level lower than observed for Patient 1. Thus, an urgent amendment was filed with the FDA to permit elimination of the direct CD34 enrichment steps and allow transduction of the entire red blood cell (RBC)-depleted BM product. This processing change preserved more CD34+ cells (Table 2), with improved transduction and viability (Table 3). Together, these data suggested that minimal manipulation of target CD34+ cells from FA-A patients could improve yield, gene transfer efficiency, and function in vivo.
Development of a novel strategy to deplete lineage+ cells
We hypothesized that depleting non-target mature B cells, T cells, monocytes, and granulocytes would retain precious CD34+ cells with minimal manipulation, since CD34-expressing cells would not be directly labeled, selected, or washed (Figure 3). Building on our previous work automating cell selection and gene transfer using the CliniMACS ProdigyTM device,17 we designed a cus- tomized, automated RBC debulking and immunomagnet- ic bead-based lineage specific depletion strategy (Online Supplementary Materials and Methods). Four different bead- conjugated antibody reagents were used in this approach: anti-CD3 (T-cell removal), anti-CD14 (monocyte removal), anti-CD16 (granulocyte and NK-cell removal), and anti-CD19 (B-cell removal). This protocol was designed for both BM and mAPH products.
Lineage depletion preserves available CD34+ cells for gene transfer
A total of nine BM and ten mAPH products were processed to establish process validity. An average 60% of BM CD45+ cells and 50% of mAPH CD45+ cells expressed one of the four target markers (CD3, CD14, CD16, or CD19) (Online Supplementary Figure S1A and B, respective- ly). CD34+ cell content in these products ranged from 0.35- 1.4% in BM and 0.06-0.9% in mAPH products. The aver- age process run time for BM products was ten hours, whereas mAPH products were processed over 13 hours. Observed total nucleated cell (TNC) reduction was approximately 1 log for both BM and mAPH products fol- lowing lineage depletion (Figure 4A). All target lineage+ cells were depleted to less than 10% of initial numbers, and CD34+ cells were retained at 94.62±4.61% for BM products and 70.69±11.4% for mAPH products (Figure 4B). Retention of available CD34Hi and CD34Lo cells was observed and comparable or superior to that observed for the same products by direct CD34-enrichment (Online
Supplementary Figure S2). Approximately 24% of BM CD34+ cells were colony-forming in a standard methylcel- lulose assay, while 51% of mAPH CD34+ cells formed colonies (Figure 4C and Online Supplementary Figure S3). However, following LV transduction of these cells using the same protocol proposed for FA-A patient cells, we observed consistent 50% rates of gene transfer into CFCs from both cell product types (Figure 4D). Analysis of sin- gle colonies demonstrated an average VCN per CFC of 0.7 for BM CD34+ cells and 1.6 for mAPH CD34+ cells. VCN was also assessed in bulk transduced cells cultured for ten days in vitro, demonstrating an average value of 5 for both BM and mAPH products (Figure 4E). Final cell products tested for mycoplasma and sterility were negative, and endotoxin testing demonstrated values within criteria for patient infusion. Lineage-depleted and transduced cells from six mAPH and BM products each were infused into immunodeficient (NSG) mice at a target cell dose of 1x106 TNC per mouse. On average, the CD34+ cell dose per mouse for BM products was 2.86x104 CD34+ cells [stan- dard error of the mean (SEM)=6.67x103] and for mAPH products was 1.08x105 CD34+ cells (SEM=1.45×104). Flow cytometry analysis on peripheral blood was used to eval- uate engraftment (human CD45+) and lineage develop- ment into T cells (human CD3+), B cells (human CD20+),
Figure 2. In vitro repopulation potential restricted to CD34Hi hematopoietic cells. Mobilized leukapheresis from FA-A Patient 3 (Panel A) and a healthy donor (Panel B) were in parallel fluorescence stained with anti-CD34 antibody and sort-purified for CD34Hi and CD34Lo cells. Total nucleated cells (TNC) equivalent to 1500 CD34-expressing cells were seeded in CFC assays. Percentage of CD34+ cells seeded in the assay that gave rise to colonies is represented as the % of colony-forming cells.
A
B
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and monocytes (human CD14+) over time (Figure 4F). Both mAPH and BM products demonstrated long-term engraftment over 20 weeks of monitoring. Engraftment levels were comparable to results reported by Wiekmeijer et al. with CD34+ cells purified from BM and infused at similar cell doses.18
Lineage-depleted cell products xenoengraft equivalently to CD34-enriched products
In this experiment, healthy donor BM products were divided into two aliquots. One was lineage-depleted and the other CD34-enriched. Resulting cell populations were transduced with the same LV vector under identical condi- tions and infused into NSG mice at matched CD34+ cell doses. We observed higher CD34+ cell retention with lin- eage depletion compared to CD34 selection, with no dif- ferences in transduction efficiency or colony-forming potential (Figure 5A and B). We observed slightly higher, but not significantly different, levels of human CD45+ blood cell engraftment in mice receiving transduced, line- age-depleted cells relative to mice receiving CD34-select- ed cells. We also observed more stability of T- and B-cell engraftment in mice receiving lineage-depleted cell prod- ucts relative to mice receiving CD34-selected cell products (Figure 5C).
Lineage depletion protocol preserves limited FA CD34Hi cells
These data collectively suggest that lineage-specific depletion preserved available CD34+ cells without com- promising transduction efficiency or cell fitness. Under
FDA approval, the clinical protocol was modified to include both BM and/or mAPH products, with lineage depletion as the method of CD34+ cell enrichment. Patient 3 (the first treated under the modified protocol) was a 5- year old male with FA-A confirmed by complementation studies. Baseline neutrophils averaged 1.7x109/L and base- line platelets averaged 32x109/L in the six months prior to treatment, with declining neutrophils and platelets over the prior 2-year interval (Online Supplementary Figure S4). Mobilization of ≥10 CD34+ cells/mL peripheral blood was achieved (Online Supplementary Figure S5A), and two suc- cessive apheresis collections resulted in 8.5x1010 TNC con- taining a total 1.6x108 CD34+ cells (Table 2). The patient required a total of two platelet transfusions and two packed red blood cell transfusions during mobilization and leukapheresis (Online Supplementary Figure S5B). Due to column limitations, 5x1010 TNC (equivalent to 9.5x107 total CD34+ cells) were subjected to lineage depletion, and the remainder were cryopreserved. Lineage depletion resulted in a 94% reduction in TNC and a 56% retention of available CD34+ cells. CD34 purity was 1.6%, repre- senting a 1-2 log-fold increase in the total number of CD34+ cells per kg available for transduction and infusion relative to Patients 1 and 2 (Table 2). A total of 52.8x106 CD34+ cells were transduced at an MOI of 5 IU/cell, resulting in a final cell dose of 2.4x106 total CD34+ cells per kg with 99.3% viability based on trypan blue dye exclu- sion. Approximately 26% of CFCs in this cell product were transduced, displaying a mean VCN of approximate- ly 1 (0.9) (Table 3). Thus, limited numbers of available CD34+ cells were indirectly enriched using lineage deple-
Figure 3. Direct CD34 enrichment versus depletion of lineage positive (+) cells. Products can include bone marrow (BM) or mobilized apheresis product (mAPH) (1). BM products were first processed through hetastarch sedimentation to deplete red blood cells (RBCs). Leukapheresis products were first subjected to several washes to deplete platelets. For direct CD34+ cell selection, anti-CD34 antibody-bound immunomagnetic beads (microbeads) are used, whereas for lineage depletion anti- CD3+, CD14+, CD16+, and CD19+, microbeads are used (2). In both cases, microbead-bound cells are retained on the column and subjected to wash steps. When lin- eage depletion is used, CD34-expressing cells undergo minimal manipulation during purification. Following purification, cells are cultured and transduced with a VSV-G pseudotyped lentiviral vector at a multiplicity of infection (MOI) of 5–10 IU/ cell (3). Following ~16 hours of incubation cells are harvested (4). *These process- es were performed on the CliniMACS ProdigyTM device from Miltenyi Biotec GmbH.
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AB
CD
F
Figure 4. Multi-lineage engraftment of lineage depleted and transduced bone marrow (BM) and mobilized apheresis products (mAPH) in NSG mice. Recovery of total nucleated cells (TNC), CD34+ cells and lineage positive (+) cells (A and B). (C-E) Gene transfer efficiency. The colony-forming potential of transduced cells in standard CFC assays is defined as the plating efficiency (TNC). The colony-forming potential normalized to the number of CD34+ cells seeded is depicted as plating efficiency (CD34+). The percentage of colonies analyzed positive for the presence of lentivirus (LV) backbone by PCR analysis on DNA extracted from individual colonies is depicted as transduction efficiency. The vector copy number per cell in the bulk transduced population is depicted as VCN. The average VCN per cell in the individual CFC is depicted as single colony VCN. Data are representative of the average of 9 healthy BM products and 10 healthy mAPH products. Error bars rep- resent the standard error of the mean. (F) Engraftment of human CD45+ cells and lineage development into T cells (CD3+ ), monocytes (CD14+ ) and B cells (CD20+) was determined by flow cytometry over 20 weeks following infusion of lineage-depleted cell products. Data are representative of 36 mice from 6 mAPH donors and 42 mice from 6 BM donors, respectively. Error bars represent the Standard Error of the Mean.
tion on a blood product from an FA-A patient without compromising transduction efficiency.
Discussion
Here we confirm prior reports of inefficient CD34+ cell enrichment from FA patient blood products by direct, immunomagnetic bead-based separation, which is the current standard protocol for isolating HSPCs.15,19-21 We also demonstrate substantially reduced levels of CD34Hi cells in FA patients relative to healthy donors, which likely contributes to poor positive selection results in blood products from FA patients. Colony seeding assays demon- strate that only CD34Hi cells contribute to in vitro colony- forming potential in both FA and healthy donor blood products, underscoring the need to preserve as many available CD34+ cells as possible during ex vivo manipula- tion for gene transfer. We demonstrate a clinically viable procedure for depleting lineage positive cells to indirectly enrich for CD34+ cells that preserves the limited numbers of these cells in FA-A patients without compromising via- bility, gene transfer, or engraftment potential.
Importantly, the phenotype of limiting CD34+ cell num- bers is not restricted to FA alone. Sickle cell disease (SCD) patients treated with hydroxyurea also display reduced CD34+ cell frequencies in BM, and there is a contraindica- tion to mobilization of available CD34+ cells owing to an increased risk of vaso-occlusive crisis.22 Other inherited BM failure syndromes such as dyskeratosis congenita also
are associated with abnormal CD34+ cell frequencies and behavior.23 As a larger number of disease targets become relevant for gene therapy, additional patient populations will likely display variable CD34+ cell frequency and anti- gen expression. These disease targets could also benefit from clinically viable alternative selection procedures such as we have developed here.
Our observation of CFC potential in only the CD34Hi fraction in both FA and healthy samples suggests that CD34Lo cells may not be contributing to hematopoietic reconstitution. Notably, our data are from mAPH samples not BM, and we will need more patients for confirmation. Additionally, the standard colony-forming assay best defines progenitor cells, more so than true long-term repopulating hematopoietic stem cells.24 Alternatively, xenotransplant of purified cells into immunodeficient mice could provide the most robust evidence for CD34+ cell function in vivo, but the very small numbers of these cells may prove problematic to achieving relevant cell doses needed for these experiments. Another in vitro assay, such as the long-term culture-initiating cell assay,25 may provide additional insight into the desired target CD34+ subpopulations for gene therapy if they are present in either the CD34Hi or CD34Lo populations in FA patients. In this regard, we recently demonstrated that the CD34HiCD45RA–CD90+ phenotype is responsible for hematopoietic repopulation in non-human primates in the autologous, myeloablative setting,16 and evaluation of this phenotype in the enrolled FA patients is ongoing. Critically, our strategy of depleting cells expressing mature
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A
B
C
Figure 5. Multi-lineage engraftment levels of lineage-depleted cell products in NSG (NOD/SCID/IL2rgnull) mice is comparable to CD34-enriched cell products from the same donor. (A) Graph depicts percent recovery of total nucleated cells (TNC) and CD34+ cells from each arm following depletion or enrichment. (B) Numbers of total and transduced colony-forming cells (CFC) nor- malized to 1x108 cells processed to each arm, and vector copy number (VCN) in the bulk transduced cells following ten days of culture. Data are representative of 2 healthy donor bone marrow products. Error bars represent the Standard Error of the Mean. (C) Engraftment of human CD45+ cells and lineage development into T cells (CD3+), monocytes (CD14+) and B cells (CD20+) was determined by flow cytometry over 26 weeks following infusion. Data are representative of 9 mice for the lineage depleted (Lin-) arm and 6 mice for the CD34 enriched (CD34) arm, respectively.
Lin- CD34+
blood cell lineage markers preserves all CD34+ cell pheno- types for gene transfer and infusion, as demonstrated by Patient 3, whose infused CD34+ cell dose was the largest received to date.
One characteristic of lineage-depleted cell products requiring additional study is the presence and impact of other supporting cells on engraftment. Especially for BM- derived products, our procedure does not include a marker to deplete mesenchymal stem cells (MSC). While the engraftment potential of MSC manipulated ex vivo in CD34+ cell supportive media is unexplored, two recent reports suggest that these cells are integral to BM function in FA, and can be LV-transduced and functionally corrected to facilitate hematopoietic recovery and function in a mouse model of FA.26,27 For mAPH-derived products, such as that infused into Patient 3, additional follow up will be required to determine if a selective advantage is observed
in vivo. The improved transduction efficiency of lineage- depleted cell products could reflect non-repopulating CD34– cell uptake of LV. However, we still observed a ben- efit in transduction of hematopoietic CFC, even at the lower MOI of 5 IU/cell. One other possible explanation is the age and clinical condition of Patient 3. To address this concern we compared our results in Patient 3 to the 4 FA patients enrolled in the FANCOSTEM clinical trial in Spain (clinicaltrials.gov identifier: 02931071).28 These 4 patients were aged 3-7 years and demonstrated higher baseline blood cell counts at the time of collection. All 4 patients received the same mobilization regimen as Patient 3 reported here, but resulting mAPH products were subjected to direct CD34 enrichment prior to trans- duction at an MOI of 100 IU/cell. The reported mean VCN was 0.4±0.1 and ranged from 0.1 to 0.4 copies in individual CFC. Our data with a higher VCN at lower
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MOI suggest that the mixed cell culture supports trans- duction of hematopoietic progenitor cells, at least.
In conclusion, we describe an alternative strategy to a direct, immunomagnetic bead-based selection of CD34-expressing cells that overcomes current barriers in isolation of blood stem and progenitor cells especially for diseases like FA. Our novel approach to preserve available CD34+ cells during initial blood product processing has the potential to improve gene therapy and gene editing in set- tings of limited CD34+ cell availability, including FA and other diseases in which direct CD34 enrichment has proven inefficient, such as SCD.
Acknowledgments
We thank our patients and their families. We thank the Fanconi Anemia Research Fund for sponsoring patient travel and housing arrangements associated with this study. We especially thank the Fred Hutch Cell Processing Facility and Seattle Cancer Care Alliance for their support in enrollment and treatment of clinical trial patients. We thank H. Crawford and K. Gonzalez for help in preparing the manuscript. We
also thank J. Chen and C. Ironside for excellent support in our mouse studies. This work was primarily funded by a Sponsored Research Agreement between Fred Hutch and Rocket Pharmaceuticals.
Funding
This work was also supported in part by grants and contracts to H-PK from the NIH HHSN2680004 and HL122173 and by funds to JEA from the Fred Hutch. This research was also funded in part through the NIH/NCI Cancer Center Support Grant P30 CA015704. H-PK is a Markey Molecular Medicine Investigator and received support as the inaugural recipient of the José Carreras/E. Donnall Thomas Endowed Chair for Cancer Research and the Fred Hutch Endowed Chair for Cell and Gene Therapy. JEA and H-PK are co-inventors on U.S. Provisional Patent Applications #62/491,116 and #62/503,801 “Novel Manufacturing of Gene Corrected Autologous Blood Cells for Gene Therapy.” JEA has previously served as a consultant for Rocket Pharmaceuticals. H-PK is an active consultant for Rocket Pharmaceuticals. The other authors declare that they have no competing interests.
References
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4. Asur RS, Kimble DC, Lach FP, et al. Somatic mosaicism of an intragenic FANCB duplica- tion in both fibroblast and peripheral blood cells observed in a Fanconi anemia patient leads to milder phenotype. Mol Genet Genomic Med. 2018;6(1):77-91.
5. Gregory JJ, Jr., Wagner JE, Verlander PC, et al. Somatic mosaicism in Fanconi anemia: evidence of genotypic reversion in lympho- hematopoietic stem cells. Proc Natl Acad Sci USA. 2001;98(5):2532-2537.
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mia complementation group A bone mar- row cells using a safety-modified lentiviral vector. Gene Ther. 2010;17(10):1244-1252.
10. Syrjala M, Ruutu T, Jansson SE. A flow cyto- metric assay of CD34-positive cell popula- tions in the bone marrow. Br J Haematol. 1994;88(4):679-684.
11. Collins RH Jr. CD34+ selected cells in clinical transplantation. Stem Cells. 1994; 12(6):577- 585.
12. Spohn G, Wiercinska E, Karpova D, et al. Automated CD34+ cell isolation of peripher- al blood stem cell apheresis product. Cytotherapy. 2015;17(10):1465-1471.
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Mobilization and collection of peripheral blood CD34+ cells from patients with Fanconi anemia. Blood. 2001;98(10):2917- 2921.
21. Larghero J, Marolleau JP, Soulier J, et al. Hematopoietic progenitor cell harvest and functionality in Fanconi anemia patients. Blood. 2002;100(8):3051.
22. Uchida N, Fujita A, Hsieh MM, et al. Bone marrow as a hematopoietic stem cell source for gene therapy in sickle cell disease: Evidence from rhesus and SCD patients. Hum Gene Ther Clin Dev. 2017;28(3):136-
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in the hay stack: hematopoietic stem cells in Fanconi anemia (Review). Mutat Res. 2009;668(1-2):141-149.
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16. Radtke S, Adair JE, Giese MA, et al. A dis- tinct hematopoietic stem cell population for rapid multilineage engraftment in nonhu- man primates. Sci Transl Med. 2017; 9(414).
17. Adair JE, Waters T, Haworth KG, et al. Semi- automated closed system manufacturing of lentivirus gene-modified haematopoietic stem cells for gene therapy. Nat Commun. 2016;7:13173.
18. Wiekmeijer AS, Pike-Overzet K, Brugman MH, et al. Sustained engraftment of cryopre- served human bone marrow CD34(+) cells in young adult NSG mice. Biores Open Access. 2014;3(3):110-116.
19. Liu JM, Kim S, Read EJ, et al. Engraftment of hematopoietic progenitor cells transduced with the Fanconi anemia group C gene (FANCC). Hum Gene Ther. 1999;
23. Balakumaran A, Mishra PJ, Pawelczyk E, et al. Bone marrow skeletal stem/progenitor cell defects in dyskeratosis congenita and telomere biology disorders. Blood. 2015; 125(5):793-802.
24. Coulombel L. Identification of hematopoiet- ic stem/progenitor cells: strength and draw- backs of functional assays. Oncogene. 2004;23(43):7210-7222.
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Prognostic factors of Erdheim–Chester disease: a nationwide survey in Japan
Takashi Toya,1* Mizuki Ogura,1* Kazuhiro Toyama,2 Akihide Yoshimi,1
Aya Shinozaki-Ushiku,3 Akira Honda,1 Kenjiro Honda,4 Noriko Hosoya,5 Yukako Murakami,6 Hiroyuki Kawashima,7 Yasuhito Nannya,1 Shunya Arai,1 Fumihiko Nakamura,1 Yusuke Shinoda,8 Masaomi Nangaku,4
Kiyoshi Miyagawa,5 Masashi Fukayama,3 Akiko Moriya-Saito,9
Ichiro Katayama,6 Takashi Ogura10 and Mineo Kurokawa1,2
*TT and MO contributed equally to this work
ABSTRACT
Erdheim–Chester disease is a rare histiocytosis with insufficient clin- ical data. To clarify the clinical features and prognostic factors of Erdheim–Chester disease, we conducted a nationwide survey to collect the detailed data of 44 patients with Erdheim–Chester disease in Japan. The median age of onset of the participants was 51 (range: 23–76) years, and the median number of involved organs per patient was 4 (range: 1–11). The existence of central nervous system disease was corre- lated with older age (P=0.033), the presence of cardiovascular lesions (P=0.015), and an increased number of involved organs (P=0.0042). The median survival from the onset was 10.4 years, and >3.0 mg/dL C-reac- tive protein level at onset was associated with worse outcome (median survival, 14.6 vs. 7.4 years; P=0.0016). In a multivariate analysis, age >60 years (hazard ratio, 25.9; 95% confidence interval, 2.82–237; P=0.0040) and the presence of digestive organ involvement (hazard ratio, 4.74; 95% confidence interval, 1.05–21.4; P=0.043) were correlated with worse sur- vival. Fourteen patients had available histological samples of Erdheim– Chester disease lesions. BRAFV600E mutation was detected in 11 patients (78%) by Sanger sequencing. A correlation between BRAF mutation sta- tus and clinical factors was not observed. Our study revealed that age and digestive organ involvement influence the outcome of Erdheim–Chester disease patients, and an inflammatory marker, such as C-reactive protein, might reflect the activity of this inflammatory myeloid neoplasm.
Introduction
Erdheim–Chester disease (ECD) is a rare non-Langerhans histiocytosis that was first reported by Jakob Erdheim and William Chester in 1930.1 The number of reports has drastically increased recently, perhaps due to the increased recognition of the disease, and approximately 650–1000 cases have been reported.2-4 ECD typ- ically develops among middle-aged males, and bilateral cortical osteosclerosis occurs in more than 95% of ECD patients.5 Furthermore, some patients experience involvements of the central nervous system (CNS), cardiovascular system, and var- ious other organs.6,7
Ferrata Storti Foundation
1Department of Hematology & Oncology, Graduate School of Medicine, The University of Tokyo; 2Department of Cell Therapy and Transplantation Medicine, The University of Tokyo Hospital; 3Department of Pathology, Graduate School of Medicine, The University of Tokyo; 4Division of Nephrology and Endocrinology, The University of Tokyo Graduate School of Medicine; 5Laboratory of Molecular Radiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo; 6Department of Dermatology, Osaka University Graduate School of Medicine; 7Division of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Sciences; 8Department of Rehabilitation Medicine Graduate School of Medicine, The University of Tokyo; 9Clinical Research Center, National Hospital Organization Nagoya Medical Center, Aichi and 10Department of Respiratory Medicine, Kanagawa Cardiovascular and Respiratory Center, Yokohama, Japan
Haematologica 2018 Volume 103(11):1815-1824
Correspondence:
kurokawa-tky@umin.ac.jp
Received: February 8, 2018. Accepted: July 4, 2018. Pre-published: July 5, 2018.
doi:10.3324/haematol.2018.190728
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1815
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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The pathogenesis of ECD is still unclear, and whether this condition is a type of neoplasia or inflammation is a topic of debate. The high prevalence of mutations in BRAF, NRAS, and various genes involved in the MAPK pathway and the dramatic efficacy of BRAF inhibitors suggest the important role played by the BRAF and MAPK pathways in ECD development.8-11 Recently, Haroche et al. speculated that ECD could be redefined as “inflammatory myeloid neoplasia”, similar to Langerhans cell histiocyto- sis (LCH).2,12 A mouse model of LCH showed that genetic mutations in hematopoietic stem cells or immature myeloid progenitors induce misguided differentiation, and increase in pathological dendritic cells, which recruit and activate additional inflammatory cells (so-called “innocent bystanders”).13 Cavalli et al. suggested the significance of oncogene-induced senescence (OIS), a protective reaction against oncogenesis, in the recruitment of circulating nor- mal leukocytes in ECD lesions.14,15 In the context of ECD, the local production of pro-inflammatory chemokines and Th1-associated cytokines by BRAFV600E mutated cells attracts circulating normal leukocytes to the sites and con- tributes to the inflammatory activation and formation of ECD. Further basic studies are warranted to investigate the exact mechanisms of ECD.
The clinical course of ECD is quite heterogeneous, but most cases are progressive and become fatal within a few years. Little is known about the prognostic factors of ECD except that of the involvement of CNS.16 ECD diagnosis is mainly dependent on pathological findings, such as CD68+CD1a− foamy histiocyte infiltration, but the con- sensus guidelines also demand the clinical and radiological contexts for an appropriate diagnosis of the disease.5 However, our knowledge about the clinical profiles of ECD is unsatisfactory, and more information to consoli- date this “context” is required.
Herein, we conducted a nationwide survey on ECD in Japan and clarified some clinical features of this disease. Strikingly, the poor outcome observed among elderly patients and the prognostic impact of digestive organ involvement encouraged the spread of novel treatment strategies, such as vemurafenib, or other molecular target- ed therapies.17 Additionally, the prognostic value of the increased C-reactive protein (CRP) level at onset suggested the significance of the inflammatory nature of ECD patho- physiology.
Methods
Study design and participants
We conducted a postal questionnaire-based, multicenter retro- spective study on ECD. A questionnaire was simultaneously sent to the hematology, dermatology, respiratory medicine, orthope- dics, and pathology departments of the involved hospitals in Japan in July 2014, which were certified by each Japanese society. All cases were diagnosed according to the histopathological findings consistent with ECD, which typically contain infiltration of foamy or lipid-laden histiocytes and which were positive for CD68, CD163 and negative for CD1a and Langerin on immunohisto- chemical staining. The questionnaire was also sent to hospital departments containing a member who published a paper or pre- sented at an academic conference on ECD cases. The samples of the ECD lesions from the peripheral blood and/or bone marrow were also collected, if available. This study was performed in accordance with the Declaration of Helsinki and the Ethical
Guidelines for Biomedical Research Involving Human Subjects enforced on March 29, 2001. This study was approved by the ethics committees of the University of Tokyo and each participat- ing institution. Written informed consent was obtained from all patients whose ECD samples were collected. No definitive diag- nostic criteria for ECD have been published; therefore, the diag- noses were self-reported by each institute based on the patholog- ical, radiological, and clinical findings. The digestive organ means gastrointestinal tract plus the accessory organs of digestion (the pancreas, liver, and gallbladder).
Mutation analysis
Genomic DNA was extracted from each formalin-fixed, paraf- fin-embedded tissue and peripheral blood specimen using the QIAamp DNA FFPE Tissue Kit and DNA Mini Kit (Qiagen, Hilden, Germany), respectively. Polymerase chain reaction (PCR) for the detection of BRAF V600E mutation was performed using primers (TACCTAAACTCTTCATAATGCTTGC, GTAACTCAGCAGCATCTCAGGG) as previously reported.18 The products were purified with Illustra ExoStar (GE Healthcare, Tokyo, Japan), and Sanger sequencing was conducted using the BigDye Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems, Foster City, CA, USA) and the ABI Prism 3100 Genetic Analyzer (Life Technologies, Carlsbad, CA, USA).
Statistical analysis
The numerical and categorical variables were compared using the t-test and Fisher’s exact test, respectively. Three patients diag- nosed at autopsy were excluded from the analyses of the interval from onset to diagnosis. The survival time was calculated through the Kaplan–Meier method, and the log-rank test was utilized for the evaluation of the significant differences. The effect of various parameters on survival was evaluated through univariate and mul- tivariate analyses with the use of the Cox proportional hazards regression model. ECD-related death was defined as death associ- ated with ECD (such as heart failure due to cardiac involvement and increased intracranial pressure caused by brain mass etc.). The cumulative incidence of ECD-related death was calculated in a competing risks model. The factors with P<0.05 in the univariate analyses were included in the multivariate analysis of the survival. Hazard ratio (HR) was estimated with 95% confidence intervals (CI), and the respective P values were reported from these analy- ses. Differences were considered statistically significant at P values <0.05. Statistical analyses were performed using R version 3.3.2 (The R Foundation for Statistical Computing, Vienna, Austria).
Results
Patient characteristics and affected organs
The questionnaire was sent to 3850 departments, of which 52% (2007 departments) responded. We confirmed that in Japan 75 patients have ECD, and detailed data were collected from 45 patients. One patient was exclud- ed from the analyses because of insufficient pathological validity. Table 1 shows the clinical characteristics of the remaining 44 patients. The first signs of the disease are described in Online Supplementary Table S1. The median age at initial onset was 51 (range: 23–76) years. Among the 44 patients, 28 were males (63.6%) and 16 were females (36.4%). Five, eight, nine, and 22 patients were diagnosed before 1999, between 2000 and 2004, between 2005 and 2009, and after 2010, respectively. No association between time of diagnosis and clinical features, other than treat- ment choice, was observed. Three patients were diag-
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nosed at autopsy or after death, and the median and mean time from onset to diagnosis was 12 (range: 1–89) and 20.7 months (Online Supplementary Figure S1). No significant difference between interval from onset to diagnosis and presence of organ involvement, age, year of diagnosis, and any other clinical features were detected.
Table 1. Clinical characteristics of ECD patients Characteristics
Sex (male–female)
Median age at onset, y (range) Median age at diagnosis, y (range) Mean time for diagnosis, m (range) Year of diagnosis, no. (%)
Before 2000 2000–2004 2005–2009 2010 and later
Coexistence of LCH, no. (%)
Median number of involved organs (range) Skeletal involvement, no. (%)
Bone pain
CNS involvement, no. (%)
Parenchymal brain mass Exophthalmos
Meningeal involvement
Without any radiological findings
Cardiovascular involvement, no. (%) Cardiac involvement
Aortitis
Retroperitoneal involvement, no. (%)
Hydronephrosis
Hairy kidney
Endocrine involvement, no. (%)
Diabetes insipidus
Pituitary tumor without diabetes insipidus Hypothyroidism
Cutaneous involvement, no. (%)
Xanthelasma
Other
Pulmonary involvement, no. (%)
Pleural thickening
Fibrosis
Interlobular septal thickening Centrilobular shadow
Digestive involvement, no. (%)
Pancreas
Liver Gastrointestinal Gallbladder
CRP at onset (mg/dL), median (range)
All patients (n = 44)
28–16
51 (23–76) 53 (23–77) 20.7 (1–89)
5 (11.4) 8 (18.2) 9 (20.5) 22 (50.0) 4 (9.1)
4 (1–11) 38 (86.4) 22
22 (50.0) 12
6
4
2
23 (52.3) 19
11
22 (50.0) 10
8
18 (40.9) 15
2
1
18 (40.9) 11
7
15 (34.1)
5
3
2
1
6 (13.6)
3
2
2
1
2.61 (0.1–14.1)
15 (34.1) 25 (56.8) 5 (11.4) 5 (11.4) 4 (9.1) 1 (2.3) 2 (4.5) 1 (2.3) 1 (2.3) 1 (2.3) 1 (2.3) 10 (22.7 1 (2.3)
Fifteen patients (33.3%) were treated with interferon a (IFN-a) or pegylated IFN. Twenty-five patients (57.8%) were administered with corticosteroid. Patients who were diagnosed after 2005 were more frequently administered IFN than those diagnosed before 2005 (43.8% vs. 7.7%, P=0.034). No patient was administered with vemurafenib or other BRAF inhibitors.
The median number of involved organs per patient was four (range: 1–11). The lesions were mainly found in the bone (86.4%), the CNS (50.0%), the cardiovascular sys- tem (52.3%), the kidney and retroperitoneal organs (50.0%), the endocrine organs (40.9%), the skin (40.9%), the lungs (34.1%), and the digestive organs (13.6%). Oropharyngeal lesions in three patients (6.8%), lym- phadenopathy in three patients (6.8%), splenomegaly in two patients (4.5%), and breast lesions in two patients (4.5%) were also detected. In one patient, the testes, prostate, bladder, spinal cord, glottis, and bone marrow were also affected. These unusually affected organs were exclusively observed in patients with multiple (three or more) lesions and, in many cases, who were diagnosed at autopsy. Thirty-eight patients had skeletal lesions, of which 22 had bone pain. Four patients (9.1%) had simul- taneous or heterochronic LCH lesions. No patient was diagnosed as having immunoglobulin (Ig)G4-related dis- ease as the clinical and pathological findings did not corre- spond to the disease, although specific examinations such as serum IgG-4 levels and immunohistochemistry for IgG4 were not carried out on the majority of patients. Among the 18 patients with endocrine involvement, 15 had diabetes insipidus (DI), two had pituitary tumors without obvious DI and one had hypothyroidism. Twenty-three patients had cardiovascular involvement including 19 with cardiac involvement and 11 with aortitis (seven had both). Among the 22 patients with CNS involvement, six had exophthalmos, 12 had parenchymal brain mass and four had meningeal involvement. Two patients had no radiological finding of CNS but their neu- rological symptoms (delirium and cerebellar ataxia) were considered to be symptoms of ECD.
In addition, one patient had low-risk myelodysplastic syndrome (MDS) prior to ECD. He did not receive any treatment for MDS and one year later, after the detection of an abnormal pulmonary shadow, ECD was diagnosed through partial pneumonectomy. The shadow shrank after cyclosporine and prednisolone therapy, but he died of pneumonia 4.5 years after the ECD diagnosis.
Survival
The median follow-up period of survivors was 5.17 (range: 1.0–21.1) years. Eighteen out of 44 patients died during the clinical course of their illness, and the cause of death was associated with ECD in 13 patients (72.2%, Online Supplementary Table S2). Moreover, two other patients died from infection, possibly due to the use of corticosteroid therapy as a treatment for ECD.
The median survival from the initial onset, which was determined using the Kaplan–Meier method, was 10.42 years (Figure 1A). The log-rank test results revealed that
Treatments, no. (%)
IFN a or PEG-IFN Corticosteroid Irradiation Imatinib mesylate Cyclophosphamide Cladribine Etoposide Cyclosporine Prostaglandin I2 CHOP
JLSG-02 Bisphosphonate Lung transplantation
ECD: Erdheim–Chester disease; LCH: Langerhans cell histiocytosis; CNS: central nerv- ous system; CRP: C-reactive protein; IFN-a: interferon a; PEG: pegylated; CHOP: cyclophosphamide, adriamycin, vincristine, and prednisolone; JLSG-02: a regime protocol for LCH consisting of cytarabine, vincristine, and prednisolone.
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the prognostic factors for this disease were age >60 years old at the onset (P<0.0001), lack of bone lesions (P<0.0001), and the involvement of the CNS (P=0.0010) and digestive organs (P=0.017) (Figure 1B-E). In contrast, the presence of cardiovascular disease, endocrinosis, and pulmonary, kidney/retroperitoneal and cutaneous lesions was not considered as a prognostic factor (Online
Supplementary Figure S2). Patients with only one ECD lesion, all of whom had a bone lesion, tended to have bet- ter survival after the onset of the disease than those with multiple lesions, although this difference was not statisti- cally significant, perhaps because the number of patients who had a single lesion was only five (P=0.064).
The univariate analyses, which were conducted using
AB
C
D
E
Figure 1. Survival curves of patients with Erdheim–Chester disease. Kaplan– Meier estimation for survival from onset of (A) all 44 patients based on (B) age and presence of (C) bone lesions, (D) central nervous system involvement, and (E) digestive involvement. CNS: central nervous system; DO: digestive organ.
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Cox proportional hazards regression model, revealed that age >60 years (P=0.00035), the presence of CNS involve- ment (P=0.0021) and digestive organ disease (P=0.0022), and the absence of bone lesions (P=0.0042) were signifi- cant poor prognostic factors for survival from the onset (Table 2). Sex, year of diagnosis, and existence of cardio- vascular, endocrine, cutaneous, or pulmonary involve- ment and kidney/retroperitoneal lesions did not have an effect on survival.
Table 2. Univariate and multivariate analyses for survival.
The multivariate analysis showed that age >60 years (HR, 25.9; 95% CI, 2.82–237; P=0.0040) and the presence of digestive organ involvement (HR, 4.74; P=0.043) were correlated with worse survival.
ECD-related death
Next, we analyzed the association between the cumula- tive incidence of ECD-related death and clinical factors (Figure 2A-D). ECD-related death was significantly associ-
Age, years
Sex
Year of diagnosis
Skeletal involvement
CNS involvement
Cardiovascular involvement
Retroperitoneal involvement
Endocrine involvement
Cutaneous involvement
Pulmonary involvement
Digestive involvement
≥ 60 15
<6029 1 Male 28 0.52
No. of patients
Univariate analysis
P
Multivariate analysis HR (95% CI)
P
0.0040
0.20 0.083
0.00035
25.9 (2.82–237)
Female 16
Before 2005
2005 or later 31
13 0.38
Yes 38 0.0042
No 6
Yes 22 0.0021
No22
Yes 23 0.14
No 21
Yes 22 0.58
No 22
Yes 18 0.86
No 26
Yes 18 0.77
No 26
Yes 15 0.94
No 29
Yes 6 0.0022
1
2.16 (0.660–7.09) 3.63 (0.844–15.6) 1
CNS: central nervous system; HR: hazard ratio; CI: confidence interval.
Table 3. Skeletal involvement and clinical factors. Characteristics
Sex (male–female)
Median age at onset, y (range)
Diagnosed after 2005, no. (%)
Coexistence of LCH, no. (%)
Median number of involved organs (range) CNS involvement, no. (%)
Cardiovascular involvement, no. (%) Retroperitoneal involvement, no. (%) Endocrine involvement, no. (%)
Diabetes insipidus, no. (%) Cutaneous involvement, no. (%) Pulmonary involvement, no. (%) Digestive involvement, no. (%)
CRP at onset (mg/dL), median (range)
Skeletal (−) (n = 6)
3–3
59 (40–67)
2 (33.3)
0 (0)
3 (2–8)
5 (83.3)
3 (50.0)
3 (50.0)
3 (50.0)
1 (16.7)
4 (66.7)
1 (16.7)
1 (16.7)
5.38 (3.30–7.46)
Skeletal (+) (n = 38)
25–13
49 (23–76) 29 (76.3)
4 (11.1)
4 (1–11)
17 (44.7)
20 (52.6)
19 (50.0)
15 (39.5)
14 (36.8)
14 (36.8)
14 (36.8)
5 (13.2) 2.45 (0.10–14.1)
P
0.65
0.43 0.053 1 0.77 0.19 1 1 0.68 0.65 0.21 0.65 0.56 0.49
No38 1
4.74 (1.05–21.4)
0.043
LCH: Langerhans cell histiocytosis; CRP: C-reactive protein; CNS: central nervous system.
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ated with age >60 years (P<0.0001), digestive organ (P<0.0001), CNS (P=0.0062), and skeletal involvement (P=0.0072). Cardiovascular (P=0.071), cutaneous (P=0.26), retroperitoneal (P=0.27), respiratory (P=0.28), endocrine involvement (P=0.83) and sex (P=0.89) were not signifi- cantly associated with ECD-related death.
ECD without skeletal lesion
Considering that the prevalence of skeletal lesions in our study was relatively low compared with that of previous studies in Western countries (>95%),5,19 we compared the clinical data of ECD patients with and without skeletal lesions. No obvious clinical difference based on skeletal involvement was observed, except that patients with skeletal lesions had a better outcome than those without (Figure 1C and Table 3).
ECD with digestive involvement
Given that ECD with digestive involvement was associ- ated with worse survival, we examined the characteristics of ECD patients with digestive disease (Table 4). The digestive organs concerned were the liver (50.0%), pan- creas (50.0%), gastrointestinal tract (33.3%), and gallblad- der (16.7%). Causes of death were arrhythmia in one patient with cardiac tamponade, heart and renal failure in
one patient with pericardial effusion and hydronephrosis, sepsis due to rectal perforation in one patient with gas- trointestinal involvement of ECD, and ECD (details unknown) in one patient. An autopsy was carried out in four patients who died during the clinical course of diges- tive disease, and the involvement of ECD cells was histo- logically proven. Histological samples were available in two patients and both were BRAFV600E positive.
No correlation was found between the existence of digestive organ disease and the CRP level at onset (P=0.99), age at onset (P=0.11), sex (P=0.39), year of diag- nosis (P=1), and the presence of specific organ involve- ment.
CNS involvement and associated clinical factors
Considering that the CNS was revealed to be a “risk organ”, based on the result of our analysis and that of a previous study,16 we compared the characteristics of patients with and without CNS disease to determine those were are at risk of CNS involvement (Table 5). Patients with CNS disease displayed significantly higher age at onset than those without (median, 62 [range, 23–76] years vs. 45 [range, 25–70] years; P=0.033). Additionally, the existence of CNS involvement was correlated with the presence of cardiovascular lesions (P=0.015). No statisti-
AB
C
D
Figure 2. Cumulative incidence of ECD-related death. Competing risks models revealed the cumulative incidence of ECD-related death based on (A) age and pres- ence of (B) digestive organs, (C) CNS, (D) skeletal involvement. DO: digestive organ; CNS: central nervous system.
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cally significant association between the presence of CNS involvement and sex (P=0.75), year of diagnosis (P=1.0), and existence of bone (P=0.19) and skin lesions (P=0.36), endocrinosis (P=0.12), pulmonary (P=0.20) and digestive organ involvement (P=0.66), or kidney/retroperitoneal dis- ease (P=0.13) was detected.
CRP level and outcome
The CRP level at onset was higher than the upper nor- mal limit in 29 (85.3%) out of 34 patients with sufficient laboratory data, with a median CRP level at onset of 2.61 mg/dL (range: 0.10–14.1). Interestingly, a >3.0 mg/dL CRP level at onset was associated with a worse outcome (median survival, 14.6 vs. 7.4 years; P=0.016; Figure 3A). The cumulative incidence of ECD-related death was also associated with a higher CRP level at onset (P=0.043; Figure 3B). We also compared the CRP level at onset with that after the administration of first-line therapy in 25 patients whose clinical data were available. The results of the Wilcoxon signed-rank test revealed that CRP levels tended to decline following the initial treatment (median at onset and after initial therapy: 2.38 [range, 0.10–14.1] mg/dL and 1.16 [range, 0.01–34.6] mg/dL, respectively; P=0.051; Figure 3C). In addition, patients whose CRP lev- els reduced by more than 2.0 mg/dL after first-line therapy had a better outcome compared with patients whose CRP levels dropped by less than 2.0 mg/dL or increased after first-line treatment (median survival, 11.3 vs. 7.4 years; P=0.045) (Figure 3D).
BRAFV600E mutation
Thirteen patients had available histological samples on
ECD lesions (Online Supplementary Table S3). The genomic DNA was extracted from the samples, which were then subjected to direct sequencing. A BRAFV600E mutation was detected in 11 out of 14 patients (78%). None of the BRAF mutations were detected through Sanger sequenc- ing of the genomic DNA extracted from the peripheral blood or bone marrow samples. Moreover, no correlation between BRAF mutation status and age, CRP level at onset, and other clinical factors were observed.
Discussion
Our nationwide study broadly investigated ECD patients and analyzed the clinical data of 44 patients. ECD is so rare that few reports on multiple ECD patient studies have been published and little evidence about the clinical characteristics or prognostic factors of this disease is avail- able. The study herein is one of the largest in terms of the number of patients with ECD involved in our research.2,6,7,16 In this study, the duration between onset and diagnosis seems to be shorter compared with previ- ous studies, in which many patients were diagnosed sev- eral years after initial onset. It might reflect an increased familiarity with ECD in recent years, although the exact reason is unclear.20 IFN has recently been recommended as first-line therapy, and BRAF inhibitors are also strong can- didates for the treatment of ECD.5,16,21 In our study, IFN was administered to a very small proportion of patients during the clinical course of the disease, and no patients received BRAF inhibitors, which is partially attributed to the Japanese insurance system. Instead, many patients were prescribed corticosteroid, which is believed to tem- porarily alleviate the symptoms, although it is not recom- mended by the consensus guidelines.5 Two patients died from infection (one pneumonia and one invasive pul- monary aspergillosis), possibly due to immunosuppres- sion induced by corticosteroid administration for the treatment of ECD. In our study, the mortality rate was rel- atively high compared with a recent report which showed a five year survival rate of 82.7 %.4 However, the outcome in our cohort was slightly better than that in patients who were not administered IFN in a previous report,16 perhaps due to the improvement of supportive care. To improve the prognosis of patients with ECD, more detailed analy- ses and prospective studies of the pathophysiology of ECD are required. Given that future studies on ECD may not include patients who were not administered with IFN and/or BRAF inhibitors, this study could serve as an important physician’s compass that reveals the baseline clinical behaviors of ECD.
CNS involvement was a significant poor prognostic fac-
Digestive (+) (n=6) P 5–1 0.39
66 (46–68) 0.11 4 (66.6) 1 0 (0) 1
8 (3–11)
5 (83.3) 1 4 (66.7) 0.66 1 (16.7) 1 4 (66.7) 0.67 5 (83.3) 0.19 3 (50.0) 0.68 2 (33.3) 1 3 (50.0) 0.39
Table 4. Digestive involvement and clinical factors. Characteristics
Sex (male–female)
Median age at onset, y (range)
Diagnosed after 2005, no. (%)
Coexistence of LCH, no. (%)
Median number of involved organs (range) Skeletal involvement, no. (%)
CNS involvement, no. (%) Exophthalmos, no. (%)
Cardiovascular involvement, no. (%) Retroperitoneal involvement, no. (%) Endocrine involvement, no. (%) Cutaneous involvement, no. (%) Pulmonary involvement, no. (%)
CRP at onset (mg/dL), median (range)
Digestive (−) (n=38)
23–15
49 (23–76) 27 (71.1) 4 (11.1) 3 (1–7) 33 (91.7) 18 (47.4) 5 (13.2) 19 (50.0) 17 (44.7) 13 (34.2) 16 (42.1) 12 (31.6)
2.52 (0.10–14.1)
0.015
2.70 (0.13–7.46) 0.99
LCH: Langerhans cell histiocytosis; CRP: C-reactive protein; CNS: central nervous system.
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tor in our series, which seems to be consistent with the previous study reporting that CNS involvement was asso- ciated with resistance to IFN.16 Our study revealed that ECD patients with CNS lesions were significantly older and had cardiovascular lesions more frequently. These fac- tors might affect the efficacy of IFN, as a cardiovascular lesion has also been suggested to contribute to the ineffec- tiveness of IFN therapy.22 Furthermore, the side effects of IFN, such as delirium, is known to be more frequently observed in older patients than in younger ones, despite intense psychiatric support.23 Future study is necessary to identify patients who are expected to benefit the most from treatment with IFN.
The prevalence of affected organs, median age at onset and male predominance were roughly comparable with that of previous reports in Western countries,5,7 excepting the article by Cavalli et al. which found that CNS manifes- tations in younger patients are relatively common,7 and the fact that the percentage of patients with skeletal dis- ease in our cohort was relatively low.5 The coexistence of LCH was also relatively rare in our series. Considering the close relationship between ECD and LCH, perhaps some
cases were overlooked.24 This dissociation might be attrib- uted to coincidence, ethnicity, or other genetic/epigenetic diversity. No statistically significant clinical difference was found between ECD patients with and without bone involvement, which suggests that ECD cases have com- mon features regardless of this factor. We were unable to obtain evidence that demonstrates whether ECD without bone lesions should be classified as a distinctive entity.
The digestive organ was detected as a risk organ for patients with ECD in this study. The prognostic impact of digestive involvement was not found in previous reports,5,6 perhaps due to the small number of patients with digestive ECD lesions. Although the liver and pan- creas were the most commonly affected organs, none of these patients with hepatic/pancreatic involvements suf- fered from the relevant organ failure. Four of six patients with digestive organ involvement died of ECD, however, only one patient died of rectal perforation due to ECD involvement and the other three patients died of other affected organs. A further accumulation of cases is neces- sary in order to confirm the prognostic impact of digestive involvement.
AB
CD
Figure 3. C-reactive protein (CRP) at onset and clinical outcome. (A) Kaplan–Meier estimation for survival from onset and (B) the cumulative incidence of ECD-related death of 34 patients with sufficient clinical data. (C) Comparison of the CRP level before and after administration of first-line therapy. (D) Kaplan–Meier estimation for survival from onset according to the decline of CRP levels after first-line therapy.
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The CRP level was elevated in many patients with ECD, and declined after IFN or vemurafenib treatment,8,22 simi- lar to the finding in our cohort. In this study, we firstly revealed that the CRP level at onset as well as the drop in CRP levels after initial therapy predict the patient out- come. We have to interpret this result with caution because initial treatments in our cohort were quite hetero- geneous and most of them were not standard therapy. Recently, ECD has been considered as an inflammatory myeloid neoplasm. Although the MAPK pathway and other mutations, such as PIK3CA, tend to attract attention to the neoplastic aspect of the disease, the association between CRP levels and poor prognosis evokes the neces- sity of vigorous research on the inflammatory characteris- tic of Janus-faced ECD because these mutations them- selves do not necessarily induce elevated CRP. Some inflammatory markers, such as interleukin (IL)-1, IL-6 and tumor necrosis factor, have also been reported as activa- tion markers of ECD.25-28 However, CRP levels are relative- ly easy to measure compared with inflammatory cytokines and might be suitable as a convenient marker to detect patients at risk.
Interestingly, low-risk MDS and ECD coexisted in one patient in our cohort. Papo et al. reported that adult histi- ocytic neoplasms frequently co-occur with other myeloid neoplasms (9.5%), and MAPK pathway-associated muta-
tions (BRAF, NRAS, and other mutations) could coexist with MDS-associated mutations (IDH1/2, ASXL1, and TET2 mutations) in the hematopoietic stem/progenitor cells of ECD patients.29 Unfortunately, we were unable to acquire a sample from the patient, and the genetic infor- mation was unavailable.
Due to the retrospective nature of our study, we could not analyze some of the most important clinical informa- tion of many of the patients, such as osteosclerosis of the sinuses and BRAF or other mutations.30 It is now mandato- ry to systematically collect clinical findings, radiological and laboratory data, and above all histological samples for patients with ECD. A more sophisticated method of detec- tion for the BRAF mutation is also warranted. Sanger sequencing is a classic method and still plays an important role in detecting ECD, partially owing to its low cost and convenience. However, immunohistochemistry for the BRAF V600E protein and hypersensitive methods, such as droplet digital PCR and/or targeted sequencing techniques, are becoming crucial because only a small fraction of cells in an ECD lesion actually harbor the BRAF mutation, and some studies have reported that a BRAF mutation in the peripheral blood could only be detected with ultrasensitive techniques as opposed to Sanger sequencing.15
In summary, our nationwide survey revealed the clinical characteristics of patients with ECD, and clarified the
Table 5. CNS involvement and clinical factors. Characteristics
Sex (male–female)
Median age at onset, y (range)
Diagnosed after 2005, no. (%)
Coexistence of LCH, no. (%)
Median number of involved organs (range) Skeletal involvement, no. (%) Cardiovascular involvement, no. (%) Retroperitoneal involvement, no. (%) Endocrine involvement, no. (%) Cutaneous involvement, no. (%) Pulmonary involvement, no. (%)
Digestive involvement, no. (%)
CRP at onset (mg/dL), median (range)
CNS (−) (n=22)
13–9
45 (25–70) 16 (72.7)
2 (9.1)
3 (1–8)
21 (95.5)
7 (31.8)
8 (36.4)
6 (27.3)
11 (50.0)
5 (22.7)
2 (9.1) 1.37 (0.10–14.1)
5 (22.7) 8 (36.4) 4 (18.2) 2 (9.1) 3 (13.6) 0 (0)
0 (0)
0 (0)
1 (4.5)
0(0)
0 (0)
1 (4.5)
CNS (+) (n=22) P 15–7 0.75
62 (23–76)
15 (68.2) 1
0.033 2 (9.1) 1
5 (2–11)
17 (77.3) 0.19
16 (72.7)
14 (63.6) 0.13 12 (54.5) 0.12
7 (31.8) 0.36 10 (45.5) 0.20 4 (18.2) 0.66 3.64 (0.12–12.6) 0.34
10 (45.5) 0.20
0.0042
0.015
Treatments, no. (%)
IFN a or PEG-IFN
Steroid
Radiation
Imatinib mesylate
Cyclophosphamide
Cladribine
Etoposide
Cyclosporine
Prostaglandin I2
CHOP
JLSG-02
Lung transplantation
0.014
17 (77.3)
1 (4.5) 0.34
3 (13.6) 1 1 (4.5) 0.61 1 (4.5) – 2 (9.1) – 1 (4.5) –
0 (0) – 1(4.5) – 1 (4.5) –
LCH: Langerhans cell histiocytosis; CNS: central nervous system; CRP: C-reactive protein; IFN-a: interferon a; PEG: pegylated; CHOP: cyclophosphamide, adriamycin, vincristine, and prednisolone. JLSG-02: a regimen protocol for LCH consisting of cytarabine, vincristine, and prednisolone
0 (0) –
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prognostic value of age and digestive involvement. The CRP level at onset also predicts the patients’ survival, per- haps reflecting the importance of the inflammatory status in the ECD condition. Additional large-scale studies are required in order to clarify the pathophysiology of ECD and improve the prognosis of the patients.
Acknowledgments
We would like to acknowledge K. Tanaka and Y. Nakada for their technical assistance.
Furthermore, we thank M. Fukuda (Asoka Hospital), H. Hiraga (Hokkaido Cancer Center), T. Yamauchi (Toki General Hospital), K. Takeuchi (Tochigi Cancer Center), Y. Shido (Hamamatsu University School of Medicine), S. Nogawa (Tokyo Dental College Ichikawa General Hospital), T. Hamada (Okayama University), N. Hayashi (Wakayama Rosai Hospital), S. Yokokura (Shin-Yamanote Hospital), T. Makiishi (Japanese Red Cross Otsu Hospital), T. Kitani (Ehime University), Y. Shibuya (Showa University Northern Yokohama Hospital), M. Yoshimitsu (Kagoshima University), J. Mitsushima (Matsue Seikyo General Hospital), S. Yano (Matsue Medical
Hospital), K. Tanaka (Okayama University), M. Yamamoto (Kochi University), K. Sato (Saitama Medical University), H. Sugano (Kochi Health Sciences Center), T. Kondo (Kyoto University), H. Takahama (National Cerebral and Cardiovascular Center), J. Nagano (Seirei Hamamatsu General Hospital), T. Baba (Kanagawa Cardiovascular and Respiratory Center), Y. Fukui (Juntendo University), K. Takenaka (Tsuchiura Kyodo General Hospital), K. Takada (Sapporo Medical University), S. Izumi (National Center for Global Health and Medicine), J. Kikuchi (Keio University), K. Takahashi (Kameda Medical Center), K. Shimizu (Higashihiroshima Medical Center), K. Takemura (Tokyo Teishin Hospital), and I. Choi (National Hospital Organization Kyushu Cancer Center) for pro- viding the clinical data and/or patient samples. We also thank H. Kawano (Teikyo University) and the members of the Japanese Musculoskeletal Oncology Group for cooperating in the collection of clinical data and/or patient samples.
Funding
This study is supported by Grants-in-Aid of the Ministry of Health, Labor and Welfare of Japan (H28-Nanchi-Ippan-002 to MS, TO, IK, and MK).
Center), M. Susa (Keio University), K. Ono
(Tosei General
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]]></page><page Index="85" isMAC="true"><![CDATA[Chronic Myeloid Leukemia
Reduced tyrosine kinase inhibitor dose is predicted to be as effective as standard dose in chronic myeloid leukemia: a simulation study based on phase III trial data
Artur C. Fassoni,1,2 Christoph Baldow,2 Ingo Roeder2,3* and Ingmar Glauche2*
*IR and IG contributed equally to this work.
ABSTRACT
Continuing tyrosine kinase inhibitor (TKI)-mediated targeting of the BCR-ABL1 oncoprotein is the standard therapy for chronic myeloid leukemia (CML) and allows for a sustained disease con- trol in the majority of patients. While therapy cessation for patients appeared as a safe option for about half of those patients with optimal response, no systematic assessment of long-term TKI dose de-escalation has been made. We use a mathematical model to analyze and consistent- ly describe biphasic treatment responses from TKI-treated patients from two independent clinical phase III trials. Scale estimates reveal that drug efficiency determines the initial response while the long-term behavior is limited by the rare activation of leukemic stem cells. We use this math- ematical framework to investigate the influence of different dosing regi- mens on the treatment outcome. We provide strong evidence to suggest that TKI dose de-escalation (at least 50%) does not lead to a reduction of long-term treatment efficiency for most patients, who have already achieved sustained remission, and maintains the secondary decline of BCR-ABL1 levels. We demonstrate that continuous BCR-ABL1 monitor- ing provides patient-specific predictions of an optimal reduced dose without decreasing the anti-leukemic effect on residual leukemic stem cells. Our results are consistent with the interim results of the DESTINY trial and provide clinically testable predictions. Our results suggest that dose-halving should be considered as a long-term treatment option for CML patients with good response under continuing maintenance thera- py with TKIs. We emphasize the clinical potential of this approach to reduce treatment-related side-effects and treatment costs.
Introduction
In tyrosine kinase inhibitors (TKI)-treated chronic myeloid leukemia (CML), the proportion of BCR-ABL1 mRNA is used to monitor the individual treatment response.1-3 Most patients show a typical bi-phasic response with a steep, initial decline (slope a), followed by a slower, secondary decline (slope β) of BCR-ABL1 levels.4-6 Whereas the initial decline is attributed to the eradication of proliferating leukemic cells (LC), the secondary decline has been suggested to result from a slower eradication of quiescent leukemic stem cells (LSCs).5-7 About two-thirds of the patients achieve major molecular remission (MMR), i.e. a reduction of three logs from the baseline (MR3), while one-third of these even achieve deep molecu- lar remission (DMR, i.e. MR4.5) within five years of treatment.3,6,8
Recently, TKI cessation and, thus, treatment-free remission has been established as an important therapeutic goal.9,10 However, about 50% of the patients with good response experience a molecular relapse after stopping TKI, pointing towards per- sisting residual LCs that cannot be controlled by patient-specific immunological mechanisms. As these mechanisms underlying the currently unpredictable individ- ual molecular relapse risk remain controversial, complementary approaches to
Ferrata Storti Foundation
1Instituto de Matemática e Computação, Universidade Federal de Itajubá, Brazil; 2Institute for Medical Informatics and Biometry, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Germany and 3National Center for Tumor Diseases (NCT), Partner Site Dresden, Germany
Haematologica 2018 Volume 103(11):1825-1834
Correspondence:
ingmar.glauche@tu-dresden.de
Received: March 29, 2018. Accepted: June 26, 2018. Pre-published: June 28, 2018.
doi:10.3324/haematol.2018.194522
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1825
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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minimize side-effects associated with continuous TKI therapy are required. While a number of studies evaluate TKI cessation, strategies to apply long-term dose reduc- tions are currently under-appreciated, although the poten- tial benefits of dose de-escalation are at hand: besides reducing treatment-related side-effects and increasing patients’ quality of life, it also reduces the treatment-relat- ed costs.11-14 The DESTINY trial (clinicaltrials.gov identifier: 01804985)15,16 is an ongoing study addressing TKI dose de- escalation. However, with its primary end point (molecu- lar relapse risk after TKI cessation preceded by a one year dose de-escalation) this trial focuses on stopping TKI, rather than on long-term outcomes under continuous but reduced TKI treatment.
Here, we describe a systematic, conceptual analysis of the impact of dose de-escalation on the long-term disease kinetics. Our simulation study relies on a mathematical description of TKI-treatment, which builds on a previous- ly published CML model.5,17 In contrast to the earlier approach, we use a simplified model which allows for a stringent analytical formulation of the disease dynamics without changing the overall qualitative system proper- ties. The model parameters are estimated from available, patient-specific BCR-ABL1 kinetics, determined within controlled clinical phase III trials [IRIS (clinicaltrials.gov iden- tifier: 0000634318), CML IV (clinicaltrials.gov identifier: 0005587419)].
Our results support the rationale for TKI dose de-escala- tion in patients who have already reached sustained remission. We provide strong evidence that the long-term depletion of residual LSCs in remission phase is not affect- ed by defined TKI-dose reduction. Furthermore, we pro- pose a strategy to determine patient-specific optimal TKI doses, and predict that dose-halving is a safe treatment option for the majority of patients in sustained molecular remission. The suggested dose optimization can con- tribute to the prevention of severe side-effects (e.g. cardio- vascular complications, pleural effusion) and to a reduc- tion of overall treatment costs.
Methods
Patient data and parametrization
The presented results are based on a secondary analysis of previously published data from the IRIS (clinicaltrials.gov identifier: 00006343)18 and CML IV (clinicaltrials.gov identifier: 00055874) tri- als.19 In particular, we used 69 patients from the German ima- tinib (400 mg) arm of the IRIS trial and 280 patients from the 400 mg imatinib monotherapy arm of the CML-IV study, for which IS corrected BCR-ABL1/ABL1 time courses were available at the time of our primary model analysis.5,17 As described in the orig- inal publications,20,21 both clinical trials were conducted in accor- dance with the Declaration of Helsinki and applicable regulatory requirements. The protocols were approved by the institutional review board or ethics committee of each participating center. All patients or guardians gave written informed consent before participation.
For each individual patient, the treatment response at time  (()), measured in the form 100% × BCR-ABL1/ABL1, is fur- ther described according to a biphasic characteristic, i.e.
For each patient, parameters A, B, a and β are determined using maximum likelihood estimation. For the model analysis, we selected patients with (i) sufficient time points for model fit- ting (>4) which (ii) do not show a long-term increase in BCR- ABL1/ABL1 ratio (β<0) but are characterized by (iii) a biphasic decline, (a<β<0). We also excluded 2 additional patients with measured BCR-ABL1 ratios of more than 500%, which indicates a pronounced non-linearity between BCR-ABL1 abundance and tumor load, resulting in n=55 (IRIS cohort) and n=134 (CML-IV cohort) (Online Supplementary Table S1). Median follow up of this patient cohort is 4.3 years [IQR (2.8,6.3)]; 98.4% of the patients achieved BCR-ABL1 ratio of less than 1%, while 91% achieved MR3 at least once. We also tested the robustness of our model results with respect to the reliability of high BCR-ABL1 values (Online Supplementary Table S2).
For comparisons with the DESTINY trial (clinicaltrials.gov iden- tifier: 01804985),15,16 only patients treated with TKI for at least three years and with BCR-ABL1 levels below MR3 for at least the last year of treatment were used. Therefore, we excluded from the study 53 patients treated for less than three years (excluding n=4 for IRIS; n=49 for CML-IV) and 14 patients with no MR3 in the entire last year of treatment (excluding n=4 for IRIS; n=10 for CML-IV). The time courses of the remaining 122 patients [(n=47 IRIS, median follow up 6.5 years [IQR(5.9;6.9)]; n=75 CML-IV, median follow up 4.6 years [IQR(3.9;6.1)] are available in Online Supplementary Figure S1. Following the DES- TINY trial, these patients were further split into an MR4 and an MR3 cohort, depending on whether their BCR-ABL1 levels in the last year were below MR4 or not. These selection and clas- sification procedures were based on the individual bi-exponen- tial fit () of each patient (also shown in Online Supplementary Figure S1).
Mathematical model
We apply a mechanistic model that describes TKI response as a dynamic process resulting from the interplay between tumor growth, activation/deactivation of LSCs, and cytotoxic TKI action on proliferating, but not on quiescent LSCs (Figure 1A). The model is a simplification of our previous computational CML model5,17 and formally related to a model proposed by Komarova and Wodarz.22 It considers three leukemic cell types: quiescent LSCs (), proliferating LSCs (), and fully differentiat- ed LCs (). Mathematically, the model is described by the fol- lowing set of differential equations:
The activation of dormant LSCs and deactivation of prolifer- ating LSCs are described by rate constants  and  respec- tively. LSCs proliferate with a rate constant  . During therapy, a cytotoxic TKI effect acts on proliferating LSCs, described by the rate >0. Differentiation of proliferating LSCs is quanti- fied by  and the limited life-time of differentiated LCs is mod- eled by a mortality rate . We define a net leukemia reduction =−Y with >0 for effective treatment. For illustrating simu- lations we used parameter values corresponding to the median values of the selected patients (Online Supplementary Text S1-S3).
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Reimplementation of the model in a stochastic version using a Gillespie algorithm ensured that there are no distinct differences resulting from small cell numbers (Online Supplementary Text S4).
In contrast to previous models,5,17 competition between nor- mal cells and LCs is described only implicitly, by assuming con- stant total cell numbers, , X , W in each cell compartment (Figure 1D, Online Supplementary Text S1 and Online Supplementary Figure S2 complementing Figure 1C on the level of absolute cell numbers). The actual tumor load, corresponding to BCR-ABL1 levels, is modeled as the percentage of LCs with respect to the total cell number. Figure 1C demonstrates that the
AB
modeled BCR-ABL1 levels of proliferating LSCs behave exactly like the BCR-ABL1 levels in the peripheral blood (PB). Therefore, only the dynamics of proliferating LSCs will be considered.
Results
The long-term effect of TKI is limited by the rare activation of quiescent LSCs
We apply a simple mathematical model that describes the time course of TKI response in CML as a dynamic
C

D
slopes in the bi-exponential decline
Figure 1. Mathematical model for
chronic myeloid leukemia (CML)
treatment and mechanistic interpre-
tation of the bi-phasic decline. (A)
Schematic model representation with
three cell types: quiescent (, blue)
and proliferating (, red, turnover with
rate  ) leukemic stem cells (LSCs), 
and differentiated leukemic cells
(LCs), denoted by  (green, generat-
ed with rate  , decaying with rate 
r ). The model assumes (i) mecha- 
nisms of activation/deactivation of
quiescent/proliferating LSCs with
rates  and  and (ii) a cytotoxic  
effect of TKI on proliferating LSCs with intensity  . (B) The mecha-
nistic model parameters [(TKI net effect (= − ), activation rate of
quiescent LSCs (  ), deactivation 
equation (SE1)
in Online
 Y
rate of proliferating LSCs ( )] were 
fitted to individual patient data from the IRIS and CML-IV trials.18,19 The resulting distributions reveal an intrinsic scaling between them, which are dispersed over different orders of magnitude. (C) Model simulation with median parameter values obtained from IRIS and CML-IV data illustrating the equivalence between tumor load (in terms of BCR-ABL1 levels) in the peripheral blood (green) and within the proliferating LSCs (red). Values on the y-axis indicate the relative abun- dance of BCR-ABL1 positive cells in each specific cell compartment [see
Supplementary Text S1], which corre-
sponds to the tumor load in terms of
PCR-based measurements of the
BCR-ABL1/ABL1 ratio. We adopted
this scheme for all corresponding fig-
ures throughout the manuscript.
Using the intrinsic scaling (B), the
of the BCR-ABL1 levels simplify to
≈− and ≈− . The abundance of
quiescent LSCs follows a monophasic decline approximated by ≈− .

See Online Supplementary Text S3
for parameter values used in all
model simulations. (D) During the ini-
tial phase (upper panel, “1st slope”),
eradication of the proliferating LSCs
(red) with effective rate q is the dom-
inating process (large black arrow).
After the strong initial reduction, few
proliferating cells remain (lower
panel, “2nd slope”) and eradication is
now limited by the activation rate  
(small black arrow) of quiescent LSCs (blue). Normal cells are shown in gray. See also Online Supplementary Figure S2.

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process resulting from the interplay between tumor growth, activation/deactivation of LSCs, and cytotoxic TKI action (Figure 1A, and see Methods). In brief, the model describes three LC types: quiescent LSC (X), prolif- erating LSC (Y) and fully differentiated LCs (W). The acti- vation of dormant LSCs and deactivation of proliferating LSCs are described by rate constants  and X while LSCs proliferate with a rate constant . During therapy, we assume a cytotoxic TKI effect on proliferating LSCs,
described by the rate constant >0.
We obtain an exact solution for the model, in which the
patient-specific response can be expressed in terms of the mechanistic model parameters [equation (SE5) in Online Supplementary Text S2]. In other words, a patient’s bi-pha- sic BCR-ABL1 decline characterized by the slopes a, β is expressed in terms of the resulting net cytotoxic effect =− (difference between TKI toxicity and LSC prolif- eration) and the effects of LSC activation/deactivation 
A
B
CD
EF
Figure 2. Model predictions on dose de-escalation and dose escalation. (A) The long-term treatment efficiency, defined as the magnitude of the second slope , is
shown as a function of the dose reduction. The threshold for optimal favorable reduction, 
1C) indicates how much the standard dose can be reduced without losing treatment efficiency. 
can be calculated for each patient (see main text). Any other
favorable dose reductions (dose fraction >
, green region) also retain the long-term treatment efficiency, while unfavorable dose reductions (dose fraction
<
, red region) are predicted to lead to a severe decrease in the long-term treatment efficiency. (B-E) Simulations of favorable (B), optimal favorable (C) and


unfavorable (D and E) dose reductions after 36 months under standard dose. After favorable dose reductions, a transient increase in proliferating leukemic stem
cells (LSCs) (red) is followed by a return to the original decrease rate ≈− , while the dynamics of quiescent LSCs remains unchanged (blue lines). In the case of

unfavorable reduction, an impaired scenario is observed. See also Online Supplementary Figures S3-S6. (F) dose escalation to =200% after three years of treat-
ment; although a deeper level is reached in the BCR-ABL1 levels of proliferating LSCs, the dynamics of quiescent LSCs remains unchanged.

(≈25% in this example, i.e. using median parameters as in Figure

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and . Taking into account the intrinsic scaling between the mechanistic parameters (Figure 1B), which indicates that LSC deactivation, activation, and depletion by TKI occur at different time scales, those expressions for  and  can be further simplified, allowing us to dissect the prominent processes governing each treatment phase (Figure 1C and D, Online Supplementary Texts S5-S7 and Online Supplementary Figure S2).
We found that slope  can be expressed as ≈−=−, thereby confirming that the initial treat- ment phase is dominated by the cytotoxic TKI effect on proliferating LSCs, which leads to a rapid reduction in BCR-ABL1 levels. Dose-escalation studies for imatinib substantiate this result by indicating that a higher TKI dose leads to a more rapid response.23,24 Similarly, slope  can be approximated as ≈−, implying that after deple- tion of initially abundant proliferating LSCs, the treatment response is bounded by the rare activation of quiescent LSCs. This provides a consistent explanation for the slow- er long-term decrease in proliferating and quiescent LSCs. These analytical conclusions confirm previous findings,5-7 but also allow further predictions on the effect of dose de- escalation to be made.
A wide range of reduced TKI doses is predicted to induce the same long-term response as standard dose
Due to the bounded activation of quiescent LSCs after the initial therapy response, there is a range of favorable reduced TKI doses where the long-term efficiency (defined by the magnitude of slope ) remains almost constant with the same overall efficiency as that achieved when applying the standard dose (green region in Figure 2A, and Online Supplementary Figure S3). In this case, the resulting, although reduced, cytotoxic TKI effect is still sufficient to target the abundant proliferat- ing LSCs once a patient has reached sustained remission. This range of ‘favorable’ reduced doses spans from the standard full-dose to a certain threshold, i.e. an ‘optimal favorable’ dose (green dashed line in Figure 2A), below which an accelerated decrease in long-term treatment efficiency is observed. Therefore, dose reductions below this optimal dose are considered as ‘unfavorable’ (red region in Figure 2A).
We look for a mathematical expression, which allows us to estimate this optimal dose reduction for each patient in terms of the model parameters. Although there is a mini- mal required plasma concentration for TKI cytotoxicity,
AB
CD
Figure 3. Step-wise treatment optimization. (A) Step 1: initial treatment with standard dose until the patient shows a clearly identifiable second slope (approx. 18 months) and determination of the bi-exponential parameters (A, B, a, β). (B) Step 2: reduction of tyrosine kinase inhibitor (TKI) dose by half and continuous moni- toring of the treatment response until the new intercept B′ can be inferred (approx. 18 months). (C) Step 3: reduction to the optimal dose calculated from values of the identified parameters (A, B, B’, a, β; see main text). (D) The long-term follow up using optimal dose shows that the response to this adaptive treatment adheres to the original slope β for the eradication of residual leukemic stem cells (LSCs) as standard dose treatment. Although the adapted treatment leads to a delay in the reduction of BCR-ABL1 levels in proliferating LSCs and, therefore also in the peripheral blood, the treatment dynamics in the residual quiescent LSCs are unaltered while drug intake is drastically reduced.
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which sets a lower limit to the dose de-escalation, a linear dose-response relationship is generally accepted over a wide range of treatment-relevant doses above this thresh- old.25,26 Thus, we deduced an explicit expression for the patient-specific optimal favorable dose reduction fraction  (Online Supplementary Text S8), given by
 =0.247, and corresponds to a long-term treatment effi- ciency of 98.4% compared to the standard dose. Therefore, for the ‘median patient’ in our analysis, a reduction to 24.7% of the original dose would lead to a marginal decrease of only 1.6% in the long-term treatment efficien- cy, given that a minimal required plasma concentration for TKI cytotoxicity is maintained.
Our model predicts transient increases in BCR-ABL1 lev- els of proliferating LSCs when applying different dose reductions after the first decline, i.e. once a substantial reduction in BCR-ABL1 levels had been achieved (Figure 2). However, for favorable reductions, BCR-ABL1 levels decrease again with the original long-term treatment effi- ciency (slope ) after a few months (Figure 2B and C). For the example of a ‘median patient’, dose reductions at month 36 of treatment will maintain MR3, while BCR-ABL1 levels are predicted to return to their original val- ues at de-escalation after about 20 months (in case of favor- able reduction with =0.5) or 58 months (for the optimal favorable reduction with =0.25). Importantly, the transient increase of proliferating LSCs and, therefore, of BCR-ABL1 levels in the PB, does not lead to either relevant differences in the overall response of quiescent LSCs or in the total
This optimal fraction 
minimal favorable dose which still maintains the original long-term reduction rate of both proliferating and quies- cent LSCs. Therefore, as long as the TKI dose is not reduced below this threshold, our model predicts no impaired long-term efficiency, while an over-reduction compromises the overall treatment success.
We conclude from equation (E5) that  is a patient- specific, fixed quantity determined by the proliferation rate of LSCs, , their activation rate , as well as the toxicity of the TKI, =−. For the median parameters of the available dataset, the optimal favorable reduction fraction is
corresponds to the
AB
CD
Figure 4. Model predictions on dose de-escalation and comparison with clinical data. (A) Comparison of DESTINY interim results with model simulations of 50% dose de-escalation applied to IRIS and CML-IV patient data (assuming the same protocol and patient selection criteria of DESTINY). We simulated dose de-escalation starting from the individually predicted remission level at the time of the last BCR-ABL1 measurement of each patient, and evaluated the fraction of patients above MR3 one year after de-escalation. Error bars indicate 90% confidence intervals. (B) Model estimates of the risk of losing MR3 within one year after de-escalation, depending on the patient’s individual predicted remission level just before de-escalation. Patients with remission level above MR3.5 are very likely to lose MR3 at least transiently. (C) Model simulation illustrating the transient relapse above MR3 three months after de-escalation (highlighted time interval). De-escalation of 50% was implemented for a hypothetical patient of the DESTINY trial one year after reaching MR3. The simulation of a continuing half-dose regimen predicts that after about nine months the BCR-ABL1 levels fall below MR3 and the response regains the original slope . (D) Simulation results showing the predicted relative increase/decrease in the number of patients without molecular relapse two years after cessation. We use the standard treatment scenario (full-dose for one year) as the reference (corresponding to the dashed line at 0%) to compare it with: i) half-dose for one year (the DESTINY protocol; red), and ii) half-dose for two years (blue). Relapse is defined as loss of MR3.
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LSCs population when compared to standard dose (Online Supplementary Figure S4). Our model also predicts that returning to the full dose regimen at a later point completely restores the original response levels of proliferating LSCs within a few months (Online Supplementary Figure S5).
Patient-specific optimal dose can be estimated after an initial dose reduction
The calculation of patient-specific optimal TKI doses requires the knowledge of model parameters , , , and . Whereas , , and =− can be estimated from time course data, the LSC proliferation rate  is con- founded with the individual TKI-effect  and cannot be deduced directly. Therefore, we propose to estimate  by observing the transient increase in proliferating LSCs occurring after a first favorable dose reduction. Technically, we suggest a moderate initial reduction to fraction  of the standard dose, after the patient’s response under standard dose has been sufficiently quantified in terms of the kinetic parameters (,,,) (Figure 3A). Although dose-halving (i.e. =0.5) seems to be safe for this first de-escalation (see below), the proposed approach is valid for any reasonable reduction. After a transient increase in the BCR-ABL1 levels, a new intercept ′ can be observed approximately 18 months after the dose reduc- tion (Figure 3B). Based on the difference of intercepts  and ′, and the reduction fraction , the proliferation rate  can be estimated (Online Supplementary Text S9) by
and the individual optimal dose reduction fraction  can be calculated using equation (E5). This dose is predict- ed to retain the original long-term treatment efficiency (Figure 3C and D).
A population-based estimate predicts that the majority of patients in sustained remission retain the long-term treatment efficiency after dose-halving
As pointed out above, the LSC proliferation rate , as an indicator of the ‘aggressiveness’ of the untreated dis- ease, is intrinsically unknown. In order to circumvent this limitation, we also used a population-based estimate derived from CML latency times, i.e. the time between the first leukemic transformation and diagnosis, given that no secondary events change the kinetics of disease emer- gence (Online Supplementary Figure S6A). Sampling from a distribution of CML latency times as reported by Radivoyevitch et al.27 [median latency time = 6.9 years, IQR (5.0,10.1)] (Online Supplementary Figure S6B) and tak- ing into account the observed TKI response, we obtained an individual distribution of possible proliferation rates  for each patient (Online Supplementary Figure S6C). In other words, we fit our mathematical model several times under different, plausible assumptions about the aggressiveness of the underlying leukemia. For each of those hypothetical but realistic scenarios we calculate the reduction level  (Online Supplementary Figure S6D).
Based on these different possible scenarios (i.e. different leukemia growth parameters), we calculated for each patient the fraction of its individual values of  which are below 0.5 (Online Supplementary Figure S6F). This frac- tion indicates whether dose-halving appears as a suitable treatment option or not. With these estimates, our model
predicts that 90% of the patients in the German IRIS cohort and 81% of the patients in the CML-IV trial who once achieved MR3, could have safely decreased their TKI dose by at least 50%, while maintaining the overall thera- py effect on quiescent LSCs (Online Supplementary Figure S7A). Therefore, dose-halving is expected to be safe for the majority of patients in sustained remission and might serve as the initial step to estimate the optimal individual dose.
Our results also suggest that the ratio / can be used to identify patients who are likely to benefit from dose reduction. We predict that patients with />15 are very likely to retain the original long-term treatment efficiency after a 50% dose reduction (Online Supplementary Figure S7B and C). Furthermore, we derived a condition to iden- tify patients who do not obtain sufficient TKI dose initial- ly. Specifically, we found that patients with slopes /<2 would benefit from dose escalation, while only patients with /≫2 benefit from dose de-escalation (Online Supplementary Figure S8).
The model predictions are similar to results from the DESTINY trial and support the design of new, informative trials
We compared our model results with findings from the DESTINY trial, which studies dose-halving in 174 TKI- treated patients with CML (being either in MR4 or MR3 for at least 12 months) before TKI cessation. The pub- lished DESTINY interim-analysis indicates that 93% of the patients showed no loss of MR3 within 12 months post dose reduction.15 We simulated this scenario by pre- dicting virtual treatment responses from BCR-ABL1 meas- urements in the IRIS/CML-IV trials. In particular, we identified 122 patient time courses fulfilling the inclusion criteria of the DESTINY protocol (> 3 years under TKI, > 1 year in MR3) and simulated a virtual TKI dose reduction according to the DESTINY protocol at the end of the available follow up for each of those patients. Using the same distribution of latency times as above, we calculat- ed for each patient the fraction of values of , which lead to loss of MR3 within one year after de-escalation (Online Supplementary Figure S6E). This fraction can be interpreted as an estimate for the patient-specific risk of a molecular relapse. We also calculated the expected proportion of relapsed patients within the overall population, as well as in the corresponding subcohorts of patients being in either MR3 or MR4 within the last year before dose reduction (Figure 4A). Although a quantitative compari- son should be considered with caution due to potential differences in the study populations and patient compli- ance, the results predicted for the IRIS/CML-IV patients show qualitatively similar relapse rates as observed in the DESTINY trial. Our findings also suggest that the individ- ual relapse probability is related to the remission level before de-escalation, with patients below MR3.5 having a very low probability of relapse (Figure 4B). Furthermore, we predict that most of the observed relapses are tran- sient, i.e. MR3 regain is expected when continuing the half-dose regimen (Figure 4C). Therefore, we argue that the current focus on exceeding MR3 as an indicator for a potential relapse might be reconsidered in the context of dose de-escalation strategies, while closer monitoring of the disease dynamics following dose reductions should be applied to distinguish transient from permanent BCR- ABL1 regrowth dynamics.
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Although our model does not yet reflect immunological effects, which are proposed to be important determinants of disease dynamics post TKI-cessation, we speculated about the relative impact of dose reductions with respect to treatment stop. Specifically, we simulated the DES- TINY cessation protocol for the IRIS and CML-IV patients in our data-set and evaluated the primary DESTINY end point, i.e. the proportion of patients who can de-escalate TKI dose by 50% for one year and then stop treatment completely for two years without losing MR3. Our simu- lations indicate higher rates of molecular relapse in com- parison to a structurally identical control group receiving full-dose before TKI stop (Figure 4D) if no additional immunological control mechanisms are considered. However, comparing dose reductions of different dura- tion, we predict a beneficial effect if patients remain at half-dose for longer before stopping TKI. We conclude that the same cumulative dose is more efficient if applied over a longer time period, thereby emphasizing that the full benefit of TKI dose de-escalation appears in the long term.
Discussion
Our study supports the concept that TKI dose reduction in maintenance therapy can be a safe option for many CML patients who have already achieved a sustained remission. In particular, we dissect the typical biphasic response pattern under continuing TKI treatment and con- clude that the TKI effect during the secondary treatment phase is limited by the rare activation of quiescent LSCs. Our simulations predict that the overall treatment effect is maintained for most patients, even if the TKI dose is reduced. Based on their initial treatment response under full dose, we identify patients who most likely benefit from a reduction scheme and present a strategy to esti- mate a patient-specific, optimal dose. Our results suggest a treatment strategy that could considerably reduce cumu- lative drug intake and, therefore, decrease drug-mediated side-effects. It might also increase compliance of patients to adhere to the prescribed treatment schedule. On the population level, the long overall survival times of continuously treated CML-patients add a distinct eco- nomical aspect to the outlined strategy, as the high treat- ment costs could be substantially reduced.
The proposed strategy is not restricted to a particular TKI. Although our model encompasses all TKI pharmaco- kinetic parameters and doses within a single parameter , we have found that this simple model, using a rela- tive reduction compared to a standard dose of the respec- tive TKI, is equivalent to a more elaborate formulation explicitly considering the daily TKI intake (Online Supplementary Text S10 and Online Supplementary Figure S9). Although a linear dose-response relationship appears to be an appropriate model assumption,25,26 we emphasize that the potential for dose reductions might be limited by a necessary TKI plasma concentration to ensure drug activity. Based on in vitro data for imatinib,28 we estimate this limit to be in the order of 25% of the original dose (Online Supplementary Text S11). Furthermore, recent results from clinical trials15,29 indicate that a 50% dose reduction is therapeutically active.
Several clinical studies have addressed the potential of dose reductions in various settings. While Naqvi et al.
report good results from a cohort of newly diagnosed CP- CML patients treated with low-dose dasatinib (50 mg daily) first line,29 Russo et al. study the effect of a one- month-on/on-month-off imatinib regimen in elderly patients after at least two years of initial full-dose therapy.30 In the later study, one-third of the patients lost their previous remission levels. Based on our model, we speculate whether the extended treatment interruptions might have added to this outcome as no therapeutically active TKI concentrations were achieved during this time. Furthermore, we have seen that several clinical studies reported a clear advantage of more potent TKI to achieve molecular response earlier as compared to standard-dose imatinib.8,31,32 However, the corresponding advantage in long-term survival is less pronounced, and we suggest that it is not the drug potency but the rare activation of LSCs that marginalizes the survival benefit.
In order to test our predictions in a controlled clinical setting, we suggest an approach in which the dynamics of initial treatment response to standard therapy are suffi- ciently monitored to obtain reliable estimates of the rele- vant slopes for an informed treatment adaptation (mea- surements every 3-4 months within the first year and at least every six months thereafter). Only after a clinically relevant remission level (at least MR3) is reached can dose reductions (e.g. < 50% of the initial dose) be considered and these should be accompanied by a detailed follow-up monitoring of BCR-ABL1 levels to guarantee patient safety and also inform on the validity of our model approach. Further dose reductions might be considered as a second step towards approaching an optimally reduced dose that retains the therapeutic threshold.
Our modeling results predict a transient increase of the number of proliferating LCs after dose reduction. However, because this is only a transient and expected effect, we suggest that the clinical criteria for molecular relapse after dose de-escalation would benefit from con- sidering a follow-up period rather than focusing on fixed thresholds. Although the transient increase in proliferating LCs might increase the chance of acquiring secondary mutations, we reason that this is a marginal effect which needs to be compared with the benefits of reducing treat- ment-related side-effects. Indeed, assuming that the risk of acquiring a secondary mutation is proportional to the number of proliferating LSCs divisions, this risk increases by only 1.5% when half-dose is applied for three years (after an initial period of three years under standard dose) in comparison with the full-dose scenario (Online Supplementary Text S12 and Online Supplementary Figure S10). We acknowledge that our estimates are based on the assumptions that there are no direct dose-dependent resistance mechanisms. This is supported by the observa- tion that re-starting TKI treatment after relapse in cessa- tion studies proved overall successful and did not suggest a higher tendency for TKI resistances.33,34
Our current model does not consider any immunologi- cal effects or other more detailed competition mechanism between LCs and their environment. Therefore, our pre- dictions on the risk of molecular relapse after TKI cessa- tion are solely based on the fraction of LCs at the time of TKI stop and the proliferation rate estimated from CML latency times. This implies that a lower residual LSC num- ber ultimately results in a lower relapse risk. Because of this limitation, our model does not reflect potentially ben- eficial effects resulting from mildly increased abundance
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of proliferating LCs which potentially stimulate a patient’s immune response.
Although TKI treatment response is still substantially heterogeneous with respect to many clinical parameters, the well-defined CML phenotype and the accessibility of kinetic data on treatment response has made CML a pri- mary target for mathematical model approaches in oncol- ogy.4-6,22 It has also been recognized that the regulation of stem cell quiescence under continuing TKI therapy affects the kinetics of disease eradication.5,22 Here, we consider a conservative scenario, which only assumes a direct cyto- toxic TKI effect on proliferating LCs, but does not alter LSCs quiescence. If assuming an additional TKI-depen- dent reduction of the activation rate , as previously dis- cussed,5,17,35-37 any favorable dose de-escalation would lead to an even better long-term response (Online Supplementary Figure S3). Recently, using an analytical approach very similar to our formulation, Werner et al. developed a mathematical model that allows an estima- tion of LSC fractions to be made from longitudinal measurements of tumor load.38 However, this model assumed no direct therapeutic effect on LSCs, which are, therefore, increasing even during treatment.
In summary, we show that the systematic assessment of available clinical data by means of mathematical models has direct clinical implications, but also reveals underlying disease and treatment mechanisms. Our results are sub- stantiated by and support the interim findings of the ongo-
ing DESTINY trial, thereby suggesting a change in current clinical practice and the consideration of TKI dose de-esca- lation strategies in maintenance therapy. As with any the- oretical prediction, our results represent hypotheses that need to be validated in clinical trials. However, modeling approaches can substantially support the design of inform- ative trials. We consider this simulation study as a proof- of-concept for the use of systems medicine to optimize treatment efficacy and to minimize health care costs.
Acknowledgments
Our analysis is based on previously published data from the German cohort of the IRIS trial and the CML IV study. We would like to acknowledge the PIs, study groups and reference labs involved in these studies for generating and providing the data. In particular, we thank Andreas Hochhaus, Rüdiger Hehlman and Martin Mueller.
Funding
The research of ACF was supported by the Excellence Initiative of the German Federal and State Governments (Dresden Junior Fellowship) and by CAPES/Pós-Doutorado no Exterior Grant number 88881.119037/2016-01. This work was further sup- ported by the German Federal Ministry of Education and Research (www.bmbf.de/en/), Grant number 031A424 “HaematoOpt” to IR and Grant number 031A315 “MessAge” to IG. We acknowledge support from the Open Access Publication Funds of the SLUB/TU Dresden.
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Treatment-free remission after two-year consolidation therapy with nilotinib
in patients with chronic myeloid leukemia: STAT2 trial in Japan
Naoto Takahashi,1 Kaichi Nishiwaki,2 Chiaki Nakaseko,3,4 Nobuyuki Aotsuka,5 Koji Sano,2 Chikako Ohwada,4 Jun Kuroki,6 Hideo Kimura,7
Michihide Tokuhira,8 Kinuko Mitani,9 Kazuhisa Fujikawa,10 Osamu Iwase,11 Kohshi Ohishi,12 Fumihiko Kimura,13 Tetsuya Fukuda,14,15 Sakae Tanosaki,16 Saori Takahashi,17 Yoshihiro Kameoka,17 Hiroyoshi Nishikawa,18
Ferrata Storti Foundation
Hisashi Wakita5,19 and the STAT study group
Haematologica 2018 Volume 103(11):1835-1842
1Department of Hematology, Nephrology and Rheumatology, Akita University Graduate School of Medicine; 2Department of Oncology and Hematology, Jikei University Kashiwa Hospital; 3 Department of Hematology, International University of Health and Welfare School of Medicine, Narita; 4Department of Hematology, Chiba University Hospital; 5Department of Hematology and Oncology, Japanese Red Cross Narita Hospital; 6Department of Internal Medicine, Yuri General Hospital, Yurihonjo; 7Department of Hematology, Northern Fukushima Medical Center, Date; 8Department of Hematology, Saitama Medical Center, Saitama Medical University, Kawagoe; 9Department of Hematology and Oncology, Dokkyo Medical University, Tochigi; 10Department of Hematology, Chibaken Saiseikai Narashino Hospital; 11Department of Hematology, Tokyo Medical University Hachioji Medical Center; 12Transfusion Medicine and Cell Therapy, Mie University Hospital, Tsu; 13Division of Hematology, National Defense Medical College, Tokorozawa; 14Department of Hematology, Tokyo Medical and Dental University Hospital; 15Department of Hematology, Tottori University Hospital, Yonago; 16Department of Hematology, The Fraternity Memorial Hospital, Tokyo; 17Clinical Research Promotion and Support Center, Akita University Hospital; 18Division of Cancer Immunology, Research Institute / Exploratory Oncology Research & Clinical Trial Center, National Cancer Center, Tokyo/Kashiwa and 19Japanese Red Cross Chiba Blood Center, Funabashi, Japan
ABSTRACT
The purpose of this trial was to evaluate the efficacy of 2-year consolidation therapy with nilotinib, at a dose of 300 mg twice daily, for achieving treatment-free remission in chronic myeloid leukemia patients with a deep molecular response (BCR-ABL1IS ≤0.0032%). Successful treatment-free remission was defined as no con- firmed loss of deep molecular response. We recruited 96 Japanese patients, of whom 78 sustained a deep molecular response during the consolidation phase and were therefore eligible to discontinue nilotinib in the treatment-free remission phase; of these, 53 patients (67.9%; 95% confidence interval: 56.4–78.1%) remained free from molecular recurrence in the first 12 months. The estimated 3-year treatment-free survival was 62.8%. Nilotinib was readministered to all patients (n=29) who experienced a molecular recurrence during the treatment-free remission phase. After restarting treatment, rapid deep molecular response returned in 25 patients (86.2%), with 50% of patients achiev- ing a deep molecular response within 3.5 months. Tyrosine kinase inhibitor withdrawal syndrome was reported in 11/78 patients during the early treatment-free remission phase. The treatment-free survival curve was significantly better in patients with undetectable molecular residual disease than in patients without (3-year treatment-free sur- vival, 75.6 versus 48.6%, respectively; P=0.0126 by the log-rank test). There were no significant differences in treatment-free survival between subgroups based on tyrosine kinase inhibitor treatment before the nilotinib consolidation phase, tyrosine kinase inhibitor- withdrawal syndrome, or absolute number of natural killer cells. The
Correspondence:
naotot@doc.med.akita-u.ac.jp
Received: April 4, 2018. Accepted: June 28, 2018. Pre-published: July 5, 2018.
doi:10.3324/haematol.2018.194894
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1835
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
haematologica | 2018; 103(11)
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ARTICLE
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results of this study indicate that it is safe and feasible to stop tyrosine kinase inhibitor therapy in patients with chronic myeloid leukemia who have achieved a sustained deep molecular response with 2 years of treatment with nilotinib. This study was registered with UMIN-CTR (UMIN000005904).
Introduction
Nilotinib is a second-generation tyrosine kinase inhibitor (TKI) that has been shown to be highly efficacious as a first- or second-line treatment for patients with Philadelphia chromosome-positive chronic myeloid leukemia (CML) in chronic phase. In patients newly diag- nosed with CML in chronic phase superior rates of deep molecular response (DMR) were achieved with nilotinib in comparison with imatinib, which is a first-generation TKI currently used as the standard treatment for this disease.1-3 In addition, switching to nilotinib after a minimum of 2 years on imatinib led to increased DMR rates compared to remaining on imatinib.4
Recently, treatment-free remission (TFR) has been pro- posed as a goal for CML treatment.5-7 Indeed, prospective trials have indicated that imatinib therapy can be success- fully discontinued in CML patients who have maintained a DMR for at least 2 years.8-10 In these prospective trials, the TFR rate was 43% [95% confidence interval (CI): 33–52%] at 6 months9 and 41% (95% CI: 29–52%) at 12 months in the STIM1 trial,8 while the TWISTER study revealed a TFR rate of 47.1% (95% CI: 31.5–62.7%) at 24 months.10 Moreover, the first TFR study of second-generation TKI, the DADI trial reported by Imagawa et al., showed that second-generation TKI therapy can be successfully discon- tinued.11 In this trial, all patients received dasatinib consol- idation therapy for at least 1 year. The estimated TFR rate was 49% (95% CI: 36–61%) at 6 months.11 On the other hand, the ENESTfreedom study, which is a TFR study fol- lowing frontline nilotinib treatment, required that all patients sustained DMR during the consolidation phase with nilotinib for 1 year. The TFR rate at 48 weeks was 51.6% (95% CI: 44.2–58.9%).12 Although the DMR in the consolidation phase with a second-generation TKI was sustained in both the DADI trial and the ENESTfreedom study, the TFR rate was not superior to those in the previ- ously reported imatinib TFR studies.8-10 Most relapses occurred within 6 months of discontinuing second-genera- tion TKI or imatinib therapy, and there was no disease pro- gression in patients with molecular relapse after discontin- uation.8-12 All patients who relapsed remained sensitive to TKI re-treatment in these TFR studies.8-12
Compared to imatinib, nilotinib may enable a greater proportion of patients with CML in chronic phase to achieve successful TFR if they receive nilotinib consolida- tion therapy for 2 years to sustain DMR; this is the same length of time required to achieve TFR in imatinib stud- ies.8,9 The aim of this STAT2 trial (Stop Tasigna® Trial) was to evaluate the efficacy of 2-year consolidation treatment with nilotinib for achieving successful TFR in patients with chronic phase CML.
Methods
Patients and study design
The eligibility criteria for this multicenter, phase II, single-treat- ment arm, open-label clinical trial included: patients with CML in
chronic phase, age ≥16 years, an Eastern Cooperative Oncology Group performance status of 0–2, and no severe primary organ dysfunction. Patients who had accelerated phase or blast crisis CML, a T315I mutation, or who had received allogeneic hematopoietic stem-cell transplantation were excluded from this study. Patients with a DMR (BCR-ABL1IS ≤0.0032% or a molecu- lar response, MR4.5, defined as a 4.5-log reduction in BCR-ABL1 transcripts according to the international scale], assessed by real- time quantitative polymerase chain reaction (RQ-PCR), under treatment with imatinib or a second-generation TKI following imatinib were eligible for the STAT2 trial. Nilotinib (300 mg) was administered twice daily (600 mg/day) for 2 years in the consoli- dation phase. Patients who maintained a MR4.5 during the 2-year consolidation phase were eligible to enter the TFR phase and cease nilotinib treatment. Molecular recurrence was defined as the loss of a major molecular response (MMR: BCR-ABL1IS ≤0.1%) or confirmed loss of MR4.5 (at two consecutive assessments within 4 weeks) after discontinuing nilotinib, based on criteria used both in the STIM1 trial8 and the TWISTER study.9 Patients with molec- ular recurrence during the TFR phase restarted nilotinib 300 mg twice daily, thus entering the re-treatment phase.
Endpoints and assessments
The primary endpoint of the STAT2 trial was the 12-month TFR rate after discontinuing nilotinib treatment; secondary end- points were the 24-month TFR rate after discontinuing nilotinib treatment, the 3-year treatment-free survival, and the MR4.5 rate and time to MR4.5 achieved by nilotinib in the re-treatment phase. Safety profiles, especially vascular adverse events in the consoli- dation phase or symptoms related to TKI withdrawal syndrome in the TFR phase, were evaluated. Adverse events were assessed according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.03.
MR was evaluated by BCR-ABL1IS RQ-PCR analysis upon study entry and every 3 months thereafter in the consolidation phase. After discontinuing nilotinib in the TFR phase, molecular recur- rence was monitored by monthly BCR-ABL1IS RQ-PCR testing in the first year, bi-monthly testing in the second year, then every 3 months thereafter. In the re-treatment phase, BCR-ABL1IS was monitored by monthly RQ-PCR testing. The study protocol was terminated when MR4.5 was re-achieved, or when BCR-ABL1IS increased twice consecutively in the re-treatment phase.
BCR-ABL1IS RQ-PCR was performed using a Molecular MD One-Step qRT-PCR BCR-ABL kit (BML Inc., Kawagoe, Japan). To validate BCR-ABL1 amplification, ABL1 was used as an internal control. A MMR was defined as a 3-log reduction in the BCR- ABL1 transcript according to the international scale (BCR-ABL1IS ≤0.1%), MR4.5 was defined as a 4.5-log reduction in the BCR-ABL1 transcript (BCR-ABL1IS ≤0.0032%), and MR5 was defined as a 5- log reduction in the BCR-ABL1 transcript (BCR-ABL1IS ≤0.001%), as described above. Undetectable molecular residual disease was defined as undetectable BCR-ABL1 transcript with MR5 (UMRD with MR5). At least 100,000 control genes (ABL1) were required for a sample to be considered as adequate.
Ethics
Forty-six institutions participated in this study. The study was conducted in accordance with the principles of the Declaration of Helsinki. Written informed consent was obtained from each par-
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ticipant before enrollment. The study was approved by the Ethics Committee of Akita University (N. 786) and by all institutional ethic committees that participated in this study. The study was registered with UMIN-CTR (UMIN000005904).
Results
Patients and treatment
Between July 2011 and December 2012, 96 patients who achieved MR4.5 were enrolled in the STAT2 trial. These patients started treatment in the consolidation phase and were defined as the safety analysis set. Seventy-eight patients entered the TFR phase and were analyzed as the full analysis set for TFR. The baseline demographics of the safety and full analysis sets are shown in Table 1.
The median age in the safety analysis set was 55.5 years (range, 20–83). Thirty-six (37.5%) patients were female and 16 (16.7%) patients had been administered interferon- a before TKI treatment. Based on TKI therapy prior to entry into the current study, patients were classified into three groups: 50 patients (52.1%) who had received only imatinib (‘imatinib only’), 40 patients (41.7%) who had received nilotinib following imatinib (‘nilotinib following imatinib’, including patients from the STAT1 study), and six patients (6.3%) who had received other therapy
Table 1. Baseline demographics of all patients included in the study.
(‘other’). The STAT1 study (Switch to Tasigna® Trial) is a clinical trial to evaluate the efficacy of 2-year consolidation treatment with nilotinib for achieving DMR in chronic phase CML patients with MMR, recently reported by our study group.13 Among 40 patients in STAT2 treated by nilo- tinib following imatinib, 21 patients joined this study from STAT1 since they achieved MR4.5 in the STAT1 study. The reasons for switching from imatinib to nilotinib in the 40 patients included imatinib resistance in 7.5%, imatinib intolerance in 20.0%, and upon patients’ request in 72.5% (Online Supplementary Table S1). The median duration of imatinib or nilotinib treatment was 73.6 months (range, 11–126) or 7.7 months (range, 0–35), respectively. All patients showed MR4.5 at the time of entry into the study, and the median time to MR4.5 on TKI therapy was 48.1 months (range, 6–128). Among 96 patients in the safety analysis set, 70 (73.7%) achieved the MR4.5 by prior ima- tinib treatment and 25 (26.3%) by prior nilotinib treat- ment. Comparing patients in different subgroups based on prior TKI therapy (‘imatinib only’ versus ‘nilotinib follow- ing imatinib’), there were no significant differences except in the duration of imatinib therapy and time to MR4.5 (Online Supplementary Table S1). Of these, 40 patients in the ‘imatinib only’ group, 33 patients in the ‘nilotinib follow- ing imatinib’ group, and five patients in the ‘other’ group entered the TFR phase.
Nilotinib was taken twice daily (600 mg/day) for 2 years in the consolidation phase (median dose intensity, 600 mg/day). Patients’ outcomes at the end of the consolida- tion phase at 24 months are summarized in Table 2. Among the 96 patients in the safety analysis set, 18 (18.8%) discontinued the study treatment. The most fre- quent reason for discontinuation was adverse events; dis- ease progression was not observed in any of the patients.
Treatment-free remission after nilotinib discontinuation
Among the 96 patients in the safety analysis set, 78 with sustained MR4.5 during the consolidation phase were eligi- ble for nilotinib discontinuation in the TFR phase. The median follow-up of patients in the TFR phase was 35.4 months (range, 1.8–44.2). Among the 78 patients, 53 remained in the TFR phase without a confirmed loss of MR4.5 in the first 12 months; the 12-month TFR primary endpoint was 67.9% (95% CI: 56.4–78.1%), exceeding the targeted 40% success rate. The 24-month TFR rate was 62.8% (95% CI: 51.1–73.5%). The Kaplan-Meier curve for
Table 2. Patients’ outcomes and dose intensity at the end of the 2-year nilotinib consolidation phase.
Age (years)
Sex Male Female
Sokal risk Low
SAS (n=96) before entering
the consolidation phase
55.5 (20–83)
60 (62.5)
36 (37.5)
56 (59.6) 20 (21.3) 18 (19.1)
16 (16.7)
50 (52.1) 40 (41.7) 6 (6.3)
75.6 (8–131)
73.6 (11–126) 7.7 (0–35) 5.6 (1–63) 14.5 (3–103) 48.1 (6–128)
70 (73.7)
25 (26.3) 96 (100)
29 (30.2)
FAS (n=78) before entering the TFR phase
57.0 (22–85)
45 (57.7)
33 (42.3)
44 (57.1) 17 (22.1) 16 (20.8)
12 (15.4)
40 (51.3) 33 (42.3) 5 (6.4)
99.0 (25–156)
74.9 (11–125) 25.3 (23–60) 5.5 (1–63) 14.2 (3–103) 47.9 (6–128)
58 (75.3)
19 (25.7) 78 (100)
41 (52.6)
Intermediate High
Prior interferon-a
Prior TKI before the trial Only imatinib
Nilotinib following imatinib Other
Total duration of TKI
treatment (months)
Duration of imatinib (months)
Duration of nilotinib (months)
Time to CCyR (months)
Time to MMR (months)
Time to MR4.5 (months)
Treatment at achieving MR4.5 Imatinib
Nilotinib
Molecular status MR4.5
UMRD with MR5
Dose reduction
Interruption
Treatment discontinuation Adverse events Confirmed loss of MR4.5 Withdrawal of consent Lost to follow-up
Other
Duration of nilotinib (days)
Dose intensity of nilotinib (mg/day)
SAS (n=96)
14 (14.6)
13 (13.5)
18 (18.8) 6 (6.3) 3 (3.1) 4 (4.2) 1 (1.5) 6 (6.3)
737.5 (14–859)
600 (204.6–674.5)
Data are given as median (range) or n (%). SAS: safety analysis set; FAS: full analysis set; TFR: treatment free remission; TKI: tyrosine kinase inhibitor; CCyR: complete cyto- genetic response; MMR: major molecular response; MR4.5: 4.5-log reduction of BCR- ABL1 transcripts by IS-PCR; UMRD: undetectable BCR-ABL1 transcript; MR5: 5-log reduction of BCR-ABL1 transcripts by IS-PCR.
Data are given as n (%) or median (range). SAS, safety analysis set; MR4.5, 4.5-log reduc- tion of BCR-ABL1 transcripts by IS-PCR.
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treatment-free survival is shown in Figure 1A. The estimat- ed 3-year treatment-free survival was 62.8%. Among patients with a confirmed loss of MR4.5, 25 patients lost the MR4.5 within the first 6 months after discontinuing nilotinib (median, 3.4 months; range, 1.8–5.8 months), and the remaining four patients lost the MR4.5 between 16 and 20 months within the TFR phase (Figure 1B).
In a subanalysis of groups based on prior TKI before entry into the STAT2 trial, the 12-month TFR rate was 62.5% (95% CI: 45.8–77.3%) in the ‘imatinib only’ group and 69.7% (95% CI: 51.3–84.4%) in the ‘nilotinib follow- ing imatinib’ group. In another subanalysis based on posi- tivity of molecular residual disease (MRD) before the TFR phase, the 12-month TFR rate was 56.8% (95% CI: 39.5–
A
72.9%) in the MRD group and 78.0% (95% CI: 62.4– 89.4%) in the UMRD with MR5 group; the corresponding 24-month TFR rates were 48.6% (95% CI: 31.9–65.6%) and 75.6% (95% CI: 59.7–87.6%).
An analysis of baseline factors as predictors of TFR at 12 months was conducted. With the exception of detectable MRD before entering the TFR phase (odds ratio, 0.369; 95% CI: 0.138–0.988; P=0.0473), there were no significant predictors in the univariate logistic regression analysis, including the absolute number of natural killer cells and natural killer cell cytotoxicity (Table 3). Multivariate analy- sis was not, therefore, performed. On the other hand, the treatment-free survival curve was significantly better in the UMRD with MR5 group than in the MRD group (estimated
Figure 1. Treatment-free remission after 2-year consolidation with nilotinib. (A) Kaplan-Meier estimates of treatment-free survival after discontinuation of nilotinib (n=78). (B) The kinetics of BCR-ABL1 transcripts in the treatment-free remission (TFR) phase. Twenty-five patients lost MR4.5 within 12 months and eight patients showed fluctuations in the amounts of BCR-ABL1 transcript around the MR4.5 level. Among the eight patients with fluctuations, four lost MR4.5 after 16, 16, 17, and 20 months. (C) Kaplan-Meier estimates of treatment-free survival after discontinuation of nilotinib according to the molecular response [molecular residual disease (MRD) positive or undetectable MRD (UMRD with MR5)] at enrollment in the TFR phase. UMRD with MR5 was defined as undetectable BCR-ABL1 transcripts by IS-PCR in which at least 100,000 control genes (ABL1) were required for the sensitivity of MR5. (D) Cumulative incidence of MR4.5 in patients who lost MR4.5 during the TFR phase and were subsequently readministered nilotinib (n=29). (E) Cumulative incidence of reacquisition of major molecular response (MMR) in patients who lost MMR and were readministered nilotinib (n=16).
B
CDE
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3-year treatment-free survival, 75.6 versus 48.6%; P=0.0126 by the log-rank test) (Figure 1C). There were no significant differences in the treatment-free survival curves between subgroups based on TKI treatment prior to the consolida- tion phase by nilotinib (‘imatinib only’ versus ‘nilotinib fol- lowing imatinib’ group, P=0.9508 by the log-rank test), presence of TKI withdrawal syndrome (P=0.4096 by the log-rank test), or absolute number of natural killer cells (≥ median versus < median, P=0.4527 by the log-rank test).
Response to nilotinib treatment re-initiation
Nilotinib was readministered to all 29 patients with a molecular recurrence during the TFR phase. After recom- mencing treatment, MR4.5 rapidly returned in 25 patients (86.2%), with 50% of patients achieving MR4.5 within 3.5 months (Figure 1D). Four out of 29 patients discontinued treatment: one patient discontinued at 1 month because of a nilotinib-associated rash, one at 2.5 months following the patient’s request, and two at 10 and 11 months because of increasing BCR-ABL1IS. Despite discontinuation of the study, all patients, including the two patients with increas- ing BCR-ABL1IS during the re-treatment phase, achieved DMR. The clinical course details of these four patients are shown in Online Supplementary Figure S1. Among 29 patients with a molecular recurrence, 16 had lost their
MMR at the first or second assessment of BCR-ABL1IS using RQ-PCR during the TFR phase. After starting treat- ment again, a MMR rapidly returned in all 16 patients (100%) in 3 months and 50% of patients achieved the MMR within 2 months (Figure 1E).
Safety, vascular adverse events, and tyrosine kinase inhibitor withdrawal syndrome
No patients progressed to accelerated phase or blast cri- sis CML, or died during this study. Adverse events (all grades) were reported in 55 patients (57.3%) in the safety analysis set in the consolidation phase, and 30 patients (38.7%) in the full analysis set in the TFR phase; the inci- dence of grade 3/4 adverse events was 14.6%, and 2.6% in the safety analysis set and full analysis set, respectively (Online Supplementary Table S2).
Vascular adverse events of any grade were reported in six patients (6.2%) during the nilotinib consolidation phase (Table 4). Ischemic heart disease (acute coronary syndrome or angina pectoris) was reported in three patients and cere- bral infarctions in three patients, but peripheral arterial occlusive disease was not reported in any patient. Among the six patients with vascular adverse events, four had at least one traditional risk factor for such events (e.g., hyper- tension, hyperlipidemia, diabetes mellitus, smoking, or
Table 3. Univariate analysis of predictive factors for treatment-free remission at 12 months.
Coefficient SE DF P-value OR
95% CI
0.980–1.055
0.913–1.013
0.945–1.033
0.511–3.808
0.997–1.019
0.629–1.216
0.808–1.054
0.945–1.134
0.764–1.061
0.187–1.916
0.297–2.201
0.240–3.297
0.377–6.248
1.000–1.000
0.998–1.001
0.999–1.001
0.997–1.029
0.138-0.998
1.000–1.000
0.988–1.026
0.984–1.004
0.905–1.033
0.921–1.039
0.997–1.001
0.931–1.033
0.939–1.019
0.960–1.018
Age (years)
Height (cm)
Body weight (kg)
Comorbidity
Platelet count
Blast cells in PB (%)
Eosinophils in PB (%)
Basophils in PB (%)
Spleen size (cm)
Sokal risk (low)
Hasford (low)
0.0168 0.0190 1 0.3769 1.017
-0.0387 0.0265 1 0.1447 0.962
-0.0122 0.0226 1 0.5876 0.988
0.3325 0.5125 1 0.5165 1.395
0.0083 0.0055 1 0.1322 1.008
-0.1340 0.1683 1 0.4259 0.875
-0.0803 0.0680 1 0.2379 0.923
0.0343 0.0466 1 0.4612 1.035
-0.1052 0.0839 1 0.2099 0.900
-0.5124 0.5933 1 0.3878 0.599
-0.2131 0.5112 1 0.6768 0.808
-0.1178 0.6687 1 0.8602 0.889
0.4283 0.7163 1 0.5499 1.535
0.0000 0.0002 1 0.8169 1.000
-0.0005 0.0009 1 0.5240 0.999
0.0001 0.0004 1 0.6993 1.000
0.0126 0.0082 1 0.1227 1.013
-0.9966 0.5025 1 0.0473 0.369
0.0000 0.0000 1 0.3515 1.000
0.0066 0.0097 1 0.4956 1.007
-0.0056 0.0051 1 0.2713 0.994
-0.0335 0.0338 1 0.3207 0.967
-0.0221 0.0306 1 0.4714 0.978
-0.0010 0.0013 1 0.4305 0.999
-0.0191 0.0265 1 0.4723 0.981
-0.0220 0.0208 1 0.2915 0.978
-0.0112 0.0150 1 0.4527 0.989
EUTOS (low)
Prior interferon-a
Duration of imatinib (days)
Time to CCyR (days)
Time to MMR (days)
Time to MR4.5 (days)
MRD positive
Total nilotinib dose (mg)
Duration of nilotinib (days)
Nilotinib dose intensity (mg/day)
T cells (CD3+CD8+)
T-LGL (CD3+CD57+)
NK cells (CD3-CD56+)
NK cells (CD16+CD56+)
NK cell activity E/T ratio 10:1
NK cell activity E/T ratio 20:1
SE: standard error; OR: odds ratio; 95% CI: 95% confidence interval; PB: peripheral blood; CCyR: complete cytogenetic response; MMR: major molecular response; MR4.5: 4.5-log reduction of BCR-ABL1 transcripts by IS-PCR; MRD: molecular residual disease; T-LGL: T-cell large granular lymphocytes; NK: natural killer; E/T: effector-target cell.
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chronic kidney disease). Percutaneous intervention was performed in three patients with ischemic heart disease. All patients, except one, with vascular adverse events recovered or improved. Although three patients with vas- cular adverse events stopped nilotinib treatment and switched to another TKI, three patients continued the study treatment and entered the TFR phase, eventually achieving successful TFR. No patients developed new vas- cular adverse events during the TFR phase.
Arthralgia was reported only in the TFR phase (Online Supplementary Table S2). Eleven patients reported muscu- loskeletal pain events during the early phase of the TFR; these events were categorized as TKI withdrawal syn- drome. The characteristics of the patients with TKI with- drawal syndrome are described in Table 5. The median time of onset of the TKI withdrawal syndrome in the TFR phase was 1 month (range, 0–6). All patients recovered completely with or without treatment. Of the 11 patients with the syndrome, eight (73%) maintained TFR at 12 months and remained in remission throughout the 36- month follow-up period. There were no significant differ- ences in the TFR survival curves between subgroups based on TKI withdrawal syndrome.
Discussion
The design of the STAT2 trial resembled that of the STIM18,9 and TWISTER trials,10 with the aim of adminis- tering a TKI during a 2-year consolidation phase to obtain a sustained DMR before TKI discontinuation. In this trial, in contrast to the aforementioned studies, imatinib was replaced with nilotinib as the consolidation TKI therapy. However, the assessment of BCR-ABL1 and the definition of molecular recurrence in this trial are identical to those in the aforementioned studies.8-10 Nilotinib was adminis- tered instead of imatinib because previous studies had indicated that nilotinib could induce DMR in a greater number of patients than imatinib,1-3 thereby potentially increasing the number of patients who achieve successful TFR. The 2-year period of consolidation therapy in this study was selected as the STIM18,9 and TWISTER10 trials required 2 years of sustained DMR before stopping ima- tinib therapy. Additionally, our retrospective study revealed that a DMR duration of at least 2 years was a significant predictive factor for successful TFR in Japanese CML patients.14 Therefore, the treatment duration for this trial involved a consolidation phase of 2 years, and sus-
Table 4. Treatment-related vascular adverse events in the consolidation phase.
Age Sex Duration (decade) (M/F) of imatinib
(months)
40s M 99.4
70s F 41.5 70s F 87.2 40s F 70.3
80s M 45.7
70s M 124.6
Duration of nilotinib (months)
22.6
22.4 52.6 10.5
24.0
17.9
Traditional risk factors
Hypertension
None Hypertension None
Hypertension
DM, CKD
Vascular CTCAE adverse grade
events
CI 2
ACS 3 AP 3 CI 2
CI 2
ACS 3
Outcome
Improvement
Improvement by PCI Improvement by PCI Recovery
No change
Recovery by PCI
Treatment outcome
Nilotinib discontinuation, switched TKI
Entered TFR phase
Entered TFR phase
Nilotinib discontinuation,
switched TKI
Entered TFR phase
Nilotinib discontinuation,
switched TKI
M: male; F: female; CTCAE: Common Terminology Criteria for Adverse Events; DM: diabetes mellitus; CKD: chronic kidney disease; CI: cerebral infarction; AP: angina pectoris; ACS: acute coronary syndrome; PCI: percutaneous intervention; TFR: treatment-free remission; TRI: tyrosine kinase inhibitor.
Table 5. Tyrosine kinase inhibitor withdrawal syndrome in the treatment-free remission phase.
Age (decade)
50s
50s 50s 30s 60s 30s 50s 50s 40s 50s
60s
Duration of TKI (months)
103
94 120 140 139 99 135
Muscle Time CTCAE pain of WS grade
before DC (months)
WS therapy
None
NSAID
NSAID
NSAID 7 No
Prednisolone 19 No None 13 Yes Prednisolone 26 Yes
None 17 No None 14 Yes
Sex (M/F)
F
F
F
F
F
M
F
F
M
M
Yes
No
No 51 No
0 1
1 2 1 2 1 1
Localization of symptoms
Myalgia, whole body
Arms
Hands, wrists, arms, shoulders, legs
Hands,elbows
Hands, feet
Hands, wrists, shoulders, lower back, legs
Shoulders, legs, knees
Hands, wrists, elbows, arms
Hands, wrists, elbows, arms
Duration of WS
5
TFR at 12 months (months)
Yes
107 124
10 5
Yes Yes
F 88
No 1 3 Yes 1 1 No 2 2 No 3 1 No 3 1 No 5 2 No 6 2
Hands Prednisolone 15 Yes
Hands, wrists, elbows, lower back NSAID 11 Yes
M: male; F: female; TKI: tyrosine kinase inhibitor; DC: discontinuation of nilotinib; WS: withdrawal syndrome; CTCAE: Common Terminology Criteria for Adverse Events (for the highest grade in the TFR phase); TFR: treatment-free remission; NSAID: non-steroidal anti-inflammatory drugs.
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tained DMR without loss of MR4.5 was confirmed by reg- ular BCR-ABL1IS RQ-PCR testing for 2 years.
Among 78 patients who entered the TFR phase, 53 remained in TFR in the first 12 months; the 12-month TFR primary endpoint was, therefore, 67.9% (95% CI: 56.4– 78.1%). Although the TFR rate is higher than that in the STIM1 trial (41%; 95% CI: 29–52%), it is difficult to com- pare this result with those in other TFR studies with vary- ing designs. Among 29 patients with a molecular recur- rence, MR4.5 was rapidly regained in 25 patients who were readministered nilotinib, and no patients progressed to accelerated phase or blast crisis CML in this study. Thus, our findings suggest that nilotinib therapy may allow the majority of patients to achieve successful TFR after discon- tinuation of nilotinib; this result is comparable to those of previous TFR studies with imatinib.8-10
In this study, the identified predictive factor for success- ful 12-month TFR was UMRD with MR5 before discontin- uation of nilotinib. In the EURO-SKI trial, there were no differences in MMR status at 6 months after treatment stop between depths of molecular response (MR4.5 versus no MR4.5).15 However, our finding suggests that a deeper MR favors successful achievement of TFR in CML patients, which is consistent with data from previous studies.16,17 Among four patients without TFR in the late TFR phase, in whom MR4.5 loss occurred at 16, 16, 17, and 20 months, three patients had MRD before entering the TFR phase. It is difficult to determine the quantity of BCR-ABL1 mRNA below MR4.5/MR5 because of the sensitivity of IS-RQ- PCR.18 However, UMRD with MR5 before TFR is one of the minimum requirements for TFR and the sustained duration of DMR might be a surrogate marker for the mag- nitude of the MR or the eradication of MRD during TKI treatment.19,20 Meanwhile, 1-year consolidation with either dasatinib or nilotinib, which are both second-generation TKI, was proposed in the DADI trial11 and the ENEStop study,21 respectively. Although the 1-year consolidation enabled identification of enrolled patients who had sus- tained MR4.5 and were eligible to stop treatment,21 it is still unknown whether 1 year of consolidation with a second- generation TKI is sufficient to achieve DMR/UMRD below MR4.5/MR5 for TFR.
Of the 96 patients in the safety analysis set, 78 achieved a sustained MR4.5 on nilotinib consolidation and entered the TFR phase, including 33 patients (42.3%) who were treated with nilotinib following imatinib prior to enroll- ment in STAT2. Most patients (n=29, 72.5%) were switched from imatinib to nilotinib at the patients’ request prior to the trial, primarily to obtain a deeper and more sus- tained MR, despite not having imatinib resistance or intol- erance. Similarly, the ENESTcmr study showed that a sig- nificant minority of patients who continued with imatinib therapy did later achieve DMR.4 In the subanalysis evalu- ating prior TKI exposure, the 12-month TFR was almost identical between patients treated with only imatinib (62.5%) and those treated with nilotinib following ima- tinib (69.7%). This suggests that, regardless of the specific TKI, DMR is the first step for achieving successful TFR in patients with CML.
The proportion of natural killer cells in peripheral blood has been reported as a predictive marker, which might be related to a previously reported immuno-oncological effect.22,23 However, it was beyond the remit of this trial to
identify the significance of either the activity or the propor- tion or natural killer cells in peripheral blood.
TKI withdrawal syndrome is the most common muscu- loskeletal pain-related adverse event in imatinib TFR stud- ies, being first reported in the EURO-SKI trial.24 TKI with- drawal syndrome was detected in 11 patients in the TFR phase in this study. Rousselot et al. suggested that pro- longed inhibition of c-Kit signaling by imatinib may mod- ulate nociceptive sensitivity, and that the sudden discontin- uation of imatinib may reverse this phenomenon.25 As nilo- tinib targets the same tyrosine kinases as imatinib, includ- ing BCR-ABL kinase and c-Kit, albeit with differing poten- cies, nilotinib may also result in TKI withdrawal syndrome via the same mechanisms. Although TKI withdrawal syn- drome was reported as an independent predictive factor for successful TFR by a Korean group,26 there was no sig- nificant relationship between TKI withdrawal syndrome and TFR identified in this nilotinib TFR study. However, because of the limited number of events during the TFR phase, univariate analysis is definitely limited in identify- ing a significant relationship between TKI withdrawal syn- drome and TFR. Further examination with larger numbers of patients will be necessary to identify biomarkers for suc- cessful TFR.
Although the safety of nilotinib is generally regarded as being acceptable, vascular adverse events are an important concern in nilotinib therapy. The frequency of such events in this study was similar to the frequency in the nilotinib 300 mg twice daily arm in the ENESTnd trial.3 The inci- dence of vascular adverse events in patients treated with nilotinib 300 mg twice daily was estimated to be 2.8 per 100 patient-years in a meta-analysis.27 In the STAT2 trial, all patients with vascular adverse events, except one, either recovered or improved with intervention or supportive care after nilotinib discontinuation. Moreover, three patients achieved TFR after the occurrence of vascular adverse events during the TFR phase of STAT2. Since four of the six patients had at least one traditional risk factor for vascular adverse events, patients should be carefully screened for risk factors prior to nilotinib administration, with appropriate treatment or supportive care of comor- bidities to avoid the development of vascular adverse events. After considering the risk of vascular adverse events in patients given consolidation with nilotinib, we conclude that this therapeutic agent can be safely adminis- tered to achieve a successful TFR in CML patients.
In conclusion, although previous evidence regarding TFR after discontinuation of second-line nilotinib therapy is limited, our study suggests that a 2-year consolidation peri- od of nilotinib therapy can safely induce higher TFR rates in patients with MR4.5. Thus, 2-year consolidation therapy with this agent may be an effective strategy for achieving TFR in large numbers of CML patients.
Acknowledgments
This study was supported by research funding from Novartis Pharmaceuticals to NT. The authors would like to thank all study participants and their families, and the study investigators at partic- ipating study sites. We also thank Professor Takuhiro Yamaguchi for some advice as a biostatician, the STAT data center (EPS, Co.) for monitoring the clinical trial, and Dr. Toshihiro Miyamoto, Dr. Yosuke Minami, and Dr. Hidetaka Niitsu for their cooperation as members of the data and safety monitoring committee.
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Inhibition of protein disulfide isomerase induces differentiation of acute myeloid leukemia cells
Ferrata Storti Foundation
Justyna Chlebowska-Tuz,1,2,3 Olga Sokolowska,1,2,4 Pawel Gaj,1,5
Michal Lazniewski,6,7 Malgorzata Firczuk,1 Karolina Borowiec,1
Hanna Sas-Nowosielska,8 Malgorzata Bajor,1 Agata Malinowska,9 Angelika Muchowicz,1 Kavita Ramji,1 Piotr Stawinski,10 Mateusz Sobczak,2 Zofia Pilch,1 Anna Rodziewicz-Lurzynska,11 Malgorzata Zajac,12
Krzysztof Giannopoulos,12 Przemyslaw Juszczynski,13 Grzegorz W. Basak,14 Dariusz Plewczynski,6,15 Rafal Ploski,10 Jakub Golab1,16 and Dominika Nowis1,2,17
Haematologica 2018 Volume 103(11):1843-1852
1Department of Immunology, Medical University of Warsaw; 2Laboratory of Experimental Medicine, Center of New Technologies, University of Warsaw; 3Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw; 4Postgraduate School of Molecular Medicine, Medical University of Warsaw; 5Laboratory of Human Cancer Genetics, Center of New Technologies, University of Warsaw; 6Laboratory of Functional and Structural Genomics, Center of New Technologies, University of Warsaw; 7Department of Physical Chemistry, Faculty of Pharmacy, Medical University of Warsaw; 8Laboratory of Imaging Tissue Structure and Function, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw; 9Laboratory of Mass Spectrometry, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw; 10Department of Medical Genetics, Center of Biostructure Research, Medical University of Warsaw; 11Department of Laboratory Diagnostics, Faculty of Health Sciences, Medical University of Warsaw; 12Department of Experimental Hematooncology, Medical University of Lublin; 13Department of Experimental Hematology, Institute of Hematology and Transfusion Medicine, Warsaw; 14Department of Hematology, Oncology and Internal Diseases, Medical University of Warsaw; 15Faculty of Mathematics and Information Science, Warsaw University of Technology, Warsaw; 16Center for Preclinical Research and Technology, Medical University of Warsaw and 17Genomic Medicine, Medical University of Warsaw, Poland
ABSTRACT
Acute myeloid leukemia is a malignant disease of immature myeloid cells. Despite significant therapeutic effects of differ- entiation-inducing agents in some acute myeloid leukemia sub- types, the disease remains incurable in a large fraction of patients. Here we show that SK053, a thioredoxin inhibitor, induces differenti- ation and cell death of acute myeloid leukemia cells. Considering that thioredoxin knock-down with short hairpin RNA failed to exert antiproliferative effects in one of the acute myeloid leukemia cell lines, we used a biotin affinity probe-labeling approach to identify potential molecular targets for the effects of SK053. Mass spectrome- try of proteins precipitated from acute myeloid leukemia cells incubat- ed with biotinylated SK053 used as a bait revealed protein disulfide isomerase as a potential binding partner for the compound. Biochemical, enzymatic and functional assays using fluorescence life- time imaging confirmed that SK053 binds to and inhibits the activity of protein disulfide isomerase. Protein disulfide isomerase knock- down with short hairpin RNA was associated with inhibition of cell growth, increased CCAAT enhancer-binding protein a levels, and induction of differentiation of HL-60 cells. Molecular dynamics simu- lation followed by the covalent docking indicated that SK053 binds to the fourth thioredoxin-like domain of protein disulfide isomerase. Differentiation of myeloid precursor cells requires the activity of CCAAT enhancer-binding protein a, the function of which is impaired in acute myeloid leukemia cells through various mecha- nisms, including translational block by protein disulfide isomerase.
Correspondence:
d.nowis@cent.uw.edu.pl or jakub.golab@wum.edu.pl
Received: February 3, 2018. Accepted: July 10, 2018. Pre-published: July 12, 2018.
doi:10.3324/haematol.2018.190231
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1843
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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SK053 increased the levels of CCAAT enhancer-binding protein a and upregulated mRNA levels for differentiation-associated genes. Finally, SK053 decreased the survival of blasts and increased the per- centage of cells expressing the maturation-associated CD11b marker in primary cells isolated from bone marrow or peripheral blood of patients with acute myeloid leukemia. Collectively, these results provide a proof-of-concept that protein disulfide isomerase inhibition has potential as a therapeutic strategy for the treatment of acute myeloid leukemia and for the development of small-molecule inhibitors of protein disulfide isomerase.
Introduction
Acute myeloid leukemia (AML), the most prevalent acute leukemia among adults, is a malignancy of myeloid lineage cells characterized by the inhibition of cell differentiation leading to accumulation of abnormal white blood cells.1 The use of differentiation-inducing agents, such as all-trans retinoic acid and arsenic triox- ide, for the treatment of acute promyelocytic leukemia has brought remarkable therapeutic effects.2,3 However, not all patients with acute promyelocytic leukemia ben- efit from differentiation treatment and there has been no such significant progress in the treatment of other types of AML.4 The development of new therapeutic agents exerting anti-leukemic effects by targeting unique cellular mechanisms of differentiation is still, therefore, a pressing need of clinical importance.5 It is particularly desirable to develop differentiation-promot- ing compounds that induce terminal differentiation of leukemic cells leading to cell cycle arrest followed by cell death, and obviate overt cytotoxicity.
A critical transcription factor involved in the develop- ment and differentiation of myeloid lineage cells is CCAAT enhancer-binding protein a (C/EBPa). In C/EBPa-deficient mice granulocyte differentiation is blocked,6 and C/EBPa expression in bipotential myeloid progenitors is sufficient to induce granulocytic development.7 Dysregulation of C/EBPa activity is fre- quently observed in AML patients. Lack of, aberrant or suboptimal C/EBPa activity can result from genomic mutations in the CEBPA gene,8 transcriptional suppres- sion originating from promoter hypermethylation, or functional inactivation by phosphorylation.9 A transla- tional block that occurs in cells experiencing endoplas- mic reticulum stress has also been reported as a mech- anism leading to C/EBPa downregulation at the mRNA level.10 Various mechanisms such as loss of Ca2+ home- ostasis, inhibition of disulfide bond formation, oxida- tive stress, or hypoxia, lead to endoplasmic reticulum stress, which triggers the unfolded protein response. The role of the unfolded protein response is to restore protein homeostasis and normal endoplasmic reticulum function. Accordingly, this response has been reported to be upregulated in a significant percentage of patients with AML and to be associated with a more favorable course of the disease.10
We have previously developed SK053, a pep- tidomimetic inhibitor of thioredoxin that exerts cytosta- tic/cytotoxic effects and endoplasmic reticulum stress- mediated apoptosis in tumor cells.11 Conspicuously, we have observed that AML cells incubated with SK053 undergo growth arrest followed by differentiation into more mature myeloid stages and cell death. We, there- fore, employed RNA sequencing and a biotin affinity
probe-labeling approach to identify the molecular mechanism of the differentiation-promoting effects of SK053, revealing protein disulfide isomerase (PDI) as a druggable target for AML treatment.
Methods
A detailed description of the methods used can be found in the Online Supplementary Data file.
Culture conditions for the acute myeloid leukemia cell lines
NB4, MOLM14, HS-5 and HL-60 cells were cultured in RPMI 1640 (Sigma-Aldrich) supplemented with 10% heat-inactivated fetal bovine serum (Hyclone), 100 mg/mL streptomycin and 100 U/mL penicillin (P/S, Sigma-Aldrich). KG1 cells were cultured in IMDM (Gibco) supplemented with 20% heat-inactivated fetal bovine serum (Hyclone) and P/S. HeLa cells were cultured in DMEM (Gibco) supplemented with 10% heat-inactivated fetal bovine serum (Hyclone) and P/S. All cells were cultured at 37°C in a fully humidified atmosphere of 5% CO2.
Acute myeloid leukemia cell differentiation assays
Myeloid differentiation was assessed by staining cytospun cells with May-Grünwald-Giemsa as well as in flow cytometry by examining the surface expression of CD11b. A conventional semi-quantitative microscopic nitroblue tetrazolium (NBT; Sigma-Aldrich) assay was used to determine the production of superoxide anion upon stimulation with phorbol myristate acetate in differentiated AML cells. A modified quantitative NBT assay was established and implemented by dissolving the blue formazan particles from equal cell numbers in sodium hydroxide, followed by measurement of absorbance at 620 nm using an ASYS UVM 340 microplate reader (Biochrom, Cambridge, UK).
RNA extraction and quantitative real-time polymerase chain reaction
Total RNA was extracted from HL-60 cells using an RNA purification kit (EurX) and relative gene expression was quanti- fied using a LightCycler II 480 Real-Time PCR System (Roche, Basel, Switzerland), LightCycler Probes Master and hydrolysis probes [Universal Probe Library (UPL), Roche] according to the manufacturer's recommendations.
Westernblot
HL-60 cells were washed twice with ice-cold phosphate- buffered saline, lysed in RIPA buffer (50 mmol/L Tris base, 150 mmol/L NaCl, 1% NP-40, 0.25% sodium deoxycholate, and 1 mmol/L EDTA) or cytoplasmic/nuclear fractions of proteins were extracted using an NE-PER Kit (Pierce). Immunoblotting was done via standard procedures using the antibodies accord- ing to the manufacturer’s instructions.
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Isolation of primary acute myeloid leukemia blasts and evaluation of the anti-leukemic effects of SK053
The study was approved by the Institutional Review Board of the Medical University of Lublin (approval n. KE-0254/71/2010) and the Medical University of Warsaw (approval n. KB 182/2011) and was conducted according to the Declaration of Helsinki. Each patient signed written informed consent to the procedures. Leukemic cells were obtained from the bone mar- row of patients with AML and isolated by 1.077 g/mL Histopaque (Sigma-Aldrich) density gradient centrifugation. Cells were seeded in IMDM culture medium, supplemented with 10% heat-inactivated fetal bovine serum at a density 5×105 cells/mL and incubated for 72 h with SK053. Cytotoxic effects, growth and differentiation upon incubation with SK053 were evaluated with methods described above. 7-AAD staining was used to discriminate dead cells. Additionally, anti-CD33 antibody (BD Biosciences, cat. n. 551378) was used to identify myeloid cells among all peripheral blood mononuclear cells. The patients’ basic characteristics are shown in Online Supplementary Table S11.
Statistical analysis
Data were analyzed using Microsoft Excel 2010 and GraphPad Prism 6.0 for Windows (GraphPad Software Inc., La Jolla, CA, USA) software. The results were analyzed for signif- icance using a two-tailed Student t-test or one-way ANOVA with a Dunnett post-hoc test. Statistical significance was defined as P values <0.05.
Results
SK053 induces differentiation of acute myeloid leukemia cells
HL-60 acute promyelocytic leukemia cells were incu- bated for 24 to 120 h with increasing concentrations of SK053 and cell growth as well as cytotoxic effects were determined by counting viable cells and flow cytometry. SK053 inhibited cell growth in a time- and concentra- tion-dependent manner (Figure 1A). We observed similar cytotoxic effects of SK053 against HL-60 cells grown in cell culture medium alone or on the top of bone marrow stromal cells (HS5) mimicking the interaction between AML blasts and the bone marrow niche (Figure 1B). HL- 60 cells incubated with SK053 also showed features of more mature myelopoietic stages with a decreased nucleus/cytoplasm ratio and a greater reduction of NBT (Figure 1C), corresponding to NADPH oxidase activity. An NBT reduction assay (Figure 1D) as well as increased surface levels of CD11b measured in flow cytometry (Figure 1E) confirmed the differentiation-promoting effects of SK053. Quantitative real-time polymerase chain reaction analysis revealed that incubation of HL-60 cells with SK053 resulted in increased levels of tran- scripts for differentiation-associated genes, such as dif- ferentiation-driving transcription factors (CEBPB, CEBPE), early markers of neutrophil differentiation (HK3) and genes expressed by mature granulocytes (CSF3R encoding G-CSFR, CSF2R encoding GM-CSFR, ELANE and MPO) (Figure 1F). Cytostatic/cytotoxic and differentiation-promoting effects of SK053 were also observed in NB4, another acute promyelocytic leukemia cell line, as well as in non-acute promyelocytic leukemia AML cell lines, such as MOLM14 and KG1 (Online Supplementary Figure S1).
SK053 induces gene expression profile associated with stress response and differentiation
To get further insight into the mechanisms of SK053 activity in AML cells, we sequenced and analyzed tran- scriptomes of controls and SK053-treated HL-60 cells using next-generation sequencing. Analysis of transcrip- tomes of controls and HL-60 cells incubated with SK053 for 48 h (Online Supplementary Figure S2) revealed differen- tial expression of genes (Online Supplementary Figure S3A, Online Supplementary Table S1) that, in gene ontology analysis, clustered into two major groups: (i) biological processes (Online Supplementary Figure S3B, Online Supplementary Table S2) involving the stress response (e.g. genes encoding calreticulin or proteasome subunits), reg- ulation of apoptosis (e.g. genes encoding Bcl-2-related protein, CFLAR or TNFRSF10B) and myeloid cell differen- tiation (CBFB, JAK2 or PIR) and (ii) molecule function (Online Supplementary Figure S3C, Online Supplementary Table S3) associated with changes in oxidoreductases activity [e.g. NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, ATP synthase or cytochrome c]. Furthermore, a 5-day incubation of HL-60 cells with SK053 induced the expression of genes regulating myeloid cell differentiation (JUN, CSF1, ID2) and cell pro- liferation (BCL6, PNMT) (Online Supplementary Figure S4A-C, Online Supplementary Tables S4-S6). Immunoblotting of the lysates of HL-60 cells confirmed the results of the next-generation sequencing analysis showing that SK053 induces endoplasmic reticulum stress and the unfolded protein response (Online Supplementary Figure S5).
SK053 binds to and inhibits protein disulfide isomerase
We then used lentiviral particles encoding short hairpin RNA (shRNA) to target thioredoxin in HL-60 cells. Intriguingly, thioredoxin knock-down with shRNA failed to inhibit the growth of HL-60 cells (Online Supplementary Figure S6A). Subsequently, we used two other shRNA sequences targeting thioredoxin (Online Supplementary Figure S6B) and assessed the effects of thioredoxin knock- down in HL-60 and MOLM14 cells. While both hairpins effectively suppressed the growth of MOLM14 cells, only one shRNA slightly inhibited and the other had no effect on the growth of HL-60 cells (Online Supplementary Figure S6C,D). These observations indicate that inhibition of thioredoxin might not be responsible for the differentia- tion-inducing effects of SK053 in HL-60 cells. Therefore, using a biotin affinity probe-labeling approach followed by mass spectrometry, we sought to identify other poten- tial intracellular SK053 targets in these cells. Incubation of HL-60 cells for 4 h with SK-BIO, an active, biotinylated SK053 analog (see Online Supplementary Figure S8 for the general structures of compound used herein), followed by pulldown with avidin-coated beads and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), revealed a prominent band of ~50-70 kDa molecular weight in silver-stained gels (Figure 2A). An inactive, biotinylated analog of SK053 that lacks the electrophilic double bond (referred to as SK-IN, Online Supplementary Figure S8) failed to precipitate any protein. The ~50-70 kDa protein was identified in mass spectrometry to be a protein disulfide isomerase (PDI), a product of the P4HB gene (Online Supplementary Figure S9A-D, Online Supplementary Table S7). SDS-PAGE followed by the
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Figure 1. SK053 induces differen- tiation of AML cells. (A) HL-60 cells were incubated with various concentrations of SK053 for up to 5 days. Each day the number of dead cells was evaluated with try- pan blue exclusion (mean ± SD from 6 experiments). (B) Co-cul- ture of HL-60 cells with universal bone marrow stromal cells (HS5) did not impair SK053 cytotoxicity. HL-60 cells were seeded in a tran- swell system on top of HS5 cells and incubated with SK053 for 72 h. Next, HL-60 cells were analyzed for viability using propidium iodide (PI) staining in flow cytometry (data are shown as mean percent- ages of PI-positive cells ± SD from 3 experiments); *P<0.05 in one- way ANOVA with the Dunnett post- hoc test. (C) May-Grünwald- Giemsa (MGG) staining (upper panel) and nitro-blue tetrazolium (NBT) (lower panel) in HL-60 cells incubated with SK053 for 120 h. All-trans retinoic acid (ATRA) served as a positive control. (D) Semi-quantitative colorimetric NBT reduction assay in HL-60 cells incubated for 5 days with 10 mM SK053 (data are shown as mean increases, in %, over controls ± SD for 3 experiments); *P<0.05 in one-way ANOVA with the Dunnett post-hoc test. (E) Mean percent- age ± SD of HL-60 cells expressing CD11b myeloid marker was deter- mined in flow cytometry in 3 experiments; *P<0.05 in one-way ANOVA with the Dunnett post hoc test. (F) Real-time quantitative polymerase chain reaction analy- sis of HL-60 cells incubated for 5 days with 10 mM SK053; results are presented as mean target-to- reference ratio ± SD of three experiments; *P<0.05 vs. con- trols, two-tailed Student t test, #P<0.05 vs. controls, one-tailed Student t test.
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Figure 2. SK053 binds to protein disulfide isomerase. (A) HL-60 cells were incubated with 100 mM SK-BIO and lysed. Proteins binding SK-BIO were precipitated with avidin-coated beads and eluted with buffers E1 and E2 as described in the Methods section. Next, the samples were separated by SDS-PAGE. A band obtained with buffer E1 (black rectangle) was excised from silver-stained gel and analyzed by mass spectrometry. An inactive biotinylated SK053 analog (SK-IN) was used as a neg- ative control. A representative result of a series of experiments is presented. (B) Recombinant human (rhu) PDI was incubated with a 10× molar excess of SK-BIO for 10-120 min at 37°C (left) or preincubated for 1 h with a 10× molar excess of SK053 followed by 1 h incubation with a 10× molar excess of SK-BIO (right). Next, proteins were separated by SDS-PAGE followed by western blotting (WB) using anti-biotin monoclonal antibody. Membranes stained with Ponceau red served as load- ing controls. A representative result of a series of experiments is presented. (C) Reduced (red) and oxidized (ox) rhuPDI were incubated with SK-BIO followed by immunoblotting for biotin. Gels stained with Coomasie blue served as loading controls. SK-IN was used as a negative control. A representative result of a series of experiments is presented. (D) The lysates of HL-60 cells were incubated with SK-BIO followed by biotin immunoprecipitation and western blotting. Biotin detection in total cell lysates (input) was used as a loading control. Lysate incubated with protein G agarose beads in the absence of antibodies was used as a negative control (No Ab). A representative result of a series of experiments is presented. IP: immunoprecipitation; TXN: thioredoxin.
detection of biotin revealed covalent binding of SK-BIO to recombinant human (rhu) PDI (Figure 2B). Oxidation of rhuPDI, which decreases the number of sulfhydryl groups, reduced binding of SK-BIO to PDI indicating a thiol-dependent interaction (Figure 2C). Moreover, in a competition assay, pre-incubation of rhuPDI with SK053 prevented binding of SK-BIO, indicating the same binding site for both compounds (Figure 2B).
Immunoprecipitation of PDI and thioredoxin from the lysates of HL-60 cells cultured with SK-BIO revealed the presence of biotinylated PDI but not thioredoxin (Figure 2D), indicating that in HL-60 cells PDI is a preferential tar- get for the compound. Further mass spectrometry revealed that SK053 binds to the catalytic cysteines local- ized in the fourth thioredoxin-like domain of PDI (Online Supplementary Figure S9E). Furthermore, the molecular dynamics simulation followed by covalent docking of SK053 to the fourth thioredoxin-like domain of human PDI (pdb|4ekz) indicated that the binding of the truncated form of SK053 (a molecule without the leaving group, Online Supplementary Figure S8D) is equally likely to occur by forming a covalent bond with either sulfur from Cys397 or Cys400 (Online Supplementary Figure S10, Online Supplementary Movie 1). Next, we sought to deter- mine whether binding of SK053 translates into inhibition of PDI activity. A turbidimetric assay of PDI-mediated insulin reduction revealed that SK053 efficiently blocks the enzymatic activity of rhuPDI with an IC50 value of
9.98 mM (Figure 3A,B). To further investigate whether SK053 can inhibit PDI activity in cells, we transfected HeLa cervical cancer cells with a plasmid encoding an endoplasmic reticulum-tuned fluorescent redox-respon- sive probe (roGFPiE)12 and measured the response of this probe using fluorescence lifetime imaging in a time-corre- lated single-photon counting mode. The fluorescent life- time of the probe declined in SK053-treated HeLa cells, reflecting the reductive shift in the dithiol-disulfide steady state and indicating SK053-mediated inhibition of PDI activity in the endoplasmic reticulum of living cells (Figure 3C).
Inhibition of protein disulfide isomerase increases C/EBPa levels and inhibits the growth of acute myeloid leukemia cells
Recently, it was shown that PDI interacts with the stem loop region of mRNA for C/EBPa thereby blocking its translation.13 Considering that C/EBPa is a crucial tran- scription factor driving myeloid cells differentiation14,15 we investigated the effects of SK053 on C/EBPa levels in AML cells. Incubation of HL-60 cells with SK053 increased the nuclear levels of the 42 kDa C/EBPa isoform (Figure 4A) and induced CEBPA mRNA expression (Figure 4C). Additionally, the oncogenic p30 kDa C/EBPa levels were strongly suppressed in cells incubated with SK053 (Figure 4B). Accordingly, SK053 decreased the levels of SOX4 mRNA (Figure 1G), a direct target of C/EBPa, the expres-
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Figure 3. SK053 inhibits enzymatic activity of protein disulfide isomerase. (A) A turbidimetric assay of recombinant human PDI-mediated insulin disulfide reduction (mean ± SD of 6 experiments). (B) Determination of the IC50 value for SK053 with SigmaPlot software. (C) Fluorescence lifetime imaging (FLIM) of HeLa cells trans- fected with plasmid encoding an endoplasmic reticulum-tuned fluorescent redox-responsive probe (roGFPiE) tracking the activity of the PDI in cells; 100 mM dithio- threitol (DTT), a reducing agent, was used as a positive control. A representative result of a series of experiments is presented.
sion of which has been shown to correlate inversely with C/EBPa activity, increased self-renewal of leukemic cells as well as a block in blast differentiation.16 shRNA-mediat- ed knock-down of PDI (P4HB) expression significantly suppressed the proliferation of HL-60 cells (Figure 4D,E). Lentiviral transduction of HL-60, MOLM14 and KG1 cells with another shRNA sequence confirmed that PDI knock- down is associated with significant growth suppression (Figure 4F,G) and upregulates C/EBPa protein (Online Supplementary Figure S7A). PDI knock-down also increased the percentage of CD11b+ HL-60 cells as compared with nontargeting controls, but failed to do so in MOLM14 and KG1 cells (Figure 4H). Unexpectedly, SK053 strongly sup- pressed the growth and induced differentiation of HL-60 cells transduced with two independent shRNA sequences targeting CEBPA (Online Supplementary Figure S7B-D), indi- cating that the presence of this differentiation-associated transcription factor is not necessary for the antileukemic effects of SK053.
Protein disulfide isomerase inhibition targets leukemia-initiating cells and is effective in primary acute myeloid leukemia cells
AML is characterized by a small population of self- renewing leukemic stem cells referred to as leukemia-ini- tiating cells that give rise to a large population of imma- ture leukemic blasts.17 Since leukemia-initiating cells are intrinsically resistant to chemotherapeutics and AML fre- quently relapses due to incomplete elimination of leukemia-initiating cells18 we sought to investigate the effects of SK053 on the survival of CD123+CD34+CD38-
leukemia-initiating cell-like cells within the KG1 AML cell line. We observed a concentration-dependent decrease in the percentage of these cells when incubated with SK053 (Figure 5A,B). Moreover, pretreatment of KG1 cells with SK053 decreased the clonogenic potential of these cells in a colony formation assay in vitro (Figure 5C,D). Moreover, SK053 exerted antileukemic effects in primary AML blasts isolated from bone marrow or peripheral blood of AML patients. We observed a decrease in blast survival in all samples from six patients investigated, accompanied by an increased percentage of cells expressing CD11b marker in five out of the six sam- ples (Figure 6).
Discussion
In this study we demonstrate that SK053 induces differ- entiation of AML cells. SK053 has been developed as a thioredoxin inhibitor and was reported to induce endo- plasmic reticulum stress and apoptosis of tumor cells.11 Thus, it was to some extent unexpected to observe that SK053 induces cytostatic/cytotoxic effects against HL-60 cells (Figure 1A,B), while thioredoxin knock-down with shRNA turned out to be largely ineffective in suppressing the growth of these cells (Online Supplementary Figure S6C). This observation prompted us to look for an addi- tional cellular target for SK053. Using biotinylated SK053 as a bait in a biotin affinity probe-labeling approach we observed that SK053 binds to PDI (Figure 2, Online Supplementary Figure S9). Molecular docking confirmed
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Figure 4.SK053 increases CEBPA levels in HL-60 cells and protein disulfide isomerase knock-down impairs the growth of acute myeloid leukemia cells and induces differenti- ation of HL-60 cells. (A) HL-60 cells were incubated for 2 or 5 days with 10 mM SK053. Subcellular fractions were isolated using a NE-PER kit. HDAC2 served as a loading control for the nuclear fraction. A representative result of a series of experiments is presented. (B) HL-60 cells were incubated for 1-120 h with 10 mM SK053, harvested, lysed and total cell lysates were immunoblotted for 30 kDa C/EBPa. a-tubulin levels served as a loading con- trol. A representative result of a series of experiments is presented. For (A) and (B) the con- trols are HL-60 cells incubated with dimethylsulfoxide at the same concentration as used for SK053-treated group, harvested on day 5. (C) Real-time quantitative polymerase chain reaction of HL-60 cells incubated for the indicated times with 10 mM SK053; results are presented as mean target-to-reference ratio ± SD of three experiments. (D) Western blot showing the efficacy of PDI or thioredoxin (TXN) knock-down 5 days after transduction with shRNA-encoding lentiviruses. PDI(a) and PDI(b) indicate two different shRNA; β-actin (βA) served as a loading control. (E) Growth of HL-60 cells transduced with non-targeting (NTC), TXN [TXN(a)]- or PDI [PDI(b)]-targeting shRNA lentiviral particles. Cells were counted daily in trypan blue from day 1 until day 8. *P<0.05 vs. NTC in a two-tailed Student t-test. For (C) and (D) the controls are non-modified HL-60 cells. (F) Western blot showing the efficacy of PDI knock-down in AML cell lines transduced with PDI-targeting shRNA [PDI(d)]-encod- ing lentiviruses. GAPDH served as a loading control. (G) Growth of HL-60, MOLM14 and KG1 cells transduced with non-targeting (NTC) or PDI-targeting [PDI(d)] shRNA lentiviral particles. Cells were counted daily in trypan blue from day 1 until day 9. *P<0.05 vs. NTC in a two-tailed Student t-test. (H) Mean percentage ± SD of AML cells modified with non- targeting (NTC) or PDI-targeting [PDI(d)] shRNA, expressing CD11b myeloid marker deter- mined in flow cytometry (n=4 experiments, except for KG1: n=2), ***P<0.0001 vs. NTC, two-tailed Student t-test; NS: not significant.
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Figure 5. SK053 decreases the percentage of KG1 leukemia-initiating cells and their clonogenic potential in vitro. (A) KG1 cells were incubated for 72 h with the indicated concentrations of SK053, harvested and stained for flow cytometry. Representative density plots from a series of experiments are presented. (B) Mean per- centages of CD123+ KG1 cells among CD34+ and CD38– cells ± SD (n=3 experiments) *P<0.05 vs. controls, one-way ANOVA with Dunnett post-hoc test. (C) Representative pictures of the clonogenic assay plates on day 14 after seeding KG1 cells pretreated for 72 h with SK053. (D) Mean clone size (pixel area) ± SEM (n=3 experiments); **P<0.0001 vs. controls, one-way ANOVA with Dunnett post-hoc test.
the feasibility of this interaction (Online Supplementary Figure S10) and further precipitation, as well as enzymatic and functional analyses, revealed that SK053 binds to and inhibits the activity of human PDI (Figures 2 and 3).
PDI is the original member of a family of PDI proteins that contain a characteristic CXXC motif, with two cys- teine residues forming a disulfide bond that is cleaved by oxidoreductases or by thiol-disulfide exchange. Although all PDI family members contain a thioredoxin-like domain, they differ considerably in size, domain composition and enzymatic properties. PDI is involved in the formation and isomerization of disulfide bonds between cysteine residues of polypeptides as they fold.19 Such disulfide modifications participate in post-translational protein control and affect the functions of many proteins. PDI also participates in the maintenance of cellular homeostasis by mediating oxida- tive protein folding and acts as a chaperone.19 A number of studies indicate that various PDI are highly expressed in multiple cancer types as compared with matched normal tissues and play an important role in supporting cancer progression.19 PDI is induced in tumor cells during the unfolded protein response and has been associated with chemoresistance.20,21 Inhibition of PDI activity with a non-
selective inhibitor, bacitracin, enhanced apoptosis triggered by bortezomib or fenretinide.22 Propynoic acid carbamoyl methyl amide (PACMA31), an irreversible PDI inhibitor, exhibited significant antitumor effects in ovarian cancer models23 and potentiated the antitumor effects of sorafenib in hepatocellular carcinoma.24 A structurally different PDI inhibitor (CCF642) was shown to exert anti-myeloma activity associated with the induction of endoplasmic retic- ulum stress and apoptosis-inducing calcium release.25 All these observations indicate that PDI is a potential drug tar- get in cancer treatment.
Remarkably, Heafliger et al. have shown that PDI binds to the stem loop region of C/EBPa mRNA, thereby block- ing its translation.13 Our results indicate that SK053 upreg- ulates C/EBPa levels (Figure 4), downregulates its down- stream effector SOX4, and induces differentiation of AML cells (Figure 1F). However, despite C/EBPa upregulation we have observed that SK053 still exerts potent growth- inhibitory effects in HL-60 cells with stably suppressed CEBPA expression induced by two different shRNA sequences (Online Supplementary Figure S7). Thus, it seems unlikely that PDI inhibition with SK053 directly leads to stabilization of CEBPA mRNA. Nonetheless, PDI knock-
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Figure 6. SK053 exerts antileukemic effects and induces differentiation of primary leukemic blasts isolated from the bone marrow of patients with acute myeloid leukemia. (Left) Primary AML blasts isolated from six patients (numbered consecutively Pt 1 to Pt 6) were incubated with the indicated concentrations of SK053 for 72 h. Each day the number of dead cells was evaluated with trypan blue exclusion. Graphs present mean percentages of dead cells ± SD (n=6 experiments). *P<0.05 vs. controls, one-way ANOVA with Dunnett post-hoc test. (Right) Primary AML blasts isolated from six patients were incubated with the indicated concen- trations of SK053 for 72 h. Percentages of CD11b+ cells among live (7-AAD-) and CD33+ cells were evaluated in flow cytometry. Graphs present mean percentages of dead cells ± SD (n=3 experiments). *P<0.05 vs. controls, one-way ANOVA with Dunnett post-hoc test.
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down with shRNA (Figure 4) exerted cytostatic/cytotoxic effects in HL-60, MOLM14 and KG1 cells and induced dif- ferentiation of HL-60 cells. In contrast to HL-60 cells, thioredoxin knock-down in MOLM14 and KG1 cells was also associated with inhibition of cell growth. Thus, it seems that both thioredoxin and PDI are involved in the survival of these cells, and since SK053 targets both enzymes, the antileukemic activity of this compound can be attributed to its dual selectivity. The findings that SK053 significantly decreases the percentage of CD123+CD34+CD38– leukemia-initiating cells and decreases the clonogenic potential of these cells in the colony formation assay in vitro are particularly important. Leukemia-initiating cells seem to have a pivotal role in the relapse of AML and are considered to be resistant to con- ventional chemotherapy and targeted therapies.26
induces differentiation of AML cells. These observations indicate that PDI is a druggable target for differentiation treatment in AML.
Acknowledgments
The authors thank Dr. Magdalena Winiarska from the Department of Immunology, MUW and Prof. Andrzej Dziembowski from the Institute of Biochemistry and Biophysics PAS for their critical and helpful review of this work as well as Dr. Tomasz Stoklosa from the Department of Immunology, MUW for advice concerning the clonogenic assays. This work was supported by the Polish National Science Center, grant numbers: 2013/10/E/NZ5/00778 (DN), 2014/15/B/ST6/05082 (DP), Foundation for Polish Science (TEAM to DP), Ministry of Science and Higher Education, grant number: IP2011 038971 (DN) and European Commission Horizon 2020 Programme 692180- STREAMH2020-TWINN-2015 (JG).
Altogether, we show that SK053 targets PDI by thiol- dependent interactions, modulates C/EBPα levels and
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15. Pulikkan JA, Tenen DG, Behre G. C/EBPalpha deregulation as a paradigm for leukemogenesis. Leukemia. 2017;31(11): 2279-2285.
16. Zhang H, Alberich-Jorda M, Amabile G, et al. Sox4 is a key oncogenic target in C/EBPalpha mutant acute myeloid leukemia. Cancer Cell. 2013;24(5):575-588.
17. Bonnet D, Dick JE. Human acute myeloid leukemia is organized as a hierarchy that originates from a primitive hematopoietic cell. Nat Med. 1997;3(7):730-737.
18. Jordan CT. Unique molecular and cellular
features of acute myelogenous leukemia
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Endoplasmic reticulum stress-activated tran- scription factor ATF6alpha requires the disulfide isomerase PDIA5 to modulate chemoresistance. Mol Cell Biol. 2014;34(10):1839-1849.
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]]></page><page Index="113" isMAC="true"><![CDATA[Acute Myeloid Leukemia
Genetics of acute myeloid leukemia in
the elderly: mutation spectrum and clinical impact in intensively treated patients aged 75 years or older
Ferrata Storti Foundation
Victoria V. Prassek,1 Maja Rothenberg-Thurley,1 Maria C. Sauerland,2
Tobias Herold,1,3,4 Hanna Janke,1 Bianka Ksienzyk,1 Nikola P. Konstandin,1 Dennis Goerlich,2 Utz Krug,5 Andreas Faldum,2 Wolfgang E. Berdel,2 Bernhard Wörmann,6 Jan Braess,7 Stephanie Schneider,1 Marion Subklewe,1 Stefan K. Bohlander,8 Wolfgang Hiddemann,1,3,4 Karsten Spiekermann1,3,4 and Klaus H. Metzeler1,3,4
Haematologica 2018 Volume 103(11):1853-1861
1Laboratory for Leukemia Diagnostics, Department of Medicine III, University Hospital, LMU Munich, Germany; 2Institute of Biostatistics and Clinical Research, University of Münster, Germany; 3German Cancer Consortium (DKTK), Partner Site Munich, Germany; 4German Cancer Research Center (DKFZ), Heidelberg, Germany; 5Hospital Leverkusen, Germany; 6Charité – University Hospital Berlin, Germany; 7Department of Oncology and Hematology, Hospital Barmherzige Brüder, Regensburg, Germany and 8Department of Molecular Medicine and Pathology, University of Auckland, New Zealand
ABSTRACT
Acute myeloid leukemia is a disease of the elderly (median age at diagnosis, 65-70 years). The prognosis of older acute myeloid leukemia patients is generally poor. While genetic markers have become important tools for risk stratification and treatment selection in young and middle-aged patients, their applicability in very old patients is less clear. We sought to validate existing genetic risk classification sys- tems and identify additional factors associated with outcomes in inten- sively treated patients aged ≥75 years. In 151 patients who received induction chemotherapy in the AMLCG-1999 trial, we investigated recurrently mutated genes using a targeted sequencing assay covering 64 genes. The median number of mutated genes per patient was four. The most commonly mutated genes were TET2 (42%), DNMT3A (35%), NPM1 (32%), SRSF2 (25%) and ASXL1 (21%). The complete remission rate was 44% and the 3-year survival was 21% for the entire cohort. While adverse-risk cytogenetics (MRC classification) were associated with shorter overall survival (P=0.001), NPM1 and FLT3-ITD mutations (present in 18%) did not have a significant impact on overall survival. Notably, none of the 13 IDH1-mutated patients (9%) reached complete remission. Consequently, the overall survival of this subgroup was sig- nificantly shorter than that of IDH1-wildtype patients (P<0.001). In sum- mary, even among very old, intensively treated, acute myeloid leukemia patients, adverse-risk cytogenetics predict inferior survival. The spec- trum and relevance of driver gene mutations in elderly patients differs from that in younger patients. Our data implicate IDH1 mutations as a novel marker for chemorefractory disease and inferior prognosis. (AMLCG-1999 trial: clinicaltrials.gov identifier, NCT00266136)
Introduction
The incidence of acute myeloid leukemia (AML) is highest among the elderly, with the median age at diagnosis being around 70 years.1 The prognosis of older AML patients is generally considered poor. In this age group, comorbidities, poor performance status and a reluctance of physicians and patients to use treatment regimens perceived as toxic often lead to the decision to avoid induction chemotherapy in favor of less intensive therapies.2-6 On the other hand, data from patient registries and randomized trials suggest that intensive induction therapy
Correspondence:
klaus.metzeler@med.uni-muenchen.de
Received: February 22, 2018. Accepted: June 11, 2018. Pre-published: June 14, 2018.
doi:10.3324/haematol.2018.191536
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1853
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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can result in prolonged overall survival (OS), at least in a subset of elderly patients aged 70-79 years, and may even be beneficial in selected octogenarians.4,7-10 However, it remains unclear which genetic and clinical factors are rel- evant to identify those elderly patients most likely to ben- efit from, and least likely to be harmed by, induction chemotherapy.11
Advances in the field of molecular genetics and the development of next-generation sequencing expanded our knowledge of recurrently mutated genes in AML and their role in disease pathophysiology, and led to refined risk classifications in younger patients.1,12,13 However, elderly patients were underrepresented or excluded in these stud- ies, and the question thus arises whether the spectrum and prognostic relevance of gene mutations are similar in very old AML patients. Some studies of established genet- ic risk factors indicate that there may be important differ- ences between elderly and younger patients.12,14,15 For example, the FLT3-ITD mutation is a well-recognized adverse prognostic factor in young adults, whereas its impact is reduced or absent in elderly patients.1,7,14,16,17 Therefore, comprehensive genetic analyses in cohorts of very old patients are needed to clarify the relevance of dis- tinct gene alterations in this subset of patients.
To identify prognostic factors associated with clinical outcomes in elderly AML patients, we studied 151 patients aged ≥75 years who received intensive induction therapy. The mutational spectrum in 64 recurrently mutat- ed AML genes was analyzed by targeted next-generation sequencing. We then studied associations of genetic alter- ations with other known prognostic factors, patients’ characteristics, and outcomes. Our aim was to define sub- sets of patients who may benefit from intensive induction therapy. Furthermore, we evaluated the prognostic rele- vance of the British Medical Research Council (MRC) 2010 and European LeukemiaNet (ELN) 2017 risk classifi- cation schemes in this subset of patients.1,18
Methods
previously.12 The median sequencing coverage of the target region across all samples was 520-fold, and 98.8% of the target region was covered at >30-fold. Gene alterations with variant allele fre- quencies of ≥2% were classified as driver mutations, variants of unknown significance or germline polymorphisms.12 The Catalogue Of Somatic Mutations In Cancer (COSMIC), The Cancer Genome Atlas (TCGA) and the Single Nucleotide database (dbSNP) served as databases to compare and classify the muta- tional results.19-21 NPM1,22 FLT3-ITD23 and CEBPA24 mutations were additionally tested using polymerase chain reaction followed by Sanger sequencing and/or fragment analysis.
Written informed consent for inclusion in the clinical trial and genetic analyses was provided by all patients. All study protocols were in accordance with the Declaration of Helsinki and approved by the institutional review boards of each participating center.
Statistical analysis
Associations among gene mutations, and between gene muta- tions and patients’ pretreatment features, were analyzed using the Fisher exact test for categorical variables and the Wilcoxon rank- sum test for continuous variables. The Kaplan-Meier method was used to calculate estimated survival probabilities, with the log- rank test evaluating differences between survival distributions. A multivariate Cox regression model including known risk factors [MRC risk category and Eastern Cooperative Oncology Group performance status (ECOG PS)], and gene mutations that showed a univariate association with OS (at P<0.10), was used to identify factors associated with survival. Statistical analyses were per- formed using SPSS version 24.0 (Chicago, IL, USA). All statistical tests are two-sided, and a P value of ≤0.05 was considered statis- tically significant.
Results
Patients’ characteristics
Patients, treatment, karyotype and molecular analyses
We identified 151 patients aged ≥75 years treated in the AMLCG-1999 trial for whom suitable material for genetic analyses was available. Details of this trial have been pub- lished elsewhere.25 The patients’ baseline characteristics are shown in Table 1. The median age of the subjects was 76 years (range, 75-86). Eighty-one percent of patients had a clinical diagnosis of de novo AML, 15% had secondary AML and 3% had therapy-related AML. Three patients (2%) had high-risk myelodysplastic syndromes (10-<20% bone marrow blasts). Most patients (90%) had an ECOG PS of ≤2. Among 137 patients with cytogenetic data, 82% belonged to the intermediate-risk group according to the MRC 2010 classification, including 52% with cytogeneti- cally normal AML. Only three patients (2%) had favorable cytogenetics, and 16% fell in the MRC adverse-risk group.
We studied 151 patients aged ≥75 years with newly diagnosed AML or high-risk myelodysplastic syndromes (10% - <20% bone marrow blasts; n=3), diagnosed according to World Health Organization criteria, who had suitable bone marrow or peripher- al blood specimens for genetic analysis. All patients received inten- sive induction treatment during the German AML Cooperative Group AMLCG-1999 randomized, multicenter, phase III trial (clin- icaltrials.gov identifier, NCT00266136) between 1999 and 2011. Participants aged ≥60 years were randomized to receive a first induction course with high-dose cytarabine and mitoxantrone (HAM) or with standard-dose cytarabine, daunorubicin and 6- thioguanine (TAD-9). A second HAM induction course was administered from day 21 only if ≥5% residual blasts were present in a bone marrow aspirate taken on day 15. Another cycle of TAD-9 was given as consolidation therapy, followed by monthly cytarabine-based maintenance chemotherapy (Online Supplementary Data). Karyotype analyses were performed central- ly and results were classified according to the 2010 MRC classifi- cation.18
Treatment outcomes
In the overall cohort, the rates of complete remission (CR) and CR with incomplete blood count recovery (CRi) were 44% and 4%, respectively. The median event-free survival (EFS) was 1.7 months. The median relapse-free survival (RFS) for patients achieving a remission was 12 months, and the median OS was 6.0 months (Online Supplementary Figure S1). The 3-year OS rate for the entire study population was 21%, and survival was similar for patients aged 75-79 or 80-86 years (P=0.3) (Online Supplementary Figure S2A). Patients with an ECOG PS of 3 or 4 had shorter OS compared to patients with an ECOG PS of 0-2 (P=0.036) (Online Supplementary Figure S2B),
Molecular analysis encompassed sequencing of 64 genes recur- rently mutated in AML. We analyzed either known mutational hotspots or the entire coding sequence using an amplicon-based approach (Haloplex, Agilent, Boeblingen, Germany) as described
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mostly because of an increased risk of early death within 60 days from starting treatment (26% for patients with an ECOG PS of 0-1, 40% for those with a PS of 2, and 75% for patients with an ECOG PS of 3 or 4). Patients random- ized to HAM induction tended to have longer OS com- pared to patients randomized to TAD induction (median OS: TAD, 3.1 months versus HAM, 7.8 months; P=0.09) (Online Supplementary Results and Online Supplementary Figure S3).
Impact of cytogenetics on survival
Since only three patients had favorable-risk cytogenetics
according to the MRC classification, the favorable- and intermediate-risk groups were analyzed jointly. Patients in the favorable- or intermediate-risk categories had a non- significantly higher remission rate than adverse-risk patients (CR/CRi, 51% versus 27%; P=0.2). The EFS, RFS, and OS of favorable- and intermediate-risk patients were significantly longer than those for adverse-risk patients (EFS: P=0.001; RFS: P=0.006; OS: P=0.001) (Figure 1A and Online Supplementary Figure S4).
Gene mutations and patients’ pretreatment characteristics
We identified a total of 622 driver mutations affecting 64 genes, with a median number of four mutated genes per patient (range, 1-10 mutations/patient) (Online Supplementary Figure S5). Older age (81-86 years versus 75- 80 years) was not associated with a higher number of driv- er gene mutations (P=0.5, data not shown). The most fre- quently mutated genes in this age group were TET2 (63/151, 42%), DNMT3A (53/151, 35%), NPM1 (48/151, 32%), FLT3 (45/151, 30%), SRSF2 (38/151, 25%), ASXL1 (31/151, 21%), and RUNX1 (28/151, 19%) (Table 1, Figure 2A). Compared to previously studied patients aged <60 or 60-74 years12, those aged ≥75 years had a higher frequency of TET2, SRSF2 and ASXL1 mutations. TP53 mutations occurred in 14% of patients (21/151) and were strongly associated with complex karyotypes (P<0.001). Eighty- three percent of patients (126/151) harbored one or more
A
B
Figure 1. Overall survival according to the MRC and ELN risk classifications. (A) Overall survival for patients in the favorable- and intermediate-risk groups (green) compared to the adverse-risk group (red) according to the MRC cytogenetic risk cat- egory. (B) Overall survival for patients in the favorable-(green), intermediate- (orange) and adverse-risk groups (red) according to the ELN 2017 genetic category.
Table 1. Patients’ baseline characteristics. Variable
Age [years], median (range)
Male sex
Disease type
De novo AML
Secondary AML Therapy-related AML MDS (10%-<20% blasts)
ECOG performance statusa 0
1 2 ≥3
WBC [×109/L], median (range)
Blast count at diagnosis
% bone marrow blasts, median (range)
% peripheral blood blasts, median (range)
MRC cytogenetic risk categoryb Favorable
Intermediate
Adverse
ELN 2017 genetic groupc Favorable Intermediate
Adverse
Remission status after induction CR
CRi
Persistent AML
Death during induction
Most commonly mutated genes
TET2 DNMT3A NPM1 SRSF2 ASXL1 RUNX1 FLT3-ITD NRAS IDH2 TP53 FLT3-TKD IDH1
Total cohort (n=151)
76 (75 – 86)
81 (54%)
122 (81%) 22 (15%) 4 (3%) 3 (2%)
13 (10%) 70 (51%) 42 (31%) 12 (9%)
14.2 (0.1 – 318.1)
80 (10 – 100)
26 (0 – 100)
3 (2%) 112 (82%) 22 (16%)
37 (28%) 32 (24%) 65 (49%)
66 (44%) 6 (4%) 25 (17%) 54 (35%)
63 (42%) 53 (35%) 48 (32%) 38 (25%) 31 (21%) 28 (19%) 27 (18%) 25 (17%) 23 (15%) 21 (14%) 18 (12%) 13 (9%)
ECOG: Eastern Cooperative Oncology Group; WBC: white blood cell count; MRC: British Medical Research Council; ELN: European LeukaemiaNet; CR: complete remis- sion; CRi: complete remission with incomplete blood count recovery; ITD: internal tandem duplication; TKD: tyrosine kinase domain. aNo data available for 14 patients; bNo karyotype was available for 14 patients; cClassification was not possible for 17 patients due to lack of karyotype or FLT3-ITD allelic ratio.
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mutations in TET2, DNMT3A, SRSF2, ASXL1, TP53 or SF3B1 - genes known to be involved in age-associated clonal hematopoiesis (Figure 2B).26,27 RUNX1 mutations were positively associated with mutations in SRSF2 and ASXL1 (SRSF2, P=0.02; ASXL1, P=0.01), while ASXL1 and DNMT3A mutations were inversely correlated with each other (P=0.003). NPM1 mutations were mutually exclu- sive with RUNX1 mutations, and only two patients had co-mutations in NPM1 and ASXL1 (P<0.001) (Figure 2B).
Association between gene mutations, therapy response and survival
The number of mutated genes per patient was not asso- ciated with OS in a comparison of patients with one to three (62/151, 41%), four to seven (80/151, 53%) or eight to ten (9/151, 6%) mutated genes (P=0.6) (Online Supplementary Figure S6).
Univariate analyses of the associations between the most common gene mutations and CR rate and OS are shown in Online Supplementary Table S1. NPM1 muta- tions, which have been shown to be associated with a higher CR rate in younger AML patients, were not associ- ated with response to induction treatment in our cohort. Patients with NPM1 mutations had a significant longer EFS (P=0.027) (Online Supplementary Figure S7A) and tend- ed to have a longer RFS (P=0.081) (Online Supplementary
A
Figure S7B) and OS (P=0.090) (Figure 3A) than wildtype patients. Among patients who achieved CR, those with mutated NPM1 had a significantly longer OS (calculated from the day of achieving CR) than NPM1-wildtype patients (P=0.037) (Online Supplementary Figure S7C). Within the subgroup of patients with cytogenetically nor- mal AML, there was no difference in OS between NPM1- mutated and -wildtype patients (P=0.4, data not shown). Likewise, the OS of NPM1mutated/FLT3-ITDwildtype patients - a known favorable-risk subgroup, at least in younger patients - was similar to that of the rest of the cohort (P=0.59) (Figure 3B).
FLT3-ITD mutations had no impact on EFS, RFS, or OS in the entire cohort [EFS: P=0.54 (Online Supplementary Figure S8A); RFS: P=0.78 (Online Supplementary Figure S8B); OS: P=0.32 (Figure 3C)] or in patients with cytogenetically normal AML (P=0.26) (Online Supplementary Figure S8C). Since the FLT3-ITD allelic ratio is an important prognosti- cator recognized in the ELN 2017 classification, we also explored its impact on OS. A high FLT3-ITD allelic ratio (≥0.5) was not associated with a shorter OS compared to a low allelic ratio (<0.5) or FLT3-ITD wildtype (OS: P=0.53) (Online Supplementary Figure S8D). In the context of co-mutated NPM1, there was also no impact on OS of a high FLT3-ITD allelic ratio compared to a low allelic ratio or to NPM1mutated/FLT3-ITDwildtype patients (OS: P=0.4)
B
Figure 2. Genetic landscape of old acute myeloid leukemia patients. (A) Driver gene mutations in 151 AML patients ≥75 years of age at primary diagnosis. The bar chart shows the 15 most commonly mutated genes in the 151 AML patients aged ≥75 years compared to 664 patients aged <60 and 60-74 at primary diagnosis (data from Metzeler et al.12). (B) Heatmap showing associations between different driver gene mutations. Each column represents one patient.
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(Online Supplementary Figure 7D). Patients with TP53 muta- tions showed trends towards shorter EFS (P=0.079) (Online Supplementary Figure S9A) and OS (P=0.073) (Figure 3D), and had a significantly shorter RFS (P=0.041) (Online Supplementary Figure S9B), compared to TP53-wildtype patients. TP53-mutated patients who achieved CR had a significantly shorter OS (calculated from the day of achieving CR) compared to that of TP53-wildtype patients in CR (P=0.005) (Online Supplementary Figure S9C).
IDH1 mutations: impact on event-free and overall survival, association with patients’ pretreatment characteristics and other gene mutations
In our cohort of old AML patients, the only gene signif- icantly associated with OS in univariate analysis was IDH1 (Online Supplementary Table S1). None of the IDH1 codon R132-mutated patients (13/151, 9%) reached CR/CRi (P<0.001). Consequently, IDH1-mutated patients had a significantly shorter EFS (P<0.001) (Online Supplementary Figure S10A) and OS (P≤0.001) Figure 4A) than IDH1-wildtype patients.
Within this elderly cohort of patients, IDH1-mutated patients showed a trend towards older age (P=0.08) (Online Supplementary Table S2). Furthermore, IDH1- mutated patients tended to have higher platelet counts (P=0.20) and lower WBC counts (P=0.10) than IDH1-wild- type patients. There was no difference in peripheral blood or bone marrow blast counts between IDH1-wildtype and IDH1-mutated patients. IDH1 mutations were associated
A
with cytogenetically normal AML (P=0.069): 10/13 IDH1- mutated patients had a normal karyotype, whereas one patient had a 7q deletion, one had trisomy 8, and kary- otype was unknown for one patient. Further information on clinical characteristics of the 13 IDH1-mutated patients are shown in Online Supplementary Table S3. IDH1 and IDH2 mutations were mutually exclusive (P=0.2), and IDH2 mutations, found in 15% of patients (23/151), had no impact on OS (P=0.5). TET2 mutations were mutually exclusive with IDH1 mutations (P=0.001), and with mutated IDH2 (P=0.002).
Five IDH1-mutated patients also carried NPM1 muta- tions. While patients with NPM1 mutations overall tend- ed to have favorable OS (Figure 3A), IDH1 mutations had a dominant negative prognostic effect even when co- occurring with mutated NPM1 (Figure 4B). Four IDH1- mutated patients had simultaneous FLT3-TKD mutations, an association that almost reached statistical significance (P=0.051). There was no association between IDH1 and FLT3-ITD mutations (P=0.5).
Multivariate analysis of prognostic factors in old, intensively treated acute myeloid leukemia patients
We used a multivariate Cox regression model to identify the most relevant predictors of OS in this cohort of inten- sively treated AML patients ≥75 years (Table 2). In this multivariate model, using the MRC classification, ECOG PS, and IDH1, NPM1 and TP53 mutations as covariates, only IDH1 mutations and the MRC adverse cytogenetic
B
C
D
Figure 3. Overall survival according to gene mutations. (A) NPM1 mutations: overall survival in NPM1-mutated (green) compared to NPM1-wildtype patients (red). (B) NPM1-mutated/FLT3-ITD-negative patients: overall survival in NPM1-mutated/FLT3-ITD-wildtype patients (green) compared to other patients (red). (C) FLT3-ITD muta- tions: overall survival in FLT3-ITD-mutated (red) compared to FLT3-ITD-wildtype patients (green). (D) TP53 mutations: overall survival in TP53-mutated patients (red) compared to TP53-wildtype patients (green). “Mut” denotes mutated and “wt” wildtype.
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risk category had significant negative impacts on OS. There was a trend towards worse OS for patients with poor ECOG PS.
Patients who were characterized by wildtype IDH1, favorable or intermediate cytogenetics and an ECOG PS of 0-2 had a significantly longer median OS than patients who had at least one high-risk feature (mutated IDH1, adverse cytogenetics, and/or performance status ≥3) (3- year OS, 25% versus 5%; P<0.001) (Figure 5).
Association between the European LeukemiaNet 2017 and Medical Research Council classifications
and outcomes
When we applied the novel ELN 2017 genetic risk clas- sification to our cohort of very old patients, more patients were assigned to the favorable- and adverse-risk cate- gories, and fewer patients to the intermediate-risk group, compared to the MRC classification (Table 1). Surprisingly, patients classified as ELN-2017 intermediate- risk had longer OS (median, 10.7 months) compared to both the favorable- and adverse-risk groups (median, 3.4 months and 3.6 months, respectively; P=0.009) (Figure 1B). Furthermore, in the MRC adverse-risk subgroup, all patients died within 2 years, whereas seven ELN-2017 adverse-risk patients survived for 3 years or longer.
A
B
Figure 4. IDH1 mutations and survival. (A) Overall survival in IDH1-mutated patients (red line) compared to IDH1-wildtype patients (green line). (B) Overall survival in NPM1-mutated/IDH1-mutated patients (red line) compared to NPM1- mutated/IDH1-wildtype patients (green line). Mut: mutated; wt: wildtype.
Discussion
Elderly AML patients are frequently underrepresented in clinical trials evaluating induction chemotherapy sched- ules, as well as in studies of the genetic basis of the dis- ease.12,28-30 For example, the widely-used MRC cytogenetic risk categories were derived from a cohort of patients aged 16-59 years.18 This selection bias contrasts with the epi- demiology of AML, which is mostly a disease of elderly patients. While many study groups have excluded older patients from trials involving induction chemotherapy, and less-intensive regimens, including the hypomethylat- ing agents, decitabine and azacitidine, are now widely used in this age group, some studies suggest that a sub- group of old patients may benefit from induction chemotherapy.7,8,10 There is, therefore, a vital need to iden- tify factors that are associated with outcomes and that could support therapeutic decision-making in this diffi- cult-to-treat patient cohort.
We designed our study to focus on a cohort of very old patients (aged 75 years or older) included in a trial of induction chemotherapy. In this age group, the benefits of induction chemotherapy and potential clinical and genetic markers for therapy success or failure are not well defined. We found that, even among very old patients, favorable-
Table 2. Multivariate analysis for overall survival.
Variable
MRC cytogenetic risk group
(adverse vs. favorable/ intermediate)
NPM1-mutated
TP53-mutated
IDH1-mutated
ECOG performance status
HR (95% CI)
2.21 (1.19 – 4.09)
0.97 (0.62 – 1.51) 1.32 (0.69 – 2.49) 3.68 (1.87 – 7.23) 1.68 (0.89 – 3.18)
P
0.012
0.889
0.402 <0.001 0.113
(3-4 vs. 0-2)
HR: hazard ratio; CI: confidence interval; MRC: British Medical Research Council;
ECOG: Eastern Cooperative Oncology Group.
Figure 5. Impact of Eastern Cooperative Oncology Group performance status, Medical Research Council classification and IDH1 mutations on overall survival. Overall survival in patients with an ECOG performance status of 0-2, favorable or intermediate MRC category and IDH1-wildtype compared to patients with an ECOG performance status of 3-4 or MRC adverse category or IDH1 mutation.
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and intermediate-risk cytogenetics remain associated with a relatively favorable OS in a comparison with adverse- risk cytogenetics. This finding is in agreement with that of a retrospective analysis by Heiblig and colleagues.31 In their study, older age (≥75 years in a cohort with an age range of 70-93 years) was also a strong prognostic factor in terms of OS whereas according to our own data, higher age (80-86 years versus 75-79 years) did not associate with OS, potentially due to the fact that only very fit octagenar- ians were enrolled in a trial of induction chemotherapy. Patients in the cohort reported by Heiblig and colleagues received three different treatment modalities: intensive chemotherapy, less intensive treatment (i.e. low-dose AraC, azacitidine or decitabine) or best supportive care only.31 The median OS in patients aged ≥75 years, regard- less of therapy type, was 4.3 months with a 3-year OS rate of 14%, compared to a median OS of 10 months and a 3- year OS rate of 20% in patients aged <75 years. In patients ≥75 years of age who all received intensive chemotherapy, Heiblig and colleagues reported a 3-year OS rate of 24%, which is comparable to the 3-year OS rate of 21% found in our retrospective analysis. Importantly, the analysis by Heiblig and colleagues also showed that long-term sur- vival beyond 3 years was exceedingly rare in patients treated with hypomethylating agents, while survival times exceeding 10 years were observed in intensively treated patients.
Our previous analysis of the mutational landscape in 664 intensively treated AML patients included 288 patients ≥60 years of age at primary diagnosis.12 We reported that the mutational spectrum in older AML patients differed from that in younger patients (<60 years). In this study, we extend this finding to very old patients aged ≥75 years. The five most frequently mutated genes were TET2, DNMT3A, NPM1, SRSF2 and ASXL1.12 The high incidence of TET2, DNMT3A, SRSF2, ASXL1, TP53 and SF3B1 mutations in our patients is in agreement with reports showing that these genes are frequently mutated in age-associated clonal hematopoiesis.26,32 Overall, 83% (126/151) of AML patients ≥75 years carried at least one mutation in one of these six genes.
Recently, Baldus and colleagues published data on the genetic and epigenetic landscape in 93 elderly AML patients (65-90 years) enrolled in a Study Alliance Leukemia (SAL) registry.33 Similar to our results, they iden- tified a high frequency of mutations in DNMT3A, TET2, SRSF2, ASXL1 and RUNX1. Strikingly, NPM1 mutations were much less common (16.1% of patients) than in our cohort (32%). This difference remains unexplained, since there are no obvious differences regarding, for example, the proportion of patients with de novo versus secondary AML which could affect the frequency of NPM1 muta- tions.
We unexpectedly identified IDH1 mutations as the strongest genetic predictor of shorter survival in this age group. The prognostic value of IDH1 and IDH2 mutations in AML has been studied by multiple groups but is still controversial.34,35 While some analyses found no impact on OS,36 others demonstrated associations with poor37-40 or favorable prognosis.28 A recently published meta-analysis of 33 studies found that IDH1 and IDH2 mutations, ana- lyzed jointly, do not affect OS or EFS.34 IDH1 mutations, when analyzed separately, are associated with lower CR rates, shorter EFS and shorter OS. A negative impact of IDH1 mutations on outcomes has also been described in
younger NPM1-mutated/FLT3-ITD-negative patients.37,39 These findings are generally compatible with the results of our study. This meta-analysis also revealed that IDH2- mutated patients had a longer OS than IDH2-wildtype patients, while in our study there was no impact of IDH2 mutations on OS (P=0.53). This discrepancy may be explained by our focus on very old AML patients, among whom the prognostic relevance of gene mutations may differ from that among younger patients. It remains unclear why mutations in two related genes with appar- ently similar functional consequences21,41,42 might have varying or even opposite impacts on OS. The poor out- come of old AML patients with mutated IDH1 needs to be validated in additional cohorts. If the negative prognostic effect of IDH1 mutations in old patients is confirmed in other studies, these patients should not be considered can- didates for induction chemotherapy. Targeted inhibitors of the mutant IDH1 enzyme, which are currently being tested in clinical trials, may become a preferred therapeu- tic approach for these patients in the future.
In our multivariate analysis, results of cytogenetic analy- sis (classified according to the MRC system) were a strong predictor of outcomes. Compared to the MRC risk cate- gories, application of the new ELN-2017 genetic risk clas- sification led to an expansion of the favorable- and adverse-risk categories (Table 1). The inclusion of RUNX1, ASXL1 and TP53 mutations in the ELN adverse-risk cate- gory, in particular, affects the risk classification of this cohort of very old patients in whom these mutations are common. Many patients who were classified as interme- diate-risk based on cytogenetic results alone according to the MRC recommendations are now re-classified into the adverse-risk group. At least in our cohort, however, the MRC cytogenetic risk classification appears to provide better prognostic stratification compared to the ELN-2017 system. Thus, further validation of the ELN-2017 classifi- cation in larger cohorts of elderly patients seems warrant- ed to define its applicability in this age group.
Our finding that in patients aged 75 or older, the prog- nosis of ELN-2017 favorable-risk patients was not better, and may in fact be worse, than that of the intermediate- risk group suggests that favorable molecular markers established in younger patients (e.g., mutated NPM1 without or with a low FLT3-ITD allelic ratio, biallelic CEBPA mutations) have weaker prognostic relevance in elderly patients. Indeed, in our cohort, the NPM1-mutat- ed/FLT3-ITD-negative genotype did not associate with favorable outcomes. NPM1 mutations alone were associ- ated with significantly longer EFS, but there were only trends towards longer RFS and OS. Among patients who achieved CR after induction therapy, those with mutated NPM1 had a significantly longer OS, suggesting that these patients might have benefited from cytarabine-based con- solidation and prolonged monthly maintenance therapy as used in the AML-CG 1999 trial. In contrast, the MRC adverse-risk group, defined by cytogenetic alterations only, had significantly shorter OS compared to the cytoge- netic favorable- and intermediate-risk groups. In contrast to the ELN-2017 adverse-risk group, no MRC adverse-risk patient survived beyond 2.1 years. Thus, karyotype rather than gene mutations appears to be the major factor defin- ing the prognosis in very old, intensively treated AML patients.43
One limitation of our study is that all patients were treated with the same treatment modality - intensive
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chemotherapy. Consequently, we were unable to study interactions between genetic alterations and type of treat- ment (intensive versus not intensive) with regard to patients’ outcomes. However, we found that patients ran- domized to the more intensive induction regimen (HAM) tended to have longer OS compared to those randomized to TAD. While this non-significant difference may be due to the play of chance, the finding that better outcomes were observed in the more intensive arm supports the conclusion that induction chemotherapy is tolerable for selected patients in this age group. Two randomized phase III trials in newly diagnosed AML patients aged ≥65 years compared treatment with the hypomethylating agents, azacitidine and decitabine, to alternative therapies (best supportive care, low-dose cytarabine, or intensive chemotherapy).44,45 The median OS of azacitidine-treated patients was 10.4 months, and that of decitabine-treated patients was 7.7 months, compared to a median OS of 6.0 months in our study. Obviously, these cohorts of patients cannot be compared directly because of their different age ranges and inclusion criteria. While the lower age limit of our analysis was higher than that in the trials of hyp- methylating agents (75 versus 65 years), our cohort repre- sents highly selected patients who were, despite their advanced age, deemed fit enough to undergo induction chemotherapy. Notwhitstanding this obvious limitation, it is noteworthy that the 3-year OS rate in our cohort was nominally higher than the rates in both the trials of hypomethylating agents. In our study, 24 patients (21%)
were still alive 3 years after primary diagnosis, whereas two patients (1%) in the azacitidine and no patient in the decitabine trial were still alive at 3 years. Thus, at least a subset of AML patients may benefit from intensive induc- tion therapy in terms of sustained remissions and long- term survival, even at the age of 75 years or above. Nevertheless, the longer median OS achieved in the trials of hypomethylating agents suggests that these agents may be the preferred choice for many elderly patients.
In clinical practice, the choice between intensive, poten- tially curative chemotherapy or a palliative therapeutic approach in old AML patients should be guided by an evi- dence-based, individualized assessment of the potential risks (e.g., treatment-related mortality) and benefits of intensive chemotherapy. In our study, favorable- and intermediate-risk cytogenetics, IDH1-wildtype status and good performance status characterized a subset of old AML patients who may achieve long-term survival after induction chemotherapy. These patients might be candi- dates for intensive therapy in the absence of medical con- traindications. On the other hand, patients with adverse- risk cytogenetics, IDH1 mutations or poor performance status did not benefit from intensive induction therapy and might fare better with alternative strategies such as hypomethylating agents, or novel targeted agents that have recently been approved or are currently under devel- opment.46 In summary, our results show that clinicians should consider intensive chemotherapy as a therapeutic option even for selected, very old AML patients.
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1Department for Biomedical Research, University of Bern and 2Department of Medical Oncology, Inselspital, Bern University Hospital, Switzerland
Ferrata Storti Foundation
Acute Myeloid Leukemia
MDM2- and FLT3-inhibitors in the treatment of FLT3-ITD acute myeloid leukemia, specificity and efficacy of NVP-HDM201 and midostaurin
Katja Seipel,1,2 Miguel A.T. Marques,1 Corinne Sidler,1 Beatrice U. Mueller2 and Thomas Pabst2
ABSTRACT
Prognosis for FLT3-ITD positive acute myeloid leukemia with high allelic ratio (>0.5) is poor, particularly in relapse, refractory to or unfit for intensive treatment, thus highlighting an unmet need for novel therapeutic approaches. The combined use of compounds target- ing both the mutated FLT3 receptor and cellular p53 inhibitors might be a promising treatment option for this poor risk leukemia subset. We therefore assessed MDM2 and FLT3 inhibitors as well as cytotoxic com- pounds used for conventional induction treatment as single agents and in combination for their ability to induce apoptosis and cell death in leukemic cells. Acute myeloid leukemia cells represented all major mor- phologic and molecular subtypes with normal karyotype, including FLT3-ITD (>0.5) and FLT3 wild type, NPM1 mutant and NPM1 wild type, as well as TP53 mutant and TP53 wild type cell lines. Acute myeloid leukemia cells with mutated or deleted TP53 were resistant to MDM2- and FLT3-inhibitors. FLT3-ITD positive TP53 wild type acute myeloid leukemia cells were significantly more susceptible to FLT3-inhibitors than FLT3-ITD negative TP53 wild type cells. The pres- ence of a NPM1 mutation reduced the susceptibility of TP53 wild type acute myeloid leukemia cells to the MDM2 inhibitor NVP-HDM201. Moreover, the combined use of MDM2- and FLT3-inhibitors was supe- rior to single agent treatment, and the combination of midostaurin and NVP-HDM201 was as specific and effective against FLT3-ITD positive TP53 wild type cells as the combination of midostaurin with conven- tional induction therapy. In summary, the combined use of the MDM2 inhibitor NVP-HDM201 and the FLT3 inhibitor midostaurin was a most effective and specific treatment to target TP53 and NPM1 wild type acute myeloid leukemia cells with high allelic FLT3-ITD ratio. These data suggest that the combined use of NVP-HDM201 and midostaurin might be a promising treatment option particularly in FLT3-ITD positive acute myeloid leukemia relapsed or refractory to conventional therapy.
Introduction
Acute myeloid leukemia (AML) is a clonal hematopoietic disorder characterized by blocked differentiation and deregulated proliferation of hematopoietic precur- sor cells. At the cellular level, specific genetic and epigenetic alterations lead to changes in cellular signaling pathways including the common inactivation of the p53 tumor suppressor axis, and thereby contribute to blocked differentiation and accumulation of leukemic blasts in the blood and the bone marrow. The past decade has witnessed major advances in our comprehension of the biologic hetero- geneity of AML.1 AML genetic variants are assigned into favorable, intermediate and poor risk categories, and a major molecular subgroup within the poor risk AML is characterized by genetic alterations of the FLT3 receptor gene. FLT3 internal tan-
Correspondence:
thomas.pabst@insel.ch
Received: February 20, 2018. Accepted: June 29, 2018. Pre-published: July 5, 2018.
doi:10.3324/haematol.2018.191650
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1862
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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ARTICLE
]]></page><page Index="123" isMAC="true"><![CDATA[Targeting FLT3-ITD in AML
dem duplications (FLT3-ITD) are the most common muta- tions in the FLT3 receptor gene. FLT3-mutated AML account for 25-35% of all AML, and their prognosis is poor, particularly in unfit, refractory or relapsed patients.
Targeting the mutated FLT3 receptor is a promising approach to treat this specific AML subset. Midostaurin (PKC412) is a first generation type III receptor tyrosine kinase inhibitor that has been extensively studied in vitro and in clinical trials as a treatment for AML patients with mutated FLT3.2,3 After successful phase II clinical trials, midostaurin was found to significantly prolong survival of FLT3-mutated AML patients when combined with con- ventional induction and consolidation therapies in a ran- domized phase III clinical trial leading to the first new drug approval in AML in over 40 years.4 Midostaurin is a multi-targeted kinase inhibitor able to block FLT3 auto- phosphorylation and to induce growth arrest and apopto- sis in FLT3-dependent leukemia.5 Midostaurin is orally administered and generally well tolerated as a single agent. Quizartinib (ACC220) and gilteritinib (ASP2215) are second and third generation FLT3 inhibitors currently in evaluation for the treatment of FLT3-mutated AML.6-8
Targeting the p53 antagonist MDM2 is a novel approach to restore the crucial p53 tumor suppressor function in AML cells.9 Idasanutlin (RG7833) is a second generation MDM2 inhibitor that has been studied in vitro and in vivo as a treatment for AML patients with wild type TP53.10 NVP-CGM09711 and NVP-HDM20112 are second genera- tion MDM2 inhibitors that are currently evaluated in sin- gle-agent phase I studies in patients with advanced tumors with wild type TP53 (clinicaltrials.gov identifiers 01760525 and 02143635). Like midostaurin, NVP-HDM201 is orally administered and expected to be well tolerated as single agent.
In this study, we investigated the combined treatment with MDM2- and FLT3- inhibitors, in particular NVP- HDM201 and midostaurin, on AML cells in order to iden- tify a potentially effective treatment specifically for FLT3-ITD AML refractory to or unfit for intensive chemotherapy. The study might provide the rationale for initiating a clinical study in FLT3-ITD AML evaluating this combination.
Methods
Patient samples
Mononuclear cells of AML patients diagnosed and treated at the University Hospital, Bern, Switzerland between 2005 and 2015 were included in this study. Informed consent from all patients was obtained according to the Declaration of Helsinki, and the studies were approved by decisions of the local ethics committee of Bern, Switzerland. Mutational screening for FLT3, NPM1, TP53 and conventional karyotype analysis of at least 20 metaphases were performed for each patient. Peripheral blood mononuclear cells (PBMCs) and bone marrow mononuclear cells (BMMCs) were collected at the time of diagnosis before initiation of treat- ment.
AML cell lines
OCI-AML2 (AML-M4, FLT3wt, DNMT3A R882C, NPM1wt, TP53wt); OCI-AML3 (AML-M4, FLT3wt, DNMT3A R882C, NPM1mut, TP53wt), MOLM-13 (AML-M5, t(9;11), FLT3-ITD, TP53wt), MOLM-16 (AML-M0, FLT3wt, TP53mut), MV4-11 (AML-M5, t(4;11), FLT3-ITD, TP53wt), ML-2 (AML-M4, t(6;11), FLT3wt, TP53mut), PL-21 (AML-M3, FLT3wt, TP53hemi) and HL-60 (AML-M2, FLT3wt, TP53null) cells were supplied by the Leibniz Institute DSMZ, German Collection of Microorganisms and Cell Cultures. AML cells were grown in RPMI 1640 (SIGMA-ALDRICH, St. Louis, MO, USA) supplemented with 20% fetal bovine serum (FBS, Biochrom GmbH, Germany).
Cytotoxicity assays
AML cells were treated with the MDM2 inhibitors NVP- HDM201, NVP-CGM097, idasanutlin (RG7388), the FLT3 inhibitors midostaurin (PKC412), quizartinib (ACC220), gilteri- tinib (ASP2215) or with genotoxic compounds cytarabine and idarubicin in equimolar concentrations. NVP-HDM201 and NVP-CGM097 investigational compounds were supplied by Novartis, Switzerland, whereas RG7833, PKC412, ACC220 and ASP2215 were purchased at MCE (MedChemExpress, Monmouth Junction, NJ, USA). Cytarabine and idarubicin were purchased at Sigma-Aldrich (St.Louis, MO, USA) and SelleckChem (Houston, TX, USA). Cell viability was deter- mined using the MTT-based in vitro toxicology assay (TOX1, Sigma-Aldrich) with four repeat measurements per dosage. Data
Table 1. Genetic variants in AML cell lines.
ID FLT3
HL-60 wt
MOLM-13 ITD MOLM-16 wt
MV4-11 ITD OCI-AML2 wt
A680V
OCI-AML3 wt
TP53
del
wt V173M C238S
wt wt
wt
NPM1 mutated genes
wt NRAS Q61L CDKN2A R80X
wt MLL-AF9 (t9;11) wt MLL V1368L MTOR T571K
wt MLL-ENL (t4;11) wt DNMT3A R635W
MLL K1751*
L287fs DNMT3A R882C
NRAS Q61L PL-21 wt wt wt KRASA146V
P336L P36fs
wt: wild type; ITD: internal tandem duplication; del: deletion
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are depicted as XY graphs with median and interquartile range, as box plots or scatter plots with mean values. Statistical analy- sis was done on GraphPad Prism (version 7, GraphPad software, LaJolla, CA, USA) in grouped analysis and significance calculat- ed by Mann-Whitney test. Combination indexes were calculat- ed on CompuSyn software (version 1.0; ComboSyn, Inc. Paramus, NJ,USA).
Measurement of mRNA expression by qPCR
RNA was extracted from AML cells and quantified using qPCR.
The RNA extraction kit was supplied by Macherey-Nagel, Düren, Germany. Reverse transcription was done with MMLV-RT (Promega, Madison, WI, USA). Real-time PCR was performed on the ABI7500 Real-Time PCR Instrument using ABI universal mas- ter mix (Applied Biosystems, Austin, TX, USA) and gene specific probes Hs00355782_m1 (CDKN1A), Hs01050896_m1 (MCL1) and Hs02758991_g1 (GAPDH) (ThermoFischer Scientific, Waltham, MA, USA). Measurements of CDKN1A and MCL1 expression were normalized with GAPDH values (ddCt relative quantitation). Assays were performed in three or more independ-
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DEF
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Figure 1. Variable responses of AML cell lines to FLT3 and MDM2 inhibitors. Dose response curves in AML cell lines treated with FLT3 inhibitors (A,B,C) and MDM2 inhibitors (D,E,F) as single compound treatment with midostaurin (PKC412) (A), quizartinib (AC220) (B), gilteritinib (ASP2215) (C), idasanutlin (RG7833) (D), NVP- CGM097 (E) or NVP-HDM201 (F), in a variety of AML cell lines (G) and combination treatments with NVP-HDM201 and PKC412, ACC220 or ASP2215 in MOLM-13 cells (H). Combination indexes were calculated according to Chou Talalay.42
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ent experiments. Statistical analysis was done on GraphPad Prism software using two-tailed t-tests (version 7, GraphPad software, LaJolla, CA, USA). Data are depicted in column bar graphs plotting mean with SD values.
Antibodies and cytometry
Staining for apoptosis was done using AnnexinV-CF488A (Biotium, Germany) in AnnexinV buffer and Hoechst 33342 (10 mg/ml) for 15 min. at 37C, followed by several washes. Propidium iodide was added shortly before imaging on the Nucleocounter NC-3000 (ChemoMetec, Allerod, Denmark). For cell cycle analysis cells were incubated in lysis buffer with DAPI (10 mg/ml) for 5 min. at 37°C and analyzed on NC-3000 imager.
Results
Sensitivity of AML cell lines to MDM2 and FLT3 inhibitors
To determine the sensitivity of AML cells to MDM2 and FLT3 inhibitors, AML cell lines were treated with three MDM2- and three FLT3-inhibitors for 24 hours in dose escalation experiments before cell viability assessment. The AML cell lines covered the major morphologic and molecular subtypes including particularly FLT3-ITD and FLT3 wild type, NPM1 mutant and wild type, as well as TP53 wild type, mutant, hemizygous and null cells (Table I). The two FLT3-ITD cell lines MV4-11 and MOLM-13 had high allelic ratios of FLT3-ITD and chromosomal
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Figure 2. Variable responses of AML blast cells to midostaurin and HDM201. Cell viability was determined in AML patient cells treated with midostaurin (PKC412) (A) or NVP-HDM201 (B). AML cells were grouped according to major molecular subtypes (FLT3/TP53/NPM1). Cell viability measurements are depicted in dose response curves (A, B) or with 50nM single compound (C, D), as well as combination treatment of midostaurin with conventional induction therapy (E) or midostaurin with NVP-HDM201 (F). PBM are peripheral blood monocytes of normal controls. AML patient samples were analyzed in groups of at least four individual samples (Online Supplementary Table S1) using GraphPad prism software. Significance is denoted for P<0.05 (*); P<0.005 (**); P<0.0005 (***); P<0.0001 (****); P>0.05 (ns).
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translocations with MLL gene rearrangements. Some cell lines contained additional mutations in driver genes such as DNMT3A (OCI-AML2, OCI-AML3) and RAS genes (OCI-AML3, PL-21). DNMT3a and RAS gene mutations may influence sensitivity to MDM2 or FLT3 inhibitors. The MDM2 inhibitors included idasanutlin (RG7388), NVP-CGM097 and NVP-HDM201. The FLT3 inhibitors included the 1st, 2nd and 3rd generation inhibitors midostau- rin (PKC412), quizartinib (ACC220) and gilteritinib (ASP2215). The FLT3-ITD positive and TP53 wild type cell lines MOLM-13 and MV4-11 were most susceptible to all three FLT3- and all three MDM2-inhibitors (Figure 1). The effects on MOLM-13 cell survival induced by the three FLT3 inhibitors were consistent with IC50 values of 200nM (Figure 1A,B,C). Quizartinib had a greater potency with 70% cell viability after treatment with 10nM com- pound, while midostaurin and gilteritinib had comparable potencies with 90% cell viability at 10nM compound. OCI-AML2 and PL-21 cells showed some response to midostaurin while OCI-AML3, MOLM-16 and HL-60 cells were rather resistant to midostaurin and quizartinib. With respect to gilteritinib, however, OCI-AML3, PL-21 and HL-60 cells showed some response and only MOLM- 16 cells were resistant. The effects on MOLM-13 cell sur- vival varied for the MDM2 inhibitors with IC values of
NPM1 mutant and wild type, as well as TP53 mutant and wild type cells (Online Supplementary Table S1). Most of the FLT3-ITD AML cells had a high allelic ratio of FLT3-ITD (>0.5). Only few of the patient samples contained addi- tional mutations in driver genes, one with DNMT3A, one with RAS mutations. Samples of AML blast cells were grouped according to the major molecular subtypes (FLT3/TP53/ NPM1) and comprised at least four samples per molecular genetic combination, with median 84% blast cells ranging from 25 to 95% (Online Supplementary Table S1). Both midostaurin and NVP-HDM201 used as single agent treatment induced varying levels of loss in cell viability with correlation to certain AML subsets (Figure 2). Data for MOLM-13 and MV4-11 cell lines were includ-
Figure 3. Synergistic responses in FLT3-ITD AML blast cells to midostaurin and HDM201. Cell viability was determined in individual AML patient cells treated with increasing dosage of NVP-HDM201 as single compound and in combina- tion treatment with midostaurin (PKC412) in FLT3-ITD/TP53wt/NPM1wt relapsed AML (patient 13) (A), FLT3-ITD/TP53wt/NPM1wt primary AML (patient 16) (B) and in FLT3-ITD/TP53wt/NPM1mut primary AML (patient 20) (C). Combination indexes were calculated according to Chou Talalay.42
A
B
C
50
300nM NVP-HDM201, 1 mM RG7388 and 10 mM NVP-
CGM097 (Figure 1D,E,F). MOLM-13 cells were most sus- ceptible to MDM2 inhibitor idasanutlin with IC50 at 1 mM RG7388. MV4-11 and OCI-AML2 cells showed some response to idasanutlin with IC50 of 10 mM RG7388 while OCI-AML3, PL-21, HL-60 and MOLM-16 cells were rather resistant to idasanutlin. With respect to the MDM2 inhibitors NVP-CGM097 and NVP-HDM201 MOLM-13, MV4-11 and OCI-AML2 cells showed consistent suscepti- ble responses while OCI-AML3 and PL-21 cells were less susceptible and MOLM-16 and HL60 cells were resistant. In order to define the most effective treatment combina- tion we focused our studies on the latest and most potent MDM2 inhibitor NVP-HDM201 and tested its effects in single agent treatment and together with the three FLT3- inhibitor compounds in MOLM-13 cells. The combination of NVP-HDM201 and midostaurin had excellent synergis- tic effects on cell survival with a combination index of 0.4, while the combination of NVP-HDM201 with quizartinib or gilteritinib had only moderate synergistic effects with combination indexes of 0.7 and 0.8 (Figure 1H). To deter- mine the relevance of the order of addition, midostaurin and NVP-HDM201 were tested as direct combination or sequential treatment and found to be effective independ- ent of sequence of application. NVP-HDM201 pretreat- ment followed by midostaurin treatment had similar effects on cell viability as midostaurin pretreatment fol- lowed by NVP-HDM201 treatment. Moreover, both sequential treatments had comparable effects on cell via- bility as direct combination treatment (Online Supplementary Figure S1).
Sensitivity of AML patient cells to the MDM2 inhibitor HDM201 and the FLT3 inhibitor midostaurin
To determine the sensitivity of NK-AML blast cells to HDM201 and midostaurin, mononuclear cells isolated from peripheral blood or bone marrow of NK-AML patients were subjected to in vitro cytotoxicity assays. The NK-AML cells covered the major morphologic and molec- ular subtypes including FLT3-ITD and FLT3 wild type,
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ed as, compared to primary FLT3-ITD AML cells with 80% blast cells, FLT3-ITD AML cell lines with 100% blast cells are more susceptible to midostaurin (Figure 2A), and less susceptible to NVP-HDM201 (Figure 2B).
With respect to midostaurin, FLT3-ITD/TP53wt NK- AML cells were distinctly more susceptible than FLT3- ITD/TP53wt cells. Patient derived AML blast cells charac- terized by FLT3-ITD/TP53wt/NPM1wt were susceptible to midostaurin with a median loss of 30% viability after treatment with 500nM PKC412.
FLT3-ITD/TP53wt/NPM1wt cells with 11q23/MLL abnormalities, MOLM-13 (t(9;11) and MV4-11 (t(4;11) lost 60% cell viability within 24 hours when treated with 500nM midostaurin. All other AML cells including
FLT3-ITD/TP53wt/ NPM1mut, FLT3wt and TP53mut cells were less susceptible to midostaurin with 0-10% reduced viability at 500nM midostaurin (Figure 2A).
With respect to NVP-HDM201, we observed that the same NK-AML blast cells characterized by FLT3- ITD/TP53wt/NPM1wt and sensitive to midostaurin were most susceptible to the MDM2 inhibitor NVP-HDM201, with a median loss of 45% viability within 24 hours at 100nM NVP-HDM201. MOLM-13 and MV4-11 cells were less susceptible with a loss of 20% viability at 100nM NVP-HDM201. FLT3-ITD/TP53wt/NPM1wt cells responded with a median 20% loss of viability and FLT3- ITD/TP53wt/NPM1wt with median 10% loss of viability at 100nM NVP-HDM201. All other AML cells including
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Figure 4. Dose-dependent induction of apoptosis and cell death in FLT3-ITD AML cells. Induction of tumor suppressor protein p53 in MV4-11 (A) and MOLM-13 cells (B) treated for 24 hours with the indicated amounts of NVP-HDM201 and midostaurin. Relative quantitation of CDKN1A mRNA (C) and MCL-1 mRNA (D) in AML cells treated for 24 hours with midostaurin (PKC412) (black bars) and NVP-HDM201 (light grey bars) alone or in combination (dark grey bars). Cytometric assays in MV4- 11 AML cells treated with NVP-HDM201 and midostaurin alone and in combination to measure induction of cell death (subG1 fraction) using DAPI staining (E) and induction of apoptosis using AnnexinV/PI staining (F).
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FLT3-ITD/TP53wt/NPM1wt and TP53mut cells were minimally susceptible to NVP-HDM201 with 1-5% reduced viability when treated with 1 mM compound (Figure 2B).
In single agent treatments with 50nM compound, FLT3- ITD/TP53wt/NPM1wt cells were significantly more sus- ceptible to midostaurin and NVP-HDM201 than FLT3- ITD/TP53wt/NPM1mut and FLT3wt cells (Figure 2C,D). FLT3-ITD/TP53wt/NPM1wt cells lost more than 20% cell viability within 24hours at 50nM PKC412 while all other AML cells and normal peripheral blood monocytes were unaffected by this low dose treatment (Figure 2C). Similarly, FLT3-ITD/TP53wt/NPM1wt cells lost 30% cell viability within 24 hours at 50nM NVP-HDM201 while all other AML cells were significantly less affected by this low dose treatment and TP53mut AML cells as well as normal peripheral blood monocytes were unaffected (Figure 2D).
These data propose that the ideal target population for the treatment with midostaurin and NVP-HDM201 are FLT3-ITD NK-AML cells with a high allelic ratio of FLT3- ITD that are wild type for TP53 and NPM1.
Specificity and efficacy of combined HDM201 and midostaurin against FLT3-ITD/TP53wt/NPM1wt AML cells
The response of AML cells to 50nM midostaurin in combination with conventional induction therapy (CI, 20nM cytarabine and 20nM idarubicin) or in combination with 50nM NVP-HDM201 was determined by in vitro cytotoxicity assays. Similar to the single agent treatments reported above, FLT3-ITD/TP53wt NK-AML cells were most susceptible to the combined treatment whereas FLT3-ITD/TP53mut cells turned out to be resistant and FLT3-ITD/TP53wt cells showed intermediate responses (Figure 2E,F).
The combination of midostaurin with conventional induction treatment had significant effects on TP53wt AML cells with 30-40% median loss of cell viability in FLT3-ITD cells and 15-25% reduction in FLT3wt cells exposed to 20nM CI and 50nM midostaurin for 24 hours (Figure 2E). TP53mut AML cells and normal peripheral blood monocytes were affected with 5-10% median loss- es in cell viability. The effects of conventional induction treatment on cell viability were enhanced by the addition of midostaurin in FLT3-ITD/TP53wt cells independent of their NPM1 status (Figure 2E).
The combination of midostaurin with NVP-HDM201 was as effective as the combination of midostaurin with standard induction therapy. As in the single agent treat- ments, FLT3-ITD/TP53wt/NPM1wt cells were most sus- ceptible to this combination with 40% median loss of cell viability in 24 hours to 50nM NVP-HDM201 and 50nM midostaurin (Figure 2F). FLT3-ITD/TP53wt/NPM1mut and FLT3wt/TP53wt/NPM1wt AML cells were less sus- ceptible with a median reduction of 20% cell viability in this combination treatment. FLT3wt/TP53wt/NPM1mut and TP53mut AML cells as well as normal peripheral blood monocytes were least affected with 3% median losses in cell viability. The combination of NVP-HDM201 and midostaurin had synergistic effects on cell survival of FLT3-ITD positive AML cells with a combination index of 0.63 in the relapsed AML patient #13 (Figure 3A), and moderate synergistic effects in FLT3-ITD positive primary AML cells (Figure 3B,C). FLT3-ITD/TP53wt/NPM1wt pri-
mary AML cells (patient #16) were most susceptible to this combination treatment (Figure 3B) with reduced responses in FLT3-ITD/TP53wt/NPM1wt (patient#20) pri- mary AML (Figure 3C).
To confirm p53 activation in the presence of MDM2 inhibitors we determined the expression levels of the tumor suppressor protein p53 and of the p53 target genes CDKN1A and MCL1 in AML cells treated for 24 hours with single compounds and with combined treatment. Protein p53 was stabilized and p53 levels were increased in AML cells treated with 200nM NVP-HDM201, with three- to eightfold induction in MV4-11, MOLM-13 and OCI-AML3 cells, while OCI-AML2 cells had a high p53 level with a maximal 20% increase (Figure 4 A, B, C, D). CDKN1A gene expression was significantly induced in FLT3-ITD/TP53wt/NPM1wt AML cells (MOLM-13, MV4-11, patient#13) and in FLT3wt/TP53wt/NPM1wt cells (OCI-AML2) treated with 50nM NVP-HDM201 (Figure 4E), and in FLT3wt/TP53wt/NPM1mut cells (OCI- AML3) treated with 500nM NVP-HDM201, but not in FLT3wt/TP53mut cells (MOLM-16). To reach the same level of p53 target gene expression induced by 50nM NVP- HDM201 in FLT3-ITD/NPM1wt (MOLM-13, MV4-11, pat#13) and FLT3wt/NPM1wt (OCI-AML2) cells, ten times more MDM2 inhibitor was required in FLT3wt/NPM1mut (OCI-AML3) cells. Yoshimoto et al. 2009 showed that FLT3-ITD up-regulates the apoptosis inhibitor MCL-1 to promote survival of stem cells in acute myeloid leukemia. They analyzed the function of MCL-1 in FLT3-ITD AML and showed that the enforced expres- sion of MCL-1 prevented MV4-11 cells from apoptosis in the presence of 100nM midostaurin. Inhibition of MCL-1 by shRNA resulted in apoptosis of MV4-11 cells. To eluci- date the mechanism of apoptosis induction by NVP- HDM201 and midostaurin we analyzed MCL-1 expres- sion in a variety of AML cells (Figure 4F). MCL-1 gene expression was repressed in the presence of 50nM NVP-HDM201 or 50nM midostaurin in FLT3-ITD/TP53wt/NPM1wt AML cells (MOLM-13, MV4-11, patient#13), with enhanced effects in the combi- nation treatments. MCL-1 gene expression was repressed in the presence of 50nM NVP-HDM201 in FLT3wt/TP53wt/NPM1wt cells (OCI-AML2) and by 500nM NVP-HDM201 in FLT3wt/TP53wt/NPM1mut cells (OCI-AML3), but not by midostaurin. There was no repression of MCL-1 gene expression in FLT3wt/TP53mut cells (MOLM-16). In the susceptible FLT3-ITD cell lines MV4-11 and MOLM-13 as well as in the relapsed FLT3- ITD AML sample (patient#13) both compounds led to a significant reduction in MCL-1 gene expression with enhanced reduction in the combination treatments (Figure 4F). The effect of NVP-HDM201 and midostaurin treat- ment on MCL-1 gene repression appeared to be strongly synergistic with a combination index of 0.25. To further assess pro-apoptotic effects in AML cells treated with midostaurin and with the MDM2 inhibitor NVP- HDM201, cells were stained with AnnexinV and DAPI and analyzed on a cell imager. Apoptosis and cell death were induced in FLT3-ITD/TP53wt/NPM1wt cells in a dose dependent manner by both inhibitors in single com- pound and combination treatments. There was a signifi- cant increase in dead cells with subG1 DNA content, and a concomitant loss of cells in defined cell cycle stages, most prominently a reduction of cells with G0/G1 phase DNA content, but also of cells with S-phase and G2 phase
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content in MV4-11 cells treated with 20nM PKC412 and 50nM NVP-HDM201 (Figure 4G). Moreover, there was a significant increase in the number of AnnexinV positive apoptotic cells and a concomitant reduction in AnnexinV negative non-apoptotic cells in MV4-11 cells treated with 20nM PKC412 and 50nM NVP-HDM201 (Figure 4H). The pro-apoptotic and lethal effects of the single compound treatments were enhanced in the combined treatments with a combination index of 0.44 indicating synergistic pro-apoptotic and lethal effects with NVP-HDM201 and midostaurin. A similar induction of apoptosis and cell death was also detected in MOLM-13 cells treated with 20nM PKC412 and 50nM NVP-HDM201 (Online Supplementary Figure S2). While there was no pro-apoptot- ic effect in FLT3wt/TP53wt/NPM1mut (OCI-AML3) and FLT3-ITD/TP53mut (PL-21) cells at 100nM compounds, a low-level induction of apoptosis and cell death was detected in OCI-AML3 and PL-21 cells after 24 hours of treatment with 1 mM compounds (data not shown).
In summary, our data indicate that NVP-HDM201 and midostaurin can induce apoptosis and cell death effective- ly and specifically in FLT3-ITD/TP53wt/NPM1wt AML cells. FLT3-ITD is a constitutively active growth factor
receptor signaling via PI3K-AKT,13 via RAS-MEK-ERK13 and via STAT514,15 leading to cell growth and proliferation via p53 inhibition and MCL1 induction (Figure 5). We have shown that MDM2 inhibition by NVP-HDM201 can reactivate p53 function leading to induction of CDKN1A and inhibition of MCL1 gene expression. Inhibition of FLT3-ITD by midostaurin, however, did not restore p53 function, but led to reduced MCL1 gene expression via RAS-MEK-ERK and/or STAT5 signaling (Figure 5). These data suggest that the combined use of NVP-HDM201 and midostaurin might be a promising treatment option par- ticularly in FLT3-ITD AML relapsed or refractory to con- ventionaltherapy.
Discussion
Acute myeloid leukemia (AML) characterized by nor- mal karyotype (NK) and presence of the mutated FLT3 growth factor receptor gene variant FLT3-ITD comprises 27-34% of newly diagnosed AML. The subset of NK-AML patients with high allelic ratio of FLT3-ITD (>0.5) and NPM1 wild type is associated with adverse risk and low-
Figure 5. Schematic representation of the FLT3-ITD signaling pathways and downstream effects. FLT3-ITD is a constitutively active growth factor receptor signaling via PI3K-AKT, via RAS-MEK- ERK and via STAT5 leading to cell growth and proliferation via p53 inhibition and MCL1 induction. p53 function can be reactivated by NVP-HDM201 treatment leading to induction of CDKN1A and inhi- bition of MCL1 gene expression. MCL1 gene expression can be inhibited by NVP-HDM201 via p53 induction and by midostaurin (PKC412) via RAS-MEK-ERK and/or STAT5 signaling.
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est survival rates. Survival rates are higher in NK-AML patients with high allelic ratio of FLT3-ITD and NPM1mut or low allelic ratio of FLT3-ITD and NPM1 wild type or FLT3wt and NPM1mut which have all been classified as intermediate risk.16 The leukemic cells of all these AML subsets have substantially elevated levels of cellular p53 antagonists and reduced p53 activity17 which identifies them as targets for treatments aiming to restore p53 func- tion including conventional chemotherapy with genotoxic compounds and non-genotoxic treatments with p53 reac- tivating compounds.
MDM2 is an established cellular p53 antagonist fre- quently overexpressed in AML cells. A variety of MDM2 inhibitors have been developed and tested in AML cell lines. Compounds currently in clinical trials for the treat- ment of AML include idasanutlin (RG7388), NVP- CGM097 and NVP-HDM201.12,18,19 We have studied the MDM2 inhibitor idasanutlin in combination with the MEK inhibitor cobimetinib in AML cell lines and patient samples and found this combination to be effective only in AML cells expressing high levels of FLT3 and MDM2 protein.20 The activity of NVP-CGM097 was investigated in AML cell lines and primary AML cells expressing wild type and mutant p53, alone and in combination with the FLT3 inhibitor PKC412 (midostaurin) or the MEK inhibitor AZD 6244.19 Synergy was observed when NVP- CGM097 was combined with FLT3 inhibition against oncogenic FLT3 expressing cells, as well as when com- bined with MEK inhibition in cells with activated MAPK signalling. In addition to reactivating p53 in AML cells by specific MDM2 inhibition the FLT3 receptor can be directly targeted by (more or less) specific tyrosine kinase inhibitors.5,21
In the present study, we tested a variety of FLT3 and MDM2 inhibitors. The effects on cell survival of FLT3- ITD AML cells were consistent for the FLT3 inhibitors midostaurin (PKC412), quizartinib (ACC220) and gilteri- tinib (ASP2215), but varied for the MDM2 inhibitors idasanutlin (RG7388), NVP-CGM097 and NVP-HDM201. The most potent MDM2 inhibitor NVP-HDM201 exhibit- ed superior combinatory effects on cell viability of FLT3- ITD AML cells together with midostaurin, and moderate combinatory effects together with quizartinib and gilteri- tinib. The different combinatory potentials may be related to the target specificity of the three FLT3 inhibitors. While quizartinib (ACC220) inhibits FLT3 and PDGFR kinases,22 gilteritinib (ASP2215) inhibits FLT3, LTK, ALK, and AXL kinases,8 and midostaurin (PKC412) inhibits FLT3, KIT, PKC, PPK, VEGFR-2, PDGFR, and SYK kinases.23 PDGFR and VEGFR-2 are expressed in the bone marrow of AML patients24,25 and, like FLT3, signal via PI3K/AKT and MDM2 to inhibit p53.26,27 The stem cell growth factor receptor KIT is expressed in the bone marrow and, like FLT3-ITD, signals via PI3K/AKT and MDM2 to inhibit p53, and via JAK2 and STAT5.28
MOLM-13 and MV4-11 AML cells were most suscepti- ble to the FLT3 inhibitor midostaurin. Both cell lines have a high allelic ratio of FLT3-ITD and harbor MLL rearrange- ments, created by t(9;11) and t(4;11), encoding MLL-AF9 and MLL-ENL, respectively. FLT3 and MLL cooperate in AML29 and leukemic cells with mutations in FLT3 and MLL are known to be susceptible to midostaurin.30,31 In the absence of MLL mutations, FLT3-ITD AML cells were less susceptible to midostaurin, but more susceptible to NVP- HDM201 indicating that the presence of MLL fusion pro-
teins may change the susceptibility of AML cells to FLT3 and MDM2 inhibitors.
NK-AML cells with FLT3-ITD/TP53wt/NPM1wt were particularly susceptible to the combination of midostaurin with conventional induction therapy or with NVP- HDM201. In contrast, NK-AML cells with mutated TP53 were rather resistant to midostaurin and NVP-HDM201, and they have previously been shown to be resistant to chemotherapy with genotoxic compounds32 and to other MDM2 inhibitors.33 As both the conventional induction therapy and MDM2 inhibition induce cell cycle exit and apoptosis via p53 activation, these treatments can only be effective in a TP53 wild type context.9 The presence of one mutated TP53 allele may be sufficient to suppress the function of the remaining p53 wild type protein. Hence, restoring wild-type p53 activity may be a promising option for treatment of AML with mutated TP53.34 HL-60 cells with deleted TP53 were resistant to midostaurin and HDM201, indicating that these two compounds specifi- cally target AML cells with functional p53 protein. This is in apparent contrast to the FLT3- inhibitor sorafenib and the MDM2 inhibitor nutlin-3 which promoted synergistic cytotoxicity irrespectively of FLT3 and p53 status via induction of the pro-apoptotic Bcl-2 family members Bax and Bak in p53 wild type and p53 deleted cells.35
It seems remarkable that FLT3wt/TP53wt/NPM1mut AML cells turned out to be as refractory to midostaurin and NVP-HDM201 as TP53mut cells. This suggests that the presence of mutated NPM1 protein is sufficient to pre- vent induction of p53 target genes by midostaurin or NPV- HDM201 in these cells. The mutated NPM1 protein (NPM1c) reduces the susceptibility of FLT3-ITD AML cells to both midostaurin and NVP-HDM201, indicating that the same molecular mechanisms may be involved in FLT3wt and FLT3-ITD cells. NPM1c is exported to the cytoplasm36 where it inhibits the tumor suppressor protein p53 by cytoplasmic retention. This leads to reduction of p53 protein in the nucleus and decreases its stability and transcriptional activation function.37 It appears that this loss of p53 activity by NPM1c cannot be compensated by inhibition of MDM2 or FLT3, at least not with NVP- HDM201 or midostaurin. In contrast, nutlin-3 can induce apoptosis and cell death in FLT3wt/TP53wt/NPM1mut cells,17 indicating a fundamental difference in the activities of the two MDM2 inhibitors.
The molecular mechanisms involved in p53 activation appear to be different in the conventional induction treat- ment. Here, FLT3wt/TP53wt/NPM1mut AML cells were more susceptible to conventional induction treatment than TP53mut cells, indicating that the presence of NPM1c is not sufficient to prevent p53 activation by geno- toxic substances. This may be reflected by the usually favorable outcome of FLT3wt/TP53wt/NPM1mut AML patients after standard induction treatment.38,39 Midostaurin can enhance effects of conventional induc- tion therapy in FLT3-ITD cells in vitro and in vivo. As eval- uated in a randomized, double-blind, phase III interna- tional study (clinicaltrials.gov identifier 00651261) in high- risk patients with newly diagnosed, FLT3-mutant AML (CALGB10603/RATIFY trial), the multikinase inhibitor midostaurin plus standard chemotherapy improved sur- vival compared with placebo plus chemotherapy.40,41 On April 28, 2017, the U.S. Food and Drug Administration approved midostaurin (RYDAPT, Novartis Pharmaceuticals Corp.) for the treatment of adult patients
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with newly diagnosed acute myeloid leukemia (AML) who are FLT3 mutation-positive (FLT3+), in combination with standard cytarabine and daunorubicin induction and cytarabine consolidation. This combination therapy is, however, not suitable for NK AML patients with FLT3-ITD in relapse or refractory to conventional induc- tion treatment or unfit for intensive treatment. For the subset of AML patients with a high ratio of FLT3-ITD and adverse prognosis, the combined use of non-genotoxic tar- geted compounds, such as the combination of midostau- rin and NVP-HDM201, may represent a promising treat- ment option. Synergistic effects on cell viability with midostaurin and NVP-HDM201 were observed independ- ent of sequence of application, indicating that the order of target inhibition for FLT3 and MDM2 was not important. Sequential application of NVP-HDM201 and midostaurin
had the same effects on cell viability as direct combination treatment. Pretreatment with one inhibitor did not enhance the susceptibility of AML cells to the second inhibitor. This leaves several options for treatment regi- mens in a prospective clinical trial. The best therapy regi- men in combination treatments with midostaurin and NVP-HDM201 for AML patients will have to be defined empirically.
Acknowledgments
We thank Novartis for providing the investigational com- pounds NVP-HDM201 and NVP-CGM097.
Funding
This work was supported by a grant from the Swiss National Science Foundation (SNF) #310030_127509 to TP.
References
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]]></page><page Index="133" isMAC="true"><![CDATA[Acute Lymphoblastic Leukemia
Radiation exposure from computerized tomography and risk of childhood leukemia: Finnish register-based case-control study of childhood leukemia (FRECCLE)
Atte Nikkilä,1 Jani Raitanen,2,3 Olli Lohi1,4 and Anssi Auvinen2,3,5
1Faculty of Medicine and Biosciences, University of Tampere; 2Faculty of Social Sciences, University of Tampere; 3UKK Institute for Health Promotion Research, Tampere; 4Tampere Center for Child Health Research, University of Tampere and Tampere University Hospital and 5STUK – Radiation and Nuclear Safety Authority, Helsinki, Finland
ABSTRACT
The only well-established risk factors for childhood leukemia are high-dose ionizing radiation and Down syndrome. Computerized tomography is a common source of low-dose radiation. In this study, we examined the magnitude of the risk of childhood leukemia after pediatric computed tomography examina- tions. We evaluated the association of computed tomography scans with risk of childhood leukemia in a nationwide register-based case- control study. Cases (n=1,093) were identified from the population- based Finnish Cancer Registry and three controls, matched by gender and age, were randomly selected for each case from the Population Registry. Information was also obtained on birth weight, maternal smoking, parental socioeconomic status and background gamma radi- ation. Data on computed tomography scans were collected from the ten largest hospitals in Finland, covering approximately 87% of all pediatric computed tomography scans. Red bone marrow doses were estimated with NCICT dose calculation software. The data were ana- lyzed using exact conditional logistic regression analysis. A total of 15 cases (1.4%) and ten controls (0.3%) had undergone one or more com- puted tomography scans, excluding a 2-year latency period. For one or more computed tomography scans, we observed an odds ratio of 2.82 (95% confidence interval: 1.05 – 7.56). Cumulative red bone marrow dose from computed tomography scans showed an excess odds ratio of 0.13 (95% confidence interval: 0.02 – 0.26) per mGy. Our results are consistent with the notion that even low doses of ionizing radiation observably increase the risk of childhood leukemia. However, the observed risk estimates are somewhat higher than those in earlier studies, probably due to random error, although unknown predispos- ing factors cannot be ruled out.
Introduction
Leukemia is the most common childhood malignancy.1 The incidence rates of childhood leukemia in Finland are comparable to those in other European coun- tries and show a slight increasing trend up to the 1990s.2 Acute lymphoblastic leukemia accounts for approximately 85% of all childhood leukemias. The major histological subtype of acute lymphoblastic leukemia is precursor B-cell acute lym- phoblastic leukemia (~85%).1
Well-established risk factors for childhood leukemia include high doses of ion- izing radiation, alkylating chemotherapy agents, as well as Down syndrome and some rare congenital syndromes such as Fanconi anemia, Bloom syndrome and ataxia telangiectasia.1,3-6 A number of genetic variants have also been associated
Ferrata Storti Foundation
Haematologica 2018 Volume 103(11):1873-1880
Correspondence:
atte.nikkila@uta.fi
Received: January 6 2018. Accepted: June 26, 2018. Pre-published: July 5, 2018.
doi:10.3324/haematol.2018.187716
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1873
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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with increased risk of leukemia.7,8 Furthermore, there is reasonably consistent evidence of a slightly increased risk associated with large birth weight relative to gestational time.9 A higher risk has also been suggested for older parental age, delivery by Cesarean section, and paternal smoking.10–13 However, daycare attendance, allergic dis- eases, maternal folic acid supplementation before birth, and early immune stimulation have been suggested to reduce the risk of leukemia.14–17
Although high doses of ionizing radiation increase the risk of childhood leukemia, the magnitude of any effect from low doses remains uncertain. Some studies have suggested increased risks associated with background radiation and following x-ray examinations in utero and post-natally.18–22 Computed tomography (CT) imaging has been used for almost four decades and its frequency of utilization increased greatly during the 1980s-1990s. The annual number of scans peaked around year 2002; more recently CT scans have been partly replaced by magnetic resonance imaging in pediatric imaging, partly because of the risk of cancer from ionizing radiation.23 In 2015, 5,311 pediatric CT scans were performed in the Finnish popu- lation of 1,024,000 children under 17 years old, which is a low rate compared to that in many other countries.23,24
Four high-quality studies have investigated the associa- tion of pediatric CT scans and childhood leukemia.25–28 The interpretation of the findings must include an evalu- ation of confounding by indication, i.e. underlying condi- tions predisposing children to both CT scans and leukemia.28–30 Nevertheless, the evidence is still limited and the magnitude of the risk needs to be characterized further.
In this study, we examined the magnitude of the risk of childhood leukemia after pediatric CT examinations using a nationwide case-control design with efforts to avoid reverse causation.
Methods
We used a register-based, case-control study with individually matched controls. The key characteristics of the material have been presented previously.10 Briefly, all cases of childhood leukemia (M9800–M9948 in ICD-O-3) diagnosed in Finland dur- ing 1990–2011 (n=1,100) before the age of 15 years were identi- fied from the Finnish Cancer Registry (Figure 1). Three controls were individually matched, by sex and year of birth, for each case from the Population Register Center. In all analyses, a 2-
Figure 1. Flow chart depicting the selection of study subjects. The flow of cases is represented on a white background and the controls on a light gray background. The necessary exclusions are shown in red boxes. Dashed lines represent the linking of the study subjects with the CT scans collected.
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year latency period was used, in part to deal with reverse causa- tion due to confounding by indication.31 Also, multiple predis- posing factors (Online Supplementary Table S1) were accounted for with outpatient register data. The methods are described in more detail in the Online Supplementary Material.
We obtained data on all CT scans performed on pediatric patients (<15 years) from all five university hospitals and the five
largest central hospitals in Finland (Table 1, Figure 2). The period of data availability varied between hospitals, because radiologi- cal databases with information on each CT scan for individual patients were introduced at different times. We estimated that the data from the study hospitals covered 87% of all pediatric CT scans performed in Finland during 1975–2011 (see the Online Supplementary Material for details). For each CT scan, we
Table 1. The collection and availability of electronically stored computed tomography scans.
Hospital
Helsinki University Hospital
Tampere University Hospital Oulu University Hospital
Turku University Hospital
Kuopio University Hospital Central Finland Central Hospital Satakunta Central Hospital Seinäjoki Central Hospital Päijänne Tavastia Central Hospital North Karelia Central Hospital TOTAL
City
Helsinki
Tampere Oulu Turku Kuopio Jyväskylä Pori Seinäjoki Lahti Joensuu
Data availability
1990–2011
1978–2011 1993–2011 1996–2011 1996–2011 2002–2011 1995–2011 1999–2011 2000–2011 1993–2011
Number of CT scans
31,825
9,236 7,513 7,360 5,408 2,571 1,948 1,759 1,597 1,191 80,783
All Finnish university hospitals are listed first followed by the five chosen central hospitals.
Figure 2. Flow chart linking the collected computed tomography scans to the study subjects The flow of the CT scans is represented on a white back- ground and the CT scans to different body parts on a light gray background. The necessary exclusions are shown in red boxes.
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obtained the parameters used for dose assessment including year, body part, use of contrast medium and the number of sequences. Manufacturers and models of CT scanners in each hospital were acquired from the Radiation and Nuclear Safety Authority (STUK). For dose calculations, we assumed in the main analysis that each CT scan was performed using the latest CT scanner available at the hospital.
Data on a total of 80,783 pediatric CT scans were obtained and of those, 49 CT scans were performed on the study subjects, excluding the 2-year latency period (Table 1). Half (n=25) were head scans, and 19 were lung scans. Of the CT scans, 36 were per- formed on 15 (1.4%) cases and 13 scans on 10 (0.3%) controls.
The CT scan parameters were obtained based on expert opin- ion of an experienced hospital physicist (Online Supplementary Table S2). The doses were estimated using the NCICT software (v1.2).32 Age- and sex-specific pediatric software phantoms (for neonates, and children aged 1, 5, 10, and 15 years) were used. The input for dose calculation also included the scanner manu- facturer and model. If data were available only on the manufac- turer, a manufacturer-specific average was used. It was assumed that a head or body filter was used, based on the target body part. The cumulative absorbed red bone marrow (RBM) doses were obtained as the sums of absorbed RBM doses from all CT scans for each study subject. The dose from a scan was multi- plied by 1.5 if contrast medium was used, consistent with tissue- specific coefficients suggested for other tissues.33 Alternative dose estimates were obtained based on values reported in the lit- erature.34
We identified subjects with Down syndrome (40 cases and 2 controls) from the Congenital Malformation Register and Care Register for Health Care, and those with a previous malignancy (2 cases) from the Finnish Cancer Registry. They were excluded to avoid confounding by indication (reverse causation). We also collected information on birth weight (large for gestational age) and maternal smoking during pregnancy from the Medical Birth Register, as well as socioeconomic status and education of the parents from Statistics Finland. Residential exposure to back- ground gamma radiation, including natural terrestrial radiation and Chernobyl fallout, was estimated as described previously.8
Due to small frequencies, exact conditional logistic regression in SAS 9.4 was used for estimating odds ratios (OR), excess odds ratios and their confidence intervals (CI).35 Statistical power cal- culations indicated that the sample size is sufficient for detecting a linear dose-response with an OR of 1.05 or greater per 1 mGy increase in cumulative RBM dose with a statistical power of 80% using asymptotic conditional logistic regression.36
The ethical committee of Pirkanmaa Hospital district reviewed the study protocol (tracking number R14074) and, in accordance with Finnish regulations, no informed consent was required for this register-based study. In addition, each hospital approved our study protocol before delivering the data on CT scans. We obtained permission to use data from the Finnish Cancer Registry, the Medical Birth Register, Care Register for Health Care and Congenital Malformation Register from the National Institute of Health and Welfare (1774/5.05.00/2014), as well as census data on socioeconomic status from Statistics Finland (TK-52-306-16).
Results
In our nationwide register-based study, after excluding cases with an incorrect personal identification number or prohibition to use their data, we identified 1,093 cases of childhood leukemia diagnosed in 1990-2011. Most of the
cases were acute lymphoblastic leukemia (81.1%) or acute myeloid leukemia (13.0%). The median age at diag- nosis among cases was 4.52 years (interquartile range, IQR 2.72 – 8.23). Of the cases and controls, 52% were male (Table 2). The criteria for large for gestational age were met by 121 (13.3%) of the cases and 275 (9.9%) of the controls.
Table 2. The characteristics of cases and controls before any exclusions.
Gender Female Male
Large for gestational age No
Ys
Missing
Mother’s smoked during pregnancy
No
Yes Missing
Down syndrome No
Yes
Parents’ education Mother
Upper secondary Bachelor’s degree
Master’s or doctor’s degree Missing
Father
Upper secondary Bachelor’s degree
Master’s or doctor’s degree Missing
Parents’ socioeconomic status Mother
Self-employed
Upper level employee Lower level employee Manual worker
Other
Missing
Father
Self-employed
Upper level employee Lower level employee Manual worker
Other
Missing
Age at leukemia diagnosis, years 0–2
2–7
7–15
Leukemia type Pre-B-ALL
Pre-T-ALL
Unclassified ALL
Acute myeloid leukemia Other
48.0% (525) 52.0% (568)
86.7% (788) 13.3% (121) 184
83.1% (742) 16.9% (151) 200
96.3% (1053)
3.7% (40)
48.5% (530) 22.3% (244) 10.2% (112) 18.9% (207)
52.0% (568) 15.2% (166) 10.0% (110) 22.8% (249)
7.7% (84) 16.1% (176) 34.8% (380) 21.4% (231) 18.2% (199) 2.1% (23)
13.9% (152) 17.6% (192) 18.3% (197) 34.0% (372) 12.4% (135) 4.1% (45)
14.3% (156) 55.5% (605) 33.4% (332)
75.6% (826) 5.9% (64) 1.8% (20) 13.6% (149) 3.1% (34)
48.0% (1575) 52.0% (1704)
90.1% (2493) 9.9% (275) 511
84.5% (2296) 15.5% (420) 563
99.9% (3277)
0.1% (2)
50.6% (1659) 23.1% (756) 9.8% (321) 16.6% (543)
51.4% (1685) 16.2% (532) 10.2% (334) 22.2% (728)
8.3% (273) 15.7% (514) 34.5% (1130) 20.6% (674) 20.3% (664) 0.7% (24)
12.0% (395) 18.2% (596) 17.9% (587) 35.0% (1148) 14.3% (469) 2.6% (84)
Cases(n=1,093) Controls(n=3,279)
P
0.001
0.096
<0.001
ref 0.869 0.406
ref 0.423 0.880
ref 0.477 0.521 0.490 0.859
ref 0.178 0.273 0.170 0.036
The reported P-values are from an univariate conditional logistic regression model.The non- binary variables were treated as factors and the reference categories are marked with“ref”.ALL: acute lymphoblastic leukemia.
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After exclusions, eight cases (0.7%) and nine controls (0.3%) had undergone at least one CT scan. The median RBM dose was 10.1 mGy (IQR 4.79 – 13.6) for the exposed cases and 6.29 mGy (IQR 5.69 – 7.14) for the exposed controls (Figure 3). The corresponding literature- based values were 26.5 mGy and 17.6 mGy. The RBM doses calculated with NCICT from thoracic CT scans var- ied between 1.8 and 6.8 mGy (median 4.0 mGy) and sim- ilarly, the doses for head CT scans varied between 1.6 and 10.7 mGy (median 6.6 mGy).
The OR for any versus no CT was 2.82 (95% CI: 1.05 – 7.56). For two or more pediatric CT scans, the OR was 5.22 (95% CI: 0.89 – 69.9). For any head CT scans, an OR of 4.00 (95% CI: 1.39 – 11.5) was obtained.
The overall excess OR of childhood leukemia was 0.13 (95% CI: 0.02 – 0.26) per mGy of absorbed RBM dose cal- culated with the NCICT software (Table 3). Using the cumulative RBM dose estimates from the literature, an excess OR of 0.05 (95% CI: 0.01 – 0.10) per mGy was obtained. In an analysis by dose tertile calculated with
A
B
Figure 3. Histograms of (A) the ages of the subjects at the time of computed tomography scan and (B) the cumulative doses received by the subjects, calcu- lated with NCICT.
NCICT, the excess OR relative to zero dose were 1.26 (95% CI: -0.50 – 10.1) for the first group, 0.09 (95% CI: -0.89 – 10.5) for the second, and 5.00 (95% CI: 0.10 – 31.7) for the last (Figure 4).
For the most common subtype, precursor B-cell acute lymphoblastic leukemia, the excess OR per mGy was 0.14 (95% CI: 0.02 – 0.29) using estimates from NCICT and 0.06 (0.01 – 0.11) for literature-based estimates. The excess OR for any versus no CT scans was 2.25 (95% CI: 0.08 – 8.75) for acute lymphoblastic leukemia and 2.88 (95% CI: 0.22 – 11.4) for precursor B-cell acute lym- phoblastic leukemia. In the analysis by age at diagnosis/reference date, the excess OR for any versus no CT scans was 3.50 (95% CI: -0.25 – 25.9) for children aged 2 – <7 years and 1.27 (95% CI: -0.32 – 6.54) for those aged 7 – <15 years.
Covariate (confounder) adjustments (large for gesta- tional age, maternal smoking during pregnancy, parental education and parental socioeconomic status) did not alter the OR for CT exposure by more than 0.05 units, with the exception of maternal smoking, which increased the OR related to the number of pediatric CT scans (0 ver- sus 1 or more) (approximately 0.10 units). Nevertheless, we preferred the unadjusted model, as missing data on maternal smoking resulted in wider confidence intervals for the main variables.
The OR were higher when the subjects with Down syndrome were not excluded (for 1 or more CT scans OR=5.21, 95% CI: 2.19 – 12.4 and for cumulative RBM dose excess OR=0.19 per mGy, 95% CI: 0.07 – 0.32). No evidence of a different effect of the RBM doses on leukemia risk for subjects with or without Down syn-
Table 3. The frequencies of computed tomography scans for subjects >2 years old at the reference date and odds ratios calculated with exact condi- tional logistic regression.
Cases Controls
911 2730
CT scans
0 903 2721 1 4 7 2 or more 4 2
by type (1 or more)
ALL 7 7 pre-B-ALL 7 6
by age-group (1 or more)
2-<7years 3 2 7 - <15 years 5 7
by dose index (NCICT/literature)
low, 4.79a/11.6b mGy 3 4 medium, 6.72a/19. 8b mGy 1 3 high, 13.8a/33.2b mGy 4 2
per 1 mGy (NCICT)
TOTAL pre-B-ALL
per 1 mGy (literature)
TOTAL
pre-B-ALL
OR (95% CI)
1.85 (0.39, 7.36) 6.22 (0.89, 68.9)
3.25 (1.08, 9.75) 3.88 (1.22, 12.4)
4.50 (0.75, 26.9) 2.27 (0.68, 7.54)
2.26 (0.50, 10.1) 1.09 (0.11, 10.5) 6.00 (1.10, 32.8)
1.13 (1.02, 1.26) 1.14 (1.02, 1.29)
1.05 (1.01, 1.10)
1.06 (1.01, 1.11)
The reference group for all calculated odds ratio (OR) is zero CT scans for categorical vari- ables. Study subjects with Down syndrome or cancer diagnoses were excluded. All reported OR are from an unadjusted model.The median doses for dose-index classes calculated with NCICT are marked with a.The respective class medians based on literature are marked with b. ALL: acute lymphoblastic leukemia; pre-B-ALL: precursor B-cell acute lymphoblastic leukemia.
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drome was found to suggest effect modification (interac- tion P=0.99).
When the oldest possible CT scanner (at maximum, 10 years old) at the hospital was used in dose estimation instead of the most modern CT scanner, the median cumulative RBM dose for cases was 9.71 mGy (IQR 7.09 – 18.7) and for controls 7.14 mGy (IQR 5.71 – 12.6), with an excess OR of 0.11 (95% CI: 0.02 – 0.22) per mGy.
When the cumulative RBM dose from terrestrial gamma radiation and Chernobyl fallout was included in the model, the OR for cumulative RBM dose from pedi- atric CT scans remained unchanged. The median cumula- tive dose from residential gamma radiation was 1.96 mSv for cases and 1.90 mSv for controls.
The distributions of cities of the last addresses of cases and controls were analyzed to evaluate whether cases and controls belonged to catchment populations of differ- ent hospitals, which might have caused differential mis- classification due to contrasting data availability. No dif- ference in the distributions was noted (chi-squared test, P=0.30). The age and CT scan years of the subjects are reported in Online Supplementary Table S3.
Discussion
We estimated the impact of radiation exposure from pediatric CT scans on risk of childhood leukemia in a nationwide register-based case-control study in Finland. Overall, a statistically significant increase in risk per mGy of RBM absorbed dose was found. The central estimate is larger than in previous studies, but the confidence inter- vals overlap with earlier results, and the effect size is compatible with extrapolation from high-dose studies. The higher main point estimate is likely influenced by random error, as the dose estimates were imprecise due to lack of detail in dosimetric data, including parameter values used for the scanner. It is also possible that the typ- ical values based on expert opinion are representative of current procedures, but may underestimate doses from older examinations, which could inflate the risk estimates per unit dose. However, our site-specific dose estimates calculated with NCICT were quite comparable with those reported in the British study.25 We minimized the potential for systematic error by adjusting for several con- founders and used consistent procedures for the cases and controls. The risk estimates were slightly higher for pre- cursor B-cell acute lymphoblastic leukemia than for other leukemias, but the difference was not statistically signifi- cant.
Two large studies have been published on the subject prior to ours. The cohort studies from the United Kingdom and Australia reported a significant risk of child- hood leukemia associated with RBM dose from pediatric CT scans.25,26 Pearce et al. found an excess relative risk of 0.04 per mGy and Mathews et al. reported a relative risk of 1.2 for one or more CT scans with an excess relative risk of 0.04 per mGy. The Australian cohort had 211 exposed leukemia cases and the UK study 74. A smaller German cohort study reported an increased leukemia incidence following two or more CT scans, but a non-sig-
27 nificant dose-response based on 12 exposed cases. Based
on the Life Span Study in Japan, the extrapolated excess relative risk for childhood exposure would be approxi- mately 0.05 per mGy.37
Other major sources of ionizing radiation were taken into consideration by including cumulative RBM doses from terrestrial gamma radiation and Chernobyl fallout, and this did not affect the results. In our data, the average cumulative RBM dose from CT for the controls was only 0.002 mGy, which is approximately 0.1% of the average annual RBM dose in Finland.38 We accounted for medical use of radiation, to which tomography scans make the largest contribution, and terrestrial gamma radiation, which accounts for nearly two-thirds of average annual radiation to the RBM in Finland.23,39 In addition, there is little evidence to assume that other sources of ionizing radiation, such as cosmic radiation or internal exposure to natural radioisotopes, would distribute unequally among the cases and controls.
The coefficient 1.5 for incremental dose due to CT imaging with contrast medium was chosen pragmatically based on the coefficients for other body parts, as the effects on RBM dose were not reported separately.33
Based on limited population statistics available from the Radiation and Nuclear Safety Authority,23 roughly 30 CT scans were expected for the controls. However, only 13 scans were recorded among them. This might partly reflect incomplete availability of data, but the estimate of the expected numbers is highly uncertain because of lack of data on pediatric CT scans prior to 2008. It is also worth noting that pediatric CT scans are performed less frequently in Finland than in several other countries.24
Our material consists of a comprehensive set of child- hood leukemia cases and representative controls, which should eliminate selection bias by virtue of a register- based approach, which required no consent or informa- tion from the study subjects or their families. The study period covers the years in which the use of pediatric CT scans was most frequent, as the annual number of pedi- atric CT scans has been decreasing in Finland since the year 2000.23 The data on CT scans were obtained from
Figure 4. Dose-response curve of cumulative red bone marrow dose from pedi- atric computed tomography scans and childhood leukemia. The point esti- mates with 95% confidence intervals are for the three dose index levels and the fitted curve is for the cumulative RBM dose calculated with NCICT. The shaded area represents the 95% confidence interval for the continuous dose-response. The vertical axis is on a binary logarithm scale.
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hospital databases to avoid recall bias, and also included the scanner model and use of contrast medium. As in other studies, the most common single CT scan in our analysis was a head scan.23
Radiation doses to RBM from the CT scans were calcu- lated using the best available methods, employing NCICT software, with age- and sex-specific phantoms and taking into account the scanner model. The scanning parameters entered into the software were based on the settings and procedures commonly used in Finland, although data were not available for each scan. We also evaluated the effects of choosing the most modern CT scanner at each imaging site and the OR showed robust behavior.
We also had data on several important risk factors includ- ing Down syndrome, parental socioeconomic status, large for gestational age and maternal smoking. We were able to incorporate data on cancer predisposing factors, which have been shown to be of importance recently.28,30 Inclusion of cases with Down syndrome would have increased the risk estimates, possibly because Down syndrome is associ- ated with increased risks of both leukemia and infections.4,40 We also explored the joint effect of Down syndrome and cumulative RBM dose and found no interaction. Subgroup analyses of exploratory nature were carried out by subtype of childhood leukemia and age at diagnosis, although these were underpowered.
Our study has some shortcomings. We were able to obtain data from all ten hospitals only after 2002, thus exposure assessment is not uniformly complete for sub- jects born prior to that year. Only a minor improvement in statistical power would have been reached by collect- ing pediatric CT scans from the rest of the imaging cen- ters in Finland. In addition, there is no reason to assume that the missed CT scans would have been unequally dis- tributed for the cases and controls, i.e. result in differen-
tial misclassification. For dose estimation, complete infor- mation on the scanning parameters is included in the modern picture archiving systems, but was not available before the year 2000. Use of parameters for each individ- ual scan would have provided more accurate dose esti- mates. The unexpectedly lower median dose of cases for older scanners found in our sensitivity analysis may be due to random error. The number of different CT scan- ners in our analysis was limited and thus the estimates of average dose were imprecise.
Our results support the notion that even small doses of radiation from pediatric CT scans produce a small, but detectable increase in leukemia risk. In the subgroup analyses, we observed no substantial differences by age or leukemia subtype, although slightly higher risks were found for precursor B-cell acute lymphoblastic leukemia.
Acknowledgments
The authors would like to thank Isabelle Thierry-Chef (IARC), Hannele Niiniviita (Turku University Hospital), Juha Suutari (STUK) and Rebecca Smith-Bindman (University of California, San Francisco) for their valuable suggestions and comments regarding modeling of CT scan doses with the data available in Finland. We are also grateful to Dr Choonsik Lee (National Cancer Institute) for his insightful comments related to modeling contrast media and for providing us with his state-of- the-art dose calculation software (NCICT) and Anniriikka Rantala (STUK) for collecting the data on CT scanners used in Finland. Päivi Laarne’s (Tampere University Hospital) crucial input regarding the scanning parameters enabled us to use NCICT software. Funding for the study was obtained from the Finnish Foundation for Pediatric Research, Väre Foundation for Pediatric Cancer Research and Competitive State Research Financing of the Expert Responsibility area of Tampere University Hospital (9T030 and 9U030).
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Adherence to the Western, Prudent, and Mediterranean dietary patterns and chronic lymphocytic leukemia in the MCC-Spain study
Ferrata Storti Foundation
Marta Solans,1,2,3* Adela Castelló,1,4,5* Yolanda Benavente,1,6
Rafael Marcos-Gragera,2,3 Pilar Amiano,1,7 Esther Gracia-Lavedan,1,8,9
Laura Costas,6 Claudia Robles,10 Eva Gonzalez-Barca,11
Esmeralda de la Banda,12 Esther Alonso,12 Marta Aymerich,13 Elias Campo,13 Trinidad Dierssen-Sotos,1,14 Guillermo Fernández-Tardón,1,15
Rocio Olmedo-Requena,1,16,17 Eva Gimeno,18 Gemma Castaño-Vinyals,1,8,9,19, Nuria Aragonés,1,20 Manolis Kogevinas,1,8,9,19 Silvia de Sanjose,1,6,21
Marina Pollán1,4** and Delphine Casabonne1,6**
Haematologica 2018 Volume 103(11):1881-1888
1Centro de Investigación Biomédica en Red: Epidemiología y Salud Pública (CIBERESP), Madrid, Spain; 2Research Group on Statistics, Econometrics and Health (GRECS), University of Girona, Spain; 3Epidemiology Unit and Girona Cancer Registry, Catalan Institute of Oncology, Girona, Spain; 4Cancer Epidemiology Unit, National Centre for Epidemiology, Carlos III Institute of Health, Madrid, Spain; 5Faculty of Medicine, University of Alcalá, Alcalá de Henares, Madrid, Spain; 6Unit of Molecular Epidemiology and Genetic in Infections and Cancer (UNIC-Molecular), Cancer Epidemiology Research Programme (IDIBELL), Catalan Institute of Oncology, L' Hospitalet De Llobregat, Spain; 7Public Health Division of Gipuzkoa, BioDonostia Research Institute, San Sebastian, Spain; 8ISGlobal, Barcelona, Spain; 9Universitat Pompeu Fabra (UPF), Barcelona, Spain; 10Unit of Information and Interventions in Infections and Cancer (UNIC-I&I), Cancer Epidemiology Research Programme, (IDIBELL), Catalan Institute of Oncology, L' Hospitalet De Llobregat, Spain; 11Hematology, Bellvitge Biomedical Research Institute (IDIBELL), Catalan Institute of Oncology, L'Hospitalet de Llobregat, Spain; 12Hematology Laboratory, Department of Pathology, Hospital Universitari de Bellvitge, L'Hospitalet de Llobregat, Spain; 13Hospital Clinic de Barcelona, University of Barcelona, CIBERONC, Barcelona Spain; 14University of Cantabria - Marqués de Valdecilla Research Institute (IDIVAL), Santander, Spain; 15University Institute of Oncology (IUOPA), University of Oviedo, Spain; 16Department of Preventive Medicine and Public Health, University of Granada, Spain; 17Instituto de Investigación Biosanitaria de Granada, Hospitales Universitarios de Granada, Spain; 18Hematology Department, Hospital del Mar, Barcelona, Spain; 19Hospital del Mar Medical Research Institute (IMIM), Barcelona, Spain; 20Epidemiology Section, Public Health Division, Department of Health of Madrid, Spain and 21PATH, Reproductive Health, Seattle, WA, USA
*MS and AC contributed equally to this work. **MP and DC contributed equally to this work.
ABSTRACT
Diet is a modifiable risk factor for several neoplasms but evidence for chronic lymphocytic leukemia (CLL) is sparse. Previous stud- ies examining the association between single-food items and CLL risk have yielded mixed results, while few studies have been conducted on overall diet, reporting inconclusive findings. This study aimed to eval- uate the association between adherence to three dietary patterns and CLL in the multicase-control study (MCC-Spain) study. Anthropometric, sociodemographic, medical and dietary information was collected for 369 CLL cases and 1605 controls. Three validated dietary patterns, Western, Prudent and Mediterranean, were reconstructed in the MCC- Spain data. The association between adherence to each dietary pattern and CLL was assessed, overall and by Rai stage, using mixed logistic regression models adjusted for potential confounders. High adherence to a Western dietary pattern (i.e. high intake of high-fat dairy products, processed meat, refined grains, sweets, caloric drinks, and convenience food) was associated with CLL [ORQ4 vs. Q1=1.63 (95%CI 1.11; 2.39); P-trend=0.02; OR 1-SD increase=1.19 (95%CI: 1.03; 1.37)], independent- ly of Rai stages. No differences in the association were observed accord- ing to sex, Body Mass Index, energy intake, tobacco, physical activity, working on a farm, or family history of hematologic malignancies. No associations were observed for Mediterranean and Prudent dietary pat- terns and CLL. This study provides the first evidence for an association between a Western dietary pattern and CLL, suggesting that a propor- tion of CLL cases could be prevented by modifying dietary habits. Further research, especially with a prospective design, is warranted to confirm these findings.
Correspondence:
dcasabonne@iconcologia.net
Received: March 6, 2018. Accepted: June 25, 2018. Pre-published: June 28, 2018.
doi:10.3324/haematol.2018.192526
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1881
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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ARTICLE
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Introduction
Chronic lymphocytic leukemia (CLL) is the commonest leukemia among the adult population in Western coun- tries, with an annual incidence rate of around 5 per 100,000 person-years in Europe,1 but its etiology is still poorly understood. A pooled analysis of 2440 CLL cases and 15,186 controls from the InterLymph consortium showed significant inverse associations with atopic condi- tions, smoking, blood transfusion history, and recreational sun exposure, and positive associations with height, hep- atitis C virus seropositivity, living or working on a farm, working as a hairdresser, and family history of hematolog- ic malignancies.2
Diet is a modifiable risk factor for several neoplasms,3 but evidence for CLL is inconclusive. Epidemiological data on the association of diet and CLL are heterogeneous, and mainly arise from studies on nutrients or single food items. While most prospective studies4-12 did not find any association with a wide range of dietary factors, case-con- trol studies13-25 have yielded contradictory results for items such as meat, dairy or vegetable intake. Some authors argue that focusing on overall dietary patterns instead of on individual foods or nutrients may better capture dietary variability in the population’s diet while allowing the evaluation of interactions between dietary factors.26 However, the few studies that have been conducted on overall diet and CLL25,27,28 reported inconclusive findings, mainly due to small sample size.
A population-based multicase-control study (MCC- Spain) was launched to evaluate the influence of environ- mental exposures and their interaction with genetic fac- tors in CLL, among other cancers.29 The aim of the present study was to evaluate the association between adherence to three validated dietary patterns,30 Western, Prudent and Mediterranean, and CLL in the MCC-Spain study.
Methods
Study population
MCC-Spain is a multicentric case-control study with population controls and cases with common tumors (prostate, breast, colorec- tal, gastroesophageal and CLL) in Spain. Between 2010 and 2013, CLL cases aged 20-85 years were recruited in 11 Spanish hospitals from 5 Spanish provinces (Asturias, Barcelona, Cantabria, Girona and Granada). Simultaneously, population-based controls frequen- cy-matched to cases according to age (5-year intervals), sex, and province of recruitment were randomly selected from primary care centers within the hospitals’ catchment areas. Participation rates were 87% in cases and 53% in controls, with variability among geographical regions. After applying specific diet exclusion criteria (excluding participants with no dietary data or with miss- ing or implausible energy intakes under 750 or over 4500 kcal/day), a total of 1605 controls and 369 CLL cases were includ- ed in the study. All participants gave informed consent. Approval for the study was obtained from the ethical review boards of all recruiting centers. Additional information regarding the study design has been provided elsewhere.29
Outcome definition
Chronic lymphocytic leukemia cases were diagnosed according to the International Workshop on CLL criteria: presence of an absolute count ≥5 x109 B cells/L for three or more months in peripheral blood and a clonal population of CD5+, CD19+, and
CD23+ B cells.31 All diagnoses were morphologically and immuno- logically confirmed using flow cytometry immunophenotype and complete blood cell count. CLL and small lymphocytic lymphoma were considered the same underlying disease. Given the indolent course of the disease, CLL cases were recruited and interviewed within three years from diagnosis. Disease severity at interview was evaluated using the Rai staging system obtained from medical records and verified by local hematologists. CLL subjects were then categorized into two groups based on Rai stage: a) low-risk category including asymptomatic patients with lymphocytosis only (Rai 0); and b) intermediate/high-risk category including patients with either lymphadenopathy, hepatomegaly, splenomegaly, anemia and/or thrombocytopenia (Rai I-IV).
Data collection
Data on socio-demographic factors, lifestyle and personal/fam- ily medical history were collected through face-to-face interviews performed by trained personnel. Height and weight at different ages were self-reported. The questionnaire in Spanish is available at www.mccspain.org.
In addition, subjects were provided a semi-quantitative Food Frequency Questionnaire (FFQ), which was a modified version from a previous tool validated in Spain to include regional prod- ucts.32 The FFQ was self-administered and returned by mail or filled out face-to-face. It included 140 food items with portion sizes specified for each item, and assessed usual dietary intake during the previous year. Cross-check questions on aggregated food group consumption were used to adjust the frequency of food consumption and reduce misreporting of food groups with large numbers of items.33 Nutrient intakes were estimated using food composition tables published for Spain, and other sources.34 The response rate of the FFQ was slightly lower in cases (82%) than in controls (87%). Overall, responsiveness was not associated with age, and individuals from Granada were less likely to answer the FFQ than those from Barcelona. Those individuals who did not answer the diet questionnaire had a lower level of education and, in controls, were also more likely to be women.
Dietary patterns
Three validated dietary patterns identified in a Spanish case- control study (EpiGEICAM)30 were reconstructed in the MCC- study: a) a Western dietary pattern characterized by high intake of high-fat dairy products, processed meat, refined grains, sweets, caloric drinks, convenience food and sauces; b) a Prudent pattern, with high intake of low-fat dairy products, vegetables, fruits, whole grains and juices; and c) a Mediterranean pattern, defined by a high intake of fish, vegetables, legumes, boiled potatoes, fruits, olives, and vegetable oil. Further information on identifica- tion of the dietary patterns can be found elsewhere.30 In brief, dietary information extracted from a semi-quantitative question- naire in the EpiGEICAM study was converted to mean daily intake in grams and grouped into 26 food categories. Major exist- ing dietary patterns were identified in the control population by applying principal components analysis (PCA) without rotation of the variance-covariance matrix over the 26 inter-correlated food groups. The set of loadings obtained represent the correlation between the consumption of each food group and the compo- nent/pattern score, and can be used to apply such patterns to other populations.35 In the MCC-study, we grouped the FFQ items into thesame26foodgroups(OnlineSupplementary TableS1),andcal- culated the score of adherence to the Western, Prudent and Mediterranean dietary patterns as a linear combination of the loads described in the EpiGEICAM study and the log-transformed centered food group consumption reported by the participants of MCC-Spain study.
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Figure 1. Association between adherence to dietary patterns and chron- ic lymphocytic leukemia in the multicase-control (MCC- Spain) study. OR: Odds Ratio; 95%CI: 95% confi- dence interval; Q: quartile; SD: standard deviation. Black squares indicate OR and horizontal lines repre- sent 95%CI. 1Logistic regression models adjusted for age, sex, education, energy intake (kcal/day) with province of residence as random effect.
Statistical analysis
As descriptive analyses, we compared anthropometric, socio- demographic and lifestyle characteristics between cases and con- trols. χ2 test was used to evaluate the level of significance of the differences observed in categorical variables, Student t-test for nor- mally distributed continuous variables, and Wilcoxon rank-sum test for non-normally distributed continuous variables. In addi- tion, we analyzed the distribution of each dietary pattern (contin- uous) across categories of descriptive variables. Student t-test was used to assess differences observed in variables with two cate- gories and ANOVA for those with more than two categories.
The association between the dietary patterns and CLL was eval- uated using mixed logistic regression models with random province-specific intercepts. The exposure variables (adherence to Western, Prudent or Mediterranean patterns) were included in the model both as continuous variables [1-standard deviation (SD) increase in the controls’ scores] and as categorical variables (according to the quartile distribution in all controls). All models were adjusted for age (years, continuous), sex, education (no for- mal education, primary school, secondary school, university), and energy intake (kcal/day, continuous) as fixed effects and province of residence as a random effect term. Height (cm, continuous), waist-to-hip ratio (continuous), Body Mass Index (BMI in kg/m2, continuous), experience working on a farm (yes, no), family histo- ry of hematologic malignancies (yes, no), alcohol consumption (g/day, continuous), smoking status (never, past, current), and physical activity [in the last 10 years, measured in Metabolic Equivalent of Task (METs)/week: inactive (0), low (0.1-8), moder- ate (8-15.9) and very active (≥16)] were examined as potential con- founders, but were not included in the final models as they were not found alone, or in combination, to affect the estimates. Interaction terms were modeled between each of these separate variables and the dietary score (continuous), and tested using log- likelihood ratio tests. A possible effect modification of sex, BMI, energy intake, tobacco, physical activity, working on a farm, and family history of hematologic malignancies was tested including an interaction term between each of the patterns and such vari-
ables. The estimation of the effects according to Rai stage (0 vs. I-IV) was calculated with multinomial logistic regression models adjusted by the set of variables described above plus province of residence as random effect term. Finally, sensitivity analyses were performed to examine how the inclusion of: i) cases with longer period of time from diagnosis to recruitment (<1 year vs. ≥ 1 year); and ii) cases treated before the interview affected the overall esti- mates. Odds Ratios (OR) and 95% confidence intervals (CI) were also obtained with multinomial logistic regression models. The P-value for heterogeneity of effects across Rai stage and for sensi- tivity analyses was obtained with the Wald test. All analyses were performed using STATA/MP (v.14.1, 2015, StataCorp LP) and sta- tistical significance was set at two-sided P<0.05.
Results
Distribution of baseline characteristics between cases and controls is shown in Table 1. Compared with controls, cases were more adherent to the Western pattern, while no differences in level of adherence to the Prudent and Mediterranean patterns were observed in bivariate analy- ses. CLL cases were also slightly older, had a higher waist- to-hip ratio, and were more likely to have a family history of hematologic malignancy and to have worked on a farm. No other differences were observed for any of the other pre-selected variables.
The distribution of key characteristics of controls according to level of adherence to each dietary pattern is shown in Online Supplementary Figure S1. Controls with greater adherence to a Western pattern were more likely to be men, younger, taller, current smokers, less prone to have worked in farming or agriculture, had a lower BMI and waist-to-hip ratio, and a higher level of education, energy and alcohol intake. Those with a higher adherence to a Prudent pattern were more likely to be women, younger, taller, physically active, never/former smokers,
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Table 1. Baseline characteristics of chronic lymphocytic leukemia for cases and controls in the multicase-control (MCC-Spain) study.
Western, mean (SD)
Prudent, mean (SD) Mediterranean, mean (SD) Province, n(%)
Barcelona Asturias Cantabria Granada Girona
Age (years), mean (SD)
Sex, n(%) Male Female
Energy intake (kcal/day), mean (SD)
Current alcohol intake (g/day), median (IQI)2 BMI (kg/m2), mean (SD)2
Height (cm), mean(SD)2
Waist-to-hip ratio3, n(%)
Low Moderate High Unknown
Smoking status, n(%)
Never Former Current Unknown
Education, n(%)
No formal education Primary
Secondary University
Physical activity4, n(%)
Inactive Low Moderate Very active Unknown
Ever worked in farming or agriculture, n(%) No
Yes
Unknown
Family history of hematologic malignancy, n(%)
No
Yes
Rai stage
Controls (n=1605)
5.88 (1.46)
6.55 (1.12) 7.08 (1.00)
900 (56) 211 (13) 281 (18) 144 (9) 69 (4) 64.30 (10.54)
936 (58)
669 (42) 1901.15 (585.88) 8.80 (0.58;27.32) 26.99 (4.50) 165.63 (8.51)
460 (29) 449 (28) 682 (42) 14 (1)
696 (43) 602 (38) 303 (19) 4 (0)
357 (22) 502 (31) 461 (29) 285 (18)
656 (41) 219 (14) 190 (12) 502 (31) 38 (2)
1257 (78) 323 (20) 25 (2)
1551 (97)
54 (3)
Cases P1 (n=369)
6.06 (1.40) 0.03
6.66 (1.03) 0.07 7.16 (0.88) 0.20
242 (66) 51 (14) 21 (6)
27 (7)
28 (8) 66.19 (10.12)
217 (59)
<0.001
0.002
0.95
152 (41)
1937.91 (612.06) 0.28 8.82 (0.83;24.47) 0.75
27.32 (4.43) 0.21 165.97 (9.11) 0.50
77 (21) 98 (27) 192 (52) 2 (1)
165 (45) 134 (36) 67 (18) 3 (1)
94 (25) 106 (29) 107 (29) 62 (17)
136 (37) 55 (15) 47 (13) 118 (32) 13 (4)
258 (70) 108 (29) 3 (1)
333 (90)
36 (10)
199(54) 150 (41) 20 (5)
0.004
0.39
0.54
0.50
<0.001
<0.001
0 - I-IV - Unknown -
SD: standard deviation; IQI: interquartile interval; BMI: Body Mass Index. 1P-value for heterogeneity calculated with the Student t-test for comparison of normally distributed con- tinuous variables, with the Wilcoxon rank-sum test for comparison of non-normally distributed continuous variables (alcohol intake), and with the χ2 test for categorical vari- ables. 2% of missing values in continuous variables: alcohol intake (2%), BMI (4%), height (3%). 3Waist-to-hip ratio risk categories according to WHO criteria. 4Physical activity, in the last ten years, measured in METs/week: inactive (0), low (0.1-8), moderate (8-15.9), and very active (≥16). In bold: P<0.05.
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Table 2. Association between adherence to dietary patterns and chronic lymphocytic leukemia by severity of the disease, in the multicase-control (MCC-Spain) study.
Rai 0
Cases N(%) OR1 (95% CI)
(n=199)
45(23) 1
Rai I-IV
Controls N(%) (n=1605)
402(25) 401 (25) 401 (25) 401 (25)
402(25) 401 (25) 401 (25) 401 (25)
402(25) 401 (25) 401 (25) 401 (25)
Cases (n=150)
26(17) 39 (26) 37 (25) 48 (32)
30(20) 37 (25) 32 (21) 51 (34)
29(19) 29 (19) 46 (31) 46 (31)
OR1 (95% CI)
P-het2
Western Q1
Q2
Q3
Q4
P-trend
1-SD increase
Prudent Q1
Q2
Q3
Q4
P-trend
1-SD increase
Mediterranean Q1
Q2
Q3
Q4
P-trend
1-SD increase
47 (24) 47 (24) 60 (30)
1.11 (0.71;1.74) 1.17 (0.73;1.87) 1.60 (0.97;2.65) 0.07
1
1.40 (0.82;2.38) 1.32 (0.76;2.30) 1.71 (0.95;3.06) 0.11
1.15 (0.95;1.39) 42(21) 1
1.26 (1.02;1.56) 0.50
1
1.16 (0.69;1.93) 0.97 (0.56;1.66) 1.47 (0.86;2.51) 0.23
1.18 (0.96;1.45) 0.17
1
0.94 (0.55;1.62) 1.39 (0.83;2.30) 1.32 (0.76;2.27) 0.17
1.15 (0.93;1.41) 0.04
53 (27) 52 (26) 52 (26)
1.09 (0.70;1.70) 1.07 (0.68;1.69) 1.01 (0.62;1.64) 0.98
0.99 (0.83;1.18) 48(24) 1
51 (26) 55 (28) 45 (23)
0.88 (0.57;1.36) 0.88 (0.57;1.37) 0.65 (0.40;1.06) 0.11
0.88 (0.74;1.04)
OR: Odds Ratio; 95% CI: 95% Confidence Interval; Q: quartile; SD: Standard Deviation. 1Multinomial logistical regression models adjusted for age, sex, education, energy intake (kcal/day) with province of residence as a random effect. 2P-value for the heterogeneity of effects. In bold: P<0.05.
more highly educated, less prone to have worked in farm- ing or agriculture, and with a higher energy intake and lower alcohol consumption. Finally, controls with a greater adherence to a Mediterranean pattern were more likely to be men, physically active, showing a lower pro- portion of ever smokers and having worked in farming or agriculture, and a higher energy intake.
Figure 1 summarizes the adjusted ORs for the associa- tion between CLL and level of adherence to the Western, Prudent and Mediterranean dietary patterns. Individuals in the highest quartile of the Western score had an OR for CLL of 1.63 (95%CI: 1.11; 2.39) compared with individu- als with low adherence (P for trend 0.02). Each SD incre- ment in the score was associated with a 19% higher OR of having CLL (95%CI: 1.03; 1.37). No associations were observed for Mediterranean and Prudent diet patterns. The impact of each individual covariate (region, age, sex, education, and energy intake) in the association of the three dietary patterns and CLL is provided in Online Supplementary Figure S2.
Since CLL is more prevalent in men, who are also more likely to adhere to a Western dietary pattern (Table 1 and Online Supplementary Figure S1), all analyses were strati- fied according to sex. No differences across sexes were observed for any of the dietary patterns [P-heterogeneity (P-het): Western (0.79), Prudent (0.11) and Mediterranean (0.17); data not shown]. In addition, no differences were observed according to BMI, energy intake, tobacco, phys- ical activity, working on a farm, and family history of
hematologic malignancies (all P for interaction >0.05; data not shown).
Analyses according to Rai-stage did not show significant heterogeneity of effects for the Western or Prudent dietary patterns (P-het=0.50 and 0.17, respectively). However, weak opposite trends in relation to a Mediterranean diet pattern were observed; it was inversely associated (although not statistically significant) with Rai 0 CLL [OR 1-SD increase= 0.88 (95%CI: 0.74; 1.04)] and positively related with Rai I-IV CLL [OR 1-SD increase= 1.15 (95%CI: 0.93; 1.41)] (P-het=0.04) (Table 2).
Sensitivity analyses according to time from diagnosis to recruitment yielded similar results for the three dietary patterns (Online Supplementary Table S2). Similarly, exclud- ing cases treated prior to consent (n=79) did not materially modify the results [P-het in trends: Western (0.25), Prudent (0.32) and Mediterranean (0.33)], but higher ORs for a Western dietary pattern were observed in cases treat- ed prior to consent in comparison to those not treated (Online Supplementary Table S3).
Discussion
This study provides, for the first time, evidence of an association between adherence to a Western dietary pat- tern and CLL. By contrast, no associations were found for a Prudent or Mediterranean pattern.
There is limited evidence linking extrinsic-risk factors,
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and particularly diet, with non-Hodgkin lymphoma (NHL). In the 2007 report by the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR),3 the Panel decided not to make any judge- ments regarding the causality of associations between specific dietary factors and NHL, but pointed out a sugges- tive inverse association with vegetables, fruit, and alco- holic beverages, and a positive association with meat, total fat, body fatness, and dairy. Recent meta-analyses further support these associations,36,37 but there is still not sufficient evidence to establish a causal role. Similarly, data on the association of diet and CLL are inconclusive and mainly arise from studies on nutrients or single food items. To our knowledge, 9 prospective studies4-12 and 13 case-control studies13-25 have been published on this topic. With the exception of a few studies that found positive associations with consumption of processed meat and poultry,4 total carbohydrate8 or fat (in women)11 intake, and inverse associations with isoflavones consumption,10 gen- erally large prospective studies found no associations between a wide range of dietary factors and CLL. By con- trast, case-control studies have yielded contradictory results for meat,13,14,16,24,25 dairy products,13-17 fish15,18 or veg- etables and fruit14,16,19,22,23,25 intake.
Inconsistencies in previous epidemiological nutritional studies in part reflect the difficulty in disentangling the influence of single food items that, when consumed in combination, may be highly correlated and exert synergis- tic or antagonistic effects on CLL risk. The examination of dietary patterns, which better reflect the complexity of dietary intake, has been used to address such limitations.26 So far, only a few studies have examined associations of dietary patterns and risk of CLL,25,27,28 reporting inconclu- sive findings, mainly due to small sample size. Ollberding et al.28 pointed out that a high adherence to a ‘Meat, Fat and Sweets’ dietary pattern, characterized by a high intake of French fries, red meat, processed meat, pizza, salty snacks, sweets and desserts, was associated with an increased risk of overall NHL (ORQ4 vs. Q1=3.6; 95%CI: 1.9, 6.8) in a Nebraska case-control study. This association was maintained when stratifying according to lymphoma subtypes but sub-analyses did not include CLL cases due to sample size (n=25). By contrast, a large prospective cohort in the US did not find associations with ‘Fat and Meat’ pattern and CLL etiology.27 However, this pattern did not include sweets and deserts, sweetened beverages, or convenience foods, which may be important contribut- ing factors of these associations. Thus, not only differ- ences in the study design and setting, but also in food groups loaded in these data-driven analyses, should be carefully considered when comparing results. In line with our findings, no associations with overall NHL25,27,28 or CLL25,27 were detected for a ‘healthy’ dietary pattern char- acterized by high intake of fruit and vegetables.
We observed opposite trends in relation to a Mediterranean diet pattern and Rai stages, with stronger adherence among cases with higher disease severity (P-het=0.04). We hypothesize that reverse causality could partly explain these results. While Rai 0 patients are usu- ally diagnosed in a routine blood test and present an indo- lent course, Rai I-IV are more prone to be symptomatic (e.g. night sweat, fatigue, weight loss or fever) and to receive active treatment. Thus, those patients with a more severe disease (and probably more concerned about their illness) would be more prone to shift towards a healthier
dietary pattern. However, these results have to be taken with caution since none of the trends showed statistically significant associations.
Chronic lymphocytic leukemia is the most common leukemia in Western countries while its incidence is much lower in Eastern countries, where it accounts for only 1- 3% of NHL in most series.38 While genetic backgrounds may be responsible for some of the differences in the CLL incidence, some studies have suggested that environmen- tal factors also play an important role. A dramatic increase in CLL incidence in Taiwan in recent years was associated with a strong birth-cohort effect, that corresponded to the Westernization of lifestyle in Taiwan since 1960.39 In addi- tion, a higher incidence of CLL has been reported among US-born Asians compared to foreign-born Asians, point- ing out the influence of environmental factors that change with immigration and acculturation to a Westernized lifestyle.40 Our results further support the view that adopt- ing a Western diet could partly explain these incidence patterns.
A Western diet has been associated with obesity pheno- types,41 including a higher waist-to-hip ratio, which has in turn been recently linked to higher OR of CLL, particular- ly in women, in the MCC-Spain study.42 Despite the fact that CLL cases showed a higher waist-to-hip ratio than controls in our study, waist-to-hip ratio and BMI were not included as covariates in the final multiple-adjusted model since they did not change risk estimates. Hence, an inde- pendent effect of the Western dietary pattern may be con- tributing to CLL lymphomagenesis, which seems plausi- ble from a mechanistic point of view. On one hand, it has been well-established that dietary changes, and particular- ly switching from a low-fat, plant polysaccharide-rich diet to a high-fat, high-sugar Western diet, can induce alter- ations in microbiota composition.43 Beyond its role in the biosynthesis of key components (e.g. vitamins, essential amino acids or short chain fatty acid byproducts), several studies using germ-free mice suggest that microbiota also plays a fundamental role on the induction, training, and function of the host immune system.44 Exposure to a Western diet may have selected for a microbiota that lack the resilience and diversity required to establish balanced immune responses, and this phenomenon is proposed to account for some of the dramatic rise in autoimmune and chronic inflammatory disorders found in high-income countries. On the other hand, a diet high in fat, refined grains, red and processed meats, and sweets has been largely associated with higher levels of inflammatory markers45 and with inflammation-related chronic diseases.46 In particular in CLL, the strong production of inflammatory cytokines and chemokines accompanied by activation of intra-cellular pro-inflammatory pathways, and the presence of somatic mutations that activate pro- inflammatory signaling pathways, suggest that chronic inflammation plays a pathophysiological role in this dis- ease.47 Thus, an inflammation-related mechanism may in part underlie the observed associations with CLL, although no research on the inflammatory potential of diet and CLL risk has yet been conducted.
The dietary patterns used in this study were identified using the control population of a multicentric case-control study on female breast cancer in Spain.30 By contrast, the MCC-Spain study included male participants, who may have different dietary habits. However, this difference does not preclude the application of the original scoring
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system over the current sample. Scores of adherence to dietary patterns can be calculated following the exact same rules over different populations, resulting in differ- ent levels of adherence while still being valid, as has been recently proved.35 As a matter of fact, the current dietary patterns had previously been constructed in the MCC- study and a Western dietary pattern was positively associ- ated with gastric,48 breast49 and colorectal50 cancers.
One of the main limitations is the study design since case-control studies are prone to selection and recall bias- es. Measurement errors in the estimation of food intake due to the use of self-reported FFQ are also of some con- cern. However, the FFQ was validated in the Spanish pop- ulation and included regional products.32 Moreover, some questions about general dietary habits were included in the questionnaire and were used to adjust the responses to the FFQ following the methodology described in Calvert et al.33 The inclusion of prevalent cases might be another cause for concern since patients who survived might have a very different etiology than those who died soon after diagnosis. In addition, diet can be influenced by many external factors and patients who survive longer might have substantially modified their diet. However, results of the sensitivity analysis suggested that the use of prevalent cases might not have introduced selective survival bias or reverse causation. We may have been limited by the small sample size and lack of statistical power to detect signifi- cant associations when evaluating certain subgroups. Finally, although we adjusted for a range of potential con- founders, residual confounding factors cannot be totally ruled out.
The strengths of the study include the substantial sam- ple size of CLL cases, with specific information on clinical presentation. We were able to collect detailed information on demographics and disease stage, and statistically adjust for a number of potential confounding factors. This allowed the evaluation of potential interactions of diet
with numerous covariates and the exploration of the asso- ciations by stage. Finally, the multi-centric nature of the study, including both rural and urban areas, provided a wide geographic variability of dietary intake data.
In conclusion, in this Spanish population-based case- control study, greater adherence to a Western dietary pat- tern was associated with CLL. These novel results suggest that a proportion of CLL cases could be prevented by modifying dietary patterns. Further research, especially with a prospective design, is warranted to confirm these findings.
Acknowledgments
The authors would like to thank all the subjects who partici- pated in the study and all CLL MCC-Spain collaborators (the list can be found the Online Supplementary Appendix, List S1).
Funding
Predoctoral contract to MS (CIBERESP), Spanish Ministry of Economy and Competitiveness Juan de la Cierva de Incorporación grant IJCI-2014-20900. Spanish Ministry of Economy and Competitiveness - Carlos III Institute of Health cofunded by FEDER funds/European Regional Develpment Fund (ERDF) - a way to build Europe [(grants PI17/01280, PI11/01810, PI14/01219, PI11/02213, PI09/1662, PI15/00966, RCESP C03/09, RTICESP C03/10, RTIC RD06/0020/0095, RD12/0036/0056, Rio Hortega CM13/00232, SV-09-CLINIC-1 and Centro de Investigación Biomédica en Red: Epidemiología y Salud Pública (CIBERE- SP))] and the Agència de Gestió d'Ajuts Universitaris i de Recerca AGAUR (2017SGR1085, 2014SGR756). The ICGC CLL-Genome Project was funded by Spanish Ministerio de Economía y Competitividad (MINECO) through the Instituto de Salud Carlos III (ISCIII), PMP15/00007 and Centro de Investigación Biomédica en Red: Oncología (CIBERONC). ISGlobal is a member of the CERCA Programme, Generalitat de Catalunya.
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Safety of obinutuzumab alone or combined with chemotherapy for previously untreated or relapsed/refractory chronic lymphocytic leukemia in the phase IIIb GREEN study
Ferrata Storti Foundation
Véronique Leblond,1 Melih Aktan,2 Christelle M. Ferra Coll,3
Caroline Dartigeas,4 Jens Kisro,5 Marco Montillo,6 João Raposo,7 Jean-Louis Merot,8 Susan Robson,9 Ekaterina Gresko,9 Francesc Bosch,10 Stephan Stilgenbauer11 and Robin Foà12
1UPMC GRC11-GRECHY, AP-HP Hôpital Pitié-Salpêtrière, Paris, France; 2Istanbul Üniversitesi, Turkey; 3Institut Català d'Oncologia (ICO), Hospital Germans Trias i Pujol, Josep Carreras Leukaemia Research Institute, Barcelona, Spain; 4Hôpital Bretonneau CHU de Tours, France; 5Onkologische Schwerpunktpraxis Lübeck, Germany; 6Niguarda Cancer Center, ASST Grande Ospedale Metropolitano Niguarda, Milan, Italy; 7Hospital de Santa Maria, Lisbon, Portugal; 8IQVIA, St Ouen, France; 9F. Hoffmann-La Roche Ltd., Basel, Switzerland; 10University Hospital Vall d’Hebron, Barcelona, Spain; 11Internal Medicine III, Ulm University, Germany and 12Hematology, ‘Sapienza’ University,
Haematologica 2018 Volume 103(11):1889-1898
Rome, Italy
ABSTRACT
The safety of obinutuzumab, alone or with chemotherapy, was studied in a non-randomized, open-label, non-comparative, phase IIIb study (GREEN) in previously untreated or relapsed/refractory chronic lymphocytic leukemia. Patients received obinutuzumab 1000 mg alone or with chemotherapy (investigator’s choice of fludarabine- cyclophosphamide for fit patients, chlorambucil for unfit patients, or bendamustine for any patient) on days 1, 8 and 15 of cycle 1, and day 1 of cycles 2-6 (28-day cycles), with the cycle 1/day 1 dose administered over two days. The primary end point was safety/tolerability. Between October 2013 and March 2016, 972 patients were enrolled and 971 treat- ed (126 with obinutuzumab monotherapy, 193 with obinutuzumab-flu- darabine-cyclophosphamide, 114 with obinutuzumab-chlorambucil, and 538 with obinutuzumab-bendamustine). Grade ≥3 adverse events occurred in 80.3% of patients, and included neutropenia (49.9%), throm- bocytopenia (16.4%), anemia (9.6%), and pneumonia (9.0%); rates were similar in first-line and relapsed/refractory patients, and in first-line fit and unfit patients. Using expanded definitions, infusion-related reactions were observed in 65.4% of patients (grade ≥3, 19.9%; mainly seen dur- ing the first obinutuzumab infusion), tumor lysis syndrome in 6.4% [clinical and laboratory; highest incidence with obinutuzumab-ben- damustine (9.3%)], and infections in 53.7% (grade ≥3, 20.1%). Serious and fatal adverse events were seen in 53.1% and 7.3% of patients, respectively. In first-line patients, overall response rates at three months post treatment exceeded 80% for all obinutuzumab-chemotherapy com- binations. In the largest trial of obinutuzumab to date, toxicities were generally manageable in this broad patient population. Safety data were consistent with previous reports, and response rates were high. (clinicaltrials.gov identifier: 01905943).
Introduction
Obinutuzumab (GA101) is a glycoengineered, type II anti-CD20 antibody, which has demonstrated significant activity and adequate tolerability in chronic lympho- cytic leukemia (CLL), including studies where the drug was administered as monotherapy or combined with chemotherapy.1-7 Based on the results of the piv- otal phase III CLL11 trial,2,3 in which the combination of obinutuzumab and chlo- rambucil (G-Clb) was shown to be clinically superior (in terms of progression-free survival and treatment response) to rituximab plus chlorambucil in adult patients with previously untreated CLL and comorbidities, obinutuzumab was approved
Correspondence:
veronique.leblond@aphp.fr
Received: December 21, 2017. Accepted: July 4, 2018. Pre-published: July 5, 2018.
doi:10.3324/haematol.2017.186387
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1889
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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(as G-Clb; in November 2013 in the US and May 2014 in Europe) for this indication.8,9
Following its approval in CLL, a large study (GREEN) was undertaken to further inform the risk-benefit profile of obinutuzumab in a broad population of patients that is representative of that encountered in everyday practice. GREEN (clinicaltrials.gov identifier: 01905943) is an ongoing phase IIIb safety study of obinutuzumab, as a single agent or in combination with chemotherapy, in fit [defined as a Cumulative Illness Rating Scale (CIRS) score of ≤6 and cre- atinine clearance (CrCl) ≥70 mL/minute (min)] and unfit (defined as a CIRS score of >6 and/or CrCl <70 mL/min) patients with previously untreated (first-line) or relapsed/refractory (R/R) CLL. This study is collecting safety data for the largest cohort of CLL patients treated with obinutuzumab to date.
This paper reports data for the primary objective of the GREEN study (a primary analysis snapshot), which was to assess the overall safety and tolerability of obinutuzumab- based treatment. An exploratory objective was to investi- gate the effectiveness of different approaches (including a modified initial obinutuzumab dosage, slower infusion rate and additional steroid pre-medication) to reduce infu- sion-related reactions (IRRs), which were observed during obinutuzumab infusion in the CLL11 trial, particularly during the first administration.2
Methods
Design
GREEN is a non-randomized, non-comparative, open-label study. Patients received intravenous obinutuzumab 1000 mg, alone or with chemotherapy [investigator’s choice of fludarabine- cyclophosphamide (FC), Clb or bendamustine (benda), based pri- marily on fitness; see Online Supplementary Appendix], on days 1 (split over 2 consecutive days), 8 and 15 of cycle 1, and on day 1 of cycles 2-6 (six 28-day cycles). Alternative administration approaches for the first obinutuzumab infusion were studied in three first-line cohorts to assess their effect on IRR mitigation (Online Supplementary Appendix). Patients received intravenous prednisolone (or equivalent) 1 hour (h) pre-dose on day 1/day 2 of cycle 1.
Risk minimization measures, including prophylaxis and investi- gator training (Online Supplementary Appendix), were instigated for patients considered at risk of tumor lysis syndrome (TLS; defined initially as nodes ≥10 cm, or ≥5-<10 cm with lymphocytes ≥25×109/L; definition later expanded for G-benda-treated patients following 2 fatal TLS cases) (Online Supplementary Appendix). Neutropenia prophylaxis was also recommended (Online Supplementary Appendix).
GREEN was conducted according to the Declaration of Helsinki, Good Clinical Practice guidelines, and local laws/regula- tions. Study documentation was approved by institutional review boards/ethics committees at each site. Patients gave written informed consent.
Patients
Patients were aged 18 years or over with CLL requiring treat- ment [National Cancer Institute/International Workshop on Chronic Lymphocytic Leukemia (NCI/iwCLL) criteria10], an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 and adequate hematologic function (see Online Supplementary Appendix for eligibility criteria).
Study procedures
Adverse events (AEs) were graded by NCI Common Terminology Criteria for AEs version 4.0. Response was assessed by investigators according to NCI/iwCLL criteria10 at the final response assessment, scheduled 84 days after the last dose of study medication.
Statistical analysis
The primary end point was safety/tolerability. Safety outcomes included AEs, grade ≥3 AEs (primary outcome of interest), serious AEs (SAEs), and AEs of special/particular interest (AESIs/AEPIs). Overall response rate (ORR) and complete response [(CR; includ- ing CR with incomplete marrow recovery (CRi)] at the final response assessment were among the secondary efficacy end points (Online Supplementary Appendix). Time-to-event end points are not presented due to insufficient follow up (median, 20.8-28.8 months, depending on treatment); post-treatment fol- low up is still ongoing for patients who have not discontinued the study.
IRRs were defined as any AE occurring during/within 24 h of obinutuzumab infusion and considered related to obinutuzumab. IRR incidence in first-line patients was an exploratory end point.
Safety was evaluated in patients treated with at least one dose of study medication. Response was assessed in the intent-to-treat (ITT) population comprising all enrolled patients. A sample size of 950 patients [630 first-line (approximately equal proportions of fit and unfit) and 320 R/R patients] was planned [based on adequate precision, by 95% Clopper-Pearson confidence intervals (CIs), to estimate incidence rate of grade ≥3 AEs if the observed rate was 1-25%], with no formal statistical hypothesis testing. As a non-randomized study, treatment comparability was not applica- ble.
Data are presented using descriptive statistics. Incidence rates and two-sided 95% Clopper-Pearson CI were calculated for grade ≥3 AEs and ORRs.
Additional AEs and response amendments were reported late by some sites. While not captured here, updates are reported in the Online Supplementary Appendix.
Results
Patients
Patients were enrolled between October 2013 and March 2016 at 169 centers in 31 countries in Africa, North and South America, Asia and Europe. This primary analy- sis took place after all treated patients had finished study treatment and undergone a final response assessment (data cut-off for primary snapshot analysis, December 29, 2016).
The ITT population comprised 972 patients and the safety population included 971 patients [630 (64.8%) first- line, including 339 (34.9%) fit (CIRS ≤6 and CrCl ≥70 mL/min) and 291 (29.9%) unfit (CIRS >6 and/or CrCl <70 mL/min) patients; and 341 (35.1%) R/R patients]; one first-line patient was enrolled but not treated and there- fore not included in the safety population. Seven patients from one site in Romania were excluded from the analy- ses due to non-compliance with Good Clinical Practice guidelines.
At the data cut-off, 195 (20.1%; 80 first-line and 115 R/R) ITT patients had discontinued the study and 777 (79.9%; 551 first-line and 226 R/R) were still on study (all in follow up). Primary reasons for study discontinuation included death [n=105 (10.8%); 40 first-line and 65 R/R], withdrawal of consent (n=63, 6.5%), AE (n=10, 1.0%),
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loss to follow up (n=9, 0.9%), investigator decision (n=4, 0.4%) and other (n=4, 0.4%).
In the ITT population, median age was 66.0 (range 33-90) years, 63.5% of patients were male, 59.6%/36.9%/3.5% had an ECOG performance status of
0/1/2, 79.2% had a CIRS score of ≤6 and 61.0% had CrCl ≥70 mL/min (Table 1). Binet stage distribution at screening was 25.3% stage A, 41.2% stage B, 32.9% stage C and 0.6% missing. Five hundred and thirty-three (54.8%) patients had a high tumor burden (with nodes ≥10 cm, or
Table 1. Demographics and baseline disease characteristics according to line of therapy and fitness of patients (intent-to-treat population).
Characteristic
Median age, (range) years Age ≥65 years, n (%) Age ≥75 years, n (%)
Male, n (%)
ECOG performance status, n(%)
0 1 2
Binet stage, n(%) A
B
C Missing
B symptoms, n (%)*
Bulky disease (≥5 cm), n(%)
Lymphocytes ≥25x109/L, n(%) Total CIRS score, n(%)
>6
CrCl at screening, n(%)
Negative Positive Missing
CD38 expression, n(%)
Negative Positive Missing
Cytogenetics, n(%) 17p deletion
11q deletion
12q trisomy
13q deletion Other
No abnormality Missing
IgVH mutation status, n (%)
Mutated Unmutated Missing
First-line fit (n=339)
59.0 (33-82) 102 (30.1) 15 (4.4) 233 (68.7)
237 (69.9) 98 (28.9) 4 (1.2)
97 (28.6) 161 (47.5) 81 (23.9) 0
120 (35.4)
240 (70.8) 259 (76.4)
339 (100) 0
0
339 (100)
87 (25.7) 189 (55.8) 63 (18.6)
140 (41.3) 134 (39.5) 65 (19.2)
14 (4.1) 55 (16.2) 45 (13.3) 106 (31.3) 18 (5.3) 58 (17.1) 43 (12.7)
101 (29.8) 181 (53.4) 57 (16.8)
First-line unfit (n=292)
72.0 (45-87) 223 (76.4) 114 (39.0) 166 (56.8)
154 (52.7) 127 (43.5) 11 (3.8)
72 (24.7) 112 (38.4) 108 (37.0) 0
87 (29.8)
149 (51.0) 230 (78.8)
172 (58.9) 120 (41.1)
230 (78.8)
62 (21.2)
72 (24.7) 146 (50.0) 74 (25.3)
104 (35.6) 115 (39.4) 73 (25.0)
20 (6.8) 33 (11.3) 48 (16.4) 97 (33.2) 7 (2.4) 43 (14.7) 44 (15.1)
90 (30.8) 146 (50.0) 56 (19.2)
First-line all (n=631)
65.0 (33-87) 325 (51.5) 129 (20.4) 399 (63.2)
391 (62.0) 225 (35.7) 15 (2.4)
169 (26.8) 273 (43.3) 189 (30.0) 0
207 (32.8)
389 (61.6) 489 (77.5)
511 (81.0) 120 (19.0)
230 (36.5)
401 (63.5)
159 (25.2) 335 (53.1) 137 (21.7)
244 (38.7) 249 (39.5) 138 (21.9)
34 (5.4) 88 (13.9) 93 (14.7) 203 (32.2) 25 (4.0) 101 (16.0) 87 (13.8)
191 (30.3) 327 (51.8) 113 (17.9)
R/R (n=341)
68.0 (33-90) 213 (62.5) 98 (28.7) 218 (63.9)
188 (55.1) 134 (39.3) 19 (5.6)
77 (22.6) 127 (37.2) 131 (38.4) 6 (1.8) 114 (33.4)
210 (61.6) 214 (62.8)
259 (76.0) 82 (24.0)
149 (43.7)
192 (56.3)
84 (24.6) 160 (46.9) 97 (28.4)
93 (27.3) 153 (44.9) 95 (27.9)
46 (13.5) 67 (19.6) 33 (9.7) 79 (23.2) 16 (4.7) 33 (9.7) 67 (19.6)
64 (18.8) 188 (55.1) 89 (26.1)
Total (n=972)
66.0 (33-90) 538 (55.3) 277 (28.5) 617 (63.5)
579 (59.6) 359 (36.9) 34 (3.5)
246 (25.3) 400 (41.2) 320 (32.9) 6 (0.6) 321 (33.0)
599 (61.6) 703 (72.3)
770 (79.2) 202 (20.8)
379 (39.0)
593 (61.0)
243 (25.0) 495 (50.9) 234 (24.1)
337 (34.7) 402 (41.4) 233 (24.0)
80 (8.2) 155 (15.9) 126 (13.0) 282 (29.0) 41 (4.2) 134 (13.8) 154 (15.8)
255 (26.2) 515 (53.0) 202 (20.8)
≤6
<70 mL/min
≥70 mL/min
ZAP-70 expression, n(%)
R/R: relapsed/refractory; ECOG: Eastern Cooperative Oncology Group; CIRS: Cumulative Illness Rating Scale; CrCl: creatinine clearance; n: number; min: minute. *Patients with at least one B symptom (unexplained fever >38°C, drenching night sweats >1 month or weight loss >10% of body mass in preceding 6 months).
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Table 2. Summary of adverse events according to line of therapy and fitness of patients (safety population).
N (%) First-line fit First-line unfit First-line all
R/R (n=341)
334 (97.9) 198 (58.1) 101 (29.6) 115 (33.7) 94 (27.6) 83 (24.3) 57 (16.7) 44 (12.9) 42 (12.3) 46 (13.5) 55 (16.1) 42 (12.3) 55 (16.1) 46 (13.5) 42 (12.3) 46 (13.5)
281 (82.4) 179 (52.5) 67 (19.6) 40 (11.7) 46 (13.5) 27 (7.9) 29 (8.5) 16 (4.7) 20 (5.9)
40 (11.7) 7 (2.1) 2 (0.6) 2 (0.6) 3 (0.9) 0
0
2 (0.6) 0
197 (57.8) 43 (12.6) 48 (14.1) 25 (7.3) 8 (2.3) 11 (3.2) 12 (3.5)
189 (55.4) 90 (26.4) 68 (19.9)
Total (n=971)
950 (97.8) 567 (58.4) 311 (32.0) 303 (31.2) 270 (27.8) 230 (23.7) 157 (16.2) 135 (13.9) 135 (13.9) 118 (12.2) 116 (11.9) 115 (11.8) 114 (11.7) 109 (11.2) 104 (10.7) 99 (10.2)
780 (80.3) 485 (49.9) 159 (16.4) 93 (9.6) 87 (9.0) 74 (7.6) 66 (6.8) 62 (6.4) 49 (5.0)
71 (7.3) 12 (1.2) 5 (0.5) 4 (0.4) 3 (0.3) 2(0.2) 2 (0.2) 2 (0.2) 2 (0.2)
516 (53.1) 105 (10.8) 92 (9.5) 68 (7.0) 36 (3.7) 36 (3.7) 31 (3.2)
521 (53.7) 195 (20.1) 193 (19.9)
(n=339) (n=291)
AEs of any grade (in ≥10% of patients in the safety population by preferred term)
(n=630)
Any
Neutropenia Pyrexia Thrombocytopenia Nausea
Anemia
Chills
Diarrhea
Vomiting
Fatigue Pneumonia Constipation Cough Leukopenia Hypotension Dyspnea
328 (96.8) 216 (63.7) 112 (33.0) 99 (29.2) 99 (29.2) 68 (20.1) 47 (13.9) 47 (13.9) 57 (16.8) 31 (9.1) 28 (8.3) 35 (10.3) 27 (8.0) 43 (12.7) 26 (7.7) 28 (8.3)
288 (99.0) 153 (52.6) 98 (33.7) 89 (30.6) 77 (26.5) 79 (27.1) 53 (18.2) 44 (15.1) 36 (12.4) 41 (14.1) 33 (11.3) 38 (13.1) 32 (11.0) 20 (6.9) 36 (12.4) 25 (8.6)
616 (97.8) 369 (58.6) 210 (33.3) 188 (29.8) 176 (27.9) 147 (23.3) 100 (15.9) 91 (14.4) 93 (14.8) 72 (11.4) 61 (9.7) 73 (11.6) 59 (9.4) 63 (10.0) 62 (9.8) 53 (8.4)
499 (79.2) 306 (48.6) 92 (14.6) 53 (8.4) 41 (6.5) 47 (7.5) 37 (5.9) 46 (7.3) 29 (4.6)
31 (4.9) 5 (0.8) 3 (0.5) 2 (0.3) 0 1(0.2) 2 (0.3) 0
2 (0.3)
319 (50.6) 62 (9.8) 44 (7.0) 43 (6.8) 28 (4.4) 25 (4.0) 19 (3.0)
332 (52.7) 105 (16.7) 125 (19.8)
Grade ≥3 AEs (in ≥5% of patients in the safety population by preferred term)
Any
Neutropenia Thrombocytopenia Anemia
Pneumonia
Febrile neutropenia Leukopenia
TLS
Lymphopenia
266 (78.5) 177 (52.2) 46 (13.6) 23 (6.8) 17 (5.0) 29 (8.6) 26 (7.7) 14 (4.1) 20 (5.9)
233 (80.1) 129 (44.3) 46 (15.8) 30 (10.3) 24 (8.2) 18 (6.2) 11 (3.8) 32 (11.0) 9 (3.1)
Grade 5 (fatal) AEs (in ≥2 patients in the safety population by preferred term)
Any
Pneumonia
Sepsis
Death
Richter syndrome AML
Febrile neutropenia Septic shock
TLS
13 (3.8) 1 (0.3) 1 (0.3) 1 (0.3) 0 1(0.3) 0
0
1 (0.3)
18 (6.2) 4 (1.4) 2 (0.7) 1 (0.3) 0
0
2 (0.7) 0
1 (0.3)
SAEs (in ≥2% of patients in the safety population by preferred term)
Any
Neutropenia Pneumonia
Febrile neutropenia Pyrexia
TLS Thrombocytopenia
148 (43.7) 39 (11.5) 20 (5.9) 25 (7.4) 15 (4.4) 4 (1.2) 8 (2.4)
171 (58.8) 23 (7.9) 24 (8.2) 18 (6.2) 13 (4.5) 21 (7.2) 11 (3.8)
138 (47.4) 57 (19.6) 65 (22.3)
Grade ≥3 AESIs/AEPIs (basket terms)*
Neutropenia Infections IRRs
194 (57.2) 48 (14.2) 60 (17.7)
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Thrombocytopenia TLS
Second malignancies Second malignancies† Hemorrhagic events HBV reactivation Cardiac events
47 (13.9) 14 (4.1) 12 (3.5) 12 (3.5) 2 (0.6) 0
9 (2.7)
48 (16.5) 32 (11.0) 23 (7.9) 20 (6.9) 2 (0.7) 1 (0.3) 14 (4.8)
95 (15.1) 46 (7.3) 35 (5.6) 32 (5.1) 4 (0.6) 1 (0.2) 23 (3.7)
68 (19.9) 16 (4.7) 26 (7.6) 24 (7.0) 5 (1.5) 0
9 (2.6)
163 (16.8) 62 (6.4) 61 (6.3) 56 (5.8) 9 (0.9)
1 (0.1)
32 (3.3)
PML 0 0 0 1(0.3) 1(0.1)
R/R: relapsed/refractory; AE: adverse event; TLS: tumor lysis syndrome; AML: acute myeloid leukemia; SAE: serious adverse event; AESI: adverse event of special interest; AEPI: adverse event of particular interest; IRR: infusion-related reaction; HBV: hepatitis B virus; PML: progressive multifocal leukoencephalopathy; MedDRA: Medical Dictionary for RegulatoryActivities;n:number;h:hour.*NeutropeniaandthrombocytopeniaselectionwasviatheirMedDRAbasketdatasetsubgroups;infectionselectionwasviatheMedDRA system order class ‘Infections and Infestations’; IRRs were defined as any AE occurring during or within 24 h of obinutuzumab infusion and considered related to obinutuzumab; TLS and PML were defined by their preferred terms; second malignancy selection was via the MedDRA system organ class ‘Neoplasms Benign, Malignant, and Unspecified’ start- ing six months after the first study drug intake; hemorrhagic event selection was via the MedDRA basket dataset subgroup; HBV reactivation was defined as any AE with the pre- ferred term containing ‘hepatitis B’ or ‘hepatitis acute’ that was additionally assessed as HBV reactivation via medical review; and cardiac event selection was via the MedDRA system order class ‘Cardiac Disorders’. †Second malignancy selection [standardized MedDRA query (SMQ)], including malignant and unspecified tumors (wide) starting six months after the first study drug intake.
≥5 cm but <10 cm with lymphocytes ≥25x109/L) and were classified as being at increased risk of TLS. Other criteria also used to determine TLS risk are specified in the Online Supplementary Appendix. Median number of prior lines of therapy received by R/R patients was 1.0 (range 1.0-3.0) (Online Supplementary Table S1).
Treatment exposure
Treatment received was [G-mono; n=126 (12.9%); first- line n=62, R/R n=64), G-FC (n=193 (19.9%); first-line n=153, R/R n=40), G-Clb (n=114 (11.7%); first-line n=68, R/R n=46) and G-benda (n=538 (55.3%); first-line n=347, R/R n=191]. Seven hundred and eighty-nine (81.2%) patients completed all six cycles of protocol-specified treatment and 182 (18.7%) discontinued treatment prema- turely. For all chemotherapy regimens, most patients received all six treatment cycles, i.e. 79.0% for benda, 84.5% for fludarabine, 85.0% for cyclophosphamide, and 76.3% for Clb. The main reasons for not completing study treatment were tolerability [including AEs; n=146 (15.0%)] and withdrawal of consent [n=15 (1.5%)].
Patients received a median of 9 (range 1-13) administra- tions of obinutuzumab, with 94.5% of patients receiving ≥90% of the planned dose. Median exposure time to obin- utuzumab was 20.4 (range 0.1-30.1) weeks.
Safety
Median observation time was 24.5 (range 0.3-37.8) months. In the safety analysis, the most frequent treat- ment-emergent AEs (any grade, by preferred term), occur- ring in ≥20% patients, were neutropenia (58.4%), pyrexia (32.0%), thrombocytopenia (31.2%), nausea (27.8%), and anemia (23.7%), with no notable differences between the first-line and R/R, or fit and unfit subgroups (Table 2). Overall, 23.4% of patients (n=227) had at least one prolonged cytopenia (any grade, occurring during the treatment period and still present >24 days after end of treatment) and 2.4% (n=23) had at least one late-onset cytopenia (any grade, occurring during the post-treatment follow-up period, ≥24 days after end of treatment). AEs were considered related to obinutuzumab in 85.8% of patients, most commonly neutropenia (40.2%), thrombo- cytopenia (22.6%), nausea (16.8%), pyrexia (23.2%) and anemia (11.1%). AEs leading to discontinuation of obinu-
tuzumab occurred in 14.6% of patients (first-line, 14.4%; R/R, 15.0%), with 5.4% discontinuing obinutuzumab due to IRRs, 3.9% due to neutropenia and 1.8% due to throm- bocytopenia. Treatment-emergent AEs by treatment are shown in Table 3.
Severe and serious AEs
Grade ≥3 AEs (the primary safety outcome of interest) occurred in 79.2% (95% CI: 75.8-82.3%) of first-line patients 78.5% (95% CI: 73.7-82.7%) in fit and 80.1% (95% CI:75.0-84.5%) in unfit patients and 82.4% (95% CI:77.9-86.3%) of R/R patients (Table 2). Among the 80.3% of patients overall who experienced grade ≥3 AEs (Table 2), the most frequent events were neutropenia (49.9%), thrombocytopenia (16.4%), anemia (9.6%) and pneumonia (9.0%). The most common SAEs were neutropenia (10.8%), pneumonia (9.5%) and febrile neutropenia (7.0%); the overall rate of SAEs in the safety population was 53.1% (Table 2). Grade ≥3 AEs and SAEs generally occurred at a similar frequency in first-line and R/R patients, and in first-line fit and unfit patients (Table 2), although the overall rate of SAEs was higher in first- line unfit (58.8%) than first-line fit (43.7%) patients.
Deaths
A total of 112 (11.5%) patients died during the study (12 within 28 days of their last dose of study treatment and 100 during the post-treatment follow-up period), primari- ly due to AEs [n=71 (7.3%)]. AEs leading to death were numerically more common in R/R patients [n=40 (11.7%)] than in first-line patients [n=31 (4.9%)]; fit n=13, unfit n=18). Pneumonia [n=12 (1.2%)]) and sepsis [n=5 (0.5%)]) were the most common AEs leading to death (Table 2). By treatment received, the lowest rate of death due to AEs was observed in the G-FC group [4.7% (9/193)] vs. 7.9% (9/114) in the G-Clb group, 7.8% (42/538) in the G-benda group and 8.7% (11/126) in the G-mono group)] (Table 3). Two patients died due to TLS (both in the first-line G-benda subgroup). Disease progression was listed as the primary cause of death in 43 (4.4%) patients.
Adverse events of special or particular interest
AESIs/AEPIs (any grade, as defined in the footnote to Table 2 and Table 3) reported in the overall safety popula-
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Table 3. Summary of adverse events according to treatment (safety population). N (%) G-mono G-FC
(n=126) (n=193)
AEs of any grade (in ≥10% of patients in the safety population by preferred term)
G-Clb (n=114)
113 (99.1) 60 (52.6) 28 (24.6) 36 (31.6) 26 (22.8) 26 (22.8) 17 (14.9) 10 (8.8) 14 (12.3) 22 (19.3) 19 (16.7) 14 (12.3) 15 (13.2) 8 (7.0) 17 (14.9) 11 (9.6)
87 (76.3) 51 (44.7) 22 (19.3) 15 (13.2) 2 (1.8) 10 (8.8) 7 (6.1)
3 (2.6) 5 (4.4) 0
Any
Pneumonia
Sepsis
Death
Richter syndrome
AML 0
Febrile neutropenia 1 (0.8)
Septic shock 1 (0.8)
TLS 0 0 0
G-benda (n=538)
523 (97.2) 314 (58.4) 185 (34.4) 170 (31.6) 146 (27.1) 132 (24.5) 93 (17.3) 80 (14.9) 69 (12.8) 70 (13.0) 66 (12.3) 71 (13.2) 56 (10.4) 71 (13.2) 56 (10.4) 54 (10.0)
429 (79.7) 263 (48.9) 84 (15.6) 49 (9.1) 43 (8.0) 55 (10.2) 7 (1.3) 40 (7.4) 50 (9.3) 39 (7.2)
42 (7.8) 6 (1.1) 2 (0.4) 1 (0.2) 1 (0.2) 0
1 (0.2) 1 (0.2) 2(0.4)
305 (56.7) 52 (9.7) 62 (11.5) 40 (7.4) 21 (3.9) 29 (5.4)
283 (52.6) 103 (19.1) 115 (21.4) 84 (15.6)
Any
Neutropenia Pyrexia Thrombocytopenia Nausea
Anemia
Chills
Diarrhea
Vomiting
Fatigue Pneumonia Constipation Cough Leukopenia Hypotension Dyspnea
123 (97.6) 50 (39.7) 29 (23.0) 28 (22.2) 22 (17.5) 20 (15.9) 17 (13.5) 6 (4.8)
8 (6.3)
7 (5.6) 14 (11.1) 6 (4.8) 15 (11.9) 5 (4.0) 14 (11.1) 10 (7.9)
191 (99.0) 143 (74.1) 69 (35.8) 69 (35.8) 76 (39.4) 52 (26.9) 30 (15.5) 39 (20.2) 44 (22.8) 19 (9.8) 17 (8.8) 24 (12.4) 28 (14.5) 25 (13.0) 17 (8.8) 24 (12.4)
Grade ≥3 AEs (in ≥5% of patients in the safety population by preferred term)
169 (87.6) 129 (66.8) 38 (19.7) 12 (6.2) 21 (10.9) 21 (10.9) 3 (1.6) 20 (10.4) 5 (2.6) 10 (5.2) Grade 5 (fatal) AEs (in ≥2 patients in the safety population by preferred term)
Any
Neutropenia Thrombocytopenia Pneumonia
Febrile neutropenia Anemia Hypotension Leukopenia
TLS
Lymphopenia
95 (75.4) 42 (33.3) 15 (11.9) 11 (8.7) 8 (6.3)
7 (5.6) 6 (4.8) 3 (2.4) 2 (1.6) 0
SAEs (in ≥5% of patients in the safety population by preferred term)
11 (8.7) 1 (0.8) 1 (0.8) 1 (0.8) 1 (0.8)
9 (4.7) 2 (1.0) 2 (1.0) 1 (0.5) 1 (0.5) 1(0.5) 0
9 (7.9) 3 (2.6) 0
1 (0.9) 0 1(0.9) 0
0
0
87 (45.1) 13 (6.7) 28 (14.5) 20 (10.4) 11 (5.7) 3 (1.6)
136 (70.5) 35 (18.1) 30 (15.5) 39 (20.2)
Any
Pneumonia Neutropenia Febrile neutropenia Pyrexia
TLS
67 (53.2) 11 (8.7) 9 (7.1) 6 (4.8) 3 (2.4) 1 (0.8)
49 (38.9) 31 (24.6) 27 (21.4) 16 (12.7)
57 (50.0) 16 (14.0) 6 (5.3) 2 (1.8) 1 (0.9) 3 (2.6)
53 (46.5) 24 (21.1) 23 (20.2) 24 (21.1)
Grade ≥3 AESIs/AEPIs (basket terms)* Neutropenia
IRRs
Infections
Thrombocytopenia
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continued from previous page.
Second malignancies Second malignancies† TLS
Hemorrhagic events HBV reactivation Cardiac events
PML
6 (4.8) 5 (4.0) 2 (1.6) 1 (0.8) 0
3 (2.4)
9 (4.7) 8 (4.1) 5 (2.6)
7 (6.1) 6 (5.3) 5 (4.4)
39 (7.2) 37 (6.9) 50 (9.3)
0 0 8(1.5)
0 0 1(0.2)‡ 6 (3.1) 3 (2.6) 20 (3.7)
1(0.8) 0 0 0
G: obinutuzumab; mono: monotherapy; FC: fludarabine-cyclophosphamide; Clb: chlorambucil; benda: bendamustine; AE: adverse event; TLS: tumor lysis syndrome; AML: acute myeloid leukemia; SAE: serious adverse event; AESI: adverse event of special interest; AEPI: adverse event of particular interest; IRR: infusion-related reaction; HBV: hepatitis B virus; PML: progressive multifocal leukoencephalopathy; MedDRA: Medical Dictionary for Regulatory Activities; n: number; h: hour. *Neutropenia and thrombocytopenia selec- tion was via their MedDRA basket dataset subgroups; infection selection was via the MedDRA system order class ‘Infections and Infestations’; IRRs were defined as any AE occurring during or within 24 h of obinutuzumab infusion and considered related to obinutuzumab; TLS and PML were defined by their preferred terms; second malignancy selection was via the MedDRA system organ class ‘Neoplasms Benign, Malignant, and Unspecified’ starting six months after the first study drug intake; hemorrhagic event selec- tion was via the MedDRA basket dataset subgroup; HBV reactivation was defined as any AE with the preferred term containing ‘hepatitis B’ or ‘hepatitis acute’ that was addi- tionally assessed as HBV reactivation via medical review; and cardiac event selection was via the MedDRA system order class ‘Cardiac Disorders’. †Second malignancy selec- tion: standardized MedDRA query (SMQ),including malignant and unspecified tumors (wide) starting 6 months after the first study drug intake, ‡Three patients had HBV reac- tivation in total, 2 of which were grade <3.
tion were IRRs (65.4%; grade ≥3, 19.9%), neutropenia (61.7%; grade ≥3, 53.7%), infections (53.7%; grade ≥3, 20.1%), thrombocytopenia (32.3%; grade ≥3, 16.8%), car- diac events (11.2%; grade ≥3, 3.3%), second malignancies [(8.4% by MedDRA system organ class, including grade ≥3, 6.3% (listed in full in Online Supplementary Table S2); 7.7% by standardized MedDRA query, including grade ≥3, 5.8%)], hemorrhagic events (7.1%; grade ≥3, 0.9%), TLS (6.4%; all grade ≥3 by definition), hepatitis B virus reactivation (0.3%; grade ≥3, 0.1%) and progressive mul- tifocal leukoencephalopathy (0.1%; grade ≥3, 0.1%). The most commonly reported infections by preferred term were pneumonia (11.9%), bronchitis (6.9%), upper respi- ratory tract infection (6.9%), nasopharyngitis (5.4%) and urinary tract infection (5.4%). Grade ≥3 AESIs/AEPIs were reported at a similar frequency in first-line and R/R patients, and in first-line fit and unfit patients (Table 2); however, grade ≥3 TLS as an AESI was more common in first-line (7.3%) than in R/R patients (4.7%), and in first- line unfit (11.0%) than in first-line fit (4.1%) patients, and grade ≥3 infections as AESIs were more common in R/R patients (26.4%) than in first-line patients (16.7%).
TLS and IRRs
In the 62 patients with TLS events, 32 cases had labora- tory TLS and 30 had clinical TLS. Except for the 2 fatal cases described below, all TLS events resolved, none with sequelae, and there was no recurrence in any patient. In 41 of the 62 patients with TLS, no change in drug dosing was needed; treatment was interrupted or delayed in 17 patients and discontinued in 4 patients. A higher rate of TLS was observed in patients who received G-benda (9.3% overall; 6.6% in first-line fit, 14.4% in first-line unfit, and 6.8% in R/R patients) compared with the other regimens. Of the 2 patients with fatal TLS, one had bulky disease (age 79 years) and the other lymphadenopathy (age 45 years); the older patient also had chronic renal fail- ure at baseline. Both patients died in hospital after cardio- vascular events (sudden cardiac arrest and acute cardiac failure, respectively).
The frequency of IRRs was similar among the three dos- ing cohorts regardless of the IRR mitigation strategy used, although grade ≥3 IRRs, serious IRRs and IRRs leading to obinutuzumab discontinuation were more common in Cohort 3, along with TLS (as a preferred term) (Table 4).
Treatment response
Among first-line patients, the ORR in the ITT popula- tion at the final response assessment was 89.5% with G- FC, 82.4% with G-Clb, 81.8% with G-benda, and 63.5% with G-mono (Table 5); respective CR/CRi rates were 46.4%, 16.2%, 35.7% and 20.6%. In R/R patients, the ORR was 82.5% with G-FC, 54.3% with G-Clb, 72.8% with G-benda and 42.2% with G-mono; CR/CRi rates were 22.5%, 6.5%, 19.9% and 4.7%, respectively. Response rates for the 80 patients with 17p deletion are also shown in Table 5.
Discussion
GREEN evaluated the safety and tolerability of obinu- tuzumab, alone or combined with chemotherapy, in a broad CLL patient population, including first-line (fit and unfit) and R/R patients. The chemotherapy partner options that were available to GREEN investigators mirror those used in standard practice with anti-CD20 antibodies in CLL.11,12 Notably, GREEN represents the first large-scale report of safety data for obinutuzumab in CLL patients following its approval.
While GREEN was subject to certain limitations, the study provides valuable information on the overall safety profile of obinutuzumab, alone or combined with chemotherapy, in a broad CLL population. Importantly, obinutuzumab-based treatment demonstrated a generally manageable toxicity profile. Because of the non-compara- tive/non-randomized study design and potential investigator bias on patient allocation to cohorts/treat- ment, specific treatment regimens could not be compared directly. Furthermore, as treatment allocation was based on investigator’s choice, some subgroups were under-rep- resented [e.g. first-line unfit and fit patients treated with G-mono (n=32 and n=31, respectively), and R/R patients treated with G-FC (n=40) or G-Clb (n=46)], making it dif- ficult to draw conclusions from these small patient cohorts. However, this under-representation was not sur- prising given that most investigators followed current guideline recommendations for treatment.11,12 All patients were also analyzed as treated; for example, the G-mono group included patients who discontinued treatment after their first obinutuzumab administration due to AEs before receiving their planned chemotherapy regimen (n=23), as
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Table 4. Summary of infusion-related reactions according to the approach used to prevent or mitigate these events in first-line patients.
N (%)*
Any IRR
Chills
Pyrexia
Nausea
Vomiting
TLS
Hypertension Hypotension Thrombocytopenia Dyspnea Hypersensitivity Chest discomfort Flushing
Hot flush
Anemia
Oxygen saturation decreased Hyperhidrosis
Headache
Tremor
Rash
AST increased
ALT increased
Feeling hot
Dizziness
Cohort 1 (n=237)†
141 (59.5)
49 (20.7) 45 (19.0) 24 (10.1) 16 (6.8) 14 (5.9) 12 (5.1) 12 (5.1) 8 (3.4)
7 (3.0) 7 (3.0) 6 (2.5) 5 (2.1) 5 (2.1) 5 (2.1) 5 (2.1) 5 (2.1) 3 (1.3) 3 (1.3) 2 (0.8) 2 (0.8) 2 (0.8) 2 (0.8) 1 (0.4)
Cohort 2 (n=228)‡
153 (67.1)
41 (18.0) 24 (10.5) 5 (2.2)
26 (11.4) 42 (18.4) 34 (14.9) 14 (6.1) 6 (2.6) 10 (4.4) 31 (13.6) 16 (7.0) 17 (7.5) 1 (0.4) 10 (4.4) 8 (3.5)
1 (0.4) 3 (1.3) 3 (1.3) 7 (3.1) 12 (5.3) 5 (2.2) 6 (2.6) 8 (3.5) 6 (2.6) 5 (2.2) 5 (2.2)
Cohort 3 (n=151)§
96 (63.6)
37 (24.5) 23 (15.2) 12 (7.9)
13 (8.6) 28 (18.5) 7 (4.6) 4 (2.6) 15 (9.9) 5 (3.3) 4 (2.6) 9 (6.0) 9 (6.0) 1 (0.7) 3 (2.0) 2 (1.3) 1 (0.7) 5 (3.3) N/R
1 (0.7) 5 (3.3) N/R
4 (2.6) 6 (4.0) 6 (4.0) 1 (0.7) N/R
Grade ≥3 IRRs
Serious IRRs
IRRs leading to any obinutuzumab discontinuation
IRRs (reported by ≥2% patients in any cohort, any grade by preferred term)
45 (19.0) 26 (11) 4 (1.7)
IRR: infusion-related reaction; TLS: tumor lysis syndrome; N/R: not reported; AST: aspartate aminotransferase; ALT: alanine aminotransferase; G: obinutuzumab; mono: monother- apy; FC: fludarabine-cyclophosphamide; Clb: chlorambucil; benda: bendamustine; n: number; h: hour. Patients within each cohort could have received any of the permitted immunochemotherapy regimens: G-mono (Cohort 1, n=15; Cohort 2, n=25; Cohort 3, n=20), G-FC (Cohort 1, n=61; Cohort 2, n=57; Cohort 3, n=33), G-Clb (Cohort 1, n=12; Cohort 2, n=40; Cohort 3, n=16) or G-benda (Cohort 1, n=149; Cohort 2, n=106; Cohort 3, n=82). *Sixteen previously untreated patients from the safety population were excluded from the cohort analysis as they did not receive treatment as planned (n=15) or were not assigned to any cohort (n=1). †Cycle 1 day 1 dose of obinutuzumab over two days: 25 mg (12.5 mg/h) + 975 mg (50-400 mg/h). ‡Cycle 1 day 1 dose of obinutuzumab over two 2 days: 100 mg (25 mg/h) + 900 mg (50-400 mg/h) with oral dexamethasone 20 mg (or equivalent) 12 h pre-dose. §Cycle 1 day 1 dose of obinutuzumab over two days: doses and infusion rates as in Cohort 1 with pre-medication scheme as in Cohort 2.
well as patients who were only ever planned to receive single-agent obinutuzumab. As such, patients in this sub- group had a higher rate of AEs and discontinuations due to AEs than would be expected for patients treated with G-mono, based on previous single-agent studies.4,5
The safety data from GREEN were generally in line with the safety profile for obinutuzumab-based immunochemotherapy previously observed in patients treated for CLL1-7 and non-Hodgkin lymphoma.13-18 Common AEs included IRRs (typically mild or moderate events observed almost exclusively during the first obinu- tuzumab infusion), infections and hematologic toxicities. The higher frequency of grade ≥3 AEs (including infec- tions) and SAEs compared with the pivotal CLL11 study (which enrolled first-line patients with co-existing condi- tions2,3) likely reflects the broader patient population, and inclusion of more heavily pre-treated R/R patients. As expected, R/R patients in GREEN experienced more AEs and more deaths due to AEs or disease progression com-
pared with first-line patients. While the rate of deaths due to AEs, particularly infections/sepsis, in first-line patients was higher than expected, it is reflective of that seen in clinical practice (rather than in classical clinical trials), where a broad range of patients and difficult-to-treat infections are also encountered. Predictably, there was a higher rate of SAEs and fatal AEs in first-line unfit versus fit patients; an observation that may have been due to the general health of the patients rather than the treatment regimen(s) received.
The high reported rates of AESIs/AEPIs, including neu- tropenia, thrombocytopenia, IRRs, infections and TLS, may have resulted from the inclusion of R/R and unfit patients who may be more vulnerable to the adverse effects of treatment, although this did not appear to markedly affect grade ≥3 AESI/AEPI rates. Furthermore, despite the additional risk minimization measures, the rate of IRRs, including TLS, remained relatively high, par- ticularly in Cohort 3. During the initial stages of recruit-
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Table 5. Summary of response at the final response assessment according to treatment (intent-to-treat population).
All patients (N=972) First-line, % (95% CI)
ORR
CR (including CRi) R/R, % (95% CI)
ORR
CR (including CRi)
Patients with 17p deletion* (n=80)
First-line, n/N (%) ORR
CR (including CRi) R/R, n/N (%)
ORR
CR (including CRi)
G-mono (n=127)
63.5 (50.4-75.3) 20.6
42.2 (29.9-55.2) 4.7
1/2 (50.0) 0/2
2/6 (33.3)
0/6
G-FC (n=193)
89.5 (83.6-93.9) 46.4
82.5 (67.2-92.7) 22.5
1/5 (20.0) 1/5 (20.0)
5/6 (83.3)
0/6
G-Clb (n=114)
82.4 (71.2-90.5) 16.2
54.3 (39.0-69.1) 6.5
5/7 (71.4) 1/7 (14.3)
5/7 (71.4)
0/7
G-benda (n=538)
81.8 (77.4-85.8) 35.7
72.8 (65.9-79.0) 19.9
12/20 (60.0) 5/20 (25.0)
12/27 (44.4)
3/27 (11.1)
n/N: number; G: obinutuzumab; mono: monotherapy; FC: fludarabine-cyclophosphamide; Clb: chlorambucil; benda: bendamustine; CI: confidence interval; ORR: overall response rate; CR: complete response; CRi: complete response with incomplete marrow recovery; R/R: relapsed refractory. *17p deletion status was determined by fluorescence in situ hybridization.
ment into Cohort 3, up-dated and expanded definitions of patients at risk of TLS and additional TLS risk mitigation measures (for patients treated with G-benda) were implemented. Nonetheless, the TLS rate in GREEN, including 2 fatal cases, highlights the need for careful risk assessment, prophylaxis and monitoring, particularly in unfit patients [with a CIRS score of >6 and/or reduced renal function (CrCl <70 mL/min)] treated with the G- benda regimen, in whom a high incidence of TLS (14.4%) was observed. It should be noted that, because of the non- randomized study design, it is impossible to conclude whether the increase in TLS seen in G-benda-treated patients in this trial was due to the chemotherapy partner or to differences in patients’ characteristics compared with the other treatment cohorts. The current labeling states that any patients with a high tumor burden, high circulat- ing lymphocyte count (>25x109/L) or renal impairment, who are considered at greater risk for TLS, should receive appropriate TLS prophylaxis with anti-hyperuricemics (e.g. allopurinol or rasburicase) and hydration prior to obinutuzumab infusion.8,9 Pre-treatment should then be followed by intensive monitoring of clinical signs/symp- toms and laboratory parameters during the first few days of treatment. For IRRs, it is recommended that patients are pre-medicated with an intravenous corticosteroid, acetaminophen and antihistamine, and then monitored closely during obinutuzumab infusion.8,9 Antimicrobial prophylaxis is advised for patients with prolonged severe neutropenia to prevent infection; granulocyte colony- stimulating factors should be considered in case of grade ≥3 neutropenia.
All four obinutuzumab-based immunochemotherapy regimens appeared manageable in both first-line (fit or unfit) and R/R patients with CLL. G-FC, which was the most intensive regimen, was associated with a high rate of grade ≥3 neutropenia, but this did not translate into an ele- vated incidence of infection; an observation that may be explained by the underlying fitness of patients who received G-FC. Fitness may also explain the low rate of
deaths due to AEs in G-FC-treated patients.
Investigation of strategies to prevent or mitigate IRRs
during the first infusion of obinutuzumab was inconclu- sive, with rates comparable to those reported for G-Clb in CLL11 (grade ≥3, 21%).2 Despite efforts to minimize IRRs using approaches whereby the dosage of obinutuzumab was modified, the infusion rate slowed and/or additional corticosteroid was given as pre-medication, no one strategy appeared better than another. A recent nursing review of all IRR data from GREEN and CLL11 concluded that IRRs observed with obinutuzumab during the first infusion are generally manageable in CLL patients through treatment interruptions, but management could be improved considerably with extra vigilance during the first infusion.19
Analysis of anti-leukemic activity revealed high response rates across all settings and regimens, thus sup- porting findings from previous studies, including CLL11 and phase I/II trials, which have evaluated the G-Clb, G-FC, G-benda and G-mono regimens.1-7 Response rates tended to be higher in first-line versus R/R patients, and in patients who received combination versus single-agent obinutuzumab therapy. The response rates also compared favorably with those reported for rituximab-containing immunochemotherapy (rituximab plus Clb, benda or FC) in CLL.2,3,20-24 While longer-term data are required to con- firm the efficacy of obinutuzumab-based therapy in GREEN, they do suggest that these regimens are clinically active and associated with a generally manageable toxicity profile.
In conclusion, in the largest obinutuzumab patient cohort analyzed to date, the GREEN primary safety data were in line with the safety and tolerability profile previ- ously observed in patients receiving obinutuzumab-based treatment for CLL. Toxicities were generally manageable and response rates were encouraging in this broad popu- lation of CLL patients, including previously untreated, fit and unfit patients and those with R/R disease. Based on these data, future trials are warranted.
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Acknowledgments
The authors would like to thank the patients and their fami- lies, and the GREEN study investigators and site staff. They would also like to acknowledge Miriam Amor for her valuable contribution to the statistical analyses. Third-party medical
writing assistance, under the direction of the authors, was pro- vided by Cheryl Wright, PhD of Gardiner-Caldwell Communications (Macclesfield, UK), and was funded by F. Hoffmann-La Roche Ltd. GREEN was sponsored by F. Hoffmann-La Roche Ltd.
References
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7. Danilov A, Yimer H, Boxer M, et al. Results of a phase II multicenter study of obinu- tuzumab plus bendamustine in pts with previously untreated chronic lymphocytic leukemia (CLL). Haematologica. 2017;102:71 [abstract P249].
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13. Sehn LH, Chua N, Mayer J, et al. Obinutuzumab plus bendamustine versus bendamustine monotherapy in patients with rituximab-refractory indolent non- Hodgkin lymphoma (GADOLIN): a ran- domised, controlled, open-label, multicen- tre, phase 3 trial. Lancet Oncol. 2016;17(8):1081-1093.
14. Sehn LH, Goy A, Offner FC, et al. Randomized phase II trial comparing obin- utuzumab (GA101) with rituximab in patients with relapsed CD20+ indolent B- cell non-Hodgkin lymphoma: final analysis of the GAUSS study. J Clin Oncol. 2015;33(30):3467-3474.
15. Salles GA, Morschhauser F, Solal-Céligny P, et al. Obinutuzumab (GA101) in patients with relapsed/refractory indolent non- Hodgkin lymphoma: results from the phase II GAUGUIN study. J Clin Oncol. 2013; 31(23):2920-2926.
16. Morschhauser FA, Cartron G, Thieblemont C, et al. Obinutuzumab (GA101) monotherapy in relapsed/refractory diffuse large B-cell lymphoma or mantle-cell lym- phoma: results from the phase II GAU- GUIN study. J Clin Oncol. 2013; 31(23):2912-2919.
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Obinutuzumab (GA101) plus CHOP or FC in relapsed/refractory follicular lymphoma: results of the GAUDI study (BO21000). Blood. 2013;122(7):1137-1143.
18. Marcus R, Davies A, Ando K, et al. Obinutuzumab for the first-line treatment of follicular lymphoma. N Engl J Med. 2017;377(14):1331-1334.
19. Dawson K, Moran M, Guindon K, Wan H. Managing infusion-related reactions for patients with chronic lymphocytic leukemia receiving obinutuzumab. Clin J Oncol Nurs. 2016;20(2):E41-E48.
20. Eichhorst B, Fink AM, Bahlo J, et al. International group of investigators; German CLL Study Group (GCLLSG). First-line chemoimmunotherapy with ben- damustine and rituximab versus fludara- bine, cyclophosphamide, and rituximab in patients with advanced chronic lymphocytic leukaemia (CLL10): an inter- national, open-label, randomised, phase 3, non-inferiority trial. Lancet Oncol. 2016;17(7):928-942.
21. Fischer K, Bahlo J, Fink AM, et al. Long- term remissions after FCR chemoim- munotherapy in previously untreated patients with CLL: updated results of the CLL8 trial. Blood. 2016;127(2):208-215.
22. Skarbnik AP, Faderl S. The role of com- bined fludarabine, cyclophosphamide and rituximab chemoimmunotherapy in chron- ic lymphocytic leukemia: current evidence and controversies. Ther Adv Hematol. 2017;8(3):99-105.
23. Hallek M, Fischer K, Fingerle-Rowson G, et al. Addition of rituximab to fludarabine and cyclophosphamide in patients with chronic lymphocytic leukaemia: a randomized, open-label, phase 3 trial. Lancet. 2010; 376(9747):1164-1174.
24. Nunes AA, da Silva AS, Souza KM, Koury Cde N, de Mello LM. Rituximab, fludara- bine, and cyclophosphamide versus fludarabine and cyclophosphamide for treatment of chronic lymphocytic leukemia: a systematic review with meta- analysis. Crit Rev Oncol Hematol. 2015; 94(3):261-269.
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Inferior survival in high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements is not associated with MYC/IG gene rearrangements
Ellen D. McPhail,1 Matthew J. Maurer,2 William R. Macon,1 Andrew L. Feldman,1 Paul J. Kurtin,1 Rhett P. Ketterling,1 Rakhee Vaidya,3 James R. Cerhan,4 Stephen M. Ansell,5 Luis F. Porrata,5 Grzegorz S. Nowakowski,5 Thomas E. Witzig1,5 and Thomas M. Habermann5
1Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; 2Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN; 3Department of Hematology and Oncology, Wake Forest Baptist Health, Winston-Salem, NC; 4Department of Health Sciences Research, Mayo Clinic, Rochester, MN and 5Division of Hematology, Mayo Clinic, Rochester, MN, USA
ABSTRACT
High-grade B-cell lymphomas with MYC and BCL2 and/or BCL6 rearrangements (double-/triple-hit lymphoma) have an aggres- sive clinical course. We investigated the prognostic value of transformation from low-grade lymphoma, cytological features (high grade versus large cell), MYC rearrangement partners (immunoglobu- lin versus nonimmunoglobulin gene), and treatment. We evaluated 100 adults with double-/triple-hit lymphoma, reviewing cytological fea- tures; cell of origin; and rearrangements of MYC, BCL2, and BCL6 using MYC, BCL2, and BCL6 break-apart and IGH/MYC, IGL/MYC, IGK/MYC, and IGH/BCL2 dual-fusion interphase fluorescence in situ hybridization probes. Outcome analysis was restricted to patients with lymphoma, de novo or at transformation, who received anthracy- cline-based chemotherapy. Among them, 60% had high-grade cyto- logical features; 91% had a germinal center B-cell phenotype, and 60% had a MYC/IG rearrangement. Germinal center B-cell phenotype was associated with BCL2 rearrangements (P<0.001). Mean (95% con- fidence interval) 5-year overall survival was 49% (37%-64%). Transformation from previously treated and untreated low-grade lym- phoma was associated with inferior overall survival (hazard ratio, 2.99; P=0.008). Patients with high-grade cytological features showed a non-significant tendency to inferior outcome (hazard ratio, 2.32; P=0.09). No association was observed between MYC rearrangement partner and overall survival (hazard ratio, 1.00; P=0.99). Compared with patients receiving rituximab, cyclophosphamide, doxorubicin, and vincristine (R-CHOP) and dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab (EPOCH- R), patients receiving rituximab, cyclophosphamide, vincristine, dox- orubicin, methotrexate/ifosfamide, etoposide, and cytarabine (R- CODOX-M/IVAC) had a non-significant tendency to better overall survival (hazard ratio, 0.37; P=0.10). In conclusion, high-grade B-cell lymphomas with MYC and BCL2 and/or BCL6 rearrangements had heterogeneous outcomes and MYC/IG rearrangements were not asso- ciated with inferior overall survival.
Introduction
The diagnosis of ‘high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements’ (double-/triple-hit lymphoma, DH/THL) was established in the 2016 revision of the World Health Organization (WHO) classification of lym- phoid neoplasms.1 This category includes all large B-cell lymphomas with
Ferrata Storti Foundation
Haematologica 2018 Volume 103(11):1899-1907
Presented as an abstract and poster at the American Society of Hematology 58th Annual Meeting and Exposition, San Diego, California, USA, December 3-6, 2016.
Correspondence:
mcphail.ellen@mayo.edu
Received: February 7, 2018. Accepted: June 12, 2018. Pre-published: June 14, 2018.
doi:10.3324/haematol.2018.190157
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1899
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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rearrangements of MYC and BCL2 or BCL6, or both, besides those that meet criteria for follicular or lym- phoblastic lymphoma. It encompasses some cases previ- ously called ‘B-cell lymphoma, unclassifiable, with fea- tures intermediate between diffuse large B-cell lym- phoma (DLBCL) and Burkitt lymphoma (BL) (BCLU)’, in accordance with the 2008 WHO classification.2 These cases were considered clinically aggressive but were diffi- cult to diagnose because of vague diagnostic criteria.
By morphological evaluation, DH/THL may show a cytological spectrum. The spectrum can range from (i) monotonous medium-sized cells with round nuclei, fine- ly dispersed chromatin, and starry sky appearance, resembling BL, to (ii) intermediate-sized cells with slight pleomorphism and slightly irregular nuclear contours, resembling BCLU,2 to (iii) large lymphoid cells with round to irregular nuclear contours, variably sized nucleoli, and varying amounts of cytoplasm, resembling DLBCL. Experts have recommended that during evaluation, details of the morphological appearance be added in a comment to the record because of the potential prognos- tic importance of morphological characteristics.1 Yet, few studies have specifically addressed morphological appear- ance as a prognostic indicator.
MYC is a powerful transcriptional factor that helps to drive the cell from G0/1 phase to S phase and promotes cell proliferation and growth, DNA replication, and protein biosynthesis. It was identified initially as the molecular target of the 8q24 rearrangement characteristic of BL but was subsequently identified in various B-cell lymphomas, including 5% to 15% of DLBCL and 30% to 60% of high- grade B-cell lymphomas.3-5 The MYC rearrangement part- ner in BL is almost invariably an immunoglobulin (IG) gene (IGH, IGK, or IGL), whereas in DLBCL and high- grade B-cell lymphoma it is a non-IG gene in about 40% of cases.5-9 Common non-IG MYC partners include lym- phomagenesis-related genes, such as BCL6, BCL11A, PAX5, and IKAROS.10 In IG/MYC rearrangements, MYC is juxtaposed to an IG enhancer, usually resulting in pro- nounced amplification of MYC protein expression, whereas MYC expression and MYC transcript levels are often less robust in the clinical setting of non-IG/MYC rearrangements.5,9 The prognostic significance of the MYC partner gene is controversial. Some groups found that a non-IG MYC partner was a survival advantage,5,6,8 while other groups observed no significant difference between IG and non-IG partner cases.9,11
DH/THL was established as a new diagnostic category in part because of its aggressive clinical behavior. However, most DH/THL cases have a BCL2 rearrange- ment (i.e., MYC/BCL2 or MYC/BCL2/BCL6). The clinical behavior of those lacking the BCL2 rearrangement (i.e., MYC/BCL6 cases) is not well understood because a limit- ed number are available for analysis. At present, the prog- nostic significance of MYC/BCL6 in this context is con- troversial, with different groups identifying superior out- come,5,12 no difference in outcome,13 or inferior out- come.9,14,15 However, fewer than 100 cases have been described in the literature.
The reported median overall survival (OS) for DH/THL in different series range from 4.5 to 34 months.6,10,13,16-26 Patients were treated primarily with rituximab, cyclophosphamide, doxorubicin, and vincristine (R- CHOP)27; dose-adjusted etoposide, prednisone, vin- cristine, cyclophosphamide, doxorubicin, and rituximab
(EPOCH-R)28; rituximab, cyclophosphamide, vincristine, doxorubicin, and dexamethasone (R-hyper CVAD); methotrexate; cytarabine25; and rituximab, cyclophos- phamide, vincristine, doxorubicin, and methotrexate/rit- uximab, ifosfamide, etoposide, and cytarabine (R- CODOX-M/IVAC)29 with or without an autologous stem cell transplant in first complete remission. The median progression-free survival and OS were not improved in some series,13,23,25 but were improved in one series.30 Autologous stem cell transplantation in the relapse setting is associated with poor outcomes.31-33 Few studies have addressed the prognostic significance of transformation of low-grade lymphoma to DH/THL.34
In the light of the controversy surrounding these issues, the present study investigated the prognostic significance of several of these parameters, including morphological evaluation, IG/MYC versus non-IG rearrangement part- ner, presence or absence of a BCL2 rearrangement, trans- formation from low-grade lymphoma, and therapeutic regimens in diagnostic cases of DH/THL at the Mayo Clinic in Rochester, Minnesota. To our knowledge, this study represents the largest single-institution study of these characteristics among contemporary DH/THL patients.
Methods
The Mayo Clinic Institutional Review Board approved this study and all patients provided consent. Strengthening the Reporting of Observational Studies in Epidemiology reporting guidelines were followed. Cases were identified through review of Mayo Clinic patients in the Mayo Clinic Lymphoma Database (1998-2015) and the Lymphoma Specialized Program of Research Excellence Molecular Epidemiology Resource (2002- 2015). Five cases were identified from the Molecular Epidemiology Resource through fluorescence in situ hybridiza- tion (FISH) performed for other studies.35 The therapeutic regi- mens were R-CHOP, dose-adjusted EPOCH-R, R-CODOX- M/IVAC, R-hyper-CVAD, methotrexate, cytarabine, and non– anthracycline-based treatment. Additional information regard- ing case identification and case criteria is detailed in the Online Supplementary Appendix.
All cases were diagnosed initially by a Mayo Clinic hematopathologist as either DLBCL or BCLU according to the 2008 WHO criteria;2 all were reclassified as DH/THL according to the 2016 WHO criteria.1 Morphological re-review to assess high-grade versus large-cell histological characteristics was per- formed by four Mayo Clinic hematopathologists (ALF, PJK, WRM, and EDM). Definitions of high-grade and large-cell cyto- logical features are detailed in the Online Supplementary Appendix. For outcome analysis, only cases with a consensus re- review diagnosis were used.
Cell of origin was determined according to the Hans classifier.36 Immunohistochemical methods and criteria are detailed in the Online Supplementary Appendix. Interphase FISH was performed on either paraffin sections of tissue specimens or smears of bone marrow aspirate specimens according to previ- ously described methods37,38 using break-apart probes for MYC and BCL6; dual-fusion FISH probes for IGH/MYC, IGL/MYC, and IGK/MYC; and either a BCL2 break-apart probe or an IGH/BCL2 dual-fusion FISH probe. Further details are provided in the Online Supplementary Appendix. Because of tissue limita- tions, not all probe sets were performed in all cases. Specifically, in some cases, the MYC rearrangement partner could not be
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identified, and in other cases, the BCL6 rearrangement status was unknown. Cases with concurrent MYC and BCL2 rearrangements, concurrent MYC and BCL6 rearrangements, and concurrent MYC, BCL2, and BCL6 rearrangements are referred to as MYC/BCL2, MYC/BCL6, and MYC/BCL2/BCL6, respectively.
Clinical outcome analysis was limited to patients with DH/THL characteristics identified at initial diagnosis or at trans- formation from previously diagnosed low-grade lymphoma and who received an anthracycline-based chemotherapy regimen at DH/THL diagnosis. Previous therapies for the 11 patients with prior low-grade lymphoma are as follows: none (n=2); radiation therapy only (n=2); bendamustine and rituximab (B-R) only (n=2); single-agent rituximab (n=1); B-R followed by ibritu- momab consolidation (n=1); R-CHOP with maintenance ritux- imab (n=1); seven prior therapies, including rituximab, cyclophosphamide, vincristine, and prednisone (R-CVP), CHOP, ifosfamide, carboplatin, and etoposide (ICE), and B-R (n=1); and four prior therapies, including R-CVP and B-R (n=1). Patients with recurrent B-cell lymphoma with high-grade or large-cell histological features were excluded from this analysis because the MYC/BCL2/BCL6 rearrangement status of the initial biopsy was unknown.
OS was defined as the time from DH/THL diagnosis to death of any cause or to last follow-up. Event-free survival (EFS) was defined as the time from diagnosis to progression, relapse, re- treatment after initial chemotherapy, or death of any cause. EFS12 was defined as event-free status at 12 months after diag- nosis. EFS12 was used as an endpoint because of limited follow- up and because progression or relapse occurred primarily in the first 12 months after diagnosis.39 OS and EFS were evaluated with Kaplan-Meier curves and Cox proportional hazards mod- els. All analyses were performed using statistical software (SAS version 9.4; SAS Institute Inc.) and R 3.3.1 (R Project for Statistical Computing). Statistical significance was defined by P values less than 0.05.
Results
Morphological and tumor characteristics
The study involved 100 patients (male to female ratio, 64:36) with the median (range) age at DH/THL diagnosis of 61 (29-87) years. Sixty-seven patients had DH/THL identified at initial diagnosis; 22, at the time of transfor- mation of previously diagnosed low-grade lymphoma; and 11, from a recurrent specimen in previously diag- nosed lymphoma with large-cell or high-grade morpho- logical features for which original diagnostic material was not studied (Table 1). Slides were available for consensus review in 72 cases, and in 65 cases a consensus diagnosis was reached. Of these, 39 patients (60%) had high-grade morphological features (Figure 1A) and 26 (40%) had large-cell morphological features (Figure 1B). According to the Hans classifier, the phenotype of 91 cases (91%) was germinal center B-cell (GCB); six (6%), non-GCB; and three (3%), unknown. In immunohistochemistry analysis, 37 of 43 cases (86%) met criteria for MYC posi- tivity, 76 of 84 (90%) expressed BCL2, and 30 of 37 (81%) expressed both (called double expressers).
MYC rearrangement partner (IG versus non-IG gene) and BCL2/BCL6 rearrangement status
The MYC rearrangement partner was an IG gene in 52 cases (39 IGH, 6 IGK, and 7 IGL), a non-IG gene in 35
cases, and unknown in 13 cases (Figure 2A). Fifty-nine cases were MYC/BCL2; 13, MYC/BCL6; 20, MYC/BCL2/BCL6; and 8, MYC/BCL2 (unknown BCL6) (Figure 2B). The MYC rearrangement partner (IG versus non-IG gene) was not associated with morphological fea- tures (P=0.96), cell of origin (P=0.18), or BCL2 rearrange- ment status (P=0.27) (Table 2). However, MYC expres- sion by immunohistochemistry was significantly more common in IG/MYC than in non-IG/MYC cases (95% versus 74%; P=0.049). GCB phenotype was present in 100% of the 85 cases with BCL2 rearrangements [MYC/BCL2, MYC/BCL2/BCL6, and MYC/BCL2 (unknown BCL6); collectively referred to as DH- BCL2/THL], and in six (50%) of the 12 MYC/BCL6 cases
Table 1. Clinicopathological features, genetic characteristics, and ther- apeutic regimens of all patients compared with those of the outcome analysis cohort.
Variable
All patientsa (n=100)
47 (47) 53 (53)
64 (64)
36 (36)
67 (67) 22 (22) 11 (11)
(n=65) 26 (40) 39 (60)
(n=97) 91 (94) 6 (6)
(n=43) 37 (86) 6 (14) 20-90 70
Outcome analysis cohorta (n=70)
34 (49) 36 (51)
41 (59)
29 (41)
59 (84) 11 (16) 0 (0)
(n=43) 19 (43) 24 (56)
(n=69) 64 (93) 5 (7)
(n=29) 26 (90) 3 (10) 0-90 50
(n=61) 35 (57) 26 (43)
39 (56) 11 (16) 14 (20) 6 (9)
32 (46) 17 (24) 15 (21) 6 (9)
0 (0)
0 (0)
Age, years <60
≥60
Sex Male Female
Timing of diagnosis
De novo
Transformation Recurrence
Morphologic review, central Large cell
High grade
COO per Hans classifier GCB
Non-GCB
MYC immunohistochemistry Positive
Negative
% MYC+, range
% MYC+, median
MYC FISH: rearrangement partner(n=87) IG gene 52 (60) Non-IG gene 35 (40)
BCL2 and BCL6 FISH: rearrangement status
MYC/BCL2
MYC/BCL6
MYC/BCL2/BCL6
MYC/BCL2 (BCL6 unknown)
Therapy
R-CHOP
R-EPOCH R-CODOX-M/IVAC R-hyper-CVAD Platinum-based salvage Other/none/unavailable
59 (59) 13 (13) 20 (20) 8 (8)
36 (36) 17 (17) 17 (17) 6 (6) 10 (10) 14 (14)
COO: cell of origin; FISH: fluorescence in situ hybridization; GCB: germinal center B cell; IG: immunoglobulin; hyper-CVAD: cyclophosphamide, vincristine: doxorubicin, and dexamethasone; R-CHOP: rituximab, cyclophosphamide, doxorubicin, and vin- cristine; R-CODOX-M/IVAC: rituximab, cyclophosphamide, vincristine, doxorubicin, and high-dose methotrexate alternating with rituximab, ifosfamide, etoposide, and high-dose cytarabine; R-EPOCH: rituximab, etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin. aValues are presented as number (%) of patients unless specified otherwise.
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(P<0.001). All 13 MYC/BCL6 cases were de novo diag- noses, whereas 38% of DH-BCL2/THL cases were either transformed (n=22) or relapsed (n=11) (P=0.03). No asso- ciation was observed between morphological features and BCL2 rearrangement status (P=0.16).
Therapy, clinical characteristics, and outcome
The therapeutic regimens were R-CHOP (n=36); dose- adjusted EPOCH-R (n=17); R-CODOX-M/IVAC (n=17); R-hyper-CVAD, methotrexate, and cytarabine (n=6); plat- inum-based salvage (n=10); and non-anthracycline-based treatment (n=14). Survival was analyzed for 70 patients receiving anthracycline-based curative-intent therapy at diagnosis of DH/THL (Table 1). The median (interquartile range) age of these patients was 61 (29-82) years; 41 (59%) were males. Fifty-nine patients had de novo DH/THL and 11 had transformation of a previously diag- nosed low-grade lymphoma. For treatment, 32 patients
received R-CHOP; 17, dose-adjusted EPOCH-R; 15, R- CODOX-M/IVAC; and 6, R-hyper-CVAD with methotrexate and cytarabine. Twelve patients (17%) received consolidation with autologous stem cell trans- plantation. At a median (range) follow-up of 21 (1-87) months, EFS12 was 46% (Figure 3A) and median OS was 22 months (95% CI: 13 months - unreached) (Figure 3B). At a 5-year follow-up, the OS rate was 49% (95% CI: 37%-64%).
Patients with DH/THL at transformation of previously diagnosed low-grade lymphoma (n=11) had poor out- comes [median OS, 10.8 months; hazard ratio (HR), 2.99; 95% CI: 1.33-6.71; EFS12, 10%] - inferior to the out- comes of patients with de novo DH/THL (median OS, 22 months; P=0.008; EFS12, 52%) (Figure 4A). However, seven of the 11 patients had received prior immunochemotherapy for their low-grade lymphoma. Patients with high-grade morphological features on a con-
A
AB
Figure 1. Comparison of high- grade and large-cell cytologic characteristics. (A) Double- hit/triple-hit lymphoma (DH/THL) with a high-grade morphological pattern (hematoxylin-eosin, origi- nal magnification ×400). (B) DH/THL with large-cell morpholog- ical characteristics (hematoxylin- eosin, original magnification ×400).
Figure 2. MYC rearrangement partners and BCL2 and BCL6 rearrangement status. (A) MYC rearrangement partners in dou- ble-hit/triple-hit lymphoma (DH/THL) by interphase dual- fusion fluorescence in situ hybridization (FISH). Cases with an IG/MYC rearrangement (IGH/MYC, IGK/MYC, or IGL/MYC) are contiguous. (B) BCL2 and BCL6 rearrangement status in DH/THL by interphase FISH. All cases had a MYC rearrangement. BCL2-rearranged cases are con- tiguous whereas MYC/BCL6 cases are not contiguous.
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sensus pathology review (n=24) showed a nonsignificant tendency to inferior outcome (median OS, 13.5 months; HR, 2.32; 95% CI: 0.88-6.12; EFS12, 37%) compared with that of patients with large-cell morphological features (n=19) (median OS, unreached; P=0.09; EFS12, 57%) (Figure 4B). Patients with MYC/BCL6 (BCL2 rearrange- ment-negative) tumors showed a nonsignificant tendency to better outcomes (n=11) (median OS, unreached; HR, 0.42; 95% CI: 0.13-1.40; EFS12, 64%) than those of patients with BCL2 rearrangement (DH-BCL2/THL; n=59; median OS, 21.7 months; P=0.16; EFS12, 42%) (Figure 4C). There was no association between MYC partner (IG gene versus non-IG gene) and OS (for IG, HR, 1.00; 95% CI: 0.48-2.09; P=0.99) (Figure 4D).
Compared with patients receiving all other therapies, patients treated with R-CODOX-M/IVAC had superior EFS12 (72% versus 39%, P=0.04) and showed a nonsignif- icant tendency to improved OS (HR, 0.37; 95% CI, 0.11- 1.23; P=0.10) (Figure 5). However, patient selection bias may confound this outcome because the patients were significantly younger (P<0.001) than the patients who received other anthracycline-based regimens. Nevertheless, outcomes stayed consistent although not significant for EFS12 (HR, 0.27; 95% CI: 0.07-1.16; P=0.08) and for OS (HR, 0.40; 95% CI: 0.11-1.51; P=0.18), after adjustment for age in multivariable logistic and Cox models, respectively.
Discussion
The diagnosis of ‘high-grade B-cell lymphoma, with MYC and BCL2 and/or BCL6 rearrangements’ (DH/THL) was established in the 2016 revision of the WHO classifi- cation of lymphoid neoplasms, in part to acknowledge the prognostic significance of the MYC and BCL2 or MYC and BCL6 rearrangements, or both, in B-cell lym- phomas with large-cell or high-grade morphological fea- tures. However, our study shows that within this umbrel-
la category, several subgroups have distinctive features and varying clinical outcomes. Strengths of this single- institution study include thorough pathology review, comprehensive analyses of genetic features and cell of origin, and availability of key clinical, treatment, and out- come data. The main limitations of this retrospective study include missing MYC rearrangement data for some cases, potential for selection bias in treatment choice given to the patient, inclusion of cases over an 11-year time frame during which clinical management evolved rapidly, and small sample size for some analyses. Although there is likely some bias toward selection of cases with high-grade cytological features in the early specimens, this bias should not have been present in the 57 cases that were identified after our institution began performing interphase FISH to identify DH/THL in all B- cell lymphomas with either large-cell or high-grade histo- logical features. Of the specimens with histological con- sensus re-review, 16/20 (80%) of the early cases but only 23/45 (51%) of the later cases had a morphological diag- nosis of high-grade B-cell lymphoma, suggesting that the selection bias present in the early cases had been mitigat- ed in the later group.
Our data suggest several important observations. First, patients with DH/THL at transformation of previously diagnosed low-grade lymphoma had a dismal outcome with a median OS of 10.8 months and EFS12 of 10%. In light of the small number of cases and potential con- founding effect of the prior immunochemotherapy for some patients, this observation should be interpreted with caution. However, it raises an interesting biological question that may warrant investigation in future studies. Few previous studies have addressed this, although a report of two cases of transformation of low-grade follic- ular lymphoma to DH/THL described an aggressive clini- cal course.34 In DH/THL, induction failure occurs early and is worse among patients aged 60 years or older. Nevertheless, the OS for the entire cohort at 5 years was 49%, suggestive of long-term cure in a subset of patients.
Table 2. Correlations between clinicopathological and genetic characteristics in de novo, transformed, and recurrent double-hit/triple-hit lymphoma.a
Morphological evaluation
Cell of origin
MYC
Double BCL2 expresserb
All High Large
Characteristic patients grade cell GCB Non-GCB IGgene gene Rearranged Rearranged Yes No
All patients
Timing of diagnosis
De novo
Transformed
Recurrent
Morphological evaluation High grade
Large cell
Cell of origin GCB
Non-GCB
MYC partner IG gene Non-IG gene
BCL2
Rearranged
Not rearranged
67 (67) 22 (22) 11 (11)
39 (60) 26 (40)
91 (94)
6 (6)
52 (60) 35 (40)
39 (60)
20 (51) 10 (63) 9 (90)
26 (40)
19 (49) 6 (38) 1 (10)d
91 (94)
59 (91) 21 (100) 11 (100)
36 (95) 22 (88)
6 (6)
6 (9) 0 (0)c 0 (0)
2 (5) 3 (12)
52 (60)
34 (60) 12 (60) 6 (60)
20 (53) 13 (52)
48 (62)
2 (33)
35 (40)
23 (40) 8 (40) 4 (40)
18 (48) 12 (48)
30 (38)
4 (67)
87 (87)
54 (81) 22 (100) 11 (100)
35 (90) 20 (77)
85 (93)
0 (0)
46 (88) 28 (80)
Not
13 (13)
13 (19) 0 (0)c 0 (0)
4 (10) 6 (23)
6 (7)
6 (100)e
4 (12) 7 (20)
30 (81)
20 (87) 8 (73) 2 (67)
16 (80) 10 (83)
28 (82)
2 (67)
18 (84) 12 (75)
28 (85)
2 (50)
7 (19)
3 (13) 3 (27) 1 (33)
4 (20) 2 (17)
6 (18)
1 (33)
3 (16) 4 (25)
5 (15)
2 (50)
partner Non-IG
GCB:germinalcenterBcell;IG:immunoglobulin.aValuesarepresentedasnumber(%)ofpatients. bExpressionofbothMYCandBCL2.cP=0.01to<0.05.dP=0.05to0.10.eP≤0.001.
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Of note, progression or relapse occurred almost exclu- sively within 12 months of diagnosis, suggesting that EFS12 is worth further evaluation as an endpoint for stud- ies of DH/THL.39
Treatment with R-CODOX-M/IVAC may result in superior outcomes for patients younger than 60 years, despite the preponderance of aggressive (high-grade) his- tological findings within this group. However, selection bias may also have an important role in the superior out- comes for this cohort. A multicenter retrospective analy- sis evaluated effect of induction regimen and stem cell transplantation on outcomes in DHL, showing that inten- sive induction therapy was not associated with improved OS.13 In a meta-analysis of 11 studies and 394 patients, OS was not different across the treatment approaches used in our series.40 Sun et al. reported a 2-year progres-
AB
sion-free survival rate of 60% and a 2-year OS rate of 82% for 16 patients treated with R-CODOX-M/IVAC followed by hematopoietic stem cell transplantation.30 No randomized clinical trial for this histological subset is cur- rently available.
Second, DH/THL patients with high-grade histological characteristics showed a tendency, although not statisti- cally significant, toward a more aggressive clinical course. Published literature has provided mixed results on this issue. Johnson et al., in their retrospective study of BCLU and DLBCL with concurrent MYC and BCL2 rearrange- ments identified through karyotypic analysis, showed that BCLU morphological appearance was associated with poorer outcome (P<0.001).6 Other investigators have obtained similar results.40-42 Blastoid morphological char- acteristics have also been associated with adverse clinical
AB
Figure 3. Event-free survival and overall survival of patients receiv- ing anthracycline-based therapy. (A) Event-free survival of the 70 patients receiving anthracycline- based therapy at the time of diag- nosis of double-hit/triple-hit lym- phoma. (B) Overall survival of the 70 patients.
Figure 4. Overall survival according to transformation of previously diagnosed low-grade lymphoma, morphological characteristics, BCL2 rearrangement status, and MYC partner (IG gene versus non-IG gene). (A) Patients with double- hit/triple-hit lymphoma (DH/THL) at transformation of previously diag- nosed low-grade lymphoma had inferior overall survival (OS) com- pared with patients who had de novo DH/THL [hazard ratio (HR) 2.99, P=0.007)]. (B) DH/THL patients with high-grade morpholog- ical characteristics showed a ten- dency toward inferior OS compared with patients with large-cell mor- phological characteristics, but it was not statistically significant (HR 2.32, P=0.09). (C) DH/THL patients with BCL2 rearrangements [MYC/BCL2, MYC/BCL2/BCL6, and MYC/BCL2 (BCL6 unknown)], so- called DH-BCL2/TH, showed a non- significant tendency toward inferior OS compared with those who did not have BCL2 rearrangements (MYC/BCL6) (HR 2.44, P=0.16). (D) No association was observed between MYC partner (IG versus non-IG) and OS (P=0.99).
CD
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outcome.43 In contrast, Petrich et al., in their retrospective study of 311 DH/THL patients, reported that histological appearance had no effect on OS; however, theirs was a multicenter study across 23 medical centers without cen- tral pathological review.13 Our cases were derived from a single institution, and outcome analysis was restricted to cases with a consensus re-review diagnosis among four expert hematopathologists, lending support to the validi- ty of this finding.
The clinical significance of high-grade histological char- acteristics underscores the importance of the revised WHO recommendation to note morphological appearance in all DH/THL cases.1 Furthermore, because DH/THL cases often show morphological characteristics of DLBCL (40% in this series), a complete interphase FISH analysis to exclude DH/THL is important for all cases with large-cell or high-grade morphological appearance. Also, low MYC expression by immunohistochemistry does not reliably predict absence of a MYC rearrangement. In the present series, 14% of evaluable cases, all with a MYC rearrange- ment by definition, had fewer than 40% MYC-positive cells by immunohistochemistry. However, these cases were too few to analyze outcome, and it is not known whether absence of MYC expression in DH/THL has a favorable impact on survival.
Third, clinical and pathological differences were report- ed and depended on whether a BCL2 rearrangement was present. BCL2-rearranged cases [i.e., MYC/BCL2, MYC/BCL2/BCL6, or MYC/BCL2 (BCL6 unknown)] showed heterogeneous presentation as de novo, recurrent, or transformation events but were uniformly of GCB type. The latter finding has been previously described.4,5,7,9,26 Conversely, MYC/BCL6 cases uniformly developed de novo but were equally likely to be GCB or non-GCB type. Thus, all patients with non-GCB DH/THL in our cohort had MYC/BCL6. Although the association between non-GCB subtype and MYC/BCL6 has been reported previously,5,9 this is the largest cohort to date to investigate this issue.
Clinically, our 12 MYC/BCL6 cases with outcome analysis showed a nonsignificant tendency to superior OS and EFS12, regardless of whether only the de novo cases were evaluated. Previous studies have yielded con-
flicting results. Two studies showed an association between MYC/BCL6 and poor prognosis.9,14 In the first study, only six FISH-confirmed cases were evaluated.14 In the second study, the MYC/BCL6 group, which had older patients with uniformly large-cell histological features, was compared with a MYC/BCL2 group that was younger and had various histological patterns, including low-grade lymphoma.9 Two other studies reported improved survival of patients with MYC/BCL6 compared to those with MYC/BCL2 DH/THL, but only seven and four cases, respectively, were studied.5,44 Another group showed better survival in de novo MYC/BCL6 with large- cell morphological features compared with MYC/BCL2 DH/THL combined with MYC-rearranged single-hit DLBCL.12 Four additional studies – three included patients with large-cell lymphomas and high-grade histological characteristics13,15,25 and one comprised only subjects with large-cell histological features26 - showed no difference in survival between MYC/BCL2 and MYC/BCL6 DH/THL. However, the former two studies also included cases of follicular lymphoma,13,15 and the third study included cases with extra intact signals, as well as rearrangements of MYC, BCL2, and BCL6.25 This lack of uniformity may have affected the outcome data. More studies are needed to resolve the issue of the prognostic significance of MYC/BCL6 in DH/THL.
Some groups have suggested that it may not be neces- sary to perform interphase FISH studies to exclude DH/THL in large-cell or high-grade B-cell lymphomas of non-GCB phenotype. However, if this approach were fol- lowed, about one-half of MYC/BCL6 DH/THL would fail to be identified. The MYC/BCL6 cases in our study showed a tendency toward superior OS and EFS12. Nevertheless, in the light of conflicting outcome data in the literature, potential for poor clinical outcome, and suggested benefit from more aggressive therapy in this cohort, we advocate the performance of interphase FISH to exclude DH/THL in all large-cell and high-grade B-cell lymphomas, regardless of their cell of origin.
Fourth, we found no association between MYC partner (IG gene versus non-IG gene) and clinical outcome. To our knowledge, our study represents the largest (n=87) and most comprehensively studied cohort to date in which
Figure 5. Overall survival according to treatment regimen. Patients treated with R-CODOX-M/R- IVAC had superior overall survival, although the difference was not statistically significant (hazard ratio 0.37, P=0.10). DA-EPOCH-R: dose-adjusted etoposide, prednisone, vincristine, cyclophos- phamide, doxorubicin, and rituximab; R-CHOP: rit- uximab, cyclophosphamide, doxorubicin, and vin- cristine; R-CODOX-M/IVAC: rituximab, cyclophos- phamide, vincristine, doxorubicin, and high-dose methotrexate alternating with rituximab, ifos- famide, etoposide, and high-dose cytarabine; R- hyper-CVAD: rituximab, cyclophosphamide, vin- cristine, doxorubicin, and dexamethasone.
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this issue has been addressed. Previous studies on this matter have yielded conflicting results. Johnson et al., in a retrospective study of 54 DLBCL and BCLU cases with MYC/BCL2 identified by abnormal karyotype, showed that a non-IG/MYC partner was associated with a favor- able clinical outcome.6 However, they also found an asso- ciation between non-IG/MYC partner and DLBCL histo- logical appearance (P<0.001). In contrast, we found no such association in our cohort (P=0.96). This difference may, therefore, in part explain the divergent findings of clinical outcome between the two studies. In addition, case identification by abnormal karyotype may have selected for more aggressive disease. Pedersen et al. prospectively studied a cohort of 237 DLBCL and BCLU cases, including primary, transformed, and relapsed cases.8 They observed that IG/MYC rearrangements (n=9) were associated with a worse OS than were non- IG/MYC rearrangements (n=10). However, only 19 cases were studied, and this analysis included both MYC/BCL2 and MYC single-hit cases but lacked MYC/BCL6 cases. In addition, the patients received various treatment regi- mens, although most included rituximab plus intensive chemotherapy. An additional controversial element was the FISH protocol, because cases that were positive for a MYC rearrangement on the basis of a split MYC break- apart probe but were negative for IGH/MYC fusion were then studied with IGK and IGL break-apart probes rather than IGK/MYC and IGL/MYC dual-fusion FISH probes. Cases with concurrent MYC and IGK or IGL split break- apart probes were presumed to represent fusions, likely overestimating the number of IG/MYC cases.
Copie-Bergman et al. performed interphase FISH using break-apart probes for MYC, BCL2, and BCL6 and dual- fusion FISH probes for IGH/MYC/CEP8, IGK/MYC, and IGL/MYC as needed in 574 de novo DLBCL cases treated with rituximab–anthracycline-based chemotherapy.5 They found that the DH/THL cohort as a whole (n=32) had poorer outcome than the DLBCL cohort that lacked DH/THL rearrangements (P=0.046). However, on evalu- ating the IG/MYC and non-IG/MYC partner cases sepa- rately, Copie-Bergman et al. found that the 12 IG/MYC DH/THL cases had a poorer prognosis than the 19 DH/THL cases without non-IG/MYC rearrangement. They also observed poorer OS and progression-free sur- vival for the 25 MYC/BCL2 cases than for the seven MYC/BCL6 cases, but they did not report the IG gene ver- sus non-IG gene partners for these cases. Therefore, the IG versus non-IG gene results may have been confounded by the number of MYC/BCL2 versus MYC/BCL6 cases in each group. More than 90% of their DH/THL cases had large-cell histological characteristics (3 were reclassified
as high grade on re-review); by comparison, 60% of our cases had high-grade histological characteristics, which may have contributed to the discrepant findings between the two groups.
Other studies have shown no difference in survival between IG/MYC and non-IG/MYC groups. Aukema et al. studied 80 MYC rearrangement-positive B-cell lym- phomas, with exclusion of pediatric cases as well as adult cases with a gene expression profile of molecular BL.9 Most cases had the histological appearance of DLBCL, although some had other histological patterns, such as BCLU and follicular lymphoma. Similar to our study, Aukema et al. found no difference in survival between the IG/MYC and non-IG/MYC groups, both overall and within the MYC/BCL2 (n=26) and MYC/BCL6 (n=14) subgroups. However, various treatment regimens were used, and only some patients received immunotherapy (rituximab). Li et al. also found no significant difference in survival in MYC/BCL2 DH/THL cases with IG (n=23) ver- sus non-IG (n=5) MYC partners.11
More studies are needed to resolve the issue of the prognostic significance of MYC rearrangement partner in DH/THL. Our study, as well as those of Aukema et al.9 and Li et al.,11 suggests that it may not be necessary to identify whether the MYC gene rearrangement partner is an IG gene. Our current approach is to perform FISH on all aggressive B-cell lymphomas. However, in the light of these findings coupled with the association of DH/THL with such features as GCB phenotype, high-grade B-cell lymphoma morphological characteristics, and high MYC expression in immunohistochemistry, further risk-benefit analyses of alternative triage strategies are warranted.
In conclusion, in this large, retrospective, single-institu- tion study of DH/THL, although no differences in sur- vival were seen between the IG/MYC and non-IG/MYC groups, transformation from previously treated and untreated low-grade lymphoma was associated with infe- rior OS, and there was a trend toward inferior OS in patients with high-grade morphological patterns and the presence of a BCL2 rearrangement.
Acknowledgments
We thank Kay M. Ristow for her assistance with database management. This work was supported in part by National Institutes of Health (NIH) Grant no. P50 CA97274 to the University of Iowa and Mayo Clinic Lymphoma Specialized Program of Research Excellence, National Cancer Institute (NCI) Grant n. R01 CA200703, NCI Grant n. U01 CA195568, and the Henry J. Predolin Foundation, Inc. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.
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43. Moore EM, Aggarwal N, Surti U, Swerdlow SH. Further exploration of the complexities of large B-cell lymphomas with MYC abnor- malities and the importance of a blastoid morphology. Am J Surg Pathol. 2017;41(9): 1155–1166.
44. Tzankov A, Xu-Monette ZY, Gerhard M, et al. Rearrangements of MYC gene facilitate risk stratification in diffuse large B-cell lym- phoma patients treated with rituximab- CHOP. Mod Pathol. 2014;27(7):958–971.
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1Research Program Unit, Faculty of Medicine, University of Helsinki, Finland; 2Department of Oncology, Tampere University Hospital, Finland; 3Hematology Research Unit Helsinki, Department of Clinical Chemistry and Hematology, University of Helsinki, Finland; 4Institute for Molecular Medicine Finland (FIMM), Helsinki, Finland; 5Department of Oncology, Comprehensive Cancer Center, Helsinki University Hospital, Finland; 6Department of Pathology, Helsinki University Hospital, Finland; 7Science for Life Laboratory, Karolinska Institutet, Department of Oncology and Pathology, Solna, Sweden; 8Faculty of Medicine and Life Sciences, University of Tampere, Finland; 9Department of Hematology, Comprehensive Cancer Center, Helsinki University Hospital, Finland
Ferrata Storti Foundation
Non-Hodgkin Lymphoma
PD-L1+ tumor-associated macrophages and PD-1+ tumor-infiltrating lymphocytes predict survival in primary testicular lymphoma
Marjukka Pollari,1,2 Oscar Brück,3 Teijo Pellinen,4 Pauli Vähämurto,1,5 Marja-Liisa Karjalainen-Lindsberg,6 Susanna Mannisto,1,5 Olli Kallioniemi,4,7 Pirkko-Liisa Kellokumpu-Lehtinen,2,8 Satu Mustjoki,3,9 Suvi-Katri Leivonen1,5 and Sirpa Leppä1,5
ABSTRACT
Primary testicular lymphoma is a rare and aggressive lymphoid malignancy, most often representing diffuse large B-cell lymphoma histologically. Tumor-associated macrophages and tumor-infiltrat- ing lymphocytes have been associated with survival in diffuse large B- cell lymphoma, but their prognostic impact in primary testicular lym- phoma is unknown. Here, we aimed to identify macrophages, their immunophenotypes and association with lymphocytes, and translate the findings into survival of patients with primary testicular lymphoma. We collected clinical data and tumor tissue from 74 primary testicular lymphoma patients, and used multiplex immunohistochemistry and digital image analysis to examine macrophage markers (CD68, CD163, and c-Maf), T-cell markers (CD3, CD4, and CD8), B-cell marker (CD20), and three checkpoint molecules (PD-L1, PD-L2, and PD-1). We demon- strate that a large proportion of macrophages (median 41%, range 0.08- 99%) and lymphoma cells (median 34%, range 0.1-100%) express PD- L1. The quantity of PD-L1+CD68+ macrophages correlates positively with the amount of PD-1+ lymphocytes, and a high proportion of either PD-L1+CD68+ macrophages or PD-1+CD4+ and PD-1+CD8+ T cells trans- lates into favorable survival. In contrast, the number of PD-L1+ lym- phoma cells or PD-L1– macrophages do not associate with outcome. In multivariate analyses with IPI, PD-L1+CD68+ macrophage and PD-1+ lymphocyte contents remain as independent prognostic factors for sur- vival. In conclusion, high PD-L1+CD68+ macrophage and PD-1+ lympho- cyte contents predict favorable survival in patients with primary testic- ular lymphoma. The findings implicate that the tumor microenviron- ment and PD-1 – PD-L1 pathway have a significant role in regulating treatment outcome. They also bring new insights to the targeted thera- py of primary testicular lymphoma.
Introduction
Primary testicular lymphoma (PTL) is a rare and aggressive lymphoid malignancy affecting mainly elderly men. The biology of PTL is beginning to emerge,1-7 and the outcome has improved with the addition of anthracycline-based chemotherapy, central nervous system (CNS) targeted therapy and irradiation of the contralateral testis.8-10 The majority of PTLs represent diffuse large B-cell lymphoma (DLBCL) displaying more often non-germinal center B-cell (GCB) than GCB-like signatures.11 Somatic mutations in NF-κ-B pathway genes, such as MYD88 and CD79B, as well as rearrangements of programmed cell death ligand (PD-L) -1 and -2 genes, have been shown to be enriched in PTL.2,4 In addition, two stromal signatures associated
Correspondence:
sirpa.leppa@helsinki.fi
Received: May 6, 2018. Accepted: July 16, 2018. Pre-published: July 19, 2018.
doi:10.3324/haematol.2018.197194
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1908
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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with outcome have been described in primary, mainly nodal DLBCL patients treated with immunochemothera- py, forming the backbone for our study.12 We have recent- ly demonstrated that tumor-associated macrophages (TAMs) have a favorable prognostic impact on survival in DLBCL patients after immunochemotherapy,13 whereas other groups have investigated the role of programmed cell death-1 (PD-1) pathway in DLBCL.14-18 While PD-1 protein is expressed predominantly by activated tumor- infiltrating lymphocytes (TILs), its ligands (PD-L1 and PD- L2) have been shown to be expressed both by the tumor
15,19-21
cells and the tumor microenvironment. An unexpect-
ed feature has been that PD-L1 expression by the tumor- infiltrating myeloid and other immune cells can be more prevalent than PD-L1 expression by the tumor cells.15,19,20 Recently, it was also shown that the expression of PD-L1, not only by the tumor cells but also by the host cells, plays a critical role in mediating the immunosuppressive func- tion of the PD-1 pathway.21
In DLBCL, expression of PD-L1 by lymphoma cells has been associated with poor outcome.14 Interestingly, 9p24.1/PD-L1/PD-L2 copy number alterations and addi- tional translocations of these loci are frequent in PTLs (>50%), leading to increased expression of the PD-Ls,4 and possibly also to immune escape. Whether the expression of PD-1 and PD-Ls predict survival in PTL, and in which compartments, is unknown.
With the aim of resolving the relative expression of checkpoint molecules by the tumor and host immune cells in patients with PTL, we examined B cells, TAMs, TILs, and checkpoint molecules by using multiplex immunohis- tochemistry (mIHC),22 allowing simultaneous detection of CD68+ TAMs, CD163+ or c-Maf+ M2-polarized TAMs, CD4+ and CD8+ T cells, CD20+ B cells, and the checkpoint molecules PD-L1, PD-L2 and PD-1. The findings were cor- related with clinical parameters and survival.
Methods
Patients
We identified 74 PTL patients with DLBCL histology diagnosed between the years 1987 and 2013 from the pathology databases of the University Hospitals in Southern Finland. Histological diagno- sis was established from surgical pretreatment tumor tissue according to current criteria of the World Health Organization (WHO) classification.23 The majority of the patients were treated with anthracycline-based chemotherapy. About half of the patients received rituximab as a part of their treatment. Contralateral testis was treated with surgical excision or irradia- tion for a minority of the patients. Patients were divided into three equal tertiles, based on the content of different immune cell sub- types (high, intermediate, low). The patient characteristics are described in more detail in Table 1. The protocol and sampling were approved by the Institutional Review Boards, Ethics Committees and the Finnish National Supervisory Authority for Welfare and Health.
Multiplex immunohistochemistry (mIHC)
Formalin-fixed, paraffin-embedded (FFPE) primary tumor tis- sues were collected from the local biobanks and reviewed to match the latest WHO classification.23 Selection of the cores on the tissue microarray (TMA) was based on the evaluation of a hematopathologist. TMA was constructed and the sections (3.5 μm) stained with 4-plex primary antibody panels (PD-L1, PD-L2,
CD68, c-MAF; CD3, CD4, CD8, PD-1; CD20, CD163, PD1, PD- L1; Online Supplementary Table S1), followed by fluorescently labelled secondary antibodies and DAPI counterstain (nuclear stain). A more detailed description of the stainings is provided in the Online Supplementary Methods. Fluorescent images were acquired with AxioImager.Z2 (Zeiss, Germany). Machine-learning platform CellProfiler24 2.1.2 was used for cell segmentation, inten- sity measurements (upper quartile intensity) and immune cell clas- sification. Different cell types were quantified as proportion to all cells (e.g., PD-L1+CD68+ implying the number of PD-L1+CD68+ TAMs from all cells in a TMA spot) or as a proportion to a specific cell subtype (e.g., PD-L1+CD68+/CD68+ implying the number of PD-L1+CD68+ cells from all CD68+ TAMs). Spots with less than 5000 cells were excluded from the analysis, and data from dupli- cate spots from the same patient were merged.
Gene expression analysis
CD68, CD163, MAF, MS4A1 (CD20), CD274 (PD-L1), PDCD1LG2 (PD-L2), and PDCD1 (PD-1) mRNA levels were measured from 60 PTL samples using digital gene expression analysis with NanoString nCounter (Nanostring Technologies, Seattle, WA, USA).25
Survival definitions and statistical analyses
Overall survival (OS) was defined as time between diagnosis and death from any cause, disease specific survival (DSS) as time between diagnosis and lymphoma related death, and progression free survival (PFS) as time between diagnosis and lymphoma pro- gression or death from any cause.
Statistical analyses were performed with IBM SPSS v.24.0 (IBM, Armonk, NY, USA). Differences in the frequency of prognostic factors between three patient groups were analyzed by Kruskal- Wallis test. Correlations between gene expression values and cell counts as well as between different immune cell subpopulations were tested with Spearman's rank correlation.
Survival rates were estimated using the Kaplan–Meier method. Univariate and multivariate analyses were performed according to the Cox proportional hazards regression model. The potential bias due to duration of follow up was assessed by Schoenfeld residual. Probability values below 0.05 were considered statistically signifi- cant. All comparisons and all comparative tests were two-tailed.
Results
Patient characteristics
Patient and treatment characteristics of the study cohort are shown in Table 1. The majority of the patients repre- sented non-GCB phenotype, low stage, and had low/intermediate International Prognostic Index (IPI). Altogether, 34 deaths, 24 relapses and 24 lymphoma-asso- ciated deaths occurred during the median follow up of 67 months (range from 6.7 to 120 months). Five-year OS, DSS and PFS rates were 56%, 68%, and 53%, respectively.
Association of CD68, PD-L1 and PD-L2 encoding gene expression with survival
First, we determined the gene expression of the macrophage markers (CD68, CD163 and MAF), check- point molecules CD274 (PD-L1), PDCD1LG2 (PD-L2) and PDCD1 (PD-1), and the B-cell marker MS4A1 (CD20). CD68 expression correlated positively with CD274 (rs=0.654, P<0.001), PDCD1LG2 (rs=0.636, P<0.001), CD163 (rs=0.602, P<0.001), and MAF (rs=0.425, P=0.001) levels, and to a lesser extent with PDCD1 (rs=0.300, P=0.020), whereas no correlation between CD68 and
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Table 1. Patient and treatment characteristics.
All n (%)
PD-L1+ CD68+ low
25 (34)
68 (38-86)
6 (24) 19 (76)
GCBa
Non-GCB
NA 1(1) 1(4)
Stage
I-II 47 (64) 10 (40) 16 (67) 21 (84) III-IV 24 (32) 15 (60) 6 (25) 3 (12) NA 3(4) 2(8) 1(4)
Number of patients
Median age (range) Age
<60, years ≥ 60, years
Molecular subgroup
74
70 (36-92)
17 (23) 57 (77)
PD-L1+
CD68+ intermed.
24 (32)
73 (37-92)
4 (17) 20 (83)
PD-L1+ CD68+ high
25 (34)
66 (46-90)
7 (28) 18 (72)
P
0.638
0.426
0.002
0.065
0.137 0.057 0.856 0.464 0.136 0.884 0.305 0.237 0.377 0.312
17 (23) 56 (76)
8 (32) 17 (68)
4 (17) 20 (83)
5 (20) 19 (76)
IPI score
0-2 3-5 NA
CNS prophylaxis IV prophylaxis IT prophylaxis
Contralateral testis treated
Irradiation
Surgical excision
Anthracycline-based chemotherapy
Treated with rituximab
Relapse of contralateral testis
CNS progression
50 (68) 13 (52) 17 (71) 20 (80) 20 (27) 11 (44) 5 (21) 4 (16) 4(5) 1(4) 2(8) 1(4)
36 (49) 34 (46) 7 (9) 23 (31) 12 (16) 11 (15) 60 (81) 35 (47) 1 (1)
9 (12)
9 (36) 8 (32) 2 (8) 6 (24) 2 (8) 4 (16) 18 (72) 9 (36) 0 (0)
4 (16)
11 (46) 10 (42) 3 (13) 7 (29) 3 (13) 4 (17) 21 (88) 11 (46) 1 (4) 4 (17)
16 (64) 16 (64) 2 (8) 10 (40) 7 (28) 3 (12) 21 (84) 15 (60) 0 (0) 1 (4)
aGCB: germinal center B-cell like; NA: not applicable; IPI: International prognostic Index; CNS: central nervous system; IV: intravenous; IT: intrathecal; P: P-value determined by Kruskal-Wallis test.
MS4A1 expression was found. Furthermore, the expres- sion of CD68, CD274 and PDCD1LG2 genes analyzed as continuous variables, but not PDCD1, CD163 or MAF, translated into favorable survival (Table 2).
High PD-L1+ TAM content predicts favorable survival
To explore the expression of the checkpoint molecules in the tumor cells and in the microenvironment in more detail, we analyzed the cell immunophenotypes with mIHC from a PTL TMA using four primary antibodies and DAPI (nuclear stain) simultaneously (Figure 1A-C; see also Table 1 for the TMA cohort used and Online Supplementary Table S1 for the antibody panels). The marker CD68 was used to identify all TAMs. Subpopulations of TAMs were defined by the presence and absence of CD163, c-MAF, PD-L1 and PD-L2 (Figure 1A-B, D). In addition, CD20 marker was used to identify lymphoma cells (Figure 1B). For detecting TILs, a panel with CD3, CD4, CD8, and PD1 antibodies was used (Figure 1C).
As proof of concept, we found high agreement with the gene expression and the mIHC data when analyzing the quantities of CD68+ macrophages (rs=0.637, P<0.001),
Table 2. Cox regression analysis at the univariate level showing asso- ciation of gene expression levels with overall survival.
Gene symbol
CD68
CD274 PDCD1LG2 PDCD1 CD163 MAF
HRa 95% CI
0.505 0.290-0.881
0.737 0.592-0.919
0.688 0.505-0.936
0.846 0.659-1.088
0.914 0.636-1.313
0.899 0.551-1.466
P
0.016
0.007
0.017
0.192
0.627
0.668
aHR: hazard ratio; CI: confidence interval. Boldface font indicates statistical signifi- cance (P<0.05).
lymphoma cells (rs=0.704, P<0.001) and PD-L1+ cells (rs=0.710, P<0.001) (Online Supplementary Figure S1). The proportions of the different cell types in the tumor tissue are shown in Figure 1D. The most prominent non-malig- nant cell type was CD3+ T-lymphocyte (median 45%, range 5-97%). TAM and PD-L1+ cell contents showed a great variation between the samples (CD68+ TAMs, medi- an 23%, range 3-81%; PD-L1+ cells, median 15%, range 0.01-100%), and a large proportion of lymphoma cells (median 34%, range 0.1-100%) and TAMs (median 41%,
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AD
B
C
Figure 1. Characterization of cell immunophenotypes with mIHC. (A-C) Representative images from 4-plex mIHC stainings. Panels (low, intermediate, and high) show representative images from the corresponding tertiles, based on the content of different immune cell subtypes. The insets highlight cells with higher magnification. PD-L1=blue, PD-L2=red, CD68=white, c-Maf=green (A); PD-L1=blue, CD163=red, CD20=white, PD1=green (B); CD3=blue, CD8=red, CD4=white, PD1=green (C). Scale bar 40 mm. (D) Proportions of distinct immune cell subpopulations from all cells. PD-L1+CD68+ indicating the content of PD-L1+ TAMs, PD-L1+CD163+ and PD- L1+CD68+c-Maf+ the content of PD-L1+ M2-polarized TAMs, PD-1+CD3+CD4+ and PD-1+CD3+CD8+ the content of PD-1+ TILs, and PD-L1+CD20+ the content of PD-L1+ lymphoma cells.
range 0.1-99%) expressed PD-L1. Due to a low proportion of PD-L2+ cells (0.06%) (data not shown), PD-L2 was excluded from further analyses.
We further observed that a high number of PD-L1+ cells, high proportion of PD-L1+CD68+ macrophages from all cells, as well as a high proportion of PD-L1+CD68+ macrophages from all CD68+ macrophages (PD- L1+CD68+/CD68+), associated with favorable OS when analyzed as continuous variables (Table 3). In order to use an objective cutoff, we stratified the patients into three equal subgroups based on tertiles of the PD-L1+CD68+ macrophage counts (high, intermediate, low). The 5-year OS and DSS rates were clearly worse for the patients with a low number of PD-L1+CD68+ macrophages (≤4.75% corresponding to the lowest tertile of the patients) in com- parison to the patients with intermediate or high numbers (>4.75%, 5-y OS, 39% vs. 66%, P=0.014; 5-y DSS, 53% vs. 76%, P=0.056; Figure 2A). When PD-L1+CD68+ macrophage count was included in a multivariate analysis with IPI, both factors had independent prognostic value for OS (Table 4). In contrast, neither PD-L1+ lymphoma cells, PD-L1+CD68– cells nor any other TAM phenotypes were significantly associated with survival (Table 3). When comparing the three PD-L1+CD68+ TAM subgroups (high, intermediate and low), no significant differences in age, molecular subtype, IPI score or treatments were observed (Table 1). However, high PD-L1+CD68+ macrophage count was associated with limited disease stage. When the patients treated in the pre-rituximab era were removed from the analyses, a trend towards worse survival was maintained for the patients with low number of PD-L1+CD68+ macrophages (≤5.97%, the lowest tertile; OS, P=0.093, Online Supplementary Figure S2A). These
Table 3. Cox regression analysis at the univariate level showing asso- ciation of cell immunophenotypes with overall survival.
Cell immunophenotype
PD-L1+
HRa 95% CI
0.983 0.967-0.999
1.009 0.995-1.023
0.993 0.978-1.008
0.981 0.955-1.007
0.986 0.964-1.008
0.965 0.933-0.999
0.987 0.975-0.998
1.012 0.982-1.043
0.835 0.668-1.044
0.734 0.518-1.041
0.996 0.978-1.014
0.989 0.969-1.010
0.194 0.053-0.712
0.089 0.008-0.999
0.042 0.003-0.537
P
0.038
0.209
0.376
0.146
0.196
0.042
0.027
0.437
0.113
0.083
0.666
0.298
0.013
0.050
0.015
CD20+ PD-L1+CD20+ PD-L1+CD68- CD68+
PD-L1 CD68
+++ PD-L1+CD68+/CD68
–+ PD-L1 CD68
CD68+c-Maf+ PD-L1+CD68+c-Maf+ CD163+ PD-L1+CD163+
+ CD3
PD-1+CD3+CD4+
PD-1+CD3+CD8+
aHR: hazard ratio; CI: confidence interval; PD-L1+CD68+ implies the number of PD-
L1+CD68+ TAMs from all cells; PD-L1+CD68+/CD68+ implies the number of PD-L1+CD68+ +
TAMs from all CD68 TAMs. Boldface font indicates statistical significance (P<0.05).
results highlight the clinical relevance and possible func- tional connection of PD-L1+ TAMs for PTL progression.
Association of PD1+ TILs with survival
Given the prognostic value of PD-L1+ TAMs, we then determined their association with T cells by mIHC. The marker CD3 was used to identify all T cells. Subpopulations of T cells were then defined by the pres-
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AB
C
Figure 2. Association of the immune cell subtypes with survival. (A-C) Cell immunophenotypes were determined by mIHC from 74 PTL patients. Patients were strat- ified into three equal subgroups (high, intermediate and low) based on tertiles of PD-L1+CD68+ TAM, PD-1+CD3+CD4+ T cell, and PD-1+CD3+CD8+ T-cell counts. Kaplan- Meier plots depict survival differences between the PD-L1+CD68+ (A), PD-1+CD3+CD4+ (B), and PD-1+CD3+CD8+ (C) groups. P-values were determined by univariate Cox regression analysis (HR, hazard ratio with 95% confidence interval).
Table 4. Cox regression analysis at multivariate level showing inde- pendent association of low cell immunophenotypes and IPI high (IPI 3-5) with overall survival.
corresponding to the lowest tertile vs. other patients; 5-y OS, 39% vs. 65%, P=0.008; 5-y DSS, 43% vs. 81%, P<0.001; Figures 2B-C). In multivariate analyses with IPI, both PD-1+CD3+CD4+ and PD-1+CD3+CD8+ T-cell counts maintained an independent association with OS (Table 4). When the patients treated in the pre-rituximab era were removed from the analyses, a low number of PD-1+ T cells maintained their adverse impact on survival (PD- 1+CD3+CD4+ cells, ≤8.50%, the lowest tertile; OS, P=0.001 and PD-1+CD3+CD8+ cells, ≤11.02%, the lowest tertile; OS, P=0.034; Online Supplementary Figure S2B-C).
Discussion
In this study, we applied mIHC and digital image analy- sis to a TMA comprised of PTL tissue from 74 patients. We show that PTL microenvironment contains a hetero- geneous TAM population. Among these, PD-L1+ TAMs were the predominant subpopulation, and high infiltra- tion of PD-L1+CD68+ TAMs was associated with favorable survival. Additionally, PD-1+ CD4+ and CD8+ TIL contents correlated with PD-L1+ TAM infiltration and survival, and both PD-L1+ TAMs and PD-1+ TILs emerged as independ- ent indicators of survival for the patients with PTL. In con- trast, neither PD-L1+ lymphoma cells, other PD-L1+ cells
Cell immunophenotype
PD-L1+CD68+
HRa 95% CI
2.214 1.054-4.650
P
0.036
4.325 2.008-9.312 2.275 1.054-4.909 3.608 1.643-7.923 2.654 1.261-5.586 4.907 2.275-10.585 2.259 1.075-4.748 4.971 2.314-10.678
IPI
PD-L1+CD68+/CD68+
IPI
PD-1+CD3+CD4+
IPI
PD-1+CD3+CD8+
IPI
aHR, hazard ratio; CI: confidence interval; IPI: International Prognostic Index.
<0.001 0.036 0.001 0.010 <0.001 0.031 <0.001
ence and absence of CD4, CD8 and PD-1 (Figure 1C-D). As with CD4+ T-helper and CD8+ cytotoxic cells in gener- al, PD-1+CD3+CD4+ and PD-1+CD3+CD8+ T-cell counts correlated with the PD-L1+ TAM counts (Online Supplementary Table S2). Furthermore, as overall with T-cells,25 a high and intermediate number of PD-1+ CD4+ and CD8+ T-cells associated with superior survival (PD- 1+CD3+CD4+ cells ≤5.7% corresponding to the lowest ter- tile vs. other patients; 5-y OS, 34% vs. 68%, P=0.002; 5-y DSS, 43% vs. 81%, P<0.001; PD-1+CD3+CD8+ cells, ≤7.2%
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than TAMs, nor other TAM phenotypes correlated with survival. The findings highlight the specific roles of TAMs, TILs and PD-1-PD-L1 axis in regulating survival and ther- apy resistance in PTL.
mIHC is a novel technology enabling multi-parametric readout from a single tissue section. In our study, the simultaneous use of multiple markers is important in many ways. Firstly, while PD-L1 was found to be expressed both in TAMs and B cells including lymphoma cells, the prognostic impact of PD-L1 positivity was restricted to TAMs. Thus, the use of just one marker would not be able to detect the survival association. Secondly, the spatial relationships between TILs, TAMs and lymphoma cells are retained in our experimental strat- egy, allowing for a more precise appreciation of their bio- logical interactions. Thirdly, since mIHC was performed on all evaluable PTL tissue areas on the TMA, thereby providing an overall snapshot of the PTL microenviron- ment, we can avoid a bias of earlier observations focusing only on hot spot areas of immune cell counts using single marker immunohistochemistry. However, it should be noted that while the overall infiltration of PD-L1+ TAMs and PD-1+ TILs had a significant impact on survival, their functional statuses remain to be explored. Combining our panel with other multiplex panels for immunoregulatory molecules, such as FoxP3, LAG-3 or IDO-1 and IDO-2, may be useful in the evaluation of response to immunotherapy.
As described in a recent review article by Xu-Monette et al., the PD-L1 expression in the tumor microenvironment has not been previously well defined in B-cell lymphomas, and association with survival has not been demonstrat- ed.18 PD-1 is a protein, which is classically upregulated upon activation of T lymphocytes. Interaction between PD-1 and PD-L1 was previously thought to induce immune tolerance by leading T lymphocytes to apoptosis.26 Further studies have, however, revealed that the expression of PD-L1 on tumor cells can lead to immune escape, to T-cell exhaustion and a state of non- responsiveness, further enabling immune escape of the tumor cells.27-29 Moreover, in addition to binding to PD-1,
PD-L1 and PD-L2 can also bind to CD80/B7-1 (PD-L1)30,31
and RGMb (PD-L2),32 indicating that the PD-1 – PD-L1
pathway is much more complex than previously anticipat- ed.18
In addition to PD-L1, macrophages express PD-1.33,34 Recently, Gordon and coworkers showed that PD-1 expression by TAMs inhibits phagocytosis and tumor immunity.35 In addition, they demonstrated that blockade of PD-1 – PD-L1 interaction increases macrophage phago- cytosis, reduces tumor growth and lengthens survival in mouse models of colon cancer, suggesting the PD-1 – PD- L1 pathway has a significant role in TAM function and tumor survival.
Based on our findings, we suggest that the PD-1 - PD-L1 signaling between TAMs and TILs has clinical relevance in PTL. As PD-1 engagement on T cells to its ligands has been linked to decreased anti-tumor immunity, and early experience on PD-1 blockade in PTL has shown promising results,36 the association of high PD-L1+ TAM and PD-1+ T- cell count with favorable outcome in response to immunochemotherapy seems paradoxical. Yet, the inter- action of PD-L1+ TAMs and PD-1+ T cells might modify the tumor microenvironment in PTL, or otherwise pro- mote an anti-tumor immune response following immunochemotherapy.
In conclusion, we argue that high PD-L1+ TAM and PD-1+ T-cell counts correlate with each other and with favorable outcome in patients with PTL. Higher PD- L1+CD68+ TAM scores seem to protect the patients from progression and death, and identify a group of patients with favorable prognosis. Interestingly, apart from PD-L1+CD68+ TAMs, no association was found between other PD-L1+ cells or PD-L1– TAMs and survival. Together, the data demonstrate that the PD-1 - PD-L1 axis in PTL affects the survival of patients with PTL.
Acknowledgments
We thank Drs. Petri Auvinen and Lars Paulin (Institute of Biotechnology, University of Helsinki), Finland for the Nanostring analyses. Anne Aarnio and Marika Tuukkanen are acknowledged for technical assistance.
References
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A phase II/III randomized, multicenter trial of prednisone/sirolimus versus prednisone/ sirolimus/calcineurin inhibitor for the treatment of chronic graft-versus-host disease:
BMT CTN 0801
Ferrata Storti Foundation
Paul A. Carpenter,1 Brent R. Logan,2 Stephanie J. Lee,1 Daniel J. Weisdorf,3 Laura Johnston,4 Luciano J. Costa,5 Carrie L. Kitko,6 Javier Bolaños-Meade,7 Stefanie Sarantopoulos,8 Amin M. Alousi,9 Sunil Abhyankar,10 Edmund K. Waller,11 Adam Mendizabal,12 Jiaxi Zhu,12 Kelly A. O’Brien,12 Aleksandr Lazaryan,3 Juan Wu,12 Eneida R. Nemecek,13 Steven Z. Pavletic,14 Corey S. Cutler,15 Mary M. Horowitz2 and Mukta Arora3 on behalf of the BMT CTN.
Haematologica 2018 Volume 103(11):1915-1924
1Fred Hutchinson Cancer Research Center, Seattle, WA; 2Medical College of Wisconsin, Milwaukee, WI; 3University of Minnesota, Minneapolis, MN; 4Stanford Hospital and Clinics, Stanford, CA; 5University of Alabama at Birmingham, AL; 6Vanderbilt University School of Medicine, Nashville, TN; 7Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD; 8Duke University Medical Center, Durham, NC; 9University of Texas MD Anderson Cancer Center, Houston, TX; 10The University of Kansas Medical Center, Kansas City, KS; 11Emory University School of Medicine, Atlanta, GA; 12The Emmes Corporation, Rockville, MD; 13Oregon Health and Sciences University, Portland, OR; 14Experimental Transplantation and Immunology Branch, National Cancer Institute, Bethesda, MD and 15Dana Farber Cancer Institute, Boston, MA, USA
ABSTRACT
Initial therapy of chronic graft-versus-host disease is prednisone ± a cal- cineurin-inhibitor, but most patients respond inadequately. In a ran- domized, adaptive, phase II/III, multicenter trial we studied whether prednisone/sirolimus or prednisone/sirolimus/photopheresis was more effective than prednisone/sirolimus/calcineurin-inhibitor for treating chronic graft-versus-host disease in treatment-naïve or early inadequate responders. Primary endpoints of this study were proportions of sub- jects alive without relapse or secondary therapy with 6-month com- plete or partial response in phase II, or with 2-year complete response in phase III. The prednisone/sirolimus/photopheresis arm closed pre- maturely because of slow accrual and the remaining two-drug versus three-drug study ended in phase II due to statistical futility with 138 evaluable subjects. The two-drug and three-drug arms did not differ in rates of 6-month complete or partial response (48.6% versus 50.0%, P=0.87), or 2-year complete response (14.7% versus 15.5%, P=0.90). Serum creatinine values >1.5 times baseline were less frequent in the calcineurin-inhibitor-free arm at 2 months (1.5% versus 11.7%, P=0.025) and 6 months (7.8% versus 24.0%, P=0.016). Higher adjusted Short Form-36 Physical Component Summary and Physical Functioning scores were seen in the two-drug arm at both 2 months (P=0.02 and P=0.04, respectively) and 6 months (P=0.007 and P=0.001, respectively). Failure-free survival and overall survival rates at 2 years were similar for patients in the the two-drug and three-drug arms (48.6% versus 46.2%, P=0.78; 81.5% versus 74%, P=0.28). Based on sim- ilar long-term outcomes, prednisone/sirolimus is a therapeutic alterna- tive to prednisone/sirolimus/calcineurin-inhibitor for chronic graft-ver- sus-host disease, being easier to administer and better tolerated. Clinicaltrials.gov identifier: NCT01106833.
Correspondence:
pcarpent@fredhutch.org
Received: April 7, 2018. Accepted: June 26, 2018. Pre-published: June 28, 2018.
doi:10.3324/haematol.2018.195123
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1915
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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ARTICLE
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Introduction
Chronic graft-versus-host disease (GvHD) is the major treatment-related complication among patients who sur- vive after allogeneic hematopoietic cell transplantation. The protracted duration of chronic GvHD and its protean and sometimes irreversible organ manifestations makes it the leading cause of impaired immunity, compromised functional status, and late treatment-related deaths.1,2 Standard immunosuppressive therapy with prednisone ± a calcineurin inhibitor (CNI) has not changed for three decades, but most patients respond inadequately with slow and most often incomplete control of their disease. The results of six phase III chronic GvHD trials that tested prednisone or prednisone/CNI backbones with or without an experimental immunosuppressive therapy have not changed clinical practice, because the treatments tested in the experimental arms did not improve outcomes due to lack of efficacy and/or more toxicity.3-8 Between 2005- 2007, reports of phase II trials from single centers showed promising results for prednisone combined with sirolimus, rituximab, mycophenolate mofetil, pentostatin or extracorporeal photopheresis (ECP).9-13 At the same time, renewed understanding of regulatory T cells (Treg) led to the hypothesis that experimental therapies permis- sive of Treg expansion would abrogate GvHD better than CNI-containing (control) immunosuppressive therapy. Sirolimus and ECP are permissive of Treg expansion.14-18 Because of their acceptance in clinical practice sirolimus and ECP were considered good candidates to add to pred- nisone in clinical trials investigating chronic GvHD.
This background, together with the 2005 National Institutes of Health (NIH) chronic GvHD criteria,19 plus other efforts designed to propel the field forward,20,21 moti- vated the Blood and Marrow Transplant Clinical Trials Network (BMT CTN) to conduct an intervention trial for chronic GvHD. The intent was an adaptive phase II/III design to minimize between-phase downtime. The pri- mary purpose of phase II was to select the more promising of two CNI-free approaches (prednisone/sirolimus and prednisone/sirolimus/ECP) in order to proceed seamlessly into a definitive phase III study against a CNI-containing comparator arm (prednisone/sirolimus/CNI). The study also provided an opportunity to use the NIH diagnostic and response criteria prospectively and to validate them.
Methods
Patients
Adult and pediatric allogeneic hematopoietic cell transplant recipients were eligible if they had classic chronic GvHD ± acute GvHD (overlap subtype) that met 2005 NIH diagnostic consen- sus criteria.19 Eligibility criteria were broad and allowed a period of steroid exposure prior to enrollment to ensure congruence with standard practice. Thus, eligible patients were either: newly diagnosed patients, defined as individuals who had received <14 days of prednisone (or equivalent) before randomization to the study therapy, or previously treated, but responding inadequate- ly after ≤16 weeks of initial therapy with prednisone and/or a CNI ± an additional non-sirolimus agent started at the time that the chronic GvHD was diagnosed. Major reasons for exclusion were patients with late persistent acute GvHD or recurrent acute GvHD only, patients unable to begin prednisone at a dose of 0.5 mg/kg day (or equivalent), patients already receiving sirolimus
for treatment of chronic GvHD, and patients already receiving sirolimus (for prophylaxis or treatment of acute GvHD) along with prednisone at ≥0.25 mg/kg/day (or equivalent) ± additional agents. Patients were also ineligible if they had an invasive fungal or viral infection not responding to appropriate therapies, a crea- tinine clearance <50 mL/min/1.73 m2 based on the Cockcroft- Gault (adults) or Schwartz (age ≤12 years) formula, an absolute neutrophil count <1.5x109/L, a requirement for platelet transfu- sion, or a progressive or recurrent malignancy defined other than by quantitative molecular assays. Institutional review boards at all participating centers provided ethics approval. All patients or their parents signed informed consent to participation in the trial in accordance with the Declaration of Helsinki.
Treatment plan
The starting dose of prednisone (or prednisone-equivalent) was 1 mg/kg once daily, unless contraindicated, in which case the prednisone dose began at 0.5-1 mg/kg once daily. It was recom- mended that the dose of prednisone was tapered down, over 4-8 weeks to reach a dose of 0.5-1 mg/kg every other day, with the tapering starting within 2 weeks after the first evidence of GvHD improvement. Once an every-other-day prednisone (or equiva- lent) regimen was achieved, this dose remained constant for 10- 12 weeks until all reversible chronic GvHD manifestations resolved. A second taper was then attempted and could follow individual institutional guidelines, but it was recommended that the extent of the tapering be approximately calibrated to the magnitude of an individual patient’s every-other-day prednisone dose. CNI therapy was continued by targeting trough serum lev- els of 5-10 ng/mL for tacrolimus (120-200 ng/mL for cyclosporine). The sirolimus therapy began at a dose of 2 mg orally once daily (1 mg/m2 per day if the patient weighed <40 kg) to target trough serum levels of 3-12 ng/mL. Supportive care was provided in accordance with institutional guidelines reflecting standard practices appropriate for chronic GvHD.22
Study design
The trial was designed as an adaptive phase II/III randomized, open-label, prospective study of three treatments for chronic GvHD (Figure 1, Online Supplementary Figures S1 and S2). Phase II included two parallel, 100-patient, randomized trials, comparing prednisone/sirolimus or prednisone/sirolimus/ECP versus identi- cal (prednisone/sirolimus/CNI) comparator arms. The primary objective of phase II was to estimate the proportion of study sub- jects at 6 months after randomization with complete or partial response, who were alive without relapse or receipt of secondary immunosuppressive therapy. A sufficiently promising phase II result would determine whether the trial would proceed into phase III with additional accrual, would continue as phase II, but be followed for longer phase III endpoints without additional accrual, or would end in failure without further follow-up (Online Supplementary Figure S2). Full details of the study design, endpoint definitions, statistical analysis and study timeline are contained in the Online Supplementary Material.
Results
Patients
One hundred patients were evaluated for the phase II primary endpoint after all had completed 6 months of fol- low-up. The Z-statistic comparing complete/partial response rates (51% versus 50%, Z=0.11, stopping bound- ary Z6≤0.9) did not support proceeding to phase III and, together with pre-specified outcome scenarios, guided the
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Data and Safety Monitoring Board recommendation to suspend further phase III accrual; however, all 151 enrolled subjects were followed for phase III endpoints (Online Supplementary Figure S2B). The endpoint review committee response adjudication determined that 13 (10%) subjects had not satisfied the NIH criteria for the diagnosis of chronic GvHD at enrollment and were ineli- gible (Online Supplementary Figure S1C); a screening diag- nostic checklist for NIH-defined chronic GvHD was required after July 24, 2013. One-hundred thirty-eight remaining subjects were randomized: 72 were assigned to two drugs and 66 to three drugs. Endpoint review com- mittee-adjudicated complete/partial response rates and provider-reported complete/partial response rates were concordant at 6 months (Cohen κ = 0.78) and at 2 years (κ = 0.88). Participants lost to follow-up, or who relapsed, died, or began secondary immunosuppressive therapy were excluded from these agreement tests.
Patients’ demographic and transplant characteristics were mostly similar between treatment groups (Table 1). The median age was 50.2 years in the two-drug arm and 54.7 years in the three-drug arm. Characteristics that were more frequent in the two-drug arm were male gen- der (66.7% versus 50%), Hispanic ethnicity (11.1% versus 0%), an underlying diagnosis of acute leukemia (65.3% versus 37.9%), transplants done for early stage disease (63.9% versus 40.9%), myeloablative conditioning (65.3% versus 43.9%), and CNI/methotrexate-based GvHD pro- phylaxis (61% versus 33.3%). Lymphoma was less fre- quent in the two-drug arm (6.9% versus 25.8%). Donor or stem cell sources did not differ between arms.
Chronic GvHD characteristics were similar between the two-drug and three-drug arms (Table 2), including the pro- portion of subjects with high-risk chronic GvHD (51.4% versus 48.5%), median time from hematopoietic cell trans- plant to enrollment (7.3 versus 7.7 months), and median time from chronic GvHD diagnosis to enrollment (7 versus 10 days). Sixty-two percent of the study subjects were enrolled within 14 days of a new diagnosis of chronic GvHD and 38% were responding inadequately to initial therapy; classic and overlap subtypes were equally repre- sented. Global severity scores were mainly moderate (67%), then mild (21%) and severe (12%); 43% of the patients had progressive onset chronic GvHD. The organs involved were the skin (76%), mouth (74%), liver (71%), eyes (54%), gastro-intestinal tract (46%), joints/fascia (24%), genital tract (17%), and lungs (15%) with the pat- tern of involvement being similar between the treatment groups except for genital tract involvement, which was more common in the group treated with three drugs (10% versus 26%, but only 63% of the study population were scored).
Response and survival
The treatment success rate at 6 months was 48.6% [95% confidence interval (CI): 36.7%-60.7%] with two drugs versus 50.0% (95% CI: 37.4%-62.6%) with three drugs P=0.87). The rate of more stringently defined treat- ment success at 2 years (complete responses only) was 14.7% (95% CI: 7.3%-25.4%) with two drugs versus 15.5% (95% CI: 7.4%-27.4%) with three drugs (P=0.90) (Table 3). Since very good partial response is clinically rel-
Figure 1. BMT CTN 0801 Consort flow diagram. ECP: extracorporeal photo- pheresis; PDN: prednisone; SRL: sirolimus; CNI: calcineurin inhibitor.
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evant, we compared the proportion of patients with com- plete response/very good partial response who otherwise satisfied the 2-year treatment success definition. By this measure, the 29.4% (95% CI: 19.0-41.7%) in the two- drug arm did not differ from the 22.4% (95% CI: 12.5- 35.3%) in the three-drug arm (P=0.37).
To address whether certain categories of chronic GvHD responded differently in the study arms overall, in univari- ate analysis, we compared subjects with mild, moderate and severe chronic GvHD, and de novo, quiescent onset and progressive chronic GvHD. There were no statistical- ly significant differences between these groups in terms of the odds of treatment success at 6 months or 2 years. Similarly, no particular individual organ involvement was more likely to be associated with treatment success using either treatment regimen.
The overall survival rate at 2 years was 81.5% in the group treated with two drugs versus 74% in the group treated with three drugs (P=0.28) (Figure 2A). Progression- free survival rates were 78.6% with two drugs versus 67.3% with three drugs (P=0.14) (Figure 2B) and the 2- year failure-free survival rates were 48.6% with two drugs versus 46.2% with three drugs (P=0.78) (Figure 2C,D). The cumulative incidence of relapse (10.1% versus 14.9%,
Table 1. Demographic and hematopoietic cell transplant characteristics.
P=0.40), non-relapse mortality (5.6% versus 11.1%, P=0.26), and the cumulative incidence of secondary immunosuppressive therapy (38.5% versus 29.4%, P=0.22) were not different between the groups treated with two or three drugs. By 2 years, 13 deaths had occurred in the two-drug arm and 16 in the three-drug arm (Online Supplementary Table S1). Almost one-third of deaths were due to GvHD (30.8% in the prednisone/sirolimus group versus 31.3% in the pred- nisone/sirolimus/CNI group). Recurrent or progressive malignancy was the primary cause of death in 30.8% of the prednisone/sirolimus group versus 12.5% in the pred- nisone/sirolimus/CNI group (P=0.36). There were two deaths (15.4%) primarily from infection in the two-drug arm and three (18.8%) in the three-drug arm.
Curves depicting cumulative incidence of discontinuation of systemic immunosuppressive therapy by 2 years over- lapped, with the values at 2 years being 23.2% in the two- drug arm and 20% in the three-drug arm (P=0.71) (Figure 3). Mean (standard deviation) daily glucocorticoid doses (mg/kg) at baseline were 0.9 (0.4) for the group given pred- nisone/sirolimus versus 0.8 (0.2) for the group given pred- nisone/sirolimus/CNI (P=0.13). From baseline to 1 year the mean (standard deviation) daily dose reduction was 0.7 mg/kg (0.3) for the prednisone/sirolimus group and 0.5 mg/kg (0.5) for the prednisone/sirolimus/CNI group.
Gender Female Male
Ethnicity
Hispanic or Latino
Not Hispanic or Latino Unknown/not answered
Race
White
Non-white Unknown/not answered
Age, years Median <20
≥20
Primary disease Acute leukemia Chronic leukemia MDS/MPS Lymphoma Other
Disease stage Early Intermediate High risk
Stem cell type
Bone marrow (BM)
Peripheral blood stem cells (PBSC) Cord blood
Donor source (for BM/PBSC) Related
Unrelated
Type of conditioning regimen Myeloablative
Non-myeloablative or reduced intensity
24 (33.3) 48 (66.7)
8 (11.1) 63 (87.5) 1 (1.4)
54 (75.0) 13 (18.1) 5 (6.9)
50.2
5 (6.9) 67 (92.1)
47 (65.3) 7 (9.7) 12 (16.7) 5 (6.9) 1 (1.4)
46 (63.9) 11 (15.3) 15 (20.8)
5 (6.9) 64 (88.9) 3 (4.2)
29 (42.0)
40 (58.0)
47 (65.3) 25 (34.7)
33 (50.0) 33 (50.0)
0 (0.0) 59 (89.4) 7 (10.6)
57 (86.4) 9 (13.6) 0 (0.0)
54.7
2 (3.0) 64 (97.0)
25 (37.9) 8 (12.1) 9 (13.6) 17 (25.8) 7 (10.6)
27 (40.9) 21 (31.8) 18 (27.3)
5 (7.6) 60 (90.9) 1 (1.5)
38 (58.5)
27 (41.5)
29 (43.9) 37 (56.1)
continued from the previous column
GvHD prophylaxis after transplant CNI + methotrexate ± other CNI + MMF
CNI + MMF ± Other CNI+MMF+ATG
CNI + sirolimus
CNI + corticosteroids CNI only
Other regimen
Donor age, years Mean (SD) Median
Donor age, years <20
20-40 41-60 >60
Donor gender Female Male Unknown
Donor recipient gender mismatch Female-female
Female-male
Male-female
Male-male
Two drugs
N=72(%) N=66(%)
Two drugs Three drugs N=72(%) N=66(%)
Three drugs
44 (61.0) 9 (12.5) 5 (6.9) 0 (0.0) 3 (4.2) 2 (2.8) 5 (6.9) 4 (5.6)
38.5 (12.9) 38.8
3 (4.8) 31 (50.0) 24 (38.7) 4 (6.5)
35 (48.6) 37 (51.4) 0 (0.0)
14 (19.4) 21 (29.2) 10 (13.9) 27 (37.5)
22 (33.3) 15 (22.7) 7 (10.6) 1 (1.5) 5 (7.6) 0 (0.0) 5 (7.6) 11 (16.7)
44.4 (15.2) 47.0
4 (6.6) 21 (34.4) 27 (44.3) 9 (14.8)
26 (39.4) 38 (57.6) 2 (3.0)
10 (15.6) 16 (25.0) 21 (32.8) 17 (26.6)
Two drugs: prednisone/sirolimus, Three drug: prednisone/sirolimus/calcineurin-inhibitor; MDS/MPS: myelodysplastic syndrome/myeloproliferative syndrome; BM: bone marrow; PBSC: peripheral blood stem cells; CNI: calcineurin inhibitor; MMF: mycophenolate mofetil; ATG: anti- thymocyte globulin; GvHD: graft-versus-host disease; SD: standard deviation.
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Biomarkers
Correlative biology studies were attempted using a pre- specified analysis of plasma B-cell activating factor (BAFF) levels determined by enyme-linked immunosorbent assay, and CD3+CD4+CD35+CD127– Treg and CD19+ B- cell enumeration in blood by flow cytometry. Data were available for 99% of patients at baseline, 86% at 60 days and 76% at 180 days after beginning study therapy. Median Treg levels (cells per microliter) in both arms were identical, 26, at baseline (P=0.96), and were lower, 18, at day 60 (P=0.87). At day 180 after starting study therapy, the median Treg number was higher in the group treated with two drugs, 21 (range, 0-68) than in the group treated with three drugs 14.5 (range, 1-239) (P=0.04), but there was no significant difference in Treg: conventional
T-cell (Tcon) ratios. Treatment success at day 180, irre- spectively of treatment arm, was associated with signifi- cantly higher median Treg levels at day 60, 21 (range, 2- 78) versus 10 (range, 1-53) among those with treatment failure (P=0.006). This trend attenuated at day 180 (20 ver- sus 16, P=0.14). Similarly, Treg:Tcon ratios at baseline and day 60 were higher among patients in whom treatment was a success than among those in whom it failed (data not shown).
B-cell numbers were not significantly different between arms, except at day 180 when the median B-cell number (cells per microliter) was higher in the two-drug arm, 148 (range, 0-1547) than in the three-drgu arm, 68 (range, 0- 1035) (P=0.045). Overall, median plasma BAFF levels were low (1.0 – 1.9 ng/mL) at all time-points, potentially
AB
CD
Figure 2. Overall survival, progression-free survival, and failure-free survival. (A) Probability of overall survival by treatment arm (P=0.281). (B) Probability of progres- sion-free survival by treatment arm (P=0.142). Progression-free survival was defined as no clinical evidence of progression or relapsed disease, or any therapy used to treat persistent, progressive, or relapsed disease including withdrawal of immunosuppressive therapy or donor lymphocyte infusion. (C) Probability of failure-free survival in the (C) sirolimus + prednisone (2-drug) arm and (D) control (3-drug) arm. Failure-free survival was defined by the absence of secondary immunosuppres- sive therapy for chronic graft-versus-host disease, non-relapse mortality, and recurrent or progressive malignancy during treatment. Note: the numbers shown are estimates at each time point for each endpoint. Siro/Pred: sirolimus + prednisone; NRM: non-relapse mortality; FFS: failure-free survival.
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Table 2. Chronic graft-versus-host disease characteristics.
continued from the previous column
Two drugsa Three drugs N=72(%) N=66(%)
Two drugsa Three drugs N=72(%) N=66(%)
Time from transplant to enrollment in months, median (range)
Time from diagnosis of chronic GvHD to
enrollment in days, median (range)
Chronic GvHD risk statusa High
Standard
Category of chronic GvHD diagnosis relative to enrollment
Treatment naïveb
Early inadequate respondersc
Chronic GvHD presentation Overlap acute and chronic GvHD Classic chronic GvHD
Chronic GvHDs severityd Mild
Moderate
Severe
Chronic GvHD onset
De-novo
Quiescent Progressive
Skin score 0
1 2 3
Mouth score 0
1 2 3
Gastro-intestinal tract score 0
1 2 3
Eye score 0
1 2 3
Joints and fascia score 0
1 2 3
Genital tract score 0
1 2 3
Lung score 0
1 2 3
Liver score 0
1
7.3 (3.4, 28.6)
7.0 (0.0, 202.0)
37 (51.4) 35 (48.6)
49 (68)
23 (32)
36 (50.0) 36 (50.0)
16 (22.2) 45 (62.5) 11 (15.3)
30 (41.7) 10 (13.9) 32 (44.4)
14 (19.7) 16 (22.5) 22 (31.0) 19 (26.8)
20 (27.8) 31 (43.1) 18 (25.0) 3 (4.2)
40 (56.3) 17 (23.9) 12 (16.9) 2 (2.8)
33 (46.5) 25 (35.2) 9 (12.7) 4 (5.6)
53 (74.6) 10 (14.1) 7 (9.9) 1 (1.4)
43 (89.6) 3 (6.3) 2 (4.2) 0 (0.0)
62 (86.1) 8 (11.1) 1 (1.4) 1 (1.4)
19 (26.4) 14 (19.4)
7.7 (2.5, 42.4)
10.0 (0.0, 310.0)
32 (48.5) 34 (51.5)
36 (54.5)
30 (46.5)
34 (53.1) 30 (46.9)
13 (20.6) 45 (71.4) 5 (7.9)
24 (36.4) 14 (21.2) 28 (42.4)
19 (29.7) 11 (17.2) 20 (31.3) 14 (21.9)
16 (25.0) 26 (40.6) 17 (26.6) 5 (7.8)
33 (51.6) 21 (32.8) 8 (12.5) 2 (3.1)
29 (45.3) 24 (37.5) 10 (15.6) 1 (1.6)
49 (76.6) 11 (17.2) 4 (6.3) 0 (0.0)
28 (73.7) 8 (21.1) 0 (0.0) 2 (5.3)
54 (84.4) 6 (9.4) 3 (4.7) 1 (1.6)
21 (31.8) 23 (34.9)
2 3
Acute GvHD prior to enrollment Yes
No
22 (30.6) 17 (23.6)
42 (58.3)
30 (41.7)
14 (21.2) 8 (12.1)
42 (63.6)
24 (36.4)
continued in the next column
b
nisone ≥0.5 mg/kg/day (or equivalent) at the time of chronic GvHD diagnosis. Treatment-naïve:
newly diagnosed for <14 days. cEarly inadequate responders: previously treated and not responding ≤16 weeks from time of first diagnosis of chronic GvHD.dChronic GvHD severity was defined as per the NIH Consensus criteria.31
because of steroid use,23 and did not differ significantly at day 180 between patients in whom treatment had or had not been successful by day 180. Among patients in whom treatment was successful, the median baseline BAFF lev- els were slightly higher, 1.6 ng/mL (range, 0.2-17.7) versus 1.2 ng/mL (range, 0.1-19.4; P=0.046). BAFF/B-cell ratios were not significantly different between study arms or between patients in whom treatment was or was not suc- cessful.
Quality of life
Health-related quality of life was measured by self- report instruments, including the Functional Assessment of Cancer Therapy Bone Marrow Transplantation (FACT- BMT), Short Form-36 (SF-36). and Lee symptom scale. Figure 4 shows significantly better scores, at 2 and 6 months, with two drugs versus three drugs for the SF-36 Physical Component Summary, adjusted for baseline scores (P=0.02 and P=0.04), and demonstrated further by SF-36 Physical Functioning sub-scores (P=0.007 and P=0.001). Unadjusted, seven-item FACT-BMT Physical Well-Being scores were higher at 2 months with two drugs, but this observation did not hold when adjusted for baseline scores (P=0.27, graph not shown). Lee symptom scale scores did not differ between arms (data not shown).
Toxicity and adverse events
The proportion of patients with grade 3-5 toxicities was similar, 63.9% for those in the two-drug arm versus 56.1% in the three-drug arm. Thrombotic microangiopathy was observed in one patient (1.4%) in the two-drug arm and in three (4.5%) in the three-drug arm. The mean (standard deviation) increase in serum creatinine from baseline to 2 months was significantly higher with three drugs, 0.1 (0.3) mg/dL than with two drugs, 0 (0.2) mg/dL (P=0.002). The proportion of patients with serum creatinine >1.5 times baseline was significantly higher among patients treated with three drugs than among those treated with two drugs at both 2 months (11.7% versus 1.5%, P=0.025), and at 6 months (24.0% versus 7.8%, P=0.016). Twenty-seven subjects in the two-drug arm versus 27 in the three-drug arm (40.9% versus 37.5%, P=0.682) experienced severe to life-threatening/fatal infection episodes with slightly more infection episodes occurring in the three-drug arm (80 ver- sus 52). One patient in the two-drug arm and another three in the three-drug arm developed non-infectious pneumonitis.
Two drugs: prednisone/sirolimus; three drugs: prednisone/sirolimus/calcineurin-inhibitor; GvHD: graft-versus-host disease. aChronic GvHD risk status was defined as high-risk in patients with platelets <100,000,>50% skin involvement,bronchiolitis obliterans or those receiving pred-
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Discussion
In this phase II, multicenter, randomized trial comparing two CNI-free approaches against a CNI-containing com- parator arm, the comparison of two versus three drugs showed similar outcomes with the CNI-free chronic GvHD therapy. Subjects who received prednisone/sirolimus had better renal and physical function at 2 and 6 months, but these improvements did not result in long-term advantages for recipients of the two-drug immunosuppressive therapy. However, between 6 and 12 months, 20%-30% of subjects treated with two drugs and 11%-24% treated with three drugs had already switched to secondary immunosuppres- sive therapy, potentially attenuating longer-term associa- tions. Earlier studies suggested that narrower targeting of CNI and sirolimus blood levels might mitigate nephrotoxi- city.9,25 Data to evaluate this were not collected, but it is con- ceivable that side effects, particularly with three drugs, were partially mitigated by detailed study guidance for managing CNI and sirolimus blood levels.
Our hypothesis was that CNI-free two-drug immuno- suppressive therapy would not impede Treg expansion and would thereby abrogate chronic GvHD better than would three-drug immunosuppressive therapy. The few statistically significant associations that we observed in Treg number and BAFF serum levels were inconsistent and/or difficult to understand suggesting that chronic GvHD biomarker response associations are more complex than Treg alone. Rates of secondary therapy for lack of efficacy between day 90 and day 180 were almost double with two-drug immunosuppressive therapy compared to three-drug therapy, which might have attenuated predict- ed Treg response associations.
We learned important lessons to inform and potentially improve future study design in chronic GvHD. Had phase II been positive, the 51 additionally accrued subjects beyond the phase II target would have jump-started phase III accrual, thereby confirming “built-in” adaptive phase II/III design utility. Second, to begin endpoint review com- mittee adjudications 3 years after enrollment and then dis- cover that 10% of subjects had been ineligible was prob- lematic. For a complex clinical syndrome like chronic GvHD, our fundamental eligibility criterion that required patients to be “diagnosed according to NIH guidelines” was too open to misinterpretation. This problem was resolved after introducing a screening checklist to confirm that patients met the NIH diagnostic criteria for chronic GvHD (Online Supplementary Material). Lastly, a similar problem existed with respect to complete/partial response evaluations. While considerable efforts have been made to standardize and develop more objective chronic GvHD response instruments,26 case report forms for this trial had multiple sections with categorical check boxes and required measures in many organs. The completion of case report forms was inconsistent and has been consid- ered burdensome by others.27 Months of iterative commu- nications between the endpoint review committee, site investigators, and the Data Coordinating Center to clean
Table 3. Treatment success.
Two drugs
Treatment success at 6 months
Three drugs P-value
Treatment successa Yes
(N=72)
35 (48.6%) [95% CI: 36.7%-60.7%]
(N=66)
33 (50.0%) [95% CI: 37.4%-62.6%]
0.871
CR 3 6 PR 32 27
No
Relapse Secondary therapy Death
Not in CR/PR
Treatment successb Yes
37 (51.4%) [95% CI: 39.3%-63.4%] 1
14
4
18
33 (50.0%) [95% CI: 37.4%-62.6%] 3
7
6
17
Treatment success at 2 years
10 (14.7%) [95% CI: 7.3%-25.4%]
9 (15.5%) [95% CI: 7.4%-27.4%]
CRoffIST 3 7 CRonIST 7 2
0.899
No
VGPRc off IST VGPRc on IST PRoffIST PRonIST Progression Relapse Secondary therapy Deathd
Not evaluablee
58 (85.3%) [95% CI: 74.6%-92.7%] 6
4
1
9
1
5
28
4
4
49 (84.5%) [95% CI: 72.6%-92.7%] 1
3
3
7
2
8
18
7
8
Two drugs: prednisone/sirolimus, three drugs: prednisone/sirolimus/calcineurin-inhibitor; aTreatment success at 6 months is defined as a complete (CR) or partial response (PR) without secondary systemic immunosuppressive therapy (IST) and no recurrent malignancy or death through 6 months after randomization.bPartial response is excluded from the definition of treat- ment success at 2 years.cVery good partial response (VGPR) is defined as having trivial residual and asymptomatic graft-versus-host disease features, while on a prednisone dose that is physio- logical or less (defined as ≤5 mg daily or ≤10 mg every other day).This category splits further into truly off all IST (meaning also off sirolimus and/or calcineurin inhibitor or not. dDeath, relapse, and secondary therapy are mutually exclusive, based on which event occurred first. eParticipant withdrew study consent.
Figure 3. Cumulative incidence of discontinuation of all systemic immunosup- pressive therapy without the need to add additional therapy by 2 years.
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data were necessary to enable meaningful analysis. Near real-time monitoring (8-10 weeks after diagnosis) was invoked later by the BMT CTN in an effort to improve the quality of clinically annotated data in a more recent prospective correlative study of serum biomarkers, GvHD and other clinical outcomes.28 These experiences from the 0801 CTN trial also directly informed simplifications implemented in the 2014 revision of the NIH diagnostic and response criteria.29.30
Regardless of treatment arm, success rates at 6 months were only modest; approximately half of all subjects failed to achieve a complete or partial response and remain alive without relapse or receipt of secondary immunosuppres- sive therapy. There were fewer relapses in the two-drug arm, which contained more patients with early stage dis- ease, more with acute leukemia (likely in first remission), and more recipients of myeloablative conditioning. Conceivably these chance imbalances might have resulted
Figure 4. Quality of life. Unadjusted graphs are shown for SF-36 quality of life scores:23 (left) Physical Component Summary scores; (right) Physical Functioning subscale scores.
AB
Figure 5. Six-month landmark analysis. (A) Overall survival after the 6-month landmark with a median follow up for survivors of 30 months. The mortality rates after the 6-month landmark were similar in the complete or partial response group and stable or progressive disease group (hazard ratio, 0.71; 95% confidence interval: 0.17-2.96; P=0.63) or secondary treatment groups (hazard ratio, 0.54; 95% confidence interval: 0.13-2.26; P=0.39), respectively. (B) Cumulative incidence of dis- continuation of immunosuppressive therapy after the 6-month landmark. Patients who died or were lost to follow up or experienced relapse before the landmark were excluded (n=19) and no patients ended immunosuppressive therapy before the landmark. CR/PR: patients with complete or partial response without relapse and without secondary therapy at the time of assessment (n=68). SD/PD/Rx: patients not in complete or partial response and alive without relapse and without sec- ondary therapy at the time of assessment (n=31), and patients who had secondary therapy without relapse regardless of response before the landmark (n=16); IST: immunosuppressive therapy.
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in fewer relapses than in the potentially higher-risk patients who received three drugs. However, our sample size provided insufficient power to be able to detect a dif- ference in relapse. The proportion of subjects who received secondary immunosuppressive therapy in either arm of the trial was not significantly different and it made no difference whether the patient had been enrolled with “newly diagnosed” versus “inadequately responding” chronic GvHD (data not shown).
Two large studies assessed failure-free survival among patients who received non-uniform initial chronic GvHD therapy and showed that the rates of failure-free survival were either similar31 or lower32 to those in our study in the context of overall generally higher rates of moderate and severe chronic GvHD. The Consortium recently evaluated 202 subjects in a landmark analyses to deter- mine whether failure-free survival plus complete/partial responses at either 6 months or 1 year predicted down- stream clinical benefit. At 1 year, the <20% of study sub- jects who satisfied the failure-free survival plus com- plete/partial response end-point versus all other states (failure-free survival with stable/progressive GvHD, or received secondary immunosuppressive therapy) were associated over the subsequent 5 years with significantly fewer GvHD disease manifestations, lower mortality, and earlier discontinuation of immunosuppressive thera- py.33 Because a similar 6-month failure-free survival plus complete/partial response landmark analysis revealed less striking associations with downstream clinical bene- fit, the authors proposed 1-year failure-free survival plus complete/partial responses as the primary endpoint for future pivotal clinical trials of initial therapy. Although 1- year endpoint data were not available, at 6 months our two groups without complete/partial response (i.e. fail- ure-free survival with stable/progressive GvHD, or received secondary immunosuppressive therapy) behaved similarly when analyzed separately. They were, therefore, collapsed into one “stable disease/progressive disease/secondary immunosuppressive therapy” group of 47 patients for comparison to 68 patients with com- plete/partial response who satisfied the failure-free sur- vival endpoint, resulting in just over half the size of the cohort used for the Consortium landmark analysis. Our 6-month failure-free survival plus complete/partial response endpoint predicted earlier time to discontinue immunosuppressive therapy compared to that in the combined group with stable or progressive disease or secondary immunosuppressive therapy (hazard ratio,
2.05; 95% CI: 1.15-3.68; P=0.02) (Figure 5), but similar to the findings of Martin et al.,33 there was no striking sur- vival benefit at 6 months, perhaps because of the shorter follow up and/or the small sample size. Larger prospec- tive studies are needed to verify the utility of this end- point in predicting better survival and shorter duration of immunosuppressive therapy.
In summary, this randomized trial showed no difference in response rates between the two treatment arms. Analyses of nephrotoxicity and quality of life demonstrate that initial therapy of chronic GvHD with prednisone/sirolimus is an acceptable alternative and bet- ter tolerated than three-drug therapy including a CNI. Our study could not address the relative merits of prednisone/sirolimus versus prednisone ± CNI. We were not able to include a prednisone ± CNI treatment arm (cur- rent standard for initial therapy), because the study includ- ed patients with high-risk chronic GvHD or early treat- ment failure. Success rates for prednisone/sirolimus as ini- tial therapy in treatment-naïve or early inadequate respon- ders are insufficient to warrant a randomized controlled trial versus prednisone with or without CNI. For early chronic GvHD therapy, novel approaches that improve rates of complete/parital responses and failure-free sur- vival are required. Given the inherent complexity of chronic GvHD trials, we advise real-time diagnostic checklists to ensure patients’ eligibility, and real-time data auditing to protect data integrity.
Acknowledgments
The authors would like to thank the National Heart, Lung, and Blood Institute and the National Cancer Institute for sup- porting this study (grant #U10HL069294). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. We thank the laboratory of Jerome Ritz for performing all of the immunophenotyping and measuring serum BAFF levels. We thank Saurabh Chhabra, Gregory Yanik, Richard Maziarz, Suhag Parikh, Mark Litzow, Hillard Lazarus, Marcelo Pasquini, Andrew Artz, Krishna Gundabolu, Mark Juckett, Peter Westervelt, Pablo Parker, George Selby, George Chen, John Wingard, Scott Rowley, Scott Solomon, David Porter, Carlos Bachier, Paul Shaughnessy, James Essell, Marcie Riches, Thomas Shea, Michael Pulsipher, Edward Ball, John McCarty, Samantha Jaglowski, Guenther Koehne, and John Lister for enrolling patients on this trial. We thank the members of the Blood and Marrow Transplant Clinical Trials Network, the research nurses, and the patients who participated in this trial.
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13. Jacobsohn DA, Chen AR, Zahurak M, et al. Phase II study of pentostatin in patients with corticosteroid-refractory chronic graft-ver- sus-host disease. J Clin Oncol. 2007;25(27): 4255-4261.
14. Zeiser R, Nguyen VH, Beilhack A, et al. Inhibition of CD4+CD25+ regulatory T-cell function by calcineurin-dependent inter- leukin-2 production. Blood. 2006;108(1): 390-399.
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N-linked glycosylation modulates
the immunogenicity of recombinant human factor VIII in hemophilia A mice
Ferrata Storti Foundation
Jesse D. Lai,1 Laura L. Swystun,1 Dominique Cartier,1 Kate Nesbitt,1 Cunjie Zhang,2 Christine Hough,1 James W. Dennis2 and David Lillicrap1
1Department of Pathology & Molecular Medicine, Queen’s University, Kingston and 2Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, ON, Canada
ABSTRACT
Immune responses to factor VIII remain the greatest complication in the treatment of severe hemophilia A. Recent epidemiological evi- dence has highlighted that recombinant factor VIII produced in baby hamster kidney cells is more immunogenic than factor VIII produced in Chinese hamster ovary cells. Glycosylation differences have been hypothesized to influence the immunogenicity of these synthetic con- centrates. In two hemophilia A mouse models, baby hamster kidney cell-derived factor VIII elicited a stronger immune response compared to Chinese hamster ovary cell-derived factor VIII. Furthermore, factor VIII produced in baby hamster kidney cells exhibited accelerated clearance from circulation independent of von Willebrand factor. Lectin and mass spectrometry analysis of total N-linked glycans revealed differences in high-mannose glycans, sialylation, and the occupancy of glycan sites. Factor VIII desialylation did not influence binding to murine splenocytes or dendritic cells, nor surface co-stimulatory molecule expression. We did, however, observe increased levels of immunoglobulin M specific to baby hamster kidney-derived factor VIII in naïve hemophilia A mice. De-N-glycosylation enhanced immunoglobulin M binding, suggesting that N-glycan occupancy masks epitopes. Elevated levels of immunoglobulin M and immunoglobulin G specific to baby hamster kidney-derived factor VIII were also observed in healthy individuals, and de-N-glycosylation increased immunoglobulin G binding. Collectively, our data suggest that factor VIII produced in baby hamster kidney cells is more immunogenic than that produced in Chinese hamster ovary cells, and that incomplete occupancy of N-linked glycosylation sites leads to the formation of immunoglobulin M- and immunoglobulin G- factor VIII immune complexes that contribute to the enhanced clearance and immunogenicity in these mouse models of hemophilia A.
Introduction
The immune response that develops in ~30% of severe hemophilia A (HA) patients remains the most serious complication in factor VIII (FVIII) replacement therapy. Why FVIII-neutralizing antibodies, known as inhibitors, develop in only some patients remains unclear. The type of FVIII concentrate has been proposed as one of the factors that influences the risk of FVIII immunogenicity. Three independ- ent cohort studies have described differences among different recombinant (r) FVIII concentrates, where a 2nd generation full-length rFVIII was associated with a 1.6-fold increase in inhibitor risk compared to 3rd generation products.1-3 Most recently, a fourth retrospective analysis further reported hazard ratios of 2.81 and 1.64 for inhibitor incidence with 2nd and 3rd generation rFVIII, respectively, compared to plas- ma-derived FVIII.4
While these observational studies provide compelling evidence, the mechanistic basis for such findings has only been hypothesized, and not systematically exam- ined.5 The transition from 2nd to 3rd generation rFVIII is based on the removal of human and animal proteins in the production process and final product formulation.
Haematologica 2018 Volume 103(11):1925-1936
Correspondence:
david.lillicrap@queensu.ca
Received: January 11, 2018. Accepted: July 9, 2018. Pre-published: July 12, 2018.
doi:10.3324/haematol.2018.188219
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/11/1925
©2018 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
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ARTICLE
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In the aforementioned studies, 2nd and 3rd generation prod- ucts refer specifically to Kogenate FS© (Bayer) produced in baby hamster kidney cells (BHK; BHK-rFVIII), and Advate© (Shire) produced in Chinese hamster ovary cells (CHO; CHO-rFVIII). In addition, these products differ by a single amino acid (AA) at position 1241 in the FVIII B domain, aspartic acid and glutamic acid, respectively. However, the immunologic relevance of this substitution appears insignificant as AA 1241 is poorly represented in both the major histocompatibility class II-restricted pep- tidome of human monocyte-derived dendritic cells (DCs), and the repertoire of DR15-restricted CD4+ T-cell epi- topes.6,7 Commercial formulations of BHK-rFVIII have very recently been reported to contain a higher presence of protein aggregates, which have previously been shown to be immunogenic.8,9
Another hypothesis proposes that the differential immunogenicity is attributed to post-translational modifi- cation of rFVIII, and specifically to differential glycosyla- tion patterns between BHK- and CHO-rFVIII at the 25 potential N-linked sites.5,10 Glycans have been implicated in FVIII intracellular trafficking and folding, as well as clearance by the asialoglycoprotein receptor and Siglec- 5.11-14 High-mannose glycans have been hypothesized to facilitate the uptake of FVIII via the mannose receptor on DCs and macrophages, however the data have been con- flicting, and the in vivo significance of this interaction is unclear.15,16 Previous non-clinical studies have reported similar, or increased, immunogenicity of BHK-rFVIII com- pared to CHO-rFVIII, as well as a decreased, but statisti- cally insignificant, inhibitory antibody response to degly- cosylated FVIII.17-19 No mechanistic explanation for these differences has been provided.
Here, we used the previously described BHK- and CHO-rFVIII concentrates, Kogenate FS® and Advate®, respectively, and assessed their relative immunogenicities in two complementary murine models of HA. We further characterized the glycosylation profiles of each product, and evaluated their role in the development of the anti- FVIII immune response in these murine models.
Methods
FVIII concentrates
The following human rFVIII concentrates were used: Kogenate FS® (full-length BHK-rFVIII; Bayer, Leverkusen, Germany), Advate® (full-length CHO-rFVIII; Shire, Dublin, Ireland), and Xyntha® (CHO-B-domain deleted (BDD)-rFVIII; Pfizer, New York City, NY, USA). Information on FVIII clearance, antigen/activity assays, deglycosylation, and von Willebrand factor (VWF) binding is available in the Online Supplementary Methods.
Mice
Sex and littermate-matched 8-12 week old C57Bl/6 F8 exon 16 knockout (KO) mice with a human full-length F8 transgene con- taining an R593C point mutation (HA-R593C mice) that is tran- scribed, but for which FVIII protein is undetectable in plasma, were used for preliminary experiments.20 Results were extended using similarly controlled “conventional” C57Bl/6 F8 exon 16 KO mice (HA mice).21 Mice were treated by subcutaneous or tail vein intravenous injection of 6 IU (240 IU/kg; as per manufacturer’s label) of rFVIII biweekly for two weeks. Lipopolysacharride (LPS; 1 mg) was used as an adjuvant with the first FVIII infusion where indicated. HA mice were challenged with 2 IU (80 IU/kg) of rFVIII
using the same regimen. Blood was collected by cardiac puncture in one-tenth volume of 3.2% sodium citrate 28 days after the first administration of FVIII. Mouse experiments were approved by the Queen’s University Animal Care Committee.
Anti-FVIII antibodies and FVIII inhibitor assays
FVIII-specific immunoglobulin G (IgG) titres were quantified by enzyme-linked immunosorbent assay (ELISA) and FVIII inhibitors were measured by a 1-stage FVIII clotting assay using an automated coagulometer (Siemens BCS XP, Berlin, Germany), as previously described.22,23 Where indicated, anti-FVIII IgG was quantified using a standard curve generated using the human anti-FVIII monoclonal antibody, EL14 (provided by Dr. Jan Voorberg, Sanquin Research, Amsterdam, The Netherlands).24 Information on human sample collection is available in the Online Supplementary Methods.
FVIII-specific IgM was assessed by indirect ELISA. rFVIII (1 μg/mL) was adsorbed to Nunc Maxisorp 96-well plates overnight. Samples were diluted 1:20 and incubated for 2 hrs. IgM was detected using horseradish peroxidase (HRP)-conjugated goat anti- mouse or anti-human IgM (Southern Biotech, Birmingham, AL, USA). Bovine serum albumin (BSA)-coated wells were used as controls. Plates were developed for 15 minutes using o-phenylene- diamine (Sigma, St. Louis, MO, USA) and read at 492 nm.
Lectin binding assays
rFVIII products were adsorbed to Maxisorp microtitre plates at 1 mg/mL overnight at 4°C. All products saturated binding at this concentration (Online Supplementary Figure S1). Plates were blocked with 1% BSA in phosphate buffered saline (PBS) + 0.01% Tween-20 for 1 hr, and subsequently incubated with biotinylated lectins (Vector Laboratories, Burlingame, CA, USA) for 30 min. Detection was facilitated using streptavidin-poly-HRP (ThermoFisher Scientific, Waltham, MA, USA) and developed for 5 min. Statistical analysis was performed using the Student t test.
FVIII preparation for mass spectrometry
FVIII samples were desalted on ViVaspin, 50kDa MWCO (Sartorius, Goettingen, Germany) spin columns. 20 mg of protein in 400 ml of 50 mM ammonium bicarbonate was reduced in 10 mM dithiothreitol (DTT) at 60°C for 40 min then alkylated in 25 mM iodoacetamide in darkness for 30 min. The reaction was stopped by the addition of 20 mM DTT in darkness for 40 min. Trypsin at 1:50 ratio was added to the sample and incubated at 37°C overnight.
Glycopeptide analysis by liquid chromatography and tandem mass spectrometry (LC–MS/MS)
Peptides were applied to a nano-HPLC Chip using an Agilent 1200 series microwell-plate autosampler interfaced with a Agilent 6550 Q-TOF MS (Agilent Technologies, Santa Clara, CA, USA). The reverse-phase nano-HPLC Chip (G4240-62002) had a 40 nL enrichment column and a 75 mm x 150 mm separation column packed with 5 mm Zorbax 300SB-C18. The mobile phase was 0.1% formic acid in water (v/v) as solvent A, and 0.1% formic acid in ACN (v/v) as solvent B. The flow rate was 0.3 mL/min with gra- dient schedule; 3% B (0-1 min); 3-40% B (1-90 min); 40-80% B(90- 95 min); 80% B (95-100 min) and 80-3% B (100-105 min).
Mascot search was used to identify proteins and sequence cov- erage. Extracted glycopeptides were identified by Agilent Masshunter Quantitative Analysis software by the presence of hexose and N-acetylhexosamine. Glycan structures were predict- ed for extracted glycopeptides by GlycoMod. Glycan structure by MS/MS and occupancy of consensus N_X_S/T N-glycosylation sites were determined manually.
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Results
BHK-rFVIII is more immunogenic than CHO-rFVIII in mouse models of hemophilia A
While an International Standard exists for determination of the FVIII:C potency of FVIII concentrates (and products are labeled in International Units), there is no standardized method to accurately quantify FVIII:Ag between products.25 Although there are differences in specific coag- ulant activity between commercial preparations (and between different lots of concentrate) (Online Supplementary Figure S2), we dosed rFVIII by the coagulant activity reported by the manufacturer so as to recapitulate clinical practice and the data reported by previous FVIII inhibitor epidemiological studies. To assess the immuno- genic differences between CHO- and BHK-rFVIII, we administered rFVIII subcutaneously or intravenously to HA-R593C mice biweekly (6 IUs; 240 IU/kg per adminis- tration) for two weeks and analyzed plasma on day 28 (Figure 1A). After subcutaneous immunization, we observed a significant increase in the incidence of anti- FVIII IgG antibodies in mice treated with BHK-rFVIII com- pared to CHO-rFVIII 28 days after the initial injection (93.75% vs. 47.3% respectively, P=0.0042; Figure 1B). Further serological analysis showed that the aFVIII IgG titre was also greater when mice were immunized with BHK-rFVIII (Figure 1C). A similar difference was observed in the incidence of all FVIII inhibitory antibodies (93.75% vs. 36.8%, P=0.0003; Figure 1D). However no significant differences were observed in the inhibitory antibody titres (Figure 1E).
To account for the typical biodistribution of FVIII in the bloodstream, we administered rFVIII intravenously with the first injection containing 1 mg of lipopolysaccharide (LPS) as an adjuvant (Figure 1F). We did not observe any significant difference in the incidence of aFVIII IgG between products in these experiments (Figure 1G). However, BHK-rFVIII elicited higher titres of aFVIII IgG (Figure 1H) among FVIII-responders. Analysis of FVIII inhibitory antibodies showed no differences in incidence (Figure 1I) or inhibitor titre (Figure 1J) using this testing protocol.
All mice developed FVIII-specific antibodies by day 28 (Figure 2B), and there were no differences in the titre of FVIII-specific antibodies (Figure 2C). However, mice immunized with BHK-rFVIII exhibited a higher incidence of all FVIII antibodies with an inhibitory titer >1 bethesda unit (BU; 100% vs. 54.5%; Figure 2D), but no difference in the magnitude among FVIII-responders (Figure 2E).
BHK-rFVIII exhibits accelerated clearance that is independent of binding to murine VWF
We next assessed the clearance of rFVIII from the mouse circulation. Following an intravenous infusion of either BHK-rFVIII or CHO-rFVIII at 200 IU/kg in HA mice, plas- ma FVIII:C was measured by chromogenic assay at the indicated time points and normalized to a 5 min post-infu- sion sample. Our results show a significant increase in the clearance rate of BHK-rFVIII compared to CHO-rFVIII (6.22 hrs vs. 9.53 hrs; P=0.02) (Figure 3A).
Given the dominant influence of VWF on FVIII half-life, we assessed whether the rFVIII products exhibit differen- tial binding to endogenous mouse VWF (Figure 3B). FVIII- binding was reported as a function of the amount of FVIII:Ag at each dilution in the assay. These data suggest
that there is no significant difference in the binding to murine VWF between CHO- and BHK-derived rFVIII, and that the differences observed in clearance and immuno- genicity are independent of VWF and may suggest struc- tural moieties, such as post-translational modifications, that facilitate or inhibit cellular uptake.
rFVIII produced in BHK or CHO cell lines contains significantly different glycosylation profiles
Given the differences in clearance and immunogenicity observed in vivo, we next assessed rFVIII glycosylation by using a panel of lectins to detect specific, exposed, carbo- hydrate linkages on CHO- and BHK-rFVIII. CHO-BDD- rFVIII was used as a control, as it lacks all but six of the potential N-linked sites. Multiple lectins specific for simi- lar structures were used to confirm findings, and the medi- an-centered optical absorbance readings were compared between products using the Student t test (Online Supplementary Table S1). These data suggest that BHK- rFVIII has a higher degree of sialylation and fucosylation, and a lower presence of high-mannose glycans compared to CHO-rFVIII (Figure 4A; Principal component analysis Online Supplementary Figure S3). We further confirmed that these glycan differences were conserved across three dif- ferent lots of rFVIII products (Figure 4B).
Table 1. N-linked glycan structures detected across BHK-, CHO-, and CHO-BDD-rFVIII products.
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By LC-MS/MS, we detected 22 of the 25 potential N- linked Asn-X-Ser/Thr consensus sequences, and identified a total of 21 unique glycans (Table 1; for peptide coverage and glycan construction see Online Supplementary Figure S4 and Figure S5). The intensity of glyco-peptides was nor- malized to the area under the curve of non-glycosylated peptides relative to CHO-rFVIII. The predicted N-linked
glycan sites at Asn1001, Asn1005, and Asn1512 were not detected by our methods. At each occupied site, we observed significant heterogeneity in the glycan structures (Figure 5A). We next grouped glycan stuctures into either high-mannose, asialylated, partially sialylated, or fully sia- lylated. In agreement with our lectin binding data, we observed high-mannose glycans at Asn757 and Asn1300
A
BCDE
F
GHI
J
Figure 1. Immunogenic differences between BHK-rFVIII and CHO-rFVIII in HA-R593C mice. (A) Mice were immunized subcutaneously (SC) with 6 IU (0.6 μg; 240 IU/kg) of either BHK- or CHO-rFVIII biweekly for 2 weeks. Blood was collected by cardiac puncture 28 days after the first infusion. Plasma was assessed for (B) the incidence and (C) titre of FVIII-specific IgG, as well as (D) the incidence of inhibitors above 1 and 5 BU and (E) the magnitude of inhibitory activity. (F) Mice were immu- nized intravenously (IV) with 6 IU (0.6 mg; 240 IU/kg) of either BHK- or CHO-rFVIII product twice weekly for 2 weeks. The first infusion contained 1 mg of lipopolysachar- ride. Plasma samples 28 days after the first infusion were assessed for (G) the incidence and (H) titre of FVIII-specific IgG. (I) Comparison of the incidence of inhibitors above 1 BU and the (J) magnitude of inhibitory activity. Horizontal lines and error bars represent the mean and SEM, respectively. Mann-Whitney U and Fisher’s exact test were used where appropriate. *P<0.05; **P<0.01; ***P<0.001. BHK: baby hamster kidney cells; CHO: Chinese hamster ovary cells: rFVIII: recombinant factor VIII; Ig: immunoglobulin; n.s. not significant; BU: bethesda unit.
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in CHO-rFVIII but not in BHK-rFVIII (Figure 5B). Similarly, the sialylation of sub-terminal galactose residues is more complete in BHK-rFVIII as evidenced by a high proportion of fully-sialylated glycans (Figure 5C-E). We did not observe differences in the frequency of fucosylated N- linked glycans between products (data not shown).
Glycosylation of rFVIII does not influence binding to or induction of IFNγ production by splenocytes or splenic dendritic cells in vitro
Glycosylation differences between CHO- and BHK- rFVIII may alter the association of FVIII with different cell types or receptors. To address this, we employed a FVIII binding assay to unsorted splenocytes from rFVIII naïve HA or HA-R593C mice. However, we did not observe sig- nificant differences in the binding of the different rFVIII preparations to these cells (Online Supplementary Figure S6A,B). We further assessed downstream immune responses to rFVIII in naïve mixed lymphocyte popula- tions using an interferon (IFN)γ enzyme-linked immunospot (ELISPOT). Splenocytes were isolated from naïve HA mice or HA-R593C mice and stimulated with the two rFVIII proteins for 48 hr. The number of cells secreting IFNγ did not differ between the two rFVIII con- centrates (Online Supplementary Figure S6C). Since these data suggest that the early rFVIII innate immune responses are similar between HA mice and HA-R593C mice, we used HA-R593C mice for subsequent experiments.
Differential FVIII immunogenicity in hemophilia A mouse models is not explained by differences in sialic acid content
Given that the degree of N-linked sialylation was the greatest source of glycan variation between BHK- and
CHO-rFVIII, we removed the terminal sialic acids from BHK-rFVIII using a2-3,6,8 neuraminidase for 18 hr at 37°C. Desialylation was confirmed by lectin binding assay (Online Supplementary Figure S7A). Desialylated FVIII:C procoagulant function was 62.3% of the control, however, FVIII antigenicity was conserved (Online Supplementary Figure S7B,C). The removal of sialic acid from BHK-rFVIII did not influence the binding to spleno-
+
cytes or CD11c dendritic cells (Figure 6A,B). Considering
the potential immunomodulatory role of sialic acid, we next investigated whether different glycoforms of rFVIII could influence the expression of the co-stimulatory mol- ecules, CD80 and CD86, on naïve or LPS-stimulated splenocytes and DCs. While we observed significant upregulation of both CD80 and CD86 in LPS-stimulated conditions, the removal of sialic acid did not influence surface co-stimulatory molecule expression in either splenocytes or DCs (Figure 6C, D). Similarly, HA-R593C mice treated subcutaneously with BHK-rFVIII or its desia- lylated glycoform, as described above, did not exhibit sig- nificant differences in the incidence or the titre of FVIII- specific IgG (Figure 6E, F).
N-linked glycans prevent binding of non-neutralizing IgM and IgG to rFVIII
We next evaluated the interaction of non-neutralizing IgM and IgG on rFVIII, and the ability of N-linked glycans to regulate this interaction. We found that incubation of naïve HA, or HA-R593C mouse plasma on a FVIII-coated microtitre plate resulted in the increased binding of BHK- rFVIII-specific IgM (Figure 7A,B) relative to CHO-rFVIII. FVIII-specific IgG was not detected (data not shown). Of note, competition through preincubation with other forms of FVIII showed that these IgM molecules are spe-
A
BCDE
Figure 2. Immunogenic differences between BHK- and CHO-rFVIII in HA mice. (A) F8 exon 16 KO HA mice were immunized intravenously (IV) with 6 IU (0.6 mg; 240 IU/kg) of either BHK- or CHO-rFVIII biweekly for 2 weeks. Blood was collected by cardiac puncture 28 days after the first infusion, and plasma was isolated by cen- trifugation. Samples were assessed for (B) incidence and (C) titres of FVIII-specific IgG. FVIII-responders were analyzed for (D) the incidence (P=0.015) and (E) con- centration of FVIII inhibitors. The horizontal lines and error bars represent the mean and SEM. Mann-Whitney U test and Fisher’s exact test were used where appro- priate. *P<0.05. BHK: baby hamster kidney cells; CHO: Chinese hamster ovary cells: rFVIII: recombinant factor VIII; Ig: immunoglobulin; n.s. not significant; BU: bethesda unit.
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cific to BHK-rFVIII, and that the interaction is not inhibit- ed by human VWF (Figure 7C).
We next evaluated whether N-linked glycans sterically hinder access of IgM to certain epitopes in the FVIII pro- tein backbone. From our MS data, we observed that there were consistently higher proportions of unoccupied N- glycan sites at Asn900, Asn1255, Asn1259, Asn1282, Asn1300, and Asn1810 in BHK-rFVIII compared to CHO- rFVIII (Figure 7D). We subsequently removed all the N- linked glycans from BHK- and CHO-rFVIII using Peptide: N-Glycosidase F (PNGase F), and observed a greater increase in IgM binding to deglycosylated CHO-rFVIII (Figure 7E) when compared to the native rFVIII glycoform.
To extend these findings to humans, we collected plas- ma from healthy human volunteers and quantified levels of FVIII-specific IgM. We observed an increased binding of IgM to BHK-rFVIII compared to CHO-rFVIII and CHO- BDD-rFVIII (Figure 7F). The presence of FVIII-specific IgG antibodies has previously been reported in healthy indi- viduals.26,27 We generated a standard curve using the recombinant antibody, EL14, which bound equally to rFVIII products (Online Supplementary Figure S8). Upon incubation with plasma from healthy human subjects, we observed that a higher proportion of human IgG bound to BHK-rFVIII compared to CHO-rFVIII (Figure 7G). We fur- ther determined that this binding was enhanced when the N-glycans were removed from rFVIII (Figure 7H).
Discussion
Factor VIII immunogenicity remains a significant con- cern among hemophilia treaters, and mounting evidence suggests that rFVIII products differ from pdFVIII concen- trates as well as among themselves. Non-human cell lines have been shown to add immunogenic non-human glycan structures, Gal(a1-3)Galβ1-GlcNAc-R (aGal) and 5-gly- colylneuraminic acid (Neu5Gc) to rFVIII.28,29 In two murine models of HA, in which both non-human glycans are present, we found that BHK-rFVIII was more immuno- genic than CHO-rFVIII. These data suggest that although Neu5Gc and aGal have the potential to induce FVIII immunity in humans, as seen with the immune responses against cetuximab, there are additional mechanisms that contribute to this response.30,31
As per its routine clinical use, mice were dosed by the procoagulant activity of rFVIII. However, the level of inac- tive FVIII protein in the commercial concentrates likely plays a role in immunogenicity. BHK-rFVIII has been reported to have higher FVIII:C and FVIII:Ag than adver- tised.32 We were unable to observe a similar trend across four lots of rFVIII, perhaps due to different methodologies used. High-dose intensive FVIII treatment has been impli- cated as a risk factor for inhibitor development, however this correlation is likely facilitated by the inflammatory milieu of concurrent surgery or bleeding.33 Whether expo-
A
Figure 3. Characterization of FVIII half-life and VWF binding in hemophilia A mice. (A) HA mice were intravenously infused with 200 IU/kg of either BHK-rFVIII or CHO cell line-derived rFVIII. FVIII activity was measured by chromogenic assay, and normalized to a 5 min time point post-injection. Data are repre- sentative of the aggregate data of 3 independent experiments totalling at least 5 biological replicates per time point and 2 lots of each rFVIII product. Error bars represent SEM. (B) Murine VWF from HA mouse pooled plasma was captured on a microtitre plate coated with a polyclonal rabbit anti-human VWF antibody. Increasing concentrations of either BHK-derived, or CHO-derived rFVIII were incubated with the captured VWF and detected using a polyclonal sheep anti-human FVIII antibody. Data shown is one technical replicate representative of 3 inde- pendent experiments. BHK: baby hamster kidney cells; CHO: Chinese hamster ovary cells; rFVIII: recombinant factor VIII.
P=0.02
B
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sure to greater amounts of FVIII protein accounts for the increase in immunogenicity in a non-inflammatory steady state is unclear. Consistent with our data, Delignat et al. standardized FVIII:Ag between products using human plasma, and observed enhanced immunogenicity of BHK- rFVIII compared to CHO-rFVIII in HA mice.18
The immunogenic disparity between rFVIII concen- trates was greatest when administered subcutaneously in HA-R593C mice. In F8 exon 16 KO HA mice, central tol- erance for human FVIII is limited, which may explain why differences between very similar proteins are not as appar- ent in this mouse model.34 In humanized F8 exon 16 KO HA-R593C mice, immunological tolerance to human FVIII necessitates an adjuvant to elicit an immune response via intravenous administration, which may result in a general heightened immune reactivity against all antigens, thus preventing the resolution of subtle immunogenic differ- ences.20 Of note, there are major differences in the biodis- tribution of FVIII when administered intravenously, where it complexes with murine VWF and predominantly localizes in the liver and spleen, versus subcutaneous deliv- ery, where VWF association is less likely, and FVIII local- izes to the draining lymph node.35 This likely directs FVIII to different populations of phagocytic cells, particularly DCs and macrophages.36
The removal of FVIII from circulation can lead to clear- ance and/or antigen presentation. Even in the dominating
presence of endogenous murine VWF, BHK-rFVIII was cleared at an accelerated rate, independent of differences in VWF-binding under static conditions. This difference in half-life has not been described in human patients, and may only be apparent in this mouse model due to inter- species differences in the mechanisms of FVIII and VWF clearance. In this scenario, assuming that FVIII does not influence VWF clearance to a significant extent, it is possi- ble that the ~5% of BHK-rFVIII that circulates without VWF is cleared faster, thus shifting the equilibrium to pro- mote further FVIII dissociation from VWF.37 We hypothe- sized that post-translational structures could contribute to the different clearance kinetics of these proteins in mice.
Our analysis of rFVIII glycans confirms the findings of previous studies: that rFVIII possesses predominantly core-fucosylated biantennary complex glycans, a heavily sialylated B domain, high mannose glycans at Asn239 and Asn2118, and unoccupied sites at Asn582, Asn943, Asn1384, and Asn1685.28,38,39 Contrary to previous studies, we did not detect tetraantennary glycans or Neu5Gc gly- cans (aGal cannot be detected directly using our meth- ods). Lectin binding analysis of exposed N- and O-linked glycans and mass spectrometry analysis of total N-linked glycans collectively showed differences in sialic acid and high-mannose glycan content. A similar analysis showed an absence of high mannose glycans as well as greater sia- lylation in CHO-derived rFVII compared to that produced
AB
Figure 4. Lectin array analysis of exposed glycans on rFVIII products. rFVIII products were adsorbed on microtitre plates at 1 mg/mL and assessed using a panel of biotinylated lectins. BSA was adsorbed as a control. Binding was detected using a streptavidin poly-HRP and read at 492 nm. (A) Heat plot demonstrating the medi- an-centred binding values of lectins with varying carbohydrate specificites to different rFVIII products. Values shown are representative of the mean of at least 3 inde- pendent experiments on a single lot of each rFVIII product. Statistical summary available in Online Supplementary Table S1. (B) Lectin binding analysis of different production lots of full-length rFVIII from CHO or BHK cells. Data are representative of at least 3 independent experiments. BHK: baby hamster kidney cells; CHO: Chinese hamster ovary cells: rFVIII: recombinant factor VIII; BSA: bovine serum albumin; BDD: B-domain deleted.
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in BHK cells, suggesting that differences in glycan profiles may be protein-specific.40
Given the conflicting evidence relating to the role of mannosylation on FVIII immunity, and the high abun- dance of endogenous high-mannose glycans on other plas- ma proteins that do not exhibit similar immunogenic responses, we assessed sialic acid as a regulator of FVIII immunogenicity.15,16,41 N-glycans on BHK-rFVIII exhibited greater sialylation, which considering our clearance data, is in contrast to previously reported influences of sialic acid on FVIII and VWF half-life.42 The inhibition of com-
plex glycan formation has been shown to increase the spe- cific activity of FVIII, suggesting that the enhanced nega- tive charge due to increased sialic acid may alter the affini- ties between BHK-rFVIII and its interacting coagulant partners.43 While the influence of the FVIII procoagulant activity on immunogenicity remains a subject of debate, the increased negative charge associated with enhanced sialylation may modulate clearance receptor binding.44,45
Sialic acid can signal through inhibitory receptors such as Siglec-5, or the activating homolog Siglec-14, which have nearly identical binding motifs.14,46 In our study, we
A
B
C
E
D
Figure 5. Comparative N-linked glycosylation of different rFVIII products by LC-MS/MS. (A) Heat plot representing the proportion of each of the detected glycans at each N-linked consensus sequence across different rFVIII products. Sites portrayed with an X were not detected in the analyses. Glycan structures are denoted as additions to the core (Man3GlcNAc2-Asn) where H=hexose, N=GlcNAc, F=fucose, S=sialic acid. (B) High-mannose, (C) asialylated, (D) partially sialylated, and (E) fully sialylated N-linked glycans presented as a proportion of the total occupied glycans. Amino acid numbering for N-linked Asn glycosylation sites does not include the 19 amino acid signal peptide. Each rFVIII product was analyzed at least twice, including an initial assessment of sample quality. BHK: baby hamster kidney cells; CHO: Chinese hamster ovary cells; rFVIII: recombinant factor VIII; BDD: B-domain deleted.
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observed no difference in the binding of BHK- or CHO- rFVIII to naïve splenocytes or DCs. Moreover, the removal of a2-3, and a2-6 sialic acids did not significantly influ- ence cellular binding or modulation of surface co-stimula- tory molecule responses in vitro, and did not influence the immunogenicity of BHK-rFVIII in mice. In fact, the FVIII immune response was attenuated when exposed to desia- lylated BHK-rFVIII compared to exposure to unmodified rFVIII, potentially due to desialylated BHK-rFVIII behav- ing as a unique antigen.47 Although the antigenicity of desialylated rFVIII was not altered as determined by
A
ELISA, the decrease in FVIII:C activity suggests an alter- ation of global tertiary structure that may influence FVIII immunogenicity.
Interactions between FVIII and its plasma binding part- ners may regulate its association with endocytic cells in the liver and spleen. We observed increased binding to BHK-rFVIII by non-neutralizing IgM in the plasma of naïve HA and HA-R593C mice as well as by non-neutral- izing IgM and IgG from healthy human subjects. The presence of mouse and human VWF in these experiments suggests that these immune complexes can form in the cir-
B
CD
Figure 6. Sialic acid does not alter FVIII binding to, and matu- ration of splenocytes and den- dritic cells in vitro, and does not modulate the FVIII immune response in vivo. Desialylated and control rFVIII were incubated with FVIII naïve splenocytes for 1 hr at 4°C and assessed for bind- ing by flow cytometry. Cells were gated as total (A) splenocytes or (B) CD11c+ dendritic cells (DCs). rFVIII association with DCs was quantified as the proportion of FVIII+CD11c+ out of all CD11c+ cells. Flow cytometry characteri- zation of the surface co-stimula- tory molecules, CD80 and CD86, were performed on (C) spleno- cytes and (D) CD11c+ DCs incu- bated for 24 hr under the indicat- ed conditions (1 mg/mL LPS or rFVIII; n=4). HA-R593C mice were administered 1 mg of rFVIII and its desialylated glycoform subcu- taneously biweekly for 2 weeks. Plasma samples 28 days after the initial infusion were assessed for (E) the incidence of FVIII-spe- cific IgG and (F) the titre of the anti-FVIII IgG response. Line and error bars represent mean and SEM respectively. Data represen- tative of at least 3 independent deglycosylation reactions. **P<0.01; ***P<0.001. MFI: mean fluorescence intensity; rFVIII: recombinant factor VIII; Ig: immunoglobulin; n.s. not signifi- cant.
EF
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ABC
DE
FGH
Figure 7. FVIII-specific IgM and IgG in naïve HA mice and healthy humans bind preferentially to BHK-rFVIII. FVIII-specific IgM was detected by indirect ELISA using plasma from naïve (A) HA-R593C mice and (B) HA mice. (C) Competition assay in which the specificity of these IgM antibodies for BHK-rFVIII was assessed by a 30 min preincubation with either other rFVIII concentrates, or human pdVWF (n=3). (D) Glycan occupancy at each N-linked Asn consensus sequence derived from LC- MS/MS analysis. (E) Murine IgM binding to deglycosylated rFVIII products (n=7). (F) FVIII-binding of IgM isolated from healthy humans. (G) Binding of IgG from healthy human plasma to different rFVIII products. (H) Binding of IgG from healthy human plasma to de-N-glycosylated BHK-rFVIII. Line and error bars represent mean and SEM respectively. The Wilcoxon test was used for paired statistical analysis. *P<0.05; **P<0.01; ***P<0.001. BHK: baby hamster kidney cells; CHO: Chinese ham- ster ovary cells; rFVIII: recombinant factor VIII; BDD: B-domain deleted; Ig: immunoglobulin; PNGaseF: Peptide: N-Glycosidase F.
culation in the presence of the protective effect of VWF.48 N-linked glycans may result in steric hindrance to prevent Ig binding. Indeed, removal of N-linked glycans from BHK- and CHO-rFVIII increased IgM binding to a greater extent in the latter, suggesting that glycans on CHO-rFVIII better mask underlying epitopes.
These rFVIII immune complexes may provide an expla- nation for the enhanced immunogenicity documented with BHK-rFVIII through fragment crystallizable (Fc)- mediated uptake by DCs.49 The binding of IgM to antigens further facilitates the binding of mannose-binding lectin, and both can trigger the deposition of complement that greatly increases the binding potential of FVIII to endocyt- ic receptors.50 These data therefore support the observa- tion of increased clearance and immunogenicity of BHK- rFVIII. The presence of FVIII-specific IgM in rFVIII naïve HA mice, and both IgM and IgG in healthy individuals, suggests an innately immunogenic property of FVIII.
Previous studies have reported anti-FVIII antibodies in up to 19% of healthy subjects.26,27,51 These autoantibodies have been mapped to several regions in the FVIII heavy chain, and a single region in the A3 domain of the FVIII light chain.51 Complete glycosylation of the partially occu- pied sites described herein may inhibit these initial immune complexes from forming. Although these anti- rFVIII Igs likely possess low binding affinities, the avidity of IgM binding, in addition to IgG binding, may compen- sate and contribute to cellular uptake of FVIII immune complexes leading to either clearance or antigen presenta- tion.52,53
In this study, our data suggest that N-linked glycans shield underlying FVIII epitopes. We propose that the increased immunogenicity of BHK-rFVIII shown in two murine models of hemophilia A and four separate epi- demiological studies is, in part, related to incomplete N- linked glycosylation that exposes immunogenic epitopes
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to FVIII-specific IgM and IgG, that may, in turn, facilitate the formation of immune complexes in the circulation. Collectively, our studies provide an additional biological complement to evidence presented in recent epidemio- logical investigations showing that 2nd generation BHK- rFVIII is more immunogenic than 3rd generation CHO- rFVIII.
Funding
This work was supported by an Operating and Foundation Grant from the Canadian Institutes of Health Research (MOP-10912, FDN-154285), GlycoNet, and from the Canadian Hemophilia Society. JDL is supported in part by an Ontario Graduate Scholarship and the Franklin Bracken Fellowship. and DL is the recipient of a Canada Research Chair in Molecular Hemostasis.
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