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Chronic Lymphocytic Leukemia
Non-genotoxic MDM2 inhibition selectively induces a pro-apoptotic p53 gene signature in chronic lymphocytic leukemia cells
Ferrata Storti Foundation
Haematologica 2019 Volume 104(12):2429-2442
Carmela Ciardullo,1 Erhan Aptullahoglu,1 Laura Woodhouse,2 Wei-Yu Lin,1 Jonathan P Wallis,3 Helen Marr,3 Scott Marshall,4 Nick Bown,5 Elaine Willmore1 and John Lunec1
1Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne; 2Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne; 3Department of Haematology, Freeman Hospital, The Newcastle upon Tyne NHS Foundation Trust, Newcastle upon Tyne; 4Department of Haematology, City Hospitals Sunderland NHS Trust, Sunderland and 5Northern Genetics Service, Institute of Genetic Medicine, Newcastle upon Tyne, UK
ABSTRACT
Chronic lymphocytic leukemia (CLL) is a clinically heterogeneous hematologic malignancy. In approximately 90% of cases the TP53 gene is in its wildtype state at diagnosis of this malignancy. As mouse double-minute-2 homolog (MDM2) is a primary repressor of p53, targeting this protein is an attractive therapeutic approach for non-genotox- ic reactivation of p53. Since the discovery of the first MDM2 inhibitor, Nutlin-3a, newer potent and bioavailable compounds have been developed. In this study we tested the second-generation MDM2 inhibitor, RG7388, in patient-derived CLL cells and normal cells, examining its effect on the induction of p53-transcriptional targets. RG7388 potently decreased viabil- ity in p53-functional CLL cells, whereas p53-non-functional samples were more resistant to the drug. RG7388 induced a pro-apoptotic gene expres- sion signature with upregulation of p53-target genes involved in the intrin- sic (PUMA, BAX) and extrinsic (TNFRSF10B, FAS) pathways of apoptosis, as well as MDM2. Only a slight induction of CDKN1A was observed and upregulation of pro-apoptotic genes dominated, indicating that CLL cells are primed for p53-dependent apoptosis. Consequently, RG7388 led to a concentration-dependent increase in caspase-3/7 activity and cleaved poly (ADP-ribose) polymerase. Importantly, we observed a preferential pro- apoptotic signature in CLL cells but not in normal blood and bone marrow cells, including CD34+ hematopoietic cells. These data support the further evaluation of MDM2 inhibitors as a novel additional treatment option for patients with p53-functional CLL.
Introduction
Chronic lymphocytic leukemia (CLL) is the most prevalent B-cell malignancy in adults and is marked by an extremely heterogeneous clinical course.1-3 CLL is char- acterized by a clonal expansion of CD19+CD5+ B cells in the blood, bone marrow and lymphoid tissues.1-3 Malignant B-lymphocytes accumulate partly due to activa- tion of B-cell receptor (BCR) signaling, leading to increased proliferation and inhi- bition of apoptosis.3 In addition to BCR signaling, CLL cells are supported by the tumor microenvironment, including extensive cytokine and chemokine signaling with T cells, myeloid cells, and stromal cells.4-7
Although the use of chemo-immunotherapy and BCR antagonists has improved patients’ response rates to treatment, CLL remains incurable.8,9 The identification of new agents that interfere with the survival of CLL cells by promoting apoptosis of these cells is one important approach to improve therapeutic outcomes.10,11 In fact, several studies have demonstrated that the anti-apoptotic BCL2 protein is highly expressed in CLL and inhibits the activity of pro-apoptotic BH3-only family mem- bers, such as p53-upregulated modulator of apoptosis (PUMA).12-14 Therefore, drugs
Correspondence:
JOHN LUNEC
john.lunec@ncl.ac.uk
Received: October 3, 2018. Accepted: April 16, 2019. Pre-published: April 19, 2019.
doi:10.3324/haematol.2018.206631
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/104/12/2429
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haematologica | 2019; 104(12)
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