Page 85 - 2022_01-Haematologica-web

Acute Myeloid Leukemia
A genome-wide CRISPR screen identifies regulators of MAPK and MTOR pathways that mediate resistance to sorafenib in acute myeloid leukemia
Alisa Damnernsawad,1,2 Daniel Bottomly,3 Stephen E. Kurtz,4 Christopher A. Eide,4 Shannon K. McWeeney,3 Jeffrey W. Tyner1,4 and Tamilla Nechiporuk1
1Department of Cell, Developmental & Cancer Biology, Knight Cancer Institute, Oregon Health & Science University, Portland, OR, USA; 2Department of Biology, Faculty of Science, Mahidol University, Bangkok, Thailand; 3Division of Bioinformatics and Computational Biology, Knight Cancer Institute, Oregon Health & Science University, Portland, OR, USA and 4Division of Hematology and Medical Oncology, Knight Cancer institute, Oregon Health & Science University, Portland, OR, USA
ABSTRACT
Drug resistance impedes the long-term effect of targeted therapies in acute myeloid leukemia (AML), necessitating the identifica- tion of mechanisms underlying resistance. Approximately 25% of AML patients carry FLT3 mutations and develop post-treatment insensitivity to FLT3 inhibitors, including sorafenib. Using a genome- wide CRISPR screen, we identified LZTR1, NF1, TSC1 and TSC2, neg- ative regulators of the MAPK and MTOR pathways, as mediators of resistance to sorafenib. Analyses of ex vivo drug sensitivity assays in samples from patients with FLT3-ITD AML revealed that lower expres- sion of LZTR1, NF1, and TSC2 correlated with sensitivity to sorafenib. Importantly, MAPK and/or MTOR complex 1 (MTORC1) activity was upregulated in AML cells made resistant to several FLT3 inhibitors, including crenolanib, quizartinib, and sorafenib. These cells were sensi- tive to MEK inhibitors, and the combination of FLT3 and MEK inhibitors showed enhanced efficacy, suggesting the effectiveness of such treatment in AML patients with FLT3 mutations and those with resistance to FLT3 inhibitors.
Introduction
Acute myeloid leukemia (AML), a rapidly progressing hematologic malignancy, is caused by the impaired differentiation and subsequent proliferation of hematopoietic progenitor cells. AML is characterized by cytogenetic heterogene- ity and numerous recurrent genetic lesions.1-5 The Fms-related tyrosine kinase 3 (FLT3) receptor tyrosine kinase is normally expressed on hematopoietic stem and progenitor cells and functions in promoting cell proliferation and survival as well as normal development of these cells.6-8 FLT3 activating mutations occur in approximately 25% of AML patients, either by internal tandem duplications (FLT3-ITD) or point mutations in the tyrosine kinase domain,4,9-12 stimulating AML cell proliferation and survival. These mutations are associated with poor out- comes including an enhanced risk of relapse.6,7,13 The high frequency and adverse effects of FLT3 mutations have prompted the development of small-molecule inhibitors targeting FLT3.
Among the FLT3 tyrosine kinase inhibitors that have been developed, several have provided encouraging results in clinical trials,7,14,15 and two in particular, midostaurin and gilteritinib, have been approved for FLT3-mutant AML.16-18 Nevertheless, all the FLT3 inhibitors developed to date lack long-term, durable clinical efficacy because of the development of resistance. Point mutations within the kinase domain of FLT3, such as variants in residues D835 and F691, cause resistance to type II FLT3 inhibitors (quizartinib and sorafenib) in vitro as well as in relapsed/refractory patients.19-21 While patients with tyrosine kinase domain mutations develop resistance to type II inhibitors, they are sensitive to type I
Ferrata Storti Foundation
Haematologica 2022 Volume 107(1):77-85
Correspondence:
TAMILLA NECHIPORUK
nechipot@ohsu.edu
JEFFREY W. TYNER tynerj@ohsu.edu
Received: May 3, 2020.
Accepted: December 21, 2020. Pre-published: December30,2020.
https://doi.org/10.3324/haematol.2020.257964 ©2022 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 | 2022; 107(1)
77
ARTICLE