Chronic myeloid leukemia (CML) is a hematopoietic malignancy characterized by a (9;22) translocation, which generates the constitutively active BCR-ABL tyrosine kinase. BCR-ABL is the critical mediator of disease pathogenesis, exhibiting constitutive kinase activity that drives survival and proliferation through multiple downstream pathways. First-line therapy with the ABL kinase inhibitor imatinib leads to durable responses in the majority of patients with CML, although a substantial number of patients develop resistance to therapy. The second-generation ABL inhibitors nilotinib and dasatinib have proven largely effective as salvage therapies in this clinical scenario. However, the "gatekeeper" BCR-ABLT315I mutant is insensitive to all three approved drugs, and new ABLT315I inhibitors are in development. Recent clinical reports suggest that sequential ABL tyrosine kinase inhibitor therapy may select for BCR-ABLT315I-inclusive compound mutants (two mutations within the same BCR-ABL molecule) that confer high-level resistance. A cell-based screen will be used to identify BCR-ABL compound mutations that confer resistance to ABLT315I inhibitors, and strategies to minimize emergence of compound mutants will be explored. A second subset of patients exhibits disease progression via a BCR-ABL-independent, "oncogene switching" mechanism, and the molecular events leading to this phenomenon remain unidentified. To better understand this process, the combination of functional screens using panels of siRNA and kinase inhibitors with high-throughput sequencing and microarray analysis will accelerate the identification of molecular mechanisms of BCR-ABL-independent resistance. To gain a more complete understanding of how to maximize efficacy of ABL kinase-inhibitor-based therapy, it is important to determine the molecular mechanism and kinetics by which these inhibitors commit CML cells to undergo apoptosis. The surprising clinical observation that dasatinib is effective in vivo despite only transient inhibition of BCR-ABL kinase activity challenges the dogma that kinase inhibitor efficacy is predicated on continual target inhibition. A detailed investigation of the core requirements for an ABL kinase inhibitor to irrevocably commit BCR-ABL-positive cells to apoptosis in CML will shed light on this process. Finally, further insight into the regulation of ABL kinase activity in the context of the multimeric oncogenic kinase BCR-ABL will be critical to improvements in our understanding of the biology and treatment of CML. We will apply a systematic approach to generate, screen, and pursue BCR-ABL protein constructs that are candidates for x-ray crystallography. Structural studies would enhance our understanding of the structural basis for activation and regulation of this oncogenic kinase. Thus, this proposal centers on: 1) elucidation of resistance mechanisms in CML, 2) identification of critical apoptosis commitment pathways associated with tyrosine kinase inhibitor sensitivity, and 3) improving our understanding of the regulation of kinase activity of BCR-ABL. This knowledge will inform and improve the disease management for patients with CML and other malignancies.

Public Health Relevance

Targeted therapy for chronic myeloid leukemia (CML) with imatinib (Gleevec) has dramatically altered the prognosis for patients with this disease, but resistance to imatinib occurs in some patients. The proposed studies will improve our understanding and ability to control resistance, aid in the design of novel therapies by better understanding how cells are killed by imatinib, and provide insight into how the target of imatinib causes the growth of leukemia cells. Together, these findings will have important implications for the treatment of CML and for the use of targeted therapies in many other cancers.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Method to Extend Research in Time (MERIT) Award (R37)
Project #
5R37CA065823-18
Application #
8444282
Study Section
Cancer Molecular Pathobiology Study Section (CAMP)
Program Officer
Mufson, R Allan
Project Start
1995-07-01
Project End
2016-02-29
Budget Start
2013-03-01
Budget End
2014-02-28
Support Year
18
Fiscal Year
2013
Total Cost
$291,676
Indirect Cost
$102,276
Name
Oregon Health and Science University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
096997515
City
Portland
State
OR
Country
United States
Zip Code
97239
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Ma, Leyuan; Shan, Yi; Bai, Robert et al. (2014) A therapeutically targetable mechanism of BCR-ABL-independent imatinib resistance in chronic myeloid leukemia. Sci Transl Med 6:252ra121
Khorashad, Jamshid S; Kelley, Todd W; Szankasi, Philippe et al. (2013) BCR-ABL1 compound mutations in tyrosine kinase inhibitor-resistant CML: frequency and clonal relationships. Blood 121:489-98
O'Hare, Thomas; Eide, Christopher A; Agarwal, Anupriya et al. (2013) Threshold levels of ABL tyrosine kinase inhibitors retained in chronic myeloid leukemia cells determine their commitment to apoptosis. Cancer Res 73:3356-70
Traer, E; MacKenzie, R; Snead, J et al. (2012) Blockade of JAK2-mediated extrinsic survival signals restores sensitivity of CML cells to ABL inhibitors. Leukemia 26:1140-3
O'Hare, Thomas; Deininger, Michael W N; Eide, Christopher A et al. (2011) Targeting the BCR-ABL signaling pathway in therapy-resistant Philadelphia chromosome-positive leukemia. Clin Cancer Res 17:212-21
Eide, Christopher A; Adrian, Lauren T; Tyner, Jeffrey W et al. (2011) The ABL switch control inhibitor DCC-2036 is active against the chronic myeloid leukemia mutant BCR-ABLT315I and exhibits a narrow resistance profile. Cancer Res 71:3189-95
O'Hare, Thomas; Zabriskie, Matthew S; Eide, Christopher A et al. (2011) The BCR-ABL35INS insertion/truncation mutant is kinase-inactive and does not contribute to tyrosine kinase inhibitor resistance in chronic myeloid leukemia. Blood 118:5250-4
Packer, Leisl M; Rana, Sareena; Hayward, Robert et al. (2011) Nilotinib and MEK inhibitors induce synthetic lethality through paradoxical activation of RAF in drug-resistant chronic myeloid leukemia. Cancer Cell 20:715-27
Hurtz, Christian; Hatzi, Katerina; Cerchietti, Leandro et al. (2011) BCL6-mediated repression of p53 is critical for leukemia stem cell survival in chronic myeloid leukemia. J Exp Med 208:2163-74

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