Inhibition of BCL2 family members increases the efficacy of copper chelation in BRAFV600E-driven melanoma.
By: Ye-Jin Kim, Tiffany Tsang, Grace R Anderson, Jessica M Posimo, Donita C Brady

Cancer Biology, University of Pennsylvania.
2020-01-27; doi: 10.1158/0008-5472.CAN-19-1784
Abstract

The principal unmet need in BRAFV600E-positive melanoma is lack of an adequate therapeutic strategy capable of overcoming resistance to clinically approved targeted therapies against oncogenic BRAF and/or the downstream MEK1/2 kinases. We previously discovered that copper (Cu) is required for MEK1 and MEK2 activity through a direct Cu-MEK1/2 interaction. Repurposing the clinical Cu chelator tetrathiomolybdate (TTM) is supported by efficacy in BRAFV600E-driven melanoma models, due in part to inhibition of MEK1/2 kinase activity. However, the antineoplastic activity of Cu chelators is cytostatic. Here, we performed high-throughput small molecule screens to identify bioactive compounds that synergize with TTM in BRAFV600E-driven melanoma cells. Genetic perturbation or pharmacological inhibition of specific members of the BCL2 family of anti-apoptotic proteins (BCL-W, BCL-XL, and MCL-1) selectively reduced cell viability when combined with a Cu chelator and induced CASPASE-dependent cell death. Further, in BRAFV600E-positive melanoma cells evolved to be resistant to BRAF and/or MEK1/2 inhibitors, combined treatment with TTM and the clinically evaluated BCL2 inhibitor, ABT-263, restored tumor growth suppression and induced apoptosis. These findings further support Cu chelation as a therapeutic strategy to target oncogene-dependent tumor cell growth and survival by enhancing Cu chelator efficacy with chemical inducers of apoptosis, especially in the context of refractory or relapsed BRAFV600E-driven melanoma.



Copyright ©2020, American Association for Cancer Research.

PMID:32005716






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