Abstract 62: Destabilization of NOXA mRNA as a common resistance mechanism to targeted therapies

Abstract

Abstract Most targeted cancer therapies fail to achieve complete tumor regressions or attain durable remissions. To understand why these treatments fail to induce robust cytotoxic responses despite appropriately targeting oncogenic drivers, here we systematically interrogated the dependence of cancer cells on the BCL-2 family of apoptotic proteins after drug treatment. We observe that multiple targeted therapies, including BRAF or EGFR inhibitors, rapidly deplete the pro-apoptotic factor NOXA, thus creating a dependence on the anti-apoptotic protein MCL-1. This adaptation requires a pathway leading to the destabilization of the NOXA mRNA transcript. We find that interruption of this mechanism of anti-apoptotic adaptive resistance dramatically increases cytotoxic responses in cell lines and a murine melanoma model. Durable control of disease in vivo can be achieved with combinations of targeted therapy with an MCL-1 inhibitor. However, consistent with an adaptive resistance mechanism we have identified, the timing of drug treatment strongly influences the efficacy of the combination therapy. Collectively, our results identify NOXA mRNA destabilization/MCL-1 adaptation as a non-genomic mechanism that limits apoptotic responses. Our data indicate that optimal sequencing of MCL-1 inhibitors with targeted therapies could overcome widespread and clinically important therapeutic resistance, and achieve prolonged tumor responses in solid tumors. Citation Format: Joan Montero, Cecile Gstalder, Daniel J. Kim, Dorota Sadowicz, Wayne Miles, Michael Manos, Justin R. Cidado, J. Paul Secrist, Adriana E. Tron, Keith Flaherty, F. Stephen Hodi, Charles H. Yoon, Anthony Letai, David E. Fisher, Rizwan Haq. Destabilization of NOXA mRNA as a common resistance mechanism to targeted therapies [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 62.