Abstract 5509: Breaking the paradox breakers - RAF inhibitor mechanisms

Abstract

Abstract A number of ATP competitive inhibitors of RAF onco-protein have been successful in tumors with RAF V600 mutations but have failed for more common cases with upstream mutations. Instead, a paradoxical activation (PA) of downstream signaling is observed in response to these inhibitors when RAF is not the driver mutation. A detailed understanding of processes that potentiate PA would help in minimizing side effects, choosing appropriate mono- or combination treatments and guide future drug development. Several mechanisms of PA have been proposed in the past, such as negative co-operativity to additional drug binding and RAF dimer stabilization. However, the evidence for these mechanisms is indirect and does not explain PA for all the different types of drugs. In our work, we created a mathematical model of RAF activation solely based on canonical RAF signal regulatory processes to show how autoinhibition provides a general mechanism of PA. We also used this model to show that 14-3-3 proteins could further potentiate PA by stabilizing autoinhibited RAF. Based on the computational work, we predicted that transfecting 14-3-3 proteins would potentiate PA even with drugs which are otherwise expected to provide minimal or no PA. Our experiments with these drugs in SKMEL2 melanoma cells and SW48 colon cancer cells validated our predictions thereby providing support for our general model of PA. Citation Format: Gaurav Mendiratta, Thomas McFall, Edward Stites. Breaking the paradox breakers - RAF inhibitor mechanisms [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 5509.