Abstract P106: SELECTIVE CYTOTOXICITY IN KRAS-MUTANT CANCER CELLS THROUGH COORDINATED STABILIZATION OF KRAS AND ITS UPSTREAM REGULATORS USING SMALL MOLECULE DRUG

Abstract

KRAS is one of the most frequently mutated oncogenes in cancer, driving tumorigenesis and resistance to therapy. However, its smooth, shallow surface and lack of deep binding pockets have historically made it difficult to target with small molecules. Our lab identified Merodantoin (C1), a small molecule that selectively induces cell death in KRAS-mutant cancer cells by hyperactivating KRAS. This activation leads to stimulation of the mTORC2–AKT signalling pathway, elevated reactive oxygen species (ROS) levels, and subsequent cell death via mitochondrial fission and mitophagy. To further elucidate the upstream mechanisms underlying KRAS hyperactivation, we employed mass spectrometry- and Western blot-based Cellular Thermal Shift Assays (MS-CETSA and WB-CETSA). In KRAS G13D mutant cells, C1 treatment resulted in thermal stabilization of KRAS, its upstream adaptor GRB2, and the prenylation enzymes Farnesyltransferase-α/β, which are essential for KRAS membrane localization and function. Functional knockdown studies showed that GRB2 silencing partially rescued both C1-induced cytotoxicity and impaired spheroid formation, suggesting a contributory—but not exclusive—role in modulating the KRAS-driven response. In KRAS wild-type cells, C1 induced minimal cell death and exhibited stability in GRB2 but not KRAS. Autophagy-inducing treatments (Rapamycin, EBSS) stabilized KRAS in mutant cells but not GRB2, and neither protein in wild-type cells, indicating that KRAS stabilization is mutation-dependent, while GRB2 stabilization is specific to C1. These results suggest that C1-induced lethality involves coordinated stabilization of multiple upstream KRAS regulators, with GRB2 acting as one component that may amplify signalling in a mutant-specific context. Together, this reveals a novel mechanistic axis of synthetic lethality in KRAS-driven cancers.