Abstract 1669: KRAS G12X mutants display differential preferences in downstream effector binding

Abstract

Abstract KRAS is among the most frequently mutated oncogenic driver proteins in human cancers including lung, colorectal, and pancreatic cancers. Activating KRAS mutants cause increased cell proliferation through direct binding and overactivation of effector proteins. Effector activation preference is driver mutation specific, as KRAS G12D and G12C purportedly bind both RAF and PI3K, whereas G12R has been reported to bind RAF but not PI3K. The mechanisms of effector binding of G12S action are under-investigated. Furthermore, most KRAS mutations remain clinically untreatable, as clinically approved KRAS inhibitors (KRASi) are currently limited to specifically targeting G12C. While experimental non-G12C inhibitors are being developed, resistance mechanisms to non-G12C mutations—including G12D/R/S/V—remain relatively understudied. We set out to characterize the binding efficiency of KRAS to RAF1 and the PI3K subunit p110α, and to understand how isoforms differ in inhibitor resistance strategies. Our findings suggest that significant variances in KRAS mutation-specific effector binding preference exist and are cell line dependent. We performed proximity ligation based immunofluorescence assays (PLA) on an isogenic panel of human colorectal SW48 KRAS cells with G12C/D/R/S/V or wildtype. SW48 cells with G12S significantly prefer the KRAS-RAF1 mode of binding over otherwise isogenic WT cells, and G12V homologs prefer PI3K. Our findings suggest that in this model, G12R cells have no specific preference of one binding mode over the other. We hypothesize that G12 chemistry drives effector binding preference and that G12X inhibitor resistant cell cultures will demonstrate variant mechanisms of resistance in line with their preferred binding partner. Ongoing studies will further characterize understudied RAS isoform biology and evaluate the links between isoform chemistry and mechanisms of inhibitor resistance. These studies will expand our mechanistic knowledge of the interplay between G12X chemistry and adaptive resistance in human cancer. Citation Format: Leonard J. Ash, Ottavia Bourdain, Dennis Lam, Shlomo S. Pallas, Andrew L. Wolfe. KRAS G12X mutants display differential preferences in downstream effector binding [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1669.