Abstract PR015: Silent KRAS mutations confer altered sensitivity to targeted KRAS inhibition

Abstract Silent, or synonymous mutations, are typically overlooked, ignored, and not reported because the mutational change does not change the encoded amino acid. For example, the FDA-approved cobas® KRAS Mutation Test is specifically designed to ignore KRAS G12G and G13G silent mutations, to prevent them from inadvertently being reported. Despite this, silent mutations cluster in KRAS with low frequency at G12, G13, and G60, at or adjacent to the hotspot activating mutation positions. KRAS is evolutionarily constrained to contain rare codons or codon pairs at these positions, and we have previously shown that any silent mutation at these positions increases KRAS protein expression in accordance with glycine codon usage frequency. Further, we determined and these KRAS silent mutations can drive tumorigenic phenotypes in NIH3T3 cells. We now show that among cancer patients with wild-type (WT) KRAS tumors, high expression of KRAS is associated with a poor prognosis in a pan-cancer cohort. Furthermore, we determined that when performing proliferation assays in NIH3T3 cells overexpressing KRAS silent G12G, G13G, and G60G mutations treated with AMG410, BI-2865, or RMC-7977, the cells exhibit a growth defect similar to KRAS G12V-overexpressing cells, despite their WT amino acid sequence. Finally, silent mutation-containing NIH3T3 cells also exhibit altered responses to KRAS inhibition as measured by ERK MAPK signaling. Future studies will involve evaluating silent KRAS mutations by introducing silent KRAS mutations at the endogenous locus in non-transformed human cells. Citation Format: Megan A. Satyadi, Rachel Bridgens, Haley Todd, Grace Goodhart, Syed A. Ahmad, Andrew M. Waters. Silent KRAS mutations confer altered sensitivity to targeted KRAS inhibition [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: RAS Oncogenesis and Therapeutics; 2026 Mar 5-8; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(5_Suppl_1):Abstract nr PR015.