Abstract 3867: Chromatin modification driving sub-clonal resistance to KRAS G12C combination therapies in KRAS mutant non-small cell lung cancer

Abstract The FDA approval of the KRAS G12C inhibitor (G12Ci) sotorasib and the advancement of similar drugs into clinical trials marks a major milestone in treating KRAS G12C non-small cell lung cancer (NSCLC). However, not all patients respond (sotorasib - ORR = 37.1%, adagrasib - 43%, JDQ443 - 35%), motivating preclinical and clinical investigation into mechanisms of intrinsic and acquired resistance. For instance, clinical studies have reported on-target KRAS mutations and preclinical studies have demonstrated mitogen-activated protein kinase (MAPK) feedback reactivation including EGFP, SHP2, and WT RAS signaling. In response to targeted therapies, sub-populations of cells can enter quiescence or specific epigenetic-driven states that confer drug tolerance. However, epigenetic states defining drug-tolerant persister populations and contributing to adaptive resistance to KRAS G12Ci have not been reported. Using a lineage tracing barcoded system, we identify distinct and reversible subpopulations defined by specific chromatin and transcriptional states in KRAS NSCLC cell lines that contribute to KRAS G12Ci resistance in vitro, even prior to drug treatment. We observed that specific states, including activation of histone demethylation and SWI/SNF complex, may contribute to MAPK reactivation-driven resistance. These results suggest potential epigenetic vulnerabilities that can be exploited to improve the response to KRAS G12Ci. Moreover, we observed distinct persister subpopulations with resistance to KRAS G12Ci combination co-targeting orthogonal pathways (SHP2, CDK4/6, PI3K, and MCL-1), raising the possibility that distinct epigenetic-transcriptional states contribute to differential drug response and clonal evolution of persisters. Collectively, these results suggest that more complete tumor regression may be achieved by orthogonal strategies that target different resistant populations within the same tumor. Citation Format: Chendi Li, Qian Qin, Mohammed Usman Syed, Anahita Nimbalkar, Barbara Karakyriakou, Sarah E. Clark, Anne Y. Saiki, Paul E. Hughes, Chris Ott, Luca Pinello, Aaron N. Hata. Chromatin modification driving sub-clonal resistance to KRAS G12C combination therapies in KRAS mutant non-small cell lung cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3867.