Abstract 1107: Notch activation drives resistance to Kras(G12C) inhibition in lung adenocarcinoma

Abstract

Abstract Approximately one-third of lung adenocarcinoma (LUAD) tumors contain driver mutations in the Kras GTPase, most commonly occurring as Kras(G12C) activating mutations. Despite the promising development of covalent G12C small molecule inhibitors, early-phase clinical trial data indicate most patients will likely demonstrate disease progression through either intrinsic or acquired resistance. Thus, there is an urgent need to identify such resistance mechanisms to targeting Kras. Our lab previously discovered a unique requirement for Notch3 in tumor-propagating cells from the KrasLSL-G12D p53fl/fl LUAD mouse model as well as in patient-derived xenografts. Here we report activated Notch3 as a novel driver of resistance to Kras(G12C) inhibition in LUAD cell lines. Aiming to study the Notch3 transcriptional signature in LUAD, we developed an inducible model of Notch3 intracellular domain (NICD) expression in Kras-mutant LUAD cell lines. Our data demonstrate that activated NICD modulates downstream RTK signaling pathways to suppress both cell cycle arrest and apoptosis in response to G12C inhibitor treatment. We subsequently performed RNA-sequencing to identify Notch-dependent genes driving resistance and in parallel, used Cut&Run technology to interrogate the global chromatin binding profiles of Notch3 and associated histone marks in NICD-expressing cell lines. We integrate our transcriptomic and epigenomic data to reveal that NICD acts as a key regulator of Rho family genes, which in turn support cell survival upon Kras inhibition. We additionally find enrichment of cell division and morphological signatures in inhibitor treated NICD cell lines and we elucidate the mechanism of direct Notch target genes in mediating the apoptotic response. Finally, we conduct a focused in vitro CRISPRi screen in the H358 LUAD cell line to identify the subset of Notch target genes required for NICD-induced resistance. Our results define a Notch3 transcriptional landscape in LUAD and demonstrate a role for Notch signaling in promoting resistance to small molecule Kras inhibitors. Citation Format: Elizabeth E. Hwang, Alex Lee, Stanley Leung, Marcus Breese, Alejandro Sweet-Cordero. Notch activation drives resistance to Kras(G12C) inhibition in lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1107.