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PI3K Regulates Wild-type RAS Signaling to Confer Resistance to KRAS Inhibition

ABSTRACT: Despite the availability of RAS inhibitors and the dependence of >90% of pancreatic ductal adenocarcinomas (PDAC) on oncogenic KRAS mutations, resistance to KRAS inhibition remains a serious obstacle. We showed here that PI3K plays a major role in this resistance through upstream activation of wild-type RAS signaling – beyond its known KRAS effector function. The combination of proximity labeling, CRISPR screening, live-cell imaging, and functional assays revealed that PI3K orchestrates phosphoinositide-mediated GAB1 recruitment to the plasma membrane, nucleating assembly of RAS signaling complexes that activate MAPK in an EGFR/SHP2/SOS1-dependent manner. Inhibiting PI3K enhanced sensitivity to mutant-specific KRAS inhibitors in PDAC cells, including in cells with clinically identified PIK3CA mutations. These findings refine RAS-PI3K signaling paradigms, reveal that PI3K-driven wild-type RAS activation drives resistance to KRAS inhibition, and illuminate avenues for augmenting KRAS-targeted therapies in PDAC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE328107 | GEO | 2026/04/28

REPOSITORIES: GEO

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Project description:Small molecule KRASG12C(OFF) inhibitors that bind to the inactive GDP-bound state of KRAS have demonstrated efficacy in patients with KRASG12C mutant tumors, yet responses tend to be transient due to on-treatment resistance. Recently, a RAS(ON) G12C-selective inhibitor, which binds to the active GTP-bound state of KRAS, was introduced into the clinical settings. We generated cell line and PDX resistant models to KRAS G12C(OFF) and RAS(ON) G12C-selective inhibitors that displayed a variety of resistance mechanisms similar to the ones observed in human studies. Here we interrogated resistance mechanisms using a multi-omics strategy consisting of phosphoproteomics, exome sequencing, and RNA-sequencing then coupled these analyses to functional testing using small molecule screens, CRISPR screens and combination with RAS(ON) inhibitors that have entered clinical trials. We found two models that reactivate RAS signaling, either via KRASG12C gene amplification or NRASG13R mutation, and showed that tumors driven by these resistance mechanisms are vulnerable to dual inhibition by either RAS(ON) G12C-selective combined with RAS(ON) multi-selective inhibitor. Two models, which lack any discernable genomic alteration, acquired resistance associated with increased receptor tyrosine kinase activity and downstream persistent RAS activity, were sensitive to RAS-GTP inhibition by RAS(ON) multi-selective inhibitor. Finally, one model displayed epithelial-mesenchymal transition, loss of RAS activity and acquired dependence on cell cycle kinases and proteins associated with DNA damage response. Our work highlights KRASi-resistant states that could potentially be overcome with a RAS(ON) multi-selective inhibitor as a standalone agent or in carefully tailored combinations. It also identifies resistant tumors that have reduced RAS dependance, thereby necessitating alternative therapeutic strategies. These datasets compare parental LUN156 patient-derived xenograft tumors to those with acquired resistance to the KRAS G12C inhibitors, Adagrasib (AR) and RM-4998 (RR). Data are provided for protein expression (ID), global phosphorylation (IMAC), and tyrosine phosphorylation (pY) as indicated in the filenames.

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PI3K Regulates Wild-type RAS Signaling to Confer Resistance to KRAS Inhibition

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