Abstract KRAS G12D mutation is a prevalent oncogenic driver in gastrointestinal (GI) cancer. Recently, novel KRAS inhibitors have shown promise in KRAS-mutant cancers. However, acquired resistance inevitably emerges, limiting clinical efficacy. Nevertheless, their resistance mechanisms and overcoming strategies remain largely undefined. We established nine human GI cancer models of acquired resistance to MRTX1133, a KRAS G12D selective inhibitor: two gastric (AGS and SNU-601), two pancreatic (AsPC-1 and PANC-1), and two colorectal cancer cell lines (SNU-C2A and SNU-C2B), and three colorectal cancer patient-derived organoids (SNU-4646S1-TO, SNU-6325-TO, and SNU-6330-TO). Single-cell RNA sequencing analysis of resistant and parental SNU-4646S1-TO (GSE290526) revealed enrichment of angiogenesis, hypoxia, and epithelial-mesenchymal transition (EMT) signatures in resistant models compared to parental cells. In line with this, all nine resistant models showed markedly elevated VEGFA expression and VEGFR2 activation, which we traced to AKT-mediated nuclear translocation of the transcription factor SP1. Mechanistic investigation revealed that oncogenic KRAS in the resistant state formed a complex with p110γ and p101, subunits of PI3Kγ, leading to hyperactivation of PI3Kγ. This, in turn, established the autocrine VEGFA-VEGFR2 signaling loop via AKT and SP1 activation that reinforced EMT and sustained the resistant phenotype. In the resistant models, disrupting VEGFA-VEGFR2 signaling using KDR knock-out and ramucirumab treatment restored MRTX1133 sensitivity and reversed EMT in resistant cells. Inhibition of hyperactivated PI3Kγ using eganelisib, a selective p110γ inhibitor, also replicated the same results. Indirect co-culture experiments of cancer cells and human large vessel endothelial cells (HUVECs) identified that cancer-endothelial paracrine crosstalk in resistant models further amplified angiogenesis, hypoxia, and EMT signatures (GSE290487) in cancer cells and concurrently promoted endothelial cell proliferation, suggesting a microenvironment-mediated feedback loop. In a mouse xenograft model of MRTX1133-resistant PANC-1 cells, anti-VEGFR2 antibody (DC101) treatment combined with MRTX1133 rechallenge more effectively reduced tumor growth and angiogenesis than either agent alone, without significant changes in body weight. Our study revealed a novel mechanism of acquired resistance to KRAS G12D inhibition in GI cancers: a KRAS-PI3Kγ interaction-driven autocrine and paracrine VEGFA-VEGFR2 signaling axis that fosters EMT and therapeutic escape. Importantly, co-targeting this axis with VEGFR2 or PI3Kγ inhibitor restored sensitivity to KRAS inhibition. These findings provide a rationale for further biomarker-guided clinical trials of combined VEGFA-VEGFR2 and KRAS inhibition in patients experiencing acquired resistance after KRAS inhibitor treatment. Citation Format: Sung-Hyun Hwang, Mingyun Bae, Ji-Won Kim, Seung Yoon Hyun, Kui-Jin Kim, Joshua Choe, Min Jun Kim, Ji Won Park, Seung Yong Jeong, Songji Choi, Woochan Park, Jeongmin Seo, Heejung Chae, Minsu Kang, Eun Hee Jung, Koung Jin Suh, Se Hyun Kim, Jin Won Kim, Yu Jung Kim, Jee Hyun Kim, Haeseong Park, Andrew J. Aguirre, Eunjung Lee, Ja-Lok Ku, Keun-Wook Lee. VEGFR2 blockade overcomes acquired KRAS G12D inhibitor resistance driven by PI3Kγ activation abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 6772.
Hwang et al. (Fri,) studied this question.