Mechanisms of resistance to oncogenic KRAS inhibition in pancreatic cancer

KRAS inhibitors demonstrate clinical efficacy in pancreatic ductal adenocarcinoma (PDAC); however, resistance is common. Among patients with KRASG12C-mutant PDAC treated with adagrasib or sotorasib, mutations in PIK3CA and KRAS, and amplifications of KRASG12C, MYC, MET, EGFR, and CDK6 emerged at acquired resistance. In PDAC cell lines and organoid models treated with the KRASG12D inhibitor MRTX1133, epithelial-to-mesenchymal transition and PI3K-AKT-mTOR signaling associate with resistance to therapy. MRTX1133 treatment of the KrasLSL-G12D/+;Trp53LSL-R172H/+;p48-Cre (KPC) mouse model yielded deep tumor regressions, but drug resistance ultimately emerged, accompanied by amplifications of Kras, Yap1, Myc, and Cdk6/Abcb1a/b, and co-evolution of drug-resistant transcriptional programs. Moreover, in KPC and PDX models, mesenchymal and basal-like cell states displayed increased response to KRAS inhibition compared to the classical state. Combination treatment with KRASG12D inhibition and chemotherapy significantly improved tumor control in PDAC mouse models. Collectively, these data elucidate co-evolving resistance mechanisms to KRAS inhibition and support multiple combination therapy strategies. Autochthonous KPC (KrasLSL-G12D/+;Trp53LSL-R172H/+;p48-Cre) genetically engineered mouse model (GEMM) of PDAC were treated with MRTX1133 (KRAS p.G12D inhibitor) or vehicle. Tumors were harvested after 3 days of continuous treatement ("Early vehicle" and “Early MRTX1133”) or after mice reached a humane endpoint ("Endpoint vehicle" or “MRTX1133 resistant”) based on criteria from the Institutional Animal Care & Use Committee (IACUC) at Dana-Farber Cancer Institute (DFCI).

KRAS抑制剂在胰腺导管腺癌（pancreatic ductal adenocarcinoma, PDAC）中展现出明确的临床疗效，但耐药现象极为常见。在接受阿达格拉西布（adagrasib）或索托拉西布（sotorasib）治疗的KRASG12C突变型PDAC患者中，PIK3CA与KRAS突变，以及KRASG12C、MYC、MET、EGFR和CDK6的扩增，会在获得性耐药阶段被检测到。在经KRASG12D抑制剂MRTX1133处理的PDAC细胞系及类器官模型中，上皮间质转化（epithelial-to-mesenchymal transition）与PI3K-AKT-mTOR信号通路与治疗耐药密切相关。对KrasLSL-G12D/+;Trp53LSL-R172H/+;p48-Cre（以下简称KPC）小鼠模型施以MRTX1133治疗，可实现肿瘤的深幅退缩，但最终仍会产生耐药性，伴随Kras、Yap1、Myc及Cdk6/Abcb1a/b的扩增，以及耐药相关转录程序的共同演化。此外，在KPC模型与患者来源异种移植（patient-derived xenograft, PDX）模型中，间质样与基底样细胞状态相较于经典型细胞状态，对KRAS抑制治疗的响应更为显著。联合使用KRASG12D抑制治疗与化疗，可显著改善PDAC小鼠模型的肿瘤控制效果。综上，本研究数据阐明了KRAS抑制治疗中共同演化的耐药机制，并为多种联合治疗策略提供了理论支持。
本研究将自发形成PDAC的KrasLSL-G12D/+;Trp53LSL-R172H/+;p48-Cre（KPC）基因工程小鼠模型（genetically engineered mouse model, GEMM）分别施以MRTX1133（KRAS p.G12D抑制剂）或赋形剂处理。按照丹娜法伯癌症研究院（Dana-Farber Cancer Institute, DFCI）下属实验动物护理与使用委员会（Institutional Animal Care & Use Committee, IACUC）制定的标准，在连续给药3天后收获肿瘤（分为"早期赋形剂组"与"早期MRTX1133组"），或在小鼠达到人道终点时收获肿瘤（分为"终点赋形剂组"与"MRTX1133耐药组"）。