MGST1 facilitates novel KRASG12D inhibitor resistance in KRASG12D-mutated pancreatic ductal adenocarcinoma by inhibiting ferroptosis.

Background: Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal cancer with a low 5-year survival rate. Treatment options for PDAC patients are limited. Recent studies have shown promising results with MRTX1133, a KRAS^G12D inhibitor that demonstrated potent antitumor activity in various types of tumors with KRAS^G12D mutation. Resistance to KRAS inhibitors is frequently occurred and one of the main reasons for treatment failure. Understanding resistance mechanisms to novel KRAS inhibitors is crucial to ensure sustained and durable remissions.

Methods: Two KRAS^G12D inhibitor MRTX1133-resistant PDAC cell lines were established in vitro. The resistance mechanisms to KRAS^G12D inhibitor MRTX1133 against PDAC in vitro and in vivo were characterized by RNA sequencing, reverse transcript polymerase chain reaction, cytotoxicity test, plasmid transfection, lentivirus transfection, lipid peroxidation detection, malondialdehyde levels detection, glutathione levels detection, western blot, immunofluorescence, nude mice tumorigenesis experiment and immunohistochemistry.

Results: The bioinformatics analysis and transcriptome sequencing showed that ferroptosis was involved in the resistant effect of the KRAS^G12D inhibitor treatment, and MGST1 was the key molecule against MRTX1133-induced ferroptosis. Increased expression of MGST1 weakened the cytotoxicity of MRTX1133 by inhibiting lipid peroxidation-induced ferroptosis in KRAS^G12D inhibitor-resistant PDAC cells. Knockdown or overexpression of MGST1 conferred sensitivity or resistance to KRAS^G12D inhibitor MRTX1133, respectively. Mechanismly, increased nuclear localization and higher levels of active β-catenin were observed in MRTX1133-resistant PDAC cells, which contributed to higher MGST1 expression. Knockdown of CTNNB1 or TCF4 can decreased MGST1 expression. Additionally, we found that PKF-118-310, an antagonist of β-catenin/Tcf4 complex, repressed MGST1 expression. In both in vitro and in vivo models, a synergistic effect was observed when combining MRTX1133 and PKF-118-310 in KRAS^G12D inhibitor MRTX1133-resistant PDAC cells and tumors.

Conclusion: Our data showed that KRAS^G12D inhibitor MRTX1133 combined with PKF-118-310 could enhance the effectiveness of MRTX1133 treatment response through induction of ferroptosis via inhibiting MGST1 expression in MRTX1133-resistant PDAC cells and tumors. This evidence may provide a promising strategy to overcome KRAS^G12D inhibitor MRTX1133 resistance in PDAC patients with KRAS^G12D mutations.