Abstract 518: Repurposing of pralatrexate in gastric cancer: Inducing cell death via SMO inhibition and GLI1 suppression

Gastric cancer (GC) is the fifth most common cancer and the fourth leading cause of cancer-related deaths worldwide. Currently, GC has serious drug resistance and side effects to existing treatments, and the development of new treatments is urgently needed. Abnormal activation of Hedgehog (Hh) signaling can promote the proliferation, metastasis, and drug resistance of GC cells and inhibit apoptosis. In gastrointestinal cancer, the expression of components of the Hh signaling pathway and their target genes are upregulated. Through TCGA analysis, we found that among the five types of digestive cancers: cholangial, colorectal, gastric, hepatocellular, and pancreatic, GC is most affected by Hh signaling. Pralatrexate is an FDA-approved drug originally used to treat relapsed or refractory peripheral T-cell lymphoma (PTCL). Research has been conducted on its anticancer efficacy in solid carcinomas such as Non-small cell lung cancer (NSCLC), but its efficacy in GC remains unexplored. In a previous study, screening results using an FDA-approved drug library showed that Pralatrexate inhibits GLI-dependent luciferase activity. In this study, we demonstrated that Pralatrexate canonically regulates Hh signaling by downregulating SMO. Structural predictions using AI modeling indicated that Pralatrexate binds to a site similar to the SMO antagonist ANTA-XV, distinct from Cyclopamine's binding pocket. It was confirmed that Pralatrexate causes degradation of SMO, and GLI1 was subsequently degraded by lysosome. This suppression of Hedgehog (Hh) signaling results in reduced cell proliferation and the induction of apoptosis. In summary, Pralatrexate canonically regulates Hh signaling by inhibiting SMO and suppressing GLI1, ultimately reducing cell proliferation and causing apoptosis in GC. Our findings uncover a novel anticancer mechanism of Pralatrexate in GC, providing a potential basis for its clinical application in GC therapy. Citation Format: Hyemi Yun, Bo Ram Kim, Bu Gyeom Kim, Dae Yeong Kim, Okhyeon Kim, Yoon Namgung, Jun Woo Bong, Sanghee Kang, Sun Il Lee, Sang Cheul Oh. Repurposing of pralatrexate in gastric cancer: Inducing cell death via SMO inhibition and GLI1 suppression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 518.