Tetrahydromagnolol induces autophagic cell death by targeting the m6A reader protein YTHDF2 and enhances the efficacy of anti-PD-1 immunotherapy in pancreatic cancer cells.

Rationale: Tetrahydromagnolol (THM) is a bioactive compound derived from Magnolia officinalis. Although other compounds from this plant, such as magnolol and honokiol, have shown significant anticancer potential, the anticancer activities of THM remain unreported. This study aims to investigate the anticancer effects and underlying molecular mechanisms of THM in pancreatic cancer cells. Methods: In this study, the effects of THM on pancreatic cancer cells were investigated by various experiments both in vitro and in vivo. The molecular target of THM in pancreatic cancer cells was determined by transcriptomics, ligand coupled epoxy-activated magnetic beads, CETSA, SPR analysis, ITC analysis, LC-MS/MS analysis, and MD simulations. Results: Our findings reveal that THM significantly suppresses pancreatic cancer cell proliferation and induces cell death. Autophagic cell death is demonstrated to predominantly contribute to THM-triggered cell death. Importantly, YTHDF2, the m6A reader protein, is identified as a direct anticancer target of THM. Further investigations have shown that THM binds to YTHDF2, blocking its ability to recognize m6A modifications on the autophagy-related gene mRNAs ATG5 and ATG7. Notably, a medium dose of THM exhibits anticancer efficacy comparable to gemcitabine (GEM), the first-line treatment for pancreatic cancer, and the high dose of THM showing superior anticancer effects than GEM treatment. Moreover, THM enhances the efficacy of anti-PD-1 immunotherapy in pancreatic cancer models. Conclusions: This study presents the first evidence that THM promotes cell death in pancreatic cancer cells by inducing autophagy and YTHDF2 is identified as a direct binding target of THM. Targeting YTHDF2 is a critical determiner for THM-induced autophagic cell death and the immunosensitizing effect of THM with anti-PD-1 inhibitor in pancreatic cancer. Therefore, THM may function as a candidate anticancer drug for pancreatic cancer treatment, either alone or in combination with anti-PD-1 immunotherapy.