A Marine‐Derived Small Molecule Inhibits Prostate Cancer Growth by Promoting Endoplasmic Reticulum Stress Induced Apoptosis and Autophagy

ABSTRACT MHO7 (6‐epi‐ophiobolin G), a novel component extracted from a mangrove fungus, exhibits significant anticancer effects against breast cancer. However, the precise mechanism underlying the anticancer effects of MHO7 in prostate cancer (PCa) is yet to be fully elucidated. Therefore, this study was undertaken to assess the effect of MHO7 on PCa cells and elucidate its underlying mechanism. A series of in vitro experiments were conducted, including Cell Counting Kit‐8, and plate clone formation assays, flow cytometry analysis, electron microscopy, immunofluorescence staining, western blotting, and molecular dynamics simulation. Additionally, in vivo tumor xenograft models were employed. Our findings revealed that MHO7 could induce cellular autophagy at low concentration (2 μM) and apoptosis at relatively high concentration (4 and 8 μM), leading to significant PCa cell growth inhibition. Furthermore, MHO7 triggered endoplasmic reticulum (ER) stress, which subsequently stimulated autophagy and apoptosis via IRE1α/XBP‐1s signaling pathway activation. Notably, IRE1α knockdown markedly reduced MHO7‐induced autophagy and apoptosis. Moreover, MHO7 targeted the IRE1α protein, thereby enhancing its stability. MHO7 also exhibited substantial anticancer activity in tumor xenograft models. Our study revealed that MHO7 holds considerable potential as an anticancer agent against PCa, attributable to its activation of ER stress‐induced autophagy and apoptosis at different concentrations, facilitated by the upregulation of IRE1α expression.