Physalin A induces apoptosis through conjugating with Fas-FADD cell death receptor in human oral squamous carcinoma cells and suppresses HSC-3 cell xenograft tumors in NOD/SCID mice

IntroductionOral carcinoma cancer exhibits high global incidence and mortality. Physalin A (PA) was reported to induce programmed cell death in cancer cells. No study has yet investigated the influence of PA in oral squamous cell carcinoma. Herein, this study aims to explore PA-induced anti-cancer effects in human oral carcinoma.MethodsThis study used DNA gel electrophoresis and Annexin V/PI staining to detect DNA fragmentation and cell apoptosis. Western blotting and immunofluorescence analyzed protein expression. Flow cytometry measured Ca²⁺ release and mitochondrial membrane potential (∆Ψm). Moreover, molecular docking models predicted the molecular binding affinity.ResultsDNA gel electrophoresis and annexin V/PI staining confirmed PA-induced DNA fragmentation and apoptosis. Flow cytometry showed PA increased Ca²⁺ release and reduced ∆Ψm levels. PA activated cleaved caspase-3, -8, and -9, upregulated Bax and Bid, and downregulated Bcl-2. PA dose-dependently increased Fas (CD95/APO-1), apoptosis-inducing factor (AIF), and cytochrome c release in western blotting analysis. Confocal microscopy confirmed increased Bax, AIF, cleaved caspase-3, and Fas, with decreased Bcl-2. Molecular docking showed strong PA binding via hydrophobic interactions with the Fas-associated death domain (FADD). Compared with cisplatin, PA inhibited HSC-3 cell xenograft tumor growth in NOD/SCID mice.DiscussionWe reveal that PA binds to the Fas-FADD complex, inducing caspase-8 activation and triggering extrinsic and intrinsic mitochondria-dependent apoptosis in HSC-3 cells. It also suppresses HSC-3 cell xenograft tumors in NOD/SCID mice. These findings suggest PA as a potential anti-oral cancer agent in the future.