Abstract

Background Hepatocellular carcinoma (HCC) remains a leading cause of cancer mortality worldwide. While regulatory T (Treg) cells are known to contribute to HCC progression, the molecular mechanisms regulating their activation, particularly those involving post-translational modifications, remain poorly understood. Methods This study employed a comprehensive approach combining clinical sample analysis, in vitro cell models (HepG2, Hep3B, HCC-LM3) and in vivo xenograft experiments. Genetic manipulation involved lentiviral-mediated knockdown or overexpression of FCN3 and STT3A. Techniques included immunofluorescence, co-immunoprecipitation, glycosylation validation, CCK-8, wound healing, Transwell and flow cytometry. Results Clinical data revealed significant downregulation of FCN3 in HCC tissues, correlating with poor patient survival. Mechanistically, FCN3 suppressed Treg activation and HCC progression by inhibiting Wnt/β-catenin signaling through APC upregulation. However, the glycosyltransferase STT3A mediated N-glycosylation of FCN3 at Asn189, thereby disrupting the tumor-suppressive function of FCN3 in HCC. In mouse models, STT3A knockdown reduced tumor growth and decreased Treg infiltration. Additionally, the Treg cell-depleting agent diphtheria toxin could reverse the promoting effect of STT3A overexpression on HCC tumor growth. Conclusion This research unveiled a novel STT3A-FCN3-β-catenin axis that drove HCC progression through glycosylation-dependent Treg activation. These findings provided new insights into immune evasion mechanisms and highlighted potential therapeutic opportunities for HCC.