STT3A-mediated FCN3 N-glycosylation promotes Treg cell activation to drive hepatocellular carcinoma progression via Wnt/β-catenin.

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. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13402-025-01159-1.