SENP3-mediated deSUMOylation stabilizes programmed death-ligand 1 to promote immune evasion in hepatocellular carcinoma.

Despite the clinical benefits of immune checkpoint blockade in hepatocellular carcinoma (HCC), therapeutic efficacy remains limited due to persistent immune evasion. SENP3, a SUMO2/3-specific protease sensitive to redox regulation, has emerged as a critical regulator of protein homeostasis and immune modulation. This study investigates how SENP3 regulates programmed death-ligand 1 (PD-L1) stability through SUMOylation to facilitate immune escape in HCC. We performed comprehensive molecular and functional analyses in HCC cell lines using SENP3 manipulation strategies. PD-L1 expression and SUMOylation status were evaluated by Western blotting and Ni-NTA pulldown assays. Protein interactions were examined through coimmunoprecipitation. Functional immune assays included T cell cytotoxicity measurements using coculture systems, colony formation assays to quantify tumor cell survival, cytokine profiling by ELISA, and granzyme B (GzmB) expression analysis in CD8⁺ T cells via flow cytometry. Clinical samples and experimental models demonstrated significant SENP3 overexpression in HCC. SENP3 knockdown reduced PD-L1 abundance while enhancing T cell-mediated tumor killing, pro-inflammatory cytokine secretion, and cytotoxic GzmB expression in CD8⁺ T cells. Mechanistic studies revealed that SENP3 directly interacts with PD-L1 and catalyzes its deSUMOylation, thereby extending PD-L1 protein half-life. Importantly, SENP3 overexpression rescued the immunostimulatory effects of PD-L1 knockdown, confirming the specificity of this regulatory pathway. Our findings establish SENP3 as a novel posttranslational regulator of PD-L1 that promotes immune evasion in HCC through direct deSUMOylation and stabilization of PD-L1 protein. Therapeutic targeting of SENP3 may overcome resistance to immune checkpoint inhibitors in HCC by restoring antitumor immunity.