Unmodified γδ T cells exhibit potent antitumor activity in hepatocellular carcinoma and are enhanced by PD-L1 blockade

OBJECTIVE: Hepatocellular carcinoma (HCC) exhibits a profoundly immunosuppressive microenvironment that limits the efficacy of current immunotherapies. This study evaluated the antitumor activity of unmodified γδ T cells in HCC and defined immune checkpoint-mediated mechanisms that restrict their therapeutic durability. METHODS: Bioinformatic analyses of LIHC datasets were performed to identify candidate prognostic T-cell receptor γ variable (TRGV) genes. Ex vivo-expanded γδ T cells were evaluated using in vitro co-culture assays with PD-L1-low (Huh7) and PD-L1-high (HCC-LM3) HCC cell lines, real-time cytotoxicity analyses, and cytokine profiling. Therapeutic efficacy, immune checkpoint regulation, and systemic safety were further assessed in subcutaneous xenograft mouse models using co-implantation and intravenous administration strategies. RESULTS: TRGV3 expression correlated with improved overall survival and reflected γδ T-cell presence within the tumor microenvironment. Unmodified γδ T cells exerted potent, dose-dependent cytotoxicity against HCC cells and suppressed tumor growth in vivo, particularly in PD-L1-negative models. In PD-L1-positive HCC-LM3 tumors, γδ T cell efficacy was reduced following systemic administration and was associated with tumor-induced PD-L1 upregulation, delayed cytotoxicity, and tumor recurrence. Blockade of the PD-L1/PD-1 axis restored durable γδ T cell-mediated tumor control. Importantly, γδ T-cell treatment was well tolerated, with no overt systemic toxicity observed. CONCLUSION: Unmodified γδ T cells demonstrate strong antitumor activity and a favorable safety profile in HCC but are limited by adaptive PD-L1-mediated immune resistance in PD-L1-positive tumors. These findings provide a mechanistic rationale for combining γδ T cell-based therapies with immune checkpoint inhibition to enhance therapeutic efficacy in advanced HCC.