HBV-specific CD8 T cells present higher TNF-α expression but lower cytotoxicity in hepatocellular carcinoma

Tumor necrosis factor (TNF)-α is largely regarded as a proinflammatory cytokine, but several recent researches have demonstrated that TNF-α could possess immunoregulatory roles with potential to suppress anti-tumor immunity. Chronic hepatitis B virus (HBV) infection is a major risk factor of hepatocellular carcinoma (HCC), and HBV-specific CD8 T cells could exert anti-tumor roles in HCC patients. Here, we found that HBV-specific CD8 T cells, both in the peripheral blood and in the tumor microenvironment, were more enriched with TNF-α-expressing cells than interferon (IFN)-γ-expressing cells. Compared to IFN-γ-expressing HBV-specific CD8 T cells, TNF-α-expressing HBV-specific CD8 T cells presented lower expression of inhibitory checkpoint molecules, including programmed cell death (PD)-1, T cell immunoglobulin mucin-3 (TIM-3) and cytotoxic T lymphocyte antigen (CTLA)-4. HBV-specific CD8 T cells could mediate the lysis of autologous primary tumor cells, and the inhibition of TNF-α could further elevate their cytotoxic capacity. Subsequently, we demonstrated that TNF-α inhibition in HBV-specific CD8 T cells could significantly increase granzyme B (GZMB) and perforin 1 (PRF1) expression while having no effect towards granzyme A (GZMA) expression. The addition of exogenous TNF-α at low levels had no consistent effect on the expression of GZMA, GZMB and PRF1, but at higher levels, exogenous TNF-α significantly reduced GZMA, GZMB and PRF1 expression. Overall, these results suggested that TNF-α-expressing cells probably presented a deleterious role in HCC but were enriched in HBV-specific CD8 T cells.