PDCD1 and hepatocellular carcinoma: Moreover, TOX knockdown in a mouse hepatocellular carcinoma (HCC) model or in tumor-infiltrating CD8+ T cells resulted in significant reduction in immune checkpoint proteins, including PD-1, CTLA-4, TIM-3, and TIGIT, ameliorating T cell exhaustion and promoting the antitumor effects of antigen-specific CD8+ T cells [32–34].