PDCD1 and hepatocellular carcinoma: In HCC tumor-bearing mice treated with anti-PD-1, concurrent anti-TIGIT treatment resulted in a combined blockade effect that expanded the effector memory CD8 + T cell population and increased the cytotoxic T cell to Treg ratio in the tumor, thereby suppressing tumor growth and prolonging survival (Li et al., 2018; Chiu et al., 2020; Lepletier et al., 2020), indicating that TIGIT can be used as a rational target to further improve the efficacy of anti-PD-1 therapy in HCC.