TIGIT and hepatocellular carcinoma: We found a close correlation between risk score of HCC patients and the expression of key immune checkpoints composed of cytotoxic T lymphocyte-associated protein 4 (CTLA4), programed death-1 (PD1), T cell immunoglobulin mucin 3 (TIM3), lymphocyte activation gene 3 (LAG3) and T cell immunoreceptor with Ig, and ITIM domains (TIGIT) (Fig. 4d).