PDCD1 and hepatocellular carcinoma: In the current study, patients in the high-risk group had significantly higher expression of PD-1, TIGIT, CTLA4, and TIM-3 compared to patients in the low-risk group, implying that the high-risk group in the prognostic signature may represent the immunogenic microenvironment, and thus, we inferred that HCC patients with high-risk scores might respond better to PD-1, TIGIT, CTLA4, and TIM-3 antibodies.