PDCD1 and hepatocellular carcinoma: ICBs targeting programmed cell death protein 1 (PD-1), programmed cell death ligand 1 (PD-L1) or cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) have recently undergone several clinical trials and are paving the way for the evolution of novel treatment strategies of advanced HCC [23].