HCC usually occurs in the context of liver inflammation, in which PD-1 is highly expressed in intrahepatic lymphocytes, while its ligands, PD-L1 and PD-L2, are highly expressed in Kupffer cells, sinusoidal endothelial cells, and leukocytes once cells are exposed to pro-inflammatory cytokines [32]. The gene discussed is PDCD1; the disease is hepatocellular carcinoma.