In addition, the expression of gene encoding for immune checkpoint proteins, such as KLRD1/HLA-E, PD-L1/CD274/PD-CD1 and CTLA4/CD86, may in turn influence NK cell activation such as cytolysis, antibody-dependent cellular cytotoxicity (ADCC) and cytokine release, their survival, and the abundance and inhibition of NK cells in patients with HCC. Here, PDCD1 is linked to hepatocellular carcinoma.