PVR and hepatocellular carcinoma: Hepatocarcinoma cells express ligands of several activating NK receptors (NKR), including NKp30, natural killer receptor group 2, member D (NKG2D), and DNAM-1, such as the B7 protein homolog 6, the major histocompatibility complex class I chain-related protein A and B (MICA/B), and CD155, respectively, whose expression can correlate with HCC outcome [73,74].