When the GEP monoclonal antibody A23 was co-cultured with hepatocellular carcinoma cells in vitro, NK cells could be reactivated, the production of GEP and soluble ligand sMICA production were all reduced, so that the expression NKG2D was up-regulated, IFN-gamma and perforin production were significantly increased, and the cytotoxic effect was ultimately increased. The gene discussed is KLRK1; the disease is hepatocellular carcinoma.