Current anti-cancer chemotherapy regimens may also cause the upregulation of NKG2D ligands (87, 88), and while this may transiently upregulate NK cytotoxicity, a sustained and prolonged period of high ligand expression for cancer immunotherapy could exhaust NK cytotoxicity and pose an area of concern for long-term efficacy of NK cell function. The gene discussed is KLRK1; the disease is cancer.