Here, NK cytotoxicity against HCC cells was attenuated under hypoxia compared to normoxia (Figure 5A; 20% O2, 22.14%; 5% O2, 10.57%; *** p < 0.0001), and the expression of the activating receptors NKG2D and NKp44 on the surface of NK-92 cells was also significantly reduced (Figure 5E; NKG2D+: 20% O2, 82.5%; 5% O2, 76.01%; NKp44+: 20% O2, 36.71%; 5% O2, 32.34%; * p < 0.05; *** p < 0.0001). The gene discussed is KLRK1; the disease is hepatocellular carcinoma.