KLRK1 and hepatocellular carcinoma: The cytotoxic effect of NK-92 cells on HIF-1α-expressed HCC SK-Hep1 cells was improved by blocking sIL-6 in their supernatants by IL-6 antibody (Fig. 2A), and the activating receptor NKG2D and NKG2C were highly upregulated (Fig. 3).