The cytotoxic effect of NK-92 on HCC significantly decreased by the blocking of IL-6 (Fig. 2A, Non-treated 30.97%, Anti-IL-6 28.91%, *p < 0.05) however, to HIF-1α-expressed HCC cells, it remarkably enhanced compared as the non-blocking of IL-6 (Fig. 2A, Anti-IL-6 5.15%, CoCl2 + Anti-IL-6 13.66%, **p < 0.05). The gene discussed is HIF1A; the disease is hepatocellular carcinoma.