ELISA showed that CIK cells produced significant amounts of IFN-γ and IL-6 (Fig. 6E); whereas slight amounts of IL-2, IL-4, IL-10 and TNF-α were produced by CIK cells (Fig. 6E), suggesting that compared with IL-2, IL-4, IL-10 and TNF-α, IFN-γ and IL-6 might play an important role in tumor-killing activity of CIK cells against NPC cells. This evidence concerns the gene IFNG and nasopharyngeal carcinoma.