IL18 and cancer: NK cells participate in both innate and adaptive immunity.21 They play an important role in immune surveillance against local tumor growth and metastasis by direct cellular cytotoxicity; thus lower NKCC is associated with increased cancer metastasis.21,22 Antitumor responses in NKCC are activated by various cytokines, such as IL-1, IL-2, IL-12, IL-15, IL-18, IL-21, and type I interferons.21,22 As IL-2-activated human NK cells can effectively kill colon carcinoma cells in vitro,23 we investigated IL-2 for this study.