Human IL-18, IL-2 and the fusion gene IL18-IL2 were obtained by PCR, inserted into pBV220 vector and expressed in BL21 (DE3) by 42 ??C heat induction.     ///    "Anti asialo GM1 could reduce natural killer cell cytotoxicity, production of IFN-?, and regression of LLC tumor aroused by IL18-IL2. "    ///    "IL18-IL2 was confirmed by Western blot, and its molecular weight was about 34.5 kDa. "    ///    "IL18-IL2 could significantly enhance production of IFN-? in PBMCs in vitro and induce significant tumor regression in tumor-bearing mouse models of LLC, NCI-H460 and HCT-116 than that of IL-18 and IL-2 separately or combination using. "    ///    The biological activity of IL18-IL2 was first determined by its ability to augment IFN-? production in PBMCs.     ///    "Then tumor-bearing mouse models of mouse Lewis lung carcinoma (LLC), human large cell lung carcinoma (NCI-H460) and human colorectal carcinoma (HCT-116) were established to investigate the antitumor activity and mechanism of IL18-IL2. "    ///    "In the mice bearing HCT-116 and LLC, IFN-? concentrations and natural killer cell cytotoxicity were highly enhanced by IL18-IL2. "    ///     To obtain a human IL18-IL2 fusion protein by genetic engineering methods and investigate its antitumor activity and mechanism in tumor-bearing mouse models.     ///    "These results suggested the IL18-IL2 fusion protein showed a synergetic effect on tumor regression, which was related to the great ability of IL18-IL2 in enhancing IFN-? production and natural killer cell cytotoxicity. "