Human IL18-IL2 fusion protein as a potential antitumor reagent by enhancing NK cell cytotoxicity and IFN-γ production

To obtain a human IL18-IL2 fusion protein by genetic engineering methods and investigate its antitumor activity and mechanism in tumor-bearing mouse models. 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 A degrees C heat induction. Purified proteins were analyzed by SDS-PAGE and Western blot. The biological activity of IL18-IL2 was first determined by its ability to augment IFN-gamma 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. IL18-IL2 was confirmed by Western blot, and its molecular weight was about 34.5 kDa. IL18-IL2 could significantly enhance production of IFN-gamma 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. In the mice bearing HCT-116 and LLC, IFN-gamma concentrations and natural killer cell cytotoxicity were highly enhanced by IL18-IL2. Anti asialo GM1 could reduce natural killer cell cytotoxicity, production of IFN-gamma, and regression of LLC tumor aroused by IL18-IL2. 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-gamma production and natural killer cell cytotoxicity. The fusion protein was a potential antitumor reagent in cancer immunotherapy.