Abstract: BACKGROUND AND AIM: To study the antitumor effect of colon26 cells transfected with 4_1BBL gene in vivo. MATERIALS AND METHODS: The eukaryotic expression vector pMKIT/4_1BBL was transfected into colon26 cells with lipofectamine, The transfected cells were selected by G418 and termed colon26/4_1BBL. Then the tumor cell vaccine(TCV) was obtained by treatment with MMC. Three mice models (colon26, colon26/pMKITneo , and colon26/4_1BBL ) were established to study the antitumor effects of TCV_4_1BBL. The cytolytic activity of CTL and NK were detected by variable MTT method. The content of IL_2 and IFN_γ in serum were measured by ELISA . The early cancer model was made by inoculating colon26, then the mice were treated with TCV_4_1BBL on the second and seven days. RESULTS: Compared with colon26 and colon26/pMKITneo, colon26/4_1BBL cells grew much slower in mice. Mostly syngeneic mice were protected by inoculation with TCV_4_1BBL, survived free from tumor for a long period (over 100 days). The cytolytic effect of CTL and NK in colon26/4_1BBL mice were improved significantly, and the contents of IL_2 and IFN_γ were also increased. Cured by TCV_4_1BBL,some mice could survive free from tumor,and other bearing_tumor mice whose tumor grew slowly.The survival periods of all these mice were significantly prolonged. CONCLUSION: The antitumor effect against syngeneic marine colon carcinoma and the immune response in vivo were obviously enhanced by treating them with TCV_4_1BBL.

Key words: gene transfer, tumor cell vaccine(TCV), antitumor effect, 4_1BBL