ObjectiveTo investigate the feasibility of using cytokine-induced killer (CIK) cells as targeted vehicle to deliver hIL-21 gene for hepatocellular carcinoma (HCC) treatment. MethodsWe constructed pDC759-hIL-21 and pDC759-CopGFP for cotransfection of HEK293 cells with pAd5 and pAd5F35 which can express hIL-21 and CopGFP proteins for viral packaging. We isolated CIK cells and plotted the growth curve. Then Ad5/AAV-CopGFP and Ad5F35/AAV-CopGFP of different MOIs (0,1,5,10,50,100, and 1 000) were used to infect CIK cells; Ad5/AAV-hIL-21 and Ad5F35/AAV-hIL-21 of different MOIs (0,1,5,10,20, and 50) were used to infect SMMC-7721 cells and the hIL-21 protein levels were examined by ELISA assay 48 h after infection. Ad5F35/AAV- hIL-21 of different MOIs (0, 1, 5, 10, 50, and 100) was used to infect CIK cells and hIL-21 protein levels were also examined 48 h after infection. SMMC-7721 cells were subcutaneously injected to nude mice for tumor forming, and then the tumor-bearing mice were treated with CIK cells carrying hIL-21 and the therapeutic effects were observed. ResultsPlasmids for viral packaging were constructed. After cotransfection of HEK293 cells, Ad5 and Ad5F35 which can express hIL-21 and CopGFP proteins were successfully packaged. Ad5 and Ad5F35 which can express CopGFP were used in this study. It was found that Ad5F35 was superior to Ad5 in CIK infection, with the suitable MOI being 50. Ad5/AAV-hIL-21 and Ad5F35/AAV-hIL-21 had similar effect on IL-21 expression in SMMC-7721 cells. Results of animal study showed that mice in group CIK/hIL-21 had a better curative effect. ConclusionhIL-21 and CIK cells have synergistic anti-tumor effect in nude mice bearing HCC.