AIM:To observe the anti-liver cancer activity of tumornecrosis factor-related apoptosis-inducing ligand (TRAIL)gene and its bystander effects on hepatocellular carcinoma(HCC) cell line SMMC7721.METHODS:Full-length cDNA of human TRAIL was transferredinto SMMC7721 cells with a binary adenoviral vector system.Polymerase-chain reaction following reverse transcription(RT-PCR) was used to determine the expression of TRAILgene.Effects of the transfected gene on proliferation ofSMMC7721 cells were measured by MTT assay.Its influenceon apoptosis was demonstrated by fluorescence-activatedcell sorting (FACS).The bystander effect was observed byco-culturing the SMMC7721 cells with and without thetransfected TRAIL gene at different ratios,and the culturemedium supernatant from the transfected cells was alsoexamined for its influence on SMMC7721 cells.RESULTS:The growth-inhibition rate and apoptotic cellfraction in the cells transfected with the TRAIL gene,Baxgene or only LacZ gene were 91.2%,48.0%,28.8% and29.1%,12.5%,6.6%,respectively.The growth-inhibitionrate of transfection with these three sequences in normalhuman fibroblasts was 6.1%,45.5% and 7.6%,respectively,indicating a discriminative inhibition of TRAIL transfectionon the cancer cells.In the co-culturing test,addition of thetransfected TRAIL to SMMC7721 cells in proportions of 5%,25%,50%,75% and 100%,resulted in a growth-inhibitionof 15.9%,67%,80.2%,86.4% and 87.7%,respectively.We failed to observe a significant growth-inhibition effect ofthe culture medium supernatant on SMMC7721 cells.CONCLUSION:TRAIL gene transferred by a binary adenoviralvector system can inhibit proliferation of SMMC7721 cellsand induce their apoptosis.A bystander effect was observed,which seemed not to be mediated by soluble factors. AIM: To observe the anti-liver cancer activity of tumornecrosis factor-related apoptosis-inducing ligand (TRAIL) gene and its bystander effects on hepatocellular carcinoma (HCC) cell line SMMC7721.METHODS: Full-length cDNA of human TRAIL was transferred in SMMC7721 cells with a binary adenoviral vector system. Polymerase-chain reaction following reverse transcription (RT-PCR) was used to determine the expression of TRAILgene. Effects of the transfected gene on proliferation of SMMC7721 cells were measured by MTT assay. Its influenceon apoptosis was demonstrated by fluorescence -activated cell sorting (FACS) .The bystander effect was observed byco-culturing the SMMC7721 cells with and without thetransfected TRAIL gene at different ratios, and the culturemedium supernatant from the transfected cells was alsoexamined for its influence on SMMC7721 cells. RESULTS: The growth- inhibition rate and apoptotic cell fraction in the cells transfected with the TRAIL gene, Baxgene or only LacZ gene were 91.2%, 48.0% 28.8% and29.1%, 12.5%, 6.6%, respectively. The growth-inhibition rate of transfection with these three sequences in normalhuman fibroblasts was 6.1%, 45.5% and 7.6%, respectively, indicating a discriminative inhibition of TRAIL transfection of the cancer cells In the co-culturing test, addition of the transfected TRAIL to SMMC7721 cells in proportions of 5%, 25%, 50%, 75% and 100%, resulted in a growth-inhibition of 15.9%, 67%, 80.2%, 86.4% and 87.7%, respectively. We failed to observe a significant growth-inhibition effect of the culture medium supernatant on SMMC7721 cells. CONCLUSION: TRAIL gene transferred by a binary adenoviral vector system can inhibit proliferation of SMMC7721 cells and induce their apoptosis. A bystander effect was observed, which seemed not to be mediated by soluble factors.