Reduction of tumorigenicity of SMMC-7721 hepatoma cells by vascular endothelial growth factor antisense gene therapy

AIM: To test the hypothesis to block VEGF expression of SMMC-7721 hepatoma cells may inhibit tumor growth using the rat hepatoma model. METHODS: Amplify the 200 VEGF cDNA fragment and insert it into human U6 gene cassette in the reverse orientation transcribing small antisense RNA which could specifically interact with VEGF165, and VEGF121 mRNA. Construct the retroviral vector containing this antisense VEGF U6 cassette and package the replication-deficient recombinant retrovirus. SMMC-7721 cells were transduced with these virus and positive clones were selected with G418. PCR and Southern blot analysis were performed to determine if U6 cassette integrated into the genomic DNA of positive clone. Transfected tumor cells were evaluated for RNA expression by ribonuclease protection assays. The VEGF protein in the supernatant of parental tumor cells and genetically modified tumor cells was determined with ELISA. In vitro and in vivo growth properties of antisense VEGF cell clone in nude mice were analyzed. RESULTS: Restriction enzyme digestion and PCR sequencing verified that the antisense VEGF RNA retroviral vector was successfully constructed.After G418 selection, resistant SMMC-7721 cell clone was picked up. PCR and Southern blot analysis suggested that U6 cassette was integrated into the cell genomic DNA. Stable SMMC-7721 cell clone transduced with U6 antisense RNA cassette could express 200 bp small antisense VEGF RNA and secrete reduced levels of VEGF in culture condition. Production of VEGF by antisense transgene-expressing cells was 65+/-10 ng/L per 10(6) cells, 42045 ng/L per 10(6) cells in sense group and 485+/-30 ng/L per 10(6) cells in the negative control group, (P【 0.05). The antisense-VEGF cell clone appeared phenotypically indistinguishable from SMMC-7721 cells and SMMC-7721 cells transfected sense VEGF. The growth rate of the antisense-VEGF cell clone was the same as the control cells. When S.C. was implanted into nude mice, growth of antisense-VEGF cell lines was greatly inhibited compared with control cells. CONCLUSION: Expression of antisense VEGF RNA in SMMC-7721 cells could decrease the tumorigenicity, and antisense-VEGF gene therapy may be an adjuvant treatment for hepatoma.

AIM To test the hypothesis to block VEGFexpression of SMMC-7721 hepatoma cells mayinhibit tumor growth using the rat hepatomamodel.METHODS Amplifiy the 200 VEGF cDNAfragment and insert it into human U6 genecassette in the reverse orientation transcribingsmall antisense RNA which could specificallyinteract with VEGF165, and VEGF121 mRNA.Construct the retroviral vector containing thisantisense VEGF U6 cassette and package thereplication-deficient recombinant retrovirus.SMMC-7721 cells were transduced with thesevirus and positive clones were selected withG418. PCR and Southern blot analysis wereperformed to determine if U6 cassette integratedinto the genomic DNA of positive clone.Transfected tumor cells were evaluated for RNAexpression by ribonuclease protection assays.The VEGF protein in the supernatant of parentaltumor cells and genetically modified tumor cellswas determined with ELISA. In vitro and in vivogrowth properties of antisense VEGF cell clonein nude mice were analyzed.RESULTS Restriction enzyme digestion andPCR sequencing verified that the antisense VEGFRNA retroviral vector was successfullyconstructed. After G418 selection, resistantSMMC-7721 cell clone was picked up. PCR andSouthern blot analysis suggested that U6cassette was integrated into the cell genomicDNA. Stable SMMC-7721 cell clone transducedwith U6 antisense RNA cassette could express200bp small antisense VEGF RNA and secretereduced levels of VEGF in culture condition.Production of VEGF by antisense transgeneexpressing cells was 65 ± 10 ng / L per 106 cells,420 ± 45 ng/L per 106 cells in sense group and 485± 30 ng/L per 106 cells in the negative control group, (P＜0.05). The antisense-VEGF cell clone appeared phenotypically indistinguishable from SMMC-7721 cells and SMMC-7721 cells transfected sense VEGF. The growth rate of the antisense-VEGF cell clone was the same as the control cells. When S. C. was implanted into nude mice, growth of antisense-VEGF cell lines was greatly inhibited compared with control cells.CONCLUSION Expression of antisense VEGFRNA in SMMC-7721 cells could decrease thetumorigenicity, and antisense-VEGF genetherapy may be an adjuvant treatment forhepatoma.