Adenovirus mediated double suicide gene inducing cell apoptosis in breast cancer cells

[Objective] To study the selective killing effect of adenovirus (Ad)-mediated fusion gene system driven by human vascular endothelial growth factor (VEGF) promoter on human breast cancer MCF-7 cells and observe whether apoptosis can be induced. [Methods] The VEGF-expressing MCF-7 cells and non VEGF-expressing normal human mammary epithelial cells in primary culture were infected by the Ad-VEGFP-CD/TK.The infection efficiencies were observed under a fluorescence microscope. The expression of CD/TK gene was detected by RT-PCR. The toxic effect induced by giving the prodrug 5-fluorocytosine (5-FC) and ganciclovic(GCV) were determined by light microscopy and flow cytometry (FCM). An animal model of human breast cancer in nude mice was reproduced. The treatment effect was observed in each group. Then pathological character of tumor growth cells were observed by electronmicroscopy. [Results] The green fluorescent protein(GFP) were observed in the 95 percent of the infected MCF-7 and human mammary epithelial cells when the multiple of infection(MOI) of the Ads are 100. RT-PCR demonstrated that there existed the expression of CD/TK gene in MCF-7 cells infected by Ad-VEGFP-CDTK, while the infected human mammary epithelial cells were not. The progrug could induce apoptosis of MCF-7/CDTK under inverted microscope. Apoptotic peak was also shown in pro-drugs group by flow cytometry. In vivo, tumor growth was dramatically inhibited in treated group. It was no significant difference among the other groups. Morphologic features of xenografts cell apoptosis in the group treated with prodrug were displayed via electron microscopy. [Conclusions] The CD/TK fusion gene system controlled by VEGF promoter have selectively killing effect on MCF-7 cells and inducing the cell apoptosis in vitro and vivo.