OBJECTIVETo investigate the selectively killing effect of adenovirus (Ad) mediated double suicide gene under the regulation of KDR promoter on vascular endothelial cells and colorectal tumor cells.

METHODS293 packaging cells were transfected with the plasmids of pAdEasy- KDR- CDglyTK and pAdEasy- CMV- CDglyTK and the infectious viruses were generated. The KDR expressive cells of ECV304,SW620 and the KDR inexpressive cells of LS174T were infected by two Ads. The infection rate was observed and the expression of CDglyTK was detected by RT- PCR. After treatment with different concentrations of 5- FC and GCV,the killing effect and bystander effect on ECV304,SW620 and LS174T were examined.

RESULTSThe titers of these two purified Ads were 2.0 x 10(12 ) pfu/ml. There was no significant difference in infection rate between two recombinant Ads infecting various cells,and the infection rate increased in accordance with the enhancing titers of Ads. RT- PCR demonstrated that there existed the product of CDglyTK gene in all the cells infected by Ad- CMV- CDglyTK and the cells infected by Ad- KDR- CDglyTK except in the SL174T. The curative effect in this system on various cells was shown as follows: (1) All cells infected with Ad- CMV- CDglyTK and some cells of ECV304 and SW620 infected with Ad- KDR- CDglyTK were highly sensitive to the prodrugs,but there was no significant differences among them (P > 0.05); compared with ECV304 and SW620 cells,LS174T cells were not sensitive to the two prodrugs (P< 0.001). (2) The efficacy of double suicide gene was better than that of single suicide gene (P< 0.001). (3) The system had considerable bystander effect.

CONCLUSIONThe double suicide gene under the regulation of KDR promoter has specific killing effect on the KDR- expressing endothelial cells and colorectal tumor cells.