EFFICACY OF MULTIPLE ADMINISTRATIONS OF A RECOMBINANT ADENOVIRUS EXPRESSING WILD-TYPE P53 IN AN IMMUNE-COMPETENT MOUSE-TUMOR MODEL

Infection of Renca cells in vitro with a recombinant adenovirus expres sing a marker gene beta-galactosidase resulted in high level of the tr ansgene expression. Renca tumors grown in Balb/C mice were also infect able with this recombinant adenovirus. The transgene expression in the tumors of Ad-beta gal, on day 7 produced beta-galactosidase for about 7 days, however, administration of another dose of AD-beta gal, on da y 7 produced beta-galactosidase expression. To investigate the effect of antibodies to adenovirus were injected with multiple doses of adeno virus to produce neutralizing antibodies. To these animals Renca cells were injected and tumors formed. Interestingly, when Ad beta-gal was administered into these tumors, a high level of transgene expression w as still observed. We next explored the utility of a recombinant adeno virus expressing p53 (AdWTp53) in the Renca tumor model. Renca cells w hen exposed to an adenovirus expressing p53 (AdWTp53) produced a high level of p53 protein, a p53-inducible gene p21/WAF1/Cip1 and underwent apoptosis. A single injection of AdWTp53 (10(9) plaque forming units) resulted in significant inhibition of tumor growth. However, multiple administrations (four doses of 2.5 x 10(8) plaque forming units) of A dWTp53 were needed for tumor cures. Mixing uninfected and AdWTp53-infe cted cells showed a bystander effect of AdWTp53-infected Renca cells. Based on these results we believe that an appropriate dose scheduling of AdWTp53 can be efficacious for cancer gene therapy in immune-compet ent tumor-bearing animals.