Gene therapy of brain tumors: Biological effects of recombinant adenovirus containing wild-type p53 gene in human glioma cells and in vivo

The prognosis of patients with malignant glioma, the most common primary brain tumor is grim despite contemporary surgery, radiation, and chemotherapy. New approaches for the treatment of brain tumors are urgent. The p53 tumor suppressor gene is one of the genes with greatest potential for cancer treatment. We evaluated the biological effects of the recombinant adenovirus containing the wild-type p53 cDNA (Ad5CMV-p53) in human glioma cell lines and in rat brains. Monolayer cell cultures of the cell lines (U-251 and LG expressing endogenous mutant p53, and EFC-2 expressing wild-type p53) were treated with various doses of 10-1,000 plaque forming unit (PFU). Viral infection efficiency, gene transfer and expression level as well as growth inhibitor effect were determined using β-galactosidase histochemistry, immunoblotting, and growth curve assay, respectively. We injected Ad5CMV-P53 of various doses (107-109 PFU in 5 μl) into rat brains and examined the toxicity to brains and other major organs. Infection efficiency was 80-90% in U-251 and EFC-2 cells, and 42% in LG cells at 25 MOI. Introduction of Ad5CMV-p53 inhibited the growth of U-251 and EFC-2 cells (>85% inhibition), and LG cells (36% inhibition). Local administration of Ad5CMV-p53 into the brain showed no evidence of toxicity to the extracranial major organs but the doses higher than 107 PFU demonstrated inflammatory reaction to the brain. These results suggest that Ad5CMV-p53 infects human glioma cells and transduces with high efficiency the p53 gene, and dose optimization is of importance in the design of safe gene therapy for brain tumors.