Potential of adenoviral p53 gene therapy and irradiation for the treatmentof malignant gliomas

We investigated the combined effects of p53 gene transfer and irradiation a nd its still unclear interaction mechanism in human gliomas. Four human gli oma cell lines expressing mutant type p53 (U373 and A172) and wildtype p53 (D54MG and EFC-2) were transfected by adenoviral vectors bearing p53 gene a t 50 multiplicity of infection. Two days after transfection, cells were irr adiated (3, 6, and 9 Gy). The cytotoxicity was evaluated by clonogenic assa y. The quantitative analysis of apoptosis and cell cycle analysis were perf ormed using flow cytometry. Irradiation combined with adenoviral p53 transf ection significantly increased cytotoxicity, which was additive in cell lin es with wild-type p53 and more than additive in cell lines with mutant p53. The combination of two modalities increased the apoptotic population by 14 % in A172 cells and 20% in D54 MG cells, which were the sum of apoptosis fr om each modality. Adenoviral p53 transfection increased the GI phase fracti on and concomitant decrease of radioresistant S phase fraction in A172 and D54MG cells. Our study demonstrated that p53 gene transfer combined with ir radiation increased absolute cytotoxicity in human glioma cells used in thi s experiment. The interaction mechanism for increased cytotoxicity involved , in part, increased apoptosis and change of cell cycle profile.