Adenovirus-mediated wild-type p53 gene expression radiosensitizes non-small cell lung cancer cells but not normal lung fibroblasts

Purpose: We compared the ability of adenoviral-mediated wild-type p53 RPR/I NGN201 (Ad5/CMV/p53) to radiosensitize non-small cell lung carcinoma (NSCLC ) and normal lung fibroblast cells. Materials and methods: NSCLC cell lines (A549 and H322) and human lung fibr oblast cells (MRC-9 and CCD-16) were used in this study. Radiosensitivity w as determined by clonogenic assay and tumor growth delay. Expression of p53 , Bax, and p21(WAF1) protein were evaluated by immunoblot. A FITC conjugate of annexin V was used for flow cytometric detection of apoptosis. Results: Clonogenic and apoptotic assays indicated that Ad5/CMV/p53 enhance d the radiosensitivity of both NSCLC cell lines. On the other hand, the two normal human fibroblast cell lines appeared to be resistant to the cytotox ic effects of Ad5/CMV/p53 and were not radiosensitized compared to the NSCL C cells. According to immunoblot analysis, Bax expression was increased in the NSCLC cells treated with the combination therapy; Bax expression, howev er, was unchanged in normal cells. In in vivo studies, tumor growth suppres sion was enhanced by this combination strategy in xenograft tumors growing in nude mice compared to Ad5/CMV/p53 or radiation therapy when used alone. Conclusions: Our data indicate that therapy using Ad5/CMV/p53 and irradiati on in combination is more effective than either treatment when used alone o n NSCLC cells, is not limited to cells with defective endogenous p53, and d oes not enhance the radiosensitivity of normal cells.