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¹ Departments of Experimental Radiation Oncology and ² Thoracic and Cardiovascular Surgery, University of Texas MD Anderson Cancer Center, Houston, TX

Requests for reprints: Raymond E. Meyn, Department of Experimental Radiation Oncology, Unit 066, University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030. Phone: (713) 792-3424; Fax: (713) 794-5369. E-mail: rmeyn{at}mdanderson.org

Functional inactivation of the p53 gene and robust DNA repair capacity may be among the salient causes of radioresistance in tumor cells. We expressed the wild-type (wt) p53 gene in a p53-mutant human epidermoid carcinoma cell line, A431, using an adenoviral vector [adenovirus-p53 (Ad-p53), INGN 201], examined its radiosensitivity, and correlated p53 status and radiosensitivity with cellular repair functions. Using clonogenic survival assays and the terminal deoxynucleotidyl transferase-mediated nick end labeling assay for apoptosis, we demonstrated that preirradiation treatment with Ad-p53 significantly increased the radiosensitivity of A431 cells over controls. Induction of p53 expression using a construct where p53 expression was under the control of an inducible promoter also significantly increased radiosensitivity of H1299 lung tumor cells, which are otherwise null for p53. These results did not correlate with radiation-induced apoptosis but did correlate with functional impairment of DNA repair and suppressed expression of several repair-related genes, such as Ku70, DNA-dependent protein kinase, ataxia telangiectasia mutated, and X-ray-sensitive complementation group 4. Normal human fibroblast MRC-9 cells showed no impairment in the repair capability due to Ad-p53 despite the suppression of some repair genes. Expression of Ku70, which is known to mediate diverse cellular functions, correlated with the differential effects of p53 on radiosensitivity in the normal and tumor cells.

Grant support: P01 CA78778, P01 CA06294, and P30 CA 16672 from the National Cancer Institute.

Present address: Dr. Nand K. Sah, Department of Botany, RD College, Sheikhpura 811105, India.

¹ T. Nishikawa, A. Munshi, M. D. Story, S. Chada, and R. E Meyn. Adenoviral-mediated MDA-7 expression suppresses DNA repair capacity and radiosensitizes a non-small cell lung cancer cells, manuscript in preparation.

Received 5/15/03; revised 8/ 8/03; accepted 8/28/03.

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