Expression of genes involved in repair of DNA double-strand breaks in normal and tumor tissues

Background: DNA double-strand breaks (DSB) are the major lethal lesions ind uced by ionizing radiation. The capability for DNA DSB repair is crucial fo r inherent radiosensitivity of tumor and normal cells. DNA-PKcs, Ku 70, Ku 85, Xrcc4, and Nbsl play a critical role in DNA DSB repair. Methods: We immunohistochemically investigated the expression of DNA-PKcs, Ku 70, Ku85, Xrcc4, and Nbsl in 134 specimens from various normal and tumor tissues with different radiosensitivity. Results and Conclusion: Immunopositivity to Ku70, Ku85, DNA-PKcs, Xrcc4, an d Nbsl was found in all tumor tissues examined. The staining for Ku70, Ku85 , and DNA-PKcs was nuclear; but, for Xrcc4 and Nbsl, it was nuclear and cyt oplasmic. There were no apparent differences in the expression of these fiv e proteins among cancerous tissues and the corresponding normal tissues. No apparent differences in nuclear staining intensity were detected in the ex pression of these five proteins among tumor tissues with different radiosen sitivity, although non-Hodgkins' lymphoma (B or T cell) tended to show a lo wer expression than the others. The stromal cells generally expressed these five proteins at much lower frequency than either tumor or epithelial cell s in both tumor and normal tissues. (C) 2001 Elsevier Science Inc.