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Repair and Replication of DNA in Hereditary (Bilateral) Retinoblastoma Cells after X-Irradiation¹

Laboratory of Radiobiology and Environmental Health [J. E. C., W. C. C.], and Ocular Oncology Unit [D. C., N. R.], University of California, San Francisco, California 94143

Fibroblasts from patients with hereditary retinoblastoma reportedly exhibit increased sensitivity to killing by X-rays. Although some human syndromes with similar or greater hypersensitivity to DNA-damaging agents (e.g., X-rays, ultraviolet light, and chemical carcinogens), such as xeroderma pigmentosum, are deficient in DNA repair, most do not have such clearly demonstrable defects in repair. Retinoblastoma cells appear to be normal in repairing single-strand breaks and performing repair replication after X-irradiation and also in synthesizing poly(adenosine diphosphoribose). Semiconservative DNA replication in these cells, however, is slightly more resistant than normal after X-irradiation, suggesting that continued replication of damaged parental DNA could contribute to the pathogenesis of the disease. This effect is small, however, and may be a consequence rather than a cause of the fundamental enzymatic abnormality in retinoblastoma that causes the tumorigenesis.

¹ This work was supported by the United States Department of Energy and Grants EYD1441, 1759, and 3675 from the NIH.

² To whom requests for reprints should be addressed.

Received 10/ 7/81. Accepted 1/ 8/82.