Epidemiology of ultraviolet-DNA repair capacity and human cancer.

The following conclusions are derived from an epidemiological study. Reduced repair of ultraviolet (UV)-induced DNA damage contributes directly to basal cell carcinoma (BCC) in individuals with prior sunlight overexposure. A family history of BCC is a predictor of low DNA repair. Repair of UV-damaged DNA declines at a fixed rate of approximately 1% per annum in noncancerous controls. The DNA repair differences between young BCC cases and their controls disappear as they age. Hence, BCC, in terms of DNA repair, is a premature aging disease. The persistence of photochemical damage because of reduced repair results in point mutations in the p53 gene and allelic loss of the nevoid BCC gene (Gorlin's syndrome) located on chromosome 9q. The fact that environmental vulnerability is gender oriented implicates hormones in regulating DNA repair. Xeroderma pigmentosum appears to be a valid paradigm for the role of DNA repair in BCC in the general population.