Levels and repair of cyclobutane pyrimidine dimers and 6-4 photoproducts in skin of sporadic basal cell carcinoma patients

The P-32-postlabeling method was applied to measure directly the levels and repair rates of specific cyclobutane pyrimidine dimers and 6-4 photoproduc ts in 10 basal cell carcinoma patients and 10 controls matched on age, skin type, and gender after exposure to 400 J per m(2) of solar simulating radi ation on previously unexposed buttock skin. The results showed an identical level of photoproducts at 0 h after solar simulating radiation in the basa l cell carcinoma group and the control group. Erythemal response correlated with the repair of cyclobutane pyrimidine dimers within 24 h in both group s, i.e., repair was faster in those with a strong erythemal reaction. The b asal cell carcinoma patients showed a somewhat slower repair of photoproduc ts in skin compared with the controls, but the result was not significant. Photoproducts formed at the TTC sites were repaired faster than those at th e TTT sites for both cyclobutane pyrimidine dimers and 6-4 photoproducts in the basal cell carcinoma group and in the controls.