Fibroblasts derived from patients with dysplastic nevus syndrome are not more sensitive towards 254-nm and 312-nm ultraviolet light than fibroblasts from normal donors.

DNA repair capacity of 18 fibroblast strains from patients with dysplastic nevus syndrome, 5 of them with malignant melanoma, was investigated and their colony-forming ability (D0) after UV exposure was determined as a measurement of this. Seventeen fibroblast strains from normal donors served as controls. The dose/response experiments included up to 11 dose levels and two UV wavelength ranges: UV-C (using a low-pressure mercury lamp emitting predominantly 254-nm light) and UV-B (artificial "sunlamp" radiation centering around 312-nm light). The exponential segments of the dose/response curves were analysed by linear regression and the negative reciprocals of the regression coefficients, D0, were calculated for each cell strain and each wavelength range. When comparing D0 values of individual cell strains from patients with and without melanomas with the mean value for all normal donors, only 4 out of 18 showed increased sensitivity towards UV-B. This difference, however, was not statistically significant. On the contrary, weighted-mean D0 values for fibroblast strains from patients with and without melanoma were found to be slightly but significantly higher than those for normal donors (significance level: 5%), indicating that cell strains from these patients were less sensitive to UV light (UV-C and UV-B) of both wavelength. This result, which on the basis of current literature data is somewhat unexpected, holds true within the limits of experimental accuracy of +/- 12%.