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

Summary 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 (D ₀) 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,D ₀, were calculated for each cell strain and each wavelength range. When comparingD ₀ 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-meanD ₀ 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%.Abbrevations UV ultraviolet light - UV-A, UV-B, UV-C UV light with wavelengths in the ranges 320–400 nm, 290–320 nm, and 230–290 nm - D ₀ (in J/m²) to give 37% colony-forming ability     

Xeroderma pigmentosum patients from Germany: repair capacity of 45 XP fibroblast strains of the Mannheim XP Collection as measured by colony-forming ability and unscheduled DNA synthesis following treatment with methyl methanesulfonate and N-methyl-N-nitrosourea

Summary A total of 45 XP fibroblast strains from the Mannheim XP Collection (representatives of XP complementation groups A, C, D, E, F or G, I, and XP variants) were investigated for colony-forming ability (term: D₀ after treatment with up to ten doses of the methylating carcinogen MeSO₂OMe. As controls 16 fibroblast strains from normal donors were used. Except for 4 XP strains (1 from group C and 3 from group D) which, however, were borderline cases, none of the remaining 41 XP strains was found to be more sensitive than normal controls. This held true within the limits of an experimental accuracy (experimental variability of D₀ values) of ±7%. When weighted means were calculated for XP complementation groups and compared with that of normal donors at a significance level of 5%, no significant difference was detected. In contrast, after exposure of 6 XP group D strains to MeNOUr, a weighted mean D₀ value was obtained which was significantly decreasd by 27%. Unscheduled DNA synthesis (term: G₀ which serves as a measure of excision repair) after exposure to MeNOUr was quantitatively the same (exposure to MeNOUr was quantitatively the same (experimental varability: ±8%) both in the group of normal strains and in most of the XP complementation groups. Exceptions were group E and group F (or G) which had higher, and group I which had lower repair. Analogous G₀ values measured after exposure to MeSO₂OMe (experimental variability: ±13%), however, differed from that of the control strains: they were lower in XP complementation groups A, D, E, F (or G), and I. However, groups A, E, F (or G), and I including only 3 individual strains or less may be considered to be possibly ill-represented. Yet, group D including 11 XP strains did show reduction of the mean G₀ value by 35%. From this it is concluded that there are repair defects in XP group D strains with regrad to MeSO₂OMe-induced adducts. These defects seem to be small.Abbreviations XP xeroderma pigmentosum - MeSO₂OMe methyl methanesulfonate - MeNOUr N-methyl-N-nitrosourea - Me(NO)(NO₂)Gdn N-methyl-N-nitro-N-nitrosoguanidine - HEPES N-2-hydroxyethyl-piperazine-N-2-ethanesulfonic acid This work was supported by the Deutsche Forschungsgemeinschaft, SFB 136     

DNA repair synthesis in fibroblast strains from patients with actinic keratosis,squamous cell carcinoma,basal cell carcinoma,or malignant melanoma after treatment with ultraviolet light,N-acetoxy-2-acetyl-aminofluorene,methyl methanesulfonate,and N-methyl-N-nitrosourea

Summary Fibroblast strains derived from skin biopsies of patients with actinic keratosis (6), malignant melanoma (18), squamous cell carcinoma (11), and basal cell carcinoma (12) were investigated for DNA repair synthesis, with 16 fibroblast strains for normal donors as controls. Cells were exposed to UV light, the UV-like carcinogen (Ac)₂ONFln, and the methylating carcinogenes MeSO₂OMe and MeNOUr. Dose-response experiments, which included 10 dose levels, were performed, the data analyzed by linear regression, and the slope of the regression line (term: G ₀) used as a measure of DNA repair synthesis. The mean experimental variability of G ₀ of individual fibroblast strains was 9.5%–15.4%, depending upon exposure. For comparison of all cell strains belonging to the same skin malignancy group with those of the control group, G ₀ values of the individual strains were combined to yield group-specific weighted mean G ₀ values.In addition, the capacity to incise UV-damaged DNA was measured in 24 cell strains from patients with skin tumors using the alkaline elution technique. For quantitating DNA-incising capacity, the initial velocities of the elution curves were plotted versus the UV dose, and the slope of the resulting regression line was used to obtain the characteristic value E ₀. The mean experimental variability of E ₀ of individual strains was ±22%. These E ₀ values were combined to yield weighted mean values of groups.The fibroblast strains in the groups of patients with actinic keratosis and malignant melanoma were found to have normal mean G ₀ values when DNA repair synthesis was challenged with UV light or one of the three carcinogens. However, the squamous cell carcinoma group exhibited significantly lower mean G ₀ values after treatment with UV light (82% that of normal donors), (Ac)₂ONFln (70%), MeSO₂OMe (70%), and MeNOUr (69%). The basal cell carcinoma group showed significantly diminished repair synthesis upon treatment with UV light (81% that of normal donors) and MeSO₂OMe (67%). In contrast to these findings, in no skin malignancy group was post UV DNA-incising capacity (E ₀) significantly diminished, although it should be noted that group sizes were only half as large as for G ₀ determinations.These data may be interpreted as indicating that DNA excision repair is impaired in fibroblast strains from patients with squamous cell carcinoma and — to a lesser extent — basal cell carcinoma. This deficiency seems to pertain to several DNA repair mechanisms, as excision of both alkylation and UV-induced damage is involved. Although the repair impairments are statistically significant, the relative risks at which the investigated patients are do not seem to be high enough as to be of immediate practical value. Our results indicate further studies would be useful.Abbreviations XP xeroderma pigmentosum - UV light ultraviolet light - UVB UV light with the wavelength from 290 nm to 320 nm - (Ac)₂ONFln N-acetoxy-2-acetylaminofluorene - MeSO₂OMe methyl methanesulfonate - MeNOUr N-methyl-N-nitrosourea - ara-C 1--d-arabinofuranosyl cytosine This work was supported by the Deutsche Forschungsgemeinschaft, SFB 136Dedicated to Professor E. Hecker on the occasion of his 60th birthday