Low DNA repair is a risk factor in skin carcinogenesis: a study of basal cell carcinoma in psoriasis patients

We have studied DNA repair in patients with psoriasis aiming at investigati ng the importance of repair in chemically induced cancer. An increased risk of non-melanoma skin cancer has been observed in psoriasis patients extens ively treated with tar, methotrexate and photochemotherapy (psoralen + WA). We measured the DNA repair capacity (DRC) by a host cell reactivation (HCR ) assay in lymphocytes from psoriasis patients with and without basal cell cancer and non-psoriatic persons with and without basal cell cancer (4 x 20 study persons). Among psoriasis patients we observed a significant lower D RC in patients with skin cancer compared to patients without skin cancer(P = 0.015; Mann-Whitney, one-sided). Using the median of the healthy control group (group 4) as a cutoff value to divide the psoriasis patients into gro ups of high and low repair, we found that individuals who had a low repair capacity had a 6.4-fold increased skin cancer risk compared to individuals with high repair (95% confidence interval (CI), 1.44-28.5). The level of DN A repair was correlated with the age at which the psoriasis patients got th eir first skin cancer. The lower the level of DNA repair, the earlier the p soriasis patients had their first skin tumor (P = 0.070 Spearman; one-sided ). Psoriasis patients without BCC had marginally higher repair than healthy controls (P = 0.11, Mann-Whitney, two-sided). We found no difference betwe en BCC patients without psoriasis and healthy controls. In conclusion, thes e findings suggest a protective role of DNA repair in a predominantly chemi cally induced cancer. (C) 1999 Elsevier Science B.V. All rights reserved.