SEASONAL-VARIATION OF DNA-DAMAGE AND REPAIR IN PATIENTS WITH NONMELANOMA SKIN-CANCER AND REFERENTS WITH AND WITHOUT PSORIASIS

Quadruples of skin cancer patients with and without psoriasis and refe rents with and without psoriasis (4 x 20 study persons) were identifie d and examined for DNA damage by single cell gel electrophoresis (come t-assay) and DNA-repair by UV-induced unscheduled DNA synthesis (UDS) in mononuclear blood cells (lymphocytes and monocytes). DNA damage (st rand breaks and alkaline labile sites) as assessed by the comet assay and DNA repair as assessed by UDS were significantly associated with t he season in which blood sampling took place. This variation might be explained by an increased exposure to solar radiation. When the comet tail moment data were stratified by sampling period, an interaction be tween psoriasis and skin cancer was detected, with patients with psori asis and skin cancer exhibiting more DNA damage. Patients with psorias is and skin cancer also had lower UDS compared to healthy study person s, suggesting that the more DNA damage may be caused by a lower rate o f DNA repair. In all study persons, the extent of UDS correlated posit ively with the amount of DNA damage determined by the comet assay. (C) 1998 Elsevier Science B.V.