ABNORMAL DNA-SYNTHESIS ACTIVITY-INDUCED BY X-RAYS IN NEVOID BASAL-CELL CARCINOMA SYNDROME CELLS

DNA synthesis activity was examined in fibroblasts and isolated nuclei derived from patients with nevoid basal cell carcinoma syndrome (NBCC S) upon exposure to X-ray and ultraviolet (UV). The DNA synthesis acti vity in NBCCS fibroblasts increased after X-ray irradiation, i.e., to twice that on mock-irradiation, while it decreased in healthy donor-de rived fibroblasts. The DNA synthesis activity in isolated nuclei of X- ray irradiated NBCCS fibroblasts also increased, i.e., more than twice that on mock-irradiated. In the experiments using synchronized cells, DNA synthesis activity showed the most marked increase when the fibro blasts at S phase were irradiated with X-rays. In contrast, UV-irradia ted NBCCS fibroblasts showed no such increase in DNA synthesis. These results revealed that DNA synthesis is abnormally induced in X-ray irr adiated NBCCS cells and that this abnormality might be related with th e tendency of tumorigenesis in NBCCS patients after exposure to X-ray. (C) 1997 Academic Press.