Chronic lymphocytic leukemia lymphocytes lack the capacity to repair UVC-induced lesions

Cells from chronic lymphocytic leukemia (CLL) patients and from healthy ind ividuals were irradiated with UVC and incubated for varying periods of time . The number of single strand breaks and alkali-labile sites was determined by comet analysis. Unirradiated CLL and healthy cells exhibited no signifi cant numbers of single strand breaks. The extent of DNA damage was found to increase with dose for both healthy and CLL cells. However, the CLL cells had much more extensive DNA fragmentation than healthy cells at each dose. Deoxyribonucleoside supplemented medium inhibited comet formation in both c ell types. Thymidine alone produced the same effect. In healthy cells, repa ir of lesions was complete after 4 h of incubation as indicated by the abse nce of comet formation. The CLL cells exhibited no significant repair even after 48 h, CLL lymphocytes are killed by very low doses of UVC radiation. The results reported here suggest that this hypersensitivity results from t he inability of CLL cells to repair WC-induced DNA damage and a contributin g factor is the low amounts of intracellular deoxyribonucleosides. (C) 2000 Elsevier Science B.V. All rights reserved.