DNA-repair synthesis in blast cells from patients with acute myeloblastic leukaemia

DNA-repair synthesis was studied in blast cells from patients with acute myeloblastic leukaemia. The DNA-repair synthesis, measured as 3H-thymidine incorporation, was registered as unscheduled DNA synthesis by autoradiography, and also after suppression of the replicative DNA synthesis by hydroxyurea by liquid scintillation. There was good correlation when results from both methods were compared. A significantly wider variation of unscheduled DNA synthesis was found in leukaemic as compared to normal blast cell populations. There was also a wider variation within individual leukaemic blast cell samples compared to normal samples. A correlation was found between unscheduled DNA synthesis induced by nitrogen mustard and by UV-irradiation in the leukaemic blast cell populations. The UV-induced unscheduled DNA synthesis in some of the leukaemic blast cell populations continued to increase at doses of UV-irradiation at which normal myeloblasts had reached their maximum level of unscheduled DNA synthesis. This indicates that at least some malignant blast cell populations may possess an effective DNA-repair system.