3-AMINOBENZAMIDE DELAYS REJOINING OF DNA STRAND BREAKS IN GAMMA-IRRADIATED LYMPHOCYTES FROM PATIENTS WITH BREAST-CANCER AND NOT CERVICAL-CANCER

An inhibitor of poly(ADP-ribose) polymerase is 3-aminobenzamide (3AB), treatment by which normally results in the decreased levels of rejoin ing of DNA single strand breaks. We have studied the effect of 3AB in gamma-irradiation induced damage and the subsequent repair of DNA alon g with the corresponding changes in poly (ADP-ribose) polymerase activ ity in lymphocytes of patients with the cancer of breast and uterine c ervix. The presence or absence of 3AB prior to gamma-irradiation did n ot influence the extent of DNA damage. On the other hand, single stran d breaks rejoining in breast cancer cases was found to be slower as co mpared to that of cervical cancer cases and normal individuals. The re lative ADP-ribosylation in the presence of 3AB was much lower in the b reast cancer cases as compared to normal but there was no significant change in the cervical cancer cases. Overall the maximum relative ADP- ribosylation was slower in the presence of 3AB. This suggests that the lower activity of poly (ADP-ribose) polymerase in breast cancer cases might delay the first phase of single strand breaks (SSBs) rejoinnig.