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 rejoining of DNA single strand breaks. We have studied the effect of 3AB in gamma-irradiation induced damage and the subsequent repair of DNA along with the corresponding changes in poly (ADP-ribose) polymerase activity in lymphocytes of patients with the cancer of breast and uterine cervix. The presence or absence of 3AB prior to gamma-irradiation did not influence the extent of DNA damage. On the other hand, single strand breaks rejoining in breast cancer cases was found to be slower as compared to that of cervical cancer cases and normal individuals. The relative ADP-ribosylation in the presence of 3AB was much lower in the breast 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) rejoining.