Exploiting Novel Calcium-Mediated Apoptotic Processes for the Treatment of Human Breast Cancers with Elevated Nqo1 Levels; Technical rept. 6 Feb 2004-5 Feb 2008

摘要

We demonstrate that the NQO1-dependent reduction of Beta-lap caused ROS generation, DNA breaks, and triggered calcium (Ca2+)- dependent Upsilon- H2AX formation and PARP-1 hyperactivation. PARP-1 hyperactivation was an integral part of cell death caused by this compound, causing NAD+ and ATP losses that suppressed DNA repair and caused cell death. PARP-1 inhibition or intracellular Ca2+ chelation protected cells from Beta-lap-induced cell death. Similarly, hydrogen peroxide (H2O2), but not N-Methly-N -nitro-N- nitrosoguanidine (MNNG), caused Ca2+-mediated PARP-1 hyperactivation and death. Thus, Ca2+-mediated PARP-1 hyperactivation and death. Thus, Ca2+ appears to be an important co-factor in PARP-1 hyperactivation after ROS-induced DNA damage. To further explore DNA repair as a resistance factor(s) that might impede cell death, we explored the contribution of DNA double-strand break (DSB) repair following Beta-lap exposure. Beta-Lap treatment resulted in the NQO1-dependent activation of the MRE11-Rad50-Nbs-1 (MRN) complex, as well as ATM Serine 1981, DNA-PKcs Theronine 2609, and Chk1 Serine 345 phosphorylation, indicative of ATR activation. These data suggested the simultaneous activation of both homologous recombination (HR) and non-homologous end joining (NHEJ) pathways. However, inhibition of NHEJ potentiated Beta-lap lethality.