NCX4040, the non-steroidal anti-inflammatory-NO donor, is cytotoxic to several human
tumors, including ovarian
tumor cells. We have found that
NCX4040 is also cytotoxic against both OVCAR-8 and its
adriamycin resistant (NCI/ADR-RES) tumor cell lines. Here, we have examined mechanism(s) for the cytotoxicity of
NCX4040 in OVCAR-8 and NCI/ADR-RES cell lines. We found that
NCX4040 induced significant apoptosis in both cell lines. Furthermore,
NCX4040 treatment caused significant depletion of cellular
glutathione, causing oxidative stress due to the formation of reactive
oxygen/
nitrogen species (ROS/RNS). Significantly more ROS/RNS were detected in OVCAR-8 cells than in NCI/ADR-RES cells which may have resulted from increased activities of SOD,
glutathione peroxidase and
transferases expressed in NCI/ADR-RES cells.
NCX4040 treatment resulted in the formation of double-strand DNA breaks in both cells; however, more of these DNA breaks were detected in OVCAR-8 cells. RT-PCR studies indicated that NCX4040-induced DNA damage was not repaired as efficiently in NCI/ADR-RES cells as in OVCAR-8 cells which may lead to a differential cell death. Pretreatment of OVCAR-8 cells with
N-acetylcysteine (NAC) significantly decreased cytotoxicity of
NCX4040 in OVCAR-8 cells; however, NAC had no effects on
NCX4040 cytotoxicity in NCI/ADR-RES cells. In contrast, FeTPPS, a
peroxynitrite scavenger, completely blocked NCX4040-induced cell death in both cells, suggesting that NCX4040-induced cell death could be mediated by
peroxynitrite formed from
NCX4040 following cellular metabolism.