title: Modulation of redox signaling promotes apoptosis in epithelial ovarian cancer cells.
abstract: OBJECTIVE
  Epithelial ovarian cancer (EOC) cells are known to be resistant to apoptosis through a mechanism that may involve alteration in their redox balance. NADPH oxidase is a major source of intracellular superoxide, which is converted to the less toxic product by superoxide dismutase (SOD). Superoxide contributes to hypoxia inducible factor (HIF)-1α stabilization. We sought to determine the effects of inhibiting the generation of intracellular reactive oxygen species (ROS) on apoptosis of EOC cells.
  
  
  METHODS
  Diphenyleneiodonium (DPI), an irreversible ROS inhibitor, was used to inhibit the generation of ROS in EOC cell lines, SKOV-3 and MDAH-2774, followed by assessment of apoptosis, NADPH oxidase, SOD3 and HIF-1α expression. A combination of immunohistochemistry, immunoprecipitation/western blot, and real-time RT-PCR were utilized to evaluate the expression of these enzymes in EOC cells as well as normal ovarian tissue and ovarian cancer tissue specimens.
  
  
  RESULTS
  DPI treatment significantly induced apoptosis in both EOC cell lines as evident by increased caspase-3 activity and TUNEL assay. Additionally, both EOC cell lines were found to express NADPH oxidase, HIF-1α, and SOD3, which were highly sensitive to DPI treatment. DPI treatment resulted in reduced NADPH oxidase, SOD3 and HIF-1α levels. Furthermore, ovarian cancer tissues were found to manifest higher NADPH oxidase levels as compared to normal ovarian tissues.
  
  
  CONCLUSIONS
  These data suggest that lowering oxidative stress, possibly through the inhibition of NADPH oxidase, induces apoptosis in ovarian cancer cells and may serve as a potential target for cancer therapy.
authors.affiliation: Department of Obstetrics and Gynecology, The C.S. Mott Center for Human Growth and Development, Wayne State University School of Medicine, Detroit, MI 48201, USA.
authors.forename: Zhongliang
authors.initials: Z
authors.lastname: Jiang
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Fletcher
authors.forename: Rouba
authors.initials: R
authors.lastname: Ali-Fehmi
authors.forename: Michael P
authors.initials: MP
authors.lastname: Diamond
authors.forename: Husam M
authors.initials: HM
authors.lastname: Abu-Soud
authors.forename: Adnan R
authors.initials: AR
authors.lastname: Munkarah
authors.forename: Ghassan M
authors.initials: GM
authors.lastname: Saed
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D000077216:Carcinoma, Ovarian Epithelial; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000032:analysis; D019255:NADPH Oxidases / Q000032:analysis / Q000235:genetics; D009375:Neoplasms, Glandular and Epithelial / Q000378:metabolism / Q000473:pathology*; D009861:Onium Compounds / Q000494:pharmacology; D010051:Ovarian Neoplasms / Q000378:metabolism / Q000473:pathology*; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013482:Superoxide Dismutase / Q000235:genetics
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009861:Onium Compounds; D017382:Reactive Oxygen Species; C007517:diphenyleneiodonium; C441642:SOD3 protein, human; D013482:Superoxide Dismutase; D019255:NADPH Oxidases; D053148:Caspase 3