title: Cisplatin alters nitric oxide synthase levels in human ovarian cancer cells: involvement in p53 regulation and cisplatin resistance.
abstract: The present study determines if (1) basal protein levels of nitric oxide (NO) synthases (eNOS, iNOS, and nNOS) are different in cisplatin-sensitive (OV2008) and counterpart cisplatin-resistant (C13(*)) human ovarian cancer cells, (2) cisplatin alters NOS levels, (3) NO donor causes apoptosis and p53 upregulation, (4) NO donor sensitizes C13(*) cells to cisplatin via p53 upregulation (determined by p53 siRNA gene-knockdown), and (5) inhibition of endogenous NOS alters cisplatin-induced apoptosis. Basal iNOS levels were higher in OV2008 cells than in C13(*) cells. Cisplatin upregulated iNOS, but dramatically reduced eNOS and nNOS, in OV2008 cells only. Failure of cisplatin to upregulate iNOS and downregulate eNOS/nNOS in cisplatin-resistant C13(*) cells may be an aetiological factor in the development of resistance. The NO donor S-nitroso-N-acetylpenicillamine (SNAP) increased p53 protein levels and induced apoptosis in both cell types, and enhanced cisplatin-induced apoptosis in C13(*) cells in a p53-dependent manner (i.e., enhancement blocked by p53 siRNA). Specific iNOS inhibitor 1400W partially blocked cisplatin-induced apoptosis in OV2008 cells. In cisplatin-resistant C13(*) cells, blocking all NOSs with N(G)-amino-L-arginine dramatically changed these cells from cisplatin-resistant to cisplatin-sensitive, greatly potentiating cisplatin-induced apoptosis. The data suggest important roles for the three NOSs in regulating chemoresistance to cisplatin in ovarian cancer cells.
authors.affiliation: Reproductive Biology Unit, Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: E L
authors.initials: EL
authors.lastname: Leung
authors.forename: M
authors.initials: M
authors.lastname: Fraser
authors.forename: R R
authors.initials: RR
authors.lastname: Fiscus
authors.forename: B K
authors.initials: BK
authors.lastname: Tsang
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D005260:Female; D006801:Humans; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000502:physiology; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D034741:RNA, Small Interfering / Q000494:pharmacology; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
chemical_list: D000970:Antineoplastic Agents; D020030:Nitric Oxide Donors; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D026423:S-Nitroso-N-Acetylpenicillamine; D019001:Nitric Oxide Synthase; D002945:Cisplatin