title: Endogenous endothelial cell nitric-oxide synthase modulates apoptosis in cultured breast cancer cells and is transcriptionally regulated by p53.
abstract: Nitric oxide can both stimulate and suppress apoptosis. By reverse transcriptase-polymerase chain reaction and sequencing we show that human breast cancer (MCF-7) cells express endothelial cell nitric-oxide synthase (ecNOS), but not other nitric-oxide synthase isoforms. Inhibition of ecNOS activity in MCF-7 cells increased tumor cell apoptosis, and this effect was also seen following treatment with an NO scavenger. In addition, low concentrations of the NO donor sodium nitroprusside inhibited, whereas high concentrations stimulated MCF-7 cell apoptosis. The ecNOS promoter was found to contain a specific binding site for the apoptosis-regulating protein p53. In co-transfection studies wild-type, but not mutant, p53 down-regulated transcription of an ecNOS promoter-luciferase reporter gene construct. In addition, NO donors up-regulated p53 protein levels in MCF-7 cells. These data point to a previously unrecognized p53-dependent regulation of ecNOS expression that may be important both for regulating apoptosis and for avoiding the generation of genotoxic quantities of NO.
authors.affiliation: Division of Cell Biology, Department of Anatomy, The Royal Veterinary and Agricultural University, DK-1870 Frederiksberg, DK-2950 Denmark.
authors.forename: K
authors.initials: K
authors.lastname: Mortensen
authors.forename: J
authors.initials: J
authors.lastname: Skouv
authors.forename: D M
authors.initials: DM
authors.lastname: Hougaard
authors.forename: L I
authors.initials: LI
authors.lastname: Larsson
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D001483:Base Sequence; D001943:Breast Neoplasms / Q000473:pathology*; D004247:DNA; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000502:physiology*; D052250:Nitric Oxide Synthase Type III; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic / Q000502:physiology*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
chemical_list: D016159:Tumor Suppressor Protein p53; D004247:DNA; C496314:NOS3 protein, human; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III