title: Nitric oxide in physiologic concentrations targets the translational machinery to increase the proliferation of human breast cancer cells: involvement of mammalian target of rapamycin/eIF4E pathway.
abstract: Nitric oxide (NO) in nanomolar (nmol/L) concentrations is consistently detected in tumor microenvironment and has been found to promote tumorigenesis. The mechanism by which NO enhances tumor progression is largely unknown. In this study, we investigated the possible mechanisms and identified cellular targets by which NO increases proliferation of human breast cancer cell lines MDA-MB-231 and MCF-7. DETA-NONOate, a long acting NO donor, with a half-life of 20 h, was used. We found that NO (nmol/L) dramatically increased total protein synthesis in MDA-MB-231 and MCF-7 and also increased cell proliferation. NO specifically increased the translation of cyclin D1 and ornithine decarboxylase (ODC) without altering their mRNA levels or half-lives. Critical components in the translational machinery, such as phosphorylated mammalian target of rapamycin (mTOR) and its downstream targets, phosphorylated eukaryotic translation initiation factor and p70 S6 kinase, were up-regulated following NO treatment, and inhibition of mTOR with rapamycin attenuated NO induced increase of cyclin D1 and ODC. Activation of translational machinery was mediated by NO-induced up-regulation of the Raf/mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase/ERK (Raf/MEK/ERK) and phosphatidylinositol 3-kinase (PI-3 kinase)/Akt signaling pathways. Up-regulation of the Raf/MEK/ERK and PI-3 kinase/Akt pathways by NO was found to be mediated by activation of Ras, which was cyclic guanosine 3',5'-monophosphate independent. Furthermore, inactivation of Ras by farnesyl transferase inhibitor or K-Ras small interfering RNA attenuated NO-induced increase in proliferation signaling and cyclin D1 and ODC translation, further confirming the involvement of Ras activation during NO-induced cell proliferation.
authors.affiliation: Departments of Obstetrics and Gynecology and Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, University of California-Los Angeles, 10833 Le Conte Avenue, Los Angeles, CA, USA.
authors.forename: Shehla
authors.initials: S
authors.lastname: Pervin
authors.forename: Rajan
authors.initials: R
authors.lastname: Singh
authors.forename: Estebes
authors.initials: E
authors.lastname: Hernandez
authors.forename: Guoyao
authors.initials: G
authors.lastname: Wu
authors.forename: Gautam
authors.initials: G
authors.lastname: Chaudhuri
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000037:antagonists & inhibitors; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D048708:Cell Growth Processes / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D006152:Cyclic GMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism*; D006801:Humans; D020935:MAP Kinase Signaling System; D009569:Nitric Oxide / Q000494:pharmacology*; D009603:Nitroso Compounds / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D014176:Protein Biosynthesis; D011494:Protein Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases; D048490:raf Kinases / Q000378:metabolism
chemical_list: D019883:Alkyl and Aryl Transferases; D006152:Cyclic GMP; D039561:Eukaryotic Initiation Factor-4E; D009569:Nitric Oxide; D009603:Nitroso Compounds; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D048490:raf Kinases; C094210:2,2'-(hydroxynitrosohydrazono)bis-ethanamine; C064911:p21(ras) farnesyl-protein transferase; C546842:MTOR protein, human