title: Estradiol downregulates miR-21 expression and increases miR-21 target gene expression in MCF-7 breast cancer cells.
abstract: Select changes in microRNA (miRNA) expression correlate with estrogen receptor alpha (ER alpha) expression in breast tumors. miR-21 is higher in ER alpha positive than negative tumors, but no one has examined how estradiol (E(2)) regulates miR-21 in breast cancer cells. Here we report that E(2) inhibits miR-21 expression in MCF-7 human breast cancer cells. The E(2)-induced reduction in miR-21 was inhibited by 4-hydroxytamoxifen (4-OHT), ICI 182 780 (Faslodex), and siRNA ER alpha indicating that the suppression is ER alpha-mediated. ER alpha and ER beta agonists PPT and DPN inhibited and 4-OHT increased miR-21 expression. E(2) increased luciferase activity from reporters containing the miR-21 recognition elements from the 3'-UTRs of miR-21 target genes, corroborating that E(2) represses miR-21 expression resulting in a loss of target gene suppression. The E(2)-mediated decrease in miR-21 correlated with increased protein expression of endogenous miR-21-targets Pdcd4, PTEN and Bcl-2. siRNA knockdown of ER alpha blocked the E(2)-induced increase in Pdcd4, PTEN and Bcl-2. Transfection of MCF-7 cells with antisense (AS) to miR-21 mimicked the E(2)-induced increase in Pdcd4, PTEN and Bcl-2. These results are the first to demonstrate that E(2) represses the expression of an oncogenic miRNA, miR-21, by activating estrogen receptor in MCF-7 cells.
authors.affiliation: Department of Biochemistry & Molecular Biology, Center for Genetics and Molecular Medicine, University of Louisville School of Medicine, Louisville, KY 40292, USA.
authors.forename: Nalinie S
authors.initials: NS
authors.lastname: Wickramasinghe
authors.forename: Tissa T
authors.initials: TT
authors.lastname: Manavalan
authors.forename: Susan M
authors.initials: SM
authors.lastname: Dougherty
authors.forename: Krista A
authors.initials: KA
authors.lastname: Riggs
authors.forename: Yong
authors.initials: Y
authors.lastname: Li
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Klinge
mesh_terms: D020413:3' Untranslated Regions / Q000737:chemistry; D051017:Apoptosis Regulatory Proteins / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D015536:Down-Regulation; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000819:agonists / Q000037:antagonists & inhibitors / Q000235:genetics; D047629:Estrogen Receptor beta / Q000819:agonists / Q000037:antagonists & inhibitors / Q000235:genetics; D005260:Female; D000077267:Fulvestrant; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D006801:Humans; D035683:MicroRNAs / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D016372:RNA, Antisense / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology; D020703:ras GTPase-Activating Proteins / Q000235:genetics
chemical_list: D020413:3' Untranslated Regions; D051017:Apoptosis Regulatory Proteins; D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; D019384:Nucleic Acid Synthesis Inhibitors; C114487:PDCD4 protein, human; D011500:Protein Synthesis Inhibitors; D016372:RNA, Antisense; D016601:RNA-Binding Proteins; D020703:ras GTPase-Activating Proteins; D013629:Tamoxifen; C016601:afimoxifene; D003609:Dactinomycin; D000077267:Fulvestrant; D004958:Estradiol; D003513:Cycloheximide