title: miR-200a regulates Nrf2 activation by targeting Keap1 mRNA in breast cancer cells.
abstract: NF-E2-related factor 2 (Nrf2) is an important transcription factor that activates the expression of cellular detoxifying enzymes. Nrf2 expression is largely regulated through the association of Nrf2 with Kelch-like ECH-associated protein 1 (Keap1), which results in cytoplasmic Nrf2 degradation. Conversely, little is known concerning the regulation of Keap1 expression. Until now, a regulatory role for microRNAs (miRs) in controlling Keap1 gene expression had not been characterized. By using miR array-based screening, we observed miR-200a silencing in breast cancer cells and demonstrated that upon re-expression, miR-200a targets the Keap1 3'-untranslated region (3'-UTR), leading to Keap1 mRNA degradation. Loss of this regulatory mechanism may contribute to the dysregulation of Nrf2 activity in breast cancer. Previously, we have identified epigenetic repression of miR-200a in breast cancer cells. Here, we find that treatment with epigenetic therapy, the histone deacetylase inhibitor suberoylanilide hydroxamic acid, restored miR-200a expression and reduced Keap1 levels. This reduction in Keap1 levels corresponded with Nrf2 nuclear translocation and activation of Nrf2-dependent NAD(P)H-quinone oxidoreductase 1 (NQO1) gene transcription. Moreover, we found that Nrf2 activation inhibited the anchorage-independent growth of breast cancer cells. Finally, our in vitro observations were confirmed in a model of carcinogen-induced mammary hyperplasia in vivo. In conclusion, our study demonstrates that miR-200a regulates the Keap1/Nrf2 pathway in mammary epithelium, and we find that epigenetic therapy can restore miR-200a regulation of Keap1 expression, therefore reactivating the Nrf2-dependent antioxidant pathway in breast cancer.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Eades
authors.forename: Muhua
authors.initials: M
authors.lastname: Yang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Yao
authors.forename: Yongshu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Qun
authors.initials: Q
authors.lastname: Zhou
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000235:genetics; D000975:Antioxidants / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D020868:Gene Silencing; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D000072019:Kelch-Like ECH-Associated Protein 1; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism*; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D020871:RNA Stability / Q000187:drug effects / Q000235:genetics; D015203:Reproducibility of Results; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D000077337:Vorinostat
chemical_list: D020413:3' Untranslated Regions; D000975:Antioxidants; D006877:Hydroxamic Acids; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; C533896:MIRN200 microRNA, human; D035683:MicroRNAs; D051267:NF-E2-Related Factor 2; D000077337:Vorinostat