title: MicroRNA-221/222 negatively regulates estrogen receptor alpha and is associated with tamoxifen resistance in breast cancer.
abstract: A search for regulators of estrogen receptor alpha (ERalpha) expression has yielded a set of microRNAs (miRNAs) for which expression is specifically elevated in ERalpha-negative breast cancer. Here we show distinct expression of a panel of miRNAs between ERalpha-positive and ERalpha-negative breast cancer cell lines and primary tumors. Of the elevated miRNAs in ERalpha-negative cells, miR-221 and miR-222 directly interact with the 3'-untranslated region of ERalpha. Ectopic expression of miR-221 and miR-222 in MCF-7 and T47D cells resulted in a decrease in expression of ERalpha protein but not mRNA, whereas knockdown of miR-221 and miR-222 partially restored ERalpha in ERalpha protein-negative/mRNA-positive cells. Notably, miR-221- and/or miR-222-transfected MCF-7 and T47D cells became resistant to tamoxifen compared with vector-treated cells. Furthermore, knockdown of miR-221 and/or miR-222 sensitized MDA-MB-468 cells to tamoxifen-induced cell growth arrest and apoptosis. These findings indicate that miR-221 and miR-222 play a significant role in the regulation of ERalpha expression at the protein level and could be potential targets for restoring ERalpha expression and responding to antiestrogen therapy in a subset of breast cancers.
authors.affiliation: H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, USA.
authors.forename: Jian-Jun
authors.initials: JJ
authors.lastname: Zhao
authors.forename: Jianhong
authors.initials: J
authors.lastname: Lin
authors.forename: Hua
authors.initials: H
authors.lastname: Yang
authors.forename: William
authors.initials: W
authors.lastname: Kong
authors.forename: Lili
authors.initials: L
authors.lastname: He
authors.forename: Xu
authors.initials: X
authors.lastname: Ma
authors.forename: Domenico
authors.initials: D
authors.lastname: Coppola
authors.forename: Jin Q
authors.initials: JQ
authors.lastname: Cheng
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics / Q000378:metabolism; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D047628:Estrogen Receptor alpha / Q000096:biosynthesis* / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism*; D013629:Tamoxifen / Q000494:pharmacology
chemical_list: D020413:3' Untranslated Regions; D018931:Antineoplastic Agents, Hormonal; D047628:Estrogen Receptor alpha; D035683:MicroRNAs; D009363:Neoplasm Proteins; D012334:RNA, Neoplasm; D013629:Tamoxifen; C525709:MIR221, human; C525710:MIR222, human
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