title: An induction of microRNA, miR-7 through estrogen treatment in breast carcinoma.
abstract: BACKGROUND
  Estrogen plays an important role in the development of estrogen-dependent breast carcinoma. Recently, several studies demonstrated a possible involvement of several micro RNAs (miRNAs) in the development of resistance to endocrine therapy in breast cancer patients, but the correlation between estrogen actions and miRNA expression in breast carcinoma still remains largely unknown. Therefore, in this study, we examined the in vitro effects of estrogen upon miRNA expression profiles in breast carcinoma.
  
  
  METHODS
  We first screened the miRNA expression profiles induced by 17β-Estradiol (E2) using RT2 miRNA PCR Array in the ER-positive breast carcinoma cell line MCF-7. We identified miR-7 as the important miRNA associated with estrogen actions in these cells and further examined the changes of estrogen-dependent EGFR expression by miR-7 in ER-positive or -negative breast carcinoma cell lines including MCF-7. We also evaluated the correlation between miR-7 and EGFR expression in breast carcinoma cells derived from 21 patients using laser capture microdissection combined with quantitative reverse transcriptase-PCR.
  
  
  RESULTS
  Seventeen miRNAs were significantly induced by E2 treatment in the MCF-7 cell line. Among 17 miRNAs induced by estradiol treatment, only miR-7 expression was significantly decreased by subsequent ICI treatment. The expression of miR-7 was up-regulated 2.94-fold by E2 treatment. miR-7 was reported to suppress epidermal growth factor receptor (EGFR) expression in several human malignancies. Transfection of miR-7 significantly suppressed EGFR mRNA levels in MCF-7 cells. Depletion of E2 from cell culture media also increased the expression level of EGFR mRNA in MCF-7 and T-47D cells but not in ER-negative, MDA-MB-231 and SK-BR-3 cells. We also evaluated the status of miR-7 in breast carcinoma tissues, but the correlation between the status of miR-7 and EGFR in carcinoma cells isolated by laser capture microscopy was not detected.
  
  
  CONCLUSIONS
  These results suggest that miR-7 may play a role in the development of resistance to endocrine therapy in breast cancer patients through regulating EGFR expression of carcinoma cells.
authors.affiliation: Department of Pathology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Masuda
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Miki
authors.forename: Shuko
authors.initials: S
authors.lastname: Hata
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Takagi
authors.forename: Minako
authors.initials: M
authors.lastname: Sakurai
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Ono
authors.forename: Koyu
authors.initials: K
authors.lastname: Suzuki
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.forename: Eriko
authors.initials: E
authors.lastname: Abe
authors.forename: Hisashi
authors.initials: H
authors.lastname: Hirakawa
authors.forename: Takanori
authors.initials: T
authors.lastname: Ishida
authors.forename: Takashi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Noriaki
authors.initials: N
authors.lastname: Ohuchi
authors.forename: Hironobu
authors.initials: H
authors.lastname: Sasano
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology / Q000627:therapeutic use; D004967:Estrogens / Q000494:pharmacology* / Q000627:therapeutic use*; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D061986:MCF-7 Cells; D035683:MicroRNAs / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged
chemical_list: D066246:ErbB Receptors; D004958:Estradiol; D004967:Estrogens; D035683:MicroRNAs; C549242:MIRN7-1 microRNA, human; C512478:EGFR protein, human