title: Expression of miR-21 and its targets (PTEN, PDCD4, TM1) in flat epithelial atypia of the breast in relation to ductal carcinoma in situ and invasive carcinoma.
abstract: BACKGROUND
  Flat epithelial atypia (FEA) of the breast is characterised by a few layers of mildly atypical luminal epithelial cells. Genetic changes found in ductal carcinoma in situ (DCIS) and invasive ductal breast cancer (IDC) are also found in FEA, albeit at a lower concentration. So far, miRNA expression changes associated with invasive breast cancer, like miR-21, have not been studied in FEA.
  
  
  METHODS
  We performed miRNA in-situ hybridization (ISH) on 15 cases with simultaneous presence of normal breast tissue, FEA and/or DCIS and 17 additional cases with IDC. Expression of the miR-21 targets PDCD4, TM1 and PTEN was investigated by immunohistochemistry.
  
  
  RESULTS
  Two out of fifteen cases showed positive staining for miR-21 in normal breast ductal epithelium, seven out of fifteen cases were positive in the FEA component and nine out of twelve cases were positive in the DCIS component. A positive staining of miR-21 was observed in 15 of 17 IDC cases. In 12 cases all three components were present in one tissue block and an increase of miR-21 from normal breast to FEA and to DCIS was observed in five cases. In three cases the FEA component was negative, whereas the DCIS component was positive for miR-21. In three other cases, normal, FEA and DCIS components were negative for miR-21 and in the last case all three components were positive. Overall we observed a gradual increase in percentage of miR-21 positive cases from normal, to FEA, DCIS and IDC. Immunohistochemical staining for PTEN revealed no obvious changes in staining intensities in normal, FEA, DCIS and IDC. Cytoplasmic staining of PDCD4 increased from normal to IDC, whereas, the nuclear staining decreased. TM1 staining decreased from positive in normal breast to negative in most DCIS and IDC cases. In FEA, the staining pattern for TM1 was similar to normal breast tissue.
  
  
  CONCLUSIONS
  Upregulation of miR-21 from normal ductal epithelial cells of the breast to FEA, DCIS and IDC parallels morphologically defined carcinogenesis. No clear relation was observed between the staining pattern of miR-21 and its previously reported target genes.
authors.affiliation: Department of Pathology & Medical Biology, Groningen University Medical Centre and University of Groningen, Groningen, The Netherlands. l.qi@path.umcg.nl
authors.forename: Liqiang
authors.initials: L
authors.lastname: Qi
authors.forename: Joost
authors.initials: J
authors.lastname: Bart
authors.forename: Lu Ping
authors.initials: LP
authors.lastname: Tan
authors.forename: Inge
authors.initials: I
authors.lastname: Platteel
authors.forename: Tineke van der
authors.initials: Tv
authors.lastname: Sluis
authors.forename: Sippie
authors.initials: S
authors.lastname: Huitema
authors.forename: Geert
authors.initials: G
authors.lastname: Harms
authors.forename: Li
authors.initials: L
authors.lastname: Fu
authors.forename: Harry
authors.initials: H
authors.lastname: Hollema
authors.forename: Anke van den
authors.initials: Av
authors.lastname: Berg
mesh_terms: D051017:Apoptosis Regulatory Proteins / Q000235:genetics* / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D004848:Epithelium / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D006801:Humans; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D009361:Neoplasm Invasiveness; D051059:PTEN Phosphohydrolase / Q000235:genetics* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D014335:Tropomyosin / Q000235:genetics* / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; C114487:PDCD4 protein, human; D016601:RNA-Binding Proteins; C490775:TPM1 protein, human; D014335:Tropomyosin; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human