title: [Interaction between miR-21 and DNA methylation in different breast cancer cells].
abstract: OBJECTIVE
  To determine the interaction between miR-21 and DNA methylation in different breast cancer cells.
  
  
  METHODS
  Fluorescence tagged miR-21 inhibitor and its negative control (NC) were transient transfected into MCF-7 and MDA-MB-231 cell, the transfection efficiency was observed using fluorescence microscopy, and the miR-21 expression level and genome DNA methylation status before and after transfection were assessed by real-time PCR and bisulfite-qMSP respectively. To investigate the regulation effect of DNA methylation on miR-21, cells were treated with 5-AZA (2.5 µmol/L) for 72 h, with dimethyl sulfoxide (DMSO) treatment as its negative control (NC), and the expression level of phosphatase and tensin homolog deleted on chromosome ten (PTEN) and AKT(also known as Protein Kinase B), two downstream genes of miR-21 were detected by Western blot.
  
  
  RESULTS
  The expression of miR-21 in MCF-7 cell was significantly knocked down (P < 0.01) by miR-21 inhibitor, with the genome DNA methylation level (P < 0.05) and all the three Dnmts: Dnmt1, Dnmt3a, and Dnmt3b unregulated. In contrast, the miR-21 expression in MDA-MB-231 cell was elevated ( P < 0.01) by miR-21 inhibitor, meanwhile, down- regulated of genome DNA methylation (P < 0.05) and Dnmt3b expression, upregulation of Dnmt3a were also observed. In addition, treated with 5-AZA resulted in significant increases of miR-21 expression in both MCF-7 and MDA-MB-231 cells (P < 0.01), with the protein level of PTEN increased in MCF-7 cell, which was further involved in the downregulation of AKT.
  
  
  CONCLUSIONS
  The regulation effects of DNA methylation by transient transfection of miR-21 in MCF-7 and MDA-MB-231 cells are almost opposite, whilst the expression of miR-21 in two cell lines were all upregulated by decreased DNA methylation level and our results may provide some experimental evidences for the future development of rational therapy for different breast cancer.
authors.forename: Ying-yi
authors.initials: YY
authors.lastname: Zhang
authors.forename: Wei-ping
authors.initials: WP
authors.lastname: Tian
authors.forename: Mei
authors.initials: M
authors.lastname: Mei
mesh_terms: D001374:Azacitidine; D001943:Breast Neoplasms / Q000235:genetics*; D045744:Cell Line, Tumor; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism; D019175:DNA Methylation; D000090205:DNA Methyltransferase 3A; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D061986:MCF-7 Cells; D035683:MicroRNAs / Q000235:genetics*; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D011401:Promoter Regions, Genetic; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D015854:Up-Regulation; D000097584:DNA Methyltransferase 3B
chemical_list: D001374:Azacitidine; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D035683:MicroRNAs; D051059:PTEN Phosphohydrolase; D051057:Proto-Oncogene Proteins c-akt; D000097584:DNA Methyltransferase 3B; C000717967:DNMT3A protein, human; C524940:MIRN21 microRNA, human; C000619380:DNMT1 protein, human; C494929:PTEN protein, human