title: [Role of let-7 in maintaining characteristics of breast cancer stem cells].
abstract: OBJECTIVE
  To observe the expression of let-7 in breast cancer stem cells and explore the role of let-7 in maintaining the characteristics of breast cancer stem cells.
  
  
  METHODS
  We separated breast cancer stem cells (SP and NSP) from MCF-7 cell line using SP sorting, and observed the expression of let-7a/b/c on SP and NSP cells using quantitative real-time PCR and the expressions of Ras and ERK using Western blotting to study the mechanism by which let-7 maintains the characteristics of breast cancer stem cells.
  
  
  RESULTS
  The SP cells accounted for 3.3% in MCF-7 cells, however, the rate dropped to 0.4% when verapamil was added into the process of seperation. The level of Let-7a/b/c in SP cells were lower than that in NSP cells, and among let-7 miRNAs, let-7b/c showed the most obvious difference. The expressions of t-Ras and t-ERK showed no difference between SP and NSP cells, nevertheless, the expressions of p-Ras, p-ERK were higher in SP cells than in NSP cells.
  
  
  CONCLUSIONS
  SP sorting is an effective method to separate cancer stem cells. There do exist cancer stem cells in MCF-7 breast cancer cell line. Let-7 is down-regulated in SP cells, and the down-regulation makes let-7 lose the opportunity to restrain Ras mRNA, finally, p-Ras and p-ERK are activated. They play an important role in maintaining the characteristics of breast cancer stem cells.
authors.affiliation: Department of Surgical Oncology, FiXi'an Jiaotong University, Xi'an, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Sun
authors.forename: Chong
authors.initials: C
authors.lastname: Fan
authors.forename: Li-juan
authors.initials: LJ
authors.lastname: Hu
authors.forename: Ning
authors.initials: N
authors.lastname: Du
authors.forename: Chong-wen
authors.initials: CW
authors.lastname: Xu
authors.forename: Hong
authors.initials: H
authors.lastname: Ren
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D061986:MCF-7 Cells; D035683:MicroRNAs / Q000235:genetics*; D014411:Neoplastic Stem Cells / Q000378:metabolism*; D015689:Oncogene Protein p21(ras) / Q000378:metabolism; D058985:Side-Population Cells / Q000378:metabolism
chemical_list: D035683:MicroRNAs; C487931:mirnlet7 microRNA, human; D048049:Extracellular Signal-Regulated MAP Kinases; D015689:Oncogene Protein p21(ras)