title: miR-211 suppresses epithelial ovarian cancer proliferation and cell-cycle progression by targeting Cyclin D1 and CDK6.
abstract: BACKGROUND
  Epithelial ovarian cancer (EOC) is a significant cause of morbidity and mortality. MicroRNAs play important roles in cancer development and progression. The microRNA miR-211 is localized on intron 6 of the Trpm1 gene at 15q13-q14, a locus that is frequently lost in neoplasms. Its function and loss-of-function have been described in normal and cancer cells and tissues. miR-211 is known to be dysregulated in ovarian cancer: however, its function and the downstream effect of its loss-of-function in ovarian cancer have not been described before.
  
  
  METHODS
  We analyzed miR-211 expression in clinical samples of primary EOC tissues compared to normal epithelial ovarian tissues and in the EOC cell lines: OVCAR3, Caov3, OVCA429, SKOV3 and A2780 compared to human ovarian surface epithelial cells. We then investigated the effect of miR-211 on EOC cell proliferation and apoptosis by counting cell numbers, MTT, colony formation, cell cycle, and PI/Annexin V staining assays. A luciferase reporter system was developed to assess miR-211 regulation of the predicted targets. Expression level of discovered targets and correlation with miR-211 expression were analyzed in EOC tissues. Finally, OVCAR3 stably expressing miR-211 or control cells were injected subcutaneously into mice to determine in vivo effect of miR-211 on tumorigenesis.
  
  
  RESULTS
  We found that the expression of miR-211 is downregulated in EOC tissues and cell lines compared to normal epithelial ovarian tissue and human ovarian surface epithelial cells, respectively. miR-211 was found to arrest cells in the G0/G1-phase, inhibit proliferation and induce apoptosis. Cyclin D1 and CDK6 were found to be direct targets of miR-211, and when overexpressed in miR-211-expressing EOC cells, could restore proliferative ability. Finally, in vitro investigation confirmed that miR-211 is a tumor suppressor that controls Cyclin D1 and CDK6 expression.
  
  
  CONCLUSIONS
  Our results demonstrate that miR-211 is a tumor suppressor that controls expression of Cyclin D1 and CDK6, and that its downregulation results in overexpression of Cyclin D1 and CDK6 which increases proliferation ability of EOC cells to proliferate compared to normal cells.
authors.affiliation: Department of Gynecology, the Affiliated Tumor Hospital, Harbin Medical University, 150 Haping Rd, Nangang, Harbin, 150020, Heilongjiang, China. xiabairong9999@126.com.
authors.forename: Bairong
authors.initials: B
authors.lastname: Xia
authors.affiliation: Department of Gynecology, the Affiliated Tumor Hospital, Harbin Medical University, 150 Haping Rd, Nangang, Harbin, 150020, Heilongjiang, China. dr_yss@126.com.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Yang
authors.affiliation: Department of Gynecology, the Affiliated Tumor Hospital, Harbin Medical University, 150 Haping Rd, Nangang, Harbin, 150020, Heilongjiang, China. skyliu_1030@hotmail.com.
authors.forename: Tianbo
authors.initials: T
authors.lastname: Liu
authors.affiliation: Department of Gynecology, the Affiliated Tumor Hospital, Harbin Medical University, 150 Haping Rd, Nangang, Harbin, 150020, Heilongjiang, China. lougehyd@163.com.
authors.forename: Ge
authors.initials: G
authors.lastname: Lou
mesh_terms: D017209:Apoptosis / Q000235:genetics; D000077216:Carcinoma, Ovarian Epithelial; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000235:genetics; D019938:Cyclin D1 / Q000235:genetics*; D051361:Cyclin-Dependent Kinase 6 / Q000235:genetics*; D015536:Down-Regulation / Q000235:genetics; D005260:Female; D059585:G1 Phase Cell Cycle Checkpoints / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D016147:Genes, Tumor Suppressor / Q000502:physiology*; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D008875:Middle Aged; D009375:Neoplasms, Glandular and Epithelial / Q000235:genetics* / Q000473:pathology; D010051:Ovarian Neoplasms / Q000235:genetics* / Q000473:pathology; D016192:Resting Phase, Cell Cycle / Q000235:genetics*
chemical_list: C530104:CCND1 protein, human; C549405:MIRN211 microRNA, human; D035683:MicroRNAs; D019938:Cyclin D1; C495911:CDK6 protein, human; D051361:Cyclin-Dependent Kinase 6