title: Knockdown of miR-21 in human breast cancer cell lines inhibits proliferation, in vitro migration and in vivo tumor growth.
abstract: BACKGROUND
  MicroRNAs (miRNAs) are a class of small non-coding RNAs (20 to 24 nucleotides) that post-transcriptionally modulate gene expression. A key oncomir in carcinogenesis is miR-21, which is consistently up-regulated in a wide range of cancers. However, few functional studies are available for miR-21, and few targets have been identified. In this study, we explored the role of miR-21 in human breast cancer cells and tissues, and searched for miR-21 targets.
  
  
  METHODS
  We used in vitro and in vivo assays to explore the role of miR-21 in the malignant progression of human breast cancer, using miR-21 knockdown. Using LNA silencing combined to microarray technology and target prediction, we screened for potential targets of miR-21 and validated direct targets by using luciferase reporter assay and Western blot. Two candidate target genes (EIF4A2 and ANKRD46) were selected for analysis of correlation with clinicopathological characteristics and prognosis using immunohistochemistry on cancer tissue microrrays.
  
  
  RESULTS
  Anti-miR-21 inhibited growth and migration of MCF-7 and MDA-MB-231 cells in vitro, and tumor growth in nude mice. Knockdown of miR-21 significantly increased the expression of ANKRD46 at both mRNA and protein levels. Luciferase assays using a reporter carrying a putative target site in the 3' untranslated region of ANKRD46 revealed that miR-21 directly targeted ANKRD46. miR-21 and EIF4A2 protein were inversely expressed in breast cancers (rs = -0.283, P = 0.005, Spearman's correlation analysis).
  
  
  CONCLUSIONS
  Knockdown of miR-21 in MCF-7 and MDA-MB-231 cells inhibits in vitro and in vivo growth as well as in vitro migration. ANKRD46 is newly identified as a direct target of miR-21 in BC. These results suggest that inhibitory strategies against miR-21 using peptide nucleic acids (PNAs)-antimiR-21 may provide potential therapeutic applications in breast cancer treatment.
authors.affiliation: State Key Laboratory of Oncology in Southern China, Sun Yat-Sen University Cancer Center, 651 Dong Feng Road East, Guangzhou, 510060, PR China.
authors.forename: Li Xu
authors.initials: LX
authors.lastname: Yan
authors.forename: Qi Nian
authors.initials: QN
authors.lastname: Wu
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yang Yang
authors.initials: YY
authors.lastname: Li
authors.forename: Ding Zhun
authors.initials: DZ
authors.lastname: Liao
authors.forename: Jing Hui
authors.initials: JH
authors.lastname: Hou
authors.forename: Jia
authors.initials: J
authors.lastname: Fu
authors.forename: Mu Sheng
authors.initials: MS
authors.lastname: Zeng
authors.forename: Jing Ping
authors.initials: JP
authors.lastname: Yun
authors.forename: Qiu Liang
authors.initials: QL
authors.lastname: Wu
authors.forename: Yi Xin
authors.initials: YX
authors.lastname: Zeng
authors.forename: Jian Yong
authors.initials: JY
authors.lastname: Shao
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D001483:Base Sequence; D001943:Breast Neoplasms / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics*; D049109:Cell Proliferation; D016000:Cluster Analysis; D053487:DEAD-box RNA Helicases / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D035683:MicroRNAs / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D008875:Middle Aged; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D020319:Oligodeoxyribonucleotides, Antisense / Q000378:metabolism; D020135:Peptide Nucleic Acids / Q000378:metabolism; D011379:Prognosis; D016415:Sequence Alignment; D023041:Xenograft Model Antitumor Assays
chemical_list: C430868:ANKRD46 protein, human; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; D009124:Muscle Proteins; D020319:Oligodeoxyribonucleotides, Antisense; D020135:Peptide Nucleic Acids; D053487:DEAD-box RNA Helicases