title: Genetic and epigenetic down-regulation of microRNA-212 promotes colorectal tumor metastasis via dysregulation of MnSOD.
abstract: OBJECTIVE
  Altered functions of microRNAs (miRNAs) have been associated with colorectal cancer (CRC). miR-212 is transcribed from a stable intron of a non-protein coding gene, and is reportedly down-regulated in different tumor types. We investigated the role of miR-212 in colorectal carcinogenesis and progression.
  
  
  METHODS
  We analyzed the expression of miR-212 by real-time polymerase chain reaction (PCR) analysis of colorectal cell lines and 180 paired tumor samples and surrounding healthy tissue. We overexpressed and knocked down miR-212 in CRC cell lines and assessed the in vitro effects. We also studied the effects of miR-212 overexpression on metastasis of tumors grown from HCT116 cells in nude mice.
  
  
  RESULTS
  Overexpression of miR-212 inhibited CRC cell migration and invasion in vitro and formation of intrahepatic and pulmonary metastasis in vivo. We identified manganese superoxide dismutase (MnSOD) messenger RNA as a direct target of miR-212, and observed an inverse correlation between the level of miR-212 and MnSOD protein in colorectal tumor samples. MnSOD was required for down-regulation of epithelial markers and up-regulation of mesenchymal markers in CRC cells, indicating that it promoted the epithelial-mesenchymal transition. Overexpression of miR-212 reduced the levels of MnSOD to block the epithelial-mesenchymal transition process. Loss of heterozygosity and promoter hypermethylation each contributed to the down-regulation of miR-212. Reduced levels of miR-212 were associated with a more aggressive tumor phenotype and short disease-free survival times of patients (P = .0045; overall survival, P = .0015).
  
  
  CONCLUSIONS
  miR-212 is down-regulated in human CRC tissues via genetic and epigenetic mechanisms. miR-212 might prevent tumor progression by targeting MnSOD messenger RNA; reduction of miR-212 could be a prognostic marker for patients with CRC. miR-212 and MnSOD might also be therapeutic targets for cancer.
authors.affiliation: State Key Laboratory of Oncology in South China, Sun Yat-sen University Cancer Center, Guangzhou, PR China.
authors.forename: Xiangqi
authors.initials: X
authors.lastname: Meng
authors.forename: Jiangxue
authors.initials: J
authors.lastname: Wu
authors.forename: Changchuan
authors.initials: C
authors.lastname: Pan
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Ying
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhou
authors.forename: Hongyan
authors.initials: H
authors.lastname: Yu
authors.forename: Yufang
authors.initials: Y
authors.lastname: Zuo
authors.forename: Zhizhong
authors.initials: Z
authors.lastname: Pan
authors.forename: Ran-Yi
authors.initials: RY
authors.lastname: Liu
authors.forename: Wenlin
authors.initials: W
authors.lastname: Huang
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D018572:Disease-Free Survival; D015536:Down-Regulation; D044127:Epigenesis, Genetic; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008819:Mice, Nude; D035683:MicroRNAs / Q000235:genetics*; D009361:Neoplasm Invasiveness / Q000235:genetics; D009368:Neoplasm Transplantation; D012333:RNA, Messenger; D060888:Real-Time Polymerase Chain Reaction; D013482:Superoxide Dismutase / Q000235:genetics*
chemical_list: C551411:MIRN212 microRNA, human; D035683:MicroRNAs; D012333:RNA, Messenger; D013482:Superoxide Dismutase
keywords: 3′-UTR; 3′-untranslated region; CRC; Colorectal Cancer; EMT; Epigenetic Regulation; Gene Expression; Genetic Alteration; LOH; MnSOD; NC; PCR; colorectal cancer; epithelial−mesenchymal transition; loss of heterozygosity; manganese superoxide dismutase; miRNA; microRNA; negative control; polymerase chain reaction; si; small interfering