title: Loss of miR-638 in vitro promotes cell invasion and a mesenchymal-like transition by influencing SOX2 expression in colorectal carcinoma cells.
abstract: BACKGROUND
  Colorectal carcinoma (CRC) is a major cause of cancer mortality. The aberrant expression of several microRNAs is associated with CRC progression; however, the molecular mechanisms underlying this phenomenon are unclear.
  
  
  METHODS
  miR-638 and SRY-box 2 (SOX2) expression levels were detected in 36 tumor samples and their adjacent, non-tumor tissues from patients with CRC, as well as in 4 CRC cell lines, using real-time quantitative RT-PCR (qRT-PCR). SOX2 expression levels were detected in 90 tumor samples and their adjacent tissue using immunohistochemistry. Luciferase reporter and Western blot assays were used to validate SOX2 as a target gene of miR-638. The regulation of SOX2 expression by miR-638 was assessed using qRT-PCR and Western blot assays, and the effects of exogenous miR-638 and SOX2 on cell invasion and migration were evaluated in vitro using the HCT-116 and SW1116 CRC cell lines.
  
  
  RESULTS
  We found that miR-638 expression was differentially impaired in CRC specimens and dependent on tumor grade. The inhibition of miR-638 by an antagomiR promoted cell invasion and a mesenchymal-like transition (lamellipodium stretching increased and cell-cell contacts decreased, which was accompanied by the suppression of the epithelial cell marker ZO-1/E-cadherin and the upregulation of the mesenchymal cell marker vimentin). A reporter assay revealed that miR-638 repressed the luciferase activity of a reporter gene coupled to the 3'-untranslated region of SOX2. miR-638 overexpression downregulated SOX2 expression, and miR-638 inhibition upregulated SOX2 expression. Moreover, miR-638 expression levels were correlated inversely with SOX2 mRNA levels in human CRC tissues. The RNAi-mediated knockdown of SOX2 phenocopied the invasion-inhibiting effect of miR-638; furthermore, SOX2 overexpression blocked the miR-638-induced CRC cell transition to epithelial-like cells.
  
  
  CONCLUSIONS
  These results demonstrate that the loss of miR-638 promotes invasion and a mesenchymal-like transition by directly targeting SOX2 in vitro. These findings define miR-638 as a new, invasion-associated tumor suppressor of CRC.
authors.forename: Kelong
authors.initials: K
authors.lastname: Ma
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Pan
authors.forename: Pingsheng
authors.initials: P
authors.lastname: Fan
authors.forename: Yinghua
authors.initials: Y
authors.lastname: He
authors.forename: Jun
authors.initials: J
authors.lastname: Gu
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Tengyue
authors.initials: T
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Oncogenes & Related Genes, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiaotong University School of Medicine, No, 25/Ln2200, XieTu Rd, Shanghai 200032, China. zonghaili@shsmu.edu.cn.
authors.forename: Zonghai
authors.initials: Z
authors.lastname: Li
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Luo
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D044127:Epigenesis, Genetic; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D035683:MicroRNAs / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D060787:Neoplasm Grading; D009361:Neoplasm Invasiveness; D011379:Prognosis; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D055748:SOXB1 Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D014746:Vimentin / Q000235:genetics / Q000378:metabolism; D062826:Zonula Occludens-1 Protein / Q000235:genetics / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
chemical_list: D015415:Biomarkers; C495270:CTNNB1 protein, human; D015820:Cadherins; C572154:MIRN638 microRNA, human; D035683:MicroRNAs; D034741:RNA, Small Interfering; C527782:SOX2 protein, human; D055748:SOXB1 Transcription Factors; C569042:TJP1 protein, human; D014746:Vimentin; D062826:Zonula Occludens-1 Protein; D051176:beta Catenin; D049452:Green Fluorescent Proteins