title: Prospero homeobox 1 promotes epithelial-mesenchymal transition in colon cancer cells by inhibiting E-cadherin via miR-9.
abstract: OBJECTIVE
  Prospero homeobox 1 (PROX1) has been shown to function as a tumor suppressor in various types of cancer. However, it promotes colon cancer progression. The aim of this study is to clarify the underlying mechanism by which PROX1 regulates tumorigenicity of colon cancer.
  
  
  METHODS
  Association of PROX1 and clinicopathological features was studied by immunohistochemical staining. Pri-miR-9-2 and miR-9 were detected by quantitative real-time PCR. Assays of cell invasion, adhesion, and matrix metalloproteinase activity were used to study PROX1-mediated epithelial-mesenchymal transition (EMT).
  
  
  RESULTS
  PROX1 was overexpressed in 43% (59/136) of colon cancer tissues and its expression was correlated with E-cadherin downregulation (P = 0.00005), advanced tumor staging (P = 0.005), and lymph node metastasis (P = 0.000009). Enforced expression of PROX1 in DLD-1 cells caused downregulation of E-cadherin and integrins and attenuated cell adhesion. These cells showed increase of matrix metalloproteinase activity and invasive ability. Conversely, knockdown of PROX1 in SW620 cells restored E-cadherin protein expression and reduced invasiveness. Unexpectedly, repression of E-cadherin by PROX1 was not mediated by transcriptional inhibition. We found that PROX1 bound to miR-9-2 promoter and triggered its expression to suppress E-cadherin 3'UTR reporter activity and protein expression. Anti-miR-9 restored E-cadherin in SW620 cells, whereas precursor miR-9 inhibited E-cadherin in PROX1-knockdown cells. The miR-9 level was higher in tumor tissues with high PROX1/low E-cadherin than that of tumor tissues with low PROX1/high E-cadherin.
  
  
  CONCLUSIONS
  Our results provide mechanistic insights by which PROX1 promotes EMT and colon cancer progression. Targeting of PROX1-mediated oncogenic activity may be helpful for the treatment of colon cancer.
authors.affiliation: Institute of Biomedical Sciences, National Sun Yat-Sen University, Taiwan.
authors.forename: Mei-Hsuan
authors.initials: MH
authors.lastname: Lu
authors.forename: Chao-Cheng
authors.initials: CC
authors.lastname: Huang
authors.forename: Mei-Ren
authors.initials: MR
authors.lastname: Pan
authors.forename: Hong-Hwa
authors.initials: HH
authors.lastname: Chen
authors.forename: Wen-Chun
authors.initials: WC
authors.lastname: Hung
mesh_terms: D015820:Cadherins / Q000235:genetics*; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D004789:Enzyme Activation; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000235:genetics / Q000378:metabolism; D008198:Lymph Nodes / Q000473:pathology; D008207:Lymphatic Metastasis; D020782:Matrix Metalloproteinases / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D009367:Neoplasm Staging; D012323:RNA Processing, Post-Transcriptional; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D000098551:Prospero-Related Homeobox 1 Protein
chemical_list: D015820:Cadherins; D018398:Homeodomain Proteins; D016023:Integrins; C541874:MIRN92 microRNA, human; D035683:MicroRNAs; D025521:Tumor Suppressor Proteins; D000098551:Prospero-Related Homeobox 1 Protein; D020782:Matrix Metalloproteinases