title: Snail1 induces epithelial-to-mesenchymal transition and tumor initiating stem cell characteristics.
abstract: BACKGROUND
  Tumor initiating stem-like cells (TISCs) are a subset of neoplastic cells that possess distinct survival mechanisms and self-renewal characteristics crucial for tumor maintenance and propagation. The induction of epithelial-mesenchymal-transition (EMT) by TGFβ has been recently linked to the acquisition of TISC characteristics in breast cancer. In HCC, a TISC and EMT phenotype correlates with a worse prognosis. In this work, our aim is to elucidate the underlying mechanism by which cells acquire tumor initiating characteristics after EMT.
  
  
  METHODS
  Gene and protein expression assays and Nanog-promoter luciferase reporter were utilized in epithelial and mesenchymal phenotype liver cancer cell lines. EMT was analyzed with migration/invasion assays. TISC characteristics were analyzed with tumor-sphere self-renewal and chemotherapy resistance assays. In vivo tumor assay was performed to investigate the role of Snail1 in tumor initiation.
  
  
  CONCLUSIONS
  TGFβ induced EMT in epithelial cells through the up-regulation of Snail1 in Smad-dependent signaling. Mesenchymal liver cancer post-EMT demonstrates TISC characteristics such as tumor-sphere formation but are not resistant to cytotoxic therapy. The inhibition of Snail1 in mesenchymal cells results in decreased Nanog promoter luciferase activity and loss of self-renewal characteristics in vitro. These changes confirm the direct role of Snail1 in some TISC traits. In vivo, the down-regulation of Snail1 reduced tumor growth but was not sufficient to eliminate tumor initiation. In summary, TGFβ induces EMT and TISC characteristics through Snail1 and Nanog up-regulation. In mesenchymal cells post-EMT, Snail1 directly regulates Nanog expression, and loss of Snail1 regulates tumor growth without affecting tumor initiation.
authors.affiliation: Department of Pediatrics and Pharmacology, The Pennsylvania State University, College of Medicine, Penn State Children's Hospital, Hershey, USA.
authors.forename: Hien
authors.initials: H
authors.lastname: Dang
authors.forename: Wei
authors.initials: W
authors.lastname: Ding
authors.forename: Dow
authors.initials: D
authors.lastname: Emerson
authors.forename: C Bart
authors.initials: CB
authors.lastname: Rountree
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects / Q000235:genetics*; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism; D051379:Mice; D000071317:Nanog Homeobox Protein; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D015398:Signal Transduction; D051785:Smad Proteins; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D018398:Homeodomain Proteins; D000071317:Nanog Homeobox Protein; C475540:Nanog protein, mouse; C000604407:SNAI1 protein, human; D051785:Smad Proteins; C000604429:Snai1 protein, mouse; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D016212:Transforming Growth Factor beta