title: Stable SET knockdown in head and neck squamous cell carcinoma promotes cell invasion and the mesenchymal-like phenotype in vitro, as well as necrosis, cisplatin sensitivity and lymph node metastasis in xenograft tumor models.
abstract: BACKGROUND
  SET/I2PP2A is a multifunctional protein that is up-regulated in head and neck squamous cell carcinoma (HNSCC). The action of SET in HNSCC tumorigenicity is unknown.
  
  
  METHODS
  Stable SET knockdown by shRNA (shSET) was established in three HNSCC cell lines: HN12, HN13, and Cal27. Protein expression and phosphorylated protein levels were determined by Western blotting and immunofluorescence, cell migration and invasion were measured by functional analysis, and PP2A activity was determined using a serine/threonine phosphatase assay. A real-time PCR array was used to quantify 84 genes associated with cell motility. Metalloproteinase (MMP) activity was assessed by zymographic and fluorometric assays. HN12shSET xenograft tumors (flank and tongue models) were established in Balb/c nude mice; the xenograft characteristics and cisplatin sensitivity were demonstrated by macroscopic, immunohistochemical, and histological analyses, as well as lymph node metastasis by histology.
  
  
  RESULTS
  The HN12shSET cells displayed reduced ERK1/2 and p53 phosphorylation compared with control. ShSET reduced HN12 cell proliferation and increased the sub-G1 population of HN12 and Cal27 cells. Increased PP2A activity was also associated with shSET. The PCR array indicated up-regulation of three mRNAs in HN12 cells: vimentin, matrix metalloproteinase-9 (MMP9) and non-muscle myosin heavy chain IIB. Reduced E-cadherin and pan-cytokeratin, as well as increased vimentin, were also demonstrated as the result of SET knockdown. These changes were accompanied by an increase in MMP-9 and MMP-2 activities, migration and invasion. The HN12shSET subcutaneous xenograft tumors presented a poorly differentiated phenotype, reduced cell proliferation, and cisplatin sensitivity. An orthotopic xenograft tumor model using the HN12shSET cells displayed increased metastatic potential.
  
  
  CONCLUSIONS
  SET accumulation has important actions in HNSCC. As an oncogene, SET promotes cell proliferation, survival, and resistance to cell death by cisplatin in vivo. As a metastasis suppressor, SET regulates invasion, the epithelial mesenchymal transition, and metastasis.
authors.forename: Lays M
authors.initials: LM
authors.lastname: Sobral
authors.forename: Lucas O
authors.initials: LO
authors.lastname: Sousa
authors.forename: Ricardo D
authors.initials: RD
authors.lastname: Coletta
authors.forename: Hamilton
authors.initials: H
authors.lastname: Cabral
authors.forename: Lewis J
authors.initials: LJ
authors.lastname: Greene
authors.forename: Eloiza H
authors.initials: EH
authors.lastname: Tajara
authors.forename: J Silvio
authors.initials: JS
authors.lastname: Gutkind
authors.forename: Carlos
authors.initials: C
authors.lastname: Curti
authors.affiliation: Department of Clinical Analysis, Toxicology and Food Sciences, School of Pharmaceutical Sciences of Riberião Preto, University of São Paulo, Av, Café, s/n, 14040-903 Ribeirão Preto, SP, Brazil. andreiaml@usp.br.
authors.forename: Andréia M
authors.initials: AM
authors.lastname: Leopoldino
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000473:pathology*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology; D004268:DNA-Binding Proteins; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics*; D005455:Fluorescent Antibody Technique; D055785:Gene Knockdown Techniques; D006258:Head and Neck Neoplasms / Q000235:genetics* / Q000473:pathology*; D056488:Histone Chaperones / Q000235:genetics*; D006801:Humans; D008207:Lymphatic Metastasis / Q000235:genetics / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009336:Necrosis / Q000473:pathology; D009361:Neoplasm Invasiveness; D010641:Phenotype; D060888:Real-Time Polymerase Chain Reaction; D000077195:Squamous Cell Carcinoma of Head and Neck; D014157:Transcription Factors / Q000235:genetics*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D056488:Histone Chaperones; C513473:SET protein, human; D014157:Transcription Factors; D002945:Cisplatin