title: Claudin 1 overexpression increases invasion and is associated with aggressive histological features in oral squamous cell carcinoma.
abstract: BACKGROUND
  The authors have previously shown that overexpression of claudin 1 (CLDN1) is associated with advanced disease stage in oral squamous cell carcinomas (OSCCs). Their goal was to examine CLDN1 expression in a large series of primary OSCCs and to further investigate whether CLDN1 overexpression plays a role in invasion in OSCC.
  
  
  METHODS
  CLDN1 gene expression levels were determined by quantitative real-time reverse transcription polymerase chain reaction (QRT-PCR) in 100 primary OSCCs. CLDN1 protein expression was examined by immunohistochemistry in 70 of 100 OSCCs. E-Cadherin protein levels were also assessed in 58 OSCCs. The authors performed a transwell Matrigel invasion assay for assessment of the invasive potential of CLDN1 overexpressing oral carcinoma cells. Western blotting and QRT-PCR were used to assess CLDN1 expression in transfected cells and controls.
  
  
  RESULTS
  CLDN1 mRNA was increased (median = 18.5) in 79 of 100 OSCCs, compared with normal oral mucosa (expression = 1.0). CLDN1 overexpression was associated with angiolymphatic (P = .037) and perineural invasion (P = .051). CLDN1 was highly expressed in 48 of 70 (68%) OSCCs. E-Cadherin was lost or underexpressed in 49 of 58 (84%) OSCCs. The invasion assay showed that cells overexpressing CLDN1 have increased invasive potential, whereas small interfering RNA-mediated depletion of CLDN1 decreased the invasive potential of cells.
  
  
  CONCLUSIONS
  CLDN1 overexpression is associated with angiolymphatic and perineural invasion, consistent with aggressive tumor behavior. Overexpression of CLDN1 protein is associated with increased invasiveness of oral carcinoma cells.
authors.affiliation: Division of Applied Molecular Oncology, Princess Margaret Hospital, University Health Network, Toronto, Ontario, Canada.
authors.forename: Patricia Pintor
authors.initials: PP
authors.lastname: Dos Reis
authors.forename: Rikki R
authors.initials: RR
authors.lastname: Bharadwaj
authors.forename: Jerry
authors.initials: J
authors.lastname: Machado
authors.forename: Christina
authors.initials: C
authors.lastname: Macmillan
authors.forename: Melania
authors.initials: M
authors.lastname: Pintilie
authors.forename: Mahadeo A
authors.initials: MA
authors.lastname: Sukhai
authors.forename: Bayardo
authors.initials: B
authors.lastname: Perez-Ordonez
authors.forename: Patrick
authors.initials: P
authors.lastname: Gullane
authors.forename: Jonathan
authors.initials: J
authors.lastname: Irish
authors.forename: Suzanne
authors.initials: S
authors.lastname: Kamel-Reid
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000378:metabolism; D062445:Claudin-1; D004268:DNA-Binding Proteins; D005260:Female; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000235:genetics*; D009361:Neoplasm Invasiveness / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C568108:CLDN1 protein, human; D062445:Claudin-1; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D012333:RNA, Messenger; C484746:RSPH1 protein, human