title: Claudin-7 down-regulation is an important feature in oral squamous cell carcinoma.
abstract: OBJECTIVE
  Claudins, a large family of essential tight junction (TJ) proteins, are abnormally regulated in human carcinomas, especially claudin-7. The aim of this study was to investigate claudin-7 expression and alterations in oral squamous cell carcinoma (OSCC).
  
  
  RESULTS
  Expression of claudin-7 was analysed in 132 cases of OSCC organized in a tissue microarray. Claudin-7 mRNA transcript was evaluated using real-time polymerase chain reaction and the methylation status of the promoter was also assessed. Claudin-7 was negative in 58.3% of the cases. Loss of claudin-7 protein expression was associated with recurrence (P = 0.019), tumour size (P = 0.014), clinical stage of OSCC (P = 0.055) and disease-free survival (P = 0.015). Down-regulation of the claudin-7 mRNA transcripts was observed in 78% of the cases, in accordance with immunoexpression. Analysis of the methylation status of the promoter region of claudin-7 revealed that treatment of O28 cells (that did not express claudin-7 mRNA transcripts) with 5-Aza-2'-Deoxycytidine (5-Aza-dC) led to the re-expression of claudin-7 mRNA transcript.
  
  
  CONCLUSIONS
  Loss of claudin-7 expression is associated with important subcellular processes in OSCC with impact on clinical parameters.
authors.affiliation: Department of General Pathology, Dental School, University of São Paulo, São Paulo, Brazil. silvialourenco.70@terra.com.br
authors.forename: Silvia Vanessa
authors.initials: SV
authors.lastname: Lourenço
authors.forename: Cláudia Malheiros
authors.initials: CM
authors.lastname: Coutinho-Camillo
authors.forename: Marcilei Elisa Cavicchioli
authors.initials: ME
authors.lastname: Buim
authors.forename: Ana Carolina
authors.initials: AC
authors.lastname: de Carvalho
authors.forename: Roberta Cardim
authors.initials: RC
authors.lastname: Lessa
authors.forename: Cláudia Maria
authors.initials: CM
authors.lastname: Pereira
authors.forename: André Luiz
authors.initials: AL
authors.lastname: Vettore
authors.forename: André Lopes
authors.initials: AL
authors.lastname: Carvalho
authors.forename: José Humberto
authors.initials: JH
authors.lastname: Fregnani
authors.forename: Luiz Paulo
authors.initials: LP
authors.lastname: Kowalski
authors.forename: Fernando Augusto
authors.initials: FA
authors.lastname: Soares
mesh_terms: D000328:Adult; D000368:Aged; D001374:Azacitidine / Q000031:analogs & derivatives / Q000378:metabolism; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D057167:Claudins; D000077209:Decitabine; D015536:Down-Regulation; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000235:genetics* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: C473255:CLDN7 protein, human; D057167:Claudins; D008565:Membrane Proteins; D012333:RNA, Messenger; D000077209:Decitabine; D001374:Azacitidine