title: Down-regulation of claudin-2 in breast carcinomas is associated with advanced disease.
abstract: OBJECTIVE
  Claudin 2 (CLDN2) is a family of integral membrane tight junctions. The aim was to determine the influence of CLDN2 expression on tumour behaviour and its role in breast carcinogenesis.
  
  
  RESULTS
  Thirty-seven invasive breast carcinomas and corresponding normal breast tissues were examined for CLDN2 protein and mRNA expression using Western blotting and semiquantitative reverse transcriptase-polymerase chain reaction. The expression of CLDN2 protein in 118 cases of breast carcinoma was further studied with immunohistochemistry and related to various clinicopathological parameters. CLDN2 protein expression was significantly down-regulated (0.4-fold) in tumours compared with corresponding normal breast tissue (P < 0.0001). Down-regulation of CLDN2 was significantly associated with lymph node metastasis (P = 0.047) by Western blot analysis, and with high clinical stage (P = 0.040) by immunohistochemistry. The expression levels of CLDN2 mRNA in high clinical stages (stages II and III) were lower than those in low clinical stage (stage I) and normal tissue, but not statistically significantly so.
  
  
  CONCLUSIONS
  These results suggest that CLDN2 is implicated in the progression as well as the development of breast carcinoma, indicating that CLDN2 is a possible tumour suppressor gene product.
authors.affiliation: Department of Pathology, Bundang CHA Hospital, Gyonggi-do, Korea.
authors.forename: T H
authors.initials: TH
authors.lastname: Kim
authors.forename: J H
authors.initials: JH
authors.lastname: Huh
authors.forename: S
authors.initials: S
authors.lastname: Lee
authors.forename: H
authors.initials: H
authors.lastname: Kang
authors.forename: G I
authors.initials: GI
authors.lastname: Kim
authors.forename: H J
authors.initials: HJ
authors.lastname: An
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D001940:Breast / Q000378:metabolism / Q000473:pathology; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D057167:Claudins; D015536:Down-Regulation; D005260:Female; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007124:Immunoenzyme Techniques; D008198:Lymph Nodes / Q000378:metabolism / Q000473:pathology; D008207:Lymphatic Metastasis / Q000235:genetics / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009367:Neoplasm Staging; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D014408:Biomarkers, Tumor; C491875:CLDN2 protein, human; D057167:Claudins; D008565:Membrane Proteins; D012333:RNA, Messenger