title: Altered expression of claudin-1 is related with malignancy in canine thyroid tumors.
abstract: OBJECTIVE
  Claudins (CLDNs) are crucial structural and functional components of tight junctions playing an important role in maintaining cell polarity, controlling paracellular diffusion and regulating cell growth and differentiation of epithelial cells. CLDNs are differentially expressed in neoplastic lesions compared to the corresponding healthy tissues; therefore, they are thought to play a role in tumorigenesis and tumor progression. Reduced expression of CLDN-1 has been observed in several types of human cancers, including thyroid tumors. There are no reports of CLDN-1 immunoexpression in normal and neoplastic canine thyroid tissues.
  
  
  METHODS
  CLDN-1 immunoexpression was investigated in normal canine thyroid gland (n=2), benign (n=1) and malignant (n=10) tumors, as well as neoplastic emboli (n=6).
  
  
  RESULTS
  CLDN-1 was constitutively expressed in normal canine follicular epithelium. Ninety percent of the malignant canine thyroid lesions showed absence or reduced CLDN-1 expression compared to that of normal thyroid gland. Additionally, a cytoplasmic subcellular location of CLDN-1 was recorded in the malignant epithelial cells and neoplastic emboli.
  
  
  CONCLUSIONS
  These findings link altered expression of CLDN-1 to neoplastic transformation and suggest that CLDN-1 expression is associated with malignant canine thyroid tumors and their vascular invasion.
authors.affiliation: Department of Pathology and Molecular Immunology of the Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal.
authors.forename: Ana Rute
authors.initials: AR
authors.lastname: Flores
authors.affiliation: Department of Pathology and Molecular Immunology of the Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Rêma
authors.affiliation: Department of Pathology and Molecular Immunology of the Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Porto, Portugal.
authors.forename: Irina
authors.initials: I
authors.lastname: Amorim
authors.affiliation: Department of Pathology and Molecular Immunology of the Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Porto, Portugal fgartner@ipatimup.pt.
authors.forename: Fátima
authors.initials: F
authors.lastname: Gartner
mesh_terms: D000818:Animals; D062445:Claudin-1 / Q000235:genetics* / Q000378:metabolism; D004285:Dogs; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D007150:Immunohistochemistry; D008297:Male; D013961:Thyroid Gland / Q000378:metabolism / Q000473:pathology; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*
chemical_list: D062445:Claudin-1
keywords: Claudin-1 (CLDN-1); canine; dog; immunohistochemistry; thyroid tumors