title: Immunoanalysis indicates that the sodium iodide symporter is not overexpressed in intracellular compartments in thyroid and breast cancers.
abstract: OBJECTIVE
  The active transport of iodide into thyroid cells is mediated by the Na(+)/I(-) symporter (NIS) located in the basolateral membrane. Strong intracellular staining with anti-NIS antibodies has been reported in thyroid and breast cancers. Our initial objective was to screen tumour samples for intracellular NIS staining and then to study the mechanisms underlying the altered subcellular localization of the transporters.
  
  
  METHODS
  Immunostaining using three different anti-NIS antibodies was performed on paraffin-embedded tissue sections from 93 thyroid or breast cancers. Western blot experiments were carried out to determine the amount of NIS protein in 20 samples.
  
  
  RESULTS
  Using three different anti-NIS antibodies, we observed intracellular staining in a majority of thyroid tumour samples. Control immunohistochemistry and western blot experiments indicated that this intracellular staining was due to non-specific binding of the antibodies. In breast tumours, very weak intracellular staining was observed in some samples. Western blot experiments suggest that this labelling is also non-specific.
  
  
  CONCLUSIONS
  Our results strongly indicate that the NIS protein level is low in thyroid and breast cancers and that the intracellular staining obtained with anti-NIS antibodies corresponds to a non-specific signal. Accordingly, to increase the efficiency of radiotherapy for thyroid cancers and to enable the use of radioiodine in the diagnosis and therapy of breast tumours, improving NIS targeting to the plasma membrane will not be sufficient. Instead, increasing the expression level of NIS should remain the major goal of this field.
authors.affiliation: Department of Pathology, Center Antoine Lacassagne, 06100, Nice, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Peyrottes
authors.forename: Valerie
authors.initials: V
authors.lastname: Navarro
authors.forename: Alejandro
authors.initials: A
authors.lastname: Ondo-Mendez
authors.forename: Didier
authors.initials: D
authors.lastname: Marcellin
authors.forename: Laurent
authors.initials: L
authors.lastname: Bellanger
authors.forename: Robert
authors.initials: R
authors.lastname: Marsault
authors.forename: Sabine
authors.initials: S
authors.lastname: Lindenthal
authors.forename: Francette
authors.initials: F
authors.lastname: Ettore
authors.forename: Jacques
authors.initials: J
authors.lastname: Darcourt
authors.forename: Thierry
authors.initials: T
authors.lastname: Pourcher
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000378:metabolism / Q000473:pathology; D000236:Adenoma / Q000378:metabolism* / Q000473:pathology*; D000818:Animals; D000911:Antibodies, Monoclonal; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology*; D018276:Carcinoma, Medullary / Q000378:metabolism / Q000473:pathology; D002291:Carcinoma, Papillary / Q000378:metabolism / Q000473:pathology; D002462:Cell Membrane / Q000378:metabolism; D006111:Graves Disease / Q000378:metabolism / Q000473:pathology; D050031:Hashimoto Disease / Q000378:metabolism / Q000473:pathology; D022781:Hepatocytes / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D007454:Iodides / Q000378:metabolism; D051379:Mice; D016612:Paraffin Embedding; D027981:Symporters / Q000276:immunology / Q000378:metabolism*; D013964:Thyroid Neoplasms / Q000378:metabolism* / Q000473:pathology*; D000099209:Sodium-Iodide Symporters
chemical_list: D000911:Antibodies, Monoclonal; D007454:Iodides; D027981:Symporters; D000099209:Sodium-Iodide Symporters