Immunoanalysis indicates that the sodium iodide symporter is not overexpressed in intracellular compartments in thyroid and breast cancers.
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.
Peyrottes
Isabelle
I
Department of Pathology, Center Antoine Lacassagne, 06100, Nice, France.
Navarro
Valerie
V
Ondo-Mendez
Alejandro
A
Marcellin
Didier
D
Bellanger
Laurent
L
Marsault
Robert
R
Lindenthal
Sabine
S
Ettore
Francette
F
Darcourt
Jacques
J
Pourcher
Thierry
T
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
D000911:Antibodies, Monoclonal; D007454:Iodides; D027981:Symporters; D000099209:Sodium-Iodide Symporters