Expression of sodium iodide symporter in benign and malignant human thyroid tissues

The extent of human sodium iodide symporter (hNIS) expression in different kinds of human thyroid cancer tissues and cell lines remains controversial. In this study, polyclonal antibodies to hNIS were used to analyze the expr ession of symporter protein in benign and malignant human thyroid tissues. Formalin-fixed, paraffin wax-embedded tissue sections were used. Staining w as performed using primary polyclonal antibody of rabbit anti-human hNIS di luted in PBS (1:500). Results showed that 2 of 3 normal tissue, 3 of 6 nodu lar hyperplasia, one follicular adenoma, 3 of 11 papillary thyroid carcinom a, 1 of 5 follicular carcinoma and none of 3 metastatic thyroid epithelial tissue specimens stained positively for hNIS. A higher percentage of positi ve staining for symporter protein was found in benign thyroid tissues inclu ding normal thyroid tissue, nodular hyperplasia, and adenoma (60%). In cont rast, papillary and follicular thyroid carcinomas demonstrated lower sympor ter protein expression (20%). In conclusion, although the number of tissue samples examined in this study was small, hNIS staining found a higher rati o of sym porter protein expression in normal and benign thyroid tissues com pared with malignant tissues. Determination of the reason for discrepancies in the expression of hNIS in in vivo and in vitro studies will require fur ther investigation.