Expression of sodium iodide symporter in metastatic and follicular human thyroid tissues

Active iodide uptake across the basal membrane mediated by human sodium iod ide symporter (hNIS) has been shown to be a process coupled with the flow o f sodium. There is still controversy as to the amount of hNIS expression pr esent in different kinds of human thyroid cancer tissues. In this study, we present a 58-year-old women with follicular thyroid carcinoma with vertebr a and skull metastases. Tl-201 and 5 mCi I-131 scans clearly demonstrated t he metastatic lesions in the brain of this patient. Thyroid and metastatic tissues were then obtained for this study, which is aimed at comparing the iodide trapping ability in vivo and in vitro of hNIS, and then comparing th eir expression in both thyroid tissue and metastatic tissues. Polyclonal an tibodies to hNIS and competitive RT-PCR were used to analyze the symporter protein and mRNA expressed in follicular human thyroid and metastatic tissu es. Positive staining of the symporter protein was performed in the follicu lar thyroid carcinomas, otherwise, the metastatic tissues could not have de monstrated the protein in the staining. Follicular thyroid carcinoma tissue s from thyroid were revealed around 5 pg hNIS expressed in follicular thyro id carcinoma tissues from the thyroid. Otherwise, there was almost an absen ce of hNIS expression in the metastatic tissue. These discrepancies of the expression in hNIS in vivo and in vitro studies need further investigation.