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

Active iodide uptake across the basal membrane mediated by human sodiumiodide symporter (hNIS) has been shown to be a process coupled with the flowof sodium. There is still controversy as to the amount of hNIS expressionpresent in different kinds of human thyroid cancer tissues. In this study, wepresent a 58-year-old women with follicular thyroid carcinoma with vertebraand skull metastases. ²⁰¹Tl and 5 mCi ¹³¹I scans clearlydemonstrated the metastatic lesions in the brain of this patient. Thyroid andmetastatic tissues were then obtained for this study, which is aimed atcomparing the iodide trapping ability in vivo and in vitro of hNIS, and then comparing their expression in both thyroid tissue andmetastatic tissues. Polyclonal antibodies to hNIS and competitive RT–PCRwere used to analyze the symporter protein and mRNA expressed in follicularhuman thyroid and metastatic tissues. Positive staining of the symporterprotein was performed in the follicular thyroid carcinomas, otherwise, themetastatic tissues could not have demonstrated the protein in the staining.Follicular thyroid carcinoma tissues from thyroid were revealed around 5 pghNIS expressed in follicular thyroid carcinoma tissues from the thyroid.Otherwise, there was almost an absence of hNIS expression in the metastatictissue. These discrepancies of the expression in hNIS in vivo and in vitrostudies need further investigation.