Development of reverse transcription competitive polymerase chain reactionmethod to quantitate the expression levels of human sodium iodide symporter

The sodium iodide symporter (NIS) is the plasma membrane protein that media tes active iodide uptake into thyroid follicular cells. To investigate whet her human MS (hNIS) mRNA levels in papillary thyroid carcinomas (PCs) corre late with the ability of tumors to concentrate radioiodide, we developed a reverse transcription-competitive polymerase chain reaction (RT-cPCR) metho d to quantify the hNIS mRNA levels in thyroid tissues. We studied 7 normal thyroid tissues, 8 PCs, and 1 follicular adenoma. hNIS mRNA levels in PCs w ere generally lower than those found in normal thyroid tissues. The reduced radioiodide concentrating activity of PCs is due, at least in part, to the reduced expression and/or the decreased stability of hNIS mRNA.