Detection of mRNA of sodium iodide symporter in benign and malignant humanthyroid tissues

Human sodium iodide symporter (hNIS) is an intrinsic membrane protein with 12 transmembrane regions, which shows homology to other sodium-dependent tr ansporters. There is controversy as to the amount of hNIS expression in dif ferent kinds of human thyroid cancer tissues and cell lines. In this study, reverse transcription-polymerase chain reaction (RT-PCR) was used to detec t mRNA of hNIS in various fresh normal, benign tissues and malignant human thyroid tissues. The forward primer was nested hNIS-5' primer containing th e sequences: ACCTGGAAATGCGCTTCAGC. The reverse primer was nested hNIS3' pri mer containing the sequences: AAGCATGACACCGCGTGCCA. The results revealed th ree of three normal tissues, six of eight nodular hyperplasia, two of two h yperthyroidism, one of three follicular adenomas, five of ten papillary thy roid carcinomas, one of one follicular carcinoma and zero of one metastatic follicular tissues demonstrated positive res;lts for hNIS in thyroid epith elial cells. A higher percentage of positive results of the symporter mRNA were found in normal benign thyroid tissues and the thyroid tissues of hype rthyroidism, and nodular hyperplasia (84.6%); however follicular adenoma, p apillary and follicular thyroid carcinomas demonstrated a lower percentage of expression in the RT-PCR studies (46.7%). Serum thyrotropin levels and t he degree of differentiated components presented in cancer tissues have bee n mentioned as important factors for hNIS expression in the cancer tissues, The discrepancies of the expression of hNIS in in vivo and in vitro studie s need further investigation. In conclusion, hNIS was found in higher ratio s in normal and benign thyroid tissues than in the malignant tissues. In ad dition, the RT-PCR technique hNIS did not detect the transporter in most pa pillary thyroid cancer tissues, (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.