人钠碘转运体mRNA在良恶性甲状腺疾病中表达的研究

目的探讨人钠碘转运体（hNIS）mRNA在良恶性甲状腺疾病中的表达及其在疾病诊断中的价值.方法24例Graves病,27例桥本氏甲状腺炎,21例亚急性甲状腺炎,24例无功能性甲状腺结节性增生,22例无功能性腺瘤,21例乳头状甲状腺癌及17例滤泡状甲状腺癌（其中4例颈部淋巴转移）,经细针抽吸甲状腺组织,用实时荧光定量PCR法测定hNIS mRNA的表达.结果良性与恶性甲状腺疾病间hNIS mRNA表达量无显著差异（P＞0.05）,各组间亦无显著差异（P＞0.05）.4例颈部淋巴转移病灶其原发癌表达阳性,但只有2例转移灶表达阳性.结论hMSmRNA定量检测不能用于良恶性甲状腺疾病的鉴别.颈部转移淋巴中有部分未表达hNIS mRNA而原发灶有表达,其机理值得探讨.     

Use of sodium iodide symporter expression in differentiated thyroid carcinomas

Objective We aimed to investigate the use of NIS mRNA and protein expression as a diagnostic and/or prognostic marker in patients with differentiated thyroid cancer (DTC). Design This is a case–control study. Patients We studied 397 thyroid nodules tissue samples, including 224 papillary thyroid carcinomas (PTCs), 41 follicular carcinomas, 58 nodular goiters, 56 follicular adenomas and 18 normal tissues assembled in a tissue microarray. Measurements NIS protein was identified using a monoclonal antibody that labelled only the follicular cell basolateral membrane of all 397 tissue samples. In addition, NIS mRNA was quantified in 145 DTC patients and 85 PTC cases were screened for BRAF^V600E mutation. Results We found low NIS mRNA expression and low or negative NIS protein expression in most DTC. NIS expression was lower in DTC patients over 45 years old and in tumours larger than 2 cm. There was a tendency for lower NIS expression in advanced stages and patients presenting recurrences. All 13 DTC patients who succumbed to the disease were NIS negative at immunohistochemistry and had very low mRNA expression. NIS expression was lower in PTC presenting BRAF^V600E mutation. However, neither NIS immunohistochemical analysis nor NIS mRNA quantified expression could identify individuals with poor prognosis. Conclusions Our data suggest that NIS expression may help characterize patients’ risk and individuals with a poor response to therapy, but is not useful as a diagnostic or prognostic marker, reinforcing the current concept that an appropriate management of DTC patient is the most important and modifiable prognostic factor.     

Enhancement of sodium/iodide symporter expression in thyroid and breast cancer

The sodium/iodide symporter (NIS) mediates iodide uptake in the thyroid gland and lactating breast. NIS mRNA and protein expression are detected in most thyroid cancer specimens, although functional iodide uptake is usually reduced resulting in the characteristic finding of a 'cold' or non-functioning lesion on a radioiodine image. Iodide uptake after thyroid stimulating hormone (TSH) stimulation, however, is sufficient in most differentiated thyroid cancer to utilize beta-emitting radioactive iodide for the treatment of residual and metastatic disease. Elevated serum TSH, achieved by thyroid hormone withdrawal in athyreotic patients or after recombinant human thyrotropin administration, directly stimulates NIS gene expression and/or NIS trafficking to the plasma membrane, increasing radioiodide uptake. Approximately 10-20% differentiated thyroid cancers, however, do not express the NIS gene despite TSH stimulation. These tumors are generally associated with a poor prognosis. Reduced NIS gene expression in thyroid cancer is likely due in part, to impaired trans-activation at the proximal promoter and/or the upstream enhancer. Basal NIS gene expression is detected in about 80% breast cancer specimens, but the fraction with functional iodide transport is relatively low. Lactogenic hormones and various nuclear hormone receptor ligands increase iodide uptake in breast cancer cells in vitro, but TSH has no effect. A wide range of 'differentiation' agents have been utilized to stimulate NIS expression in thyroid and breast cancer using in vitro and in vivo models, and a few have been used in clinical studies. Retinoic acid has been used to stimulate NIS expression in both thyroid and breast cancer. There are similarities and differences in NIS gene regulation and expression in thyroid and breast cancer. The various agents used to enhance NIS expression in thyroid and breast cancer will be reviewed with a focus on the mechanism of action. Agents that promote tumor differentiation, or directly stimulate NIS gene expression, may result in iodine concentration in 'scan-negative' thyroid cancer and some breast cancer.     

钠碘转运体与甲状腺疾病

钠碘转运体(NIS)为甲状腺滤泡上皮细胞基底膜上的一类膜蛋白，主要作用是促进甲状腺逆浓度梯度转运无机碘，NIS受促甲状腺激素、碘、多种细胞因子及其他一些激素的调节。NIS与自身免疫性疾病、先天性甲状腺功能低下、甲状腺肿瘤的发生密切相关，对其进行深入研究对甲状腺疾病的治疗具有重要的临床价值。     

Expression of the human sodium/iodide symporter (hNIS) in xenotransplanted human thyroid carcinoma.

The uptake of iodide in thyroid epithelial cells is mediated by the sodium/iodide symporter (NIS). The uptake of iodide is of vital importance for thyroid physiology and is a prerequisite for radioiodine therapy in thyroid cancer. Loss of iodide uptake due to diminished expression of the human NIS (hNIS) is frequently observed in metastasized thyroid cancer. So far, no animal model for the study of radioiodine therapy in thyroid cancer has been available. Strategies to restore iodide uptake in thyroid cancer include the exploration of hNIS gene transfer into hNIS defective thyroid cancer. We have performed a stable transfection of hNIS into the hNIS defective follicular thyroid carcinoma cell line FTC133. Stably transfected colonies exhibited high uptake of Na125I, which could be blocked completely with sodium perchlorate. hNIS transfected FTC133 and non-transfected cell lines injected subcutaneously in nude mice formed tumors after 6 weeks. Iodide uptake in the hNIS transfected tumor was much higher than in non-transfected tumor, but a rapid release of radioactivity from the hNIS transfected tumor was observed. Further studies are necessary to investigate the role of hNIS in relation to other thyroid specific proteins in iodide metabolism in thyroid cancer.     

碘对大鼠甲状腺钠碘转运体mRNA表达及甲状腺功能的影响

观察不同碘摄入量对大鼠甲状腺钠碘转运体（NIS）mRNA、血清甲状腺激素、尿碘水平以及甲状腺组织碘含量的影响。低碘组NIS mRNA表达明显增强，而血清甲状腺激素、尿碘、甲状腺组织碘含量显著下降。高碘组NIS mRNA表达受到抑制，甲状腺激素有下降趋势。提示NIS是甲状腺自身调节的重要组成部分。高碘、低碘均可导致甲状腺功能低下。     

甲状腺乳头状癌组织中钠碘转运体基因启动子甲基化的研究

用甲基化特异性PCR检测34例甲状腺乳头状癌及癌旁组织中钠碘转运体(NIS)基因启动子的甲基化.结果显示癌组织中NIS基因启动子甲基化显著高于癌旁组织(P＜0.05),淋巴结转移组中NIS基因启动子的甲基化显著高于无淋巴结转移组(P＜0.05),提示NIS基因启动子异常甲基化是甲状腺乳头状癌发展过程中常见的分子事件,可能影响了甲状腺乳头状癌细胞的摄碘功能.     

维甲酸对甲状腺癌细胞钠/碘转运体基因的调节作用

以RTPCR法检测维甲酸对甲状腺癌细胞钠/碘转运体(NIS)基因表达的影响,发现在5～50μmol/L的剂量区间,维甲酸能促进NIS基因表达,提示维甲酸在甲状腺癌及其转移灶的治疗中可能起到重要作用。     

Regulation of sodium iodide symporter gene expression in FRTL-5 rat thyroid cells.

The sodium iodide symporter (NIS), first identified in FRTL-5 cells, plays a critical role in iodide transport in the thyroid gland and in the production of the iodine-containing thyroid hormones. The aim of our study was to examine the regulation of NIS RNA steady-state levels and protein expression as well as functional activity in FRTL-5 cells. FRTL-5 cells cycling in media containing thyrotropin (TSH) were incubated for 48 hours with dexamethasone (10(-8)-10(-5) M), triiodothyronine (T3; 10(-9)-10(-6) M), methimazole (100 microM), propylthiouracil (PTU; 100 microM), perchlorate (10 microM) and potassium iodide (40 microM). In other experiments, cells were treated for 48 hours with various cytokines including interleukin-6 (IL-6) (100 U/mL), interferon-gamma (IFN-gamma) (100 U/mL), tumor necrosis factor-alpha (TNF-alpha) (10 ng/ml), IL-1alpha (100 U/mL), and IL-1beta (100 U/mL). Northern blot analysis using a 32P-labeled rat NIS-specific cDNA probe (nucleotides 1397-1937) revealed NIS mRNA as a single species of approximately 3 kb. When normalized for beta-actin mRNA signal intensities, NIS RNA steady-state levels in viable FRTL-5 cells were suppressed by approximately 80% after incubation with dexamethasone and T3 in a concentration-dependent manner. Iodide accumulation was decreased by up to 40% after incubation with dexamethasone and T3, respectively, in a concentration-dependent manner. Using a rabbit polyclonal rNIS-specific antibody, Western blot analysis of FRTL-5 cell membranes revealed a 60% and 70% suppression of NIS protein expression after treatment with T3 (0.1 microM) and dexamethasone (1 microM), respectively. In additon, NIS RNA steady-state levels were decreased by approximately 50% after treatment of monolayers with methimazole, PTU, and potassium iodide, respectively. Incubation with methimazole and PTU resulted in a 20% and 25% decrease of iodide accumulation, respectively, whereas potassium iodide suppressed iodide accumulation by approximately 50%. Treatment of FRTL-5 cells with IL-6 and IL-1beta resulted in a 30% decrease of NIS RNA steady-state levels. IL-6 did not alter NIS functional activity, but IL-1beta suppressed iodide accumulation by approximately 25%. IFN-gamma and perchlorate failed to alter NIS RNA steady-state levels. In contrast to IFN-gamma that had no effect on iodide accumulation, perchlorate almost completely suppressed iodide accumulation. TNF-alpha and IL-1alpha failed to alter NIS RNA steady-state levels in higher passage numbers of FRTL-5 cells, whereas treatment with TNF-alpha and IL-1alpha of early passages of FRTL-5 cells (<20 cell passages) resulted in a 70% and 40% decrease of NIS RNA steady-state levels, respectively, and in a 20% suppression of NIS functional activity. In conclusion, our data suggest that various agents known to affect iodide transport are capable of differentially altering NIS gene expression and function in cultured thyroid cells. Suppression of NIS gene expression and function by certain cytokines may be responsible, at least in part, for the impaired radioiodine uptake by thyroid tissue in certain forms of thyroiditis.     

一氧化氮对人甲状腺细胞钠/碘转运体的影响

目的 研究一氧化氮(NO)供体硝普钠(SNP)对体外培养人甲状腺细胞钠／碘转运体(NIS)的作用。方法 采用细胞培养方法，观察不同浓度的SNP对甲状腺细胞摄碘能力和Na^ -K^ -ATP酶的影响，并分析NIS与Na^ -K^ -ATP酶的关系。结果 ①SNP(10^-6-10^-3mol／L)呈剂量依赖性抑制甲状腺细胞碘的摄取，除去SNP继续培养48h，细胞恢复摄碘能力；②SNP(10^-6-10^-mol／L)呈剂量依赖性抑制Na^ -K^ -ATP酶的活力；③NIS与Na^ -K^ -ATP酶呈正相关(r=0．95)。结论 NO能抑制甲状腺细胞NIS的摄碘功能，这可能与NO促进细胞内cGMP水平增加和抑制甲状腺细胞Na^ -K^ -ATP酶有关。     

The importance of sodium/iodide symporter (NIS) for thyroid cancer management

The thyroid gland has the ability to uptake and concentrate iodide, which is a fundamental step in thyroid hormone biosynthesis. Radioiodine has been used as a diagnostic and therapeutic tool for several years. However, the studies related to the mechanisms of iodide transport were only possible after the cloning of the gene that encodes the sodium/iodide symporter (NIS). The studies about the regulation of NIS expression and the possibility of gene therapy with the aim of transferring NIS gene to cells that normally do not express the symporter have also become possible. In the majority of hypofunctioning thyroid nodules, both benign and malignant, NIS gene expression is maintained, but NIS protein is retained in the intracellular compartment. The expression of NIS in non-thyroid tumoral cells in vivo has been possible through the transfer of NIS gene under the control of tissue-specific promoters. Apart from its therapeutic use, NIS has also been used for the localization of metastases by scintigraphy or PET-scan with 124I. In conclusion, NIS gene cloning led to an important development in the field of thyroid pathophysiology, and has also been fundamental to extend the use of radioiodine for the management of non-thyroid tumors.     

Renal metastases from thyroid papillary carcinoma: study of sodium iodide symporter expression.

Kidney metastases from thyroid cancer are rare. We report two such patients and demonstrate that the in vivo 131I uptake by the kidney metastasis is associated with high levels of sodium iodide (Na+/I-) symporter (NIS) expression in the first case. Case 1: A 61-year-old woman with papillary thyroid carcinoma-follicular variant (PTC-FV) presented with scapular metastasis. After thyroidectomy and scapulectomy, a 131I posttherapy scan showed left upper quadrant uptake. A 3.0-cm metastatic PTC-FV deposit was removed by partial nephrectomy. Case 2: A 53-year-old woman presented with back pain. A computed tomography (CT) scan showed a 3.5-cm renal mass, a multinodular goiter, and lung metastases thought secondary to a renal cell carcinoma. A unilateral nephrectomy revealed metastatic PTC-FV. After thyroidectomy, a 131I posttherapy scan showed lung and skeletal metastases. NIS immunoreactivity in tumoral tissue was strongly positive in the primary tumor, shoulder, and kidney metastasis in case 1, as well as in the primary tumor in case 2. Spotty, low-level NIS expression was observed in the kidney metastasis in case 2. In conclusion, kidney metastases of PTC-FV may occasionally retain adequate levels of NIS expression, enabling their detection during life. Thus, intense uptake in the abdomen during 131I imaging should not be assumed to be physiological gastrointestinal tract residual radionuclide activity.