Expressions of human sodium iodide symporter mRNA in primary and metastatic papillary thyroid carcinomas

Molecular Imaging of Innate Immunity and Immunotherapy

The innate immune system plays a key role as the first line of defense in various human diseases including cancer, cardiovascular and inflammatory diseases. In contrast to tissue biopsies and blood biopsies, in vivo imaging of the innate immune system can provide whole body measurements of immune cell location and function and changes in response to disease progression and therapy. Rationally developed molecular imaging strategies can be used in evaluating the status and spatio-temporal distributions of the innate immune cells in near real-time, mapping the biodistribution of novel innate immunotherapies, monitoring their efficacy and potential toxicities, and eventually for stratifying patients that are likely to benefit from these immunotherapies. In this review, we will highlight the current state-of-the-art in noninvasive imaging techniques for preclinical imaging of the innate immune system particularly focusing on cell trafficking, biodistribution, as well as pharmacokinetics and dynamics of promising immunotherapies in cancer and other diseases; discuss the unmet needs and current challenges in integrating imaging modalities and immunology and suggest potential solutions to overcome these barriers.

A novel microfluidic device capable of maintaining functional thyroid carcinoma specimens ex vivo provides a new drug screening platform

BACKGROUND

Though the management of malignancies has improved vastly in recent years, many treatment options lack the desired efficacy and fail to adequately augment patient morbidity and mortality. It is increasingly clear that patient response to therapy is unique to each individual, necessitating personalised, or 'precision' medical care. This demand extends to thyroid cancer; ~ 10% patients fail to respond to radioiodine treatment due to loss of phenotypic differentiation, exposing the patient to unnecessary ionising radiation, as well as delaying treatment with alternative therapies.

METHODS

Human thyroid tissue (n = 23, malignant and benign) was live-sliced (5 mm diameter × 350-500 μm thickness) then analysed or incorporated into a microfluidic culture device for 96 h (37 °C). Successful maintenance of tissue was verified by histological (H&E), flow cytometric propidium iodide or trypan blue uptake, immunohistochemical (Ki67 detection/ BrdU incorporation) and functional analysis (thyroxine [T4] output) in addition to analysis of culture effluent for the cell death markers lactate dehydrogenase (LDH) and dead-cell protease (DCP). Apoptosis was investigated by Terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL). Differentiation was assessed by evaluation of thyroid transcription factor (TTF1) and sodium iodide symporter (NIS) expression (western blotting).

RESULTS

Maintenance of gross tissue architecture was observed. Analysis of dissociated primary thyroid cells using flow cytometry both prior to and post culture demonstrated no significant change in the proportion of viable cells. LDH and DCP release from on-chip thyroid tissue indicated that after an initial raised level of release, signifying cellular damage, detectable levels dropped markedly. A significant increase in apoptosis (p < 0.01) was observed after tissue was perfused with etoposide and JNK inhibitor, but not in control tissue incubated for the same time period. No significant difference in Ki-67 positivity or TTF1/NIS expression was detected between fresh and post-culture thyroid tissue samples, moreover BrdU positive nuclei indicated on-chip cellular proliferation. Cultured thyroid explants were functionally viable as determined by production of T4 throughout the culture period.

CONCLUSIONS

The described microfluidic platform can maintain the viability of thyroid tissue slices ex vivo for a minimum of four days, providing a platform for the assessment of thyroid tissue radioiodine sensitivity/adjuvant therapies in real time.

Expression and correlation of sodium/iodide symporter and thyroid stimulating hormone receptor in human thyroid carcinoma

Aims

To investigate the expression of sodium/iodide symporter (NIS) and thyroid stimulating hormone receptor (TSHR) in human thyroid cancer.

Patients and methods

NIS and TSHR mRNA levels quantified by real-time PCR as well as NIS and TSHR proteins evaluated by immunohistochemistry were examined in surgical specimens including 38 benign nodules, 32 thyroid carcinomas and 36 normal thyroid samples.

Results

NIS and TSHR mRNA levels in thyroid carcinomas were significantly lower than in benign nodules and normal thyroid samples (P <0.001). Interestingly, we found that NIS and TSHR mRNA expression in benign nodules had similar levels to those in normal thyroid tissues. However, NIS and TSHR protein expression in benign nodules and thyroid carcinomas was stronger than in normal thyroid samples (P <0.05) but mainly located in cytoplasm. In addition, there was a significant positive correlation between NIS and TSHR in benign nodules and normal thyroid samples (r = 0.551 and 0.667, respectively, P = 0.001 and 0.000, respectively) but there was no such correlation in thyroid carcinomas (r = 0.222, P = 0.376).

Conclusions

In thyroid carcinomas, NIS and TSHR mRNA levels were lower but the proteins were overexpressed. The NIS protein mainly locates in the cytoplasm, which therefore lacks the ability of transporting and absorbing iodine in patients with thyroid carcinoma. In addition, there was no correlation between NIS and TSHR in thyroid cancer, which may explain why, even after TSH stimulation, 10–20% of these malignant tumors are unable to concentrate enough radioiodine for effective therapy.

NIS expression in thyroid tumors, relation with prognosis clinicopathological and molecular features

Thyroid cancer therapy is based on surgery followed by radioiodine treatment. The incorporation of radioiodine by cancer cells is mediated by sodium iodide symporter (NIS) (codified by the SLC5A5 gene), that is functional only when targeted to the cell membrane. We aimed to evaluate if NIS expression in thyroid primary tumors would be helpful in predicting tumor behavior, response to therapy and prognosis. NIS expression was addressed by qPCR and immunohistochemistry. In order to validate our data, we also studied SLC5A5 expression on 378 primary papillary thyroid carcinomas from The Cancer Genome Atlas (TCGA) database. In our series, SLC5A5 expression was lower in carcinomas with vascular invasion and with extrathyroidal extension and in those harboring BRAFV600E mutation. Analysis of SLC5A5 expression from TCGA database confirmed our results. Furthermore, it showed that larger tumors, with locoregional recurrences and/or distant metastases or harboring RAS, BRAF and/or TERT promoter (TERTp) mutations presented significantly less SLC5A5 expression. Regarding immunohistochemistry, 12/211 of the cases demonstrated NIS in the membrane of tumor cells, those cases showed variable outcomes concerning therapy success, prognosis and all but one were wild type for BRAF, NRAS and TERTp mutations. SLC5A5 mRNA lower expression is associated with features of aggressiveness and with key genetic alterations involving BRAF, RAS and TERTp. Mutations in these genes seem to decrease protein expression and its targeting to the cell membrane. SLC5A5 mRNA expression is more informative than NIS immunohistochemical expression regarding tumor aggressiveness and prognostic features.

Targeting the TSH receptor in thyroid cancer

Recent advances in the arena of theranostics have necessitated a re-examining of previously established fields. The existing paradigm of therapeutic thyroid-stimulating hormone receptor (TSHR) targeting in the post-surgical management of differentiated thyroid cancer using levothyroxine and recombinant human thyroid-stimulating hormone (TSH) is well understood. However, in an era of personalized medicine, and with an increasing awareness of the risk profile of longstanding pharmacological hyperthyroidism, it is imperative clinicians understand the molecular basis and magnitude of benefit for individual patients. Furthermore, TSHR has been recently re-conceived as a selective target for residual metastatic thyroid cancer, with pilot data demonstrating effective targeting of nanoparticles to thyroid cancers using this receptor as a target. This review examines the evidence for TSHR signaling as an oncogenic pathway and assesses the evidence for ongoing TSHR expression in thyroid cancer metastases. Priorities for further research are highlighted.

The Thyroid Na+/I- Symporter: Molecular Characterization and Genomic Regulation

Iodide (I-) is an essential constituent of the thyroid hormones triiodothyronine (T₃) and thyroxine (T₄), and the iodide concentrating mechanism of the thyroid gland is essential for the synthesis of these hormones. In addition, differential uptake of iodine isotopes (radioiodine) is a key modality for the diagnosis and therapy of thyroid cancer. The sodium dependent iodide transport activity of the thyroid gland is mainly attributed to the functional expression of the Na+/I- Symporter (NIS) localized at the basolateral membrane of thyrocytes. In this paper, we review and summarize current data on molecular characterization, on structure and function of NIS protein, as well as on the transcriptional regulation of NIS encoding gene in the thyroid gland. We also propose that a better and more precise understanding of NIS gene regulation at the molecular level in both healthy and malignant thyroid cells may lead to the identification of small molecule candidates. These could then be translated into clinical practice for better induction and more effective modulation of radioiodine uptake in dedifferentiated thyroid cancer cells and in their distant metastatic lesions.

Comparison of 18F-fluorodeoxyglucose uptake with the expressions of glucose transporter type 1 and Na+/I- symporter in patients with untreated papillary thyroid carcinoma

PURPOSE

Discrepancies between the uptakes of (18)F-fluorodeoxyglucose ((18)F-FDG) and (131)I in papillary thyroid carcinoma have been reported. We compared 18F-FDG uptake with the expressions of glucose transporter type 1 (GLUT1) and sodium-iodide symporter (NIS) in untreated papillary thyroid carcinoma.

MATERIALS AND METHODS

A total of 33 consecutive patients (male:female = 12:21; mean age, 46.6 ± 13.0 years) with initially diagnosed papillary thyroid carcinoma were prospectively included in the study. All subjects underwent preoperative (18)F-FDG positron emission tomography/computerized tomography scans followed by surgery. The expressions of GLUT1 and NIS were evaluated in resected primary tumors and metastatic lymph nodes by immunohistochemical staining and were compared with the maximum standard uptake value of each lesion, respectively.

RESULTS

None of the 40 primary tumors showed significant expressions of GLUT1. Significant expressions of NIS were found in 14 primary tumors (35.0%). Among 36 metastatic lymph nodes, only 1 showed GLUT1 expression. Significant expression of NIS was found in 13 (36.1%) metastatic nodes. The maximum standard uptake value of both primary tumors and metastatic nodes with negative expression of NIS was significantly higher than those with a positive expression of NIS (10.6 ± 10.8 vs. 4.9 ± 5.2, p = 0.011).

CONCLUSIONS

The 18F-FDG uptake of untreated papillary thyroid carcinoma has an inverse correlation with NIS expression. However, GLUT1 expression does not appear to be associated with 18F-FDG uptake in untreated papillary thyroid carcinoma.

Subcellular distribution of the sodium iodide symporter in benign and malignant thyroid tissues

BACKGROUND

Membranous expression of the sodium iodide symporter (NIS) is a prerequisite for iodide uptake in thyrocytes. Previous studies reported heterogeneous results on the relative frequency of staining in various pathological conditions of the thyroid. The present study aimed at determining membranous staining by using confocal laser microscopy in benign and malignant thyroid diseases, complemented in a subgroup of patients with recurrent or metastatic disease with functional findings of radioiodine uptake (RIU).

METHODS

There were 380 malignant thyroid tumors (145 papillary, 51 follicular, 87 Hurthle cell, and 97 undifferentiated thyroid carcinomas [UTC]), 115 benign adenomas, 62 diffuse goiters, 89 inflammatory conditions (Graves', Hashimoto, Thyroiditis deQuervain, and lymphocytic thyroiditis), and 179 normal tissues (NT, fetal, and adult). These were subjected to NIS (two different antibodies) and thyroglobulin (TG) staining and evaluated by confocal microscopy.

RESULTS

In a subgroup of 50 samples from patients with recurrent or metastatic disease, NIS staining was correlated with the RIU. As compared with NT, Graves' patients had significantly higher positive NIS membrane staining (>97% vs. 69%) whereas patients with Hashimoto, lymphocytic thyroiditis but also benign adenomas scored lower than NT (56.7% and 55.8% vs. 69%). Depending on their differentiation NIS staining was significantly lower in thyroid carcinomas in parallel with TG staining with only 1/97 UTCs being positive. RIU was more frequently detectable than NIS staining.

CONCLUSION

Confocal staining strictly evaluating only membranous expression of NIS has not used on a large scale before this study. We confirm the loss of membranous NIS in benign but more prominently in malignant thyroid tumors. NIS staining of diagnostic tissues cannot be used to predict RIU.

Induction of sodium/iodide symporter (NIS) expression and radioiodine uptake in non-thyroid cancer cells

BACKGROUND

This study was designed to explore the therapeutic potential of suppressing MAP kinase and PI3K/Akt pathways and histone deacetylase (HDAC) to induce the expression of sodium/iodide symporter (NIS) and radioiodine uptake in non-thyroid cancer cells.

METHODS

We tested the effects of the MEK inhibitor RDEA119, the Akt inhibitor perifosine, and the HDAC inhibitor SAHA on NIS expression in thirteen human cancer cell lines derived from melanoma, hepatic carcinoma, gastric carcinoma, colon carcinoma, breast carcinoma, and brain cancers. We also examined radioiodine uptake and histone acetylation at the NIS promoter in selected cells.

RESULTS

Overall, the three inhibitors could induce NIS expression, to various extents, in melanoma and all the epithelial carcinoma-derived cells but not in brain cancer-derived cells. SAHA was most effective and its effect could be significantly enhanced by RDEA119 and perifosine. The expression of NIS, at both mRNA and protein levels, was most robust in the melanoma cell M14, hepatic carcinoma cell HepG2, and the gastric carcinoma cell MKN-7 cell. Radioiodine uptake was correspondingly induced, accompanied by robust increase in histone acetylation at the NIS promoter, in these cells when treated with the three inhibitors.

CONCLUSIONS

This is the first demonstration that simultaneously suppressing the MAP kinase and PI3K/Akt pathways and HDAC could induce robust NIS expression and radioiodine uptake in certain non-thyroid human cancer cells, providing novel therapeutic implications for adjunct radioiodine treatment of these cancers.

The biology of the sodium iodide symporter and its potential for targeted gene delivery

The sodium iodide symporter (NIS) is responsible for thyroidal, salivary, gastric, intestinal and mammary iodide uptake. It was first cloned from the rat in 1996 and shortly thereafter from human and mouse tissue. In the intervening years, we have learned a great deal about the biology of NIS. Detailed knowledge of its genomic structure, transcriptional and post-transcriptional regulation and pharmacological modulation has underpinned the selection of NIS as an exciting approach for targeted gene delivery. A number of in vitro and in vivo studies have demonstrated the potential of using NIS gene therapy as a means of delivering highly conformal radiation doses selectively to tumours. This strategy is particularly attractive because it can be used with both diagnostic (99mTc, 125I, 124I)) and therapeutic (131I, 186Re, 188Re, 211At) radioisotopes and it lends itself to incorporation with standard treatment modalities, such as radiotherapy or chemoradiotherapy. In this article, we review the biology of NIS and discuss its development for gene therapy.

Determinants of thyroid autoantibody production in Hashimoto's thyroiditis

Hashimoto's thyroiditis (HT) is the most prevalent thyroid autoimmune disorder, characterized by the presence of specific thyroid autoantibodies (TAb). The development of autoimmunity, including TAb production and clinical presentation of HT, is determined by a complex interplay of genetic susceptibility and several endogenous and environmental factors, which are discussed in this article. During the progression of the disease, TAb production precedes clinical manifestations, although the correlation between TAb concentrations and thyroid function is weak. We do not treat euthyroid HT patients despite elevated TAb; while in hypothyroidism, replacement therapy with l-thyroxine is required. Until now, an effective approach to prevent TAb production and the development of clinical disease has not yet been established. However, further identification of risk factors and their interaction may help in the prevention of thyroid autoimmunity.

Analysis of thyroglobulin gene polymorphisms in patients with autoimmune thyroiditis

The autoimmune thyroid disease is a complex disorder caused by a combination of genetic susceptibility and environmental factors, which are believed to initiate the autoimmune response to thyroid antigens. Identification of the susceptibility genes has found that unique and diverse genetic factors are in association with Graves' disease and autoimmune thyroiditis. The thyroglobulin gene is an identified thyroid-specific gene associated to autoimmune thyroid disease and, principally, with autoimmune thyroiditis. The aim of this work was to test for evidence of allelic association between autoimmune thyroiditis and thyroglobulin polymorphism markers. We studied six polymorphisms distributed throughout all the thyroglobulin gene: four microsatellites (Tgms1, Tgms2, TGrI29 and TGrI30), one insertion/deletion (Indel) polymorphism (IndelTG-IVS18) and one exonic single nucleotide polymorphism (SNP) (c.7589G>A) in 122 patients with autoimmune thyroiditis compared with 100 non-related normal subjects. No differences in allele and genotype distribution were observed between autoimmune thyroiditis cases and controls for Tgms1, Tgms2, TGrI30, IndelTG-IVS18 and c.7589G>A. However, when we analyzed the patients with the TGrI29 microsatellite we found a significant association between the 199-bp allele and AT (33.7% vs. 24.5% in control group) (P = 0.0372). In addition, a higher prevalence of the 201-bp allele has been observed in control subjects (47.5% vs. 38.1% in patients group), although not statistically significant (P = 0.0536). Our work shows the association between the thyroglobulin gene and autoimmune thyroiditis and reinforce that thyroglobulin is a thyroid-specific susceptibility gene for this disease.

A novel mechanism of sodium iodide symporter repression in differentiated thyroid cancer

Differentiated thyroid cancers and their metastases frequently exhibit reduced iodide uptake, impacting on the efficacy of radioiodine ablation therapy. PTTG binding factor (PBF) is a proto-oncogene implicated in the pathogenesis of thyroid cancer. We recently reported that PBF inhibits iodide uptake, and have now elucidated a mechanism by which PBF directly modulates sodium iodide symporter (NIS) activity in vitro. In subcellular localisation studies, PBF overexpression resulted in the redistribution of NIS from the plasma membrane into intracellular vesicles, where it colocalised with the tetraspanin CD63. Cell-surface biotinylation assays confirmed a reduction in plasma membrane NIS expression following PBF transfection compared with vector-only treatment. Coimmunoprecipitation and GST-pull-down experiments demonstrated a direct interaction between NIS and PBF, the functional consequence of which was assessed using iodide-uptake studies in rat thyroid FRTL-5 cells. PBF repressed iodide uptake, whereas three deletion mutants, which did not localise within intracellular vesicles, lost the ability to inhibit NIS activity. In summary, we present an entirely novel mechanism by which the proto-oncogene PBF binds NIS and alters its subcellular localisation, thereby regulating its ability to uptake iodide. Given that PBF is overexpressed in thyroid cancer, these findings have profound implications for thyroid cancer ablation using radioiodine.

Reciprocal immunohistochemical expression of sodium/iodide symporter and hexokinase I in primary thyroid tumors with synchronous cervical metastasis

OBJECTIVES/HYPOTHESIS

Sodium/iodide symporter (NIS) is a glycoprotein which is related to the concentration of radioiodine in thyroid cancer. Glucose transporter-1 (Glut-1) and hexokinases (HK) are glycoproteins related to glucose metabolism (i.e., uptake and phosphorylation) in various cancers. The aim of this study was to determine the immunohistochemical patterns of expression and mutual relationships between NIS, Glut-1, HK I, and HK II in primary thyroid tumors and synchronous cervical metastatic tumors.

STUDY DESIGN

Retrospective experimental study.

METHODS

Nine cases of follicular carcinomas, sixteen cases of papillary carcinomas, and four cases of anaplastic carcinomas were included. The immunohistochemical staining intensities were categorized (scored) as negative (0), weak (1), positive (2), or strongly positive (3) and dichotomized as a negative/weak (scores 0 or 1) or positive expression (scores 2 or 3).

RESULTS

NIS had a positive expression in good prognostic types of thyroid carcinomas, such as follicular carcinomas, more often, while having a positive expression in poor prognostic types of thyroid carcinomas, such as anaplastic carcinomas (P = .033) less often; HK I had the opposite pattern of expression (P = .033). Primary thyroid tumors and corresponding synchronous cervical metastatic tumors had a similar pattern of expression for NIS, HK I, and HK II. NIS had a reciprocal relationship with HK I as compared to Glut-1 with respect to staining intensity on each primary tumor (P = .040).

CONCLUSION

Reciprocal staining pattern of NIS and HK I on primary tumors is related to the staining pattern of NIS and HK I on synchronous as well as occult cervical metastatic tumors.

Radiation-mediated up-regulation of gene expression from replication-defective adenoviral vectors: implications for sodium iodide symporter gene therapy

PURPOSE

To assess the effects of external beam radiotherapy (EBRT) on adenoviral-mediated transgene expression in vitro and in vivo and to define an optimal strategy for combining sodium iodide symporter (NIS)-mediated (131)I therapy with EBRT.

EXPERIMENTAL DESIGN

Expression of reporter genes [NIS, green fluorescent protein (GFP), beta-galactosidase (lacZ), and luciferase (Luc)] from replication-deficient adenoviruses was assessed in tumor cell lines under basal conditions and following irradiation. The effects of viral multiplicity of infection (MOI) and EBRT dose on the magnitude and duration of gene expression were determined. In vivo studies were done with Ad-CMV-GFP and Ad-RSV-Luc.

RESULTS

EBRT increased NIS, GFP, and beta-galactosidase expression in colorectal, head and neck, and lung cancer cells. Radiation dose and MOI were important determinants of response to EBRT, with greatest effects at higher EBRT doses and lower MOIs. Radiation exerted both transductional (through increased coxsackie-adenoviral receptor and integrin alpha(v)) and nontransductional effects, irrespective of promoter sequence (CMV, RSV, hTR, or hTERT). Analysis of the schedule of EBRT followed by viral infection revealed maximal transduction at 24 hours. Radiation maintained increasing radioiodide uptake from Ad-hTR-NIS over 6 days, in direct contrast to reducing levels in unirradiated cells. The effects of EBRT in increasing and maintaining adenovirus-mediated transgene expression were also seen in vivo using GFP- and luciferase-expressing adenoviral vectors.

CONCLUSIONS

Radiation increased the magnitude and duration of NIS gene expression from replication-deficient adenoviruses. The transductional effect is maximal at 24 hours, but radioiodide uptake is maintained at an elevated level over 6 days after infection.

NIS mRNA expression level in resected thyroid tissue as a marker of postoperative hypothyroidism after subtotal thyroidectomy in patients with Graves' disease

Subtotal thyroidectomy for Graves' disease sometimes leads to hypothyroidism or relapse during long-term follow-up in a significant proportion of patients. Factors predictive of postoperative hypothyroidism after subtotal thyroidectomy are not known. The objective of this study was to determine the relation between clinical features and expression of transcripts associated with thyroid hormone synthesis in resected thyroid tissues of patients with Graves' disease. Thyroid tissues were obtained from 65 patients with Graves' disease who underwent subtotal thyroidectomy. Expression of mRNAs from thyroglobulin (Tg), TSH receptor (TSHR), thyroid peroxidase (TPO), sodium/iodide symporter (NIS), and the Pendred's syndrome (PDS) genes were analyzed by quantitative reverse transcription-polymerase chain reaction. Uni- and multivariate analyses were performed to identify for postoperative hypothyroidism. We detected significant correlations between the NIS mRNA level and levels of free T(3) (fT(3)) and free T(4) (fT(4)) and between the Tg mRNA level and goiter weight before initial drug treatment. Mean levels of expression of all five mRNAs were significantly higher in patients who did not require L-thyroxine replacement therapy than in those who required replacement therapy at 6 months after surgery. In patients who did not require replacement therapy, a significant correlation was found between NIS mRNA expression and fT(4) levels. Univariate analysis revealed that decreased NIS mRNA expression (NIS/PGK<1.69) and low TBII levels before initial treatment were significant of postoperative hypothyroidism. Multivariate analysis showed decreased expression of NIS mRNA (NIS/PGK<1.69) to be an independent risk factor for L-thyroxine replacement after surgery (risk ratio, 3.26, confidence interval, 1.36-9.08, p<0.01). NIS expression reflects the level of thyroid hormone synthesis in Graves' disease patients. Evaluation of NIS mRNA expression in thyroid tissues may help determine prognoses of Graves' disease patients, and therefore an appropriate treatment can be determined for each patient.

Molecular characteristics in papillary thyroid cancers (PTCs) with no 131I uptake

OBJECTIVE

Papillary thyroid cancers (PTCs) with no iodine uptake have an aggressive behaviour and a poor prognosis. The aim of our study was to characterize, at molecular level, a subset of PTC with no 131 iodine ((131)I) uptake.

DESIGN AND METHODS

Forty-eight cancer tissues were divided into three groups: Group 1, 28 primary cancers; Group 2, 7 recurrences capable of trapping (131)I; and Group 3, 13 recurrences incapable of trapping (131)I. mRNA levels of thyroid genes (sodium/iodide symporter NIS, thyroglobulin, thyroperoxidase and pendrin) and glycolytic metabolism genes (GLUT-1, hexokinase I and II) and BRAF mutations were evaluated in the different groups.

RESULTS

Cancers with no (131)I uptake had slightly reduced NIS, significantly reduced thyroglobulin (P < 0.01), thyroperoxidase (P = 0.01) and pendrin (P = 0.03) and significantly increased GLUT-1 (P = 0.01) gene expression levels; and a high frequency of BRAF mutations (77%). BRAF(V600E) mutation, in both primary and metastatic thyroid cancers, is associated with a marked drop in thyroperoxidase (29-fold) and pendrin (20-fold) expression and a considerable increase (five-fold) in GLUT-1 expression.

CONCLUSIONS

(1) The loss of (131)I uptake in recurrences depends not only on a decrease in NIS gene, but possibly on a reduction in the molecules regulating its intracellular metabolism; (2) the high GLUT-1 gene expression supports the use of positron emission tomography with specific tracers in clinical management of such cancers; and (3) BRAF(V600E) point mutations may lead to less differentiated phenotypes, suggesting a worse prognosis.

Distribution of Na+/I- symporter in thyroid cancers in an iodine-deficient population: an immunohistochemical study

BACKGROUND

There are significant differences in the prevalence and behavior of differentiated thyroid cancers (DTC) in the iodine-deficient areas (IDA) and iodine-sufficient areas (ISA) of the world. The sodium iodide symporter (NIS), mediates active transport of iodide across the basolateral aspect of the thyroid follicular cell. However, no study had specifically addressed the issue of expression of sodium iodide symporter (NIS) in thyroid cancer specimens from IDA. The aim of the present study was to find an expression pattern of NIS in DTC in an iodine-deficient population, and to correlate it with histological subtypes, i.e., papillary carcinoma (PTC), follicular carcinoma (FTC), poorly differentiated carcinoma (PDTC), as well as with clinicopathological risk factors and iodine ((131)I) uptake by distant metastases.

METHODS

Immunohistochemistry was carried out in 39 cases of thyroid cancer (41 samples) including PTC (15), FTC (10), PDTC (9), anaplastic cancer (5), and resected metastases (2). Expression was correlated with the patient's age, sex, tumor size, presence or absence of extrathyroidal invasion, distant and lymph node metastases, and whole body radioiodine scan.

RESULTS

Overall, 61.8% of DTC patients showed NIS expression. There was no significant difference in expression rate between PTC (73.3%) and FTC (70.0%). However, expression was significantly less in PDTC (33.3%). There was no correlation between NIS expression and any clinicopathological risk factor (p > .05). The results of NIS expression were not concordant with (131)I uptake by metastases in 4 of 10 cases. (131)I uptake was absent in one case despite the finding that a metastatic site itself showed NIS expression in that case, whereas in the remaining 9 cases (131)I uptake was present although three cases did not show NIS expression.

CONCLUSIONS

In our experience, overall expression of NIS was comparable to other studies from ISA. We conclude that expression may not accurately predict radioactive iodine (RAI) uptake by metastases.

Defects in iodide metabolism in thyroid cancer and implications for the follow-up and treatment of patients

The two major steps of iodine metabolism--uptake and organification--are altered in thyroid cancer tissues. Organification defects result in a rapid discharge of radioiodine from thyroid cells, a short effective half-life of iodine, and a low rate of thyroid hormone synthesis. These defects are mainly due to decreased expression of functional genes encoding the sodium-iodide symporter and thyroid peroxidase and could result in a low radiation dose to thyroid cancer cells. TSH stimulation that is achieved with injections of recombinant human TSH, or long-term withdrawal of thyroid hormone treatment increases iodine-131 uptake in two-thirds of patients with metastatic disease and increases thyroglobulin production in all patients with metastases, even in the absence of detectable uptake. Serum thyroglobulin determination obtained following TSH stimulation and neck ultrasonography is the most sensitive combination for the detection of small tumor foci. Radioiodine treatment is effective when a high radiation dose can be delivered (in patients with high uptake and retention of radioiodine) and when tumor foci are sensitive to the effects of radiation therapy (younger patients, with a well-differentiated tumor and/or with small metastases). The other patients rarely respond to radioiodine treatment, and when progression occurs, other treatment modalities should be considered. Novel strategies are currently being explored to restore iodine uptake in cancer cells that are unable to concentrate radioiodine.

PTTG and PBF repress the human sodium iodide symporter

The ability of the thyroid to accumulate iodide provides the basis for radioiodine ablation of differentiated thyroid cancers and their metastases. Most thyroid tumours exhibit reduced iodide uptake, although the mechanisms accounting for this remain poorly understood. Pituitary tumour transforming gene (PTTG) is a proto-oncogene implicated in the pathogenesis of thyroid tumours. We now show that PTTG and its binding factor PBF repress expression of sodium iodide symporter (NIS) messenger RNA (mRNA), and inhibit iodide uptake. This process is mediated at least in part through fibroblast growth factor-2. In detailed studies of the NIS promoter in rat FRTL-5 cells, PTTG and PBF demonstrated specific inhibition of promoter activity via the human upstream enhancer element (hNUE). Within this approximately 1 kb element, a complex PAX8-upstream stimulating factor 1 (USF1) response element proved critical both to basal promoter activity and to PTTG and PBF repression of NIS. In particular, repression by PTTG was contingent upon the USF1, but not the PAX8, site. Finally, in human primary thyroid cells, PTTG and PBF similarly repressed the NIS promoter via hNUE. Taken together, our data suggest that the reported overexpression of PTTG and PBF in differentiated thyroid cancer has profound implications for activity of the NIS gene, and hence significantly impacts upon the efficacy of radioiodine treatment.

Papillary thyroid carcinoma with lymph node metastases

Papillary thyroid cancer (PTC) is the most frequently occurring human thyroid cancer with good prognosis following appropriate treatment. Lymph node (LN) metastases are the main way through which PTC spread cancer cells. The mechanisms underlying PTC with local invasion, LN metastases and distant metastases are not well investigated. Tumor secrete cytokines, such as vascular endothelial growth factor (VEGF)-C and -D bind to VEGF receptors on lymphatic endothelial cells and induce proliferation (budding) from nearby lymphatic capillaries and growth of new lymphatic capillaries. About one-third of patients can be diagnosed at the time of surgical findings. Different image studies, such as ultrasonography with fine needle aspiration cytology, scintigraphic localization and positron emission tomography were reported to detect LN metastases. Important factors in predicting LN metastases are vascular invasion, male gender, absence of tumor capsule, and perithyroid involvement. Tumor recurrence in LN after primary treatment of PTC had an independent and highly significant negative effect on survival in patients over 45 year-old. Recombinant adeno-associated virus-mediated gene transfer of sVEGFR3-Fc is a feasible therapeutic scheme for blocking lymphogenous metastasis. In conclusion, aggressive surgical procedures performed by experienced surgeons or postoperative radioactive iodine therapy to minimize local recurrence of LN for PTC patients with high risk.

Relationship of sodium/iodide symporter expression with I131 whole body scan uptake between primary and metastatic lymph node papillary thyroid carcinomas

The aim of the present study was to evaluate total and membranous Na+/I- symporter (NIS) expressions in papillary thyroid carcinoma (PTC) tissue, correlation of NIS expression between primary and metastatic lymph node (LN) PTC tissues, and relationship of NIS expression with I131 whole body scan (WBS) uptake between primary and metastatic LN PTC tissues by analyzing 17 pairs of primary and metastatic LN PTC tissues. Staining positivity was calculated, and staining intensity was graded as negative (0), weak (1+), moderate (2+) and strong (3+). In primary PTC tissues, positivities and intensities of normal cells were higher than those of carcinoma cells but had no correlation with those in matched metastatic LN PTC tissues. In classic type, positivities, intensities and membranous intensities (mIS) were correlated between primary and matched metastatic LN PTC tissues. In patients aged younger than 45 yr, positivities and intensities in primary PTC tissues had correlation with those in matched metastatic LN PTC tissues. Positivities, intensities, mIS and pathological subtype of carcinoma cells in primary PTC tissues were not correlated with age, tumor size, TNM stage, MACIS score and thyroglobulin (Tg) levels at the time of I131 WBS. Sensitivity, specificity, as well as positive and negative predicted values of mIS in patients with I131 WBS uptake were 69.2, 75, 90 and 42.9% in primary PTC tissues, and 92.3, 100, 100 and 80% in metastatic LN PTC tissues. The results of mIS taken either as positive or negative were correlated with those of I131 WBS after controlling for age. Our results demonstrate that PTC tissues have altered total and membranous NIS expressions, suggesting that NIS expression in primary PTC tissues may predict NIS expression and I131 WBS uptake in matched metastatic LN PTC tissues.

Decreased type 1 iodothyronine deiodinase expression might be an early and discrete event in thyroid cell dedifferentation towards papillary carcinoma

OBJECTIVE

Type I iodothyronine deiodinase (D1) catalyses the 5' monodeiodination of T4 and is highly expressed in normal human thyroid gland. We have investigated D1 expression in a series of benign and malignant differentiated thyroid neoplasias.

DESIGN

Surgically isolated thyroid tumour fragments were used. D1 expression was determined by reverse transcription polymerase chain reaction (RT-PCR) and enzymatic assay.

PATIENTS

Tumours and adjacent normal tissues were obtained from 28 unselected patients (papillary carcinoma, n = 14; follicular adenoma, n = 7; follicular carcinoma, n = 6; anaplastic carcinoma, n = 1).

MEASUREMENTS

D1 mRNA levels were determined using specific primers for the human D1 gene and enzymatic assays were performed using T4 as substrate.

RESULTS

In papillary thyroid carcinoma (PTC), D1 mRNA and activity levels were decreased compared with the surrounding tissue (0.25 +/- 0.24 vs. 1.09 +/- 0.54 arbitrary units (AU), P < 0.001 and 0.08 +/- 0.07 vs. 0.24 +/- 0.15 pmol T4/min/mg protein, P = 0.045, respectively). Decreased D1 expression was consistent and was observed in all histological subtypes and clinical stages analysed, including microcarcinomas. By contrast, significantly higher D1 mRNA levels and enzyme activity were present in follicular adenoma (1.9 +/- 1.5 vs. 0.83 +/- 0.58 AU, P = 0.028 and 2.67 +/- 1.42 vs. 0.22 +/- 0.06 pmol T4/min/mg protein, P = 0.044, respectively) and in follicular thyroid carcinoma (FTC) than in surrounding normal tissue (1.2 +/- 0.46 vs. 0.67 +/- 0.18 AU, P = 0.038 and 1.20 +/- 0.58 vs. 0.20 +/- 0.10 pmol T4/min/mg protein, P < 0.001, respectively). Type II iodothyronine deiodinase (D2) activity was also significantly higher in metastatic FTC samples than in normal thyroid tissues (5.20 +/- 0.81 vs. 0.30 +/- 0.27 fmol T4/min/mg protein, P < 0.001).

CONCLUSIONS

These findings suggest that thyroid cell dedifferentiation promotes changes in D1 gene expression by pretranscriptional mechanisms and indicate that decreased D1 expression might be an early and discrete event in thyroid cell dedifferentiation towards papillary thyroid carcinoma.

Evidence for transcriptional and posttranscriptional alterations of the sodium/iodide symporter expression in hypofunctioning benign and malignant thyroid tumors

The uptake of iodide by epithelial thyroid cells requires the expression of a specific transporter, the Na(+)/I(-) symporter, NIS. Benign and malignant thyroid tumors of epithelial origin show a decrease up to a loss of iodide uptake activity. Previous studies of the human NIS (hNIS) gene expression in these tumors, based on the amplification of transcripts and/or immunohistochemical detection of the protein, have yielded divergent data; hNIS expression was found either increased or decreased. To get a new and integrated view of the alterations of hNIS expression in hypofunctioning thyroid tumors, we performed investigations of hNIS transcript and hNIS protein levels on the same tumors and paired normal tissue samples. HNIS, identified as a 75- to 80-kd species, was present in all normal tissue samples from euthyroid patients, but was undetectable, even at high membrane protein input, in all benign and malignant hypofunctioning thyroid tumors. By contrast, approximately 50% of tumors contained hNIS transcripts. This dissociation between transcript and protein levels was not found for the transcript and protein encoded by the PDS gene assayed in the same tumors. The hNIS transcript-positive tumors contained small amounts of low-molecular mass hNIS-immunoreactive species identified as nonglycosylated hNIS. Tumors containing the nonmature form of hNIS exhibited a predominant intracellular immunolabeling. In conclusion, our data show that benign and malignant hypofunctioning thyroid tumors either no longer express hNIS protein or express only a very low amount of nonglycosylated hNIS and indicate that the impairment of hNIS gene expression might result from alterations at both transcriptional and posttranscriptional levels.

Expression of the apical iodide transporter in human thyroid tissues: a comparison study with other iodide transporters

Iodide transport by thyrocytes involves two transporters, namely the Na(+)/I (-) symporter located at the basolateral pole and possibly pendrin in the apical membranes of the cell. Recently, we identified a human gene and its protein product, designated hAIT, as a putative new transporter involved in iodide transfer across the apical membrane of thyrocytes. In the present report, we analyzed both hAIT gene and protein expressions in a large series of benign and malignant human thyroid tissues. Using immunohistochemistry, hAIT staining was detected in normal thyroid tissue in about 10% of follicles; in positive follicles, 10-40% of thyrocytes, mostly the tall cells, were stained. In thyroid tissues obtained from patients with Graves' disease and toxic adenomas, hAIT mRNA and protein levels were similar to those found in normal tissue. In hypofunctioning adenomas, hAIT mRNA levels were slightly decreased, and apical iodide transporter (AIT) immunostaining was similar to that observed in normal thyroid tissue. AIT staining was stronger in Hürthle cell adenomas and in microfollicular adenomas. In thyroid carcinomas, the mean and median hAIT mRNA levels were significantly decreased. Expression of AIT protein was undetectable in most papillary carcinomas and was weak but detectable in most follicular carcinomas; it was negative in anaplastic carcinomas.

Advances in Na(+)/I(-) symporter (NIS) research in the thyroid and beyond

The Na(+)/I(-) symporter (NIS) is a plasma membrane glycoprotein that mediates active iodide uptake in the thyroid-the essential first step in thyroid hormone biosynthesis-and in other tissues, such as salivary and lactating mammary glands. Thyroidal radioiodide uptake has been used for over 60 years in the diagnosis and effective treatment of thyroid cancer and other diseases. However, the NIS cDNA was only isolated in 1996 by expression cloning in Xenopus laevis oocytes, marking the beginning of the molecular characterization of NIS and the study of its regulation, both in the thyroid and other tissues. One of the most exciting current areas of NIS research-radioiodide treatment of extrathyroidal cancers-was launched by the discovery of functional expression of endogenous NIS in breast cancer and by the ectopic transfer of the NIS gene into otherwise non NIS-expressing cancers. This review summarizes the main findings in NIS research, emphasizing the most recent developments.

Correlation between the loss of thyroglobulin iodination and the expression of thyroid-specific proteins involved in iodine metabolism in thyroid carcinomas

Progress in biotechnology has provided useful tools for tracing proteins involved in thyroid hormone synthesis in vivo. Mono- or polyclonal antibodies are now available to detect on histological sections the Na(+)/I(-) symporter (NIS) at the basolateral pole of the cell, the putative iodide channel (pendrin) at the apical plasma membrane, thyroperoxidase (TPO), and members of the NADPH-oxidase family, thyroid oxidase 1 and 2 (ThOXs), part of the H(2)O(2)-generating system. The aim of this study was to correlate thyroglobulin (Tg) iodination with the presence of these proteins. Tg, T(4)-containing Tg, NIS, pendrin, TPO, ThOXs, and TSH receptor (TSHr) were detected by immunohistochemistry on tissue sections of normal thyroids and various benign and malignant thyroid disorders. Tg was present in all cases. T(4)-containing Tg was found in the adenomas, except in Hurthle cell adenomas. It was never detected in carcinomas. NIS was reduced in all types of carcinomas, whereas it was detected in noncancerous tissues. Pendrin was not expressed in carcinomas, except in follicular carcinomas, where weak staining persisted. TPO expression was present in insular, follicular carcinomas and in follicular variants of papillary carcinomas, but in a reduced percentage of cells. It was below the level of detection in papillary carcinomas. The H(2)O(2)-generating system, ThOXs, was found in all carcinomas and was even increased in papillary carcinomas. Its staining was apical in normal thyroids, whereas it was cytoplasmic in carcinomas. The TSHr was expressed in all cases, but the intensity of the staining was decreased in insular carcinomas. In conclusion, our work shows that all types of carcinomas lose the capacity to synthesize T(4)-rich, iodinated Tg. In follicular carcinomas, this might be due to a defect in iodide transport at the basolateral pole of the cell. In papillary carcinomas, this defect seems to be coupled to an altered apical transport of iodide and probably TPO activity. The TSHr persists in virtually all cases.

Low expression of sodium iodide symporter identifies aggressive thyroid tumors

A decreased radioiodine uptake is frequently detected in differentiated thyroid carcinomas (DTC) and is associated with high recurrence rate and reduced survival. We investigated the correlation between NIS mRNA expression levels in the primary tumor and patient outcome using a quantitative real-time RT-PCR method. NIS expression was decreased in 17 DTC (21.04+/-39.66 pg Eq) compared to four autoimmune thyroid disease (180.51+/-92.63 pg Eq) and 14 normal tissues (75.71+/-66.98 pg Eq) (p<0.0001). The 17 thyroid differentiated carcinoma patients were submitted to surgery complemented by radioiodine ablation and had at least 24 months of follow-up, under levothyroxine continued suppressive therapy. According to their outcome, we could characterize a group of papillary carcinoma patients with aggressive carcinomas, whose NIS mRNA levels were markedly lower than a group with non-aggressive carcinomas (0.62+/-0.79 versus 54.87+/-53.79; p<0.005). We suggest that the quantification of NIS mRNA relative levels in the primary tumor may predict poor outcome.

Ácido retinóico: uma terapia promissora para carcinoma treoideano desdiferenciado?

Carcinoma tireoideano é a neoplasia endócrina maligna mais freqüente. Aproximadamente 90% dos cânceres não-medulares da tireóide são classificados como diferenciados e apresentam em geral bom prognóstico após tratamento adequado. Entretanto, recidiva tumoral ocorre em cerca de 20 a 40% e perda da diferenciação celular em até 30%. O carcinoma desdiferenciado é caracterizado pela perda da função e propriedades tireóide-específicas e as opções terapêuticas são limitadas e pouco eficazes. Em estudos recentes in vitro, tem sido mostrado que o acido retinóico (AR) pode ser útil em induzir rediferenciação da célula tireoideana, como evidenciado pela maior expressão de tireoglobulina, 5' desiodase tipo I e co-transportador sódio-iodeto, além do incremento da captação de iodo pela célula tumoral. Além dos estudos experimentais, estudos clínicos demonstram efeito benéfico do AR, com aumento da captação de iodo em 40% e regressão tumoral em 20% dos pacientes com carcinoma não captante de iodo submetidos ao tratamento.

The sodium/iodide Symporter (NIS): characterization, regulation, and medical significance

The Na(+)/I(-) symporter (NIS) is an integral plasma membrane glycoprotein that mediates active I(-) transport into the thyroid follicular cells, the first step in thyroid hormone biosynthesis. NIS-mediated thyroidal I(-) transport from the bloodstream to the colloid is a vectorial process made possible by the selective targeting of NIS to the basolateral membrane. NIS also mediates active I(-) transport in other tissues, including salivary glands, gastric mucosa, and lactating mammary gland, in which it translocates I(-) into the milk for thyroid hormone biosynthesis by the nursing newborn. NIS provides the basis for the effective diagnostic and therapeutic management of thyroid cancer and its metastases with radioiodide. NIS research has proceeded at an astounding pace after the 1996 isolation of the rat NIS cDNA, comprising the elucidation of NIS secondary structure and topology, biogenesis and posttranslational modifications, transcriptional and posttranscriptional regulation, electrophysiological analysis, isolation of the human NIS cDNA, and determination of the human NIS genomic organization. Clinically related topics include the analysis of congenital I(-) transport defect-causing NIS mutations and the role of NIS in thyroid cancer. NIS has been transduced into various kinds of cancer cells to render them susceptible to destruction with radioiodide. Most dramatically, the discovery of endogenous NIS expression in more than 80% of human breast cancer samples has raised the possibility that radioiodide may be a valuable novel tool in breast cancer diagnosis and treatment.

Diagnosis of neck recurrences in patients with differentiated thyroid carcinoma

BACKGROUND

The follow-up of patients with differentiated thyroid carcinoma (DTC) is traditionally carried out with (131)I whole body scan ((131)I WBS) and serum thyroglobulin (Tg) measurement. Neck ultrasonography (US) is also used.

METHODS

We compared the roles of Tg measurement (IRMA assay) after l-thyroxine (T4) withdrawal, (131)I WBS, and US in the diagnosis of DTC neck recurrences. Diagnosis of DTC neck recurrences was based on fine-needle aspiration biopsy (FNAB) or on histologic results. Four hundred ninety-four DTC patients (120 males, 374 females; mean age, 49.3 years), submitted to total thyroidectomy and subsequent radioablative (131)I treatment, underwent serum Tg measurement off T4 therapy, (131)I WBS, and neck US at our institution. Mean (+/- SD) follow-up time was 55.1 +/- 37.7 months. Neck DTC recurrences were detected in 51 (10.3%) patients (34 females, 17 males; mean age, 49.5 years).

RESULTS

Neck recurrences occurred after 44.6 +/- 21.4 months from initial treatment. Serum Tg levels increased (> or = 2 ng/mL) off T4 therapy in 29 patients (sensitivity 56.8%), (131)I WBS showed neck uptake in 23 patients (sensitivity 45.1%) and coexisting distant metastases were detected in 9 of 23 patients, and US identified neck recurrence in 48 patients (sensitivity 94.1%). Of these 48 neck recurrences, 19 were found in the laterocervical compartment and 29 in the central neck compartment.

CONCLUSIONS

Traditional techniques for the surveillance of DTC patients are not as sensitive as US in the detection of neck recurrences. Neck US detects recurrences in patients with undetectable serum Tg levels and negative IWBS and should be performed as the first-line test in the follow-up of all DTC patients.

The sodium iodide symporter: its pathophysiological and therapeutic implications

The sodium iodide symporter (NIS) is an intrinsic plasma membrane protein that mediates the active transport of iodide in the thyroid gland and a number of extrathyroidal tissues, in particular lactating mammary gland. Because of its crucial role in the ability of thyroid follicular cells to trap iodide, cloning of NIS opened an exciting and extensive new field of thyroid-related research. Cloning and molecular characterization of NIS allowed investigation of its expression and regulation in thyroidal and nonthyroidal tissues, and its potential pathophysiological and therapeutic implications in benign and malignant thyroid disease. In addition to its key function in thyroid physiology, NIS-mediated iodide accumulation allows diagnostic thyroid scintigraphy as well as effective therapeutic application of radioiodine in benign and malignant thyroid disease. Characterization and application of NIS as a novel therapeutic gene and the presence of high native NIS expression in the majority of breast cancers further suggest a promising role of NIS in diagnosis and therapy of cancer outside the thyroid gland.

A GC box in the human sodium iodide symporter gene promoter is essential for full activity

We previously reported that the human sodium iodide symporter (hNIS) 5'-flanking region between -603 and -415 is essential for full expression. In this study, we further localized sequences within this region required for the basal expression of the hNIS promoter and identified a functional GC box. Activity of the hNIS promoter was assessed by transient transfection of luciferase reporter gene constructs with progressive 5' deletions into the human papillary thyroid cancer cell line BHP 2-7. Deletion from -603 to -535 enhanced promoter activity, further deletion to -469 decreased promoter activity, and deletion to -415 nearly abolished promoter activity. The DNA sequence within this critical 55 bp region from -469 to -415 contains a GC box. Introduction of mutations into the GC box of the deletion constructs -603, -535 and -469 decreased promoter activity in both thyroid cells (BHP 2-7 and rat thyroid cell FRTL-5) and nonthyroid cells (human prostate cancer cell LNCaP-2 and human breast cancer cell MCF-7). The magnitude of reduction for the -603 mutation construct was significantly greater than that for the -469 mutation construct in thyroid cells compared to non-thyroid cells. In vitro transcription using nuclear extracts isolated from HeLa cells was reduced from DNA templates with the GC box mutation and nearly abolished from templates with 5' deletion to -415. Identification of proteins interacting with the GC box was performed by gel retardation assays with or without Sp1 specific antibodies. Sp1 and an "Sp1-like" protein bound to the wild-type GC box sequence but not to the GC box mutant. In summary, the GC box is a positive regulatory element in the hNIS basal promoter.

CTLA-4 and autoimmune thyroid disease: lack of influence of the A49G signal peptide polymorphism on functional recombinant human CTLA-4

A single nucleotide A49G polymorphism (SNP) of CTLA-4 has been linked and associated with the autoimmune thyroid diseases (AITD) and thyroid autoantibody secretion. We have explored the functional mechanisms of CTLA-4 by means of recombinant human CTLA-4 expressed on transfected Jurkat T cells. Analysis of CTLA-4 transcripts with quantitative real-time PCR demonstrated similar baseline and PHA-stimulated levels for both the A49 and G49 alleles, which were markedly enhanced by anti-CTLA-4 engagement. Both alleles also coded for proteins which were expressed on the cell membrane, as measured by FACS analysis using anti-CTLA-4 (G: 34.4+/-11.9% cells, A: 27.6+/-8.6% cells) (p=ns). Baseline and PHA-stimulated IL-2 production were also similar among control and CTLA-4 clones expressing both alleles. After anti-CTLA-4 engagement, IL-2 production was markedly inhibited in a dose- and time-dependent manner but this also appeared to be similar in the A and G allele expressing cells (95.7+/-1.2% inhibition and 94.9+/-1.1% inhibition, respectively). In conclusion, both the extrinsic and intrinsic actions of human CTLA-4 were not affected by the signal peptide A49G polymorphism. Therefore, the linkage of the CTLA-4 A49G SNP to AITD is most likely secondary to linkage disequilibrium.

Correlation between 99mTc-pertechnetate uptakes and expressions of human sodium iodide symporter gene in breast tumor tissues

We investigated a correlation between the expression of human sodium iodide symporter (hNIS) mRNA and the uptake of 99mTc-pertechnetate in 25 breast tumors. 99mTc-pertechnetate scintigraphy revealed positive uptake in 4 patients. The normalized mRNA expression of hNIS was higher in tumors with positive uptake on the scintigraphy (n=4, median 0.97, range 0.78-1.27) than that in negative uptake tumors (n=21, median 0.46, range 0.10-1.03, p < 0.005). 99mTc-pertechnetate uptake is correlated with the hNIS expression in the breast tumor.

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.

Expression of the sodium iodide symporter and thyroglobulin genes are reduced in papillary thyroid cancer

Altered expression of the gene encoding the sodium iodine symporter (NIS) may be an important factor that leads to the reduced iodine accumulation characteristic of most benign and malignant thyroid nodules. Both up- and down-regulation of NIS gene expression have been reported in thyroid cancer using several different methods. The goal of the present study was to accurately identify alterations in NIS gene expression in benign and malignant thyroid nodules using an accurate real-time quantitative RT-PCR assay system. Total RNA was prepared from 18 benign thyroid nodules, 20 papillary thyroid cancers, and 23 normal thyroid samples from 38 subjects. Quantitative RT-PCR was used to measure NIS and thyroglobulin (TG) mRNA expression in normal thyroid tissue and in each nodular tissue sample. Papillary thyroid cancer samples had significantly lower NIS mRNA expression (72 +/- 41 picogram equivalents [pg Eq]), than did benign nodules (829 +/- 385 pg Eq), or normal tissues (1907 +/- 868 pg Eq, P = 0.04). Most important, in the paired samples, NIS gene expression was decreased in each papillary thyroid cancer compared with normal tissue (69% median decrease; range, 40-96%; P = .013). Eleven of the 12 benign nodules also demonstrated lower NIS gene expression than the normal tissue (49% decrease; range, 2-96%; P = .04). Analysis of the paired samples demonstrated that Tg mRNA expression was significantly lower in each of the thyroid cancer samples than in corresponding normal tissue (759 +/- 245 pg Eq vs. 1854 +/- 542 pg Eq, P = .03). We have demonstrated a significant decrement in NIS gene expression in all papillary thyroid cancers and in over 90% of benign nodules examined compared with adjacent normal thyroid tissue, using a highly accurate quantitative RT-PCR technique. Similarly, thyroid cancers demonstrated significantly lower TG mRNA expression than corresponding normal thyroid. Reduced NIS expression may be an important factor in the impairment of iodine-concentrating ability of neoplastic thyroid tissues.

Genetic susceptibility factors of Type 1 diabetes in Asians

Type 1 diabetes is a multifactorial disease in which the insulin producing beta-cells of the pancreas are destroyed by the immune system, a process determined by the activity of major histocompatibility complex (MHC)-restricted T lymphocytes. Progress has been made in elucidating genetic factors involved in Type 1 diabetes in Caucasians, with less data available from Asia. For Asians, the human MHC locus (HLA region), especially the class II region, is the major susceptibility interval. The role of IDDM2, the insulin locus, has been questioned in Asia. In contrast to Caucasians, Asian populations have a very low incidence of Type 1 diabetes (0.4-1.1 cases/year/100 000 individuals). This low incidence rate in the Asian population may be related to the population frequency distribution of susceptible Type 1 diabetes genes, especially of HLA. The overall risk for Type 1 diabetes from HLA DR and DQ is determined by polymorphic residues (alleles) and particular combinations of alleles (haplotypes and genotypes) in a given individual. In Asians, it is very common that a protective DR4 allele is associated with susceptible DQ alleles while neutral/protective DQ alleles are associated with the susceptible DR4 alleles. Our analyses indicate that the counterbalancing between susceptible DRB1 and protective DQB1, and vice versa, is a factor that may contribute to the low incidence of diabetes in Asians. We find that identical HLA DRB1-DQB1 haplotypes of Asians and Caucasians have similar transmission to diabetic children and similar associations with diabetes. Moreover, the association with diabetes and transmission to a diabetic offspring of DR4 haplotypes varies depending on the haplotype borne on the homologous chromosome. This might contribute not only to the synergistic effect of DR3/4, but also to the susceptibility influence of DQB1*0401 haplotypes confined to DR4/X. High-risk DR4 subtypes were predominant in DR4/X, whereas protective DR4 subtypes were observed mainly in the DR3/4 genotype. Since in Asians DQB1*0401 is in linkage disequilibrium (LD) with DRB1*0405, we find more DRB1*0405-DQB1*0401 haplotypes in patients with DR4/X than in patients with DR3/4, suggesting that the contribution of the DRB1 locus may be greater in DR4/X than in DR3/4 genotypes. Several genome scans suggested additional susceptibility intervals and provided supporting evidence for several previously reported linkages. Other studies focused on the confirmation of linkage using multipoint sib-pair analyses with densely spaced markers and multiethnic collection of families. Although significant and consistent linkage evidence was reported for the susceptibility intervals IDDM12 (on 2q33) even in Asia, evidence for most other intervals varies in different data sets. LD mapping has become an increasingly important tool for both confirmation and fine-mapping of susceptibility intervals, as well as identification of etiological mutations. The examination of large and ethnically varied data sets including those of Asia has allowed identification of haplotypes that differ only at a single codon in a single locus. As more data become available, the study of pairs of haplotypes which differ at a single polymorphic site, but have different effects on disease susceptibility, should allow more precise definition of the polymorphisms involved in the disease process.