NIS Expression Research Articles

Sequence defined cMET/HGFR-targeted polymers as gene delivery vehicles for the theranostic sodium iodide symporter (NIS) gene

The sodium iodide symporter (NIS) as well-characterized theranostic gene represents an outstanding tool to target different cancer types allowing noninvasive imaging of functional NIS expression and therapeutic radioiodide application. Based on its overexpression on the surface of most cancer types, the cMET/hepatocyte growth factor receptor serves as ideal target for tumor-selective gene delivery. Sequence-defined polymers as nonviral gene delivery vehicles comprising polyethylene glycol (PEG) and cationic (oligoethanoamino) amide cores coupled with a cMET-binding peptide (cMBP2) were complexed with NIS-DNA and tested for receptor-specificity, transduction efficiency, and therapeutic efficacy in hepatocellular cancer cells HuH7. In vitro iodide uptake studies demonstrated high transduction efficiency and cMET-specificity of NIS-encoding polyplexes (cMBP2-PEG-Stp/NIS) compared to polyplexes without targeting ligand (Ala-PEG-Stp/NIS) and without coding DNA (cMBP2-PEG-Stp/Antisense-NIS). Tumor recruitment and vector biodistribution were investigated in vivo in a subcutaneous xenograft mouse model showing high tumor-selective iodide accumulation in cMBP2-PEG-Stp/NIS-treated mice (6.6 ± 1.6% ID/g 123 I, biological half-life 3 hours) by 123 I-scintigraphy. Therapy studies with three cycles of polyplexes and 131 I application resulted in significant delay in tumor growth and prolonged survival. These data demonstrate the enormous potential of cMET-targeted sequence-defined polymers combined with the unique theranostic function of NIS allowing for optimized transfection efficiency while eliminating toxicity.

413. Effect of Adenoviral Death Protein on NIS-Based Iodine Therapy and Imaging for Pancreatic Cancer

In this study, we assess our novel Oncolytic Adenovirus (OAd) expressing a dual function therapeutic and imaging transgene, the sodium-iodide symporter (NIS) as a promising alternative for pancreatic cancer treatment. We hypothesized that NIS expression in pancreatic cancer will induce uptake of radioiodine and allow noninvasive SPECT/CT imaging with 123I. We designed our OAd-NIS to overcome the low efficacy of previous vectors. These viruses have a modified Ad5/Ad3 fiber-knob shown to improve the poor transduction of pancreatic cancer cells. Viral replication is controlled under the Cox2 promoter allowing specific delivery of viral genes, and most of adenoviral E3 genes are deleted and replaced with NIS and Adenovirus Death Protein (ADP) genes. We have previously demonstrated significantly improved ability of ADP-overexpressing OAds to enhance viral release and cytolytic activity. Although improved oncolysis enhances viral release and improve the therapeutic effect in solid tumors, it can potentially reduce radioiodide tracer uptake. To test this possibility we designed and compared identical vectors with ADP (OAd-NIS-ADP) and without ADP (OAd-NIS-noADP) in vitro and in vivo. We first compared virus killing ability in pancreatic cancer cell lines. The ADP+ vector was significantly more cytolytic that no-ADP counterpart and showed improved viral replication and spread. Cox2-controlled OAd did not produce cell death in Cox2-negative control, confirming selectivity. We next assessed OAds ability to induce NIS protein expression and radioiodine uptake. NIS-OAds efficiently produce glycosylated NIS multimers as early as 2-days post infection. Infection with no-ADP vectors resulted in a significantly greater radioiodine uptake (125I) compared to ADP+ viruses. Importantly, ex vivo uptake test in human patient tissues confirmed the high level of NIS in pancreatic adenocarcinoma samples, and revealed no 125I uptake in normal pancreas. We further assessed the ability of our vectors to visualize human pancreatic cancer xenografts in a mouse model by monitoring 99mTcO4− accumulation with SPECT-CT. The OAd-NIS-noADP showed an earlier and more sustained radioisotope uptake when compared to ADP+ supporting its use as a more sensitive diagnostic tool for pancreatic cancer. Of contrary, the ADP+ vector significantly outperformed OAd-NIS-noADP in tumor shrinkage. These results suggest that while OAd-NIS-noADP produces a greater radiotracer uptake and can be used as a diagnostic tool, its ADP+ counterpart results in a better therapeutic effect when applied as a monotherapy. It is now essential to estimate the therapeutic ability of both vectors upon combination with I-131 (ongoing study). Further investigation will include the imaging and therapeutic studies in patient-derived xenografts. Ultimately, the goal of our research is to design a multimodal therapy with radiation and oncolytic virus for diagnosis and therapy of cancers.

Enantioselectivity in Developmental Toxicity of rac-metalaxyl and R-metalaxyl in Zebrafish (Danio rerio) Embryo.

Enantioselectivity of chiral pesticides in environmental safety has attracted more and more attention. In this study, we evaluated the enantioselective toxicity of rac-metalaxyl and R-metalaxyl to zebrafish (Danio rerio) embryos through various malformations including pericardial edema, yolk sac edema, crooked body, and short tails. The results showed that there were significant differences in toxicity to zebrafish embryos caused by rac-metalaxyl and R-metalaxyl, and the LC50 s at 96 h are 416.41 (353.91, 499.29) mg · L(-1) and 320.650 (279.80, 363.46) mg · L(-1) , respectively. In order to explore the possible mechanism of the development defects, the genes involved in the hypothalamic-pituitary-gonadal axis (vtg1, vtg2, cyp17, cyp19a, cyp19b) and hypothalamic-pituitary-thyroid axis (dio1, dio2, nis, tg, tpo) were quantified by quantitative real-time polymerase chain reaction (qRT-PCR). The results revealed that there were no significant differences in the expression of vtg1, vtg2, cyp17, cyp19a, and cyp19b after exposure to rac-metalaxyl. However, the expression of vtg1, cyp19a, and cyp19b decreased significantly after exposure to R-metalaxyl. And likewise, rac-metalaxyl only caused the upregulation of dio2, while R-metalaxyl suppressed the expression of dio1 and tpo and induced the expression of dio2 and nis. The change of gene expression may cause the enantioselectivity in developmental toxicity in zebrafish embryo. The data provided here will be helpful for us to comprehensively understand the potential ecological risks of the currently used chiral fungicides. Chirality 28:489-494, 2016. © 2016 Wiley Periodicals, Inc.

Linking loss of sodium-iodide symporter expression to DNA damage

Radiotherapy of thyroid cancer with I-131 is abrogated by inherent loss of radioiodine uptake due to loss of sodium iodide symporter (NIS) expression in poorly differentiated tumor cells. It is also known that ionizing radiation per se down-regulates NIS (the stunning effect), but the mechanism is unknown. Here we investigated whether loss of NIS-mediated iodide transport may be elicited by DNA damage. Calicheamicin, a fungal toxin that specifically cleaves double-stranded DNA, induced a full scale DNA damage response mediated by the ataxia-telangiectasia mutated (ATM) kinase in quiescent normal thyrocytes. At sublethal concentrations (<1nM) calicheamicin blocked NIS mRNA expression and transepithelial iodide transport as stimulated by thyrotropin; loss of function occurred at a much faster rate than after I-131 irradiation. KU-55933, a selective ATM kinase inhibitor, partly rescued NIS expression and iodide transport in DNA-damaged cells. Prolonged ATM inhibition in healthy cells also repressed NIS-mediated iodide transport. ATM-dependent loss of iodide transport was counteracted by IGF-1. Together, these findings indicate that NIS, the major iodide transporter of the thyroid gland, is susceptible to DNA damage involving ATM-mediated mechanisms. This uncovers novel means of poor radioiodine uptake in thyroid cells subjected to extrinsic or intrinsic genotoxic stress.

The correlation of sodium iodide symporter and BRAF(V600E) mutation in classical variant papillary thyroid carcinoma.

BRAF(V600E) mutation was analyzed by real-time polymerase chain reaction in 96 consecutive cases with classical variant papillary thyroid cancer, and immunohistochemical staining of Na+/I- symporter (NIS) protein was evaluated. Localization (intracellular or membranous), density, and the intensity of cytoplasmic staining were characterized semiquantitatively. Extrathyroidal invasion, surgical margin positivity, and lymph node metastasis were compared with BRAF(V600E) mutation and NIS expression. Eighty-eight patients who had at least 24-month follow-up were also included in survival analysis. BRAF(V600E) mutation was determined in 78.1% (75/96) and functional NIS activity in 74% (71/96) of the cases. There were statistically significant differences in mean ages between BRAF(V600E) mutation-positive (48.6) and BRAF(V600E) mutation-negative cases (37.3; Levene test, P=.419; Student t test, P=.001). The surgical margin positivity (46.7%) and extrathyroidal extension percentage (54.7%) in the BRAF(V600E) mutation-positive group were higher than the negative (28.6% and 33.3%, respectively) group, without statistical significance (P=.138 and P=.084, respectively). Functional NIS activity was higher in BRAF(V600E) mutation-positive cases (78.1%) than mutation-negative ones (57.1%; P=.047). The possibility of moderate and intense cytoplasmic staining in BRAF(V600E) mutation-positive cases (72%) was 6.3 times higher than the possibility of weak staining (28%) in the mutation-positive cases (95% confidence interval, 2.2-18.8; P=.001). Functional NIS expression is higher in patients with classical variant papillary thyroid cancer with BRAF(V600E) mutation. However, the clinical features were not found to be associated with NIS expression. There may be different mechanisms determining the outcome of therapy.

A systematic evaluation of sorting motifs in the sodium-iodide symporter (NIS).

The sodium-iodide symporter (NIS) is an integral membrane protein that plays a crucial role in iodide accumulation, especially in the thyroid. As for many other membrane proteins, its intracellular sorting and distribution have a tremendous effect on its function, and constitute an important aspect of its regulation. Many short sequences have been shown to contribute to protein trafficking along the sorting or endocytic pathways. Using bioinformatics tools, we identified such potential sites on human NIS [tyrosine-based motifs, SH2-(Src homology 2), SH3- and PDZ (post-synaptic density-95/discs large tumour suppressor/zonula occludens-1)-binding motifs, and diacidic, dibasic and dileucine motifs] and analysed their roles using mutagenesis. We found that several of these sites play a role in protein stability and/or targeting to the membrane. Aside from the mutation at position 178 (SH2 plus tyrosine-based motif) that affects iodide uptake, the most drastic effect is associated with the mutation of an internal PDZ-binding motif at position 121 that completely abolishes NIS expression at the plasma membrane. Mutating the sites located on the C-terminal domain of the protein has no effect except for the creation of a diacidic motif that decreases the total NIS protein level without affecting its expression at the plasma membrane.

Nuclear translocation of β-catenin represses membrane localization of NIS in human thyroid cancer cells

To explore whether nuclear translocation of β-catenin affects functional expression of sodium iodide symporter (NIS) in human thyroid cancer cells. Two kinds of β-catenin nuclear translocation cell models were firstly established with transfection of hypoxia inducible factor 1α (HIF-1α) and β-catenin cDNA in human thyroid cancer cell line FTC133. Then the expression of β-catenin were further interfered by shRNA in above two cell models. After that, the influence of β-catenin nuclear localization on the functional expression of NIS, iodine uptake potency, epithelial-mesenchymal transition (EMT) characteristics, tumor growth curve and treatment effect inducing by radioactive iodine were comparatively analyzed in vitro and in vivo trials. Additionally, the underlying mechanism of NIS functional expression was also assessed via identifying the activation of β-catenin signal pathway. In vitro assay showed prominent EMT phenotype in the above two β-catenin nuclear translocation cell models, and in vitro proliferation and invasion potential of cancer cells markedly increased (all P<0.05); NIS protein expression translocated from cell membrane to cytoplasma. Cell iodide uptake in vitro decreased about 50.0% and 37.5%, respectively in above two β-catenin translocation cell models (both P<0.05). Moreover, β-catenin nuclear translocation was correlated with phosphorylation expressions of β-catenin Ser45, Y654 and GSK-3β Ser9. Most importantly, all above changes associated with β-catenin nuclear translocation could be effectively reversed after blockade of β-catenin expression. In the animal model, tumor growth potential and tumor mass were significantly inhibited by both blockade of β-catenin and radioactive iodide ((131)I) (all P<0.05). Meanwhile, immunohistochemistry demonstrated that β-catenin nuclear translocation remained in subcutaneous tumor cells after transplantation, and showed negatively associated with NIS membrane expression. β-catenin nuclear translocation is a vital regulatory pathway involved in functional expression of NIS in human thyroid cancer cells.

Immunovirotherapy with vesicular stomatitis virus and PD-L1 blockade enhances therapeutic outcome in murine acute myeloid leukemia

AbstractPatients with relapsed acute myeloid leukemia (AML) have limited therapeutic options. Vesicular stomatitis virus (VSV)–interferon β (IFNβ)–sodium iodide symporter (NIS) is an oncolytic VSV encoding IFNβ and the NIS reporter. Syngeneic AML C1498 tumors responded to IV therapy with VSV-murine IFNβ (mIFNβ)-NIS in a dose-dependent manner. Imaging for NIS expression showed robust virus infection within the tumors. Virus infection did not increase programmed death ligand 1 (PD-L1) on tumor cells. Combining VSV-mIFNβ-NIS with anti-PD-L1 antibody (Ab) therapy enhanced antitumor activity compared with treatment with virus alone or Ab alone; this enhancement was not significant at higher VSV-mIFNβ-NIS doses. Systemic VSV therapy reduced systemic C1498–green fluorescent protein (GFP) tumor burden in the blood, bone marrow, spleen, and liver of mice with AML. Combination VSV-mIFNβ-NIS and anti-PD-L1 Ab therapy significantly enhanced the survival of these mice with no evidence of toxicity, compared with isotype control, anti-PD-L1, or virus alone. There was an increase in tumor-infiltrating CD4 and CD8 cells. Single-agent VSV-mIFNβ-NIS virotherapy induced both VSV-specific and GFP-specific CD8 T cells as determined by IFN-γ enzyme-linked immunospot, pentamer, and intracellular IFN-γ staining assays. Both of these responses were further enhanced by addition of anti-PD-L1 Ab. Depletion of CD8 or natural killer cells, but not CD4 cells, resulted in loss of antitumor activity in the VSV/anti-PD-L1 group. Clinical samples from chronic myelomonocytic leukemia and acute myelomonocytic leukemia appear to be especially susceptible to VSV. Overall, our studies show that oncolytic virotherapy combined with immune checkpoint blockade is a promising approach to AML therapy.

All-trans retinoic acid improves iodine uptake of thyroid cancer cells via repressing transcriptional activity of β-catenin

To determine whether all-trans retinoic acid (ATRA) could improve iodine uptake via repressing transcriptional activity of β-catenin in thyroid cancer cells. Three kinds of treatment models were firstly established with alcohol, ATRA, and transfection of β-catenin shRNA in undifferentiated human thyroid cancer cell line-SW1736.Then the expressions of sodium iodide symporter (NIS), β-catenin and its regulating factors, epithelial-mensechymal transition (EMT)-phenotype, invasion and metastasis associated proteins were further measured in above three cell models.After that, the influence of ATRA on the functional expression of NIS, iodine uptake potency, tumor growth curve and treatment effect inducing by radioactive iodine was comparatively analyzed in vitro and in vivo trials. After treated with ATRA, transcriptional activity of β-catenin decreased by downregulating phosphorylation of β-catenin Ser45, Y654 and GSK-3β Ser9. Additionally, ATRA effectively upregulated the protein level of NIS, and reversed EMT phenotype in alcohol treated cells, with absence in epithelial expression of E-cadherin and cytokeratin 18, as well as abnormal expression of Vimentin, urinary plasminogen activator (uPA), uPAR and Fibronectin.Compared with alcohol-treated group, both in vitro proliferation and invasion potential of ATRA treated cells markedly decreased (all P<0.05), and iodine uptake in vitro increased about 3.5-folds (P=0.007). In ATRA-treated animal model, tumor growth potential and tumor mass were significantly inhibited by radio-iodine ((131)I) treatment (all P<0.05). ATRA can increase functional expression of NIS via downregulating transcriptional activity of β-catenin and promote isotope sensitivity to radio-iodine in human undifferentiated thyroid cancer.

Excess iodide downregulates Na+/I− symporter gene transcription through activation of PI3K/Akt pathway

Transcriptional mechanisms associated with iodide-induced downregulation of NIS expression remain uncertain. Here, we further analyzed the transcriptional regulation of NIS gene expression by excess iodide using PCCl3 cells. NIS promoter activity was reduced in cells treated for 12–24 h with 10−5 to 10−3 M NaI. Site-directed mutagenesis of Pax8 and NF-κB cis-acting elements abrogated the iodide-induced NIS transcription repression. Indeed, excess iodide (10−3 M) excluded Pax8 from the nucleus, decreased p65 total expression and reduced their transcriptional activity. Importantly, p65-Pax8 physical interaction and binding to NIS upstream enhancer were reduced upon iodide treatment. PI3K/Akt pathway activation by iodide-induced ROS production is involved in the transcriptional repression of NIS expression. In conclusion, the results indicated that excess iodide transcriptionally represses NIS gene expression through the impairment of Pax8 and p65 transcriptional activity. Furthermore, the data presented herein described novel roles for PI3K/Akt signaling pathway and oxidative status in the thyroid autoregulatory phenomenon.

Effects of BRAF(V600E) mutation on Na(+)/I(-) symporter expression in papillary thyroid carcinoma.

Radioiodine ablation (RIA) therapy is one of the most important treatments for papillary thyroid carcinoma (PTC), but some patients who received (131)I have radioiodine-refractory disease caused by the decreased expression of the Na(+)/I(-) symporter (NIS). BRAF(V600E) mutation is one possible risk factor that can disturb the NIS expression, but the roles are unclear in clinical practice. This research discussed the association of BRAF(V600E) mutation and NIS expression in PTC tissue and the clinical implications in RIA therapy. 134 PTC samples were collected between June 2013 and June 2014 from Tongji Hospital affiliated to Tongji Medical College, and their clinical characteristics were analyzed. RT-PCR was used to detect the BRAF(V600E) mutation from formalin-fixed paraffin-embedded samples, and immunohistochemistry was applied to detect the NIS expression. IPP software was used to calculate the relative expression quantity of NIS. We found that there was no significant correlation between the absorbance (A) values of NIS and clinicopathologic features in these cases, even thyroid stimulating hormone. BRAF(V600E) mutation showed inhibitory effect on the NIS expression without statistically significant difference in all PTC cases (β=-0.0195, P=0.085), but in the subgroup without hashimoto's thyroiditis (HT), BRAF(V600E) mutation could significantly inhibit the NIS expression (β=-0.0257, P=0.046). The results indicate that BRAF(V600E) mutation is correlated with a lower expression of NIS in PTCs without HT, suggesting the radioiodine-refractory effects during RIA therapy in these patients.

Oncolytic vaccinia virus as a vector for therapeutic sodium iodide symporter gene therapy in prostate cancer

Oncolytic strains of vaccinia virus are currently in clinical development with clear evidence of safety and promising signs of efficacy. Addition of therapeutic genes to the viral genome may increase the therapeutic efficacy of vaccinia. We evaluated the therapeutic potential of vaccinia virus expressing the sodium iodide symporter (NIS) in prostate cancer models, combining oncolysis, external beam radiotherapy and NIS-mediated radioiodide therapy. The NIS-expressing vaccinia virus (VV-NIS), GLV-1h153, was tested in in vitro analyzes of viral cell killing, combination with radiotherapy, NIS expression, cellular radioiodide uptake and apoptotic cell death in PC3, DU145, LNCaP and WPMY-1 human prostate cell lines. In vivo experiments were carried out in PC3 xenografts in CD1 nude mice to assess NIS expression and tumor radioiodide uptake. In addition, the therapeutic benefit of radioiodide treatment in combination with viral oncolysis and external beam radiotherapy was measured. In vitro viral cell killing of prostate cancers was dose- and time-dependent and was through apoptotic mechanisms. Importantly, combined virus therapy and iodizing radiation did not adversely affect oncolysis. NIS gene expression in infected cells was functional and mediated uptake of radioiodide both in vitro and in vivo. Therapy experiments with both xenograft and immunocompetent Transgenic Adenocarcinoma of the Mouse Prostate (TRAMP) mouse models showed that the addition of radioiodide to VV-NIS-infected tumors was more effective than each single-agent therapy, restricting tumor growth and increasing survival. In conclusion, VV-NIS is effective in prostate cancer models. This treatment modality would be an attractive complement to existing clinical radiotherapy practice.

Selenium Increases Thyroid-Stimulating Hormone-Induced Sodium/Iodide Symporter Expression Through Thioredoxin/Apurinic/Apyrimidinic Endonuclease 1-Dependent Regulation of Paired Box 8 Binding Activity.

The sodium-iodide symporter (NIS) mediates the uptake of I(-) by the thyroid follicular cell and is essential for thyroid hormone biosynthesis. Nis expression is stimulated by thyroid-stimulating hormone (TSH) and also requires paired box 8 (Pax8) to bind to its promoter. Pax8 binding activity depends on its redox state by a mechanism involving thioredoxin/thioredoxin reductase-1 (Txn/TxnRd1) reduction of apurinic/apyrimidinic endonuclease 1 (Ape1). In this study, we investigate the role of Se in Nis expression. Selenium increases TSH-induced Nis expression and activity in rat thyroid cells. The stimulatory effect of Se occurs at the transcriptional level and is only observed for Nis promoters containing a Pax8 binding site in the Nis upstream enhancer, suggesting that Pax8 is involved in this effect. In fact, Se increases Pax8 expression and its DNA-binding capacity, and in Pax8-silenced rat thyroid cells, Nis is not Se responsive. By inhibiting Ape1 and TxnRd1 functions, we found that both enzymes are crucial for TSH and TSH plus Se stimulation of Pax8 activity and mediate the Nis response to Se treatment. We describe that Se increases Nis expression and activity. We demonstrate that this effect is dependent on the redox functions of Ape1 and Txn/TxnRd1 through control of the DNA binding activity of Pax8. Nis expression is controlled by Txn/Ape1 through a TSH/Se-dependent mechanism. These findings open a new field of study regarding the regulation of Nis activity in thyroid cells. Antioxid. Redox Signal. 24, 855-866.

Enhancement of human sodium iodide symporter gene therapy for breast cancer by HDAC inhibitor mediated transcriptional modulation

The aberrant expression of human sodium iodide symporter (NIS) in breast cancer (BC) has raised the possibility of using targeted radioiodide therapy. Here we investigate modulation of endogenous, functional NIS expression by histone deacetylase inhibitors (HDACi) in vitro and in vivo. Luciferase reporter based initial screening of six different HDACi shows 2–10 fold enhancement of NIS promoter activity in majority of the cell types tested. As a result of drug treatment, endogenous NIS transcript and protein shows profound induction in BC cells. To get an insight on the mechanism of such transcriptional activation, role of Stat4, CREB and other transcription factors are revealed by transcription factor profiling array. Further, NIS-mediated intracellular iodide uptake also enhances substantially (p < 0.05) signifying functional relevance of the transcriptional modulation strategy. Gamma camera imaging confirms 30% higher uptake in VPA or NaB treated BC tumor xenograft. Corroborating with such functional impact of NIS, significant reduction in cell survival (p < 0.005) is observed in VPA, NaB or CI994 drug and 131I combination treatment in vivo indicating effective radioablation. Thus, for the first time this study reveals the mechanistic basis and demonstrates functional relevance of HDACi pre-treatment strategy in elevating NIS gene therapy approach for BC management in clinic.

Thyroid-Specific Genes Expression Uncovered Age-Related Differences in Pediatric Thyroid Carcinomas.

Despite a more advanced stage of disease at presentation, a better response to radioiodine (RAI) therapy and a reduced overall mortality have been reported in pediatric differentiated thyroid cancer (DTC) in comparison to adult DTC. Few studies suggested that the better response to RAI therapy in pediatric patients might be associated with an increased expression of NIS. However, a marked heterogeneity within the pediatric group has been recognized. Children (<10 years old) usually present a more aggressive disease than adolescents (≥10–18 years old). By analyzing the expression of thyroid-specific genes in 38 sporadic pediatric tumors, we show that the expression of NIS, PDS, and TSHR was lower in children than adolescents (P < 0.05). A linear regression confirmed the association between NIS expression and age. Most significantly, NIS was expressed at similar levels in DTC from children and adults, whereas PDS and TSHR expression was even lower in DTC from children, compared to adolescents and adults. Our data suggest that biological behaviors of DTC in adolescents might differ from those in children and adults. Therefore, the premise that the expression of thyroid-specific genes is higher in tumors from pediatric patients than in adults is not entirely true and might be too oversimplified.

Hybrid Molecular Imaging in Differentiated Thyroid Carcinoma.

Radioactive isotopes of radioiodine are frequently used in differentiated thyroid carcinoma (DTC) both for diagnosis and therapy. Their accumulation in thyroid cancer tissue is dependent on the expression and activity of the sodium-iodide symporter (NIS). Scintigraphic imaging using either planar or single-photon emission computed tomography (SPECT) cameras allows the visualization of their distribution within the human body. Due to only a poor visualization of morphology by these techniques, their diagnostic accuracy is, however, limited. This limitation is overcome when hybrid systems integrating a SPECT camera with an X-ray CT scanner are used. Roughly one third of patients with diagnostically unclear foci of radioiodine accumulation will benefit from the use of SPECT/CT, also in terms of therapeutic management. SPECT/CT has, therefore, become the gold standard of nuclear imaging in DTC. NIS expression may be absent in DTC. In this case, the glucose transporters are usually upregulated. Therefore, PET/CT using 18F-deoxyglucose can be used to diagnose and localize tumor recurrence as a prerequisite to, in particular, surgical intervention.

Influencing factors on the function of sodium iodide symporter in differentiated thyroid cancer

The expression and function of NIS are the prerequisites of radioactive iodine(RAI) treatment for DTC, which in turn determine the iodine uptake and outcome in DTC patients. Studies for the factors that might influence the function of NIS for the development of redifferentiation therapy should be conducted in conjunction with the individualized course of treatment in DTC patients having poor iodine uptake in their thyroid tumors. This review summarizes the factors that influence the function and expression of NIS in these patients. Key words: Thyroid neoplasms; Sodium/iodine symporter; Radiotherapy; Trends

Inhibition of BRD4 suppresses tumor growth and enhances iodine uptake in thyroid cancer

Thyroid cancer is a common malignancy of the endocrine system. Although radioiodine 131I treatment on differentiated thyroid cancer is widely used, many patients still fail to benefit from 131I therapy. Therefore, exploration of novel targeted therapies to suppress tumor growth and improve radioiodine uptake remains necessary. Bromodomain-containing protein 4 (BRD4) is an important member of the bromodomain and extra terminal domain family that influences transcription of downstream genes by binding to acetylated histones. In the present study, we found that BRD4 was up-regulated in thyroid cancer tissues and cell lines. Inhibition of BRD4 in thyroid cancer cells by JQ1 resulted in cell cycle arrest at G0/G1 phase and enhanced 131I uptake in vitro and suppressed tumor growth in vivo. Moreover, JQ1 treatment suppressed C-MYC but enhanced NIS expression. We further demonstrated that BRD4 was enriched in the promoter region of C-MYC, which could be markedly blocked by JQ1 treatment. In conclusion, our findings revealed that the aberrant expression of BRD4 in thyroid cancer is possibly involved in tumor progression, and JQ1 is potentially an effective chemotherapeutic agent against human thyroid cancer.

The Effect on Sodium/Iodide Symporter and Pendrin in Thyroid Colloid Retention Developed by Excess Iodide Intake.

It is well known that excess iodide can lead to thyroid colloid retention, a classic characteristic of iodide-induced goiter. However, the mechanism has not been fully unrevealed. Iodide plays an important role in thyroid function at multiple steps of thyroid colloid synthesis and transport among which sodium/iodide symporter (NIS) and pendrin are essential. In our study, we fed female BALB/c mice with different concentrations of high-iodine water including group A (control group, 0μg/L), group B (1500μg/L), group C (3000μg/L), group D (6000μg/L), and group E (12,000μg/L). After 7months of feeding, we found that excess iodide could lead to different degrees of thyroid colloid retention. Besides, NIS and pendrin expression were downregulated in the highest dose group. The thyroid iodide intake function detected by urine iodine assay and thyroidal (125)I experiments showed that the urine level of iodine increased, while the iodine intake rate decreased when the concentration of iodide used in feeding water increased (all p<0.05 vs. control group). In addition, transmission electron microscopy (TEM) indicated a reduction in the number of intracellular mitochondria of thyroid cells. Based on these findings, we concluded that the occurrence of thyroid colloid retention exacerbated by excess iodide was associated with the suppression of NIS and pendrin expression, providing an additional insight of the potential mechanism of action of excess iodide on thyroid gland.

Glycosylation of Sodium/Iodide Symporter (NIS) Regulates Its Membrane Translocation and Radioiodine Uptake.

PurposeHuman sodium/iodide symporter (hNIS) protein is a membrane glycoprotein that transports iodide ions into thyroid cells. The function of this membrane protein is closely regulated by post-translational glycosylation. In this study, we measured glycosylation-mediated changes in subcellular location of hNIS and its function of iodine uptake.MethodsHeLa cells were stably transfected with hNIS/tdTomato fusion gene in order to monitor the expression of hNIS. Cellular localization of hNIS was visualized by confocal microscopy of the red fluorescence of tdTomato. The expression of hNIS was evaluated by RT-PCR and immunoblot analysis. Functional activity of hNIS was estimated by radioiodine uptake. Cyclic AMP (cAMP) and tunicamycin were used to stimulate and inhibit glycosylation, respectively. In vivo images were obtained using a Maestro fluorescence imaging system.ResultscAMP-mediated Glycosylation of NIS resulted in increased expression of hNIS, stimulating membrane translocation, and enhanced radioiodine uptake. In contrast, inhibition of glycosylation by treatment with tunicamycin dramatically reduced membrane translocation of intracellular hNIS, resulting in reduced radioiodine uptake. In addition, our hNIS/tdTomato fusion reporter successfully visualized cAMP-induced hNIS expression in xenografted tumors from mouse model.ConclusionsThese findings clearly reveal that the membrane localization of hNIS and its function of iodine uptake are glycosylation-dependent, as our results highlight enhancement of NIS expression and glycosylation with subsequent membrane localization after cAMP treatment. Therefore, enhancing functional NIS by the increasing level of glycosylation may be suggested as a promising therapeutic strategy for cancer patients who show refractory response to conventional radioiodine treatment.