Iodide transport in a continuous line of cultured cells from rat thyroid

Inflammatory tumor microenvironment of thyroid cancer promotes cellular dedifferentiation and silencing of iodide-handling genes expression

BACKGROUND

Due to dedifferentiation of tumor cells, manifested by a decreased expression of iodide-handling genes in thyrocytes, some thyroid carcinomas lose their capability for radioiodine concentration and gradually develop radioactive iodine (RAI) resistance. This work aimed to investigate the role of tumor microenvironment (TME) in the process of tumor cell dedifferentiation.

MATERIALS AND METHODS

Bioinformatic analyses and subsequent immunohistochemistry (IHC) and western blot assays were performed in papillary thyroid carcinoma (PTC) and matched normal tissue. ELISA was used to assess the secretion of cytokines under the stimulation of pharmacological endoplasmic reticulum (ER) stress inducer.

RESULTS

Higher levels of pro-inflammatory cytokines, interleukin 6 (IL-6) and (C-X-C motif chemokine ligand 8 (CXCL8), were found in thyroid cancer tissues compared with matched normal tissues. ER stress, induced by stressful environmental stimuli, such as nutrient deprivation and hypoxia, occurred in thyroid tumors. Classic ER stress inducers, thapsigargin (Tg) and tunicamycin (Tm), promoted the expression of IL6 and CXCL8 in thyroid cancer cells at mRNA and protein levels. Of note, rIL-6 and rCXCL8 promoted the dedifferentiation of thyroid cancer cells or even non-transformed cells in an autocrine/paracrine manner, weakening radioiodine uptake ability of thyroid cancer cells. Intriguingly, sorafenib, a multiple kinase inhibitor (MKI), could potently suppress not only ER stress-induced but also basal expressions of IL-6 and CXCL8 in thyroid cancer cells.

CONCLUSIONS

The inflammatory TME could regulate cell dedifferentiation, leading to loss of thyroid-specific gene expressions, through reciprocal interaction between thyroid tumor cells and follicular cells. Our study provides a new perspective on the mechanisms of how inflammatory TME affects DTC dedifferentiation.

Pyruvate carboxylase promotes malignant transformation of papillary thyroid carcinoma and reduces iodine uptake

Previous studies have shown that pyruvate carboxylase (PC) plays a key role in the occurrence and progression of thyroid cancer (TC); however, the relationship between PC and iodine-refractory TC is unclear. Therefore, the present study aimed to investigate the molecular mechanism of PC in the malignant progression and loss of iodine uptake in papillary TC (PTC) and to explore the potential therapeutic effect of PC inhibitors in iodine-refractory PTC. PC increased cell proliferation, invasion, and metastasis, inhibited expression of the iodine metabolism-related genes TSHR, NIS, TPO, and TG, and decreased the iodine-uptake capacity by activating the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway in PTC cell lines. Furthermore, the PC inhibitor ZY-444 effectively inhibited the activation of PC, reduced the malignant invasiveness, and restored the expression of iodine metabolism-related genes and the iodine-uptake capacity in PTC cells. These findings suggest that PC activation is involved in the progression of iodine-refractory TC and that PC inhibitors may represent a potentially novel targeted therapy for iodine-refractory TC.

In Silico Screening and Validation of PDGFRA Inhibitors Enhancing Radioiodine Sensitivity in Thyroid Cancer

Aberrant activation of platelet-derived growth factor receptor α (PDGFRA) has been implicated in tumorigenesis and radioiodine resistance of thyroid cancer, indicating its therapeutic potential. In the present study, we confirmed the association between PDGFRA and radioiodine resistance in thyroid cancer using bioinformatics analysis and constructed a prediction model of PDGFRA inhibitors using machine learning and molecular docking approaches. We then performed a virtual screening of a traditional Chinese medicine (TCM) derived compound library and successfully identified 4’,5,7-trimethoxyflavone as a potential PDGFRA inhibitor. Further characterization revealed a significant inhibitory effect of 4’,5,7-trimethoxyflavone on PDGFRA-MAPK pathway activation, and that it could upregulate expression of sodium iodide symporter (NIS) as well as improve radioiodine uptake capacity of radioiodine-refractory thyroid cancer (RAIR-TC), suggesting it a potential drug lead for the development of new RAIR-TC therapy.

Excess iodide-induced reactive oxygen species elicit iodide efflux via β-tubulin-associated ClC-3 in thyrocytes

Iodide (I-) is crucial to thyroid function, and its regulation in thyrocytes involves ion transporters and reactive oxygen species (ROS). However, the extent of 2Cl-/H+ exchanger (ClC-3) involvement in the iodide (I-) efflux from thyrocytes remains unclear. Therefore, we examined the effects of ClC-3 on I- efflux. ClC-3 expression was found to significantly alter the serum TT3 and TT4 concentrations in mice. We further found that excess I- stimulation affected ClC-3 expression, distribution, and I- efflux in FRTL-5 cells. Immunofluorescence analyses indicated that ClC-3 mainly accumulated in the cell membrane and co-localized with β-tubulins after 24 h of excess I- treatment, and that this process depended on ROS production. Thus, ClC-3 may be involved in I- efflux at the apical pole of thyrocytes via excess I--induced ROS production and β-tubulin polymerization. Our results reveal novel insights into the role of ClC-3 in I- transport and thyroid function.

Capsaicin restores sodium iodine symporter-mediated radioiodine uptake through bypassing canonical TSH‒TSHR pathway in anaplastic thyroid carcinoma cells

Anaplastic thyroid cancer (ATC) is a rare but highly lethal disease. ATCs are resistant to standard therapies and are extremely difficult to manage. The stepwise cell dedifferentiation results in the impairment of the iodine-metabolizing machinery and the infeasibility of radioiodine treatment in ATC. Hence, re-inducing iodine-metabolizing gene expression to restore radioiodine avidity is considered as a promising strategy to fight against ATC. In the present study, capsaicin (CAP), a natural potent transient receptor potential vanilloid type 1 (TRPV1) agonist, was discovered to re-induce ATC cell differentiation and to increase the expression of thyroid transcription factors (TTFs including TTF-1, TTF-2, and PAX8) and iodine-metabolizing proteins, including thyroid stimulating hormone receptor (TSHR), thyroid peroxidase, and sodium iodine symporter (NIS), in two ATC cell lines, 8505C and FRO. Strikingly, CAP treatment promoted NIS glycosylation and its membrane trafficking, resulting in a significant enhancement of radioiodine uptake of ATC cells in vitro. Mechanistically, CAP activated TRPV1 channel and subsequently triggered Ca2+ influx, cyclic adenosine monophosphate (cAMP) generation, and cAMP responsive element binding protein (CREB) signal activation. Next, CREB recognized and bound to the promoter of SLC5A5 to facilitate its transcription. Moreover, the TRPV1 antagonist CPZ, the calcium chelator BAPTA, and the PKA inhibitor H-89 effectively alleviated the re-differentiation exerted by CAP, demonstrating that CAP might improve radioiodine avidity through the activation of the TRPV1‒Ca2+/cAMP/PKA/CREB signaling pathway. In addition, our study indicated that CAP might trigger a novel cascade to re-differentiate ATC cells and provide unprecedented opportunities for radioiodine therapy in ATC, bypassing canonical TSH‒TSHR pathway.

Curcumin enhances the membrane trafficking of the sodium iodide symporter and augments radioiodine uptake in dedifferentiated thyroid cancer cells via suppression of the PI3K-AKT signaling pathway

Radioactive iodine (RAI) is commonly used to treat differentiated thyroid cancer (DTC). A major challenge is the dedifferentiation of DTC with the loss of radioiodine uptake. Patients with distant metastases have persistent or recurrent disease and develop resistance to RAI therapy due to tumor dedifferentiation. Hence, tumor redifferentiation to restore sensitivity to RAI therapy is considered a promising strategy to overcome RAI resistance. In the present study, curcumin, a natural polyphenolic compound, was found to re-induce cell differentiation and increase the expression of thyroid-specific transcription factors, TTF-1, TTF-2 and transcriptional factor paired box 8 (PAX8), and iodide-metabolizing proteins, including thyroid stimulating hormone receptor (TSHR), thyroid peroxidase (TPO) and sodium iodide symporter (NIS) in dedifferentiated thyroid cancer cell lines, BCPAP and KTC-1. Importantly, curcumin enhanced NIS glycosylation and its membrane trafficking, resulting in a significant improvement of radioiodine uptake in vitro. Additionally, AKT knockdown phenocopied the restoration of thyroid-specific gene expression; however, ectopic expressed AKT inhibited curcumin-induced up-regulation of NIS protein, demonstrating that curcumin might improve radioiodine sensitivity via the inhibition of the PI3K-AKT-mTOR signaling pathway. Our study demonstrates that curcumin could represent a promising adjunctive therapy for restoring iodide avidity and improve radioiodine therapeutic efficacy in patients with RAI-refractory thyroid carcinoma.

Calcium Signaling in the Thyroid: Friend and Foe

Simple Summary

All cells in our body are activated by several different signals. The calcium ion is one of the most versatile signaling molecules, and regulates a multitude of different events in the cells. These range from activation of muscle contraction, to the regulation of cell movement, just to name a few. In normal thyroid cells, calcium signaling is of importance for the normal physiology of the cells. In thyroid pathologies, e.g., thyroid cancer, calcium is important for the regulation of proliferation and invasion, and may also activate gene transcription programs important for cancer cell survival. In this Commentary, we summarize what is known regarding calcium in the normal thyroid, and highlight the importance of calcium signaling in thyroid pathologies.

Abstract

Calcium signaling participates in a vast number of cellular processes, ranging from the regulation of muscle contraction, cell proliferation, and mitochondrial function, to the regulation of the membrane potential in cells. The actions of calcium signaling are, thus, of great physiological significance for the normal functioning of our cells. However, many of the processes that are regulated by calcium, including cell movement and proliferation, are important in the progression of cancer. In the normal thyroid, calcium signaling plays an important role, and evidence is also being gathered showing that calcium signaling participates in the progression of thyroid cancer. This review will summarize what we know in regard to calcium signaling in the normal thyroid as, well as in thyroid cancer.

Feasibility of Bone Marrow Mesenchymal Stem Cell-Mediated Synthetic Radiosensitive Promoter-Combined Sodium Iodide Symporter for Radiogenetic Ovarian Cancer Therapy

Ovarian cancer is the most lethal gynecological cancer, most patients relapse within 12-24 months, and eventually die, especially platinum-resistant patients. Gene therapy has been one of the most potential methods for tumor treatment. Bone marrow mesenchymal stem cells (BMSCs) have been used for systemic delivery of therapeutic genes to solid tumors. Sodium iodide symporter (NIS) is an intrinsic membrane glycoprotein and can concentrate ¹³¹I, which is important for radionuclide therapy and nuclear medicine imaging in recent years. However, the rapid iodine efflux has become a bottleneck for NIS-mediated radionuclide gene therapy. Our previous studies found that the early growth response-1 (Egr1) promoter containing CC(A/T)6GG (CArG) elements had an ¹³¹I radiation-positive feedback effect on the NIS gene. Other research showed the synthesized Egr1 promoter containing four CArG elements, E4, was nearly three times as sensitive as the Egr1 promoter. In our study, BMSC-E4-NIS was engineered to express NIS under the control of E4 promoter using lentivirial vectors. After BMSC-E4-NIS implantation, no tumors were seen in BALB/c nude mice and BMSC-E4-NIS did not promote the growth of SKOV3 tumor. BMSCs migrated toward ovarian cancer samples in chemotaxis assays and to ovarian tumors in mice. Using micro-single-photon emission computed tomography/computed tomography (SPECT/CT) imaging, we found that E4 promoter produced a notable increase in ¹²⁵I uptake after ¹³¹I irradiation, the radionuclide uptake is almost three and six times more than Egr1 and cytomegalovirus (CMV) promoters. These studies confirmed the feasibility of using BMSCs as carriers for lentivirus-mediated E4-NIS gene therapy for ovarian cancer. Further research on BMSC-E4-NIS gene therapy for ovarian cancer in vivo will also be carried on, and if successful, this might provide a new adjuvant therapeutical option for platinum-resistant ovarian cancer patients and provide a new method for dynamic evaluation of curative effect.

Effective control of tumor growth through spatial and temporal control of theranostic sodium iodide symporter (NIS) gene expression using a heat-inducible gene promoter in engineered mesenchymal stem cells

Purpose: The tumor homing characteristics of mesenchymal stem cells (MSCs) make them attractive vehicles for the tumor-specific delivery of therapeutic agents, such as the sodium iodide symporter (NIS). NIS is a theranostic protein that allows non-invasive monitoring of the in vivo biodistribution of functional NIS expression by radioiodine imaging as well as the therapeutic application of ¹³¹I. To gain local and temporal control of transgene expression, and thereby improve tumor selectivity, we engineered MSCs to express the NIS gene under control of a heat-inducible HSP70B promoter (HSP70B-NIS-MSCs).

Experimental Design: NIS induction in heat-treated HSP70B-NIS-MSCs was verified by ¹²⁵I uptake assay, RT-PCR, Western blot and immunofluorescence staining. HSP70B-NIS-MSCs were then injected i.v. into mice carrying subcutaneous hepatocellular carcinoma HuH7 xenografts, and hyperthermia (1 h at 41°C) was locally applied to the tumor. 0 - 72 h later radioiodine uptake was assessed by ¹²³I-scintigraphy. The most effective uptake regime was then selected for ¹³¹I therapy.

Results: The HSP70B promoter showed low basal activity in vitro and was significantly induced in response to heat. In vivo, the highest tumoral iodine accumulation was seen 12 h after application of hyperthermia. HSP70B-NIS-MSC-mediated ¹³¹I therapy combined with hyperthermia resulted in a significantly reduced tumor growth with prolonged survival as compared to control groups.

Conclusions: The heat-inducible HSP70B promoter allows hyperthermia-induced spatial and temporal control of MSC-mediated theranostic NIS gene radiotherapy with efficient tumor-selective and temperature-dependent accumulation of radioiodine in heat-treated tumors.

Evaluation of potential sodium-iodide symporter (NIS) inhibitors using a secondary Fischer rat thyroid follicular cell (FRTL-5) radioactive iodide uptake (RAIU) assay

The Fischer rat thyroid follicular cell line (FRTL-5) endogenously expresses the sodium-iodide symporter (NIS) and has been used to identify environmental chemicals that perturb thyroid hormone homeostasis by disruption of NIS-mediated iodide uptake. Previously, a high-throughput radioactive iodide uptake (RAIU) screening assay incorporating the hNIS-HEK293T-EPA cell line was used to identify potential human NIS (hNIS) inhibitors in 1028 ToxCast Phase I (ph1_v2) and Phase II chemicals. In this study, the FRTL-5 cell line was evaluated and applied as a secondary RAIU assay coupled with cell viability assays to further prioritize highly active NIS inhibitors from the earlier screening. Assay validation with ten reference chemicals and performance assessment by chemical controls suggest the FRTL-5 based assays are robust and highly reproducible. Top-ranked chemicals from the ToxCast screening were then evaluated in both FRTL-5 and hNIS RAIU assays using newly sourced chemicals to strengthen the testing paradigm and to enable a rat vs. human species comparison. Eighteen of 29 test chemicals showed less than 1 order of magnitude difference in IC₅₀ values between the two assays. Notably, two common perfluorinated compounds, perfluorooctanesulfonic acid (PFOS) and perfluorohexane sulfonate (PFHxS), demonstrated strong NIS inhibitory activity [IC₅₀ - 6.45 (PFOS) and - 5.70 (PFHxS) log M in FRTL-5 RAIU assay]. In addition, several chemicals including etoxazole, methoxyfenozide, oxyfluorfen, triclocarban, mepanipyrim, and niclosamide also exhibited NIS inhibition with minimal cytotoxicity in both assays and are proposed for additional testing using short-term in vivo assays to characterize effects on thyroid hormone synthesis.

Effect of long- and short-chain perfluorinated compounds on cultured thyroid cells viability and response to TSH

PURPOSE

Perfluorinated chemicals are widespread pollutants persistent in the environment with links to some major health issues. The two main compounds, perfluoro-octanoic acid (PFOA) and perfluoro-alkyl sulphonate (PFOS), were recently classified as carcinogenetic and thus their use has been restricted. Short-chain PFCs were recently developed as an alternative, but no data regarding the possible endocrine toxicities of these compounds are available. Aim of this study was to investigate whether short-chain PFCs could jeopardize thyroid cell viability and/or interfere with the functional effect TSH.

METHODS

Fisher rat thyroid line-5 (FRTL-5) was treated with increasing concentrations of PFOA, PFOS, perfluorobutanesulfonic acid (PFBS), perfluorobutanoic acid (PFBA), pentafluoropropionic anhydride (PFPA), perfluoropentanoic acid (PFPeA) to evaluate modifications in cell viability and TSH-stimulated cAMP production.

RESULTS

Neither long nor short-chain PFCs affected cell viability (apart from PFOS 100 µM), or interfered with cAMP production.

CONCLUSIONS

The results of the present study demonstrate for the first time that short-chain PFCs have no acute cytotoxic effect on thyroid cells in vitro and that cAMP production is not modulated by any of the tested PFCs.

The cholesterol-derived metabolite dendrogenin A functionally reprograms breast adenocarcinoma and undifferentiated thyroid cancer cells

Dendrogenin A (DDA) is a tumor suppressor mammalian cholesterol-derived metabolite and a new class of ligand of the Liver X receptor (LXR), which displays tumor cell differentiation. In human MCF7 breast adenocarcinoma cells, DDA-induced cell differentiation was associated with an increased accumulation of neutral lipids and proteins found in milk indicating that DDA re-activates some functions of lactating cells. Active iodide transport occurs in the normal lactating mammary cells through the sodium/iodide symporter (NIS) and iodide (I) is secreted into milk to be used by the nursing newborn for thyroid hormones biosynthesis. In the present study, we assessed whether DDA may induce other characteristic of lactating cells such as NIS expression and iodine uptake in MCF7 breast cancer cells and extended this study to the papillary B-CPAP and undifferentiated anaplastic 8505c thyroid cancer cells. Moreover, we evaluated DDA impact on the expression of thyroid specific proteins involved in thyroid hormone biogenesis. We report here that DDA induces NIS expression in MCF7 cells and significantly increases the uptake of 131-I by acting through the LXR. In addition, DDA induces phenotypic, molecular and functional characteristics of redifferentiation in the two human thyroid carcinoma cell lines and the uptake of 131-I in the undifferentiated 8505c cells was associated with a strong expression of all the specific proteins involved in thyroid hormone biosynthesis, TSH receptor, thyroperoxidase and thyroglobulin. 131-I incorporation in the 8505c cells was stimulated by DDA as well as by the synthetic LXR ligand, GW3965. Together these data show that the re-differentiation of breast and thyroid cancer cells by DDA, is associated with the recovery of functional NIS expression and involves an LXR-dependent mechanism. These results open new avenues of research for the diagnosis of thyroid cancers as well as the development of new therapeutic approaches for radioiodine refractory thyroid cancers.

Regression of experimental NIS-expressing breast cancer brain metastases in response to radioiodide/gemcitabine dual therapy

Treating breast cancer brain metastases (BCBMs) is challenging. Na⁺/I⁻ symporter (NIS) expression in BCBMs would permit their selective targeting with radioiodide (¹³¹I⁻). We show impressive enhancement of tumor response by combining¹³¹I⁻ with gemcitabine (GEM), a cytotoxic radiosensitizer. Nude mice mammary fat-pad (MFP) tumors and BCBMs were generated with braintropic MDA-MB-231Br cells transduced with bicistronically-linked NIS and firefly luciferase cDNAs. Response was monitored in vivo via bioluminescent imaging and NIS tumor expression.¹³¹I⁻/GEM therapy inhibited MFP tumor growth more effectively than either agent alone. BCBMs were treated with: high or low-dose GEM (58 or 14.5 mg/Kg×4); ¹³¹I⁻ (1mCi or 2×0.5 mCi 7 days apart); and ¹³¹I⁻/GEM therapy. By post-injection day (PID) 25, 82-86% of controls and 78-83% of ¹³¹I⁻-treated BCBM grew, whereas 17% low-dose and 36% high-dose GEM regressed. The latter tumors were smaller than the controls with comparable NIS expression (~20% of cells). High and low-dose ¹³¹I⁻/GEM combinations caused 89% and 57% tumor regression, respectively. High-dose GEM/¹³¹I⁻ delayed tumor growth: tumors increased 5-fold in size by PID45 (controls by PID18). Although fewer than 25% of cells expressed NIS, GEM/¹³¹I⁻ caused dramatic tumor regression in NIS-transduced BCBMs. This effect was synergistic, and supports the hypothesis that GEM radiosensitizes cells to ¹³¹I⁻.

Human sodium iodide transporter gene-mediated imaging and therapy of mouse glioma, comparison between 188Re and 131I

Novel treatment options are urgently required for patients with glioma who are not effectively treated through standard therapy. Human sodium iodide symporter (hNIS) is a molecular target of certain tumors types. Compared with ¹³¹I, ¹⁸⁸Re possesses a higher energy and shorter half-life; therefore, the effects of ¹⁸⁸Re and ¹³¹I were compared in hNIS-mediated gene imaging and therapy in the present study. Recombinant human brain glioma cell line U87 was transfected with a recombinant lentiviral vector containing hNIS (U87-hNIS). U87-0 cell line transfected with blank lentivirus was prepared as a control. In vitro, the ¹⁸⁸Re and ¹³¹I uptake of U87-hNIS cells were 21.3-times and 25.9-times that of the control groups, however the excretion rate of the two nuclides was very rapid, and the half-life was only ~4 min. Sodium perchlorate inhibited hNIS-mediated ¹⁸⁸Re and ¹³¹I uptake to levels observed in the control groups. ¹⁸⁸Re and ¹³¹I were able to kill U87-hNIS cells selectively, with a survival of only 21.6 and 36.2%, respectively. U87-hNIS nude mice appeared to accumulate ¹⁸⁸Re, with a ratio of radioactivity counts between tumor and non-tumor sites of ~13.5 compared with 10.3 of ¹³¹I 1 h after radionuclide injection. In contrast with in vitro studies, U87-hNIS cells demonstrated a notable increase in ¹⁸⁸Re retention in vivo, even 24 h after ¹⁸⁸Re injection. U87-hNIS cells also exhibited increased ¹³¹I retention in vivo; however, as the time increased, ¹³¹I was rapidly released with the tumor no longer able to be imaged 24 h after ¹³¹I injection. Following treatment, U87-hNIS tumors experienced a volume reduction of 24.1%, whereas U87-0 cells demonstrated an increase of 28.8%. ¹⁸⁸Re and ¹³¹I were revealed to be effective at decreasing tumor volume compared with the control. However, ¹⁸⁸Re was significantly more potent compared with ¹³¹I (P<0.01). The present study indicated that the U87-hNIS cell line is sufficient to induce specific ¹⁸⁸Re and ¹³¹I uptake, which may kill cells in vitro and in vivo. ¹⁸⁸Re exhibited an increased retention time in vivo compared with ¹³¹I, which facilitates the imaging and therapy of U87-hNIS tumors.

Role of Krüppel-Like Factor 4 in the Maintenance of Chemoresistance of Anaplastic Thyroid Cancer

BACKGROUND

Anaplastic thyroid cancer (ATC) has a very poor prognosis due to its aggressive nature and resistance to conventional treatment. Radiotherapy and chemotherapy are not fully effective because of the undifferentiated phenotype and enhanced drug resistance of ATC. The objective of this study was to evaluate the involvement of Krüppel-like factor 4 (KLF4), a stemness-associated transcription factor, in the undifferentiated phenotype and drug resistance of ATC.

METHODS

ATC cells were compared to papillary thyroid cancer cells in drug resistance and gene expression. The effects of KLF4 knockdown in ATC cells on in vitro and in vivo drug resistance were measured. The effects of KLF4 overexpression and knockdown on ABC transporter activity were determined.

RESULTS

ATC cells, such as HTH83, 8505C, and SW1736, exhibited higher resistance to the anticancer drug paclitaxel and higher expression of KLF4 than TPC-1 papillary thyroid cancer cells. Knockdown of KLF4 expression in ATC cells increased the expression of the thyroid-specific differentiation genes, such as thyrotropin receptor, thyroid peroxidase, thyroglobulin, and sodium-iodide symporter. Knockdown of KLF4 expression in ATC cells decreased the resistance to doxorubicin and paclitaxel, and reduced ABC transporter expression. Luciferase reporter assay results showed that KLF4 overexpression increased ABCG2 promoter activity, which was abolished by KLF4 knockdown. A tumorigenicity assay showed that the combination of paclitaxel treatment and KLF4 knockdown significantly decreased tumor mass originated from HTH83 cells in mice.

CONCLUSIONS

ATC cells show high expression of KLF4, and KLF4 expression is necessary for maintaining the undifferentiated phenotype and drug resistance in vitro and in vivo. The present study identifies KLF4 as a potential therapeutic target for eliminating ATC cells.

The Sodium/Iodide Symporter (NIS): Molecular Physiology and Preclinical and Clinical Applications

Active iodide (I^-) transport in both the thyroid and some extrathyroidal tissues is mediated by the Na⁺/I^- symporter (NIS). In the thyroid, NIS-mediated I^- uptake plays a pivotal role in thyroid hormone (TH) biosynthesis. THs are key during embryonic and postembryonic development and critical for cell metabolism at all stages of life. The molecular characterization of NIS in 1996 and the use of radioactive I^- isotopes have led to significant advances in the diagnosis and treatment of thyroid cancer and provide the molecular basis for studies aimed at extending the use of radioiodide treatment in extrathyroidal malignancies. This review focuses on the most recent findings on I^- homeostasis and I^- transport deficiency-causing NIS mutations, as well as current knowledge of the structure/function properties of NIS and NIS regulatory mechanisms. We also discuss employing NIS as a reporter gene using viral vectors and stem cells in imaging, diagnostic, and therapeutic procedures.

Imaging and targeted therapy of pancreatic ductal adenocarcinoma using the theranostic sodium iodide symporter (NIS) gene

The theranostic sodium iodide symporter (NIS) gene allows detailed molecular imaging of transgene expression and application of therapeutic radionuclides. As a crucial step towards clinical application, we investigated tumor specificity and transfection efficiency of epidermal growth factor receptor (EGFR)-targeted polyplexes as systemic NIS gene delivery vehicles in an advanced genetically engineered mouse model of pancreatic ductal adenocarcinoma (PDAC) that closely reflects human disease. PDAC was induced in mice by pancreas-specific activation of constitutively active KrasG12D and deletion of Trp53. We used tumor-targeted polyplexes (LPEI-PEG-GE11/NIS) based on linear polyethylenimine, shielded by polyethylene glycol and coupled with the EGFR-specific peptide ligand GE11, to target a NIS-expressing plasmid to high EGFR-expressing PDAC. In vitro iodide uptake studies in cell explants from murine EGFR-positive and EGFR-ablated PDAC lesions demonstrated high transfection efficiency and EGFR-specificity of LPEI-PEG-GE11/NIS. In vivo 123I gamma camera imaging and three-dimensional high-resolution 124I PET showed significant tumor-specific accumulation of radioiodide after systemic LPEI-PEG-GE11/NIS injection. Administration of 131I in LPEI-PEG-GE11/NIS-treated mice resulted in significantly reduced tumor growth compared to controls as determined by magnetic resonance imaging, though survival was not significantly prolonged. This study opens the exciting prospect of NIS-mediated radionuclide imaging and therapy of PDAC after systemic non-viral NIS gene delivery.

A Novel Ideal Radionuclide Imaging System for Non-invasively Cell Monitoring built on Baculovirus Backbone by Introducing Sleeping Beauty Transposon

Sleeping Beauty (SB) transposon is an attractive tool in stable transgene integration both in vitro and in vivo; and we introduced SB transposon into recombinant sodium-iodide symporter baculovirus system (Bac-NIS system) to facilitate long-term expression of recombinant sodium-iodide symporter. In our study, two hybrid baculovirus systems (Bac-eGFP-SB-NeoR and Bac-NIS-SB-NeoR) were successfully constructed and used to infect U87 glioma cells. After G418 selection screening, the Bac-eGFP-SB-NeoR-U87 cells remained eGFP positive, at the 18^th and 196^th day post transfection (96.03 ± 0.21% and 97.43 ± 0.81%), while eGFP positive population declined significantly at 18 days in cells transfected with unmodified baculovirus construct. NIS gene expression by Bac-NIS-SB-NeoR-U87 cells was also maintained for 28 weeks as determined by radioiodine uptake assay, reverse transcription-polymerase chain reaction (RT-PCR) and Western Blot (WB) assay. When transplanted in mice, Bac-NIS-SB-NeoR-U87 cells also expressed NIS gene stably as monitored by SPECT imaging for 43 days until the tumor-bearing mice were sacrificed. Herein, we showed that incorporation of SB in Bac-NIS system (hybrid Bac-NIS-SB-NeoR) can achieve a long-term transgene expression and can improve radionuclide imaging in cell tracking and monitoring in vivo.

Treatment with Myo-Inositol and Selenium Ensures Euthyroidism in Patients with Autoimmune Thyroiditis

Clinical evidences have highlighted the efficacy of myo-inositol and selenium in the treatment of autoimmune thyroiditis. Aim of this study was to further analyze the role of myo-inositol plus selenium (Myo-Ins-Se) in restoring a normal thyroid function of Hashimoto's patients with subclinical hypothyroidism. Eighty-six patients with Hashimoto's thyroiditis having thyroid-stimulating hormone (TSH) levels between 3 and 6 mIU/L, elevated serum antithyroid peroxidase (TPOAb) and/or antithyroglobulin (TgAb), and normal free thyroxine (fT4) and free triiodothyronine (fT3) levels were enrolled in the study: one hyperthyroid subject with TSH about 0.14 μU/ml was included in this trial as a single case. Patients were assigned to receive Myo-Ins-Se. TSH, TPOAb, and TgAb levels were significantly decreased in patients treated with combined Myo-Ins-Se after 6 months of treatment. In addition, a significant fT3 and fT4 increase, along with an amelioration of their quality of life, was observed. Remarkably, TSH values of the hyperthyroid patient increased from 0.14 μU/ml up to 1.02 μU/ml, showing a complete restoration of TSH values at a normal range. In conclusion, the administration of Myo-Ins-Se is significantly effective in decreasing TSH, TPOAb, and TgAb levels, as well as enhancing thyroid hormones and personal wellbeing, therefore restoring euthyroidism in patients diagnosed with autoimmune thyroiditis.

PDGFRα Regulates Follicular Cell Differentiation Driving Treatment Resistance and Disease Recurrence in Papillary Thyroid Cancer

Dedifferentiation of follicular cells is a central event in resistance to radioactive iodine and patient mortality in papillary thyroid carcinoma (PTC). We reveal that platelet derived growth factor receptor alpha (PDGFRα) specifically drives dedifferentiation in PTC by disrupting the transcriptional activity of thyroid transcription factor-1 (TTF1). PDGFRα activation dephosphorylates TTF1 consequently shifting the localization of this transcription factor from the nucleus to the cytoplasm. TTF1 is required for follicular cell development and disrupting its function abrogates thyroglobulin production and sodium iodide transport. PDGFRα also promotes a more invasive and migratory cell phenotype with a dramatic increase in xenograft tumor formation. In patient tumors we confirm that nuclear TTF1 expression is inversely proportional to PDGFRα levels. Patients exhibiting PDGFRα at time of diagnosis are three times more likely to exhibit nodal metastases and are 18 times more likely to recur within 5years than those patients lacking PDGFRα expression. Moreover, high levels of PDGFRα and low levels of nuclear TTF1 predict resistance to radioactive iodine therapy. We demonstrate in SCID xenografts that focused PDGFRα blockade restores iodide transport and decreases tumor burden by >50%. Focused PDGFRα inhibitors, combined with radioactive iodine, represent an additional avenue for treating patients with aggressive variants of PTC.

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

PURPOSE

Human 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.

METHODS

HeLa 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.

RESULTS

cAMP-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.

CONCLUSIONS

These 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.

Inhibition of miR-146b expression increases radioiodine-sensitivity in poorly differential thyroid carcinoma via positively regulating NIS expression

Dedifferentiated thyroid carcinoma (DTC) with the loss of radioiodine uptake (RAIU) is often observed in clinical practice under radioiodine therapy, indicating the challenge for poor prognosis. MicroRNA (miRNA) has emerged as a promising therapeutic target in many diseases; yet, the role of miRNAs in RAIU has not been generally investigated. Based on recent studies about miRNA expression in papillary or follicular thyroid carcinomas, the expression profiles of several thyroid relative miRNAs were investigated in one DTC cell line, derived from normal DTC cells by radioiodine treatment. The top candidate miR-146b, with the most significant overexpression profiles in dedifferentiated cells, was picked up. Further research found that miR-146b could be negatively regulated by histone deacetylase 3 (HDAC3) in normal cells, indicating the correlation between miR-146b and Na(+)/I(-) symporter (NIS)-mediated RAIU. Fortunately, it was confirmed that miR-146b could regulate NIS expression/activity; what is more important, miR-146b interference would contribute to the recovery of radioiodine-sensitivity in dedifferentiated cells via positively regulating NIS. In the present study, it was concluded that NIS-mediated RAIU could be modulated by miR-146b; accordingly, miR-146b might serve as one of targets to enhance efficacy of radioactive therapy against poorly differential thyroid carcinoma (PDTC).

Apical iodide efflux in thyroid

Thyroid follicular epithelial cells produce thyroxine (T4) and its physiologically active derivative, 3,3',5-triiodothyronine (T3), hormones that regulate critical developmental and metabolic functions. In order for the thyroid to form hormone precursor, iodide, the defining element in thyroid hormone, must cross both blood-facing and luminal sides of the follicular epithelium. The pathway for uptake from blood is well understood, but the mechanism(s) that enable iodide to cross the luminally facing apical membrane remain obscure. This chapter considers the physiological properties of several molecularly characterized anion transport proteins, all of which potentially contribute to the overall mechanism of apical iodide efflux.

In vivo molecular imaging and radionuclide (131I) therapy of human nasopharyngeal carcinoma cells transfected with a lentivirus expressing sodium iodide symporter

INTRODUCTION

Despite recent improvements in the survival rates for nasopharyngeal carcinoma (NPC), novel treatment strategies are required to improve distant metastasis-free survival. The sodium iodine symporter (NIS) gene has been applied for in vivo imaging and cancer therapy. In this study, we examined the potential of NIS gene therapy as a therapeutic approach in NPC by performing non-invasive imaging using 125I and 131I therapy in vivo.

METHODS

We constructed a lentiviral vector expressing NIS and enhanced green fluorescent protein (EGFP) under the control of the human elongation factor-1α (EF1α) promoter, and stably transfected the vector into CNE-2Z NPC cells to create CNE-2Z-NIS cells. CNE-2Z and CNE-2Z-NIS tumor xenografts were established in nude mice; 125I uptake, accumulation and efflux were measured using micro-SPECT/CT imaging; the therapeutic effects of treatment with 131I were assessed over 25 days by measuring tumor volume and immunohistochemical staining of the excised tumors.

RESULTS

qPCR, immunofluorescence and Western blotting confirmed that CNE-2Z-NIS cells expressed high levels of NIS mRNA and protein. CNE-2Z-NIS cells and xenografts took up and accumulated significantly more 125I than CNE-2Z cells and xenografts. In vitro, 131I significantly reduced the clonogenic survival of CNE-2Z-NIS cells. In vivo, 131I effectively inhibited the growth of CNE-2Z-NIS xenografts. At the end of 131I therapy, CNE-2Z-NIS xenograft tumor cells expressed higher levels of NIS and caspase-3 and lower levels of Ki-67.

CONCLUSION

Lentiviruses effectively delivered and mediated long-lasting expression of NIS in CNE-2Z cells which enabled uptake and accumulation of radioisotopes and provided a significant therapeutic effect in an in vivo model of NPC. NIS-mediated radioiodine treatment merits further investigation as a potentially effective, low toxicity therapeutic strategy for NPC.

Experimental study of nasopharyngeal carcinoma radionuclide imaging and therapy using transferred human sodium/iodide symporter gene

Purpose

The aim of this study was to design a method of radionuclide for imaging and therapy of nasopharyngeal carcinoma (NPC) using the transferred human sodium/iodide symporter (hNIS) gene.

Methods

A stable NPC cell line expressing hNIS was established (CNE-2-hNIS). After ¹³¹I treatment, we detected proliferation and apoptosis of NPC cells, both in vitro and vivo. In vivo, the radioactivity of different organs of nude mice was counted and ^99mTc imaging using SPECT was performed. The apparent diffusion coefficient (ADC) value changes of tumor xenografts were observed by diffusion-weighted magnetic resonance imaging (DW-MRI) within 6–24 days of ¹³¹I treatment. The correlation of ADC changes with apoptosis and proliferation was investigated. Post-treatment expression levels of P53, Bax, Bcl-2, Caspase-3, and Survivin proteins were detected by western blotting.

Results

¹³¹I uptake was higher in CNE-2-hNIS than in CNE-2 cells. The proliferation and apoptosis rate decreased and increased respectively both in vitro and vivo in the experimental group after ¹³¹I treatment. The experimental group tumors accumulated ^99mTc in vivo, leading to a good visualization by SPECT. DW-MRI showed that ADC values increased in the experimental group 6 days after treatment, while ADC values were positively and negatively correlated with the apoptotic and Ki-67 proliferation indices, respectively. After treatment, CNE-2-hNIS cells up-regulated the expression of P53 and Survivin proteins and activated Caspase-3, and down-regulated the expression of Bcl-2 proteins.

Conclusions

The radionuclide imaging and therapy technique for NPC hNIS-transfected cell lines can provide a new therapy strategy for monitoring and treatment of NPC.

All-trans-retinoic acid promotes iodine uptake via up- regulating the sodium iodide symporter in medullary thyroid cancer stem cells

Recently, the main therapy of medullary thyroid cancer (MTC) is surgical, but by which way there is a poor prognosis with a mean survival of only 5 years. In some cases, some researchers found that it is the medullary thyroid cancer stem cells (MTCSCs) that cause metastasis and recurrence. This study aimed to eradicate MTCSCs through administration of all-trans-retinoic acid (ATRA). Here we demonstrate that MTCSCs possess stem- like properties in serum-free medium. The ABCG2, OCT4 and sodium iodide symporter (NIS) were changed by ATRA. Additionally, we found that ATRA can increase the expression of NIS in vivo. All the data suggested that ATRA could increase the iodine uptake of MTCSCs through NIS.

TAS2R bitter taste receptors regulate thyroid function

Dysregulation of thyroid hormones triiodothyronine and thyroxine (T3/T4) can impact metabolism, body composition, and development. Thus, it is critical to identify novel mechanisms that impact T3/T4 production. We found that type 2 taste receptors (TAS2Rs), which are activated by bitter-tasting compounds such as those found in many foods and pharmaceuticals, negatively regulate thyroid-stimulating hormone (TSH)-dependent Ca(2+) increases and TSH-dependent iodide efflux in thyrocytes. Immunohistochemical Tas2r-dependent reporter expression and real-time PCR analyses reveal that human and mouse thyrocytes and the Nthy-Ori 3-1 human thyrocyte line express several TAS2Rs. Five different agonists for thyrocyte-expressed TAS2Rs reduced TSH-dependent Ca(2+) release in Nthy-Ori 3-1 cells, but not basal Ca(2+) levels, in a dose-dependent manner. Ca(2+) responses were unaffected by 6-n-propylthiouracil, consistent with the expression of an unresponsive variant of its cognate receptor, TAS2R38, in these cells. TAS2R agonists also inhibited basal and TSH-dependent iodide efflux. Furthermore, a common TAS2R42 polymorphism is associated with increased serum T4 levels in a human cohort. Our findings indicate that TAS2Rs couple the detection of bitter-tasting compounds to changes in thyrocyte function and T3/T4 production. Thus, TAS2Rs may mediate a protective response to overingestion of toxic materials and could serve as new druggable targets for therapeutic treatment of hypo- or hyperthyroidism.

Anoctamin-1/TMEM16A is the major apical iodide channel of the thyrocyte

Iodide is captured by thyrocytes through the Na(+)/I(-) symporter (NIS) before being released into the follicular lumen, where it is oxidized and incorporated into thyroglobulin for the production of thyroid hormones. Several reports point to pendrin as a candidate protein for iodide export from thyroid cells into the follicular lumen. Here, we show that a recently discovered Ca(2+)-activated anion channel, TMEM16A or anoctamin-1 (ANO1), also exports iodide from rat thyroid cell lines and from HEK 293T cells expressing human NIS and ANO1. The Ano1 mRNA is expressed in PCCl3 and FRTL-5 rat thyroid cell lines, and this expression is stimulated by thyrotropin (TSH) in rat in vivo, leading to the accumulation of the ANO1 protein at the apical membrane of thyroid follicles. Moreover, ANO1 properties, i.e., activation by intracellular calcium (i.e., by ionomycin or by ATP), low but positive affinity for pertechnetate, and nonrequirement for chloride, better fit with the iodide release characteristics of PCCl3 and FRTL-5 rat thyroid cell lines than the dissimilar properties of pendrin. Most importantly, iodide release by PCCl3 and FRTL-5 cells is efficiently blocked by T16Ainh-A01, an ANO1-specific inhibitor, and upon ANO1 knockdown by RNA interference. Finally, we show that the T16Ainh-A01 inhibitor efficiently blocks ATP-induced iodide efflux from in vitro-cultured human thyrocytes. In conclusion, our data strongly suggest that ANO1 is responsible for most of the iodide efflux across the apical membrane of thyroid cells.

Resveratrol inhibits sodium/iodide symporter gene expression and function in rat thyroid cells

Resveratrol is a polyphenol found in grapes and berries that has antioxidant, antiproliferative and anti-inflammatory properties. For these reasons, it is available as a dietary supplement, and it is under investigation in several clinical trials. Few data are available regarding the effects of resveratrol on thyroid function. A previous study showed that resveratrol transiently increases iodide influx in FRTL-5 rat thyroid cells. Indeed, this increase arises after short treatment times (6–12 h), and no further effects are seen after 24 h. The aim of the present study was to investigate the effects of resveratrol on iodide uptake and sodium/iodide symporter expression in thyroid cells after longer times of treatment. For this purpose, the effects of resveratrol were evaluated both in vitro and in vivo using the rat thyroid FRTL-5 cell line and Sprague-Dawley rats, respectively. In FRTL-5 cells, resveratrol decreased the sodium/iodide symporter RNA and protein expression as a function of time. Furthermore, resveratrol decreased cellular iodide uptake after 48 h of treatment. The inhibitory effect of resveratrol on iodide uptake was confirmed in vivo in Sprague-Dawley rats. This study demonstrates that with longer-term treatment, resveratrol is an inhibitor of sodium/iodide symporter gene expression and function in the thyroid. These data suggest that resveratrol can act as a thyroid disruptor, which indicates the need for caution as a supplement and in therapeutic use.

Radioiodine therapy for castration-resistant prostate cancer following prostate-specific membrane antigen promoter-mediated transfer of the human sodium iodide symporter

Radioiodine therapy, the most effective form of systemic radiotherapy available, is currently useful only for thyroid cancer because of the thyroid-specific expression of the human sodium iodide symporter (hNIS). Here, we explore the efficacy of a novel form of gene therapy using prostate-specific membrane antigen (PSMA) promoter-mediated hNIS gene transfer followed by radioiodine administration for the treatment of castration-resistant prostate cancer (CRPC). The androgen-dependent C33 LNCaP cell line and the androgen-independent C81 LNCaP cell line were transfected by adenovirus. PSMA promoter-hNIS (Ad.PSMApro-hNIS) or adenovirus.cytomegalovirus–hNIS containing the cytomegalovirus promoter (Ad.CMV-hNIS) or a control virus. The iodide uptake was measured in vitro. The in vivo iodide uptake by C81 cell xenografts in nude mice injected with an adenovirus carrying the hNIS gene linked to PSMA and the corresponding tumor volume fluctuation were assessed. Iodide accumulation was shown in different LNCaP cell lines after Ad.PSMApro-hNIS and Ad.CMV-hNIS infection, but not in different LNCaP cell lines after adenovirus.cytomegalovirus (Ad.CMV) infection. At each time point, higher iodide uptake was shown in the C81 cells infected with Ad.PSMApro-hNIS than in the C33 cells (P < 0.05). An in vivo animal model showed a significant difference in ¹³¹I radioiodine uptake in the tumors infected with Ad.PSMApro-hNIS, Ad.CMV-hNIS and control virus (P < 0.05) and a maximum reduction of tumor volume in mice infected with Ad.PSMApro-hNIS. These results show prostate-specific expression of the hNIS gene delivered by the PSMA promoter and effective radioiodine therapy of CRPC by the PSMA promoter-driven hNIS transfection.

Theranostic studies of human sodium iodide symporter imaging and therapy using 188Re: a human glioma study in mice

Objective

To investigate the role of ¹⁸⁸Re in human sodium iodide symporter (hNIS) theranostic gene-mediated human glioma imaging and therapy in model mice.

Methods

The human glioma cell line U87 was transfected with recombinant lentivirus encoding the hNIS gene under the control of cytomegalovirus promoter (U87-hNIS). The uptake and efflux of ¹⁸⁸Re were determined after incubating the cells with ¹⁸⁸Re. ¹⁸⁸Re uptake experiments in the presence of various concentrations of sodium perchlorate were carried out. In vitro cell killing tests with ¹⁸⁸Re were performed. U87-hNIS mediated ¹⁸⁸Re distribution, imaging and therapy in nude mice were also tested.

Results

U87-hNIS cell line was successfully established. The uptake of ¹⁸⁸Re in U87-hNIS cells increased up to 26-fold compared to control cells, but was released rapidly with a half-life of approximately 4 minutes. Sodium perchlorate reduced hNIS-mediated ¹⁸⁸Re uptake to levels of control cell lines. U87-hNIS cells were selectively killed following exposure to ¹⁸⁸Re, with a survival of 21.4%, while control cells had a survival of 92.1%. Unlike in vitro studies, U87-hNIS tumor showed a markedly increased ¹⁸⁸Re retention even 48 hours after ¹⁸⁸Re injection. In the therapy study, there was a significant difference in tumor size between U87-hNIS mice (317±67 mm³) and control mice (861±153 mm³) treated with ¹⁸⁸Re for 4 weeks (P<0.01).

Conclusion

The results indicate that inserting the hNIS gene into U87 cells is sufficient to induce specific ¹⁸⁸Re uptake, which has a cell killing effect both in vitro and in vivo. Moreover, our study, based on the function of hNIS as a theranostic gene allowing noninvasive imaging of hNIS expression by ¹⁸⁸Re scintigraphy, provides detailed characterization of in vivo vector biodistribution and level, localization, essential prerequisites for precise planning and monitoring of clinical gene therapy that aims to individualize gene therapy concept.

Thyrotropin in the development and management of differentiated thyroid cancer

Thyrotropin (TSH) is the major regulator and growth factor of the thyroid. TSH may be important in the development of human thyroid cancer, with both suggestive animal models and clinical evidence, although definitive proof is still required. Applications for TSH in thyroid cancer management include TSH stimulation of radioiodine uptake, enhancement of biochemical monitoring through thyroglobulin measurement, and long-term suppression of TSH with supraphysiologic levothyroxine. This review synthesizes current knowledge of TSH in both the development and management of differentiated thyroid cancer.

Canonical transient receptor potential channel 2 (TRPC2): old name-new games. Importance in regulating of rat thyroid cell physiology

In addition to the TSH-cyclic AMP signalling pathway, calcium signalling is of crucial importance in thyroid cells. Although the importance of calcium signalling has been thoroughly investigated for several decades, the nature of the calcium channels involved in signalling is unknown. In a recent series of investigations using the well-studied rat thyroid FRTL-5 cell line, we showed that these cells exclusively express the transient receptor potential canonical 2 (TRPC2) channel. Our results suggested that the TRPC2 channel is of significant importance in regulating thyroid cell function. These investigations were the first to show that thyroid cells express a member of the TRPC family of ion channels. In this review, we will describe the importance of the TRPC2 channel in regulating TSH receptor expression, thyroglobulin maturation, intracellular calcium and iodide homeostasis and that the channel also regulates thyroid cell proliferation.

Potential Usefulness of Baculovirus-Mediated Sodium-Iodide Symporter Reporter Gene as Non-Invasively Gene Therapy Monitoring in Liver Cancer Cells: An In Vitro Evaluation

Primary liver cancer has one of the highest mortality rates of all cancers, and the main current treatments have a poor prognosis. This study aims to examine the efficiency of baculovirus vectors for transducing target gene into liver cancer cells and to evaluate the feasibility of using baculovirus vectors to deliver the sodium-iodide symporter (NIS) gene as a reporter gene through co-vector administration approach to monitor the expression of the target therapeutic gene in liver cancer gene therapy. We constructed (green fluorescent protein) GFP- and NIS-expressing baculovirus vectors (Bac-GFP and Bac-NIS), and measured the baculovirus transduction efficiency in HepG2 cells and other tumor cells (A549, SW1116 and 8505C), and it showed that the transduction efficiency and target gene expression level rose with increasing viral multiplicity of infection (MOI) in HepG2 cells, and HepG2 cells had a significantly higher transduction efficiency (60.8% at MOI = 200) than other tumor cells. Moreover, the baculovirus transduction was not cytotoxic to HepG2 cells at a higher MOI (MOI = 400). We also performed dynamic iodide uptake trials, and found that Bac-NIS-transduced HepG2 cells exhibited efficient iodide uptake which could be inhibited by sodium perchlorate (NaClO4). And we measured the correlation of fluorescent intensities and 125 I uptake amount in HepG2 cells after co-vector administration with Bac-NIS and Bac-GFP at different MOIs, and found a high correlation coefficient ( r2 = 0.8447), which provides a good basis for successfully evaluating the feasibility of baculovirus-mediated NIS reporter gene monitoring target gene expression in liver cancer therapy. Therefore, this study indicates that baculovirus vector is a potential vehicle for delivering therapeutic genes in studying liver cancer cells. And it is feasible to use a baculovirus vector to deliver NIS gene as a reporter gene to monitor the expression of target genes. It therefore provides an effective approach and a good basis for future baculovirus-mediated therapeutic gene delivering or therapeutic gene expression monitoring in liver cancer cells studies.

Cooperation of histone deacetylase inhibitors SAHA and valproic acid in promoting sodium/iodide symporter expression and function in rat Leydig testicular carcinoma cells

The presence of the sodium/iodide symporter (NIS) is the prerequisite for the use of the radioiodine in the treatment of thyroid cancer. Thus, stimulators of NIS expression and function are currently investigated in cellular models of various human malignancies, also including extrathyroid cancers. In this study, we analyzed the effects of the histone deacetylase inhibitors (HDACi), suberoylanilide hydroxamic acid (SAHA) and valproic acid (VPA), on NIS expression and function in rat Leydig testicular carcinoma cells (LC540). LC540 cells were exposed to SAHA 3 μM and VPA 3 mM (alone and in combination), and cell viability evaluated by MTT assay and cell counting, NIS mRNA and protein levels by using, respectively, real-time RT-PCR and western blotting. NIS function was evaluated by iodide uptake assay. We found that both HDACi were able to stimulate the transcription of NIS gene, but not its protein expression, while the association of SAHA and VPA increased both NIS transcript and protein levels, resulting in significant sixfold enhancement of radioiodine uptake capacity of LC540 cells. These data demonstrate the presence of an epigenetic control of NIS expression in Leydig tumor cells, suggesting the possibility to use the combination of these two HDACi for a radioiodine-based treatment of these malignancies.

The Na+/I- symporter (NIS): mechanism and medical impact

The Na(+)/I(-) symporter (NIS) is the plasma membrane glycoprotein that mediates active I(-) transport in the thyroid and other tissues, such as salivary glands, stomach, lactating breast, and small intestine. In the thyroid, NIS-mediated I(-) uptake plays a key role as the first step in the biosynthesis of the thyroid hormones, of which iodine is an essential constituent. These hormones are crucial for the development of the central nervous system and the lungs in the fetus and the newborn and for intermediary metabolism at all ages. Since the cloning of NIS in 1996, NIS research has become a major field of inquiry, with considerable impact on many basic and translational areas. In this article, we review the most recent findings on NIS, I(-) homeostasis, and related topics and place them in historical context. Among many other issues, we discuss the current outlook on iodide deficiency disorders, the present stage of understanding of the structure/function properties of NIS, information gleaned from the characterization of I(-) transport deficiency-causing NIS mutations, insights derived from the newly reported crystal structures of prokaryotic transporters and 3-dimensional homology modeling, and the novel discovery that NIS transports different substrates with different stoichiometries. A review of NIS regulatory mechanisms is provided, including a newly discovered one involving a K(+) channel that is required for NIS function in the thyroid. We also cover current and potential clinical applications of NIS, such as its central role in the treatment of thyroid cancer, its promising use as a reporter gene in imaging and diagnostic procedures, and the latest studies on NIS gene transfer aimed at extending radioiodide treatment to extrathyroidal cancers, including those involving specially engineered NIS molecules.

American Thyroid Association Guide to investigating thyroid hormone economy and action in rodent and cell models

BACKGROUND

An in-depth understanding of the fundamental principles that regulate thyroid hormone homeostasis is critical for the development of new diagnostic and treatment approaches for patients with thyroid disease.

SUMMARY

Important clinical practices in use today for the treatment of patients with hypothyroidism, hyperthyroidism, or thyroid cancer are the result of laboratory discoveries made by scientists investigating the most basic aspects of thyroid structure and molecular biology. In this document, a panel of experts commissioned by the American Thyroid Association makes a series of recommendations related to the study of thyroid hormone economy and action. These recommendations are intended to promote standardization of study design, which should in turn increase the comparability and reproducibility of experimental findings.

CONCLUSIONS

It is expected that adherence to these recommendations by investigators in the field will facilitate progress towards a better understanding of the thyroid gland and thyroid hormone dependent processes.

Impact of Metformin and compound C on NIS expression and iodine uptake in vitro and in vivo: a role for CRE in AMPK modulation of thyroid function

BACKGROUND

Although adenosine monophosphate activated protein kinase (AMPK) plays a crucial role in energy metabolism, a direct effect of AMPK modulation on thyroid function has only recently been reported, and much of its function in the thyroid is currently unknown. The aim of this study was to investigate the mechanism of AMPK modulation in iodide uptake. Furthermore, we wanted to investigate the potential of the AMPK inhibitor compound C as an enhancer of iodide uptake by thyrocytes.

METHODS

The in vitro and in vivo effects of AMPK modulation on sodium-iodide symporter (NIS) protein levels and iodide uptake were examined in follicular rat thyroid cell-line cells and C57Bl6/J mice. Activation of AMPK by metformin resulted in a strong reduction of iodide uptake (up to sixfold with 5 mM metformin after 96 h) and NIS protein levels in vitro, whereas AMPK inhibition by compound C not only stimulated iodide uptake but also enhanced NIS protein levels both in vitro (up to sevenfold with 1 μM compound C after 96 h) and in vivo (1.5-fold after daily injections with 20 mg/kg for 4 days). We investigated the regulation of NIS expression by AMPK using a range of promoter constructs consisting of either the NIS promoter or isolated CRE (cAMP response element) and NF-κB elements, which are present within the NIS promoter.

RESULTS

Metformin reduced NIS promoter activity (0.6-fold of control), whereas compound C stimulated its activity (3.4-fold) after 4 days. This largely coincides with CRE activation (0.6- and 3.0-fold). These experiments show that AMPK exerts its effects on iodide uptake, at least partly, through the CRE element in the NIS promoter. Furthermore, we have used AMPK-alpha1 knockout mice to determine the long-term effects of AMPK inhibition without chemical compounds. These mice have a less active thyroid, as shown by reduced colloid volume and reduced responsiveness to thyrotropin.

CONCLUSION

NIS expression and iodine uptake in thyrocytes can be modulated by metformin and compound C. These compounds exert their effect by modulation of AMPK, which, in turn, regulates the activation of the CRE element in the NIS promoter. Overall, this suggests that the use of AMPK modulating compounds may be useful for the enhancement of iodide uptake by thyrocytes, which could be useful for the treatment of thyroid cancer patients with radioactive iodine.

Local thyroid renin-angiotensin system in experimental breast cancer

An association between breast cancer and thyroid dysfunction exists although the underlying mechanisms remain to be elucidated. Numerous studies have characterized the role of thyroid hormones in controlling the synthesis and secretion of renin-angiotensin system (RAS) components, but little information is available on the putative role of the local RAS on thyroid function.

AIMS

Here we analyze several soluble and membrane-bound RAS-regulating aminopeptidase activities in thyroid gland from rats with mammary tumors and the relationship with the circulating levels of thyroid stimulating hormone (TSH) and free thyroxin (fT4).

MAIN METHODS

We analyze soluble and membrane-bound RAS-regulating aminopeptidase activities fluorometrically using their corresponding aminoacyl-β-naphthylamide as the substrate.

KEY FINDINGS

We have found in rats with mammary tumors a concomitant change of thyroid RAS-regulating enzymes and thyroid hormone production.

SIGNIFICANCE

We suggest that existence of alterations in the regulatory mechanisms mediated by the angiotensins of the local tissue RAS as a consequence of the carcinogenic process which could act alone or in combination with alterations at a higher level of regulation such as the hypothalamus-pituitary axis.

Functional coupling of TRPC2 cation channels and the calcium-activated anion channels in rat thyroid cells: implications for iodide homeostasis

The initial step in a synthesis of thyroid hormones is the uptake of iodide from the circulation. Iodide (I(-)) is transported into thyroid cells via a Na(+)/I(-) symporter (NIS), which is electrogenic and thus sensitive to alterations in membrane potential (V(m)). I(-) is then released to the lumen of thyroid follicles where the hormones are synthesised and stored. The mechanisms of I(-) release to follicle lumen are poorly characterised. Our whole-cell voltage clamp recordings revealed the presence of a Ca(2+) activated Cl(-) current (CaCC) in Fisher rat thyroid cell line 5 (FRTL-5). Transcripts of anoctamin 1 (ANO1) and anoctamin 10 (ANO10), putative molecular constituents of CaCC, were detected. The anion channels underlying CaCC are highly permeable to I(-). Both niflumic acid (NFA) and 2-aminoethyl diphenylborinate (2-APB), antagonists of CaCC and transient receptor potential channels, respectively, inhibited CaCC. Canonical transient receptor potential channel 2 (TRPC2) is the only TRPC member present in FRTL-5 cells. The activation rate of CaCC was markedly slower in shTRPC2 knock-down cells, indicating that Ca(2+) entry via TRPC2 contributes to CaCC activation. The uptake of iodide was enhanced and the resting V(m) was more depolarised in TRPC2 knock-down cells. We suggest that the interplay between TRPC2 and ANO1 may have dual effects on iodide transport, modulating I(-) release via ANO channels and I(-) uptake via the V(m) sensitive NIS.

Study on molecular imaging and radionuclide therapy of human nasopharyngeal carcinoma cells transfected with baculovirus-mediated sodium/iodine symporter gene

The non-invasive imaging and radiotherapy by sodium/iodine symporter (NIS) gene transfer have been widely used for many experiments and some clinical studies. Baculovirus is an efficient tool for gene delivery into mammalian cells in vitro and in vivo. However, the applications of NIS and/or baculovirus in nasopharyngeal carcinoma (NPC) cells have not been reported yet. In this study, two recombinant baculoviruses expressing, respectively, NIS and green fluorescent protein (GFP), both under the control of the cytomegalovirus promoter (Bac-NIS and Bac-GFP) were successfully constructed. The infection efficiency and GFP fluorescence intensity of the human NPC cell line CNE-2Z infected by Bac-GFP at different setting of multiplicity of infection (MOI) were determined by flow cytometry. NIS protein expression was detected by indirect immunofluorescence. The 125I uptake and efflux of infected CNE-2Z cells by Bac-NIS were measured by a γ-counter. The cytotoxicity of baculovirus and sodium butyrate and inhibition of iodine uptake by NaClO4 were examined. The radioactivity and GFP fluorescence intensity in co-infected CNE-2Z cells by Bac-NIS and Bac-GFP were measured. Cell colony formation tests were conducted to evaluate the killing effect of Bac-NIS-mediated 131I. Based on the results, the transduction efficiency of Bac-GFP at the MOI of 200 or 400 reached 91.16 and 94.79%, respectively. NIS protein was expressed accurately on transfected CNE-2Z cell membranes and performed its normal function in iodine transport. Baculovirus had hardly any cytotoxic effects on infected cells, while relatively high concentration of sodium butyrate generated cytotoxicity. The correlation coefficient between the GFP fluorescence intensity and radioactivity in co-infected CNE-2Z cells was 0.917. Treatment coupled Bac-NIS with 131I killed the infected tumour cells dramatically in vitro. These results suggest that baculovirus is an effective vector of the gene delivery into CNE-2Z cells and NIS-mediated iodine transport is a potential approach for molecular imaging and radionuclide therapy of NPC.

Baculovirus as an ideal radionuclide reporter gene vector: a new strategy for monitoring the fate of human stem cells in vivo

PURPOSE

Radionuclide reporter gene imaging holds promise for non-invasive monitoring of transplanted stem cells. Thus, the feasibility of utilizing recombinant baculoviruses carrying the sodium iodide symporter (NIS) reporter gene in monitoring stem cell therapy by radionuclide imaging was explored in this study.

METHODS

Recombinant baculoviruses carrying NIS and green fluorescent protein (GFP) reporter genes (Bac-NIS and Bac-GFP) were constructed and used to infect human induced pluripotent stem cells (hiPSCs), human embryonic stem cells (hESCs) and human umbilical cord blood mesenchymal stem cells (hUCB-MSCs). Infection efficiency, total fluorescence intensity and duration of transgene expression were determined by flow cytometry. Cytotoxicity/proliferative effects of baculovirus on hUCB-MSCs were assessed using CCK-8 assays. ¹²⁵I uptake and perchlorate inhibition assays were performed on Bac-NIS-infected hUCB-MSCs. Radionuclide imaging of mice transplanted with Bac-NIS-infected hUCB-MSCs was performed by NanoSPECT/CT imaging.

RESULTS

Infection efficiencies of recombinant baculovirus in hESCs, hiPSCs and hUCB-MSCs increased with increasing MOIs (27.3%, 35.8% and 95.6%, respectively, at MOI = 800). Almost no cytotoxicity and only slight effects on hUCB-MSCs proliferation were observed. Obvious GFP expression (40.6%) remained at 8 days post-infection. The radioiodide was functionally accumulated by NIS gene products and specifically inhibited by perchlorate (ClO₄⁻). Radioiodide uptake, peaking at 30 min and gradually decreasing over time, significantly correlated with hUCB-MSCs cell number (R² = 0.994). Finally, radionuclide imaging showed Bac-NIS-infected hUCB-MSCs effectively accumulated radioiodide in vivo, which gradually weakened over time.

CONCLUSION

Baculovirus as transgenic vector of radionuclide reporter gene imaging technology is a promising strategy for monitoring stem cell transplantation therapy.

Sodium/iodide symporter is expressed in the majority of seminomas and embryonal testicular carcinomas

Testicular cancer is the most frequent cancer in young men. The large majority of patients have a good prognosis, but in a small group of tumors, the current treatments are not effective. Radioiodine is routinely used in the treatment of thyroid cancer and is currently investigated as a potential therapeutic tool even for extra-thyroid tumors able to concentrate this radioisotope. Expression of Na(+)/I(-) symporter (NIS (SLC5A5)), the glycoprotein responsible for iodide transport, has been demonstrated in normal testicular tissue. In this study, we analyzed NIS expression in a large series of testicular carcinomas. Our retrospective series included 107 patients operated for testicular tumors: 98 typical seminomas, six embryonal carcinomas, one mixed embryonal choriocarcinoma, and two Leydig cells tumors. Expression and regulation of NIS mRNA and protein levels were also investigated in human embryonal testicular carcinoma cells (NTERA) by real-time RT-PCR and western blotting respectively. Immunohistochemical analysis showed the presence of NIS in the large majority of seminomas (90/98) and embryonal carcinomas (5/7) of the testis but not in Leydig cell carcinomas. Expression of NIS protein was significantly associated with lymphovascular invasion. In NTERA cells treated with the histone deacetylase inhibitors SAHA and valproic acid, a significant increase in NIS mRNA (about 60- and 30-fold vs control, P<0.001 and P<0.01 respectively) and protein levels, resulting in enhanced ability to uptake radioiodine, was observed. Finally, NIS expression in testicular tumors with the more aggressive behavior is of interest for the potential use of targeting NIS to deliver radioiodine in malignant cells.