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

Measurements of Iodination in Thyroglobulin: A Step Toward the Next Generation of Thyroid Cancer Monitoring

Thyroglobulin (Tg) is a 330-kDa homodimeric protein that that is the prohormone of thyroid hormones triiodothyronine (T3) and thyroxine (T4). The most critical steps of thyroid hormone synthesis by Tg are iodination and fusion of specific tyrosine residues that are in close proximity to each other in the folded Tg protein. The degree of Tg iodination has been studied widely to determine if it is correlated with thyroid autoimmune disease with mixed results, but these efforts have been limited by the lack of an effective quantitative technique. Simultaneously, the treatment of thyroid cancer has undergone a shift toward partial thyroidectomies, thus undermining the value of Tg measurements. A possible alternative to established monitoring techniques is measurement of Tg iodination states as it has been shown that tumor-derived Tg has significantly lower iodine content. Such measurements require a thorough understanding of normal iodination status. In this study, state-of-the-art liquid chromatography-tandem mass spectrometry (LC-MS/MS) instrumentation is used to perform bottom-up proteomics experiments and identify iodinated residues within commercially available Tg. Using this technique, sequence coverages greater than 90% were achieved, which resulted in identification of previously identified and novel hormone synthesis and donor sites. Based on the results of these discovery experiments, 5 iodination sites were selected for targeted quantitative LC-MS/MS measurements, which suggested that hormone synthesis occurs predominantly at Y24 and Y2766. The results presented herein lay the foundation for routine measurements of iodinated residues, which has the potential to overcome the limitations of current monitoring techniques and benefit patient care.

An Orally Efficacious Thyrotropin Receptor Ligand Inhibits Growth and Metastatic Activity of Thyroid Cancers

CONTEXT

Thyroid-stimulating hormone (or thyrotropin) receptor (TSHR) could be a selective target for small molecule ligands to treat thyroid cancer (TC).

OBJECTIVE

We report a novel, orally efficacious ligand for TSHR that exhibits proliferation inhibitory activity against human TC in vitro and in vivo, and inhibition of metastasis in vivo.

METHODS

A35 (NCATS-SM4420; NCGC00241808) was selected from a sublibrary of >200 TSHR ligands. Cell proliferation assays including BrdU incorporation and WST-1, along with molecular docking studies were done. In vivo activity of A35 was assessed in TC cell-derived xenograft (CDX) models with immunocompromised (NSG) mice. Formalin-fixed, paraffin-embedded sections of tumor and lung tissues were observed for the extent of cell death and metastasis.

RESULTS

A35 was shown to stimulate cAMP production in some cell types by activating TSHR but not in TC cells, MDA-T32, and MDA-T85. A35 inhibited proliferation of MDA-T32 and MDA-T85 in vitro and in vivo, and pulmonary metastasis of MDA-T85F1 in mice. In vitro, A35 inhibition of proliferation was reduced by a selective TSHR antagonist. Inhibition of CDX tumor growth without decreases in mouse weights and liver function showed A35 to be efficacious without apparent toxicity. Lastly, A35 reduced levels of Ki67 in the tumors and metastatic markers in lung tissues.

CONCLUSION

We conclude that A35 is a TSHR-selective inhibitor of TC cell proliferation and metastasis, and suggest that A35 may be a promising lead drug candidate for the treatment of differentiated TC in humans.

PET Imaging of Differentiated Thyroid Cancer with TSHR-Targeted [89Zr]Zr-TR1402

Thyroid cancer is the most common endocrine cancer, with differentiated thyroid cancers (DTCs) accounting for 95% of diagnoses. While most DTC patients are diagnosed and treated with radioiodine (RAI), up to 20% of DTC patients become RAI refractory (RAI-R). RAI-R patients have significantly reduced survival rates compared to patients who remain RAI-avid. This study explores [89Zr]Zr-TR1402 as a thyroid-stimulating hormone receptor (TSHR)-targeted PET radiopharmaceutical for DTC. [89Zr]Zr-TR1402 was synthesized with a molar activity of 25.9 MBq/nmol by conjugating recombinant human TSH (rhTSH) analogue TR1402 to chelator p-SCN-Bn-deferoxamine (DFO) in a molar ratio of 3:1 (DFO/TR1402) and radiolabeling with 89Zr (t1/2 = 78.4 h, β+ = 22.7%). As TSHR is absent in commonly available DTC-derived cell lines, TSHR was reintroduced via stable transduction by delivering a lentivirus containing the full-length coding region of the human TSHR gene. Receptor-mediated uptake of [89Zr]Zr-TR1402 was evaluated in vitro in stably transduced TSHR+ and wild-type TSHR- DTC cell lines. In vivo PET imaging was performed on Days 1-3 postinjection in male and female athymic nude mice bearing TSHR+ and TSHR- xenografts, along with ex vivo biodistribution on Day 3 postinjection. In vitro uptake of 1 nM [89Zr]Zr-TR1402 was significantly higher in TSHR+ THJ529T (P < 0.0001) and FTC133 (P < 0.01) cells than in TSHR- THJ529T and FTC133 cells. This uptake was shown to be specific in both TSHR+ THJ529T (P < 0.0001) and TSHR+ FTC133 (P < 0.0001) cells by blocking uptake with 250 nm DFO-TR1402. In vivo PET imaging showed accumulation of [89Zr]Zr-TR1402 in TSHR+ tumors, which was the highest on Day 1. In the male FTC133 xenograft model, ex vivo biodistribution confirmed a significant difference (P < 0.001) in uptake between FTC133+ (1.3 ± 0.1%ID/g) and FTC133- (0.8 ± 0.1%ID/g) tumors. A significant difference (P < 0.05) in uptake was also seen in the male THJ529T xenograft model between THJ529T+ (1.8 ± 0.6%ID/g) and THJ529T- (0.8 ± 0.4%ID/g) tumors. The in vitro and in vivo accumulation of [89Zr]Zr-TR1402 in TSHR-expressing DTC cell lines support the continued preclinical optimization of this approach.

Canine follicular cell and medullary thyroid carcinomas: Immunohistochemical characterization

Research on modulation of iodine uptake by thyroid cells could help improve radioiodine treatment of dogs with thyroid tumors. The aim of this study was to characterize the immunohistochemical expression of thyroid transcription factor-1 (TTF-1), thyroglobulin, thyrotropin receptor (TSHR), sodium iodide symporter (NIS), pendrin, thyroid peroxidase (TPO), vimentin, and Ki-67 in follicular cell thyroid carcinomas (FTCs) and medullary thyroid carcinomas (MTCs), and to compare protein expression between FTC causing hyperthyroidism and FTC of euthyroid dogs. Immunohistochemistry was performed in 25 FTCs (9 follicular, 8 follicular-compact, and 8 compact) and 8 MTCs. FTCs and MTCs were positive for TTF-1, and expression was higher in FTCs of euthyroid dogs compared with FTCs of hyperthyroid dogs (P= .041). Immunolabeling for thyroglobulin was higher in follicular and follicular-compact FTCs compared with compact FTCs (P = .001), while vimentin expression was higher in follicular-compact FTCs compared with follicular FTCs (P = .011). The expression of TSHR, NIS, pendrin, and TPO was not significantly different among the different subtypes of FTCs or between FTCs causing hyperthyroidism and FTCs in euthyroid dogs. TSHR, NIS, pendrin, and TPO were also expressed in MTCs. Ki-67 labeling index was comparable between FTCs and MTCs, and between FTCs causing hyperthyroidism and FTCs in euthyroid dogs. Proteins of iodine transport were also expressed in canine MTCs, which could have implications for diagnosis and treatment. The different expression of thyroglobulin and vimentin between FTC histological subtypes could reflect variations in tumor differentiation.

Thyroid-stimulating hormone receptor (TSHR) as a target for imaging differentiated thyroid cancer

BACKGROUND

Of the half a million cases of thyroid cancer diagnosed annually, 95% are differentiated thyroid cancers. Although clinical guidelines recommend surgical resection followed by radioactive iodine ablation, loss of sodium-iodine symporter expression causes up to 20% of differentiated thyroid cancers to become radioactive iodine refractory. For patients with radioactive iodine refractory disease, there is an urgent need for new diagnostic and therapeutic approaches. We evaluated the thyroid-stimulating hormone receptor as a potential target for imaging of differentiated thyroid cancer.

METHODS

We immunostained tissue microarrays containing 52 Hurthle cell carcinomas to confirm thyroid-stimulating hormone receptor expression. We radiolabeled chelator deferoxamine conjugated to recombinant human thyroid-stimulating hormone analog superagonist TR1402 with 89Zr (t1/2 = 78.4 h, β+ =22.7%) to produce [89Zr]Zr-TR1402. We performed in vitro uptake assays in high-thyroid-stimulating hormone receptor and low-thyroid-stimulating hormone receptor-expressing THJ529T and FTC133 thyroid cancer cell lines. We performed in vivo positron emission tomography/computed tomography and biodistribution studies in male athymic nude mice bearing thyroid-stimulating hormone receptor-positive THJ529T tumors.

RESULTS

Immunohistochemical analysis revealed 62% of patients (27 primary and 5 recurrent) were thyroid-stimulating hormone receptor membranous immunostain positive. In vitro uptake of 1nM [89Zr]Zr-TR1402 was 38 ± 17% bound/mg in thyroid-stimulating hormone receptor-positive THJ529T thyroid cancer cell lines compared to 3.2 ± 0.5 in the low-expressing cell line (P < .01), with a similar difference seen in FTC133 cell lines (P < .0001). In vivo and biodistribution studies showed uptake of [89Zr]Zr-TR1402 in thyroid-stimulating hormone receptor-expressing tumors, with a mean percentage of injected dose/g of 1.9 ± 0.4 at 3 days post-injection.

CONCLUSION

Our observation of thyroid-stimulating hormone receptor expression in tissue microarrays and [89Zr]Zr-TR1402 accumulation in thyroid-stimulating hormone receptor-positive thyroid cancer cells and tumors suggests thyroid-stimulating hormone receptor is a promising target for imaging of differentiated thyroid cancer.

Poly (lactic-co-glycolic acid)-encapsulated iodine-131 nanoparticles fabricated with rhTSH induce apoptosis and immobilization of thyroid cancer cells

Background

Aggressive thyroid carcinoma (ATC) usually loses radioiodine avidity to iodine-131 (¹³¹I) due to the downregulation of sodium/iodide symporter (NIS). The expression of thyroid stimulating hormone receptor (TSHR) is more persistent than NIS and the administration of recombinant human thyroid stimulating hormone (rhTSH) promotes de novo NIS synthesis. Hence, exploring methods integrating ¹³¹I with rhTSH might be a feasible therapeutic strategy for selective delivery of ¹³¹I into thyroid cancer to fortify the effect of radioiodine ablation.

Methods

The ¹³¹I, poly (lactic-co-glycolic acid) (PLGA) and rhTSH were used to synthesize of the ¹³¹I-PLGA-rhTSH nanoparticles. The characteristics of the ¹³¹I-PLGA-rhTSH nanoparticles was determined using a light microscopy, scanning electron microscopy (SEM), autoradiography and immunofluorescence (IF) staining. The diameter of the ¹³¹I-PLGA-rhTSH nanoparticles was measured with a Mastersizer 3000, and the encapsulation efficiency (EF) of ¹³¹I in ¹³¹I-PLGA-rhTSH nanoparticles and the radioactivity of a single nanoparticle were determined. Then, the mouse tumor xenograft model was established, and the biodistribution and effect of ¹³¹I-PLGA-rhTSH nanoparticles on apoptosis of thyroid cance cells were investigated in vivo. Thereafter, the role of ¹³¹I-PLGA-rhTSH nanoparticles in cell viability using cell counting kit-8 and lactate dehydrogenase (LDH) release assays. Subsequently, the underlying mechanism of ¹³¹I-PLGA-rhTSH nanoparticles in reducing cell viability was assessed using immunostaining, boyden invasion assays and phalloidin staining.

Results

Our results showed that the method of developing nanoparticles-encapsulated ¹³¹I using poly (lactic-co-glycolic acid) (PLGA) and modified with rhTSH (¹³¹I-PLGA-rhTSH), was a feasible avenue for the integration of ¹³¹I and rhTSH. Meanwhile, the encapsulation efficiency (EF) of ¹³¹I-PLGA-rhTSH nanoparticles was approximately 60%, and the radioactivity of a single nanoparticle was about 1.1×10-2 Bq. Meanwhile, the ¹³¹I-PLGA-rhTSH nanoparticles were selectively delivered into, gradually enriched and slowly downregulated in xenograft tumor after the administration of ¹³¹I-PLGA-rhTSH nanoparticles through tail vein in mouse tumor xenograft model. Thereafter, the tumor weight was significantly reduced after the administration of ¹³¹I-PLGA-rhTSH nanoparticles. Subsequently, the application of ¹³¹I-PLGA-rhTSH nanoparticles facilitated apoptosis and attenuated immobilization via inhibiting F-actin assembling of FTC-133 cells.

Conclusion

The present study develops a suitable approach integrating ¹³¹I and rhTSH, and this strategy is a feasible regimen enhancing the effect of radioiodine ablation for the treatment of thyroid cancer.

CAR-T Cells Targeting TSHR Demonstrate Safety and Potent Preclinical Activity Against Differentiated Thyroid Cancer

BACKGROUND

Chimeric antigen receptor T cells (CAR-Ts) have demonstrated remarkable efficacy in hematological cancers but have not yet translated in treating solid tumors. The significant hurdles limiting CAR-T therapy were from a paucity of differentially expressed cell surface molecules on solid tumors that can be safely targeted. Here, we present TSH receptor (TSHR) as a putative target for CAR-T therapy of differentiated thyroid cancer (DTC).

METHODS

We undertook a large-scale screen on thyroid cancer tissues and multiple internal organs through bioinformatical analysis and immunohistochemistry to date TSHR expression. Using 3 previously described monoclonal antibodies, we generated 3 third-generation CAR-Ts. We tested anti-TSHR CAR-T in vitro activity by T-cell function and killing assay. Then we tested preclinical therapeutical efficacy in a xenograft mouse model of DTC and analyzed mice's physical conditions and histological abnormalities to evaluate anti-TSHR CAR-T's safety.

RESULTS

TSHR is highly and homogeneously expressed on 90.8% (138/152) of papillary thyroid cancer, 89.2% (33/37) of follicular thyroid cancer, 78.2% (18/23) of cervical lymph node metastases, and 86.7% of radioactive iodine resistance diseases. We developed 3 novel anti-TSHR CAR-Ts from monoclonal antibodies M22, K1-18, and K1-70; all 3 CAR-Ts mediate significant antitumor activity in vitro. Among these, we demonstrate that K1-70 CAR-T can have therapeutical efficacy in vivo, and no apparent toxicity has been observed.

CONCLUSION

TSHR is a latent target antigen of CAR-T therapy for DTC. Anti-TSHR CAR-T could represent a therapeutic option for patients with locoregional relapsed or distant metastases of thyroid cancer and should be tested in carefully designed clinical trials.

Developing Actively Targeted Nanoparticles to Fight Cancer: Focus on Italian Research

Active targeting is a valuable and promising approach with which to enhance the therapeutic efficacy of nanodelivery systems, and the development of tumor-targeted nanoparticles has therefore attracted much research attention. In this field, the research carried out in Italian Pharmaceutical Technology academic groups has been focused on the development of actively targeted nanosystems using a multidisciplinary approach. To highlight these efforts, this review reports a thorough description of the last 10 years of Italian research results on the development of actively targeted nanoparticles to direct drugs towards different receptors that are overexpressed on cancer cells or in the tumor microenvironment. In particular, the review discusses polymeric nanocarriers, liposomes, lipoplexes, niosomes, solid lipid nanoparticles, squalene nanoassemblies and nanobubbles. For each nanocarrier, the main ligands, conjugation strategies and target receptors are described. The literature indicates that polymeric nanoparticles and liposomes stand out as key tools for improving specific drug delivery to the site of action. In addition, solid lipid nanoparticles, squalene nanoparticles and nanobubbles have also been successfully proposed. Taken together, these strategies all offer many platforms for the design of nanocarriers that are suitable for future clinical translation.

Mechanisms of regulating NIS transport to the cell membrane and redifferentiation therapy in thyroid cancer

Iodine is an essential constituent of thyroid hormone. Active iodide accumulation in the thyroid is mediated by the sodium iodide symporter (NIS), comprising the first step in thyroid hormone biosynthesis, which relies on the functional expression of NIS on the cell membrane. The retention of NIS expressed in differentiated thyroid cancer (DTC) cells allows further treatment with post-operative radioactive iodine (RAI) therapy. However, compared with normal thyroid tissue, differentiated thyroid tumors usually show a decrease in the active iodide conveyance and NIS is generally retained within the cells, indicating that posttranslational protein transfer to the plasma membrane is abnormal. In recent years, through in vitro studies and studies of patients with DTC, various methods have been tested to increase the transport rate of NIS to the cell membrane and increase the absorption of iodine. An in-depth understanding of the mechanism of NIS transport to the plasma membrane could lead to improvements in RAI therapy. Therefore, in this review, we discuss the current knowledge concerning the post-translational mechanisms that regulate NIS transport to the cell membrane and the current status of redifferentiation therapy for patients with RAI-refractory (RAIR)-DTC.

Immunotherapy for advanced thyroid cancers - rationale, current advances and future strategies

In the past decade, the field of cancer immunotherapy has been revolutionized by immune checkpoint blockade (ICB) technologies. Success across a broad spectrum of cancers has led to a paradigm shift in therapy for patients with advanced cancer. Early data are now accumulating in progressive thyroid cancers treated with single-agent ICB therapies and combination approaches that incorporate ICB technologies. This Review discusses our current knowledge of the immune response in thyroid cancers, the latest and ongoing immune-based approaches, and the future of immunotherapies in thyroid cancer. Physiologically relevant preclinical mouse models and human correlative research studies will inform development of the next stage of immune-based therapies for patients with advanced thyroid cancer.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

MEK Inhibition Induces Therapeutic Iodine Uptake in a Murine Model of Anaplastic Thyroid Cancer

Anaplastic thyroid carcinoma (ATC) is refractory to radioiodine therapy in part because of impaired iodine metabolism. We targeted the mitogen-activated protein kinase and phosphatidylinositol 3-kinase (PI3'K) pathways with the intent to induce radioiodine uptake for radioiodine treatment of ATC. Methods: Human ATC cells were used to evaluate the ability of pharmacologic inhibition of the mitogen-activated protein kinase and PI3'K pathways to induce radioiodine uptake. Thyrocyte-specific double-mutant BRAF^V600E PIK3CA^H1047R mice were treated with a MEK inhibitor followed by radioiodine treatment, and tumor burden was monitored by ultrasound imaging. Results: ATC cell lines showed an increase in sodium-iodine symporter transcription when treated with a MEK or BRAF^V600E inhibitor alone and in combination with PI3'K inhibitor. This translated into a dose-dependent elevation of iodine uptake after treatment with a MEK inhibitor alone and in combination with a PI3'K inhibitor. In vivo, MEK inhibition but not BRAF or PI3'K inhibition upregulated sodium-iodine symporter transcription. This translated into a stable reduction of tumor burden when mice were treated with a MEK inhibitor before radioiodine administration. Conclusion: This study confirms the ability of MEK inhibition to induce iodine uptake in in vitro and in vivo models of ATC. The approach of using a MEK inhibitor before radioiodine treatment could readily be translated into clinical practice and provide a much-needed therapeutic option for patients with ATC.

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

Aims

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

Patients and methods

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

Results

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

Conclusions

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

Myocardium of patients with dilated cardiomyopathy presents altered expression of genes involved in thyroid hormone biosynthesis

Background

The association between dilated cardiomyopathy (DCM) and low thyroid hormone (TH) levels has been previously described. In these patients abnormal thyroid function is significantly related to impaired left ventricular (LV) function and increased risk of death. Although TH was originally thought to be produced exclusively by the thyroid gland, we recently reported TH biosynthesis in the human ischemic heart.

Objectives

Based on these findings, we evaluated whether the genes required for TH production are also altered in patients with DCM.

Methods

Twenty-three LV tissue samples were obtained from patients with DCM (n = 13) undergoing heart transplantation and control donors (n = 10), and used for RNA sequencing analysis. The number of LV DCM samples was increased to 23 to determine total T4 and T3 tissue levels by ELISA.

Results

We found that all components of TH biosynthesis are expressed in human dilated heart tissue. Expression of genes encoding thyroperoxidase (–2.57-fold, P < 0.05) and dual oxidase 2 (2.64-fold, P < 0.01), the main enzymatic system of TH production, was significantly altered in patients with DCM and significantly associated with LV remodeling parameters. Thyroxine (T4) cardiac tissue levels were significantly increased (P < 0.01), whilst triiodothyronine (T3) levels were significantly diminished (P < 0.05) in the patients.

Conclusions

Expression of TH biosynthesis machinery in the heart and total tissue levels of T4 and T3, are altered in patients with DCM. Given the relevance of TH in cardiac pathology, our results provide a basis for new gene-based therapeutic strategies for treating DCM.

Long Non-coding Antisense RNA TNRC6C-AS1 Is Activated in Papillary Thyroid Cancer and Promotes Cancer Progression by Suppressing TNRC6C Expression

Context: Evidences have shown the important role of long non-coding antisense RNAs in regulating its cognate sense gene in cancer biology. Objective: Investigate the regulatory role of a long non-coding antisense RNA TNRC6C-AS1 on its sense partner TNRC6C, and their effects on the aggressiveness and iodine-uptake ability of papillary thyroid cancer (PTC). Design: TNRC6C-AS1 was identified as the target long non-coding RNA in PTC by using microarray analysis and computational analysis. In vitro gain/loss-of-function experiments were performed to investigate the effects of TNRC6C-AS1 and TNRC6C on proliferation, apoptosis, migration, invasion and iodine-uptake ability of TPC1 cells. Expression levels of TNRC6C-AS1 and TNRC6C of 30 cases of PTC tissues and its adjacent normal thyroid tissues were determined. Results: Downregulation of TNRC6C-AS1 or overexpression of TNRC6C inhibited proliferation, migration and invasion of TPC1 cells, while apoptosis and iodine uptake was promoted in TPC1 cells. Suppression of TNRC6C-AS1 significantly increased the expression of TNRC6C in TPC1 cells. The inhibitory effect of TNRC6C-AS1 knockdown on cell proliferation, migration and invasion was attenuated when the expression of TNRC6C was suppressed simultaneously, indicating TNRC6C is a functional target of TNRC6C-AS1. The expression of TNRC6C-AS1 was significantly higher, while the TNRC6C mRNA and protein were significantly lower in PTC tissues than normal adjacent tissues. There was a significant inverse correlation between TNRC6C-AS1 and TNRC6C mRNA in PTC tissue samples. Conclusions: TNRC6C-AS1 promotes the progression of PTC and inhibits its ability of iodine accumulation by suppressing the expression of TNRC6C. Targeting TNRC6C-AS1 - TNRC6C axis may be a new promising treatment for PTC.

Targeting the TSH receptor in thyroid cancer

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

Citrus flavanones mildly interfere with pituitary-thyroid axis in old-aged male rats

Citrus flavanones naringenin (NAR) and hesperetin (HES) are potent antioxidants that may contribute to maintenance of health at old age by improving cardiovascular and metabolic status. However, they may also affect thyroid hormone economy. Keeping in mind impaired thyroid function at older age, in this study we tested wheather NAR or HES administration potentiate this decline. NAR or HES were administrated orally (15mg/kg) to male 24-month-old Wistar rats during 4 weeks. Control groups received vehicle, sunflower oil. Qualitative and quantitative immunohistochemical and immunofluorescent expression of specific proteins and stereological analyses of thyroid tissue were performed. Thyroid stimulating hormone (TSH) and total thyroxine (T₄) concentrations were measured in serum. Thyroid parenchyma of both flavanone-treated groups was characterized by lower (p<0.05) absolute and relative volume of luminal colloid, accompanied by elevated (p<0.05) relative volume of stroma in comparison with the controls. No hypertrophy or absolute thyroid volume change was detected. Intensity of immunopositive signal for thyroglobulin (Tg) and T₄ bound to Tg (T₄-Tg) increased (p<0.05) in the colloid of thyroid follicles after both flavanone treatments. Serum TSH increased (p<0.05) after NAR, while T₄ remained unchanged after both treatments. In conclusion, NAR elevated serum TSH in old-aged males, thus being more potent than HES in altering pituitary-thyroid axis. However, changes in thyroid structure, namely moderate colloid depletion and higher Tg and T₄-Tg protein expressions after both treatments, indicate preserved capacity of the gland to compensate flavanone interfering, and maintain T₄ production in old-aged males.

Functional morphology of pituitary -thyroid and -adrenocortical axes in middle-aged male rats treated with Vitex agnus castus essential oil

We previously reported that Vitex agnus-castus L. essential oil (VACEO), when administered to middle-aged males, exerts a bone-protective effect, induces silencing of locomotor activities and decreases pituitary prolactin immunopositivity. To further assess the putative endocrine effects of VACEO, we examined the pituitary-thyroid and -adrenocortical axes in our model. Sixteen-month-old Wistar rats were subcutaneously administered 60mg/kg of VACEO dissolved in sterile olive oil, while the control group received the same amount of vehicle alone for three weeks. Pituitaries, thyroids and adrenals were analyzed by qualitative and quantitative histological approaches. Concentration of thyroid stimulating hormone (TSH), total thyroxine and triiodothyronine (TH), adrenocorticotrophic hormone (ACTH), corticosterone in serum and in adrenal tissue were measured. In VACEO-treated rats, the relative volume density of pituitary thyrotrophs increased (p<0.001), while intensity of cytoplasmic TSHβ immunostaining decreased (p<0.001), consistent with elevated TSH in serum (p<0.01). The thyroid tissue was characterized by a micro-follicular structure, increased relative volume of follicular epithelium (p<0.05), decreased volume of luminal colloid (p<0.001) and increased basolateral expression of sodium-iodide symporter-immunopositivity (p<0.05). Serum TH also increased (p<0.01). The relative volume density of pituitary corticotrophs decreased (p<0.05), compatible with decline in circulating ACTH (p<0.05). Neither tissue nor serum corticosterone levels were affected by VACEO treatment. In conclusion, the observed changes in TSH and ACTH strongly indicate central endocrine effects of prolonged VACEO treatment. In this respect, production of ACTH decreased without impact on corticosterone production. Increase in serum concentration of both TH and TSH are not compatible with a negative feedback loop and suggest a major change in set-point regulation of the hypothalamic-pituitary-thyroid axis.

Oxidative stress and the subcellular localization of the telomerase reverse transcriptase (TERT) in papillary thyroid cancer

During hormonogenesis, thyrocytes are physiologically exposed to high levels of oxidative stress (OS) which could either be involved in the pathogenesis of thyroid cancer or exert a cytotoxic effect. We analyzed the oxidative status of papillary thyroid cancer (PTC) both directly, by measuring H2O2 generation by NADPH oxidases (NOXs), and indirectly, by evaluating the antioxidant activity of glutathione peroxidase (GPX), which neutralizes H2O2 excess, and the lipid peroxidation (LP). Moreover, we investigated the subcellular localization of telomerase reverse transcriptase (TERT), and the H2O2 levels in the mitochondria of tumor and normal tissues. The calcium-dependent and independent H2O2 generation activity was significantly higher in tumors than in normal tissues. The GPX activity was higher in PTCs than in normal tissues, and, consistently, no differences were found in LP levels. Moreover, while TERT nuclear expression was similar in tumor and normal tissues, the mitochondrial localization was significantly higher in tumors. At the mitochondrial level, no differences were found in H2O2 generation between tumor and normal tissues. In conclusion, present data demonstrate that the intracellular H2O2 generation by NOXs is significantly higher in PTCs than in normal thyroid tissues. The increased GPX activity found in tumors counteracts the potential cytotoxic effects of high OS exposure. The significantly higher mitochondrial localization of TERT in tumors is consistent with its shuttling from the nucleus upon exposure to high OS. Finally, mitochondrial OS was not significantly different in tumors and normal tissues, supporting the postulated role of mitochondrial TERT in the control of local H2O2 production.

Testosterone and estradiol treatments differently affect pituitary-thyroid axis and liver deiodinase 1 activity in orchidectomized middle-aged rats

We previously reported that orchidectomy (Orx) of middle-aged rats (15-16-month-old; MA) slightly affected pituitary-thyroid axis, but decreased liver deiodinase (Dio) type 1 and pituitary Dio2 enzyme activities. At present, we examined the effects of subsequent testosterone-propionate treatment (5mg/kg; Orx+T), and compared the effects of testosterone with the effects of estradiol-dipropionate (0.06mg/kg; Orx+E) treatment. Hormones were subcutaneously administered, daily, for three weeks, while Orx and sham-operated (SO) controls received only the vehicle. The applied dose of T did not alter serum TSH, T4 and T3 concentrations in Orx- MA, though it increased TSH when administrated to Orx young adults (2.5-month-old; Orx-YA). However, pituitaries of Orx-MA+T rats had higher relative intensity of immunofluorescence (RIF) for TSHβ; in their thyroids we found increased volume and height of follicular epithelium, decreased volume of the colloid and higher RIF for T4-bound to thyroglobulin (Tg-T4). Liver Dio1 activity was increased. E-treatment did not affect serum hormone levels, pituitary RIF for TSHβ, or liver Dio1 activity in Orx-MA rats. Thyroids had decreased relative volume and height of follicular epithelium, increased relative volume of the colloid, decreased volume of sodium-iodide symporter-immunopositive epithelium and lower RIF for Tg-T4. Detected changes were statistically significant. In conclusion, androgenization enhanced pituitary TSHβ RIF, thyroid activation and liver Dio1 enzyme activity in Orx-MA, without elevating serum TSH as in Orx-YA rats. Estrogenization induced pituitary enlargement with no effect on pituitary TSHβ RIF, serum TSH or liver Dio1 activity. E also induced alterations in thyroid histology that indicate mild suppression of its functioning, and contributed to thyroid blood vessel enlargement in Orx-MA rats.

Autophagy in thyroid cancer: present knowledge and future perspectives

Thyroid cancer is the most common endocrine malignancy. Despite having a good prognosis in the majority of cases, when the tumor is dedifferentiated it does no longer respond to conventional treatment with radioactive iodine, the prognosis worsens significantly. Treatment options for advanced, dedifferentiated disease are limited and do not cure the disease. Autophagy, a process of self-digestion in which damaged molecules or organelles are degraded and recycled, has emerged as an important player in the pathogenesis of different diseases, including cancer. The role of autophagy in thyroid cancer pathogenesis is not yet elucidated. However, the available data indicate that autophagy is involved in several steps of thyroid tumor initiation and progression as well as in therapy resistance and therefore could be exploited for therapeutic applications. The present review summarizes the most recent data on the role of autophagy in the pathogenesis of thyroid cancer and we will provide a perspective on how this process can be targeted for potential therapeutic approaches and could be further explored in the context of multimodality treatment in cancer and personalized medicine.

Roles of DUOX-mediated hydrogen peroxide in metabolism, host defense, and signaling

SIGNIFICANCE

Among the NADPH oxidases, the dual oxidases, DUOX1 and DUOX2, constitute a distinct subfamily initially called thyroid oxidases, based on their high level of expression in thyroid tissue. Genetic alterations causing inherited hypothyroidism clearly demonstrate their physiological implication in thyroid hormonogenesis. However, a growing list of biological functions triggered by DUOX-dependent reactive oxygen species (ROS) in highly differentiated mucosae have recently emerged.

RECENT ADVANCES

A role of DUOX enzymes as ROS providers for lactoperoxidase-mediated killing of invading pathogens has been well established and a role in bacteria chemorepulsion has been proposed. Control of DUOX expression and activity by inflammatory molecules and immune receptor activation consolidates their contributions to innate immune defense of mucosal surfaces. Recent studies conducted in ancestral organisms have identified effectors of DUOX redox signaling involved in wound healing including epithelium regeneration and leukocyte recruitment. Moreover, local generation of hydrogen peroxide (H2O2) by DUOX has also been suggested to constitute a positive feedback loop to promote receptor signaling activation.

CRITICAL ISSUES

A correct balance between H2O2 generation and detoxification mechanisms must be properly maintained to avoid oxidative damages. Overexpression of DUOX genes has been associated with an increasing number of chronic inflammatory diseases. Furthermore, H2O2-mediated DNA damage supports a mutagenic function promoting tumor development.

FUTURE DIRECTIONS

Despite the high sequence similarity shared between DUOX1 and DUOX2, the two isoforms present distinct regulations, tissue expression and catalytic functions. The phenotypic characterization of novel DUOX/DUOXA invalidated animal models will be very useful for defining their medical importance in pathological conditions.

Morpho-functional characteristics of rat fetal thyroid gland are affected by prenatal dexamethasone exposure

Thyroid hormones (TH) and glucocorticoids strongly contribute to the maturation of fetal tissues in the preparation for extrauterine life. Influence of maternal dexamethasone (Dx) administration on thyroid glands morpho-functional characteristics of near term rat fetuses was investigated applying unbiased stereology. On the 16th day of pregnancy dams received 1.0mg/Dx/kg/b.w., followed by 0.5mg/Dx/kg/b.w. on the 17th and 18th days of gestation. The control females received the same volume of saline. The volume of fetal thyroid was estimated using Cavalieri's principle; the physical/fractionator design was applied for the determination of absolute number of follicular cells in mitosis and immunohistochemically labeled C cells; C cell volume was measured using the planar rotator. The functional activity of thyroid tissue was provided from thyroglobulin (Tg) and thyroperoxidase (TPO) immunohistochemical staining. Applying these design-based modern stereological methods it was shown that Dx treatment of gravid females led to a significant decrease of fetal thyroid gland volume in 19- and 21-day-old fetuses, due to decreased proliferation of follicular cells. The Tg and TPO immunohistochemistry demonstrated that intensive TH production starts and continues during the examined period in control and Dx-exposed fetuses. Under the influence of Dx the absolute number of C cells was lower in both groups of near term fetuses, although unchanged relation between the two populations of endocrine cells, follicular and C cells suggesting that structural relationships within the gland are preserved. In conclusion maternal glucocorticoid administration at the thyroid gland level exerts growth-inhibitory and maturational promoting effects in near term rat fetuses.

Expression patterns of glucose transporter-1 gene and thyroid specific genes in human papillary thyroid carcinoma

PURPOSE

The expression of glucose transporter-1 (Glut-1) gene and those of major thyroid-specific genes were examined in papillary carcinoma tissues, and the expressions of these genes were compared with cancer differentiation grades.

MATERIALS AND METHODS

Twenty-four human papillary carcinoma tissues were included in this study. The expressions of Glut-1- and thyroid-specific genes [sodium/iodide symporter (NIS), thyroid peroxidase, thyroglobulin, TSH receptor and pendrin] were analyzed by RT-PCR. Expression levels were expressed as ratios versus the expression of beta-actin. Pathologic differentiation of papillary carcinoma was classified into a relatively well-differentiated group (n = 13) and relatively less differentiated group (n = 11).

RESULTS

Glut-1 gene expression was significantly higher in the less differentiated group (0.66 ± 0.04) than in the well-differentiated group (0.59 ± 0.07). The expression levels of the NIS, PD and TG genes were significantly higher in the well-differentiated group (NIS: 0.67 ± 0.20, PD: 0.65 ± 0.21, TG: 0.74 ± 0.16) than in the less differentiated group (NIS: 0.36 ± 0.05, PD: 0.49 ± 0.08, TG: 0.60 ± 0.11), respectively. A significant negative correlation was found between Glut-1 and NIS expression, and positive correlations were found between NIS and TG, and between NIS and PD.

CONCLUSION

The NIS, PD and TG genes were highly expressed in well-differentiated thyroid carcinomas, whereas the Glut-1 gene was highly expressed in less differentiated thyroid carcinomas. These findings provide a molecular rationale for the management of papillary carcinoma, especially in the selection of FDG PET or radioiodine whole-body scan and I-131-based therapy.

Targeting the thyroid gland with thyroid-stimulating hormone (TSH)-nanoliposomes

Various tissue-specific antibodies have been attached to nanoparticles to obtain targeted delivery. In particular, nanodelivery systems with selectivity for breast, prostate and cancer tissue have been developed. Here, we have developed a nanodelivery system that targets the thyroid gland. Nanoliposomes have been conjugated to the thyroid-stimulating hormone (TSH), which binds to the TSH receptor (TSHr) on the surface of thyrocytes. The results indicate that the intracellular uptake of TSH-nanoliposomes is increased in cells expressing the TSHr. The accumulation of targeted nanoliposomes in the thyroid gland following intravenous injection was 3.5-fold higher in comparison to untargeted nanoliposomes. Furthermore, TSH-nanoliposomes encapsulated with gemcitabine showed improved anticancer efficacy in vitro and in a tumor model of follicular thyroid carcinoma. This drug delivery system could be used for the treatment of a broad spectrum of thyroid diseases to reduce side effects and improve therapeutic efficacy.

Morphological and functional changes in pituitary-thyroid axis following prolonged exposure of female rats to constant light

Light regulates numerous physiological functions and synchronizes them with the environment, in part by adjusting secretion of different hormones. We hypothesized that constant light (CL) would disturb pituitary-thyroid axis. Our aim was to determine morphological and functional changes in this endocrine system in such extreme conditions and, based on the obtained results, to propose the underlying mechanism(s). Starting from the thirtieth postnatal day, female Wistar rats were exposed to CL (600 lx) for the following 95 days. The controls were maintained under the regular laboratory lighting conditions. After decapitation, pituitaries and thyroids were prepared for further histomorphometric, immunohistochemical, and immunofluorescence examinations. Concentration of thyroid stimulating hormone (TSH), total T4 and T3 (TH) were determined. Thyroid tissue of light-treated rats was characterized by microfollicular structure. We detected no change in total thyroid volume, localization and accumulation of thyroglobulin, thyroid peroxidase, and sodium-iodide symporter in the follicular epithelium of CL rats. The volume of follicular epithelium and activation index were increased, while volume of the colloid and serum levels of TH decreased. In the pituitary, the relative intensity of TSH β-immunofluorescence signal within the cytoplasm of thyrotrophs increased, but their average cell volume and the relative volume density decreased. Serum TSH was unaltered. We conclude that exposure of female rats to CL induced alterations in pituitary-thyroid axis. Thyroid tissue was characterized by microfollicular structure. Serum TH levels were reduced without accompanying increase in serum TSH. We hypothesize that increased secretion and clearance of TH together with unchanged or even decreased hormonal synthesis, resulted in decreased serum TH levels in CL group. We assume this decrease consequently led to increased synthesis and/or accumulation of pituitary TSH. However, decreased average TSH cell volume and relative volume density, together with unchanged serum TSH, point to additional, negative regulation of thyrotrophs.

Different expression of TSH receptor and NIS genes in thyroid cancer: role of epigenetics

The TSH receptor (TSHR) and sodium/iodide symporter (NIS) are key players in radioiodine-based treatment of differentiated thyroid cancers. While NIS (SLC5AS) expression is diminished/lost in most thyroid tumors, TSHR is usually preserved. To examine the mechanisms that regulate the expression of NIS and TSHR genes in thyroid tumor cells, we analyzed their expression after inhibition of ras-BRAF-MAPK and PI3K-Akt-mTOR pathways and the epigenetic control occurring at the gene promoter level in four human thyroid cancer cell lines. Quantitative real-time PCR was used to measure NIS and TSHR mRNA in thyroid cancer cell lines (TPC-1, BCPAP, WRO, and FTC-133). Western blotting was used to assess the levels of total and phosphorylated ERK and Akt. Chromatin immunoprecipitation was performed for investigating histone post-translational modifications of the TSHR and NIS genes. ERK and Akt inhibitors elicited different responses of the cells in terms of TSHR and NIS mRNA levels. Akt inhibition increased NIS transcript levels and reduced those of TSHR in FTC-133 cells but had no significant effects in BCPAP. ERK inhibition increased the expression of both genes in BCPAP cells but had no effects in FTC-133. Histone post-translational modifications observed in the basal state of the four cell lines as well as in BCPAP treated with ERK inhibitor and FTC-133 treated with Akt inhibitor show cell- and gene-specific differences. In conclusion, our data indicate that in thyroid cancer cells the expression of TSHR and NIS genes is differently controlled by multiple mechanisms, including epigenetic events elicited by major signaling pathways involved in thyroid tumorigenesis.

A mouse model with tamoxifen-inducible thyrocyte-specific cre recombinase activity

We have created a mouse model expressing tamoxifen-inducible Cre recombinase (CreER(T2) ) under the control of the thyroglobulin (Tg) gene promoter to be able to study the role of defined genetic modifications in the regulation of thyroid function. We chose the thyroglobulin promoter, as it is expressed specifically in the thyroid. In order to obtain reliable expression under the control of the Tg promoter, we used a P1 artificial chromosome (PAC) containing a large piece of the Tg promoter. A tamoxifen inducible CreER(T2) construct was selected to avoid the possible consequences of the gene deletion for the development of the thyroid gland, and to study the role of gene deletion in the adult thyroid. Transgenic lines (TgCreER(T2) ) carrying this construct were generated and analyzed by crossing the TgCreER(T2) mice with the ROSA26LacZ reporter strain. The activity and specificity of the Cre recombinase was tested by staining for β-galactosidase activity and by immunohistochemistry using an anti-Cre-antibody. In the TgCreER(T2) xROSA26LacZ reporter line, Cre-mediated recombination occurred specifically in the thyrocytes only after tamoxifen administration, and no significant staining was observed in controls. The recombination efficiency was nearly complete, since almost all thyrocytes showed X-gal staining. We could also induce the recombination in utero by giving tamoxifen to the pregnant female. In addition, mice expressing TgCreER(T2) had no obvious histological changes, hormonal alterations, or different response to growth stimuli as compared to controls. These results demonstrate that the TgCreER(T2) mouse line is a powerful tool to study temporally controlled deletion of floxed genes in the thyroid.

TPO genetic variants and risk of differentiated thyroid carcinoma in two European populations

Thyroid cancer risk involves the interaction of genetic and environmental factors. The thyroperoxidase (TPO) has a key role in the iodine metabolism, being essential for the thyroid function. Mutations in the TPO gene are common in congenital hypothyroidism, and there are also signs of the implication of TPO in thyroid cancer. We performed a case-control association study of genetic variants in TPO and differentiated thyroid carcinoma (DTC) in 1,586 DTC patients and 1,769 controls including two European populations (Italy: 1,190 DTC and 1,290 controls; Spain: 396 DTC and 479 controls). Multivariate logistic regression analyses were performed separately for each population and each single-nucleotide polymorphism (SNP). From the three studied polymorphisms, significant associations were detected between DTC and rs2048722 and rs732609 in both populations (p < 0.05). In the Italian population, both SNPs showed a negative association (rs2048722, odds ratio [OR] = 0.79, 95% confidence interval [CI] = 0.63-1.00, p = 0.045; rs732609, OR = 0.72, 95% CI = 0.55-0.94, p = 0.016), whereas in the Spanish population, these SNPs showed a positive association (rs2048722, OR = 1.39, 95% CI = 1.03-1.89, p = 0.033; rs732609, OR = 1.41, 95% CI = 1.06-1.87, p = 0.018). The corresponding associations for papillary or follicular thyroid cancer were similar to those for all DTC, within population. No association was detected for the third TPO polymorphism in the Italian and the Spanish populations. Our results, for the first time, point to TPO as a gene involved in the risk of DTC, and suggest the importance of interactions between TPO variants and other unidentified population-specific factors in determining thyroid cancer risk.

Recent insights into the cell biology of thyroid angiofollicular units

In thyrocytes, cell polarity is of crucial importance for proper thyroid function. Many intrinsic mechanisms of self-regulation control how the key players involved in thyroid hormone (TH) biosynthesis interact in apical microvilli, so that hazardous biochemical processes may occur without detriment to the cell. In some pathological conditions, this enzymatic complex is disrupted, with some components abnormally activated into the cytoplasm, which can lead to further morphological and functional breakdown. When iodine intake is altered, autoregulatory mechanisms outside the thyrocytes are activated. They involve adjacent capillaries that, together with thyrocytes, form the angiofollicular units (AFUs) that can be considered as the functional and morphological units of the thyroid. In response to iodine shortage, a rapid expansion of the microvasculature occurs, which, in addition to nutrients and oxygen, optimizes iodide supply. These changes are triggered by angiogenic signals released from thyrocytes via a reactive oxygen species/hypoxia-inducible factor/vascular endothelial growth factor pathway. When intra- and extrathyrocyte autoregulation fails, other forms of adaptation arise, such as euthyroid goiters. From onset, goiters are morphologically and functionally heterogeneous due to the polyclonal nature of the cells, with nodules distributed around areas of quiescent AFUs containing globules of compact thyroglobulin (Tg) and surrounded by a hypotrophic microvasculature. Upon TSH stimulation, quiescent AFUs are activated with Tg globules undergoing fragmentation into soluble Tg, proteins involved in TH biosynthesis being expressed and the local microvascular network extending. Over time and depending on physiological needs, AFUs may undergo repetitive phases of high, moderate, or low cell and tissue activity, which may ultimately culminate in multinodular goiters.

Thyroid hydrogen peroxide production is enhanced by the Th2 cytokines, IL-4 and IL-13, through increased expression of the dual oxidase 2 and its maturation factor DUOXA2

The dual oxidases (DUOX) 1 and 2 constitute the major components of the thyroid H(2)O(2)-generating system required for thyroid hormone synthesis. With their maturation factor, DUOXA1 or DUOXA2, they share the same bidirectional promoter allowing coexpression of DUOX/DUOXA in the same tissue. However, the molecular mechanisms regulating their transcription in the human thyroid gland are not well characterized yet. Inflammatory molecules associated with autoimmune thyroid diseases have been shown to repress the thyroid function by down-regulating the expression of the major thyroid differentiation markers. These findings led us to investigate the effects of the main cytokines involved in Hashimoto thyroiditis (IFN-γ) and Graves' diseases (IL-4/IL-13) on the transcriptional regulation of DUOX and their corresponding DUOXA genes in thyroid cells. Human thyrocytes exposed to the Th2 cytokines IL-4 and IL-13 showed up-regulation of DUOX2 and DUOXA2 genes but not DUOX1/DUOXA1. The DUOX2/DUOXA2 induction was rapid and associated with a significant increase of calcium-stimulated extracellular H(2)O(2) generation. IFN-γ treatment inhibited DUOX gene expression and repressed the Th2 cytokine-dependent DUOX2/DUOXA2 expression. In another DUOX-expressing model, the human intestinal Caco-2 cell line, expression of DUOX2 and DUOXA2 mRNA was also positively modulated by IL-4 and IL-13. Analysis of the IL-4 signaling pathway revealed that the JAK1-STAT6 cascade activated by the IL-4 type 2 receptor is required for DUOX2/DUOXA2 induction. The present data open new perspectives for a better understanding of the pathophysiology of thyroid autoimmune diseases considering DUOX2-mediated oxidative damages.

The sodium iodide symporter (NIS): regulation and approaches to targeting for cancer therapeutics

Expression of the sodium iodide symporter (NIS) is required for efficient iodide uptake in thyroid and lactating breast. Since most differentiated thyroid cancer expresses NIS, β-emitting radioactive iodide is routinely utilized to target remnant thyroid cancer and metastasis after total thyroidectomy. Stimulation of NIS expression by high levels of thyroid-stimulating hormone is necessary to achieve radioiodide uptake into thyroid cancer that is sufficient for therapy. The majority of breast cancer also expresses NIS, but at a low level insufficient for radioiodine therapy. Retinoic acid is a potent NIS inducer in some breast cancer cells. NIS is also modestly expressed in some non-thyroidal tissues, including salivary glands, lacrimal glands and stomach. Selective induction of iodide uptake is required to target tumors with radioiodide. Iodide uptake in mammalian cells is dependent on the level of NIS gene expression, but also successful translocation of NIS to the cell membrane and correct insertion. The regulatory mechanisms of NIS expression and membrane insertion are regulated by signal transduction pathways that differ by tissue. Differential regulation of NIS confers selective induction of functional NIS in thyroid cancer cells, as well as some breast cancer cells, leading to more efficient radioiodide therapy for thyroid cancer and a new strategy for breast cancer therapy. The potential for systemic radioiodide treatment of a range of other cancers, that do not express endogenous NIS, has been demonstrated in models with tumor-selective introduction of exogenous NIS.

Hürthle cell carcinoma of the thyroid presenting as thyrotoxicosis

OBJECTIVE

To report a case of hyperthyroidism associated with Hürthle cell carcinoma and to review the literature regarding this relationship.

METHODS

We describe the clinical, biochemical, radiologic, and pathologic data of a patient with Hürthle cell carcinoma associated with thyrotoxicosis and reversible heart failure. We discuss the mechanistic aspects and review previously reported cases of functional Hürthle cell carcinomas.

RESULTS

A 43-year-old woman presented with thyrotoxicosis and nonischemic cardiomyopathy. She had a "hot" nodule in the left lobe of the thyroid on sodium pertechnetate scan. She underwent a left hemithyroidectomy and isthmusectomy. Pathologic findings revealed a minimally invasive Hürthle cell carcinoma. On follow-up, the dilated cardiomyopathy had resolved. The association of thyroid carcinoma with thyrotoxicosis is rare.

CONCLUSIONS

Some Hürthle cell carcinomas can be functional and lead to thyrotoxicosis. To our knowledge, we present the first case of reversible dilated cardiomyopathy due to thyrotoxicosis originating from Hürthle cell carcinoma.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Deletion of the RNaseIII enzyme dicer in thyroid follicular cells causes hypothyroidism with signs of neoplastic alterations

Micro-RNAs (miRNAs) are small non-coding RNAs that regulate gene expression, mainly at mRNA post-transcriptional level. Functional maturation of most miRNAs requires processing of the primary transcript by Dicer, an RNaseIII-type enzyme. To date, the importance of miRNA function for normal organogenesis has been demonstrated in several mouse models of tissue-specific Dicer inactivation. However, the role of miRNAs in thyroid development has not yet been addressed. For the present study, we generated mouse models in which Dicer expression has been inactivated at two different stages of thyroid development in thyroid follicular cells. Regardless of the time of Dicer invalidation, the early stages of thyroid organogenesis, preceding folliculogenesis, were unaffected by the loss of small RNAs, with a bilobate gland in place. Nevertheless, Dicer mutant mice were severely hypothyroid and died soon after weaning unless they were substituted with T4. A conspicuous follicular disorganization was observed in Dicer mutant thyroids together with a strong down regulation of Nis expression. With increasing age, the thyroid tissue showed characteristics of neoplastic alterations as suggested by a marked proliferation of follicular cells and an ongoing de-differentiation in the center of the thyroid gland, with a loss of Pax8, FoxE1, Nis and Tpo expression. Together, our data show that loss of miRNA maturation due to Dicer inactivation severely disturbs functional thyroid differentiation. This suggests that miRNAs are mandatory to fine-tune the expression of thyroid specific genes and to maintain thyroid tissue homeostasis.

Dedifferentiation of differentiated thyroid carcinoma cell line FTC-133 is enhanced by 131I pretreatment

INTRODUCTION

Differentiated thyroid carcinoma (DTC) usually has a high iodine uptake. However, dedifferentiation of DTC with decreased or no radioiodine ((131)I) uptake is observed in clinical practice, with poor prognosis. The aim of this study was to investigate the effects of (131)I radiation on radioiodine uptake (RAIU) and the expression of thyroid-specific molecules.

METHODS

FTC-133 cells were treated with (131)I, the dosage dictated by methylthiazol tetrazolium test results and preliminary experiments. The experimental cell group was incubated with (131)I for 48 h and then cultured for 3 months in (131)I-free medium. The control group was set without (131)I. Primary cells were defined as the blank group. Following treatment, RAIU was measured with a gamma counter as the counts/cell number. Na(+)/I(-) symporter (NIS), thyroid-stimulating hormone receptor (TSHR), thyroid peroxidase (TPO) and thyroglobulin (Tg) levels were detected by Western blotting and radioimmunoassay, and their mRNAs were detected by real-time polymerase chain reaction.

RESULTS

RAIU of FTC-133 cells decreased gradually after coincubation with (131)I and did not recover even if (131)I was removed. The relative RAIU of the control and experimental groups was 0.567 and 0.182, respectively, a statistically significant difference (P<.01). Expression of NIS, TSHR, TPO and Tg decreased in the experimental group to a statistically significant degree compared to that of controls (P<.05).

CONCLUSION

Changes in the mRNA levels were in accordance with the expression of thyroid-specific proteins. Thus, FTC-133 cells undergo dedifferentiation during long-term culture in vitro, and (131)I may promote this progress.

A coherent organization of differentiation proteins is required to maintain an appropriate thyroid function in the Pendred thyroid

CONTEXT

Pendred syndrome is caused by mutations in the gene coding for pendrin, an apical Cl-/I- exchanger.

OBJECTIVE

To analyze intrathyroidal compensatory mechanisms when pendrin is lacking, we investigated the thyroid of a patient with Pendred syndrome. The expression of proteins involved in thyroid hormone synthesis, markers of oxidative stress (OS), cell proliferation, apoptosis, and antioxidant enzymes were analyzed.

RESULTS

Three morphological zones were identified: nearly normal follicles with iodine-rich thyroglobulin in the colloid (zone 1.a), small follicles without iodine-rich thyroglobulin in lumina (zone 1.b), and destroyed follicles (zone 2). In zones 1.a, dual oxidase (Duox) and thyroid peroxidase (TPO) were localized at the apical pole, OS and cell apoptosis were absent, but ClC-5 expression was strongly increased. In zones 1.b, Duox and TPO were aberrantly present and increased in the cytosol and associated with high OS, apoptosis, cell proliferation, and increased expression of peroxiredoxin-5, catalase, and dehalogenase-1 but moderate ClC-5 expression.

CONCLUSION

In conclusion, the absence of pendrin is accompanied by increased ClC-5 expression that may transiently compensate for apical iodide efflux. In more affected follicles, Duox and TPO are relocated in the cytosol, leading to abnormal intracellular thyroid hormone synthesis, which results in cell destruction presumably because intracellular OS cannot be buffered by antioxidant defenses.

Dual oxidase, hydrogen peroxide and thyroid diseases

The thyroid gland is a unique endocrine organ that requires hydrogen peroxide (H(2)O(2)) for thyroid hormone formation. The molecule for H(2)O(2) production in the thyroid gland has been known as dual oxidase 2 (DUOX2). Recently, NADPH oxidase 4 (NOX4), a homolog of the NOX family, was added as a new intracellular source of reactive oxygen species (ROS) in the human thyroid gland. This review focuses on the recent progress of the DUOX system and its possible contribution to human thyroid diseases. Also, we discuss human thyroid diseases related to abnormal H(2)O(2) generation. The DUOX molecule contains peroxidase-like and NADPH oxidase-like domains. Human thyroid gland also contains DUOX1 that shares 83% similarity with the DUOX2 gene. However, thyroid DUOX1 protein appears to play a minor role in H(2)O(2) production. DUOX proteins require DUOX maturation or activation factors (DUOXA1 or 2) for proper translocation of DUOX from the endoplasmic reticulum to the apical plasma membrane, where H(2)O(2) production takes place. Thyroid cells contain antioxidants to protect cells from the H(2)O(2)-mediated oxidative damage. Loss of this balance may result in thyroid cell dysfunction and thyroid diseases. Mutation of either DUOX2 or DUOXA2 gene is a newly recognized cause of hypothyroidism due to insufficient H(2)O(2) production. Papillary thyroid carcinoma, the most common thyroid cancer, is closely linked to the increased ROS production by NOX4. Hashimoto's thyroiditis, a common autoimmune thyroid disease in women, becomes conspicuous when iodide intake increases. This phenomenon may be explained by the abnormality of iodide-induced H(2)O(2) or other ROS in susceptible individuals. Discovery of DUOX proteins and NOX4 provides us with valuable tools for a better understanding of pathophysiology of prevalent thyroid diseases.

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

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

Radioiodine treatment for malignant thyroid disease

Radioiodine treatment for thyroid disease has been given for half a decade in Sweden. The most common indication for treatment is hyperthyroidism, when iodine uptake is high. The situation in which radioiodine treatment is used in thyroid cancer is less favourable and measures therefore have to be taken to optimize the treatment. Treatment should be performed early in the course of the disease to achieve the highest possible differentiation. Before treatment the iodine and goitrogen intake should be kept low. Stimulation of the thyrocytes by thyroid-stimulating hormone (TSH) should be high. It is conventionally achieved by thyroid hormone withdrawal rendering the patient hypothyroid, or by the recently available recombinant human TSH (rhTSH) which can be recommended for ablation of the thyroid remnant after thyroidectomy and for treatment of metastases in fragile patients unable to undergo hypothyroidism. Finally, stunning--the negative effect of a prior test dose from radioactive iodine--should be avoided.

Expression of iodine metabolism genes in human thyroid tissues: evidence for age and BRAFV600E mutation dependency

CONTEXT

Children present a higher susceptibility to developing thyroid cancer after radioiodine exposure and also a higher frequency of functional metastases than adults.

OBJECTIVE

To assess the mRNA expression of the sodium/iodide (Na(+)/I(-)) symporter (NIS), the Pendred syndrome gene (PDS), thyroperoxidase (TPO), thyroglobulin (Tg) and TSH receptor (TSH-R) in normal thyroid tissues (NTTs) and papillary thyroid carcinomas (PTCs) among different age groups.

METHODS

Analysis included 59 samples: 21 NTTs and 38 PTCs, of which 21 were the classic type (CPTC) and 17 the follicular variant (FVPTC). Patients were divided into three age groups: I (n = 16) 5-21 years, II (n = 13) 22-59 years, and III (n = 10) 60-91 years. The relative mRNA expression of the five target genes was determinate by quantitative reverse transcription polymerase chain reaction (QRT-PCR).

RESULTS

Expression of all genes was significantly higher in NTTs than in PTCs, and it was not age dependent in the NTT group. Among PTCs, the mean expression of PDS, TPO and TSH-R was significantly lower in group II than in group I. PDS, TPO and Tg expression was significantly lower in classic PTCs than in FVPTCs. The difference was related to a higher frequency of the BRAF(V600E) mutation in the former group.

CONCLUSIONS

The finding of higher PDS, TPO and TSH-R mRNA expression in paediatric vs. adult primary tumour tissues supports the hypothesis that this might contribute to the increased functional activity of metastases in the paediatric group. The finding that mRNA expression of the target genes in NTT was not age dependent does not provide an explanation for the higher susceptibility in the paediatric group.

Effectiveness of retinoic acid treatment for redifferentiation of thyroid cancer in relation to recovery of radioiodine uptake

BACKGROUND

Retinoic acid (RA) treatment has been used for redifferentiation of metastatic thyroid neoplasia that have lost radioiodine (131I) uptake with heterogeneous results.

AIM

Retrospective analysis of the recovery rate of 131I uptake after RA treatment in patients from 11 Spanish hospitals.

METHODS

Twenty-seven patients (14 men, 13 women) with papillary [21], follicular [4], and oncocytic [2] thyroid cancer initially treated with total thyroidectomy plus 131I, and with 131I negative metastatic disease, were given 13-cis RA (0.66-1.5 mg/kg for 5-12 weeks) followed by a therapeutic 131I dose (3700-7400 MBq); 3 months later thyroglobulin levels and computed tomography imaging were performed.

RESULTS

In 9 out 27 cases (33%) (8 papillary, 1 follicular) optimal positive 131I scan was observed after RA treatment; in the remaining 18, 10 had a suboptimal uptake (7 papillary, 2 follicular, 1 oncocytic) and in the rest there was no 131I uptake recovery (6 papillary, 1 follicular, 1 oncocytic). In 17 positive responses to RA (either optimal or suboptimal) in which image follow-up was available, decrease or stabilization of metastatic growth was observed in 7, while tumor mass increased at short term in the remaining 10. No major side effects were detected.

CONCLUSION

Quite a high rate of 131I uptake recovery after RA treatment may be obtained in advanced differentiated thyroid cancer, but the potential modification of the natural course of the disease is uncertain. A better biological characterization of these tumors allowing the identification of potential responders to RA may improve the outcome of RA coadjuvant therapy.

Human thyroid tumours, the puzzling lessons from E7 and RET/PTC3 transgenic mice

Human rearranged RET/PTC3 (papillary thyroid carcinoma) proto-oncogene and high-risk human papillomavirus (HPV) type 16 E7 oncogene induces in the mouse a neoplastic transformation of thyroid follicular cells. We present a detailed immuno-histological study (170 mouse thyroids: RET/PTC3, E7, wild type, 2- to 10-month-old) with cell cycle proliferation and signalling pathway indicators. The characteristics of both models are different. There is an 'oncogene dependent' cellular signature, maintained at all studied ages in the E7 model, less in the RET/PTC3 model. During tumour development a large heterogeneity occurred in the Tg-RET/PTC3 model within a same tumour or within a same thyroid lobe. The Tg-E7 model was less heterogeneous, with a dominant goitrous pattern. The solid tumour already described in the RET/PTC3 models associated with cribriform patterns, suggested 'PTC spindle cell changes' as in humans PTC rather than the equivalent of the solid human PTC. Proliferation and apoptosis in the two thyroid models are related to the causal oncogene rather than reflect a general tumorigenic process. The thyroids of RET/PTC3 mice appeared as a partial and transient model of human PTCs, whereas the Tg-E7 mice do not belong to the usual PTC type.

A molecular analysis and long-term follow-up of two siblings with severe congenital hypothyroidism carrying the IVS30+1G>T intronic thyroglobulin mutation

OBJECTIVE: To extend the molecular analysis of the IVS30+1G>T intronic thyroglobulin (TG) mutation, and to report the eleven year follow-up of the affected patients. METHOSD: Two siblings with severe congenital hypothyroidism with fetal and neonatal goiter, harboring the IVS30+1G>T mutation were included. Nodular and non-nodular thyroid tissue specimens were collected. Specific thyroid genes expression was evaluated by real-timePCR and by immunohistochemistry. RESULTS: In non-nodular tissue specific thyroid genes mRNA were reduced when compared to normal thyroid sample. In the nodule, TPO and NIS expression was very low. Microscopic examinations showed very large follicular-lumina and swollen vesicles of endoplasmatic-reticulum. Strong cytoplasmatic and low follicular-lumen TG immunostaining were detected. Intracellular NIS, membrane TPO and TSHR immunostaining had higher positivity in non-nodular sample. Both patients had a long-term adequate developmental outcome, besides one patient have been lately-treated. CONCLUSIONS: IVS30+1G>T mutation not only lead to very enlarge endoplasmatic-reticulum, but also to alterations of specific thyroid genes expression. The clinical evolution of patients harboring these mutations strengthen the concept of the influence of environment, like iodine nutrition, to determine the final phenotypic appearance.

Epigenetic dysregulation in thyroid neoplasia

Gain-of-function mutations in oncogenes have aided our understanding of the molecular mechanisms of thyroid carcinogenesis. Mutations or deletions cause inactivation of tumor suppressor genes in thyroid carcinomas. However, recent advances have disclosed the significance of epigenetic events in the development and progression of human tumorigenesis. Indeed, various tumor-suppressor genes and thyroid hormone-related genes are epigenetically silenced in thyroid tumors. This article reviews the evidence for epigenetic gene dysregulation in follicular cell-derived thyroid carcinomas including papillary thyroid carcinoma, follicular thyroid carcinoma, and undifferentiated thyroid carcinoma. The authors also discuss future applications of epigenetics as ancillary diagnostic tools and in the design of targeted therapies for thyroid cancer.