Retinoic acid increases sodium/iodide symporter mRNA levels in human thyroid cancer cell lines and suppresses expression of functional symporter in nontransformed FRTL-5 rat thyroid cells

Regulation of iodine-glucose flip-flop in SW1736 anaplastic thyroid cancer cell line

AIMS AND BACKGROUND

The alternative manner of iodide and glucose uptake found in different types of thyroid cancer, referred to flip-flop. ATC cells indicate low iodide uptake and high glucose uptake, which lack the morphology and genetic characteristics of well-differentiated tumors and become increasingly invasive. Importance placed on the discovery of innovative multi-targeted medicines to suppress the dysregulated signaling in cancer. In this research, we aimed to clarify molecular mechanism of Rutin as a phytomedicine on anaplastic thyroid cancer cell line based on iodide and glucose uptake.

MATERIAL METHODS

The MTT test was employed to test cell viability. Iodide uptake assay was performed using a spectrophotometric assay to determine iodide uptake in SW1736 cells based on Sandell-Kolthoff reaction. For glucose uptake detection, ''GOD-PAP'' enzymatic colorimetric assay was applied to measure the direct glucose levels inside of the cells. Determination of NIS, GLUT1 and 3 mRNA expression in SW1736 cells was performed by qRT-PCR. Determination of NIS, GLUT1 and 3 protein levels in SW1736 cells was performed by western blotting.

RESULTS

According to our results, Rutin inhibited the viability of SW1736 cells in a time- and dose-dependent manner. Quantitative Real-time RT-PCR analysis exposed that NIS mRNA levels were increased in Rutin treated group compared to the control group. Accordingly, western blot showed high expression of NIS protein and low expression of GLUT 1 and 3 in Rutin treated SW1736 cell line. Rutin increased iodide uptake and decreased glucose uptake in thyroid cancer cell line SW1736 compared to control group.

CONCLUSION

Multiple mechanisms point to Rutin's role as a major stimulator of iodide uptake and inhibitor of glucose uptake, including effects at the mRNA and protein levels for both NIS and GLUTs, respectively. Here in, we described the flip-flop phenomenon as a possible therapeutic target for ATC. Moreover, Rutin is first documented here as a NIS expression inducer capable of restoring cell differentiation in SW1736 cell line. It also be concluded that GLUTs as metabolic targets can be blocked specifically by Rutin for thyroid cancer prevention and treatment.

Is beta-carotene consumption associated with thyroid hormone levels?

The thyroid hormones play a pivotal role in various physiological processes, including growth, metabolism regulation, and reproduction. While non-modifiable factors are known to impact thyroid function, such as genetics and age, nutritional factors are also important. Diets rich in selenium and iodine are conventionally acknowledged to be beneficial for the production and release of thyroid hormones. Recent studies have suggested a potential link between beta-carotene, a precursor to vitamin A (retinol), and thyroid function. Beta-carotene is known for its antioxidant properties and has been shown to play a role in the prevention of various clinical conditions such as cancer and cardiovascular and neurological diseases. However, its impact on thyroid function is still unclear. Some studies have suggested a positive association between beta-carotene levels and thyroid function, while others have found no significant effect. Conversely, the hormone produced by the thyroid gland, thyroxine, enhances the conversion of beta-carotene to retinol. Furthermore, vitamin A derivatives are being explored as potential therapeutic options for thyroid malignancies. In this review, we highlight the mechanisms through which beta-carotene/retinol and thyroid hormones interact and review the findings of clinical studies examining the association between beta-carotene consumption and thyroid hormone levels. Our review underscores the need for further research to clarify the relationship between beta-carotene and thyroid function.

CRABP2 Is Associated With Thyroid Cancer Recurrence and Promotes Invasion via the Integrin/FAK/AKT Pathway

Cellular retinoic acid-binding protein 2 (CRABP2) participates in retinoid partitioning between different nuclear receptors. Recently, we identified that CRABP2 is one of the progression-associated genes in thyroid cancer. To explore the prognostic and functional significance of CRABP2, immunohistochemical analysis was performed in thyroid tissues and neoplasms. Overexpression of CRABP2 was observed in malignant thyroid neoplasms but not in benign thyroid lesions. CRABP2 expression was an independent predictive factor for recurrence-free survival in patients with differentiated thyroid cancer. Knockdown of CRABP2 reduced the sensitivity of thyroid cancer cells to retinoic acid. Importantly, CRABP2 expression in thyroid cancer cells was associated with epithelial-mesenchymal transition properties, including anoikis resistance, migration, and invasion capacity. Furthermore, invasion promoted by CRABP2 was mediated at least partly by the integrin/focal adhesion kinase/AKT pathway. In summary, CRABP2 expression is upregulated in thyroid cancer with adverse prognostic implications. The invasion-stimulating effects appear independent of canonical retinoic acid signaling and may serve as a potential therapeutic target.

Changes in chromatin accessibility are not concordant with transcriptional changes for single-factor perturbations

A major goal in the field of transcriptional regulation is the mapping of changes in the binding of transcription factors to the resultant changes in gene expression. Recently, methods for measuring chromatin accessibility have enabled us to measure changes in accessibility across the genome, which are thought to correspond to transcription factor-binding events. In concert with RNA-sequencing, these data in principle enable such mappings; however, few studies have looked at their concordance over short-duration treatments with specific perturbations. Here, we used tandem, bulk ATAC-seq, and RNA-seq measurements from MCF-7 breast carcinoma cells to systematically evaluate the concordance between changes in accessibility and changes in expression in response to retinoic acid and TGF-β. We found two classes of genes whose expression showed a significant change: those that showed some changes in the accessibility of nearby chromatin, and those that showed virtually no change despite strong changes in expression. The peaks associated with genes in the former group had lower baseline accessibility prior to exposure to signal. Focusing the analysis specifically on peaks with motifs for transcription factors associated with retinoic acid and TGF-β signaling did not reduce the lack of correspondence. Analysis of paired chromatin accessibility and gene expression data from distinct paths along the hematopoietic differentiation trajectory showed a much stronger correspondence, suggesting that the multifactorial biological processes associated with differentiation may lead to changes in chromatin accessibility that reflect rather than driving altered transcriptional status. Together, these results show many gene expression changes can happen independently of changes in the accessibility of local chromatin in the context of a single-factor perturbation.

Hormonal Crosstalk Between Thyroid and Breast Cancer

Differentiated thyroid cancer and breast cancer account for a significant portion of endocrine-related malignancies and predominately affect women. As hormonally responsive tissues, the breast and thyroid share endocrine signaling. Breast cells are responsive to thyroid hormone signaling and are affected by altered thyroid hormone levels. Thyroid cells are responsive to sex hormones, particularly estrogen, and undergo protumorigenic processes upon estrogen stimulation. Thyroid and sex hormones also display significant transcriptional crosstalk that influences oncogenesis and treatment sensitivity. Obesity-related adipocyte alterations-adipocyte estrogen production, inflammation, feeding hormone dysregulation, and metabolic syndromes-promote hormonal alterations in breast and thyroid tissues. Environmental toxicants disrupt endocrine systems, including breast and thyroid homeostasis, and influence pathologic processes in both organs through hormone mimetic action. In this brief review, we discuss the hormonal connections between the breast and thyroid and perspectives on hormonal therapies for breast and thyroid cancer. Future research efforts should acknowledge and further explore the hormonal crosstalk of these tissues in an effort to further understand the prevalence of thyroid and breast cancer in women and to identify potential therapeutic options.

Going Nuclear with Amino Acids and Proteins - Basic Biochemistry and Molecular Biology Primer for the Technologist

In recent years, there has been an influx of new tracers into the field of nuclear medicine and molecular imaging. Most of these tracers that have been FDA approved for clinical imaging exploit various mechanisms of protein biochemistry and molecular biology to bring about their actions, such as amino acid metabolism, protein folding, receptor-ligand interactions, and surface transport mechanisms. In this review, we attempt to paint a clear picture of the basic biochemistry and molecular biology of protein structure, translation, transcription, post-translational modifications, and protein targeting, in the context of the various radiopharmaceuticals currently used clinically, all in an easy-to-understand language for entry level technologists in the field. Tracer characteristics, including indications, dosage, injection-to-imaging time, and the logic behind the normal and pathophysiologic biodistribution of these newer molecular tracers, are also discussed.

Disruption by stealth - Interference of endocrine disrupting chemicals on hormonal crosstalk with thyroid axis function in humans and other animals

Thyroid hormones (THs) are important regulators of growth, development, and homeostasis of all vertebrates. There are many environmental contaminants that are known to disrupt TH action, yet their mechanisms are only partially understood. While the effects of Endocrine Disrupting Chemicals (EDCs) are mostly studied as "hormone system silos", the present critical review highlights the complexity of EDCs interfering with TH function through their interactions with other hormonal axes involved in reproduction, stress, and energy metabolism. The impact of EDCs on components that are shared between hormone signaling pathways or intersect between pathways can thus extend beyond the molecular ramifications to cellular, physiological, behavioral, and whole-body consequences for exposed organisms. The comparatively more extensive studies conducted in mammalian models provides encouraging support for expanded investigation and highlight the paucity of data generated in other non-mammalian vertebrate classes. As greater genomics-based resources become available across vertebrate classes, better identification and delineation of EDC effects, modes of action, and identification of effective biomarkers suitable for HPT disruption is possible. EDC-derived effects are likely to cascade into a plurality of physiological effects far more complex than the few variables tested within any research studies. The field should move towards understanding a system of hormonal systems' interactions rather than maintaining hormone system silos.

The relationship between thyroid disorders and vitamin A.: A narrative minireview

The terms "vitamin A" and "retinoids" encompass a group of fat-soluble compounds essential for human nutrition. Some of them (retinol, retinal, 9-cis-retinoic acid, tretinoin, and 13-cis-retinoic acid) are fully natural, while others are synthetic compounds used mostly for therapeutic purposes. Some evidence indicates that the nutritional status of these retinoids (i.e., the presence or absence of deficiency) is able to modulate thyroid gland metabolism. Vitamin A deficiency is tightly correlated with structural and functional impairment of the thyroid gland and is often associated with iodine deficiency. Furthermore, retinoids are involved in different immune functions, as well as in the process of activation, proliferation, and differentiation of regulatory T cells (Treg). This is particularly significant given the high prevalence of thyroid autoimmune disorders, whose pathogenesis seems to be related to the altered homeostasis of regulatory T cells. Retinoids are also involved in the modulation of gene expression via their interaction with nuclear receptors, and they also act as cofactors in cell growth and differentiation. The ability of retinoic acid to increase iodine uptake and sodium-iodine symporter activity in human thyroid cancer cell lines suggests that some retinoids and their derivatives may be of use in the treatment of different thyroid tumors. This minireview summarizes the current knowledge on the link between nutritional intake of vitamin A and various thyroid disorders.

Molecular mechanisms of radioactive iodine refractoriness in differentiated thyroid cancer: Impaired sodium iodide symporter (NIS) expression owing to altered signaling pathway activity and intracellular localization of NIS

The advanced, metastatic differentiated thyroid cancers (DTCs) have a poor prognosis mainly owing to radioactive iodine (RAI) refractoriness caused by decreased expression of sodium iodide symporter (NIS), diminished targeting of NIS to the cell membrane, or both, thereby decreasing the efficacy of RAI therapy. Genetic aberrations (such as BRAF, RAS, and RET/PTC rearrangements) have been reported to be prominently responsible for the onset, progression, and dedifferentiation of DTCs, mainly through the activation of mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/AKT signaling pathways. Eventually, these alterations result in a lack of NIS and disabling of RAI uptake, leading to the development of resistance to RAI therapy. Over the past decade, promising approaches with various targets have been reported to restore NIS expression and RAI uptake in preclinical studies. In this review, we summarized comprehensive molecular mechanisms underlying the dedifferentiation in RAI-refractory DTCs and reviews strategies for restoring RAI avidity by tackling the mechanisms.

Notch Signaling in Thyroid Cancer

Thyroid cancer is the most common malignancy of the endocrine system with a steadily rising incidence. The term "thyroid cancer" encompasses a spectrum of subtypes, namely papillary thyroid cancer, follicular thyroid cancer, anaplastic thyroid cancer, and medullary thyroid cancer. Each subtype differs histopathologically and in degrees of cellular differentiation, which may be in part due to signaling of the Notch pathway. The Notch pathway is an evolutionarily conserved signal transduction mechanism that regulates cell proliferation, differentiation, survival, stem cell maintenance, embryonic and adult development, epithelial-mesenchymal transition, and angiogenesis. Its role in cancer biology is controversial, as it has been shown to play both an oncogenic and tumor-suppressive role in many different types of cancers. This discordance holds true for each subtype of thyroid cancer, indicating that Notch signaling is likely cell type and context dependent. Whether oncogenic or not, Notch signaling has proven to be significantly involved in the tumorigenesis of thyroid cancer and has thus earned interest as a therapeutic target. Advancement in the understanding of Notch signaling in thyroid cancer holds great promise for the development of novel treatment strategies to benefit patients.

Targeting uptake transporters for cancer imaging and treatment

Cancer cells reprogram their gene expression to promote growth, survival, proliferation, and invasiveness. The unique expression of certain uptake transporters in cancers and their innate function to concentrate small molecular substrates in cells make them ideal targets for selective delivering imaging and therapeutic agents into cancer cells. In this review, we focus on several solute carrier (SLC) transporters known to be involved in transporting clinically used radiopharmaceutical agents into cancer cells, including the sodium/iodine symporter (NIS), norepinephrine transporter (NET), glucose transporter 1 (GLUT1), and monocarboxylate transporters (MCTs). The molecular and functional characteristics of these transporters are reviewed with special emphasis on their specific expressions in cancers and interaction with imaging or theranostic agents [e.g., I-123, I-131, ¹²³I-iobenguane (mIBG), ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) and ¹³C pyruvate]. Current clinical applications and research areas of these transporters in cancer diagnosis and treatment are discussed. Finally, we offer our views on emerging opportunities and challenges in targeting transporters for cancer imaging and treatment. By analyzing the few clinically successful examples, we hope much interest can be garnered in cancer research towards uptake transporters and their potential applications in cancer diagnosis and treatment.

The effect of retinoic acid in the ability of cold solid thyroid nodule to take up radioactive iodine: A preliminary study

One of the treatment options for benign thyroid nodules is radioactive iodine (RAI). However, this treatment is more effective for hot/warm solid thyroid nodules. Cold thyroid solid nodules are characterized by the lack of iodine uptake compared to normal thyroid tissue. Oral retinoic acid (RA) is a synthetic derivative of Vitamin A. The effect of RA on the uptake of RAI is still controversial. The aim of this study was to evaluate the effect of RA in the ability of a cold solid thyroid nodule to take up RAI. Individuals with a cold solid thyroid nodule based on ultrasonography and thyroid scintigraphy were included. Participants with liver dysfunction, smokers, and pregnant patients were excluded from the study. Each participant underwent thyroid uptake scintigraphy twice (pre- and post-RA consumption) using 35–37 MBq NaI-131. Participants consumed RA at a dose of 1 mg/kg body weight (BW) followed with 1.5 mg/kg BW. This study was approved by Dr. Hasan Sadikin General Hospital Ethic Committee. A total of 12 cold thyroid solid nodules were evaluated. The mean percentage of the nodule uptake value pre- and post-intervention was 1.11% and 0.62%, respectively (P = 0.004), while normal thyroid tissue uptake values pre- and post-intervention were 27.57% and 13.40%, respectively (P = 0.002). The percentage alteration of nodules and normal thyroid tissue uptake value were 42.4% and 51.5% lower, respectively (P = 0.354). This study showed that RA reduces the ability of cold solid thyroid nodule, as well as normal thyroid tissue, to take up RAI.

Novel targeted therapies and immunotherapy for advanced thyroid cancers

Thyroid cancer is a frequently encountered endocrine malignancy. Despite the favorable prognosis of this disease, 15–20% of differentiated thyroid cancer (DTC) cases and most anaplastic types, remain resistant to standard treatment options, including radioactive iodine (RAI). In addition, around 30% of medullary thyroid cancer (MTC) cases show resistance after surgery. The evolving understanding of disease-specific molecular therapeutic targets has led to the approval of two targeted therapies (Sorafenib and Lenvatinib) for RAI refractory DTC and another two drugs (Vandetanib and Cabozantinib) for MTC. These advanced therapies exert their effects by blocking the MAPK pathway, which has been widely correlated to different types of thyroid cancers. While these drugs remain reserved for thyroid cancer patients who failed all treatment options, their ability to improve patients’ overall survival remain hindered by their low efficacy and other molecular factors. Among these factors is the tumor’s ability to activate parallel proliferative signaling pathways other than the cascades blocked by these drugs, along with overexpression of some tyrosine kinase receptors (TKR). These facts urge the search for novel different treatment strategies for advanced thyroid cases beyond these drugs. Furthermore, the growing knowledge of the dynamic immune system interaction with tumor microenvironment has revolutionized the cancer immune therapy field. In this review, we aim to discuss the molecular escape mechanisms of thyroid tumors from these drugs. We also highlight novel therapeutic options targeting other pathways than MAPK, including PI3K pathway, ALK translocations and HER2/3 receptors and their clinical impact. We also aim to discuss the usage of targeted therapy in restoring thyroid tumor sensitivity to RAI, and finally turn to extensively discuss the role of immunotherapy as a potential alternative treatment option for advanced thyroid diseases.

Differentiation therapy revisited

The concept of differentiation therapy emerged from the fact that hormones or cytokines may promote differentiation ex vivo, thereby irreversibly changing the phenotype of cancer cells. Its hallmark success has been the treatment of acute promyelocytic leukaemia (APL), a condition that is now highly curable by the combination of retinoic acid (RA) and arsenic. Recently, drugs that trigger differentiation in a variety of primary tumour cells have been identified, suggesting that they are clinically useful. This Opinion article analyses the basis for the clinical successes of RA or arsenic in APL by assessing the respective roles of terminal maturation and loss of self-renewal. By reviewing other successful examples of drug-induced tumour cell differentiation, novel approaches to transform differentiating drugs into more efficient therapies are proposed.

Reintroducing the Sodium-Iodide Symporter to Anaplastic Thyroid Carcinoma

BACKGROUND

Anaplastic thyroid carcinoma (ATC), the most aggressive form of thyroid cancer, is unresponsive to radioiodine therapy. The current study aimed to extend the diagnostic and therapeutic application of radioiodine beyond the treatment of differentiated thyroid cancer by targeting the functional sodium-iodide symporter (NIS) to ATC.

METHODS

The study employed nanoparticle vectors (polyplexes) based on linear polyethylenimine (LPEI), shielded by polyethylene glycol (PEG) and coupled to the synthetic peptide GE11 as an epidermal growth factor receptor (EGFR)-specific ligand in order to target a NIS-expressing plasmid (LPEI-PEG-GE11/NIS) to EGFR overexpressing human thyroid carcinoma cell lines. Using ATC xenograft mouse models, transfection efficiency by ¹²³I scintigraphy and potential for systemic radioiodine therapy after systemic polyplex application were evaluated.

RESULTS

In vitro iodide uptake studies in SW1736 and Hth74 ATC cells, and, for comparison, in more differentiated follicular (FTC-133) and papillary (BCPAP) thyroid carcinoma cells demonstrated high transfection efficiency and EGFR-specificity of LPEI-PEG-GE11/NIS that correlated well with EGFR expression levels. After systemic polyplex injection, in vivo ¹²³I gamma camera imaging revealed significant tumor-specific accumulation of radioiodine in an SW1736 and an Hth74 xenograft mouse model. Radioiodine accumulation was found to be higher in SW1736 tumors, reflecting in vitro results, EGFR expression levels, and results from ex vivo analysis of NIS staining. Administration of ¹³¹I in LPEI-PEG-GE11/NIS-treated SW1736 xenograft mice resulted in significantly reduced tumor growth associated with prolonged survival compared to control animals.

CONCLUSIONS

The data open the exciting prospect of NIS-mediated radionuclide imaging and therapy of ATC after non-viral reintroduction of the NIS gene. The high tumor specificity after systemic application makes the strategy an attractive alternative for the treatment of highly metastatic ATC.

Vitamin A, endocrine tissues and hormones: interplay and interactions

Vitamin A (retinol) is a micronutrient critical for cell proliferation and differentiation. In adults, vitamin A and metabolites such as retinoic acid (RA) play major roles in vision, immune and brain functions, and tissue remodelling and metabolism. This review presents the physiological interactions of retinoids and endocrine tissues and hormonal systems. Two endocrine systems have been particularly studied. In the pituitary, retinoids targets the corticotrophs with a possible therapeutic use in corticotropinomas. In the thyroid, retinoids interfere with iodine metabolism and vitamin A deficiency aggravates thyroid dysfunction caused by iodine-deficient diets. Retinoids use in thyroid cancer appears less promising than expected. Recent and still controversial studies investigated the relations between retinoids and metabolic syndrome. Indeed, retinoids contribute to pancreatic development and modify fat and glucose metabolism. However, more detailed studies are needed before planning any therapeutic use. Finally, retinoids probably play more minor roles in adrenal and gonads development and function apart from their major effects on spermatogenesis.

Survivin and XIAP - two potential biological targets in follicular thyroid carcinoma

Follicular thyroid carcinoma's (FTC) overall good prognosis deteriorates if the tumour fails to retain radioactive iodine. Therefore, new druggable targets are in high demand for this subset of patients. Here, we investigated the prognostic and biological role of survivin and XIAP in FTC. Survivin and XIAP expression was investigated in 44 FTC and corresponding non-neoplastic thyroid specimens using tissue microarrays. Inhibition of both inhibitor of apoptosis proteins (IAP) was induced by shRNAs or specific small molecule antagonists and functional changes were investigated in vitro and in vivo. Survivin and XIAP were solely expressed in FTC tissue. Survivin expression correlated with an advanced tumour stage and recurrent disease. In addition, survivin proved to be an independent negative prognostic marker. Survivin or XIAP knockdown caused a significant reduction in cell viability and proliferation, activated caspase3/7 and was associated with a reduced tumour growth in vivo. IAP-targeting compounds induced a decrease of cell viability, proliferation and cell cycle activity accompanied by an increase in apoptosis. Additionally, YM155 a small molecule inhibitor of survivin expression significantly inhibited tumour growth in vivo. Both IAPs demonstrate significant functional implications in the oncogenesis of FTCs and thus prove to be viable targets in patients with advanced FTC.

Current Standards in Treatment of Radioiodine Refractory Thyroid Cancer

OPINION STATEMENT

Radioiodine refractory differentiated thyroid cancer (RAI-R DTC) is a challenging malignancy with limited prognosis and treatment options. Recently, clinical trials with targeted therapies have advanced the outlook of these patients, and inhibition of the vascular endothelial growth factor (VEGF) axis has led to the approval of small-molecule tyrosine kinase inhibitors (TKIs) for first-line treatment of radioiodine refractory disease. In addition to approved therapies (sorafenib and lenvatinib), other multi-targeted tyrosine kinase inhibitors that are commercially available have been recognized as viable treatment options for RAI-R DTC. Our preference is to initially use lenvatinib, given the dramatic progression-free survival (PFS) improvement versus placebo, with the caveat that 24 mg daily is not often tolerated and lower doses often used. In patients with BRAF V600E mutation, BRAF inhibitors are now considered for treatment, especially if patients are at high risk from antiangiogenic therapy. Research is continuing to evolve in identifying mechanisms related to radioiodine refractoriness, and trials are evaluating therapeutic molecules to overcome this resistance. Clinical care of patients with RAI-R DTC requires careful consideration of both patient and disease characteristics. Many patients with asymptomatic and indolent disease can be followed for years without treatment while others with high volume or rapidly progressive disease merit early intervention.

Resveratrol has anti-thyroid effects both in vitro and in vivo

Resveratrol is a natural polyphenol with antioxidant, anti-inflammatory, and antiproliferative properties. We have shown previously that resveratrol decreases sodium/iodide symporter expression and iodide uptake in thyrocytes, both in vitro and in vivo. In the present study, we further investigated the effects of resveratrol, with evaluation of the expression of additional thyroid-specific genes in the FRTL-5 rat thyroid cell line: thyroglobulin, thyroid peroxidase, TSH receptor, Nkx2-1, Foxe1 and Pax8. We observed decreased expression of these genes in FRTL-5 cells treated with 10 μM resveratrol. The effects of resveratrol was further evaluated in vivo using Sprague-Dawley rats treated with resveratrol 25 mg/kg body weight intraperitoneally, for 60 days. No clinical signs of hypothyroidism were seen, although the treated rats showed significant increase in thyroid size. Serum TSH and thyroid hormone levels were in the normal range, with significantly higher TSH seen in resveratrol-treated rats, compared with control rats. Histological and immunohistochemical analyses confirmed increased proliferative activity in the thyroid from resveratrol-treated rats. These data suggest that resveratrol acts as a thyroid disruptor and a goitrogen, which indicates the need for caution as a supplement and for therapeutic uses.

Flavonoids, Thyroid Iodide Uptake and Thyroid Cancer-A Review

Thyroid cancer is the most common malignant tumor of the endocrine system and the incidence has been increasing in recent years. In a great part of the differentiated carcinomas, thyrocytes are capable of uptaking iodide. In these cases, the main therapeutic approach includes thyroidectomy followed by ablative therapy with radioiodine. However, in part of the patients, the capacity to concentrate iodide is lost due to down-regulation of the sodium-iodide symporter (NIS), the protein responsible for transporting iodide into the thyrocytes. Thus, therapy with radioiodide becomes ineffective, limiting therapeutic options and reducing the life expectancy of the patient. Excessive ingestion of some flavonoids has been associated with thyroid dysfunction and goiter. Nevertheless, studies have shown that some flavonoids can be beneficial for thyroid cancer, by reducing cell proliferation and increasing cell death, besides increasing NIS mRNA levels and iodide uptake. Recent data show that the flavonoids apingenin and rutin are capable of increasing NIS function and expression in vivo. Herein we review literature data regarding the effect of flavonoids on thyroid cancer, besides the effect of these compounds on the expression and function of the sodium-iodide symporter. We will also discuss the possibility of using flavonoids as adjuvants for therapy of thyroid cancer.

Integrated data analysis reveals potential drivers and pathways disrupted by DNA methylation in papillary thyroid carcinomas

BACKGROUND

Papillary thyroid carcinoma (PTC) is a common endocrine neoplasm with a recent increase in incidence in many countries. Although PTC has been explored by gene expression and DNA methylation studies, the regulatory mechanisms of the methylation on the gene expression was poorly clarified. In this study, DNA methylation profile (Illumina HumanMethylation 450K) of 41 PTC paired with non-neoplastic adjacent tissues (NT) was carried out to identify and contribute to the elucidation of the role of novel genic and intergenic regions beyond those described in the promoter and CpG islands (CGI). An integrative and cross-validation analysis were performed aiming to identify molecular drivers and pathways that are PTC-related.

RESULTS

The comparisons between PTC and NT revealed 4995 methylated probes (88% hypomethylated in PTC) and 1446 differentially expressed transcripts cross-validated by the The Cancer Genome Atlas data. The majority of these probes was found in non-promoters regions, distant from CGI and enriched by enhancers. The integrative analysis between gene expression and DNA methylation revealed 185 and 38 genes (mainly in the promoter and body regions, respectively) with negative and positive correlation, respectively. Genes showing negative correlation underlined FGF and retinoic acid signaling as critical canonical pathways disrupted by DNA methylation in PTC. BRAF mutation was detected in 68% (28 of 41) of the tumors, which presented a higher level of demethylation (95% hypomethylated probes) compared with BRAF wild-type tumors. A similar integrative analysis uncovered 40 of 254 differentially expressed genes, which are potentially regulated by DNA methylation in BRAFV600E-positive tumors. The methylation and expression pattern of six selected genes (ERBB3, FGF1, FGFR2, GABRB2, HMGA2, and RDH5) were confirmed as altered by pyrosequencing and RT-qPCR.

CONCLUSIONS

DNA methylation loss in non-promoter, poor CGI and enhancer-enriched regions was a significant event in PTC, especially in tumors harboring BRAFV600E. In addition to the promoter region, gene body and 3'UTR methylation have also the potential to influence the gene expression levels (both, repressing and inducing). The integrative analysis revealed genes potentially regulated by DNA methylation pointing out potential drivers and biomarkers related to PTC development.

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

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

Thyrotropin and Insulin-Like Growth Factor 1 Receptor Crosstalk Upregulates Sodium-Iodide Symporter Expression in Primary Cultures of Human Thyrocytes

BACKGROUND

Major regulation of thyroid gland function is mediated by thyrotropin (TSH) activating the TSH receptor (TSHR) and inducing upregulation of genes involved in thyroid hormone synthesis. Evidence suggests that the insulin-like growth factor 1 (IGF-1) receptor (IGF-1R) may play a role in regulating TSHR functional effects. This study examined the potential role of TSHR/IGF-1R crosstalk in primary cultures of human thyrocytes.

RESULTS

TSH/IGF-1 co-treatment elicited additive effects on thyroglobulin (TG), thyroperoxidase (TPO), and deiodinase type 2 (DIO2) mRNA levels but synergistic effects on sodium-iodide symporter (NIS) mRNA. Similar cooperativity was seen on the level of TG protein secretion (additive) and NIS protein expression (synergistic). The IGF-1R tyrosine kinase inhibitor linsitinib inhibited TSH-stimulated upregulation of NIS but not TG, indicating that NIS regulation is in part IGF-1R dependent and occurs via receptor crosstalk. Cooperativity was not seen at the level of cAMP/protein kinase A (PKA) signaling, IGF-1R phosphorylation, or Akt activation. However, TSH and IGF-1 synergistically activated ERK1/2. Pharmacological inhibition of ERK1/2 by the MEK1/2 inhibitor U0126 and of Akt by MK-2206 virtually abolished NIS stimulation by TSH and the synergistic effect of IGF-1.

CONCLUSION

As linsitinib inhibited upregulation of NIS stimulated by TSH alone, it is concluded that crosstalk between TSHR and IGF-1R, without agonist activation of IGF-1R, plays a role in NIS regulation in human thyrocytes via a mechanism involving ERK1/2 and/or Akt. Fully understanding the nature of this crosstalk has clinical implications for the treatment of thyroid diseases, including thyroid cancer.

Identification of benign and malignant thyroid nodules by in vivo iodine concentration measurement using single-source dual energy CT: A retrospective diagnostic accuracy study

This study proposed to determine whether in vivo iodine concentration measurement by single-source dual energy (SSDE) CT can improve differentiation between benign and malignant thyroid nodules. In total, 53 patients presenting with thyroid nodules underwent SSDE CT scanning. Iodine concentrations were measured for each nodule and normal thyroid tissue using the GSI-viewer image analysis software. A total of 26 thyroid nodules were malignant in 26 patients and confirmed by surgery; 33 nodules from 27 patients were benign, with 10 confirmed by surgery and others after follow-up. Iodine concentrations with plain CT were significantly lower in malignant than benign nodules (0.47 ± 0.20 vs 1.17 ± 0.38 mg/mL, P = 0.00). Receiver operating characteristic (ROC) curve showed an area under the curve (AUC) of 0.93; with a cutoff of 0.67, iodine concentration showed 92.3% sensitivity and 88.5% specificity in diagnosing malignancy. Iodine concentration obtained by enhanced and plain CT were significantly higher in malignant than benign nodules (9.05 ± 3.35 vs 3.46 ± 2.24 mg/mL, P = 0.00). ROC curve analysis showed an AUC of 0.93; with a cutoff value of 3.37, iodine concentration displayed 78% sensitivity, 95% specificity in diagnosing malignancy. Combining unenhanced with enhanced iodine concentrations, the diagnostic equation was: Y = -8.641 × unenhanced iodine concentration + 0.663 × iodine concentration. ROC curve showed an AUC of 0.98 (95% CI, 0.94, 1.00). With Y ≥ -2 considered malignancy, diagnostic sensitivity and specificity were 96%, 96.3%, respectively. This study concluded that SSDE CT can detect the differences in iodine uptake and blood supply between benign and malignant thyroid lesions.

Thyroid malignant neoplasm-associated biomarkers as targets for oncolytic virotherapy

Biomarkers associated with thyroid malignant neoplasm (TMN) have been widely applied in clinical diagnosis and in research oncological programs. The identification of novel TMN biomarkers has greatly improved the efficacy of clinical diagnosis. A more accurate diagnosis may lead to better clinical outcomes and effective treatments. However, the major deficiency of conventional chemotherapy and radiotherapy is lack of specificity. Due to the macrokinetic interactions, adverse side effects will occur, including chemotherapy and radiotherapy resistance. Therefore, a new treatment is urgently needed. As an alternative approach, oncolytic virotherapy may represent an opportunity for treatment strategies that can more specifically target tumor cells. In most cases, viral entry requires the expression of specific receptors on the surface of the host cell. Currently, molecular virologists and gene therapists are working on engineering oncolytic viruses with altered tropism for the specific targeting of malignant cells. This review focuses on the strategy of biomarkers for the production of novel TMN oncolytic therapeutics, which may improve the specificity of targeting of tumor cells and limit adverse effects in patients.

Emerging strategies for managing differentiated thyroid cancers refractory to radioiodine

Efficient treatment of radio refractory thyroid cancer is still a major challenge. The recent identification of genetic and epigenetic alterations present in almost all differentiated tumors has revealed novel molecular targets, which can hopefully be exploited to create new treatments for these tumors. This review looks briefly at some of the innovative strategies currently being investigated for the treatment the radioiodine-resistant thyroid cancers.

PI3K/Akt/mTOR: A promising therapeutic target for non-medullary thyroid carcinoma

Thyroid carcinoma (TC) is the most common endocrine malignancy. The pathogenesis of TC is complex and involves multiple genetic events that lead to activation of oncogenic pathways such as the MAP kinase (MAPK) pathway and the PI3K/Akt/mTOR pathway. The PI3K/Akt pathway has emerged as an important player in the pathogenesis of TC, particularly in follicular and advanced anaplastic or poorly differentiated TC. Because these patients have a poor prognosis, particularly when their tumors become resistant to the conventional treatment with radioactive iodine, efforts have been made to identify possible targets for therapy within these pathways. Orally available drugs targeting the PI3K/Akt/mTOR pathway are being used with success in treatment of several types of malignant tumors. There is an increasing amount of preclinical and clinical data supporting that this pathway may represent a promising target for systemic therapy in TC. The present review focuses on the most recent developments on the role of the PI3K/Akt pathway in the pathogenesis of non-medullary TC and will provide insight into how this pathway can be targeted either alone or in the context of multimodal therapeutic strategies for treatment of advanced TC.

Codon-optimized human sodium iodide symporter (opt-hNIS) as a sensitive reporter and efficient therapeutic gene

To generate a more efficient in vivo reporter and therapeutic gene, we optimized the coding sequence of the human sodium/iodide symporter (NIS) gene by replacing NIS DNA codons from wild type to new codons having the highest usage in human gene translation. The Codon Adaptation Index (CAI), representing the number of codons effective for human expression, was much improved (0.79 for hNIS, 0.97 for opt-hNIS). Both wild-type (hNIS) and optimized human NIS (opt-hNIS) were cloned into pcDNA3.1 and pMSCV vectors for transfection. Various cancer cell lines such as thyroid (TPC-1, FRO, B-CPAP), breast (MDA-MB-231), liver (Hep3B), cervical (HeLa), and glioma (U87MG) were transfected with pcDNA3.1/hNIS or pcDNA3.1/opt-hNIS. ¹²⁵I uptake by opt-hNIS-expressing cells was 1.6 ~ 2.1 times higher than uptake by wild-type hNIS-expressing cells. Stable cell lines were also established by retroviral transduction using pMSCV/hNIS or pMSCV/opt-hNIS, revealing higher NIS protein levels and ¹²⁵I uptake in opt-hNIS-expressing cells than in hNIS-expressing cells. Moreover, scintigraphic images from cell plates and mouse xenografts showed stronger signals from opt-hNIS-expressing cells than hNIS-expressing cells, and radioactivity uptake by opt-hNIS-expressing tumors was 2.3-fold greater than that by hNIS-expressing tumors. To test the efficacy of radioiodine therapy, mouse xenograft models were established with cancer cells expressing hNIS or opt-hNIS. ¹³¹I treatment reduced tumor sizes of hNIS- and opt-hNIS-expressing tumors to 0.57- and 0.27- fold, respectively, compared to their sizes before therapy, suggesting an improved therapeutic effect of opt-hNIS. In summary, this study shows that codon optimization strongly increases hNIS protein levels and radioiodine uptake, thus supporting opt-hNIS as a more sensitive reporter and efficient therapeutic gene.

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.

Advanced radioiodine-refractory differentiated thyroid cancer: the sodium iodide symporter and other emerging therapeutic targets

Approximately 30% of patients with advanced, metastatic differentiated thyroid cancer have radioiodine-refractory disease, based on decreased expression of the sodium iodide symporter SLC5A5 (NIS), diminished membrane targeting of NIS, or both. Patients with radioiodine-refractory disease, therefore, are not amenable to (131)I therapy, which is the initial systemic treatment of choice for non-refractory metastatic thyroid cancer. Patients with radioiodine-refractory cancer have historically had poor outcomes, partly because these cancers often respond poorly to cytotoxic chemotherapy. In the past decade, however, considerable progress has been made in delineating the molecular pathogenesis of radioiodine-refractory thyroid cancer. As a result of the identification of key genetic and epigenetic alterations and dysregulated signalling pathways, multiple biologically targeted drugs, in particular tyrosine-kinase inhibitors, have been evaluated in clinical trials with promising results and have begun to meaningfully impact clinical practice. In this Review, we summarise the current knowledge of the molecular pathogenesis of advanced differentiated thyroid cancer and discuss findings from clinical trials of targeted drugs in patients with radioiodine-refractory disease. Additionally, we focus on the molecular basis of loss of NIS expression, function, or both in refractory disease, and discuss preclinical and clinical data on restoration of radioiodine uptake.

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.

Hesperetin activates the Notch1 signaling cascade, causes apoptosis, and induces cellular differentiation in anaplastic thyroid cancer

BACKGROUND

Anaplastic thyroid cancer (ATC) is characterized by very aggressive growth with undifferentiated features. Recently, it has been reported that the Notch1 signaling pathway, which affects thyrocyte proliferation and differentiation, is inactivated in ATC. However, it remains largely unknown whether using Notch1 activating compounds can be an effective therapeutic strategy in ATC. Therefore, in this study, we aimed to evaluate the drug effects of a potential Notch activator hesperetin on ATC cell.

METHODS

A unique ATC cell line HTh7 was used to evaluate the drug effects of hesperetin. The Notch1 activating function and cell proliferation were evaluated. The mechanism of growth regulation was investigated by the detection of apoptotic markers. The expression levels of thyrocyte-specific genes were quantified for ATC redifferentiation.

RESULTS

Upregulated expression of Notch1 and its downstream effectors hairy and enhancer of split 1 (Hes1) and Hes1 related with YRPW motif was observed in hesperetin-treated ATC cells. The enhanced luciferase signal also confirmed the functional activity of hesperetin-induced Notch1 signaling. Hesperetin led to a time- and dose-dependent decrease in ATC cell proliferation. The cell-growth inhibition was mainly caused by apoptosis as evidenced by increased levels of cleaved poly ADP ribose polymerase and cleaved caspase-3 as well as decreased survivin. Additionally, hesperetin induced the expression levels of thyrocyte-specific genes including thyroid transcription factor 1 (TTF1), TTF2, paired box gene 8, thyroid stimulating hormone receptor, and sodium/iodide symporter.

CONCLUSIONS

Hesperetin activates the Notch1 signaling cascade and suppresses ATC cell proliferation mainly via apoptosis. Hesperetin also induces cell redifferentiation of ATC, which could be useful clinically.

Retinoic acid therapy in patients with radioiodine negative differentiated thyroid cancer and clinical or biochemical evidence of disease: An initial experience

BACKGROUND

Dedifferentiation of thyroid follicular cells renders radioiodine therapy ineffective in patients of differentiated thyroid cancer (DTC). An alternative therapy to treat the disease or reinduce radioiodine uptake is necessary.

MATERIALS AND METHODS

We evaluated the role of retinoic acid therapy in 13 cases of DTC with raised thyroglobulin and/or clinically evident disease. Retinoic acid was given in a dose of 1.5 mg/kg for a period ranging between 1.5 and 18 months.

RESULTS

Age of the patients was between 18 and 65 years with a median of 49 years. Ten patients had papillary while two had follicular and one patient had mixed papillary and follicular thyroid cancer. Mean radioiodine given before starting retinoic acid was 164 mCi. Mean duration of therapy was 6.4 months. Thyroglobulin decreased in 2 patients and increased in 11 patients at the end of therapy. Radioiodine uptake was demonstrable in six patients, though faintly, while 7 cases showed no uptake. Based on the clinical and biochemical parameters, four patients had progressive disease, eight had stable disease and one patient showed partial response. Of the six patients with reinduction of radioiodine uptake, three had biochemical progression and the other three had stable disease.

CONCLUSION

Our findings suggest that retinoic acid therapy may induce radioiodine uptake and reduce serum thyroglobulin levels in some patients with DTC, but whether this results in clinically significant response can only be ascertained on long-term follow-up.

Retinoids: novel immunomodulators and tumour-suppressive agents?

Retinoids play important roles in the transcriptional activity of normal, degenerative and tumour cells. Retinoid analogues may be promising therapeutic agents for the treatment of immune disorders as different as type I diabetes and systemic lupus erythematosus. In addition, the use of retinoids in cancer treatment has progressed significantly in the last two decades; thus, numerous retinoid compounds have been synthesized and tested. In this paper, the actual or potential use of retinoids as immunomodulators or tumour-suppressive agents is discussed.

Radioiodine therapy in benign thyroid diseases: effects, side effects, and factors affecting therapeutic outcome

Radioiodine ((131)I) therapy of benign thyroid diseases was introduced 70 yr ago, and the patients treated since then are probably numbered in the millions. Fifty to 90% of hyperthyroid patients are cured within 1 yr after (131)I therapy. With longer follow-up, permanent hypothyroidism seems inevitable in Graves' disease, whereas this risk is much lower when treating toxic nodular goiter. The side effect causing most concern is the potential induction of ophthalmopathy in predisposed individuals. The response to (131)I therapy is to some extent related to the radiation dose. However, calculation of an exact thyroid dose is error-prone due to imprecise measurement of the (131)I biokinetics, and the importance of internal dosimetric factors, such as the thyroid follicle size, is probably underestimated. Besides these obstacles, several potential confounders interfere with the efficacy of (131)I therapy, and they may even interact mutually and counteract each other. Numerous studies have evaluated the effect of (131)I therapy, but results have been conflicting due to differences in design, sample size, patient selection, and dose calculation. It seems clear that no single factor reliably predicts the outcome from (131)I therapy. The individual radiosensitivity, still poorly defined and impossible to quantify, may be a major determinant of the outcome from (131)I therapy. Above all, the impact of (131)I therapy relies on the iodine-concentrating ability of the thyroid gland. The thyroid (131)I uptake (or retention) can be stimulated in several ways, including dietary iodine restriction and use of lithium. In particular, recombinant human thyrotropin has gained interest because this compound significantly amplifies the effect of (131)I therapy in patients with nontoxic nodular goiter.

The Effect of Tanespimycin (17-AAG) on Radioiodine Accumulation in Sodium-Iodide Symporter Expressing Cells

PURPOSE

The heat shock protein 90 inhibitor, tanespimycin, is an anticancer agent known to increase iodine accumulation in normal and cancerous thyroid cells. Iodine accumulation is regulated by membrane proteins such as sodium iodide symporter (NIS) and pendrin (PDS), and thus we attempted to characterize the effects of tanespimycin on those genes.

METHODS

Cells were incubated with tanespimycin in order to evaluate (125)I accumulation and efflux ability. Radioiodine uptake and efflux were measured by a gamma counter and normalized by protein amount. RT-PCR were performed to measure the level of gene expression.

RESULTS

After tanespimycin treatment, (125)I uptake was increased by ∼2.5-fold in FRTL-5, hNIS-ARO, and hNIS-MDA-MB-231 cells, but no changes were detected in the hNIS-HeLa cells. Tanespimycin significantly reduced the radioiodine efflux rate only in the FRTL-5 cells. In the FRTL-5 and hNIS-ARO cells, PDS mRNA levels were markedly reduced; the only other observed alteration in the levels of NIS mRNA after tanespimycin treatment was an observed increase in the hNIS-ARO cells.

CONCLUSIONS

These results indicate that cellular responses against tanespimycin treatment differed between the normal rat thyroid cells and human cancer cells, and the reduction in the (125)I efflux rate by tanespimycin in the normal rat thyroid cells might be attributable to reduced PDS gene expression.

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.

Regulation of sodium iodide symporter gene expression by Rac1/p38β mitogen-activated protein kinase signaling pathway in MCF-7 breast cancer cells

Activation of p38 MAPK is a key pathway for cell proliferation and differentiation in breast cancer and thyroid cells. The sodium/iodide symporter (NIS) concentrates iodide in the thyroid and lactating breast. All-trans-retinoic acid (tRA) markedly induces NIS activity in some breast cancer cell lines and promotes uptake of β-emitting radioiodide (131)I sufficient for targeted cytotoxicity. To identify a signal transduction pathway that selectively stimulates NIS expression, we investigated regulation by the Rac1-p38 signaling pathway in MCF-7 breast cancer cells and compared it with regulation in FRTL-5 rat thyroid cells. Loss of function experiments with pharmacologic inhibitors and small interfering RNA, as well as RT-PCR analysis of p38 isoforms, demonstrated the requirement of Rac1, MAPK kinase 3B, and p38β for the full expression of NIS in MCF-7 cells. In contrast, p38α was critical for NIS expression in FRTL-5 cells. Treatment with tRA or overexpression of Rac1 induced the phosphorylation of p38 isoforms, including p38β. A dominant negative mutant of Rac1 abolished tRA-induced phosphorylation in MCF-7 cells. Overexpression of p38β or Rac1 significantly enhanced (1.9- and 3.9-fold, respectively), the tRA-stimulated NIS expression in MCF-7 cells. This study demonstrates differential regulation of NIS by distinct p38 isoforms in breast cancer cells and thyroid cells. Targeting isoform-selective activation of p38 may enhance NIS induction, resulting in higher efficacy of (131)I concentration and treatment of breast cancer.

Bexarotene via CBP/p300 induces suppression of NF-κB-dependent cell growth and invasion in thyroid cancer

PURPOSE

Retinoic acid (RA) treatment has been used for redifferentiation of metastatic thyroid cancer with loss of radioiodine uptake. The aim of this study was to improve the understanding of RA resistance and investigate the role of bexarotene in thyroid cancer cells.

EXPERIMENTAL DESIGN

A model of thyroid cancer cell lines with differential response to RA was used to evaluate the biological effects of retinoid and rexinoid and to correlate this with RA receptor levels. Subsequently, thyroid cancer patients were treated with 13-cis RA and bexarotene and response evaluated on radioiodine uptake reinduction on posttherapy scan and conventional imaging.

RESULTS

In thyroid cancer patients, 13-cis RA resistance can be bypassed in some tumors by bexarotene. A decreased tumor growth without differentiation was observed confirming our in vitro data. Indeed, we show that ligands of RARs or RXRs exert different effects in thyroid cancer cell lines through either differentiation or inhibition of cell growth and invasion. These effects are associated with restoration of RARβ and RXRγ levels and downregulation of NF-κB targets genes. We show that bexarotene inhibits the transactivation potential of NF-κB in an RXR-dependent manner through decreased promoter permissiveness without interfering with NF-κB nuclear translocation and binding to its responsive elements. Inhibition of transcription results from the release of p300 coactivator from NF-κB target gene promoters and subsequent histone deacetylation.

CONCLUSION

This study highlights dual mechanisms by which retinoids and rexinoids may target cell tumorigenicity, not only via RARs and RXRs, as expected, but also via NF-κB pathway.

Combined therapy with 131I and retinoic acid in Korean patients with radioiodine-refractory papillary thyroid cancer

PURPOSE

The aim of this study was to assess the clinical outcome of redifferentiation therapy using retinoic acid (RA) in combination with 131I therapy, and to identify biological parameters that predict therapeutic response in Korean patients with radioiodine-refractory papillary thyroid carcinoma (PTC).

MATERIALS AND METHODS

A total of 47 patients (13 men, 34 women; age 54.2±13.6 years) with radioiodine-refractory PTC underwent therapy consisting of consecutive treatment with 131I and RA. Each 131I/RA treatment cycle involved the administration of oral isotretinoin for 6 weeks at 1-1.5 mg/kg daily followed by a single oral dose of 131I (range 5.5-16.7 GBq). Therapeutic responses were determined using serum thyroglobulin (Tg) levels and the change in tumour size 6 months after completing the 131I/RA therapy. Biological parameters and pathological parameters before and after combined therapy were compared.

RESULTS

After completing 131I/RA therapy, 1 patient showed a complete response, 9 partial response, 9 stable disease, and 28 progressive disease, representing an overall response rate of 21.3%. Univariate analysis revealed that an age of <45 years and a persistently high serum Tg level were related to a good response. No clinical response was achieved when metastases showing no iodine uptake were present. Multivariate regression analysis showed that an age of <45 years was significantly associated with a good response. Of the 24 patients with well-differentiated carcinoma, 5 (20.8%) responded to 131I/RA therapy, whereas all 6 patients with poorly differentiated carcinoma failed to respond.

CONCLUSION

131I/RA therapy was found to elicit a response rate of 21.3% among patients with radioiodine-refractory PTC, and an age of <45 years was found to be significantly associated with a good response.

KT5823 differentially modulates sodium iodide symporter expression, activity, and glycosylation between thyroid and breast cancer cells

Na(+)/I(-) symporter (NIS)-mediated iodide uptake into thyroid follicular cells serves as the basis of radioiodine therapy for thyroid cancer. NIS protein is also expressed in the majority of breast tumors, raising potential for radionuclide therapy of breast cancer. KT5823, a staurosporine-related protein kinase inhibitor, has been shown to increase thyroid-stimulating hormone-induced NIS expression, and thus iodide uptake, in thyroid cells. In this study, we found that KT5823 does not increase but decreases iodide uptake within 0.5 h of treatment in trans-retinoic acid and hydrocortisone-treated MCF-7 breast cancer cells. Moreover, KT5823 accumulates hypoglycosylated NIS, and this effect is much more evident in breast cancer cells than thyroid cells. The hypoglycosylated NIS is core glycosylated, has not been processed through the Golgi apparatus, but is capable of trafficking to the cell surface. KT5823 impedes complex NIS glycosylation at a regulatory point similar to brefeldin A along the N-linked glycosylation pathway, rather than targeting a specific N-glycosylated site of NIS. KT5823-mediated effects on NIS activity and glycosylation are also observed in other breast cancer cells as well as human embryonic kidney cells expressing exogenous NIS. Taken together, KT5823 will serve as a valuable pharmacological reagent to uncover mechanisms underlying differential NIS regulation between thyroid and breast cancer cells at multiple levels.

Follow-up of patients treated with retinoic acid for the control of radioiodine non-responsive advanced thyroid carcinoma

During thyroid tumor progression, cellular de-differentiation may occur and it is commonly accompanied by metastatic spread and loss of iodine uptake. Retinoic acid (RA) administration might increase iodine uptake in about 40% of patients, suggesting that RA could be a promising therapeutic option for radioiodine non-responsive thyroid carcinoma, although a prospective study with a long-term follow-up has not been reported. This was a clinical prospective study assessing the value of 13-cis-RA in patients with advanced thyroid carcinoma and its impact on major outcomes such as tumor regression and cancer-related death with a long-term follow-up of patients submitted to radioiodine (¹³¹I) therapy after RA administration. Sixteen patients with inoperable disease and no significant radioiodine uptake on post-therapy scan were selected. Patients were treated orally with 13-cis-RA at a dose of 1.0 to 1.5 mg·kg⁻¹·day⁻¹ for 5 weeks and then submitted to radioiodine therapy (150 mCi) after thyroxine withdrawal. A whole body scan was obtained 5 to 7 days after the radioactive iodine therapy. RECIST criteria were used to evaluate the response. An objective partial response rate was observed in 18.8%, a stable disease rate in 25% and a progression disease rate in 56.2%. Five patients died (62.5%) in the group classified as progression of disease. Progression-free survival rate (PFS) ranged from 72 to 12 months, with a median PFS of 26.5 months. RA may be an option for advanced de-differentiated thyroid cancer, due to the low rate of side effects.

The effects of amitrole on thyroglobulin and iodide uptake in FRTL-5 cells

Thyroid is a frequent target for endocrine effects of pesticides. Thyroglobulin (TG) and iodide uptake are crucial to thyroid hormone synthesis and may be targets of thyroid-disrupting chemicals. In our study, thyroid follicular FRTL-5 cells were treated with amitrole, an inhibitor of the thyroid peroxidase (TPO), and the effects on TG and total iodide uptake were observed. The results showed that 1-100 mg/L amitrole had no marked effects on FRTL-5 cell proliferation and DNA synthesis. However, it significantly increased the transcription of tg gene and inhibited the total iodide uptake. And 10-100 mg/L amitrole significantly decreased TG in the culture medium. The data suggests amitrole may disrupt the expression and secretion of TG and iodide uptake.

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

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

Sodium iodide symporter and the radioiodine treatment of thyroid carcinoma

Since the specific accumulation of iodide in thyroid was found in 1915, radioiodine has been widely applied to diagnose and treat thyroid cancer. Iodide uptake occurs across the membrane of the thyroid follicular cells and cancer cells through an active transporter process mediated by the sodium iodide symporter (NIS). The NIS coding genes were cloned and identified from rat and human in 1996. Evaluation of the NIS gene and protein expression is critical in the management of thyroid cancer, and several approaches have been tried to increase NIS levels. Identification of the NIS gene has provided a means of expanding its role in the radionuclide gene therapy of nonthyroidal cancers as well as thyroid cancer. In this article, we explain the relationship between NIS expression and the treatment of thyroid carcinoma with I-131, and we include a review of the results of our experimental and clinical trials.

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.

Effects of theophylline on radioiodide uptake in MCF-7 breast cancer and NIS gene-transduced SNU-C5 colon cancer cells

BACKGROUND

We investigated whether theophylline has the potential to increase radioiodide uptake in nonthyroidal cancer cells.

MATERIALS AND METHODS

MCF-7 cells that express endogenous sodium/iodide symporter (NIS) and SNU-C5 cells adenovirally transduced with the human NIS gene (SNU-C5/NIS) were treated with 10(-7)-2x10(-4) mol/L theophylline for 24 hours before incubation with (125)I, and then, radioiodide uptake and retention were measured. NIS expression was assessed by immunohistochemistry and Western blot analysis, using an antihuman NIS monoclonal antibody.

RESULTS

Theophylline at 10(-6)-2x10(-4) mol/L significantly and dose dependently augmented radioiodide uptake in MCF-7 cells and at 10(-6)-10(-5) mol/L in SNU-C5/NIS cells, without affecting radioiodide efflux. Abrogation by KClO(4)(-) demonstrated that the effect of theophylline occurred through specific iodide transport. Immunohistochemistry revealed dose-dependent increases of NIS staining in MCF-7 and SNU-C5/NIS cells by 10(-6)-10(-4) and 10(-6)-10(-5) mol/L theophylline, respectively. Western blot analysis demonstrated similar findings, showing increased expression of NIS on the membrane of SNU-C5/NIS and MCF-7 cells by theophylline treatment.

CONCLUSIONS

Theophylline can augment radioiodide uptake in breast cancer cells and NIS gene-transduced cancer cells through the upregulation of NIS expression. Therefore, further investigations are warranted to explore the potential utility of this phenomenon for enhancing radioiodide-based imaging and therapies of NIS gene-transduced cancer cells.

13-cis-retinoic acid re-differentiation therapy and recombinant human thyrotropin-aided radioiodine treatment of non-Functional metastatic thyroid cancer: a single-center, 53-patient phase 2 study

In 30-50% of patients with metastatic non-medullary thyroid cancer the metastases are not radioiodine-avid and so there is no effective treatment. Retinoids have demonstrated inhibition of thyroid tumor growth and induction of radioiodine uptake. The aim of our study was to assess benefits of the retinoic acid (RA) treatment to re-differentiate non-functional NMTC metastases.

PATIENTS AND METHODS

In this prospective study, 53 patients with radioiodine non avid metastatic disease (45) or hyperthyroglobulinemia (8) were treated with 13-cis-retinoic acid (13-CRA) [1.0 mg/kg/day over 1st week and then 1.5 mg/kg] for six weeks prior to I-131 treatment performed under rhTSH stimulation. The re-differentiating effect of RA was evaluated by serum thyroglobulin (Tg) monitoring before and after cessation of RA treatment and by qualitative analysis of iodine uptake on the post-therapeutic whole body scan (rxWBS).

RESULTS

13-CRA induced radioiodine uptake in 9 (17%) of patients. In the univariate analysis neither the patient's gender, age, tumor histopathology, uptake in thyroid bed nor time since thyroid cancer diagnosis was associated with results of rxWBS.41 (77%) patients were evaluable for Tg response before and after to 13-CRA treatment. There was a statistically significant increase in median Tg level (60 v. 90 ng/ml, p < 0.05). There was no difference in Tg increase between scintigraphic responders and non-responders.13-CRA and RIT was repeated at least once in 8 of 9 scintigraphic responders. None of them showed tumor regression by radiological imaging within 12 months after the first treatment, 4/9 (44%) of them had disease progression.13-CRA treatment was well-tolerated. All but one patient complained of at least one side effect the most prevalent being lip dryness (98%). All side effects were transient and resolved within 2 weeks after 13-CRA cessation.

CONCLUSION

Our results show that in patients with non-functional metastases from NMTC, 13-CRA is able to exert some re-differentiation effect by induction of radioiodine uptake in <20% of patients and increase of Tg serum level in about 30% of them. Nevertheless, this does not transfer into clinical benefit as it neither induces measurable tumor response nor prevents disease progression.