Type 3 deiodinase: role in cancer growth, stemness, and metabolism

The key roles of thyroid hormone in mitochondrial regulation, at interface of human health and disease

Mitochondria are highly plastic and dynamic organelles long known as the powerhouse of cellular bioenergetics, but also endowed with a critical role in stress responses and homeostasis maintenance, supporting and integrating activities across multifaced cellular processes. As a such, mitochondria dysfunctions are leading causes of a wide range of diseases and pathologies. Thyroid hormones (THs) are endocrine regulators of cellular metabolism, regulating intracellular nutrients fueling of sugars, amino acids and fatty acids. For instance, THs regulate the balance between the anabolism and catabolism of all the macro-molecules, influencing energy homeostasis during different nutritional conditions. Noteworthy, not only most of the TH-dependent metabolic modulations act via the mitochondria, but also THs have been proved to regulate the mitochondrial biosynthesis, dynamics and function. The significance of such an interplay is different in the context of specific tissues and strongly impacts on cellular homeostasis. Thus, a comprehensive understanding of THs-dependent mitochondrial functions and dynamics is required to develop more precise strategies for targeting mitochondrial function. Herein, we describe the mechanisms of TH-dependent metabolic regulation with a focus on mitochondrial action, in different tissue contexts, thus providing new insights for targeted modulation of mitochondrial dynamics.

Effects of N-acetylcysteine on the expressions of UCP1 and factors related to thyroid function in visceral adipose tissue of obese adults: a randomized, double-blind clinical trial

BACKGROUND

Evidences have shown that obesity is influenced by various factors, including various hormones such as thyroid hormones and the body's metabolism rate. It seems that practical solutions such as weight loss diets and common drugs can affect these potential disorders. In this study, we investigate one of these common drugs, N-Acetylcysteine (NAC), on expressions of UCP1 and factors related to thyroid function in adults with obesity.

METHODS AND ANALYSIS

The current investigation was carried out as a randomized clinical trial (RCT) including 43 adults with obesity who were potential candidates for bariatric surgery. These individuals were randomly divided into two groups: 600 mg of NAC (n = 22) or placebo (n = 21) for a duration of 8 weeks. Visceral adipose tissue was utilized in the context of bariatric surgery to investigate the gene expression of UCP1 and thyroid function. Polymerase chain reaction (PCR) was performed in duplicate for UCP1, DIO2, DIO3, THRα and β, and 18s RNA (as an internal control) using the provided instructions to investigate the expression of the respective genes.

RESULTS

Our findings revealed that after 8 weeks compared to placebo, NAC caused a significant decrease in the expression of the DIO3 gene as one of the genes related to thyroid function and metabolism. However, regarding other related genes, no statistically significant was found (despite the increase in UCP1, DIO2, and THRα expression and decrease in THRβ expression). In addition, after adjustment of possible confounders, no significant effect was observed on anthropometric factors and serum levels of thyroid hormones.

CONCLUSION

The results of this study indicate that, following an 8-week period, NAC effectively decreases the expression of the DIO3 gene in the visceral fat tissue, in comparison to the placebo.

Different Effects of Obesity and Fasting on the Expression of Type 3 Deiodinase and Thyroid Hormone Receptors in the Liver and Visceral Adipose Tissue of C57BL/6 Male Mice

Introduction

Energy status can alter thyroid hormone signalling in different tissues. Little is known about the effect of fasting on the local thyroid hormone metabolism under high-fat diet (HFD)-induced obesity. We aimed to investigate the fasting effect on deiodinase type 3 (DIO3) and thyroid hormone receptors (TRs) expression in liver and visceral adipose tissue (VAT) of HFD-induced obese mice.

Methods

The 30 male C57BL/6 mice were divided into three groups (n = 10/group): control (CON) group, obese (OB) group, and fasted obese (OBF) group.

Materials

In a 14-week study, the expression levels of DIO3 and TRs in the liver and VAT of mice were measured by real-time polymerase chain reaction. Gene expression results were shown as fold changes defined by 2-ΔΔct. Comparison between groups was performed by using one-way-ANOVA or Kruskal-Wallis ANOVA test.

Results

In the liver, there was a significantly lower expression of DIO3 and higher expression of TRs in obese fasted mice compared to obese mice. Compared to the lean mice, OBF mice had significantly lower expression of DIO3 and higher expression of TRβ. In the VAT, mRNA expression of DIO3 was significantly increased in OBF and OB groups compared to the CON group. There were no significant differences in the mRNA expression of TRs between groups.

Conclusion

Our findings suggest that fasting may be more effective in improving thyroid hormone metabolism in the liver rather than the VAT of obese mice.

Identification of pathogenic germline variants in a large Chinese lung cancer cohort by clinical sequencing

Genetic factors play significant roles in the tumorigenicity of lung cancer; however, there is lack of systematic and large-scale characterization of pathogenic germline variants for lung cancer. In this study, germline variants in 146 preselected cancer-susceptibility genes were detected in 17 904 Chinese lung cancer patients by clinical next-generation sequencing. Among 17 904 patients, 1738 patients (9.7%) carried 1840 pathogenic/likely pathogenic (P/LP) variants from 87 cancer-susceptibility genes. SBDS (SBDS ribosome maturation factor) (1.37%), TSHR (thyroid stimulating hormone receptor) (1.20%), BLM (BLM RecQ like helicase) (0.62%), BRCA2 (BRCA2 DNA repair associated) (0.62%), and ATM (ATM serine/threonine kinase) (0.45%) were the top five genes with the highest overall prevalence. The top mutated pathways were all involved in DNA damage repair (DDR). Case-control analysis showed SBDS c.184A>T(p.K62*), TSHR c.1574T>C(p.F525S), BRIP1 (BRCA1 interacting helicase 1) c.1018C>T(p.L340F), and MUTYH (mutY DNA glycosylase) c.55C>T(p.R19*) were significantly associated with increased lung cancer risk (q value < 0.05). P/LP variants in certain genes were associated with early onset of lung cancer. Our study indicates that Chinese lung cancer patients have a higher prevalence of P/LP variants than previously reported. P/LP variants are distributed in multiple pathways and dominated by DNA damage repair-associated pathways. The association between identified P/LP variants and lung cancer risk requires further studies for verification.

Insights on the Association between Thyroid Diseases and Colorectal Cancer

Benign and malignant thyroid diseases (TDs) have been associated with the occurrence of extrathyroidal malignancies (EMs), including colorectal cancers (CRCs). Such associations have generated a major interest, as their characterization may provide useful clues regarding diseases’ etiology and/or progression, with the possible identification of shared congenital and environmental elements. On the other hand, elucidation of the underlying molecular mechanism(s) could lead to an improved and tailored clinical management of these patients and stimulate an increased surveillance of TD patients at higher threat of developing EMs. Here, we will examine the epidemiological, clinical, and molecular findings connecting TD and CRC, with the aim to identify possible molecular mechanism(s) responsible for such diseases’ relationship.

Selenium, selenoproteins and cancer of the thyroid

Selenium is an essential mineral element with important biological functions for the whole body through incorporation into selenoproteins. This element is highly concentrated in the thyroid gland. Selenoproteins provide antioxidant protection for this tissue against the oxidative stress caused by free radicals and contribute, via iodothyronine deiodinases, to the metabolism of thyroid hormones. It is known that oxidative stress plays a major role in carcinogenesis and that in recent decades there has been an increase in the incidence of thyroid cancer. The anti-carcinogenic action of selenium, although not fully understood, is mainly attributable to selenoproteins antioxidant properties, and to the ability to modulate cell proliferation (cell cycle and apoptosis), energy metabolism, and cellular immune response, significantly altered during tumorigenesis. Researchers have suggested that different forms of selenium supplementation may be beneficial in the prevention and treatment of thyroid cancer; however, the studies have several methodological limitations. This review is a summary of the current knowledge on how selenium and selenoproteins related to thyroid cancer.

Alterations of DNA methylation and expression of genes related to thyroid hormone metabolism in colon epithelium of obese patients

Background

Colorectal cancer is common among obese individuals. The purpose of the current study was to determine changes in DNA methylation status and mRNA expression of thyroid hormone receptor beta (THRB), as a tumor suppressor, and thyroid hormone inactivating enzyme, type 3 deiodinase (DIO3) genes, in human epithelial colon tissues of healthy obese individuals.

Methods

Colon biopsies were analyzed by methylation sensitive-high resolution melting (MS-HRM) to investigate promoter methylation of DIO3 and THRB, and by quantitative real-time polymerase chain reaction to assay expression of DIO3 and THRB mRNA on eighteen obese and twenty-one normal-weight healthy men.

Results

There was no significant difference in mean methylation levels at the THRB promoter region between the two groups. Nevertheless, obesity decreased THRB expression levels, significantly (P < 0.05; fold change: 0.19). Furthermore, obesity attenuated DNA methylation (P < 0.001) and enhanced mRNA expression of DIO3 (P < 0.05; fold change: 3).

Conclusions

Our findings suggest that obesity may alter expression of THRB and DIO3 genes through epigenetic mechanism. Alterations of THRB and DIO3 expressions may predispose colon epithelium of obese patients to neoplastic transformation.

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.

Selective thyroid hormone receptor beta agonist, GC-1, is capable to reduce growth of colorectal tumor in syngeneic mouse models

OBJECTIVE

The effect of thyroid hormone (TH) on cancers was proposed more than 100 years ago; however, conclusions are conflicting. THs are precisely regulated at tissue and cellular levels. It seems that this regulation is altered in cancers. Thyroid hormone receptor beta (TRβ) has anti-proliferative and tumor-suppressive effects in many cancer cells. Therefore, we decided to investigate thyroid hormone receptor beta (THRB) expression and activation by the selective agonist, GC-1, on tumor growth in a syngeneic mouse model of colorectal cancer (CRC) and colon cell lines.

METHODS

In vitro cell viability assay using MTT analysis, cell cycle analysis by PI staining, and FACS analysis were performed. In vivo tumor growth measurements were carried out by caliper and [¹⁸F] Fluoro-2-deoxy-2-D-glucose (FDG) - PET imaging. Gene expressions were determined using quantitative-PCR.

RESULTS

Some concentrations of GC-1 had a marked negative effect on the cell viability of colorectal cell lines. Cell cycle analysis showed that the anti-proliferative effect of GC-1 may not result from cell cycle arrest or apoptosis. Tumor growth analysis in mice harboring colorectal tumor showed that GC-1 treatment for 8 d profoundly inhibited tumor growth and ¹⁸FDG uptake. THRB expression was decreased in mice tumor; however, it was upregulated following GC-1 administration.

CONCLUSIONS

Our results showed that specific activation of TRβ by GC-1 had negative effect on tumor growth and restored its gene expression in tumors of CRC mice model.

Colorectal cancer causes alteration of thyroid hormone profile in newly diagnosed patients

OBJECTIVES

Subcellular alteration of thyroid hormones (THs) signaling is proposed in many types of cancers. Some studies show deiodinase type 3, as an oncofetal protein, re-expresses in some cancer types. Therefore, we aimed to investigate the product of this enzyme, reverse triiodothyronine (rT3) in serum of newly diagnosed colorectal cancer (CRC) patients.

METHODS

In this cross-sectional study, blood from 38 laboratory-confirmed cases was taken, and serum levels of rT3, total T3 (triiodothyronine), total T4 (thyroxine), free T3, free T4, and thyroid-stimulating hormone (TSH) were detected by using an enzyme-linked immunosorbent assay.

RESULTS

The results illustrated that rT3 and free T3 levels increased in patients with early stages of colorectal cancer, despite normal levels of total T3, total T4, free T4, and TSH.

CONCLUSION

The elevation of rT3 in CRC patients can probably be due to the re-expression of deiodinase type 3 in CRC. Further research is needed to study the role of intracellular THs modulation in CRC and its impact on CRC treatment.

Thyroid Hormones-An Underestimated Player in Dilated Cardiomyopathy?

Dilated cardiomyopathy (DCM) is the most prevalent cardiomyopathy, typified by left ventricular dilation and systolic dysfunction. Many patients with DCM have altered thyroid status, especially lower levels of free triiodothyronine (T3) and elevated levels of thyroid-stimulating hormone. Moreover, growing evidence indicates that even subtle changes in thyroid status (especially low T3) are linked with a worse long-term prognosis and a higher risk of mortality. Notably, recent discoveries have shown that not only local myocardial thyroid hormones (THs) bioavailability could be diminished due to impaired expression of the activating deiodinase, but virtually all genes involved in TH biosynthesis are also expressed in the myocardium of DCM patients. Importantly, some studies have suggested beneficial effects of TH therapy in patients suffering from DCM. Our aim was to discuss new insights into the association between TH status and prognosis in DCM, abnormal expression of genes involved in the myocardial synthesis of TH in DCM, and the potential for TH use in the future treatment of DCM.

Involvement of Thyroid Hormones in Brain Development and Cancer

The development and maturation of the mammalian brain are regulated by thyroid hormones (THs). Both hypothyroidism and hyperthyroidism cause serious anomalies in the organization and function of the nervous system. Most importantly, brain development is sensitive to TH supply well before the onset of the fetal thyroid function, and thus depends on the trans-placental transfer of maternal THs during pregnancy. Although the mechanism of action of THs mainly involves direct regulation of gene expression (genomic effects), mediated by nuclear receptors (THRs), it is now clear that THs can elicit cell responses also by binding to plasma membrane sites (non-genomic effects). Genomic and non-genomic effects of THs cooperate in modeling chromatin organization and function, thus controlling proliferation, maturation, and metabolism of the nervous system. However, the complex interplay of THs with their targets has also been suggested to impact cancer proliferation as well as metastatic processes. Herein, after discussing the general mechanisms of action of THs and their physiological effects on the nervous system, we will summarize a collection of data showing that thyroid hormone levels might influence cancer proliferation and invasion.

DIO3, the thyroid hormone inactivating enzyme, promotes tumorigenesis and metabolic reprogramming in high grade serous ovarian cancer

High grade serous ovarian cancer (HGSOC) is the most lethal gynecologic malignancy with a need for better understanding the disease pathogenesis. The biologically active thyroid hormone, T3, is considered a tumor suppressor by promoting cell differentiation and mitochondrial respiration. Tumors evolved a strategy to avoid these anticancer actions by expressing the T3 catabolizing enzyme, Deiodinase type 3 (DIO3). This stimulates cancer proliferation and aerobic glycolysis (Warburg effect). We identified DIO3 expression in HGSOC cell lines, tumor tissues from mice and human patients, fallopian tube (FT) premalignant lesion and secretory cells of normal FT, considered the disease site-of-origin. Stable DIO3 knockdown (DIO3-KD) in HGSOC cells led to increased T3 bioavailability and demonstrated induced apoptosis and attenuated proliferation, migration, colony formation, oncogenic signaling, Warburg effect and tumor growth in mice. Proteomics analysis further indicated alterations in an array of cancer-relevant proteins, the majority of which are involved in tumor suppression and metabolism. Collectively this study establishes the functional role of DIO3 in facilitating tumorigenesis and metabolic reprogramming, and proposes this enzyme as a promising target for inhibition in HGSOC.

Decreased expression of the thyroid hormone-inactivating enzyme type 3 deiodinase is associated with lower survival rates in breast cancer

Thyroid hormones (THs) are critical regulators of cellular processes, while changes in their levels impact all the hallmarks of cancer. Disturbed expression of type 3 deiodinase (DIO3), the main TH-inactivating enzyme, occurs in several human neoplasms and has been associated with adverse outcomes. Here, we investigated the patterns of DIO3 expression and its prognostic significance in breast cancer. DIO3 expression was evaluated by immunohistochemistry in a primary cohort of patients with breast cancer and validated in a second cohort using RNA sequencing data from the TCGA database. DNA methylation data were obtained from the same database. DIO3 expression was present in normal and tumoral breast tissue. Low levels of DIO3 expression were associated with increased mortality in the primary cohort. Accordingly, low DIO3 mRNA levels were associated with an increased risk of death in a multivariate model in the validation cohort. DNA methylation analysis revealed that the DIO3 gene promoter is hypermethylated in tumors when compared to normal tissue. In conclusion, DIO3 is expressed in normal and tumoral breast tissue, while decreased expression relates to poor overall survival in breast cancer patients. Finally, loss of DIO3 expression is associated with hypermethylation of the gene promoter and might have therapeutic implications.

Thyroid hormone regulation of neural stem cell fate: From development to ageing

In the vertebrate brain, neural stem cells (NSCs) generate both neuronal and glial cells throughout life. However, their neuro‐ and gliogenic capacity changes as a function of the developmental context. Despite the growing body of evidence on the variety of intrinsic and extrinsic factors regulating NSC physiology, their precise cellular and molecular actions are not fully determined. Our review focuses on thyroid hormone (TH), a vital component for both development and adult brain function that regulates NSC biology at all stages. First, we review comparative data to analyse how TH modulates neuro‐ and gliogenesis during vertebrate brain development. Second, as the mammalian brain is the most studied, we highlight the molecular mechanisms underlying TH action in this context. Lastly, we explore how the interplay between TH signalling and cell metabolism governs both neurodevelopmental and adult neurogenesis. We conclude that, together, TH and cellular metabolism regulate optimal brain formation, maturation and function from early foetal life to adult in vertebrate species.

Structure and Mechanism of Iodothyronine Deiodinases - What We Know, What We Don't Know, and What Would Be Nice to Know

Deiodinases catalyze the specific removal of iodine atoms from one of the two iodinated phenyl rings in iodothyronines. They thereby fine-regulate local thyroid hormone concentrations in organs or cells. The chemical reaction is unique in the sense that in metazoans the reductive elimination of iodide depends on the rare amino acid selenocysteine in the enzymes' active centers. While there is no prokaryotic homologue of such deiodinases, the solution of the crystal structure of a catalytic domain of mouse deiodinase 3 has revealed that the ancient peroxiredoxin structure has been repurposed, and improved using selenocysteine, as a deiodinase during metazoan evolution. Likewise, many biochemical findings obtained over decades can now be interpreted in light of the molecular structure. Despite this leap in our understanding of deiodinase structure, there are still several open questions that need to be addressed in order to fully understand substrate binding, catalytic mechanism, and regulation of deiodinases. We surmise that these issues as well as differences between the three highly homologous isoenzymes must be understood in order to develop modulators of deiodinases that could be valuable in clinical use.

Liver dysfunction induced by Levothyroxine Sodium Tablets (Euthyrox®) in a hypothyroid patient with Hashimoto's thyroiditis: case report and literature review

A 49-year-old woman with hypothyroidism developed liver dysfunction after increasing dose of levothyroxine (L-T4) (Euthyrox^®) from 25 μg to 50 μg. Viral hepatitis, autoimmune hepatitis and non-alcoholic steatohepatitis (NASH) were ruled out with examinations. She had no concurrent medication and had no history of infectious, chronic or any other autoimmune diseases. After cessation of Levothyroxine Sodium Tablets (Euthyrox^®), liver enzymes gradually returned to normal. She was diagnosed levothyroxine-induced liver injury, based on criteria proposed in "Diagnosis and treatment guideline on drug-induced liver injury" issued by the Chinese Medical Association (2015). As an alternative 25 μg qod of Levothyroxine Sodium Tablets (Letrox^®) was tried and increased gradually up to 75 μg daily. Since then liver enzymes have remained within normal range. The main difference of additive for both tablets is whether it contains lactose or not: Euthyrox^® contains lactose which caused no liver injury, thus excluding the possibility that an additive of Euthyrox^® contributed to liver injury. The relatively quicker and larger replacement with synthetic T4 for hypothyroidism inducing transient thyrotoxicosis was suspected, although thyroid function was normal. Immune-mediated drug-induced liver injury (DILI) was also not excluded. This is a rare case of drug-induced liver injury due to levothyroxine tablets. It reminded us that when replacement with synthetic T4 for hypothyroidism is done, smaller-dose initiation and slower-speed increase may be useful for treatment of cases similar to genetically susceptible individuals.

The Colorful Diversity of Thyroid Hormone Metabolites

Since the discovery of L-thyroxine, the main secretory product of the thyroid gland, and its major metabolite T3, which exerts the majority of thyroid hormone action via ligand-dependent modulation of the function of T3 receptors in nuclei, mitochondria, and other subcellular compartments, various other T4-derived endogenous metabolites have been identified in blood and tissues of humans, animals, and early protochordates. This review addresses major historical milestones and experimental findings resulting in the discovery of the key enzymes of thyroid hormone metabolism, the three selenoprotein deiodinases, as well as the decarboxylases and amine oxidases involved in formation and degradation of recently identified endogenous thyroid hormone metabolites, i.e. 3-iodothyronamine and 3-thyroacetic acid. The concerted action of deiodinases 2 and 3 in regulation of local T3 availability is discussed. Special attention is given to the role of the thyromimetic "hot" metabolite 3,5-T2 and the "cool" 3-iodothyronamine, especially after administration of pharmacological doses of these endogenous thyroid hormone metabolites in various animal experimental models. In addition, available information on the biological roles of the two major acetic acid derivatives of thyroid hormones, i.e. Tetrac and Triac, as well as sulfated metabolites of thyroid hormones is reviewed. This review addresses the consequences of the existence of this broad spectrum of endogenous thyroid hormone metabolites, the "thyronome," beyond the classical thyroid hormone profile comprising T4, T3, and rT3 for appropriate analytical coverage and clinical diagnostics using mass spectrometry versus immunoassays for determination of total and free concentrations of thyroid hormone metabolites in blood and tissues.

Local hyperthyroidism promotes pancreatic acinar cell proliferation during acute pancreatitis

Proliferation of pancreatic acinar cells is a critical process in the pathophysiology of pancreatic diseases, because limited or defective proliferation is associated with organ dysfunction and patient morbidity. In this context, elucidating the signalling pathways that trigger and sustain acinar proliferation is pivotal to develop therapeutic interventions promoting the regenerative process of the organ. In this study we used genetic and pharmacological approaches to manipulate both local and systemic levels of thyroid hormones to elucidate their role in acinar proliferation following caerulein-mediated acute pancreatitis in mice. In addition, molecular mechanisms mediating the effects of thyroid hormones were identified by genetic and pharmacological inactivation of selected signalling pathways.In this study we demonstrated that levels of the thyroid hormone 3,3',5-triiodo-l-thyronine (T3) transiently increased in the pancreas during acute pancreatitis. Moreover, by using genetic and pharmacological approaches to manipulate both local and systemic levels of thyroid hormones, we showed that T3 was required to promote proliferation of pancreatic acinar cells, without affecting the extent of tissue damage or inflammatory infiltration.Finally, upon genetic and pharmacological inactivation of selected signalling pathways, we demonstrated that T3 exerted its mitogenic effect on acinar cells via a tightly controlled action on different molecular effectors, including histone deacetylase, AKT, and TGFβ signalling.In conclusion, our data suggest that local availability of T3 in the pancreas is required to promote acinar cell proliferation and provide the rationale to exploit thyroid hormone signalling to enhance pancreatic regeneration. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Developing a Prognostic Gene Panel of Epithelial Ovarian Cancer Patients by a Machine Learning Model

Epithelial ovarian cancer patients usually relapse after primary management. We utilized the support vector machine algorithm to develop a model for the chemo-response using the Cancer Cell Line Encyclopedia (CCLE) and validated the model in The Cancer Genome Atlas (TCGA) and the GSE9891 dataset. Finally, we evaluated the feasibility of the model using ovarian cancer patients from our institute. The 10-gene predictive model demonstrated that the high response group had a longer recurrence-free survival (RFS) (log-rank test, p = 0.015 for TCGA, p = 0.013 for GSE9891 and p = 0.039 for NTUH) and overall survival (OS) (log-rank test, p = 0.002 for TCGA and p = 0.016 for NTUH). In a multivariate Cox hazard regression model, the predictive model (HR: 0.644, 95% CI: 0.436⁻0.952, p = 0.027) and residual tumor size < 1 cm (HR: 0.312, 95% CI: 0.170⁻0.573, p < 0.001) were significant factors for recurrence. The predictive model (HR: 0.511, 95% CI: 0.334⁻0.783, p = 0.002) and residual tumor size < 1 cm (HR: 0.252, 95% CI: 0.128⁻0.496, p < 0.001) were still significant factors for death. In conclusion, the patients of high response group stratified by the model had good response and favourable prognosis, whereas for the patients of medium to low response groups, introduction of other drugs or clinical trials might be beneficial.

The Role of Thyroid Hormones in Hepatocyte Proliferation and Liver Cancer

Thyroid hormones T3 and T4 (thyroxine) control a wide variety of effects related to development, differentiation, growth and metabolism, through their interaction with nuclear receptors. But thyroid hormones also produce non-genomic effects that typically start at the plasma membrane and are mediated mainly by integrin αvβ3, although other receptors such as TRα and TRβ are also able to elicit non-genomic responses. In the liver, the effects of thyroid hormones appear to be particularly important. The liver is able to regenerate, but it is subject to pathologies that may lead to cancer, such as fibrosis, cirrhosis, and non-alcoholic fatty liver disease. In addition, cancer cells undergo a reprogramming of their metabolism, resulting in drastic changes such as aerobic glycolysis instead of oxidative phosphorylation. As a consequence, the pyruvate kinase isoform M2, the rate-limiting enzyme of glycolysis, is dysregulated, and this is considered an important factor in tumorigenesis. Redox equilibrium is also important, in fact cancer cells give rise to the production of more reactive oxygen species (ROS) than normal cells. This increase may favor the survival and propagation of cancer cells. We evaluate the possible mechanisms involving the plasma membrane receptor integrin αvβ3 that may lead to cancer progression. Studying diseases that affect the liver and their experimental models may help to unravel the cellular pathways mediated by integrin αvβ3 that can lead to liver cancer. Inhibitors of integrin αvβ3 might represent a future therapeutic tool against liver cancer. We also include information on the possible role of exosomes in liver cancer, as well as on recent strategies such as organoids and spheroids, which may provide a new tool for research, drug discovery, and personalized medicine.

The Emerging Role of Insulin Receptor Isoforms in Thyroid Cancer: Clinical Implications and New Perspectives

Thyroid cancer (TC) is the most common endocrine tumor. Although the majority of TCs show good prognoses, a minor proportion are aggressive and refractory to conventional therapies. So far, the molecular mechanisms underlying TC pathogenesis are incompletely understood. Evidence suggests that TC cells and their precursors are responsive to insulin and insulin-like growth factors (IGFs), and often overexpress receptors for insulin (IR) and IGF-1 (IGF-1R). IR exists in two isoforms, namely IR-A and IR-B. The first binds insulin and IGF-2, unlike IR-B, which only binds insulin. IR-A is preferentially expressed in prenatal life and contributes to development through IGF-2 action. Aggressive TC overexpresses IR-A, IGF-2, and IGF-1R. The over-activation of IR-A/IGF-2 loop in TC is associated with stem-like features and refractoriness to some targeted therapies. Importantly, both IR isoforms crosstalk with IGF-1R, giving rise to the formation of hybrids receptors (HR-A or HR-B). Other interactions have been demonstrated with other molecules such as the non-integrin collagen receptor, discoidin domain receptor 1 (DDR1), and the receptor for the hepatocyte growth factor (HGF), Met. These functional networks provide mechanisms for IR signaling diversification, which may also exert a role in TC stem cell biology, thereby contributing to TC initiation and progression. This review focuses on the molecular mechanisms by which deregulated IR isoforms and their crosstalk with other molecules and signaling pathways in TC cells and their precursors may contribute to thyroid carcinogenesis, progression, and resistance to conventional treatments. We also highlight how targeting these alterations starting from TC progenitors cells may represent new therapeutic strategies to improve the clinical management of advanced TCs.

Plasma 3,3',5-Triiodo-L-thyronine [T3] level mirrors changes in tumor markers in two cases of metastatic cancer of the breast and pancreas treated with exogenous L-T3

Preclinical studies have attributed 3,3’,5-triiodo-L-thyronine (T3) a direct negative effect on tumor progression, as well as chemosensitizing, differentiating and immunomodulatory properties. On the other hand, L-thyroxine (T4), via a thyroid hormone receptor on plasma membrane integrin αvβ3, promotes solid tumor growth and neoangiogenesis, therefore lowering endogenous T4 reduces tumor growth rate. We present the case of two patients with metastatic triple negative breast cancer and metastatic pancreatic cancer respectively, who benefit of the sole treatment with antithyroid drugs and exogenous administration of T3 (liothyronine). In these cases tumor growth was accompanied by T3 depletion in plasma, which may represent a novel marker for progression.

Selenoproteins in human body: focus on thyroid pathophysiology

Selenium (Se) has a multilevel, complex and dynamic effect on the human body as a major component of selenocysteine, incorporated into selenoproteins, which include the selenocysteine-containing enzymes iodothyronine deiodinases. At the thyroid level, these proteins play an essential role in antioxidant protection and hormone metabolism. This is a narrative review based on PubMed/Medline database research regarding thyroid physiology and conditions with Se and Se-protein interferences. In humans, Se-dependent enzyme functions are best expressed through optimal Se intake, although there is gap in our knowledge concerning the precise mechanisms underlying the interrelation. There is a good level of evidence linking low serum Se to autoimmune thyroid diseases and, to a lesser extent, differentiated thyroid cancer. However, when it comes to routine supplementation, the results are heterogeneous, except in the case of mild Graves' orbitopathy. Autoimmune hypothyroidism is associated with a state of higher oxidative stress, but not all studies found an improvement of thyroid function after Se was introduced as antioxidant support. Meanwhile, no routine supplementation is recommended. Low Se intake is correlated with an increased risk of developing antithyroid antibodies, its supplementation decreasing their titres; there is also a potential reduction in levothyroxine replacement dose required for hypothyroidism and/or the possibility that it prevents progression of subclinical hypothyroidism, although not all studies agree. In thyroid-associated orbitopathy, euthyroidism is more rapidly achieved if the micronutrient is added to traditional drugs, while controls appear to benefit from the microelement only if they are deficient; thus, a basal assay of Se appears advisable to better select patients who need substitution. Clearly, further Se status biomarkers are required. Future introduction of individual supplementation algorithms based on baseline micronutrient levels, underlying or at-risk clinical conditions, and perhaps selenoprotein gene polymorphisms is envisaged.

Nonthyroidal Illness Syndrome and Thyroid Hormone Actions at Integrin αvβ3

CONTEXT

The nonthyroidal illness syndrome (NTIS) is a constellation of changes in circulating thyroid hormone levels that occur in euthyroid patients with acute or chronic systemic diseases. The changes that occur include a reduction in serum T3, an increase in serum rT3, and variable changes in circulating T4 levels. No consensus exists regarding therapeutic intervention for NTIS.

METHODS

We briefly review the published literature on the physiological actions of T4 and of rT3-hormones that until recently have been seen to have little or no bioactivity-and analyze the apparent significance of changes in circulating T4 and T3 encountered in the setting of NTIS in patients with cancer. In the case of T4, these actions may be initiated at a cancer or endothelial cell plasma membrane receptor on integrin αvβ3 or at the cytoskeleton.

RESULTS

This review examines possible therapeutic intervention in NTIS in patients with cancer in terms of T4 reduction and T3 support. Evidence also exists that rT3 may support cancer.

CONCLUSIONS

Prospective study is proposed of pharmacological reduction of normal or elevated T4 in cancer-associated NTIS. We also support investigation of normally circulating levels of T3 in such patients.

Association between genetic polymorphism and levothyroxine bioavailability in hypothyroid patients

Thyroid hormones play a vital role in the human body for growth and differentiation, regulation of energy metabolism, and physiological function. Hypothyroidism is a common endocrine disorder, which generally results from diminished normal circulating concentrations of serum thyroxine (fT4) and triiodothyronine (fT3). The primary choice in hypothyroidism treatment is oral administration of levothyroxine (L-T4), a synthetic T4 hormone, as approximately 100-125 μg/day. Generally, dose adjustment is made by trial and error approach. However, there are several factors which might influence bioavailability of L-T4 treatment. Genetic background could be an important factor in hypothyroid patients as well as age, gender, concurrent medications and patient compliance. The concentration of thyroid hormones in tissue is regulated by both deiodinases enzyme and thyroid hormone transporters. In the present study, it was aimed to evaluate the effects of genetic differences in the proteins and enzymes (DIO1, DIO2, TSHR, THR and UGT) which are efficient in thyroid hormone metabolism and bioavailability of L-T4 in Turkish population. According to our findings, rs225014 and rs225015 variants in DIO2, which catalyses the conversion of thyroxine (pro-hormone) to the active thyroid hormone, were associated with TSH levels. It should be given lower dose to the patients with rs225014 TT and rs225015 GG genotypes in order to provide proper treatment with higher effectivity and lower toxicity.

Metabolic Alterations of Thyroid Cancer as Potential Therapeutic Targets

Thyroid cancer (TC) is the most frequent endocrine tumor with a growing incidence worldwide. Besides the improvement of diagnosis, TC increasing incidence is probably due to environmental factors and lifestyle modifications. The actual diagnostic criteria for TC classification are based on fine needle biopsy (FNAB) and histological examination following thyroidectomy. Since in some cases it is not possible to make a proper diagnosis, classical approach needs to be supported by additional biomarkers. Recently, new emphasis has been given to the altered cellular metabolism of proliferating cancer cells which require high amount of glucose for energy production and macromolecules biosynthesis. Also TC displays alteration of energy metabolism orchestrated by oncogenes activation and tumor suppressors inactivation leading to abnormal proliferation. Furthermore, TC shows significant metabolic heterogeneity within the tumor microenvironment and metabolic coupling between cancer and stromal cells. In this review we focus on the current knowledge of metabolic alterations of TC and speculate that targeting TC metabolism may improve current therapeutic protocols for poorly differentiated TC. Future studies will further deepen the actual understandings of the metabolic phenotype of TC cells and will give the chance to provide novel prognostic biomarkers and therapeutic targets in tumors with a more aggressive behavior.

Role of thyroid hormones in the neoplastic process: an overview

Thyroid hormones (TH) are critical regulators of several physiological processes, which include development, differentiation and growth in virtually all tissues. In past decades, several studies have shown that changes in TH levels caused by thyroid dysfunction, disruption of deiodinases and/or thyroid hormone receptor (TR) expression in tumor cells, influence cell proliferation, differentiation, survival and invasion in a variety of neoplasms in a cell type-specific manner. The function of THs and TRs in neoplastic cell proliferation involves complex mechanisms that seem to be cell specific, exerting effects via genomic and nongenomic pathways, repressing or stimulating transcription factors, influencing angiogenesis and promoting invasiveness. Taken together, these observations indicate an important role of TH status in the pathogenesis and/or development of human neoplasia. Here, we aim to present an updated and comprehensive picture of the accumulated knowledge and the current understanding of the potential role of TH status on the different hallmarks of the neoplastic process.

Thyroid Hormone Regulation and Insulin Resistance: Insights From Animals Naturally Adapted to Fasting

The contribution of thyroidal status in insulin signaling and glucose homeostasis has been implicated as a potential pathophysiological factor in humans, but the specific mechanisms remain largely elusive. Fasting induces changes in both thyroid hormone secretion and insulin signaling. Here, we explore how mammals that undergo natural, prolonged bouts of fasting provide unique insight into evolved physiological adaptations that allow them to tolerate such conditions despite intermittent states of reversible insulin resistance. Such insights from nature may provide clues to better understand the basis of thyroidal involvement in insulin dysregulation in humans.

Induction of type 1 iodothyronine deiodinase expression inhibits proliferation and migration of renal cancer cells

Type 1 iodothyronine deiodinase (DIO1) regulates peripheral metabolism of thyroid hormones that control cellular proliferation, differentiation and metabolism. The significance of DIO1 in cancer is unknown. In this study we hypothesized that diminished expression of DIO1, observed in renal cancer, contributes to the carcinogenic process in the kidney. Here, we demonstrate that ectopic expression of DIO1 in renal cancer cells changes the expression of genes controlling cell cycle, including cyclin E1 and E2F5, and results in inhibition of proliferation. The expression of genes encoding collagens (COL1A1, COL4A2, COL5A1), integrins (ITGA4, ITGA5, ITGB3) and transforming growth factor-β-induced (TGFBI) is significantly altered in renal cancer cells with induced expression of DIO1. Finally, we show that overexpression of DIO1 inhibits migration of renal cancer cells. In conclusion, we demonstrate for the first time that loss of DIO1 contributes to renal carcinogenesis and that its induced expression protects cells against cancerous proliferation and migration.

Energy metabolism in skin cancers: A therapeutic perspective

Skin cancers are the most common cancers worldwide. The incidence of common skin cancers, including basal cell carcinomas (BCCs), squamous cell carcinomas (SCCs) and melanomas, continues to rise by 5 to 7% per year, mainly due to ultraviolet (UV) exposure and partly because of aging. This suggests an urgent necessity to improve the level of prevention and protection for skin cancers as well as developing new prognostic and diagnostic markers of skin cancers. Moreover, despite innovative therapies especially in the fields of melanoma and carcinomas, new therapeutic options are needed to bypass resistance to targeted therapies or treatment's side effects. Since reprogramming of cellular metabolism is now considered as a hallmark of cancer, some of the recent findings on the role of energy metabolism in skin cancer initiation and progression as well as its effect on the response to targeted therapies are discussed in this review. This article is part of a Special Issue entitled Mitochondria in cancer, edited by Giuseppe Gasparre, Rodrigue Rossignol and Pierre Sonveaux.

PPAR-γ Agonists As Antineoplastic Agents in Cancers with Dysregulated IGF Axis

It is now widely accepted that insulin resistance and compensatory hyperinsulinemia are associated to increased cancer incidence and mortality. Moreover, cancer development and progression as well as cancer resistance to traditional anticancer therapies are often linked to a deregulation/overactivation of the insulin-like growth factor (IGF) axis, which involves the autocrine/paracrine production of IGFs (IGF-I and IGF-II) and overexpression of their cognate receptors [IGF-I receptor, IGF-insulin receptor (IR), and IR]. Recently, new drugs targeting various IGF axis components have been developed. However, these drugs have several limitations including the occurrence of insulin resistance and compensatory hyperinsulinemia, which, in turn, may affect cancer cell growth and survival. Therefore, new therapeutic approaches are needed. In this regard, the pleiotropic effects of peroxisome proliferator activated receptor (PPAR)-γ agonists may have promising applications in cancer prevention and therapy. Indeed, activation of PPAR-γ by thiazolidinediones (TZDs) or other agonists may inhibit cell growth and proliferation by lowering circulating insulin and affecting key pathways of the Insulin/IGF axis, such as PI3K/mTOR, MAPK, and GSK3-β/Wnt/β-catenin cascades, which regulate cancer cell survival, cell reprogramming, and differentiation. In light of these evidences, TZDs and other PPAR-γ agonists may be exploited as potential preventive and therapeutic agents in tumors addicted to the activation of IGF axis or occurring in hyperinsulinemic patients. Unfortunately, clinical trials using PPAR-γ agonists as antineoplastic agents have reached conflicting results, possibly because they have not selected tumors with overactivated insulin/IGF-I axis or occurring in hyperinsulinemic patients. In conclusion, the use of PPAR-γ agonists in combined therapies of IGF-driven malignancies looks promising but requires future developments.

Insulin Resistance: Any Role in the Changing Epidemiology of Thyroid Cancer?

In the past few decades, the incidence of thyroid cancer (TC), namely of its papillary hystotype (PTC), has shown a steady increase worldwide, which has been attributed at least in part to the increasing diagnosis of early stage tumors. However, some evidence suggests that environmental and lifestyle factors can also play a role. Among the potential risk factors involved in the changing epidemiology of TC, particular attention has been drawn to insulin-resistance and related metabolic disorders, such as obesity, type 2 diabetes, and metabolic syndrome, which have been also rapidly increasing worldwide due to widespread dietary and lifestyle changes. In accordance with this possibility, various epidemiological studies have indeed gathered substantial evidence that insulin resistance-related metabolic disorders might be associated with an increased TC risk either through hyperinsulinemia or by affecting other TC risk factors including iodine deficiency, elevated thyroid stimulating hormone, estrogen-dependent signaling, chronic autoimmune thyroiditis, and others. This review summarizes the current literature evaluating the relationship between metabolic disorders characterized by insulin resistance and the risk for TC as well as the possible underlying mechanisms. The potential implications of such association in TC prevention and therapy are discussed.

Thyroid Function and Cancer Risk: The Rotterdam Study

CONTEXT

In vitro and in vivo experiments have assigned both oncosuppressive and oncogenic properties to thyroid hormones. Population-based studies have found inconclusive results.

OBJECTIVE

We aimed to prospectively assess the relation between thyroid function and incident cancer in a population-based setting.

DESIGN, SETTING, AND PARTICIPANTS

The current study is a prospective population-based cohort study including 10 318 participants for whom baseline measurements of free T₄ (FT₄) and/or TSH were available.

MAIN OUTCOME MEASURES

Cox proportional hazards models were used to assess hazard ratios (HRs) of any solid non-skin cancer, as well as lung, breast, prostate, and gastrointestinal cancer specifically.

RESULTS

Higher FT₄ levels were associated with a higher risk of any solid cancer (HR, 1.42; 95% confidence interval [CI], 1.12-1.79), lung cancer (HR, 2.33; 95% CI, 1.39-3.92) and breast (HR, 1.77; 95% CI, 1.10-2.84) cancer. The risk estimates were similar after exclusion of thyroid-altering medication, but the association lost significance for breast cancer. Compared with the lowest FT₄ tertile, the highest tertile was associated with a 1.13-fold increased risk of any solid, 1.79-fold increased risk of lung, and 1.14-fold increased risk of breast cancer (P for trend <.05 for all). For TSH levels we found no associations with cancer risk. There was no differential effect of sex or age on the association between thyroid function and cancer risk.

CONCLUSIONS

Higher FT₄ levels are significantly associated with an increased risk of any solid, lung, and breast cancer. Further research should elucidate the underlying pathophysiological mechanisms.

Hypothalamus-Pituitary-Thyroid Axis

The hypothalamus-pituitary-thyroid (HPT) axis determines the set point of thyroid hormone (TH) production. Hypothalamic thyrotropin-releasing hormone (TRH) stimulates the synthesis and secretion of pituitary thyrotropin (thyroid-stimulating hormone, TSH), which acts at the thyroid to stimulate all steps of TH biosynthesis and secretion. The THs thyroxine (T4) and triiodothyronine (T3) control the secretion of TRH and TSH by negative feedback to maintain physiological levels of the main hormones of the HPT axis. Reduction of circulating TH levels due to primary thyroid failure results in increased TRH and TSH production, whereas the opposite occurs when circulating THs are in excess. Other neural, humoral, and local factors modulate the HPT axis and, in specific situations, determine alterations in the physiological function of the axis. The roles of THs are vital to nervous system development, linear growth, energetic metabolism, and thermogenesis. THs also regulate the hepatic metabolism of nutrients, fluid balance and the cardiovascular system. In cells, TH actions are mediated mainly by nuclear TH receptors (210), which modify gene expression. T3 is the preferred ligand of THR, whereas T4, the serum concentration of which is 100-fold higher than that of T3, undergoes extra-thyroidal conversion to T3. This conversion is catalyzed by 5'-deiodinases (D1 and D2), which are TH-activating enzymes. T4 can also be inactivated by conversion to reverse T3, which has very low affinity for THR, by 5-deiodinase (D3). The regulation of deiodinases, particularly D2, and TH transporters at the cell membrane control T3 availability, which is fundamental for TH action. © 2016 American Physiological Society. Compr Physiol 6:1387-1428, 2016.

Glucose delays the insulin-induced increase in thyroid hormone-mediated signaling in adipose of prolong-fasted elephant seal pups

Prolonged food deprivation in mammals typically reduces glucose, insulin, and thyroid hormone (TH) concentrations, as well as tissue deiodinase (DI) content and activity, which, collectively, suppress metabolism. However, in elephant seal pups, prolonged fasting does not suppress TH levels; it is associated with upregulation of adipose TH-mediated cellular mechanisms and adipose-specific insulin resistance. The functional relevance of this apparent paradox and the effects of glucose and insulin on TH-mediated signaling in an insulin-resistant tissue are not well defined. To address our hypothesis that insulin increases adipose TH signaling in pups during extended fasting, we assessed the changes in TH-associated genes in response to an insulin infusion in early- and late-fasted pups. In late fasting, insulin increased DI1, DI2, and THrβ-1 mRNA expression by 566%, 44%, and 267% at 60 min postinfusion, respectively, with levels decreasing by 120 min. Additionally, we performed a glucose challenge in late-fasted pups to differentiate between insulin- and glucose-mediated effects on TH signaling. In contrast to the insulin-induced effects, glucose infusion did not increase the expressions of DI1, DI2, and THrβ-1 until 120 min, suggesting that glucose delays the onset of the insulin-induced effects. The data also suggest that fasting duration increases the sensitivity of adipose TH-mediated mechanisms to insulin, some of which may be mediated by increased glucose. These responses appear to be unique among mammals and to have evolved in elephant seals to facilitate their adaptation to tolerate an extreme physiological condition.

New insights into the structure and mechanism of iodothyronine deiodinases

Iodothyronine deiodinases are a family of enzymes that remove specific iodine atoms from one of the two aromatic rings in thyroid hormones (THs). They thereby fine-tune local TH concentrations and cellular TH signaling. Deiodinases catalyze a remarkable biochemical reaction, i.e., the reductive elimination of a halogenide from an aromatic ring. In metazoans, deiodinases depend on the rare amino acid selenocysteine. The recent solution of the first experimental structure of a deiodinase catalytic domain allowed for a reappraisal of the many mechanistic and mutagenesis data that had been accumulated over more than 30 years. Hence, the structure generates new impetus for research directed at understanding catalytic mechanism, substrate specificity, and regulation of deiodinases. This review will focus on structural and mechanistic aspects of iodothyronine deiodinases and briefly compare these enzymes with dehalogenases, which catalyze related reactions. A general mechanism for the selenium-dependent deiodinase reaction will be described, which integrates the mouse deiodinase 3 crystal structure and biochemical studies. We will summarize further, sometimes isoform-specific molecular features of deiodinase catalysis and regulation, and we will then discuss available compounds for modulating deiodinase activity for therapeutic purposes.