Thyroid hormone is a MAPK-dependent growth factor for human myeloma cells acting via αvβ3 integrin

The Effect of Thyrotropin Suppression on Survival Outcomes in Patients with Differentiated Thyroid Cancer: A Systematic Review and Meta-Analysis

Background: Long-term management of intermediate- and high-risk differentiated thyroid cancer (DTC) involves thyrotropin (TSH) suppression with thyroid hormone to prevent potential stimulation of TSH receptors on DTC cells, leading to tumor growth. However, the current guidelines recommending TSH suppression are based on low- to moderate-quality evidence. Methods: We performed a systematic review and meta-analysis of studies evaluating the role of TSH suppression in intermediate- and high-risk DTC patients (≥18 years) treated as per regional guideline-based therapy with a follow-up duration of 5 years (PROSPERO #252396). TSH suppression was defined as "below normal reference range" or, when known, <0.5 mIU/L. Primary outcome measures included (i) composite of progression-free survival (PFS), disease-free survival (DFS), and relapse-free survival (RLFS), and (ii) composite of disease-specific survival (DSS), and overall survival (OS). Secondary outcome included a composite of cardiac or skeletal adverse events. All outcomes and comparisons were represented as TSH suppression versus TSH nonsuppression. Randomized controlled trials, cohort studies, and case-control studies were included for analysis. Pooled hazard ratio (HR) and 95% confidence interval (CI) were calculated using random-effects model. Results: Abstract screening was performed on 6,369 studies. After the exclusion of irrelevant studies and full-text screening, nine studies were selected for the final meta-analysis. Based on seven studies (3,591 patients), the composite outcome of PFS, DFS, and RLFS was not significantly different between TSH suppression and nonsuppression groups (HR: 0.75; 95% CI: 0.48-1.17; I2 = 76%). Similarly, a DSS and OS composite outcome assessment based on four studies (3,616 patients) did not favor TSH suppression (HR: 0.69; 95% CI: 0.31-1.52; I2 = 88%). Even after excluding studies of lower quality, the primary outcomes were not significantly different between the TSH suppression and nonsuppression cohorts. The secondary outcome, obtained from two studies (1,294 patients), was significantly higher in the TSH-suppressed groups (HR: 1.82; 95% CI: 1.30-2.55; I2 = 0%). Significant study heterogeneity was noted for primary outcomes. Conclusion: TSH suppression in intermediate- and high-risk DTC may not improve survival outcomes but may increase the risk of secondary complications. However, the limited evidence and study heterogeneity warrant cautious interpretation of our findings. Registration: PROSPERO #252396.

Thyroid hormone induces restrictive cardiomyopathy in β1-adrenoceptor knockout mice

The purpose of this study was to characterize the role of β1-AR signaling and its cross-talk between cardiac renin-angiotensin system and thyroid-hormone-induced cardiac hypertrophy. T3 was administered at 0.5 mg·kg-1·day-1 for 10 days in β1-KOT3 and WTT3 groups, while control groups received vehicle alone. Echocardiography and myocardial histology was performed; cardiac and serum ANGI/ANGII and ANP and cardiac levels of p-PKA, p-ERK1/2, p-p38-MAPK, p-AKT, p-4EBP1, and ACE were measured. WTT3 showed decreased IVSTd and increased LVEDD versus WTsal (p < 0.05). β1-KOT3 exhibited lower LVEDD and higher relative IVSTd versus β1-KOsal, the lowest levels of ejection fraction, and the highest levels of cardiomyocyte diameter (p < 0.05). Cardiac ANP levels decreased in WTT3 versus β1-KOT3 (p < 0.05). Cardiac ACE expression was increased in T3-treated groups (p < 0.05). Phosphorylated-p38 MAPK levels were higher in WTT3 versus WTsal or β1-KOT3, p-4EBP1 was elevated in β1-KO animals, and p-ERK1/2 was up-regulated in β1-KOT3. These findings suggest that β1-AR signaling is crucial for TiCH.

µ-Crystallin Is Associated with Disease Outcome in Head and Neck Squamous Cell Carcinoma

Thyroid hormone levels may be associated with disease outcome in head and neck squamous cell carcinoma (HNSCC). µ-Crystallin (CRYM), a thyroid hormone binding protein, blocks intracellular binding of the thyroid hormone T3 to its receptors. In this study, we aimed to analyze the association of CRYM levels with disease outcome in HNSCC patients. We retrospectively assessed immunohistochemical CRYM expression in 121 head and neck cancer patients. Preoperative thyrotropin levels could be extracted for 50 patients. Patients with low thyrotropin levels had a worse prognosis compared to euthyroid patients (5-year overall survival TSH low 20% vs. TSH norm 58%). We observed an association of CRYM+ patients with improved overall survival (5-year overall survival for CRYM+ 78.6% vs. CRYM− 56%). Interaction analysis between CRYM and HPV revealed that this effect was limited to HPV− patients (CRYM+|HPV− HR 0.12, 95% CI 0.01–0.87, p = 0.036). These results were replicated in an independent dataset. CRYM expression identified patients with favorable disease progression for HPV− HNSCC patients and could serve as a useful biomarker in this patient population. This study further confirms a correlation of thyroid hormone levels with adverse disease outcome in HNSCC patients, which could be potentially exploited as a therapeutic target.

Main Factors Involved in Thyroid Hormone Action

The thyroid hormone receptors are the mediators of a multitude of actions by the thyroid hormones in cells. Most thyroid hormone activities require interaction with nuclear receptors to bind DNA and regulate the expression of target genes. In addition to genomic regulation, thyroid hormones function via activation of specific cytosolic pathways, bypassing interaction with nuclear DNA. In the present work, we reviewed the most recent literature on the characteristics and roles of different factors involved in thyroid hormone function in particular, we discuss the genomic activity of thyroid hormone receptors in the nucleus and the functions of different thyroid hormone receptor isoforms in the cytosol. Furthermore, we describe the integrin αvβ3-mediated thyroid hormone signaling pathway and its rapid nongenomic action in the cell. We furthermore reviewed the thyroid hormone transporters enabling the uptake of thyroid hormones in the cell, and we also include a paragraph on the proteins that mediate thyroid receptors’ shuttling from the nucleus to the cytosol.

Targeting the DIO3 enzyme using first-in-class inhibitors effectively suppresses tumor growth: a new paradigm in ovarian cancer treatment

The enzyme iodothyronine deiodinase type 3 (DIO3) contributes to cancer proliferation by inactivating the tumor-suppressive actions of thyroid hormone (T3). We recently established DIO3 involvement in the progression of high-grade serous ovarian cancer (HGSOC). Here we provide a link between high DIO3 expression and lower survival in patients, similar to common disease markers such as Ki67, PAX8, CA-125, and CCNE1. These observations suggest that DIO3 is a logical target for inhibition. Using a DIO3 mimic, we developed original DIO3 inhibitors that contain a core of dibromomaleic anhydride (DBRMD) as scaffold. Two compounds, PBENZ-DBRMD and ITYR-DBRMD, demonstrated attenuated cell counts, induction in apoptosis, and a reduction in cell proliferation in DIO3-positive HGSOC cells (OVCAR3 and KURAMOCHI), but not in DIO3-negative normal ovary cells (CHOK1) and OVCAR3 depleted for DIO3 or its substrate, T3. Potent tumor inhibition with a high safety profile was further established in HGSOC xenograft model, with no effect in DIO3-depleted tumors. The antitumor effects are mediated by downregulation in an array of pro-cancerous proteins, the majority of which known to be repressed by T3. To conclude, using small molecules that specifically target the DIO3 enzyme we present a new treatment paradigm for ovarian cancer and potentially other DIO3-dependent malignancies.

Nuclear αvβ3 integrin expression, post translational modifications and regulation in hematological malignancies

αvβ3 integrin, a plasma membrane protein, is amply expressed on an array of tumors. We identified nuclear αvβ3 pool in ovarian cancer cells and were interested to explore this phenomenon in two rare and aggressive types of leukemia, T-cell acute lymphoblastic leukemia (T-ALL) and Mast cell leukemia (MCL) using Jurkat and HMC-1 cell lines, respectively. Moreover, we collected primary cells from patients with chronic lymphocytic leukemia (CLL, n = 11), the most common chronic adult leukemia and used human lymphoblastoid cell lines (LCL) generated from normal B cells. Nuclear αvβ3 integrin was assessed by Western blots, confocal microscopy, and the ImageStream technology which combines flow-cytometry with microscopy. We further examined post translational modifications (phosphorylation/glycosylation), nuclear trafficking regulation using inhibitors for MAPK (U0126) and PI3K (LY294002), as well as nuclear interactions by performing Co-immunoprecipitation (Co-IP). αvβ3 integrin was identified in all cell models within the nucleus and is N-glycosylated. In primary CLL cells the β3 integrin monomer is tyrosine Y759 phosphorylated, suggesting an active receptor conformation. MAPK and PI3K inhibition in Jurkat and CLL cells led to αvβ3 enhancement in the nucleus and a reduction in the membrane. The nuclear αvβ3 integrin interacts with ERK, Histone H3 and Lamin B1 in Jurkat, Histone H3 in CLL cells, but not in control LCL cells. To conclude, this observational study provides the identification of nuclear αvβ3 in hematological malignancies and lays the basis for novel cancer-relevant actions, which may be independent from the membrane functions.

Multiple bioanalytical methods reveal a thyroid-disrupting mechanism related to the membrane receptor integrin αvβ3

Di(2-ethylhexyl) phthalate (DEHP), a manufactured chemical, is suitable for large-scale production and has extensive applications. Although restricted for use, DEHP is still ubiquitous in the environment and shows potential to disrupt the structure or function of the thyroid system. However, its toxic mechanism is complex and not clearly understood. In this study, a battery of methods was employed to investigate DEHP-induced thyroid-disrupting effects and their mechanism of action, focusing on a newly discovered membrane receptor-mediated mechanism. The results showed that DEHP promoted rat pituitary tumor (GH3) cell proliferation and c-fos gene expression at environment level concentrations (2 and 5 μmol/L) in a manner similar to that of the natural thyroid hormone 3,3',5-triiodo-L-thyronine (T3). The macromolecule DEHP-BSA cannot pass through the cell membrane to interact with nuclear receptors but upregulated the c-fos gene expression when administered at concentrations comparable to DEHP concentrations; molecular docking demonstrated that DEHP has affinity for the membrane receptor integrin α_vβ₃; DEHP at 2 μmol/L upregulated the β₃ gene expression in GH3 cells; after the addition of integrin α_vβ₃-inhibiting RGD peptide, DEHP-induced c-fos gene upregulation decreased. All of these findings support the supposition that DEHP-induced thyroid-disrupting effects might be mediated by the membrane receptor integrin α_vβ₃. Moreover, DEHP activated the downstream extracellular regulated protein kinase (ERK1/2) pathway, upregulating the gene expression of raf-1, MEK-1 and MAPK1 and increasing the protein levels of p-ERK; interestingly, ERK1/2 activation and c-fos upregulation induced by DEHP were attenuated by PD98059 (an ERK1/2 inhibitor). Taken together, the data suggest that the membrane receptor integrin α_vβ₃ and the downstream ERK1/2 pathway might be involved in DEHP-induced thyroid-disrupting effects. This study provides new insight into the thyroid-disrupting effect and the underlying mechanism and will advance the effort to construct adverse outcome pathways of DEHP and other thyroid hormone disrupting chemicals.

αvβ3 Integrin Expression and Mitogenic Effects by Thyroid Hormones in Chronic Lymphocytic Leukemia

Background: Chronic lymphocytic leukemia (CLL) is the most common adult leukemia. The thyroid hormones, T3 and T4, bind the αvβ3 integrin and activate phosphorylates ERK (pERK). These tumor-promoting actions were reported in a number of malignancies, but not in CLL. Methods: Primary cells from 22 CLL patients were verified for disease markers (CD5/CD19/CD23) and analyzed for αvβ3 by flow cytometry (FC), ImageStream, Western blots (WB), and immunohistochemistry (IHC) in archival bone marrow (BM, n = 6) and lymph node (LN, n = 5) tissues. Selected samples (n = 8) were incubated with T3 (1–100 nM) or T4 (0.1–10 µM) for 30 min, and the expression levels of αvβ3, pERK and PCNA (cell proliferation marker) were determined (WB). Results: αvβ3 was detected on the membrane of circulating CLL cells and in the BM but not in the LN. T3 and T4 enhanced αvβ3 protein levels in primary CLL cells. Similarly, pERK and PCNA were rapidly induced in response to T3 and T4 exposure. Conclusions: αvβ3 integrin is expressed on primary CLL cells and is induced by thyroid hormones. We further suggest that the hormones are mitogenic in these cells, presumably via αvβ3-mediated signaling.

Inhibition by Thyroid Hormones of Cell Migration Activated by IGF-1 and MCP-1 in THP-1 Monocytes: Focus on Signal Transduction Events Proximal to Integrin αvβ3

Interaction between thyroid hormones and the immune system is reported in the literature. Thyroid hormones, thyroxine, T₄, but also T₃, act non-genomically through mechanisms that involve a plasma membrane receptor αvβ3 integrin, a co-receptor for insulin-like growth factor-1 (IGF-1). Previous data from our laboratory show a crosstalk between thyroid hormones and IGF-1 because thyroid hormones inhibit the IGF-1-stimulated glucose uptake and cell proliferation in L-6 myoblasts, and the effects are mediated by integrin αvβ3. IGF-1 also behaves as a chemokine, being an important factor for tissue regeneration after damage. In the present study, using THP-1 human leukemic monocytes, expressing αvβ3 integrin in their cell membrane, we focused on the crosstalk between thyroid hormones and either IGF-1 or monocyte chemoattractant protein-1 (MCP-1), studying cell migration and proliferation stimulated by the two chemokines, and the role of αvβ3 integrin, using inhibitors of αvβ3 integrin and downstream pathways. Our results show that IGF-1 is a potent chemoattractant in THP-1 monocytes, stimulating cell migration, and thyroid hormone inhibits the effect through αvβ3 integrin. Thyroid hormone also inhibits IGF-1-stimulated cell proliferation through αvβ3 integrin, an example of a crosstalk between genomic and non-genomic effects. We also studied the effects of thyroid hormone on cell migration and proliferation induced by MCP-1, together with the pathways involved, by a pharmacological approach and docking simulation. Our findings show a different downstream signaling for IGF-1 and MCP-1 in THP-1 monocytes mediated by the plasma membrane receptor of thyroid hormones, integrin αvβ3.

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.

Enhanced expression of αVβ3 integrin in villus and extravillous trophoblasts of placenta accreta

BACKGROUND

Placenta accreta is one of the most serious complications in obstetrics and gynecology. Villous trophoblasts (VT) and extravillous trophoblasts (EVT) play a central role in normal placentation. Placenta accreta is characterized by abnormal invasion of EVT cells through the uterine layers, due to changes in several parameters, including adhesion proteins. Although αvβ3 integrin is a central adhesion molecule, participating in multiple invasive pathological conditions including cancer, data on placenta accreta are lacking.

OBJECTIVE

To study the expression pattern of αvβ3 integrin in placenta accreta in comparison with normal placentas.

STUDY DESIGN

We collected tissue samples from placentas defined as percreta, the most severe presentation of placenta accreta and from normal control placentas (n = 10 each). The samples underwent protein extractions for analyses of αvβ3 expression by Western blots (WB) and a parallel tissue assessment by immunohistochemistry (IHC).

RESULTS

WB results indicated significantly elevated αvβ3 integrin expression in the percreta samples compared to normal placentas. These elevated levels were mainly contributed by EVT cells, as demonstrated by IHC. αvβ3 integrin demonstrated a classical membranal expression in the VT cells, whereas a uniformly distributed expression was documented in the EVT cells. These patterns of the αvβ3 integrin localization were similar in both accreta and normal placental samples.

CONCLUSIONS

Enhanced αvβ3 integrin expression, mainly in extra villous trophoblasts of placenta percreta, implies for a role of this adhesion molecule in pathological placentation.

The identification of nuclear αvβ3 integrin in ovarian cancer: non-paradigmal localization with cancer promoting actions

Nuclear translocation of transmembrane proteins was reported in high-grade serous ovarian cancer (HGSOC), a highly aggressive gynecological malignancy. Although the membrane receptor αvβ3 integrin is amply expressed in HGSOC and involved in disease progression, its nuclear localization was never demonstrated. Nuclear αvβ3 was explored in HGSOC cells (OVCAR3, KURAMOCHI, and JHOS4), nuclear localization signal (NLS) modified β3 OVCAR3, Chinese hamster ovaries (CHO-K1) and human embryonic kidney (HEK293) before/after transfections with β3/β1 integrins. We used the ImageStream technology, Western blots (WB), co immunoprecipitations (Co-IP), confocal immunofluorescence (IF) microscopy, flow cytometry for cell counts and cell cycle, wound healing assays and proteomics analyses. Fresh/archived tumor tissues were collected from nine HGSOC patients and normal ovarian and fallopian tube (FT) tissues from eight nononcological patients and assessed for nuclear αvβ3 by WB, confocal IF microscopy and immunohistochemistry (IHC). We identified nuclear αvβ3 in HGSOC cells and tissues, but not in normal ovaries and FTs. The nuclear integrin was Tyr 759 phosphorylated and functionally active. Nuclear αvβ3 enriched OVCAR3 cells demonstrated induced proliferation and oncogenic signaling, intact colony formation ability and inhibited migration. Proteomics analyses revealed a network of nuclear αvβ3-bound proteins, many of which with key cancer-relevant activities. Identification of atypical nuclear localization of the αvβ3 integrin in HGSOC challenges the prevalent conception that the setting in which this receptor exerts its pleiotropic actions is exclusively at the cell membrane. This discovery proposes αvβ3 moonlighting functions and may improve our understanding of the molecular basis of ovarian cancer pathogenesis.

Actions of L-thyroxine (T4) and Tetraiodothyroacetic Acid (Tetrac) on Gene Expression in Thyroid Cancer Cells

The clinical behavior of thyroid cancers is seen to reflect inherent transcriptional activities of mutated genes and trophic effects on tumors of circulating pituitary thyrotropin (TSH). The thyroid hormone, L-thyroxine (T4), has been shown to stimulate proliferation of a large number of different forms of cancer. This activity of T4 is mediated by a cell surface receptor on the extracellular domain of integrin αvβ3. In this brief review, we describe what is known about T4 as a circulating trophic factor for differentiated (papillary and follicular) thyroid cancers. Given T4′s cancer-stimulating activity in differentiated thyroid cancers, it was not surprising to find that genomic actions of T4 were anti-apoptotic. Transduction of the T4-generated signal at the integrin primarily involved mitogen-activated protein kinase (MAPK). In thyroid C cell-origin medullary carcinoma of the thyroid (MTC), effects of thyroid hormone analogues, such as tetraiodothyroacetic acid (tetrac), include pro-angiogenic and apoptosis-linked genes. Tetrac is an inhibitor of the actions of T4 at αvβ3, and it is assumed, but not yet proved, that the anti-angiogenic and pro-apoptotic actions of tetrac in MTC cells are matched by T4 effects that are pro-angiogenic and anti-apoptotic. We also note that papillary thyroid carcinoma cells may express the leptin receptor, and circulating leptin from adipocytes may stimulate tumor cell proliferation. Transcription was stimulated by leptin in anaplastic, papillary, and follicular carcinomas of genes involved in invasion, such as matrix metalloproteinases (MMPs). In summary, thyroid hormone analogues may act at their receptor on integrin αvβ3 in a variety of types of thyroid cancer to modulate transcription of genes relevant to tumor invasiveness, apoptosis, and angiogenesis. These effects are independent of TSH.

Nongenomic Actions of Thyroid Hormone: The Integrin Component

The extracellular domain of plasma membrane integrin αvβ3 contains a cell surface receptor for thyroid hormone analogues. The receptor is largely expressed and activated in tumor cells and rapidly dividing endothelial cells. The principal ligand for this receptor is l-thyroxine (T₄), usually regarded only as a prohormone for 3,5,3'-triiodo-l-thyronine (T₃), the hormone analogue that expresses thyroid hormone in the cell nucleus via nuclear receptors that are unrelated structurally to integrin αvβ3. At the integrin receptor for thyroid hormone, T₄ regulates cancer and endothelial cell division, tumor cell defense pathways (such as anti-apoptosis), and angiogenesis and supports metastasis, radioresistance, and chemoresistance. The molecular mechanisms involve signal transduction via mitogen-activated protein kinase and phosphatidylinositol 3-kinase, differential expression of multiple genes related to the listed cell processes, and regulation of activities of other cell surface proteins, such as vascular growth factor receptors. Tetraiodothyroacetic acid (tetrac) is derived from T₄ and competes with binding of T₄ to the integrin. In the absence of T₄, tetrac and chemically modified tetrac also have anticancer effects that culminate in altered gene transcription. Tumor xenografts are arrested by unmodified and chemically modified tetrac. The receptor requires further characterization in terms of contributions to nonmalignant cells, such as platelets and phagocytes. The integrin αvβ3 receptor for thyroid hormone offers a large panel of cellular actions that are relevant to cancer biology and that may be regulated by tetrac derivatives.

Integrative analysis of key candidate genes and signaling pathways in autoimmune thyroid dysfunction related to anti-CTLA-4 therapy by bioinformatics

Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), the first immune checkpoint to be targeted clinically, has provided an effective treatment option for various malignancies. However, the clinical advantages associated with CTLA-4 inhibitors can be offset by the potentially severe immune-related adverse events (IRAEs), including autoimmune thyroid dysfunction. To investigate the candidate genes and signaling pathways involving in autoimmune thyroid dysfunction related to anti-CTLA-4 therapy, integrated differentially expressed genes (DEGs) were extracted from the intersection of genes from Gene Expression Omnibus (GEO) datasets and text mining. The functional enrichment was performed by gene ontology (GO) annotation and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis. Protein-protein interaction (PPI) network, module enrichment, and hub gene identification were constructed and visualized by the online Search Tool for the Retrieval of Interacting Genes (STRING) and Cytoscape software. A total of 22 and 17 integrated human DEGs in hypothyroidism and hyperthyroidism group related to anti-CTLA-4 therapy were identified, respectively. Functional enrichment analysis revealed 24 GO terms and 1 KEGG pathways in the hypothyroid group and 21 GO terms and 2 KEGG pathways in the hyperthyroid group. After PPI network construction, the top five hub genes associated with hypothyroidism were extracted, including ALB, MAPK1, SPP1, PPARG, and MIF, whereas those associated with hyperthyroidism were ALB, FCGR2B, CD44, LCN2, and CD74. The identification of the candidate key genes and enriched signaling pathways provides potential biomarkers for autoimmune thyroid dysfunction related to anti-CTLA-4 therapy and might contribute to the future diagnosis and management of IRAEs for cancer patients.

Thyroid Hormone in Hepatocellular Carcinoma: Cancer Risk, Growth Regulation, and Anticancer Drug Resistance

Thyroid hormone (TH) and its receptor (TR) are involved in differentiation, metabolic process, and growth regulation in hepatocellular carcinoma (HCC). The TH/TR complexes are ligand-dependent transcriptional factors, functioning through binding to thyroid hormone response elements (TREs) upstream of the target genes. To date, deciphering the biological effects of TH in cancer progression remains challenging. Several lines of evidence suggest a growth inhibitory effect of TH in liver cancer. Mutation and aberrant expression of TRs are highly correlated with several types of cancers including HCC. Several reports show that TH inhibits cell growth in liver cancer through regulation of cell-cycle-related genes and non-coding RNAs. A case–control study indicates that hypothyroidism is associated with an increased risk of HCC. Moreover, TH/TR suppresses hepatocarcinogenesis via selective autophagy. Conversely, other groups have indicated that TH promotes cancer cell proliferation. In vitro and in vivo experiments show that TH/TR enhances cancer cell migration and invasion, anticancer drug resistance, angiogenesis, and cancer stem cell self-renewal. Adding to the complexity of this issue, non-genomic effects of TH mediated by integrin receptor on cell surface can also modulate several biological functions. Accumulating evidence indicate that regulations by genomic and non-genomic effects of TH overlap. Taken together, these observations suggest that the functions of TH depend largely on cell context, and TH/TR plays a duel role in cancer progression. Therefore, understanding the maze of biological effects of TH has become a necessity when attempting to develop effective therapeutic and preventive strategies in liver cancer.

Pharmacokinetics, Biodistribution, and Anti-Angiogenesis Efficacy of Diamino Propane Tetraiodothyroacetic Acid-conjugated Biodegradable Polymeric Nanoparticle

The anti-angiogenic agent, diamino propane tetraiodothyroacetic acid (DAT), is a thyro-integrin (integrin αvβ3) antagonist anticancer agent that works via genetic and nongenetic actions. Tetraiodothyroacetic acid (tetrac) and DAT as thyroid hormone derivatives influence gene expression after they transport across cellular membranes. To restrict the action of DAT to the integrin αvβ3 receptors on the cell surface, we used DAT-conjugated PLGA nanoparticles (NDAT) in an active targeting mode to bind to these receptors. Preparation and characterization of NDAT is described, and both in vitro and in vivo experiments were done to compare DAT to NDAT. Intracellular uptake and distribution of DAT and NDAT in U87 glioblastoma cells were evaluated using confocal microscopy and showed that DAT reached the nucleus, but NDAT was restricted from the nucleus. Pharmacokinetic studies using LC-MS/MS analysis in male C57BL/6 mice showed that administration of NDAT improved the area under the drug concentration curve AUC(0-48 h) by 4-fold at a dose of 3 mg/kg when compared with DAT, and Cmax of NDAT (4363 ng/mL) was 8-fold greater than that of DAT (548 ng/mL). Biodistribution studies in the mice showed that the concentrations of NDAT were higher than DAT/Cremophor EL micelles in heart, lung, liver, spleen, and kidney. In another mouse model using female NCr nude homozygous mice with U87 xenografts, tumor growth was significantly decreased at doses of 1 and 3 mg/kg of NDAT. In the chick chorioallantoic membrane (CAM) assay used to measure angiogenesis, DAT (500 ng/CAM) resulted in 48% inhibition of angiogenesis levels. In comparison, NDAT at low dose (50 ng/CAM) showed 45% inhibition of angiogenesis levels. Our investigation of NDAT bridges the study of polymeric nanoparticles and anti-angiogenic agents and offers new insight for the rational design of anti-angiogenic agents.

Thyroid Hormones and Cancer: A Comprehensive Review of Preclinical and Clinical Studies

Thyroid hormones take major part in normal growth, development and metabolism. Over a century of research has supported a relationship between thyroid hormones and the pathophysiology of various cancer types. In vitro studies as well as research in animal models demonstrated an effect of the thyroid hormones T3 and T4 on cancer proliferation, apoptosis, invasiveness and angiogenesis. Thyroid hormones mediate their effects on the cancer cell through several non-genomic pathways including activation of the plasma membrane receptor integrin αvβ3. Furthermore, cancer development and progression are affected by dysregulation of local bioavailability of thyroid hormones. Case-control and population-based studies provide conflicting results regarding the association between thyroid hormones and cancer. However, a large body of evidence suggests that subclinical and clinical hyperthyroidism increase the risk of several solid malignancies while hypothyroidism may reduce aggressiveness or delay the onset of cancer. Additional support is provided from studies in which dysregulation of the thyroid hormone axis secondary to cancer treatment or thyroid hormone supplementation was shown to affect cancer outcomes. Recent preclinical and clinical studies in various cancer types have further shown promising outcomes following chemical reduction of thyroid hormones or inhibition or their binding to the integrin receptor. This review provides a comprehensive overview of the preclinical and clinical research conducted so far.

Radioresistance of cancer cells, integrin αvβ3 and thyroid hormone

Radioresistance is a substantial barrier to success in cancer management. A number of molecular mechanisms support radioresistance. We have shown experimentally that the thyroid hormone analogue receptor on the extracellular domain of integrin αvβ3 may modulate the state of radiosensitivity of tumor cells. Specifically, tetraiodothyroacetic acid (tetrac), a derivative of L-thyroxine (T₄), can reduce radioresistance in cancer cells. In this review, we list a number of intrinsic signal transduction molecules and other host factors that have been reported to support/induce radioresistance in cancer cells and that are also subject to control by T₄ through actions primarily initiated at integrin αvβ3. Additional preclinical evidence is needed to support these radioresistance-relevant actions of thyroid hormone.

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.

Chemical and thyroid hormone profile of the bone marrow interstitial fluid in hematologic disorders and patients without primary hematologic disorders

Bone marrow interstitial fluid (BMIF) has not been well characterized. BMIF was isolated from 60 patients including plasma cell dyscrasias (PCD, n = 33), other primary hematologic disorders (OHD, n = 15), and patients with secondary or nonhemtologic disorders (NHD, n = 12) and analyzed for an array of chemical constituents. These included total cholesterol, glucose, phosphate, creatinine, urea, total protein, albumin, globulins, total bilirubin, aspartate aminotransferase, lactate dehydrogenase, sodium, osmolarity, free triiodothyronine (free T3), total triiodothyronine (total T3), and free tetraiodothyronine (free T4). Levels of BMIF components were compared between patient groups and to plasma levels. Compared with plasma, total cholesterol, total protein, total bilirubin, sodium, and calculated osmolarity were lower in BMIF in all groups (P < 0.05). Calculated globulins and aspartate aminotransferase were lower in BMIF of PCD patients and patients with NHD. Albumin was lower in BMIF of patients with PCD and patients with OHD. Lastly, free T4 was significantly higher in BMIF of patients with PCD and patients with OHD. Similar results were demonstrated in a separate analysis performed in patients with multiple myeloma. To conclude, the chemical and thyroid hormone composition of BMIF differs significantly from plasma in several key constituents.

Tetrac Delayed the Onset of Ocular Melanoma in an Orthotopic Mouse Model

Ocular melanoma research, the most common primary intraocular malignancy in adults, is hindered by limited in vivo models. In a series of experiments using melanoma cells injected intraocularly into mouse eyes, we developed a model for ocular melanoma. Inoculation of 5 × 10⁵ B16F10 cells led to rapid tumor growth, extensive lung metastasis, and limited animal survival, while injection of 10² cells was sufficient for intraocular tumors to grow with extended survival. In order to improve tumor visualization, 10² melanoma cells (B16F10 or B16LS9) were inoculated into Balb/C albino mouse eyes. These mice developed intraocular tumors that did not metastasize and exhibited extended survival. Next, we studied the therapeutic potential of inhibitor of the thyroid hormones-αvβ3 integrin signaling pathway in ocular melanoma. By utilizing tetraiodothyroacetic acid (tetrac), a thyroid hormone derivative, a delay in tumor onset in the B16F10 (integrin+) arm was observed, compared to the untreated group, while in the B16LS9 cells (integrin-) a similar rate of tumor onset was noticed in both experimental and control groups. In summary, following an optimization process, the mouse ocular melanoma model was developed. The models exhibited an extended therapeutic window and can be utilized as a platform for investigating various drugs and other treatment modalities.

The induction of myeloma cell death and DNA damage by tetrac, a thyroid hormone derivative

Multiple myeloma (MM) is a plasma cell malignancy in which involvement of the thyroid hormone-integrin αvβ3 pathway was shown, and pharmacologic inhibition of this pathway is a rational approach to disease management. A thyroid hormone derivative, tetraiodothyroacetic acid (tetrac), which inhibits l-thyroxine (T₄) and 3,5,3'-triiodo-l-thyronine (T₃) binding to αvβ3 integrin, was studied in five MM cell lines and primary bone marrow (BM) MM cells. Tetrac inhibited MM cell proliferation (absolute cell number/viability) and induced caspase-dependent apoptosis (annexin-V/PI and cell cycle). Activation of caspase-9 and caspase-3 was further demonstrated. Moreover, DNA damage markers, ataxia-telangiectasia-mutated (ATM) kinase, poly ADP-ribose polymerase (PARP-1) and histone γH2AX were induced by tetrac. The various tetrac-initiated effects were attenuated by Arg-Gly-Asp (RGD) peptide, suggesting integrin involvement. Primary BM mononuclear cells were harvested from MM patients (n = 39) at various disease stages. Tetrac-induced apoptosis (12/17 samples) and sensitized the cytotoxic action of bortezomib (6/9 samples). Lastly, expression of plasma membrane integrin αvβ3 was shown not only in the malignant plasma clone, but also in other cell populations within the BM samples (n = 25). Tetrac is anti-proliferative and pro-apoptotic in MM and cells may offer a therapeutic approach for this disease.

The Interplay Between Epithelial-Mesenchymal Transition (EMT) and the Thyroid Hormones-αvβ3 Axis in Ovarian Cancer

Ovarian cancer is a highly metastatic disease. The metastatic potential is enhanced by epithelial to mesenchymal transition (EMT) in which αvβ3 integrin plays a role. Thyroid hormones (L-thyroxine, T4, and 3,5,3'-triiodo-L-thyronine, T3) bind this integrin, and we hypothesized that the thyroid hormone-αvβ3 axis may be involved in EMT activity in ovarian cancer. The transcription (mRNA), protein abundance (westerns), and protein localization (fluorescence microscopy) of several EMT markers were studied in ovarian cancer cells (OVCAR-3, A2780, and SKOV-3) treated with 1 nM T3 or 100 nM T4 for 1-24 h. The protein levels of β-catenin, and its downstream targets, zeb-1, slug, and vimentin, were significantly induced by both hormones, while the effect on transcription was limited. The pre-incubation of the cells overnight with two integrin inhibitors, RGD (0.1-10 μM) or αvβ3 blocking antibody (1-100 ng/mL), prevented the induction of β-catenin by T3 and zeb-1 by T4, indicating direct integrin involvement. The transcription of the mesenchymal markers, β-catenin, zeb-1, slug/snail, vimentin, and n-cadherin was hardly affected by T3 and T4, while that of the epithelial markers, e-cadherin and zo-1, was inhibited. Our results suggest a novel role for the thyroid hormone-αvβ3 axis in EMT, with possible implications for ovarian cancer metastasis.

Thyroid hormones derivatives reduce proliferation and induce cell death and DNA damage in ovarian cancer

Ovarian cancer is a highly aggressive disease and novel treatments are required. Thyroid hormones binding to αvβ3 integrin produced growth-promoting activities in ovarian cancer and we hypothesized that natural thyroid hormone derivatives may antagonize these actions. The effect of three antagonists, tetraiodoacetic acid (tetrac), triiodothyroacetic acid (triac) and 3-iodothyronamine (T1AM), on cell proliferation, cell death and DNA damage was studied in two ovarian cancer cell lines (OVCAR3 and A2780), normal hamster ovary control cells (CHOK1) and αvβ3-deficient or transfected HEK293 cells. A differential inhibition of cell proliferation was observed in ovarian cancer cells compared to CHOK1. In OVCAR3, an induction of cell cycle regulators was further shown. Apoptosis was confirmed (annexin-PI, SubG1/cell-cycle, apoptotic genes, caspase-3 and poly ADP ribose polymerase-1 (PARP-1) cleavage) and was reversed by a pan-caspase inhibitor. Induction in apoptosis inducing factor (AIF) was observed, suggesting a parallel caspase-independent mechanism. Integrin-involvement in triac/T1AM apoptotic action was shown in αvβ3-transfected HEK293 cells. Lastly, in ovarian cancer models, key proteins that coordinate recognition of DNA damage, ataxia-telangiectasia mutated (ATM) and PARP-1, were induced. To conclude, the cytotoxic potential of thyroid hormone derivatives, tetrac, triac and T1AM, in ovarian cancer may provide a much-needed novel therapeutic approach.

Molecular insights into the transcriptional regulatory role of thyroid hormones in ovarian cancer

The regulation of cancer-relevant genes by the thyroid hormones, 3, 5, 3'-Triiodo-L-thyronine (T3) and L-thyroxine (T4), was recently acknowledged. However, limited data exists on the hormonal effects on gene expression in ovarian cancer, a gynecological malignancy associated with a low cure rate. The expression of fifteen genes involved in DNA repair, cell cycle, apoptosis, and tumor suppression was evaluated in OVCAR-3 and A2780 cell lines, using real-time PCR following short incubation with T3 (1 nM) or T4 (100 nM). The thyroid hormones downregulated the expression of the majority of genes examined. Support for the involvement of the MAPK and PI3K in thyroid hormone-mediated gene expression was shown for a set of genes. FAS expression was inhibited in A2780 cells, while an unexpected induction was demonstrated in OVCAR-3 cells. An analogous effect on the protein levels of FAS receptor and its soluble form was demonstrated by Western blotting. We further established, using primer sets that discriminate between the different RNA isoforms, that the hormones increase the mRNA levels of both coding and non-coding FAS mRNAs. The prevalence of these isoforms, using The Cancer Genome Atlas (TCGA) analysis, was significantly more abundant in 17 cancer types, including ovarian cancer, compared to normal tissues. Our results highlight the role of thyroid hormones in the expression of cancer-relevant-genes in ovarian cancer and provide an important insight into the pathways by which mitogenic and anti-apoptotic effects are exerted.

Molecular Basis of Nongenomic Actions of Thyroid Hormone

Nongenomic actions of thyroid hormone are initiated by the hormone at receptors in the plasma membrane, in cytoplasm, or in mitochondria and do not require the interaction of nuclear thyroid hormone receptors (TRs) with their primary ligand, 3,5,3'-triiodo-l-thyronine (T₃). Receptors involved in nongenomic actions may or may not have structural homologies with TRs. Certain nongenomic actions that originate at the plasma membrane may modify the state and function of intranuclear TRs. Reviewed here are nongenomic effects of the hormone-T₃ or, in some cases, l-thyroxine (T₄)-that are initiated at (a) truncated TRα isoforms, e.g., p30 TRα1, (b) cytoplasmic proteins, or (c) plasma membrane integrin αvβ3. p30 TRα1 is not transcriptionally competent, binds T₃ at the cell surface, and consequently expresses a number of important functions in bone cells. Nongenomic hormonal control of mitochondrial respiration involves a TRα isoform, and another truncated TRα isoform nongenomically regulates the state of cellular actin. Cytoplasmic hormone-binding proteins involved in nongenomic actions of thyroid hormone include ketimine reductase, pyruvate kinase, and TRβ that shuttle among intracellular compartments. Functions of the receptor for T₄ on integrin αvβ3 include stimulation of proliferation of cancer and endothelial cells (angiogenesis) and regulation of transcription of cancer cell survival pathway genes. T₄ serves as a prohormone for T₃ in genomic actions of thyroid hormone, but T₄ is a hormone at αvβ3 and more important to cancer cell function than is T₃. Thus, characterization of nongenomic actions of the hormone has served to broaden our understanding of the cellular roles of T₃ and T₄.

The combination of tetraiodothyroacetic acid and cetuximab inhibits cell proliferation in colorectal cancers with different K-ras status

Thyroid hormone induces cancer cell proliferation through its cell surface receptor integrin αvβ3. Acting via integrin αvβ3, the deaminated T4 analog tetraiodothyroacetic acid (tetrac), and its nanoparticle formulation nano-diamino-tetrac (NDAT) could inhibit cell proliferation and xenograft growth. In this study, we investigated the T4 effects on proliferation in colorectal cancer cell lines based on the proliferation marker expressions at both mRNA and protein levels. The effects of tetrac/NDAT, the monoclonal anti-EGFR antibody cetuximab, and their combinations on colorectal cancer cell proliferation were examined according to the relevant gene expression profiles and cell count analysis. The results showed that T4 significantly enhanced PCNA, Cyclin D1 and c-Myc levels in both K-ras wild type HT-29 and mutant HCT 116 cells. In HCT 116 cells, the combination of NDAT and cetuximab significantly suppressed the mRNA expressions of proliferative genes PCNA, Cyclin D1, c-Myc and RRM2 raised by T4 compared to cetuximab alone. In addition, T4-suppressed mRNA expressions of pro-apoptotic genes p53 and RRM2B could be significantly elevated by the combination of NDAT and cetuximab compared to cetuximab alone. In the K-ras mutant HCT 116 cells, but not in the K-ras wild type COLO 205 cells, the combinations of tetrac/NDAT and cetuximab significantly reduced cell proliferation compared to cetuximab alone. In conclusion, T4 promoted colorectal cancer cell proliferation which could be repressed by tetrac and NDAT. The combinations of tetrac/NDAT and cetuximab potentiated cetuximab actions in K-ras mutant colorectal cancer cells.

Hypothyroidism in Pancreatic Cancer: Role of Exogenous Thyroid Hormone in Tumor Invasion-Preliminary Observations

According to the epidemiological studies, about 4.4% of American general elderly population has a pronounced hypothyroidism and relies on thyroid hormone supplements daily. The prevalence of hypothyroidism in our patients with pancreatic cancer was much higher, 14.1%. A retrospective analysis was performed on patients who underwent pancreaticoduodenectomy (Whipple procedure) or distal pancreatectomy and splenectomy (DPS) at Thomas Jefferson University Hospital, Philadelphia, from 2005 to 2012. The diagnosis of hypothyroidism was correlated with clinicopathologic parameters including tumor stage, grade, and survival. To further understand how thyroid hormone affects pancreatic cancer behavior, functional studies including wound-induced cell migration, proliferation, and invasion were performed on pancreatic cancer cell lines, MiaPaCa-2 and AsPC-1. We found that hypothyroid patients taking exogenous thyroid hormone were more than three times likely to have perineural invasion, and about twice as likely to have higher T stage, nodal spread, and overall poorer prognostic stage (P < 0.05). Pancreatic cancer cell line studies demonstrated that exogenous thyroid hormone treatment increased cell proliferation, migration, and invasion (P < 0.05). We conclude that exogenous thyroid hormone may contribute to the progression of pancreatic cancer.

Thyroid hormone regulates adhesion, migration and matrix metalloproteinase 9 activity via αvβ3 integrin in myeloma cells

Thyroid hormone (3,5,3′-triiodothyronine, T3; L-thyroxine, T4) enhances cancer cell proliferation, invasion and angiogenesis via a discrete receptor located near the RGD recognition site on αvβ3 integrin. Tetraiodothyroacetic acid (tetrac) and its nanoparticulate formulation interfere with binding of T3/T4 to the integrin. This integrin is overexpressed in multiple myeloma (MM) and other cancers. MM cells interact with αvβ3 integrin to support growth and invasion. Matrix metalloproteinases (MMPs) are a family of enzymes active in tissue remodeling and cancer. The association between integrins and MMPs secretion and action is well established. In the current study, we examined the effects of thyroid hormone on myeloma cell adhesion, migration and MMP activity.

We show that T3 and T4 increased myeloma adhesion to fibronectin and induced αvβ3 clustering. In addition, the hormones induced MMP-9 expression and activation via αvβ3 and MAPK induction. Bortezomib, a standard myeloma treatment, caused a decrease in activity/quantity of MMPs and thyroid hormone opposed this effect. RGD peptide and tetrac impaired the production of MMP-9 in cell lines and in primary BM cells from myeloma patients.

In conclusion, thyroid hormone-dependent regulation via αvβ3 of myeloma cell adhesion and MMP-9 production may play a role in myeloma migration and progression.

The thyroid status reprograms T cell lymphoma growth and modulates immune cell frequencies

In spite of considerable evidence on the regulation of immunity by thyroid hormones, the impact of the thyroid status in tumor immunity is poorly understood. Here, we evaluated the antitumor immune responses evoked in mice with different thyroid status (euthyroid, hyperthyroid, and hypothyroid) that developed solid tumors or metastases after inoculation of syngeneic T lymphoma cells. Hyperthyroid mice showed increased tumor growth along with increased expression of cell cycle regulators compared to hypothyroid and control tumor-bearing mice. However, hypothyroid mice showed a higher frequency of metastases than the other groups. Hyperthyroid mice bearing tumors displayed a lower number of tumor-infiltrating T lymphocytes, lower percentage of functional IFN-γ-producing CD8(+) T cells, and higher percentage of CD19(+) B cells than euthyroid tumor-bearing mice. However, no differences were found in the distribution of lymphocyte subpopulations in tumor-draining lymph nodes (TDLNs) or spleens among different experimental groups. Interestingly, hypothyroid TDLN showed an increased percentage of regulatory T (Treg) cells, while hyperthyroid mice displayed increased number and activity of splenic NK cells, which frequency declined in spleens from hypothyroid mice. Moreover, a decreased number of splenic myeloid-derived suppressor cells (MDSCs) were found in tumor-bearing hyperthyroid mice as compared to hypothyroid or euthyroid mice. Additionally, hyperthyroid mice showed increased cytotoxic activity, which declined in hypothyroid mice. Thus, low levels of intratumoral cytotoxic activity would favor tumor local growth in hyperthyroid mice, while regional and systemic antitumor response may contribute to tumor dissemination in hypothyroid animals. Our results highlight the importance of monitoring the thyroid status in patients with T cell lymphomas.

KEY MESSAGES

T cell lymphoma phenotype is paradoxically influenced by thyroid status. Hyperthyroidism favors tumor growth and hypothyroidism rises tumor dissemination. Thyroid status affects the distribution of immune cell types in the tumor milieu. Thyroid status also modifies the nature of local and systemic immune responses.

The thyroid hormone-αvβ3 integrin axis in ovarian cancer: regulation of gene transcription and MAPK-dependent proliferation

Ovarian carcinoma is the fifth common cause of cancer death in women, despite advanced therapeutic approaches. αvβ3 integrin, a plasma membrane receptor, binds thyroid hormones (L-thyroxine, T4; 3,5,3'-triiodo-L-thyronine, T3) and is overexpressed in ovarian cancer. We have demonstrated selective binding of fluorescently labeled hormones to αvβ3-positive ovarian cancer cells but not to integrin-negative cells. Physiologically relevant T3 (1 nM) and T4 (100 nM) concentrations in OVCAR-3 (high αvβ3) and A2780 (low αvβ3) cells promoted αv and β3 transcription in association with basal integrin levels. This transcription was effectively blocked by RGD (Arg-Gly-Asp) peptide and neutralizing αvβ3 antibodies, excluding T3-induced β3 messenger RNA, suggesting subspecialization of T3 and T4 binding to the integrin receptor pocket. We have provided support for extracellular regulated kinase (ERK)-mediated transcriptional regulation of the αv monomer by T3 and of β3 monomer by both hormones and documented a rapid (30-120 min) and dose-dependent (0.1-1000 nM) ERK activation. OVCAR-3 cells and αvβ3-deficient HEK293 cells treated with αvβ3 blockers confirmed the requirement for an intact thyroid hormone-integrin interaction in ERK activation. In addition, novel data indicated that T4, but not T3, controls integrin's outside-in signaling by phosphorylating tyrosine 759 in the β3 subunit. Both hormones induced cell proliferation (cell counts), survival (Annexin-PI), viability (WST-1) and significantly reduced the expression of genes that inhibit cell cycle (p21, p16), promote mitochondrial apoptosis (Nix, PUMA) and tumor suppression (GDF-15, IGFBP-6), particularly in cells with high integrin expression. At last, we have confirmed that hypothyroid environment attenuated ovarian cancer growth using a novel experimental platform that exploited paired euthyroid and severe hypothyroid serum samples from human subjects. To conclude, our data define a critical role for thyroid hormones as potent αvβ3-ligands, driving ovarian cancer cell proliferation and suggest that disruption of this axis may present a novel treatment strategy in this aggressive disease.

Effect of non-genomic actions of thyroid hormones on the anaesthetic effect of propofol

Hyperthyroidism is a common disease of the endocrine system and it is known that additional propofol anaesthesia is required during surgery for patients with hyperthyroidism compared with those with normal thyroid function. The aim of the present study was to determine the mechanism through which thyroid hormones (THs) inhibit the effect of propofol anaesthesia. Immunofluorescence techniques were used to verify the difference between the expression quantities of γ-aminobutyric acid type A (GABA_A) receptor subunits α2 and β2 in the dorsal root ganglions (DRGs) of rats with hyperthyroidism and those in normal rats. Perforated patch clamp recordings in the whole-cell mode were performed to detect the GABA-activated current in acutely isolated rat DRG neurons from rats with hyperthyroidism and normal rats. This method was also used to evaluate the change in the GABA-activated currents following the pre-perfusion of propofol with and without 3,3',5-L-triiodothyronine (T₃). Compared with normal rats, rats with hyperthyroidism expressed same quantities of GABA_A receptor α2 and β2 subunits in DRGs. In addition, no difference in GABA-activated currents in the acutely isolated DRG neurons from the two types of rat was observed (P>0.05). T₃ inhibits or minimises the augmentation effect of propofol on the GABA-activated currents (P<0.05). The inhibitory effect of T₃ on propofol was minimised by increasing the propofol concentration (P<0.05). The inhibitory effect of T₃ on the anaesthetic effect of propofol is achieved through the inhibition of the function of GABA_A receptors through the non-genomic actions of the THs, rather than by changing the number of GABA_A receptors. This inhibitory effect can be mitigated by increasing the propofol concentration. In conclusion, rats with hyperthyroidism require a larger dose of propofol to induce anaesthesia since the non-genomic actions of THs suppress GABA receptors, which in turn inhibits the anaesthetic action of propofol.

Nanotetrac targets integrin αvβ3 on tumor cells to disorder cell defense pathways and block angiogenesis

The extracellular domain of integrin αvβ3 contains a receptor for thyroid hormone and hormone analogs. The integrin is amply expressed by tumor cells and dividing blood vessel cells. The proangiogenic properties of thyroid hormone and the capacity of the hormone to promote cancer cell proliferation are functions regulated nongenomically by the hormone receptor on αvβ3. An L-thyroxine (T4) analog, tetraiodothyroacetic acid (tetrac), blocks binding of T4 and 3,5,3'-triiodo-L-thyronine (T3) by αvβ3 and inhibits angiogenic activity of thyroid hormone. Covalently bound to a 200 nm nanoparticle that limits its activity to the cell exterior, tetrac reformulated as Nanotetrac has additional effects mediated by αvβ3 beyond the inhibition of binding of T4 and T3 to the integrin. These actions of Nanotetrac include disruption of transcription of cell survival pathway genes, promotion of apoptosis by multiple mechanisms, and interruption of repair of double-strand deoxyribonucleic acid breaks caused by irradiation of cells. Among the genes whose expression is suppressed by Nanotetrac are EGFR, VEGFA, multiple cyclins, catenins, and multiple cytokines. Nanotetrac has been effective as a chemotherapeutic agent in preclinical studies of human cancer xenografts. The low concentrations of αvβ3 on the surface of quiescent nonmalignant cells have minimized toxicity of the agent in animal studies.

Relevance of the thyroid hormones-αvβ3 pathway in primary myeloma bone marrow cells and to bortezomib action

Thyroid hormones (T3 and T4) induce proliferation in multiple myeloma (MM) cell lines via the αvβ3 integrin-mitogen-activated protein kinase (MAPK) pathway. We further show in primary MM bone marrow (BM) samples (n = 9) induction of cell viability by 1 nM T3 (13%, p < 0.002) and more potently by 100 nM T4 (21-45%, p < 0.0002) and a quick (1 h) and long-lasting (24 h) pERK activation, which was inhibited in the presence of β3 but not β1 blocking antibodies. Involvement of the integrin was further shown by two disintegrins, Arg-Gly-Asp (RGD) and echistatin peptides, which occluded the effects of T3/T4 on viability, proliferating cell nuclear antigen (PCNA) (proliferation marker) and apoptotic gene expression. Lastly, T3/T4 significantly opposed bortezomib (25 nM) cytotoxicy, as confirmed by several methods. In summary, our results imply that endogenous thyroid hormones in myeloma are factors that may support cell growth, with relevance to bortezomib action.

Effects of hypo- and hyperthyroid states on herpes simplex virus infectivity in the rat

OBJECTIVE

Available data from in vitro studies show that thyroid hormones (THs) regulate herpes simplex virus (HSV) gene expression and may modulate latency/reactivation of the virus. Whether infectivity of the virus is also affected by THs is not known. Using animal models (in vivo study) and Vero cell culture (in vitro study), we examined the effects of alterations in THs level on HSV-1 infectivity.

METHODS

Rats were rendered hypo- and hyperthyroid by daily addition of methimazole and l-thyroxine into their drinking water, respectively. Euthyroid animals served as control. All animals were given a single dose of HSV-1 (10(7)TCID50, ip) and sacrificed 3 d later. The spleen of the animals was then removed and viral particles were recovered from the tissue extract through aseptic procedures. Serial dilution of the extracts was prepared and added to Vero cell culture. For the in vitro study, the cultures were pretreated with l-thyroxine and the viral particles were then added. Virus titration was determined by Reed-Muench quantal assay.

RESULTS

The viral load of spleen in hyperthyroid rats was significantly lower (1000-fold) than that of the euthyroid rats. Similarly, in vitro presence of supraphysiologic levels of l-thyroxine in the culture media of Vero cells decreased virus infectivity. Interestingly, hypothyroid animals showed a significant increase (10-fold) in spleen viral load as compared to that of their euthyroid counterparts.

CONCLUSIONS

These data clearly show that the HSV-1 infectivity is affected by THs, and suggest that THs or their analogs may have a potential application in prevention and/or treatment of viral infections.

Cancer Cell Gene Expression Modulated from Plasma Membrane Integrin αvβ3 by Thyroid Hormone and Nanoparticulate Tetrac

Integrin αvβ3 is generously expressed by cancer cells and rapidly dividing endothelial cells. The principal ligands of the integrin are extracellular matrix proteins, but we have described a cell surface small molecule receptor on αvβ3 that specifically binds thyroid hormone and thyroid hormone analogs. From this receptor, thyroid hormone (l-thyroxine, T4; 3,5,3'-triiodo-l-thyronine, T3) and tetraiodothyroacetic acid (tetrac) regulate expression of specific genes by a mechanism that is initiated non-genomically. At the integrin, T4 and T3 at physiological concentrations are pro-angiogenic by multiple mechanisms that include gene expression, and T4 supports tumor cell proliferation. Tetrac blocks the transcriptional activities directed by T4 and T3 at αvβ3, but, independently of T4 and T3, tetrac modulates transcription of cancer cell genes that are important to cell survival pathways, control of the cell cycle, angiogenesis, apoptosis, cell export of chemotherapeutic agents, and repair of double-strand DNA breaks. We have covalently bound tetrac to a 200 nm biodegradable nanoparticle that prohibits cell entry of tetrac and limits its action to the hormone receptor on the extracellular domain of plasma membrane αvβ3. This reformulation has greater potency than unmodified tetrac at the integrin and affects a broader range of cancer-relevant genes. In addition to these actions on intra-cellular kinase-mediated regulation of gene expression, hormone analogs at αvβ3 have additional effects on intra-cellular protein-trafficking (cytosol compartment to nucleus), nucleoprotein phosphorylation, and generation of nuclear coactivator complexes that are relevant to traditional genomic actions of T3. Thus, previously unrecognized cell surface-initiated actions of thyroid hormone and tetrac formulations at αvβ3 offer opportunities to regulate angiogenesis and multiple aspects of cancer cell behavior.