Thyroid hormone receptor α in breast cancer: prognostic and therapeutic implications

The Significance of Thyroid Hormone Receptors in Breast Cancer: A Hypothesis-Generating Narrative Review

BACKGROUND

Breast cancer (BC) is frequently diagnosed among Canadian women. While targeted therapies are available for most BC patients; treatment resistance is common and novel therapeutic targets are of interest. Thyroid hormones (TH) bound to thyroid hormone receptors (THR) influence cell proliferation and differentiation; they are also involved in the growth and development of normal breast tissue. Evidence suggests that THRβ is a tumor suppressor in various solid tumors.

PURPOSE

This narrative review discusses retrospective studies regarding the clinical relevance of THRβ as a potential prognostic biomarker and therapeutic target in BC.

METHODS

We consulted with an information specialist to develop a search strategy to find all literature related to THRα expression as a potential prognostic and therapeutic biomarker in breast cancer. The primary search was developed for Medline and translated to Embase. The searches were conducted on the Ovid platform on 18 August 2023.

RESULTS

Across seven retrospective studies identified, several have shown an association between higher THRβ1 expression with a lower risk of BC recurrence and with longer overall survival.

CONCLUSIONS

Some evidence suggests that THRβ expression is associated with a lower risk of BC recurrence and death. Validation of THRβ as an independent prognostic biomarker and possible predictive biomarker of response to endocrine therapy and/or chemotherapy is of interest. Given that THRβ is upstream of the AKT/PI3K pathway, its potential as a predictive biomarker of response to AKT inhibitors and/or PI3K inhibitors may also be of value. Finally, the potential re-purposing of THRβ agonists as anti-cancer agents warrants investigation.

Cytoplasmic Localization of Thyroid Hormone Receptor (TR) Alpha and Nuclear Expression of Its Isoform TRα2 Determine Survival in Breast Cancer in Opposite Ways

The aim of this retrospective study was to assess the respective prognostic values of cytoplasmic and nuclear TRα, TRα1, and TRα2 expression in breast cancer (BC) tissue samples and correlate the results with clinico-pathological parameters. In 249 BC patients, the expression patterns of general TRα and the α1 and α2 isoforms were evaluated via immuno-histochemistry. Prognosis-determining aspects were calculated via univariate, as well as multivariate, analysis. Univariate Cox-regression analysis revealed no association between nuclear TRα expression and overall survival (OS) (p = 0.126), whereas cytoplasmic TRα expression was significantly correlated with a poor outcome for both OS (p = 0.034) and ten-year survival (p = 0.009). Strengthening these results, cytoplasmic TRα was found to be an independent marker of OS (p = 0.010) when adjusted to fit clinico-pathological parameters. Analyses of the TRα-subgroups revealed that TRα1 had no prognostic relevance, whereas nuclear TRα2 expression was positively associated with OS (p = 0.014), ten-year survival (p = 0.029), and DFS (p = 0.043). Additionally, nuclear TRα2 expression was found to be an independent positive prognosticator (p = 0.030) when adjusted to fit clinico-pathological parameters. Overall, our results support the hypothesis that subcellular localization of TRα and its isoforms plays an important role in the carcinogenesis and prognosis of breast cancer. Cytoplasmic TRα expression correlates with more aggressive disease progression, whereas nuclear TRα2 expression appears to be a protective factor. These data may help us to prioritize high-risk BC subgroups for possible targeted tumor therapy.

Links between Breast and Thyroid Cancer: Hormones, Genetic Susceptibility and Medical Interventions

Breast and thyroid glands are two common sites of female malignancies. Since the late 19th century, physicians have found that the cancers in either thyroid or mammary gland might increase the risk of second primary cancers in the other site. From then on, many observational clinical studies have confirmed the hypothesis and more than one theory has been developed to explain the phenomenon. Since the two glands both have secretory functions and are regulated by the hypothalamic-pituitary axis, they may share some common oncogenic molecular pathways. However, other risks factors, including medical interventions and hormones, are also observed to play a role. This article aims to provide a comprehensive review of the associations between the two cancers. The putative mechanisms, such as hormone alteration, autoimmune attack, genetic predisposition and other life-related factors are reviewed and discussed. Medical interventions, such as chemotherapy and radiotherapy, can also increase the risk of second primary cancers. This review will provide novel insights into the research designs, clinical managements and treatments of thyroid and breast cancer patients.

Thyroid hormones act as modulators of inflammation through their nuclear receptors

Reciprocal crosstalk between endocrine and immune systems has been well-documented both in physiological and pathological conditions, although the connection between the immune system and thyroid hormones (THs) remains largely unclear. Inflammation and infection are two important processes modulated by the immune system, which have profound effects on both central and peripheral THs metabolism. Conversely, optimal levels of THs are necessary for the maintenance of immune function and response. Although some effects of THs are mediated by their binding to cell membrane integrin receptors, triggering a non-genomic response, most of the actions of these hormones involve their binding to specific nuclear thyroid receptors (TRs), which generate a genomic response by modulating the activity of a great variety of transcription factors. In this special review on THs role in health and disease, we highlight the relevance of these hormones in the molecular mechanisms linked to inflammation upon their binding to specific nuclear receptors. In particular, we focus on THs effects on different signaling pathways involved in the inflammation associated with various infectious and/or pathological processes, emphasizing those mediated by NF-kB, p38MAPK and JAK/STAT. The findings showed in this review suggest new opportunities to improve current therapeutic strategies for the treatment of inflammation associated with several infections and/or diseases, such as cancer, sepsis or Covid-19 infection.

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.

TRα2—An Untuned Second Fiddle or Fine-Tuning Thyroid Hormone Action?

Thyroid hormones (THs) control a wide range of physiological functions essential for metabolism, growth, and differentiation. On a molecular level, TH action is exerted by nuclear receptors (TRs), which function as ligand-dependent transcription factors. Among several TR isoforms, the function of TRα2 remains poorly understood as it is a splice variant of TRα with an altered C-terminus that is unable to bind T3. This review highlights the molecular characteristics of TRα2, proposed mechanisms that regulate alternative splicing and indications pointing towards an antagonistic function of this TR isoform in vitro and in vivo. Moreover, remaining knowledge gaps and major challenges that complicate TRα2 characterization, as well as future strategies to fully uncover its physiological relevance, are discussed.

Targeting Thyroid Hormone/Thyroid Hormone Receptor Axis: An Attractive Therapy Strategy in Liver Diseases

Thyroid hormone/thyroid hormone receptor (TH/TR) axis is characterized by TH with the assistance of plasma membrane transporters to combine with TR and mediate biological activities. Growing evidence suggests that TH/TR participates in plenty of hepatic metabolism. Thus, this review focuses on the role of the TH/TR axis in the liver diseases. To be specific, the TH/TR axis may improve metabolic-associated fatty liver disease, hepatitis, liver fibrosis, and liver injury while exacerbating the progression of acute liver failure and alcoholic liver disease. Also, the TH/TR axis has paradoxical roles in hepatocellular carcinoma. The TH/TR axis may be a prospecting target to cure hepatic diseases.

Structured reporting to improve transparency of analyses in prognostic marker studies

BACKGROUND

Factors contributing to the lack of understanding of research studies include poor reporting practices, such as selective reporting of statistically significant findings or insufficient methodological details. Systematic reviews have shown that prognostic factor studies continue to be poorly reported, even for important aspects, such as the effective sample size. The REMARK reporting guidelines support researchers in reporting key aspects of tumor marker prognostic studies. The REMARK profile was proposed to augment these guidelines to aid in structured reporting with an emphasis on including all aspects of analyses conducted.

METHODS

A systematic search of prognostic factor studies was conducted, and fifteen studies published in 2015 were selected, three from each of five oncology journals. A paper was eligible for selection if it included survival outcomes and multivariable models were used in the statistical analyses. For each study, we summarized the key information in a REMARK profile consisting of details about the patient population with available variables and follow-up data, and a list of all analyses conducted.

RESULTS

Structured profiles allow an easy assessment if reporting of a study only has weaknesses or if it is poor because many relevant details are missing. Studies had incomplete reporting of exclusion of patients, missing information about the number of events, or lacked details about statistical analyses, e.g., subgroup analyses in small populations without any information about the number of events. Profiles exhibit severe weaknesses in the reporting of more than 50% of the studies. The quality of analyses was not assessed, but some profiles exhibit several deficits at a glance.

CONCLUSIONS

A substantial part of prognostic factor studies is poorly reported and analyzed, with severe consequences for related systematic reviews and meta-analyses. We consider inadequate reporting of single studies as one of the most important reasons that the clinical relevance of most markers is still unclear after years of research and dozens of publications. We conclude that structured reporting is an important step to improve the quality of prognostic marker research and discuss its role in the context of selective reporting, meta-analysis, study registration, predefined statistical analysis plans, and improvement of marker research.

The TSH/Thyroid Hormones Axis and Breast Cancer

Breast cancer, the most prevalent female carcinoma, is characterized by the expression of steroid nuclear receptors in a subset of cases. The most important nuclear receptor with prognostic and therapeutic implications is the Estrogen Receptor (ER), which is expressed in about three out of four breast cancers. The Progesterone Receptor (PR) and the Androgen Receptor (AR) are also commonly expressed. Moreover, non-steroid nuclear receptors, including the vitamin D receptor (VDR) and the thyroid receptors (TRs), are also present in breast cancers and have pathophysiologic implications. Circulating thyroid hormones may influence breast cancer risk and breast cancer cell survival, through ligating their canonical receptors TRα and TRβ but also through additional membrane receptors that are expressed in breast cancer. The expression of TR subtypes and their respective isotypes have diverse effects in breast cancers through co-operation with ER and influence on other cancer-associated pathways. Other components of the TSH/thyroid hormone axis, such as TSH and selenoiodinase enzymes, have putative effects in breast cancer pathophysiology. This paper reviews the pathophysiologic and prognostic implications of the thyroid axis in breast cancer and provides a brief therapeutic perspective.

Low thyroid hormone receptor alpha-2 (THRα-2) tumor expression is associated with unfavorable tumor characteristics and high breast cancer mortality

Background

The active thyroid hormone triiodothyronine (T3) has been found to have an estrogen-like effect on breast cancer cells. Thyroid hormone receptor alpha-2 (THRα-2) acts as an antagonist for triiodothyronine (T3) signaling, and a low expression has been associated with unfavorable tumor characteristics and a higher mortality in breast cancer. However, the evidence are not conclusive. The present study evaluates tumor-specific THRα-2 expression in invasive breast cancers and its association with tumor characteristics and long-term mortality in a large population.

Method

The Malmö Diet and Cancer Study (MDCS), a population-based cohort in Sweden that included 17,035 women from 1991 to 1996, was used. Women diagnosed with breast cancer during 1991–2010 were eligible for inclusion. A tissue micro array was constructed from stored tumor material and stained for THRα-2 using immunohistochemistry. Tumors from 654 patients were scored regarding the intensity and the fraction of cells stained, then dichotomized into low or high expression. Date and cause of death were collected up until 2018-12-31. Tumor- and patient characteristics were available from the MDCS. Missing data was imputed using chained equations. Logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals (CIs) for low vs high expression of THRα-2 related to specific tumor factors. Mortality was evaluated with Kaplan–Meier curves and Cox regression, rendering hazard ratios (HRs). Analyses were also stratified for estrogen receptor (ER) status.

Results

We found strong evidence of an association between low THRα-2 and unfavorable tumor characteristics, including estrogen receptor negativity: OR 4.04 (95% CI 2.28–7.15) and tumor size > 20–50 mm: OR 2.20 (95% CI 1.39–3.49). We found evidence of increased breast cancer-specific mortality for women with low THRα-2, HR 1.38 (95% CI 0.96–1.99), which remained after adjusting for age at diagnosis, HR 1.48 (95% CI 1.03–2.14), but not after adjusting for relevant prognostic factors, HR 0.98 (95% CI 0.66–1.45). THRα-2 expression in ER-negative tumors had an inverse correlation with overall mortality, HR 0.27 (95% CI 0.11–0.65).

Conclusion

Low tumor-specific THRα-2 expression was in this study associated with prognostically unfavorable tumor characteristics and a higher mortality in breast cancer, but not independent from other prognostic factors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-021-01496-7.

Control of Breast Cancer Pathogenesis by Histone Methylation and the Hairless Histone Demethylase

Breast cancer is a highly heterogeneous disease, encompassing many subtypes that have distinct origins, behaviors, and prognoses. Although traditionally seen as a genetic disease, breast cancer is now also known to involve epigenetic abnormalities. Epigenetic regulators, such as DNA methyltransferases and histone-modifying enzymes, play essential roles in gene regulation and cancer development. Dysregulation of epigenetic regulator activity has been causally linked with breast cancer pathogenesis. Hairless (HR) encodes a 130-kDa transcription factor that is essential for development and tissue homeostasis. Its role in transcription regulation is partly mediated by its interaction with multiple nuclear receptors, including thyroid hormone receptor, retinoic acid receptor-related orphan receptors, and vitamin D receptor. HR has been studied primarily in epidermal development and homeostasis. Hr-mutant mice are highly susceptible to ultraviolet- or carcinogen-induced skin tumors. Besides its putative tumor suppressor function in skin, loss of HR function has also been implicated in increased leukemia susceptibility and promotes the growth of melanoma and brain cancer cells. HR has also been demonstrated to function as a histone H3 lysine 9 demethylase. Recent genomics studies have identified HR mutations in a variety of human cancers, including breast cancer. The anticancer function and mechanism of action by HR in mammary tissue remains to be investigated. Here, we review the emerging role of HR, its histone demethylase activity and histone methylation in breast cancer development, and potential for epigenetic therapy.

Thyroid hormone and thyroid hormone nuclear receptors: History and present state of art

The present review traces the road leading to discovery of L-thyroxine, thyroid hormone (3,5,3´-triiodo-L-thyronine, T₃) and its cognate nuclear receptors. Thyroid hormone is a pleio-tropic regulator of growth, differentiation, and tissue homeostasis in higher organisms. The major site of the thyroid hormone action is predominantly a cell nucleus. T₃ specific binding sites in the cell nuclei have opened a new era in the field of the thyroid hormone receptors (TRs) discovery. T₃ actions are mediated by high affinity nuclear TRs, TRalpha and TRbeta, which function as T₃-activated transcription factors playing an essential role as transcription-modulating proteins affecting the transcriptional responses in target genes. Discovery and characterization of nuclear retinoid X receptors (RXRs), which form with TRs a heterodimer RXR/TR, positioned RXRs at the epicenter of molecular endocrinology. Transcriptional control via nuclear RXR/TR heterodimer represents a direct action of thyroid hormone. T₃ plays a crucial role in the development of brain, it exerts significant effects on the cardiovascular system, skeletal muscle contractile function, bone development and growth, both female and male reproductive systems, and skin. It plays an important role in maintaining the hepatic, kidney and intestine homeostasis and in pancreas, it stimulates the beta-cell proliferation and survival. The TRs cross-talk with other signaling pathways intensifies the T₃ action at cellular level. The role of thyroid hormone in human cancers, acting via its cognate nuclear receptors, has not been fully elucidated yet. This review is aimed to describe the history of T₃ receptors, starting from discovery of T3 binding sites in the cell nuclei to revelation of T₃ receptors as T₃-inducible transcription factors in relation to T₃ action at cellular level. It also focuses on milestones of investigation, comprising RXR/TR dimerization, cross-talk between T₃ receptors, and other regulatory pathways within the cell and mainly on genomic action of T₃. This review also focuses on novel directions of investigation on relationships between T₃ receptors and cancer. Based on the update of available literature and the author's experimental experience, it is devoted to clinicians and medical students.

Thyroid hormone receptor α1 acts as a new squamous cell lung cancer diagnostic marker and poor prognosis predictor

Lung cancer is considered the major cause of cancer-related deaths worldwide. Unfortunately, all chemotherapy regimens used in lung cancer treatment showed nearly the same efficacy. Finding a new therapeutic target that can be used as an alternative after the failure of or in association with chemotherapy to improve the prognosis is an urgent demand. Up to date, it is Known that thyroid hormones (THs) and Thyroid hormone receptors (THRs) control the progression of several types of tumours. Nevertheless, their role in non-small cell lung cancer (NSCLC) is unknown. This study investigated the expression of THRα1 in NSCLC cases and its correlation to tumour clinicopathological parameters to shed new light on the relevance of THRα1 in lung cancer. Immunohistochemistry utilizing THRα1 antibody was performed on tissue sections obtained from 80 patients diagnosed with NSCLC. We also investigated the expression of THRα gene in Microarrays of lung squamous cell carcinoma (SCC) and adenocarcinoma (AC) patients by using GEO data sets on https://www.ncbi.nlm.nih.gov . We showed, for the first time, the expression of THRα1 in NSCLC. Intermediate and high THRα1 expressions were detected in (25% and 66.7%) of SCC cases respectively. High THRα1 expression was associated with shorter OS. On the other hand, 86.7% of AC cases revealed low THRα1 expression. Inflammatory cells in SCC cases showed high THRα1 expression. By analysing GEO data sets, a significant increase in THRα gene expression was found in SCC compared to AC cases. Our study underscores the possibility of using THRα1 expression not only as a prognostic marker, but also as an innovative diagnostic additive tool for lung SCC, which could be tested as a potential therapeutic target for SCC in the future.

Relationship of ITPKA expression with the prognosis of breast cancer

BACKGROUND

Breast cancer (BC) represents a most common cancer among women worldwide. The outcomes of this disease remain dismal due to frequent recurrence and metastasis. Inositol-1,4,5-trisphosphate-3-kinase-A (ITPKA) plays an important role in regulating calcium signaling and actin dynamics. The dysregulation of ITPKA has been observed in several human cancers. The present study aimed to assess ITPKA expression and its prognostic value in BC.

METHODS

ITPKA expression was examined via quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC) methods. In addition, Kaplan-Meier survival analysis and Cox regression analysis were performed to evaluate prognostic value of ITPKA in BC.

RESULTS

Upregulated ITPKA expression was found in BC samples, according to both qRT-PCR and IHC analyses (all p < .05). ITPKA expression was positively correlated with lymph node metastasis (p = .021) and TNM stage (p = .009). Moreover, BC patients with high expression of ITPKA had poor overall survival compared with those with low expression (log-rank p < .05). Cox analysis verified that ITPKA expression was an independent prognostic factor for BC patients (HR = 4.239, 95%CI = 2.221-8.093 and p = .000).

CONCLUSION

BC cases show increased expression of ITPKA. ITPKA may act as an independent prognostic biomarker in BC.

Increased expression of thyroid hormone receptor alpha and estrogen receptor alpha in breast cancer associated with thyroid cancer

INTRODUCTION

Breast cancer co-occurred with thyroid cancer might be associated with thyroid hormone receptor (TR) and estrogen receptor (ER), but few have been reported. We aimed to investigate the expression and prognostic significance of ERs and TRs in such settings.

MATERIAL AND METHODS

Tissue microarrays were constructed from 75 patients with breast and thyroid cancer (BC + TC) who were retrospectively recruited between 1999 and 2012 and 147 with breast cancer only (BC controls). The ERα, ERβ, TRα, and TRβ expression levels were analyzed by immunohistochemistry.

RESULTS

TRα expression was more frequently observed in the BC + TC group than the BC control group both in the normal (51.5% vs 23.3%, respectively, p = 0.009) and cancer tissues (21.6% vs 6.8%, respectively, p = 0.001). The BC + TC group showed greater ERα-positivity in the cancer tissues (79.7% vs 58.7%, respectively, p = 0.002) than the BC control group. The degree of ERα- and TRα-positivity was unchanged by radioactive treatment or serum thyroid stimulating hormone levels. In the BC + TC group, ERα-positivity was associated with earlier disease stage I/IIA (81.0% vs 50.0%; p = 0.031) and lower recurrence rates (8.5% vs 40.0%; p = 0.002). TRα-positivity alone was not associated with any recurrence-free survival-related differences, and ERα- and TRα-negativity were associated with significantly shorter recurrence-free survival (p < 0.001).

CONCLUSION

Enhanced ERα and TRα expression in breast cancer is associated with thyroid cancer occurrence, and the observed association with prognosis suggests the possible role of ERs and TRs in the link between breast cancer and thyroid cancer.

The Prognostic Impact of Retinoid X Receptor and Thyroid Hormone Receptor alpha in Unifocal vs. Multifocal/Multicentric Breast Cancer

The aim of this study was to assess the prognostic value of the steroid hormone receptor expression, counting the retinoid X receptor (RXR) and thyroid hormone receptors (THRs), on the two different breast cancer (BC) entities: multifocal/multicentric versus unifocal. The overall and disease-free survival were considered as the prognosis determining aspects and analyzed by uni- and multi-variate analysis. Furthermore, histopathological grading and TNM staging (T = tumor size, N = lymph node involvement, M = distant metastasis) were examined in relation to RXR and THRs expression. A retrospective statistical analysis was carried out on survival-related events in a series of 319 sporadic BC patients treated at the Department of Gynecology and Obstetrics at the Ludwig-Maximillian's University in Munich between 2000 and 2002. The expression of RXR and THRs, including its two major isoforms THRα1 and THRα2, was analyzed by immunohistochemistry and showed to have a significant correlation for both BC entities in regard to survival analysis. Patients with multifocal/multicentric BC were exposed to a significantly worse disease-free survival (DFS) when expressing RXR. Patients with unifocal BC showed a significantly worse DFS when expressing THRα1. In contrast, a statistically significant positive association between THRα2 expression and enhanced DFS in multifocal/multicentric BC was shown. Especially the RXR expression in multifocal/multicentric BC was found to play a remarkably contradictory role for BC prognosis. The findings imply the need for a critical review of possible molecular therapies targeting steroid hormone receptors in BC treatment. Our results strengthen the need to further investigate the behavior of the nuclear receptor family, especially in relation to BC focality.

Nuclear receptors: Lipid and hormone sensors with essential roles in the control of cancer development

Nuclear receptors (NRs) are a superfamily of ligand-activated transcription factors that act as biological sensors and use a combination of mechanisms to modulate positively and negatively gene expression in a spatial and temporal manner. The highly orchestrated biological actions of several NRs influence the proliferation, differentiation, and apoptosis of many different cell types. Synthetic ligands for several NRs have been the focus of extensive drug discovery efforts for cancer intervention. This review summarizes the roles in tumour growth and metastasis of several relevant NR family members, namely androgen receptor (AR), estrogen receptor (ER), glucocorticoid receptor (GR), thyroid hormone receptor (TR), retinoic acid receptors (RARs), retinoid X receptors (RXRs), peroxisome proliferator-activated receptors (PPARs), and liver X receptors (LXRs). These studies are key to develop improved therapeutic agents based on novel modes of action with reduced side effects and overcoming resistance.

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.

Prediagnostic serum selenium levels in relation to breast cancer survival and tumor characteristics

Women with lower levels of serum selenium (Se) may have a worse survival in breast cancer than women with higher levels, despite no difference in incidence of the disease. Our study was conducted to test whether Se is associated with the aggressiveness of breast tumors. Both the risk of having a tumor characteristic associated with worse prognosis, as well as the overall and breast cancer-specific mortality, were studied. We identified breast cancer cases and controls within the Malmö Diet and Cancer Study, a population-based cohort with 17 035 women recruited between 1991 and 1996. Inclusion criteria were incident breast cancer. Exclusion criteria were carcinoma in situ and bilateral breast cancer. Controls were selected among breast cancer-free women both from matching (n = 694) as well as randomization (n = 492). After exclusion, 1066 cases remained and were compared to controls regarding their prediagnostic serum Se levels and subsequent risk of having a certain tumor characteristic or intrinsic subtype. We also followed breast cancer patients regarding overall and breast cancer-specific mortality, comparing different Se quartiles. No association between serum Se quartile and any tumor characteristic or intrinsic subtype was found. Lower overall mortality was found among women in the highest Se quartile compared to the lowest using an adjusted Cox proportional hazards model, hazard ratio 0.63 (95% confidence interval: 0.44-0.89). Similar results were seen for breast cancer-specific mortality, 0.60 (0.37-0.98). The results of our study support that Se is associated with a lower mortality in breast cancer, not related to established prognostic factors.

Cytoplasmic and Nuclear Forms of Thyroid Hormone Receptor β1 Are Inversely Associated with Survival in Primary Breast Cancer

The aim of this study was to investigate the expression of thyroid hormone receptor β1 (THRβ1) by immunohistochemistry in breast cancer (BC) tissues and to correlate the results with clinico-biological parameters. In a well-characterized cohort of 274 primary BC patients, THRβ1 was widely expressed with a predominant nuclear location, although cytoplasmic staining was also frequently observed. Both nuclear and cytoplasmic THRβ1 were correlated with high-risk BC markers such as human epidermal growth factor receptor 2 (HER2), Ki67 (also known as MKI67), prominin-1 (CD133), and N-cadherin. Overall survival analysis demonstrated that cytoplasmic THRβ1 was correlated with favourable survival (p = 0.015), whereas nuclear THRβ1 had a statistically significant correlation with poor outcome (p = 0.038). Interestingly, in our cohort, nuclear and cytoplasmic THRβ1 appeared to be independent markers either for poor (p = 0.0004) or for good (p = 0.048) prognosis, respectively. Altogether, these data indicate that the subcellular expression of THRβ1 may play an important role in oncogenesis. Moreover, the expression of nuclear THRβ1 is a negative outcome marker, which may help to identify high-risk BC subgroups.

The Thyroid Hormone Receptor-RUNX2 Axis: A Novel Tumor Suppressive Pathway in Breast Cancer

Metastatic breast cancer is refractory to conventional therapies and is an end-stage disease. RUNX2 is a transcription factor that becomes oncogenic when aberrantly expressed in multiple tumor types, including breast cancer, supporting tumor progression and metastases. Our previous work demonstrated that the thyroid hormone receptor beta (TRβ) inhibits RUNX2 expression and tumorigenic characteristics in thyroid cells. As TRβ is a tumor suppressor, we investigated the compelling question whether TRβ also regulates RUNX2 in breast cancer. The Cancer Genome Atlas indicates that TRβ expression is decreased in the most aggressive basal-like subtype of breast cancer. We established that modulated levels of TRβ results in corresponding changes in the high levels of RUNX2 expression in metastatic, basal-like breast cells. The MDA-MB-231 triple-negative breast cancer cell line exhibits low expression of TRβ and high levels of RUNX2. Increased expression of TRβ decreased RUNX2 levels. The thyroid hormone-mediated suppression of RUNX2 is TRβ specific as TRα overexpression failed to alter RUNX2 expression. Consistent with these findings, knockdown of TRβ in non-tumor MCF10A mammary epithelial-like cells results in an increase in RUNX2 and RUNX2 target genes. Mechanistically, TRβ directly interacts with the proximal promoter of RUNX2 through a thyroid hormone response element to reduce promoter activity. The TRβ suppression of the oncogene RUNX2 is a signaling pathway shared by thyroid and breast cancers. Our findings provide a novel mechanism for TRβ-mediated tumor suppression in breast cancers. This pathway may be common to many solid tumors and impact treatment for metastatic cancers.

Association between benign thyroid disease and breast cancer: a single center experience

BACKGROUND

The relationship between breast cancer (BC) and thyroid disease (TD) is still controversial. The aim of the study was to investigate the possible coexistence of TD in patients with newly diagnosed BC and its correlation with BC clinical presentation with regard to menopausal status and stage of disease.

METHODS

This is a retrospective cohort study of all patients treated for primary BC between 2014 and 2016 at the Breast Unit of Trieste University Hospital. Clinical charts and reports were reviewed for coexisting thyroid disorders (i.e. hyperthyroidism, hypothyroidism, benign TD, thyroid cancer, thyroid autoimmunity) and menopausal status at the time of BC diagnosis. Biomolecular profile, stage, and grading of BC were also evaluated.

RESULTS

A total of 786 women and 7 men were included in the study. Co-presence of TD was found in 161(20.3%) cases: of these, 151(19.4%) patients presented benign TD and 10(1.3%) patients presented thyroid carcinoma. Thyroid autoimmunity was found in 51(32%) patients. Regarding thyroid function, 88(55%) patients had hypothyroidism, 19(12%) hyperthyroidism, and 54(33%) normal thyroid function. No statistically significant correlation was found between age and TD (p = 0.16), although TD was more common in women aged ≥60 years. Women with BC diagnosed at pre-menopausal age were more likely to have thyroid autoimmune diseases (45% vs. 29%, p = 0.05). No association was detected among BC molecular profiles with either thyroid autoimmunity (p = 0.26) or altered thyroid function (p = 0.63). High-grade BC was more frequent in women with hyperthyroidism (52.9%, p = 0.04), but the grading was independent from the presence of thyroid autoimmune disease (p = 0.87). BC stage was related to both thyroid autoimmunity (p = 0.04) and thyroid function (p < 0.001), with 55.2% of women affected by benign TD presenting with stage I BC and more aggressive BCs found in hypothyroid patients.

CONCLUSIONS

According our study results, patients with primary BC present a greater incidence of autoimmunity disorders, especially when diagnosed in the pre-menopausal setting. However, further prospective studies are required to definitively prove causality.

Molecular Functions of Thyroid Hormone Signaling in Regulation of Cancer Progression and Anti-Apoptosis

Several physiological processes, including cellular growth, embryonic development, differentiation, metabolism and proliferation, are modulated by genomic and nongenomic actions of thyroid hormones (TH). Several intracellular and extracellular candidate proteins are regulated by THs. 3,3,5-Triiodo-L-thyronine (T₃) can interact with nuclear thyroid hormone receptors (TR) to modulate transcriptional activities via thyroid hormone response elements (TRE) in the regulatory regions of target genes or bind receptor molecules showing no structural homology to TRs, such as the cell surface receptor site on integrin αvβ3. Additionally, L-thyroxine (T₄) binding to integrin αvβ3 is reported to induce gene expression through initiating non-genomic actions, further influencing angiogenesis and cell proliferation. Notably, thyroid hormones not only regulate the physiological processes of normal cells but also stimulate cancer cell proliferation via dysregulation of molecular and signaling pathways. Clinical hypothyroidism is associated with delayed cancer growth. Conversely, hyperthyroidism is correlated with cancer prevalence in various tumor types, including breast, thyroid, lung, brain, liver and colorectal cancer. In specific types of cancer, both nuclear thyroid hormone receptor isoforms and those on the extracellular domain of integrin αvβ3 are high risk factors and considered potential therapeutic targets. In addition, thyroid hormone analogs showing substantial thyromimetic activity, including triiodothyroacetic acid (Triac), an acetic acid metabolite of T₃, and tetraiodothyroacetic acid (Tetrac), a derivative of T₄, have been shown to reduce risk of cancer progression, enhance therapeutic effects and suppress cancer recurrence. Here, we have reviewed recent studies focusing on the roles of THs and TRs in five cancer types and further discussed the potential therapeutic applications and underlying molecular mechanisms of THs.

Gestational and Lactational Exposure to an Environmentally Relevant Mixture of Brominated Flame Retardants Downregulates Junctional Proteins, Thyroid Hormone Receptor α1 Expression, and the Proliferation-Apoptosis Balance in Mammary Glands Post Puberty

Mammary gland development requires hormonal regulation during puberty, pregnancy, and lactation. Brominated flame retardants (BFRs) are endocrine disruptors; they are added to consumer products to satisfy flammability standards. Previously, we showed that gestational and lactational exposure to an environmentally relevant mixture of BFRs disrupts proteins of the adherens junctions in rat dam mammary glands at weaning. Here, we hypothesize that perinatal exposure to the same BFR mixture also disrupts junctional proteins and signaling pathways controlling mammary gland development in pups. Dams were exposed through diet to a BFR mixture based on the substances in house dust; doses of the mixture used were 0, 0.06, 20, or 60 mg/kg/day. Dams were exposed continuously beginning prior to mating until pups' weaning; female offspring were euthanized on postnatal day (PND) 21, 46, and 208. The lowest dose of BFRs significantly downregulated adherens junction proteins, E-cadherin, and β-catenin, and the gap junction protein p-Cx43, as well as thyroid hormone receptor alpha 1 protein at PND 46. No effects were observed on estrogen or progesterone receptors. The low dose also resulted in a decrease in cleaved caspase-3, a downward trend in PARP levels, proteins involved in apoptosis, and an upward trend in proliferating cell nuclear antigen, a marker of proliferation. No effects were observed on ductal elongation or on the numbers of terminal end buds. Together, our results indicate that gestational and lactational exposure to an environmentally relevant mixture of BFRs disrupts cell-cell interactions, thyroid hormone homeostasis and the proliferation-apoptosis balance at PND 46, a critical stage for mammary gland development.

Higher order genomic organization and epigenetic control maintain cellular identity and prevent breast cancer

Cells establish and sustain structural and functional integrity of the genome to support cellular identity and prevent malignant transformation. In this review, we present a strategic overview of epigenetic regulatory mechanisms including histone modifications and higher order chromatin organization (HCO) that are perturbed in breast cancer onset and progression. Implications for dysfunctions that occur in hormone regulation, cell cycle control, and mitotic bookmarking in breast cancer are considered, with an emphasis on epithelial-to-mesenchymal transition and cancer stem cell activities. The architectural organization of regulatory machinery is addressed within the contexts of translating cancer-compromised genomic organization to advances in breast cancer risk assessment, diagnosis, prognosis, and identification of novel therapeutic targets with high specificity and minimal off target effects.

The Antiarrhythmic Drug, Dronedarone, Demonstrates Cytotoxic Effects in Breast Cancer Independent of Thyroid Hormone Receptor Alpha 1 (THRα1) Antagonism

Previous research has suggested that thyroid hormone receptor alpha 1 (THRα1), a hormone responsive splice variant, may play a role in breast cancer progression. Whether THRα1 can be exploited for anti-cancer therapy is unknown. The antiproliferative and antitumor effects of dronedarone, an FDA-approved anti-arrhythmic drug which has been shown to antagonize THRα1, was evaluated in breast cancer cell lines in vitro and in vivo. The THRα1 splice variant and the entire receptor, THRα, were also independently targeted using siRNA to determine the effect of target knockdown in vitro. In our study, dronedarone demonstrates cytotoxic effects in vitro and in vivo in breast cancer cell lines at doses and concentrations that may be clinically relevant. However, knockdown of either THRα1 or THRα did not cause substantial anti-proliferative or cytotoxic effects in vitro, nor did it alter the sensitivity to dronedarone. Thus, we conclude that dronedarone’s cytotoxic effect in breast cancer cell lines are independent of THRα or THRα1 antagonism. Further, the depletion of THRα or THRα1 does not affect cell viability or proliferation. Characterizing the mechanism of dronedarone’s anti-tumor action may facilitate drug repurposing or the development of new anti-cancer agents.

Overexpression of HDAC9 is associated with poor prognosis and tumor progression of breast cancer in Chinese females

BACKGROUND

Breast cancer represents a serious health issue among females. HDAC9 has been identified as an oncogene in human cancers. This study sought to assess the prognostic value and the biologic function of HDAC9 in breast cancer patients.

METHODS

Expression of HDAC9 in breast cancer tissues and cells was evaluated by quantitative real-time polymerase chain reaction. Kaplan-Meier survival analysis and Cox regression assay were conducted to explore the prognostic significance of HDAC9. Cell experiments were performed to investigate the effects of HDAC9 on the biologic behaviors of breast cancer cells.

RESULTS

Expression of HDAC9 was significantly upregulated in both cancerous tissues and cells compared with the normal controls (all P<0.05). Overexpression of HDAC9 was correlated with lymph node metastasis (P=0.021) and TNM stage (P=0.004). Patients with high HDAC9 had poor overall survival compared to those with low levels of HDAC9 (log-rank P<0.05). Elevated HDAC9 was found to be an independent prognostic factor for the patients (hazard ratio=2.996, 95% CI=1.611-5.572, P=0.001). According to the cell experiments, tumor cell proliferation, migration and invasion were suppressed by knockdown of HDAC9.

CONCLUSION

All data demonstrated that overexpression of HDAC9 serves as a prognostic biomarker and may be involved in the tumor progression of breast cancer.

Thyroid hormone receptor alpha (TRa) tissue expression in ductal invasive breast cancer: A study combining quantitative immunohistochemistry with digital slide image analysis

BACKGROUND

In breast cancer, hormonal receptors hold promise for developing novel targeted therapies. The thyroid exerts its actions via the thyroid hormone receptors alpha and beta. The clinical significance of the expression of thyroid hormone receptors in breast cancer is unclear.

MATERIAL AND METHODS

We studied thyroid hormone receptor alpha (TRa) expression in 82 samples from 41 women with ductal invasive breast cancer and no thyroid disease. We performed quantitative immunohistochemistry with digital image analysis and correlated TRa expression with clinicopathological parameters.

RESULTS

TRa was expressed in both normal breast epithelium and breast cancer, but expression in breast cancer was significantly lower. TRa was expressed significantly less in larger and grade III tumors. Conversely, breast cancers with lymphovascular invasion showed increased TRa expression compared to cancers without lymphovascular invasion. TRa expression was not significantly different between node-positive and node-negative breast cancers, or among different hormonal profiles and intrinsic subtypes.

DISCUSSION

This is the first-in-human study to combine quantitative immunohistochemistry with image analysis to study TRa expression in women with ductal invasive breast cancer and no clinical or biochemical evidence of thyroid dysfunction. We confirm that TRa is expressed in both normal and malignant breast epithelium and suggest that TRa expression is downregulated during breast carcinogenesis. Larger and higher grade breast cancers demonstrate partial loss in TRa expression. Alterations in TRa expression take place even in the absence of clinical or biochemical thyroid disease. The underlying mechanism of these findings and their potential significance in survival and relapse mandate further research.

The thyroid and breast cancer

PURPOSE OF REVIEW

The female predominance of diseases of the thyroid and breast makes difficult the separation of an expected association with a causal linkage. This review will examine recent reports on associations between thyroid disease and breast cancer, comparing them with previous studies, with a view to elucidating what pointers are available to suggest either a common pathogenesis or novel thyroid-related therapeutic approach, which might arise from this association.

RECENT FINDINGS

Reports on thyroid-breast cancer associations are reviewed under the following headings: breast cancer prevalence in different thyroid disorders and their effect on risk and outcome; the possible role of thyroid autoimmunity, thyroid enlargement, effect of radioactive iodine treatment, role of stable iodine, possible joint antigens sodium iodide transporter and thyroid peroxidase and thyroid-breast cancer coincidence.

SUMMARY

Current studies on thyroid and breast cancer associations confirm earlier findings of the lack of definitive evidence of a causal relationship. The predominant relationship continues to be hypothyroidism or autoimmune thyroid disease perhaps contributing to increased breast cancer risk or outcomes. However, despite many studies and the findings of meta-analyses, elucidating the mechanisms underlying the association remains elusive. At present, there is little justification for utilizing thyroid insights as a possible therapeutic intervention in breast cancer.