Research resource: nuclear receptors as transcriptome: discriminant and prognostic value in breast cancer

The multifaceted role of the mineralocorticoid receptor in cancers

The mineralocorticoid receptor (MR/NR3C2) is a member of the family of steroid receptors (SR) which also includes the estrogen receptor (ER), progesterone receptor (PR), androgen receptor (AR) and glucocorticoid receptor (GR). They function primarily as nuclear receptors to regulate gene expression. While the other steroid hormone receptors are known to play important roles in the pathogenesis and progression of many cancers, relatively little is understood about the role of MR in cancer biology. This review focuses on examining new insights into the potential roles and mechanisms of action of MR in cancers.

Exploring the role of trifarotene against RAR-α: an investigation of expression pattern and clinicopathological significance of RAR-α in breast cancer

Introduction

The members retinoic acid receptors (RARs) (α, β, and γ) and retinoid X receptors (RXRs) (α, β, and γ) belong to the retinoid receptor family. They regulate the biological action of classical retinoids through nuclear retinoid receptors, a transcription factor that is regulated by ligands. Through the binding of particular retinoic acid-responsive elements (RAREs) located in target gene promoters, RARs and members of the RXRs form heterodimers. By binding to its nuclear receptors and triggering the transcription of the target genes downstream, retinoic acid (RA) mediates the expression of certain genes. Retinoids so mainly control gene expression to carry out their biological actions. RARs are essential for many biological processes, such as development, immunity, reproduction, organogenesis, and homeostasis. Apart from their physiological functions, RARs are also linked to pathologies and tumors due to mutations, protein fusions, changes in expression levels, or abnormal post-translational changes that lead to aberrant functions and homeostasis breakdown. The oncogenic development of animal tissues or cultured cells is linked to altered expression of retinoid receptors. The RAR-α is over-expressed in several malignancies. Increased invasion and migration in several cancer forms, including HNSC carcinoma, pediatric low-grade gliomas, lung adenocarcinoma, and breast cancer, have been linked to its upregulated expression. Numerous approved therapeutic regimens targeting RAR-α have been developed, improving patient survival rates.

Objective

This study's main objective was to identify novel RAR-α-targeting drugs and evaluate the expression patterns of RAR-α in breast cancer patients.

Methodology

In-silico investigation using a variety of bioinformatics tools like UALCAN, TISCH, TIMER 2.0, ENRICHR, and others were employed to examine the expression of RAR-α. Further we evaluated in-silico inhibition of RAR-α with trifarotene and also tested the cytotoxicity of trifarotene in breast cancer cells.

Results

Our research indicates that RAR-α is upregulated in several malignancies including Breast Cancer. It regulates granulocyte differentiation and has an association with the retinoic acid receptor signaling pathway and cellular response to estrogen stimulus. Furthermore, trifarotene was found as a potential synthetic compound that targets RAR-α through in silico and in-vitro study.

Discussion

Overall, this research indicates that elevated expression of RAR-α enhances the onset of breast cancer. Using trifarotene medication to target RAR-α will significantly boost the response of breast cancer individuals to treatment and delay the development of resistance to drugs.

Immune-related gene methylation prognostic instrument for stratification and targeted treatment of ovarian cancer patients toward advanced 3PM approach

Background

DNA methylation is an important mechanism in epigenetics, which can change the transcription ability of genes and is closely related to the pathogenesis of ovarian cancer (OC). We hypothesize that DNA methylation is significantly different in OCs compared to controls. Specific DNA methylation status can be used as a biomarker of OC, and targeted drugs targeting these methylation patterns and DNA methyltransferase may have better therapeutic effects. Studying the key DNA methylation sites of immune-related genes (IRGs) in OC patients and studying the effects of these methylation sites on the immune microenvironment may provide a new method for further exploring the pathogenesis of OC, realizing early detection and effective monitoring of OC, identifying effective biomarkers of DNA methylation subtypes and drug targets, improving the efficacy of targeted drugs or overcoming drug resistance, and better applying it to predictive diagnosis, prevention, and personalized medicine (PPPM; 3PM) of OC.

Method

Hypermethylated subtypes (cluster 1) and hypomethylated subtypes (cluster 2) were established in OCs based on the abundance of different methylation sites in IRGs. The differences in immune score, immune checkpoints, immune cells, and overall survival were analyzed between different methylation subtypes in OC samples. The significant pathways, gene ontology (GO), and protein-protein interaction (PPI) network of the identified methylation sites in IRGs were enriched. In addition, the immune-related methylation signature was constructed with multiple regression analysis. A methylation site model based on IRGs was constructed and verified.

Results

A total of 120 IRGs with 142 differentially methylated sites (DMSs) were identified. The DMSs were clustered into a high-level methylation group (cluster 1) and a low-level methylation group (cluster 2). The significant pathways and GO analysis showed many immune-related and cancer-associated enrichments. A methylation site signature based on IRGs was constructed, including RORC|cg25112191, S100A13|cg14467840, TNF|cg04425624, RLN2|cg03679581, and IL1RL2|cg22797169. The methylation sites of all five genes showed hypomethylation in OC, and there were statistically significant differences among RORC|cg25112191, S100A13|cg14467840, and TNF|cg04425624 (p < 0.05). This prognostic model based on low-level methylation and high-level methylation groups was significantly linked to the immune microenvironment as well as overall survival in OC.

Conclusions

This study provided different methylation subtypes for OC patients according to the methylation sites of IRGs. In addition, it helps establish a relationship between methylation and the immune microenvironment, which showed specific differences in biological signaling pathways, genomic changes, and immune mechanisms within the two subgroups. These data provide ones to deeply understand the mechanism of immune-related methylation genes on the occurrence and development of OC. The methylation-site signature is also to establish new possibilities for OC therapy. These data are a precious resource for stratification and targeted treatment of OC patients toward an advanced 3PM approach.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-024-00359-3.

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.

Phase separation of Nur77 mediates XS561-induced apoptosis by promoting the formation of Nur77/Bcl-2 condensates

The orphan nuclear receptor Nur77 is a critical regulator of the survival and death of tumor cells. The pro-death effect of Nur77 can be regulated by its interaction with Bcl-2, resulting in conversion of Bcl-2 from a survival to killer. As Bcl-2 is overexpressed in various cancers preventing them from apoptosis and promoting their resistance to chemotherapy, targeting the apoptotic pathway of Nur77/Bcl-2 may lead to new cancer therapeutics. Here, we report our identification of XS561 as a novel Nur77 ligand that induces apoptosis of tumor cells by activating the Nur77/Bcl-2 pathway. In vitro and animal studies revealed an apoptotic effect of XS561 in a range of tumor cell lines including MDA-MB-231 triple-negative breast cancer (TNBC) and MCF-7/LCC2 tamoxifen-resistant breast cancer (TAMR) in a Nur77-dependent manner. Mechanistic studies showed XS561 potently induced the translocation of Nur77 from the nucleus to mitochondria, resulting in mitochondria-related apoptosis. Interestingly, XS561-induced accumulation of Nur77 at mitochondria was associated with XS561 induction of Nur77 phase separation and the formation of Nur77/Bcl-2 condensates. Together, our studies identify XS561 as a new activator of the Nur77/Bcl-2 apoptotic pathway and reveal a role of phase separation in mediating the apoptotic effect of Nur77 at mitochondria.

International Union of Basic and Clinical Pharmacology CXIII: Nuclear Receptor Superfamily-Update 2023

The NR superfamily comprises 48 transcription factors in humans that control a plethora of gene network programs involved in a wide range of physiologic processes. This review will summarize and discuss recent progress in NR biology and drug development derived from integrating various approaches, including biophysical techniques, structural studies, and translational investigation. We also highlight how defective NR signaling results in various diseases and disorders and how NRs can be targeted for therapeutic intervention via modulation via binding to synthetic lipophilic ligands. Furthermore, we also review recent studies that improved our understanding of NR structure and signaling. SIGNIFICANCE STATEMENT: Nuclear receptors (NRs) are ligand-regulated transcription factors that are critical regulators of myriad physiological processes. NRs serve as receptors for an array of drugs, and in this review, we provide an update on recent research into the roles of these drug targets.

Long-range gene regulation in hormone-dependent cancer

The human genome is organized into multiple structural layers, ranging from chromosome territories to progressively smaller substructures, such as topologically associating domains (TADs) and chromatin loops. These substructures, collectively referred to as long-range chromatin interactions (LRIs), have a significant role in regulating gene expression. TADs are regions of the genome that harbour groups of genes and regulatory elements that frequently interact with each other and are insulated from other regions, thereby preventing widespread uncontrolled DNA contacts. Chromatin loops formed within TADs through enhancer and promoter interactions are elastic, allowing transcriptional heterogeneity and stochasticity. Over the past decade, it has become evident that the 3D genome structure, also referred to as the chromatin architecture, is central to many transcriptional cellular decisions. In this Review, we delve into the intricate relationship between steroid receptors and LRIs, discussing how steroid receptors interact with and modulate these chromatin interactions. Genetic alterations in the many processes involved in organizing the nuclear architecture are often associated with the development of hormone-dependent cancers. A better understanding of the interplay between architectural proteins and hormone regulatory networks can ultimately be exploited to develop improved approaches for cancer treatment.

Regulation of the stem‑like properties of estrogen receptor‑positive breast cancer cells through NR2E3/NR2C2 signaling

Cancer stem cells (CSCs) are major drivers of metastasis, drug resistance and recurrence in numerous cancers. However, critical factors that can modulate CSC stemness have not been clearly identified. Nuclear receptor subfamily 2 group E member 3 (nr2e3) expression has been previously reported to be positively associated with drug sensitivity and favorable clinical outcomes in patients with estrogen receptor (ER)+ breast cancer. This suggests that nr2e3 expression may be inversely associated with CSC stemness in this type of tumor cells. The present study aimed to investigate the regulatory roles of NR2E3 in the stem-like properties of ER+ breast cancer cells and to identify the underlying mechanisms. Bioinformatics analysis was performed using the data derived from the Cancer Genome Atlas database. Nr2e3-specific shRNA and nuclear receptor subfamily 2 group C member 2 (nr2c2) overexpressed plasmids were constructed to silence and enhance the expression of nr2e3 and nr2c2, respectively. Transwell and wound healing experiments were conducted to evaluate the migration and invasion ability of MCF7 cells, while colony formation tests were used to evaluate the clonality. Flow cytometry was used to detect the percentage of CD44+CD24-/low cells. Reverse transcription-quantitative PCR and western blotting were performed to detect expression at the mRNA and protein levels. The results showed that compared with normal breast tissues and MCF10A cells, the expression of nr2e3 was increased in ER+ breast tumor tissues and cell lines. Nr2e3 silencing promoted the migration, invasion and colony-forming ability of the ER+ MCF7 cells. It also increased the expression of epithelial-mesenchymal transition markers and stem cell-related transcription factors, in addition to the percentage of CD44+CD24-/low cells. The expression of nr2e3 and nr2c2 was found to be positively correlated. Nr2e3 knockdown decreased the mRNA and protein expression levels of nr2c2, whereas nr2c2 overexpression reversed the elevated CD44+CD24-/low cell ratio and the increased migratory activity caused by nr2e3 silencing. The results of the present study suggest that NR2E3 may serve an important role in modulating the stem-like properties of ER+ breast cancer cells, where NR2E3/NR2C2 signaling may be a therapeutic target in ER+ breast cancer.

Flavonoids Quercetin and Kaempferol Are NR4A1 Antagonists and Suppress Endometriosis in Female Mice

Nuclear receptor 4A1 (NR4A1) plays an important role in endometriosis progression; levels of NR4A1 in endometriotic lesions are higher than in normal endometrium, and substituted bis-indole analogs (NR4A1) antagonists suppress endometriosis progression in mice with endometriosis. In addition, the flavonoids kaempferol and quercetin are natural products that directly bind NR4A1 and significantly repress the intrinsic NR4A1-dependent transcriptional activity in human endometriotic epithelial and stromal cells and Ishikawa endometrial cancer cells. NR4A1 knockdown and inhibition of NR4A1 by kaempferol and quercetin suppressed proliferation of human endometriotic epithelial cells and Ishikawa cells by inhibiting epidermal growth factor receptor/c-Myc/survivin-mediated growth-promoting and survival pathways, The mammalian target of rapamycin (mTOR) signaling and αSMA/CTGF/COL1A1/FN-mediated fibrosis signaling but increasing Thioredoxin domain Containing 5/SESN2-mediated oxidative/estrogen receptors stress signaling. In human endometriotic stromal cells, NR4A1 knockdown and inhibition of NR4A1 by kaempferol and quercetin primarily inhibited mTOR signaling by suppressing proliferation of human endometrial stromal cells. In addition, kaempferol and quercetin treatment also effectively suppressed the growth of endometriotic lesions in mice with endometriosis compared with the vehicle without any body weight changes. Therefore, kaempferol and quercetin are NR4A1 antagonists with potential as nutritional therapy for endometriosis.

Targeting nuclear hormone receptors for the prevention of breast cancer

Advancements in research have led to the steady decline of breast cancer mortality over the past thirty years. However, breast cancer incidence has continued to rise, resulting in an undue burden on healthcare costs and highlighting a great need for more effective breast cancer prevention strategies, including targeted chemo preventative agents. Efforts to understand the etiology of breast cancer have uncovered important roles for nuclear receptors in the development and progression of breast cancer. Targeted therapies to inhibit estrogen receptor (ER) and progesterone receptor (PR) signaling (selective ER modulators, aromatase inhibitors and selective PR modulators) have shown great promise for the treatment and prevention of hormone receptor (HR)-positive breast cancer. However, these drugs do not prevent HR-negative disease. Therefore, recent efforts have focused on novel targeted therapies with the potential to prevent both HR-positive and HR-negative breast cancer. Among these include drugs that target other nuclear receptors, such as retinoic acid receptor (RAR), retinoid X receptor (RXR) and vitamin D receptor (VDR). In this review we provide an overview of recent preclinical and clinical trials targeting members of the nuclear receptor superfamily for the prevention of breast cancer.

NR2F6, a new immune checkpoint that acts as a potential biomarker of immunosuppression and contributes to poor clinical outcome in human glioma

Intoroduction

Nuclear receptor subfamily 2 group F member 6 (NR2F6) is a promising checkpoint target for cancer immunotherapy. However, there has been no investigation of NR2F6 in glioma. Our study systematically explored the clinical characteristics and biological functions of NR2F6 in gliomas.

Methods

We extracted RNA sequencing (RNA-seq) data of 663 glioma samples from The Cancer Genome Atlas (TCGA) as the training cohort and 325 samples from the Chinese Glioma Genome Atlas (CGGA) as the validation cohort. We also confirmed the NR2F6 gene expression feature in our own cohort of 60 glioma patients. R language and GraphPad Prism softwares were mainly used for statistical analysis and graphical work.

Results

We found that NR2F6 was significantly related to high tumor aggressiveness and poor outcomes for glioma patients. Functional enrichment analysis demonstrated that NR2F6 was associated with many biological processes that are related to glioma progression, such as angiogenesis, and with multiple immune-related functions. Moreover, NR2F6 was found to be significantly correlated with stromal and immune infiltration in gliomas. Subsequent analysis based on Gliomas single-cell sequencing datasets showed that NR2F6 was expressed in immune cells, tumor cells, and stromal cells. Mechanistically, results suggested that NR2F6 might act as a potential immunosuppression-mediated molecule in the glioma microenvironment through multiple ways, such as the recruitment of immunosuppressive cells, secretion of immunosuppressive cytokines, M2 polarization of macrophages, in addition to combining with other immune checkpoint inhibitors.

Conclusion

Our findings indicated that intracellular targeting of NR2F6 in both immune cells and tumor cells, as well as stromal cells, may represent a promising immunotherapeutic strategy for glioma. Stromal cells, may represent a promising immunotherapeutic strategy for glioma.

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.

The nuclear receptor TLX (NR2E1) inhibits growth and progression of triple- negative breast cancer

Development of targeted therapies will be a critical step towards reducing the mortality associated with triple-negative breast cancer (TNBC). To achieve this, we searched for targets that met three criteria: (1) pharmacologically targetable, (2) expressed in TNBC, and (3) expression is prognostic in TNBC patients. Since nuclear receptors have a well-defined ligand-binding domain and are thus highly amenable to small-molecule intervention, we focused on this class of protein. Our analysis identified TLX (NR2E1) as a candidate. Specifically, elevated tumoral TLX expression was associated with prolonged recurrence-free survival and overall survival for breast cancer patients with either estrogen receptor alpha (ERα)-negative or basal-like tumors. Using two TNBC cell lines, we found that stable overexpression of TLX impairs in vitro proliferation. RNA-Seq analysis revealed that TLX reduced the expression of genes implicated in epithelial-mesenchymal transition (EMT), a cellular program known to drive metastatic progression. Indeed, TLX overexpression significantly decreased cell migration and invasion, and robustly decreased the metastatic capacity of TNBC cells in murine models. We identify SERPINB2 as a likely mediator of these effects. Taken together, our work indicates that TLX impedes the progression of TNBC. Several ligands have been shown to regulate the transcriptional activity of TLX, providing a framework for the future development of this receptor for therapeutic intervention.

The expression and biological effect of NR2F6 in non-small cell lung cancer

Objective

This study aimed to explore the expression and effect of the nuclear receptor subfamily 2 group F member 6 (NR2F6) gene in non-small cell lung cancer (NSCLC) and provide an experimental basis for the targeted therapy of NSCLC.

Method

First, the expression of NR2F6 in lung cancer tissues was analyzed using the Gene Expression Omnibus and the Cancer Genome Atlas (TCGA) databases, and the expression of NR2F6 in lung cancer tissues and cells was verified by Western blotting and quantitative polymerase chain reaction. Next, the relationship between NR2F6 expression and the clinicopathological features of lung cancer was analyzed via immunohistochemistry, and the relationship between NR2F6 expression and prognosis was analyzed using the Kaplan–Meier Plotter. The influence of NR2F6 knockdown on the proliferation capacity of lung cancer cells was then verified at cell level. Finally, the expression of heterogeneous nuclear ribonucleoprotein D (HNRNPD) in lung cancer tissue was analyzed using the TCGA database and immunohistochemistry. The impact of HNRNPD knockdown on the proliferation capacity of lung cancer cells was verified at cell level, and the relationship between NR2F6 and HNRNPD was verified by co-immunoprecipitation.

Results

NR2F6 was highly expressed in lung cancer tissues and cells, and its expression was positively correlated with the depth of invasion, lymphatic metastasis, and clinical stage of lung cancer. High expression of NR2F6 in lung cancer was also significantly associated with poor prognosis. At cell level, NR2F6 knockdown was found to inhibit the proliferation of H460 and H358 in lung cancer cells. Furthermore, the TCGA database and immunohistochemical results showed that HNRNPD was highly expressed in lung cancer tissues and was highly consistent with NR2F6 expression in these tissues. Knockdown of HNRNPD also inhibited the proliferation of lung cancer cells. The co-immunoprecipitation experiment verified that NR2F6 interacted with HNRNPD.

Conclusion

NR2F6 may interact with HNRNPD to jointly regulate the progression of lung cancer, and this conclusion provides a new experimental basis for the study of the molecular targeted therapy of NSCLC.

ROR activation by Nobiletin enhances antitumor efficacy via suppression of IκB/NF-κB signaling in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a heterogeneous disease characterized by poor response to standard therapies and therefore unfavorable clinical outcomes. Better understanding of TNBC and new therapeutic strategies are urgently needed. ROR nuclear receptors are multifunctional transcription factors with important roles in circadian pathways and other processes including immunity and tumorigenesis. Nobiletin (NOB) is a natural compound known to display anticancer effects, and our previous studies showed that NOB activates RORs to enhance circadian rhythms and promote physiological fitness in mice. Here, we identified several TNBC cell lines being sensitive to NOB, by itself or in combination. Cell and xenograft experiments showed that NOB significantly inhibited TNBC cell proliferation and motility in vitro and in vivo. ROR loss- and gain-of-function studies showed concordant effects of the NOB–ROR axis on MDA-MB-231 cell growth. Mechanistically, we found that NOB activates ROR binding to the ROR response elements (RRE) of the IκBα promoter, and NOB strongly inhibited p65 nuclear translocation. Consistent with transcriptomic analysis indicating cancer and NF-κB signaling as major pathways altered by NOB, p65-inducible expression abolished NOB effects, illustrating a requisite role of NF-κB suppression mediating the anti-TNBC effect of NOB. Finally, in vivo mouse xenograft studies showed that NOB enhanced the antitumor efficacy in mammary fat pad implanted TNBC, as a single agent or in combination with the chemotherapy agent Docetaxel. Together, our study highlights an anti-TNBC mechanism of ROR-NOB via suppression of NF-κB signaling, suggesting novel preventive and chemotherapeutic strategies against this devastating disease.

Cytoplasmic Colocalization of RXRα and PPARγ as an Independent Negative Prognosticator for Breast Cancer Patients

Retinoid X receptor α (RXRα) is a nuclear receptor (NR) which functions as the primary heterodimeric partner of other NRs including the peroxisome proliferator-activated receptor γ (PPARγ). We previously reported that, in breast cancers (BC), the subcellular localization of these two receptors was strongly associated with patient prognosis. In the present work, we investigated the prognosis value of the combined cytoplasmic expression of RXRα and PPARγ using a retrospective cohort of 250 BC samples. Patients with tumors expressing both NRs in tumor cell cytoplasm exhibited a significant shorter overall (OS) and disease-free survival (DFS). This was also observed for patients with stage 1 tumors. Cox univariate analysis indicated that patients with tumors coexpressing RXRα and PPARγ in the cytoplasm of tumor cells have a decreased 5 y OS rate. Cytoplasmic co-expression of the two NRs significantly correlated with HER2 positivity and with NCAD and CD133, two markers of tumor aggressiveness. Finally, in Cox multivariate analysis, the co-expression of RXRα and PPARγ in the cytoplasm appeared as an independent OS prognosticator. Altogether, this study demonstrates that the cytoplasmic co-expression of RXRα and PPARγ could be of relevance for clinicians by identifying high-risk BC patients, especially amongst those with early and node-negative disease.

Low concentrations of 17β-estradiol exacerbate tamoxifen resistance in breast cancer treatment through membrane estrogen receptor-mediated signaling pathways

The present study aims to discover the influences of tamoxifen and 17β-estradiol (E2) on tamoxifen-resistant (TamR) patients in vitro. Herein, we established a stabilized TamR MCF-7 cell line at 1 μM via gradient concentrations of tamoxifen cultivation. The expression changes of four ER subtypes (ERα66, ERβ, ERα36 and GPR30) were found to bring about tamoxifen resistance. Moreover, the generation of tamoxifen resistance involved in apoptosis escape via a reactive oxygen species-regulated p53 signaling pathway. Interestingly, E2 at environmental concentrations (0.1-10 nM) could activate the expression of both ERα36 and GPR30, and then stimulate the phosphorylation of ERK1/2 and Akt, resulting in cell growth promotion. Cell migration and invasion promotion, apoptosis inhibition, and cell cycle G1-S progression are involved in such proliferative effects. Conversely, the application of specific antagonists of ERα36 and GPR30 could restore tamoxifen's sensitivity as well as partially offset E2-mediated proliferation. In short, overexpression of ERα36 and GPR30 not only ablate tamoxifen responsiveness but also could promote tumor progression of TamR breast cancer under estrogen conditions. These results provided novel insights into underlying mechanisms of tamoxifen resistance and the negative effects of steroid estrogens at environmental concentrations on TamR MCF-7 cells, thus generating new thoughts for future management of ER-positive breast cancer.

Nuclear receptor 4A1 (NR4A1) antagonists target paraspeckle component 1 (PSPC1) in cancer cells

Paraspeckles compound 1 (PSPC1) is a multifunctional protein that plays an important role in cancer cells, where PSPC1 is a master regulator of pro-oncogenic responses that includes activation of TGFβ (TGFβ1), TGFβ-dependent EMT, and metastasis. The pro-oncogenic activities of PSPC1 closely resembled those observed for the orphan nuclear receptor 4A1 (NR4A1, Nur77) and knockdown of NR4A1 decreased expression of PSPC1 in MDA-MB-231 breast, H1299 lung, and SNU449 liver cancer cells. Similar results were observed in these same cell lines after treatment with bisindole-derived (CDIMs) NR4A1 antagonists. Moreover, PSPC1-dependent regulation of TGFβ, genes associated with cancer stem cells and epithelial to mesenchymal transition (EMT) were also downregulated after NR4A1 silencing or treatment of breast, lung, and liver cancer cells with CDIM/NR4A1 antagonists. Results of chromatin immunoprecipitation (ChIP) assays suggest that NR4A1 regulates PSPC1 through interaction with an NBRE sequence in the PSPC1 gene promoter. These results coupled with in vivo studies showing that NR4A1 antagonists inhibit breast tumor growth and downregulate PSPC1 in tumors indicate that the pro-oncogenic nuclear PSPC1 factor can be targeted by CDIM/NR4A1 antagonists.

Transcription factors specificity protein and nuclear receptor 4A1 in pancreatic cancer

Specificity protein (Sp) transcription factors (TFs) Sp1, Sp3 and Sp4, and the orphan nuclear receptor 4A1 (NR4A1) are highly expressed in pancreatic tumors and Sp1 is a negative prognostic factor for pancreatic cancer patient survival. Results of knockdown and overexpression of Sp1, Sp3 and Sp4 in pancreatic and other cancer lines show that these TFs are individually pro-oncogenic factors and loss of one Sp TF is not compensated by other members. NR4A1 is also a pro-oncogenic factor and both NR4A1 and Sp TFs exhibit similar functions in pancreatic cancer cells and regulate cell growth, survival, migration and invasion. There is also evidence that Sp TFs and NR4A1 regulate some of the same genes including survivin, epidermal growth factor receptor, PAX3-FOXO1, α5- and α6-integrins, β1-, β3- and β4-integrins; this is due to NR4A1 acting as a cofactor and mediating NR4A1/Sp1/4-regulated gene expression through GC-rich gene promoter sites. Several studies show that drugs targeting Sp downregulation or NR4A1 antagonists are highly effective inhibitors of Sp/NR4A1-regulated pathways and genes in pancreatic and other cancer cells, and the triterpenoid celastrol is a novel dual-acting agent that targets both Sp TFs and NR4A1.

Cytoplasmic Localization of RXRα Determines Outcome in Breast Cancer

Simple Summary

Considering the immense development of today’s therapeutic approaches in oncology towards customized therapy, this study aimed to assess the prognostic value of nuclear versus cytoplasmic retinoid X receptor α (RXRα) expression in breast cancer. Our results demonstrate that RXRα expression may have different roles in tumorigenesis according to its subcellular localization. This study strengthens the need for further research on the behavior of RXRα, depending on its intracellular localization.

Abstract

The aim of this retrospective study was to assess the prognostic value of cytoplasmic versus nuclear RXRα expression in breast cancer (BC) tissue samples and to correlate the results with clinicopathological parameters. In 319 BC patients, the expression of RXRα was evaluated via immunohistochemistry. Prognosis-determining aspects were calculated through uni- and multivariate analyses. Correlation analysis revealed a trend association with nuclear RXRα expression regarding an improved overall survival (OS) (p = 0.078), whereas cytoplasmic RXRα expression was significantly correlated with a poor outcomes in terms of both OS (p = 0.038) and disease-free survival (DFS) (p = 0.037). Strengthening these results, cytoplasmic RXRα was found to be an independent marker for DFS (p = 0.023), when adjusted to clinicopathological parameters, whereas nuclear RXRα expression was positively associated with lower TNM-staging, i.e., pT (p = 0.01), pN (p = 0.029) and pM (p = 0.001). Additionally, cytoplasmic RXRα expression was positively associated with a higher histopathological tumor grading (p = 0.02). Cytoplasmic RXRα was also found to be a negative prognosticator for Her-2neu-negative and triple-negative patients. Altogether, these findings support the hypothesis that the subcellular localization of RXRα plays an important role in carcinogenesis and the prognosis of BC. The expression of cytoplasmic RXRα is correlated with a more aggressive course of the disease, whereas nuclear RXRα expression appears to be a protective factor. These data may help to identify high-risk BC subgroups in order to find possible specific options in targeted tumor therapy.

BC-N102 suppress breast cancer tumorigenesis by interfering with cell cycle regulatory proteins and hormonal signaling, and induction of time-course arrest of cell cycle at G1/G0 phase

Mechanisms of breast cancer progression and invasion, often involve alteration of hormonal signaling, and upregulation and/or activation of signal transduction pathways that input to cell cycle regulation. Herein, we describe a rationally designed first-in-class novel small molecule inhibitor for targeting oncogenic and hormonal signaling in ER-positive breast cancer. BC-N102 treatment exhibits dose-dependent cytotoxic effects against ER+ breast cancer cell lines. BC-N102 exhibited time course- and dose-dependent cell cycle arrest via downregulation of the estrogen receptor (ER), progesterone receptor (PR), androgen receptor (AR), phosphatidylinositol 3-kinase (PI3K), phosphorylated (p)-extracellular signal-regulated kinase (ERK), p-Akt, CDK2, and CDK4 while increasing p38 mitogen-activated protein kinase (MAPK), and mineralocorticoid receptor (MR) signaling in breast cancer cell line. In addition, we found that BC-N102 suppressed breast cancer tumorigenesis in vivo and prolonged the survival of animals. Our results suggest that the proper application of BC-N102 may be a beneficial chemotherapeutic strategy for ER+ breast cancer patients.

A seven-nuclear receptor-based prognostic signature in breast cancer

BACKGROUND

Breast cancer (BRCA) is a malignant cancer that threatened the life of female with unsatisfactory prognosis. The aim of this study was to identify prognostic nuclear receptors (NRs) signature of BRCA.

METHODS

BRCA patient samples were collected from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database. Consensus clustering analysis, univariate Cox regression analysis and the least absolute shrinkage and selection operator (LASSO) Cox regression analysis were performed to evaluate, select NRs as prognostic factors and build Risk Score model. GSEA analysis was explored to check signaling differences between High- and Low-Risk group. Nomogram model basing on age and Risk Score was established to predict the 1-, 3- and 5-year survival. Model performance was assessed by a time-dependent receiver operating characteristic (ROC) curve and calibration plot. CIBERSORT, ESTIMATE and TIMER algorithm were introduced to evaluate the immune landscape.

RESULTS

NR3C1, NR4A3, THRA, RXRG, NR2F6, NR1D2 and RORB were optimized as a prognostic signature for BRCA. This seven-NR-based Risk Score could effectively predict overall survival status. The area under the curve (AUC) of 1-, 3- and 5-year overall survival are 0.702, 0.734 and 0.722 in TCGA training cohort, and 0.630, 0.721 and 0.823 in GEO validation cohort, respectively. Calibration plot demonstrated satisfactory agreement between predictive and observed outcomes. Nomogram model worked well on predicting survival probabilities. Multiple cancer-related pathways were highly enriched in High-Risk group. High- and Low-Risk groups showed significant differed immune cell infiltration. There exists an obvious connection between Risk Score and immune checkpoints LAG3, PD1 and TIM3.

CONCLUSION

The seven-NR-based Risk Score represents a promising signature for estimating overall survival in patients with BRCA, and is correlated with the immune microenvironment.

Revealing nuclear receptor hub modules from Basal-like breast cancer expression networks

Nuclear receptors are a class of transcriptional factors. Together with their co-regulators, they regulate development, homeostasis, and metabolism in a ligand-dependent manner. Their ability to respond to environmental stimuli rapidly makes them versatile cellular components. Their coordinated activities regulate essential pathways in normal physiology and in disease. Due to their complexity, the challenge remains in understanding their direct associations in cancer development. Basal-like breast cancer is an aggressive form of breast cancer that often lacks ER, PR and Her2. The absence of these receptors limits the treatment for patients to the non-selective cytotoxic and cytostatic drugs. To identify potential drug targets it is essential to identify the most important nuclear receptor association network motifs in Basal-like subtype progression. This research aimed to reveal the transcriptional network patterns, in the hope to capture the underlying molecular state driving Basal-like oncogenesis. In this work, we illustrate a multidisciplinary approach of integrating an unsupervised machine learning clustering method with network modelling to reveal unique transcriptional patterns (network motifs) underlying Basal-like breast cancer. The unsupervised clustering method provides a natural stratification of breast cancer patients, revealing the underlying heterogeneity in Basal-like. Identification of gene correlation networks (GCNs) from Basal-like patients in both the TCGA and METABRIC databases revealed three critical transcriptional regulatory constellations that are enriched in Basal-like. These represent critical NR components implicated in Basal-like breast cancer transcription. This approach is easily adaptable and applicable to reveal critical signalling relationships in other diseases.

NR4A1 Ligands as Potent Inhibitors of Breast Cancer Cell and Tumor Growth

Nuclear receptor 4A1 (NR4A1, Nur77, TR3) is more highly expressed in breast and solid tumors compared to non-tumor tissues and is a pro-oncogenic factor in solid tumor-derived cancers. NR4A1 regulates cancer cell growth, survival, migration, and invasion, and bis-indole-derived compounds (CDIMs) that bind NR4A1 act as antagonists and inhibit tumor growth. Preliminary structure-binding studies identified 1,1-bis(3'-indolyl)-1-(3,5-disubstitutedphenyl)methane analogs as NR4A1 ligands with low K_D values; we further investigated the anticancer activity of the four most active analogs (K_D's ≤ 3.1 µM) in breast cancer cells and in athymic mouse xenograft models. The treatment of MDA-MB-231 and SKBR3 breast cancer cells with the 3-bromo-5-methoxy, 3-chloro-5-trifluoromethoxy, 3-chloro-5-trifluoromethyl, and 3-bromo-5-trifluoromethoxy phenyl-substituted analogs decreased cell growth and the expression of epidermal of growth factor receptor (EGFR), hepatocyte growth factor receptor (cMET), and PD-L1 as well as inhibited mTOR phosphorylation. In addition, all four compounds inhibited tumor growth in athymic nude mice bearing MDA-MB-231 cells (orthotopic) at a dose of 1 mg/kg/d, which was not accompanied by changes in body weight. These 3,5-disubstituted analogs were the most potent CDIM/NR4A1 ligands reported and are being further developed for clinical applications.

Emerging Next-Generation Target for Cancer Immunotherapy Research: The Orphan Nuclear Receptor NR2F6

Simple Summary

The most successful strategies for solid cancer immunotherapy have centered on targeting the co-stimulatory and co-inhibitory T cell molecules that regulate T cell activation. Although immunotherapy that targets surface receptors such as CTLA-4 and/or PD-1 with recombinant antibodies has been a game changer for cancer treatment, a sizeable subset of patients still fail to respond to, and even fewer patients are cured by, these therapy regimens. Here, we discuss the unique potential of NR2F6 as an emerging target for cancer immunotherapy to significantly increase response rates of cancer patients and/or to extend treatment to a broader range of cancer types.

Abstract

Additional therapeutic targets suitable for boosting anti-tumor effector responses have been found inside effector CD4⁺ and CD8⁺ T cells. It is likely that future treatment options will combine surface receptor and intracellular protein targets. Utilizing germline gene ablation as well as CRISPR/Cas9-mediated acute gene mutagenesis, the nuclear receptor NR2F6 (nuclear receptor subfamily 2 group F member 6, also called Ear-2) has been firmly characterized as such an intracellular immune checkpoint in effector T cells. Targeting this receptor appears to be a strategy for improving anti-tumor immunotherapy responses, especially in combination with CTLA-4 and PD-1. Current preclinical experimental knowledge firmly validates the immune checkpoint function of NR2F6 in murine tumor models, which provides a promising perspective for immunotherapy regimens in humans in the near future. While the clinical focus remains on the B7/CD28 family members, protein candidate targets such as NR2F6 are now being investigated in laboratories around the world and in R&D companies. Such an alternative therapeutic approach, if demonstrated to be successful, could supplement the existing therapeutic models and significantly increase response rates of cancer patients and/or expand the reach of immune therapy regimens to include a wider range of cancer entities. In this perspective review, the role of NR2F6 as an emerging and druggable target in immuno-oncology research will be discussed, with special emphasis on the unique potential of NR2F6 and its critical and non-redundant role in both immune and tumor cells.

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.

A tumour suppressive relationship between mineralocorticoid and retinoic acid receptors activates a transcriptional program consistent with a reverse Warburg effect in breast cancer

Background

The role of nuclear receptors in both the aetiology and treatment of breast cancer is exemplified by the use of the oestrogen receptor (ER) as a prognostic marker and treatment target. Treatments targeting the oestrogen signalling pathway are initially highly effective for most patients. However, for the breast cancers that fail to respond, or become resistant, to current endocrine treatments, the long-term outlook is poor. ER is a member of the nuclear receptor superfamily, comprising 48 members in the human, many of which are expressed in the breast and could be used as alternative targets in cases where current treatments are ineffective.

Methods

We used sparse canonical correlation analysis to interrogate potential novel nuclear receptor expression relationships in normal breast and breast cancer. These were further explored using whole transcriptome profiling in breast cancer cells after combinations of ligand treatments.

Results

Using this approach, we discovered a tumour suppressive relationship between the mineralocorticoid receptor (MR) and retinoic acid receptors (RAR), in particular RARβ. Expression profiling of MR expressing breast cancer cells revealed that mineralocorticoid and retinoid co-treatment activated an expression program consistent with a reverse Warburg effect and growth inhibition, which was not observed with either ligand alone. Moreover, high expression of both MR and RARB was associated with improved breast cancer-specific survival.

Conclusion

Our study reveals a previously unknown relationship between MR and RAR in the breast, which is dependent on menopausal state and altered in malignancy. This finding identifies potential new targets for the treatment of breast cancers that are refractory to existing therapeutic options.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s13058-020-01355-x.

The Paradoxical Roles of Orphan Nuclear Receptor 4A (NR4A) in Cancer

The three-orphan nuclear receptor 4A genes are induced by diverse stressors and stimuli, and there is increasing evidence that NR4A1 (Nur77), NR4A2 (Nurr1), and NR4A3 (Nor1) play an important role in maintaining cellular homeostasis and in pathophysiology. In blood-derived tumors (leukemias and lymphomas), NR4A expression is low and NR4A1^-/-/NR4A3^-/- double knockout mice rapidly develop acute myelocytic leukemia, suggesting that these receptors exhibit tumor suppressor activity. Treatment of leukemia and most lymphoma cells with drugs that induce expression of NR4A1and NR4A3 enhances apoptosis, and this represents a potential clinical application for treating this disease. In contrast, most solid tumor-derived cell lines express high levels of NR4A1 and NR4A2, and both receptors exhibit pro-oncogenic activities in solid tumors, whereas NR4A3 exhibits tumor-specific activities. Initial studies with retinoids and apoptosis-inducing agents demonstrated that their cytotoxic activity is NR4A1 dependent and involved drug-induced nuclear export of NR4A1 and formation of a mitochondrial proapoptotic NR4A1-bcl-2 complex. Drug-induced nuclear export of NR4A1 has been reported for many agents/biologics and involves interactions with multiple mitochondrial and extramitochondrial factors to induce apoptosis. Synthetic ligands for NR4A1, NR4A2, and NR4A3 have been identified, and among these compounds, bis-indole derived (CDIM) NR4A1 ligands primarily act on nuclear NR4A1 to inhibit NR4A1-regulated pro-oncogenic pathways/genes and similar results have been observed for CDIMs that bind NR4A2. Based on results of laboratory animal studies development of NR4A inducers (blood-derived cancers) and NR4A1/NR4A2 antagonists (solid tumors) may be promising for cancer therapy and also for enhancing immune surveillance.

Immune microenvironment in different molecular subtypes of ductal breast carcinoma

PURPOSE

Ductal breast carcinoma as a heterogeneous disease has different molecular subtypes associated with clinical prognosis and patients' survival. The role of immune system as a consistent part of the tumor microenvironment (TME) has been documented in progression of ductal breast carcinoma. Here, we aimed to describe the important immune cells and the immune system-associated molecules in Ductal Carcinoma In situ (DCIS) and Invasive Ductal Carcinoma (IDC) with special emphasis on their associations with different molecular subtypes and patients' prognosis.

RESULTS

The immune cells have a dual role in breast cancer (BC) microenvironment depending on the molecular subtype or tumor grade. These cells with different frequencies are present in the TME of DCIS and IDC. The presence of regulatory cells including Tregs, MDSC, Th2, Th17, M2 macrophages, HLADR^- T cells, and Tγδ cells is related to more immunosuppressive microenvironment, especially in ER^- and TN subtypes. In contrast, NK cells, CTL, Th, and Tfh cells are associated to the anti-tumor activity. These cells are higher in ER⁺ BC, although in other subtypes such as TN or HER2⁺ are associated with a favorable prognosis.

CONCLUSION

Determining the specific immune response in each subtype could be helpful in estimating the possible behavior of the tumor cells in TME. It is important to realize that different frequencies of immune cells in BC environment likely determine the patients' prognosis and their survival in each subtype. Therefore, elucidation of the distinct immune players in TME would be helpful toward developing targeted therapies in each subtype.

Evaluation of NMU-Induced Breast Cancer Treated with Sirolimus and Sunitinib on Breast Cancer Growth

Objective:

To analyze the effect of sirolimus and sunitinib in blocking the tumor growth and to evaluate the expressions of estrogen receptor (ER), progesterone receptor (PgR), and human epidermal growth factor receptor-2 (HER2/neu) after treated with sirolimus and sunitinib.

Methods:

Thirty-two female Sprague Dawley rats at age 21-days old were administered intraperitoneally with N-Methyl-N-Nitroso Urea (NMU), dosed at 70mg/kg body weight. The rats were divided into 4 groups; Group 1 (Control, n=8), Group 2 (Sirolimus, n=8), Group 3 (Sunitinib, n=8) and Group 4 (Sirolimus+Sunitinib, n=8), being treated twice when the tumor reached the size of 14.5±0.5 mm and subsequently sacrificed after 5 days. The protein expressions of ER, PgR and HER2/neu of the tumor tissues were evaluated by using immunohistochemistry analysis.

Results:

Treatment with sirolimus alone lowered expressions of ER and PgR of breast cancer and reduced tumor size. There was no significant difference of ER and PgR expressions between control and sunitinib treated tumor. Sunitinib treated tumors reduce in diameter after the first treatment, however the diameter increases after the second treatment. Histologically, sunitinib treated tumor did not show any aggressive invasive carcinoma of no special type (NST) histological subtypes. In addition, all NMU-induced tumors are HER2/neu-negative scoring.

Conclusion:

Sirolimus is neither synergistic nor additive with sunitinib for breast cancer treatment.

Oncogenic Orphan Nuclear Receptor NR4A3 Interacts and Cooperates with MYB in Acinic Cell Carcinoma

Acinic cell carcinoma (AcCC) is a morphologically distinctive salivary gland malignancy often associated with chromosome rearrangements leading to overexpression of the NR4A3 transcription factor. However, little is known about how NR4A3 contributes to AcCC biology. Detailed RNA-sequencing of 21 archived AcCC samples revealed fusion reads arising from recurrent t(4;9), t(9;12), t(8;9) or t(2;4) chromosomal translocations, which positioned highly active enhancers adjacent to the promoter of the NR4A3 gene or the closely related NR4A2 gene, resulting in their aberrant overexpression. Transcriptome analyses revealed several distinct subgroups of AcCC tumors, including a subgroup that overexpressed both NR4A3 and MSANTD3. A poor survival subset of the tumors with high-grade transformation expressed NR4A3 and POMC as well as MYB, an oncogene that is the major driver in a different type of salivary gland tumor, adenoid cystic carcinoma. The combination of NR4A3 and MYB showed cooperativity in regulating a distinct set of genes. In addition, the ligand binding domain of NR4A3 directly bound the Myb DNA binding domain. Transformation assays indicated that, while overexpressed NR4A3 was sufficient to generate transformed colonies, the combination of NR4A3 plus Myb was more potent, leading to anchorage-independent growth and increased cellular invasiveness. The results confirm that NR4A3 and NR4A2 are the main driver genes of AcCC and suggest that concurrent overexpression of NR4A3 and MYB defines a subset of AcCC patients with high-grade transformation that display exceptionally poor outcome.

Bis-indole derived nuclear receptor 4A1 (NR4A1) antagonists inhibit TGFβ-induced invasion of embryonal rhabdomyosarcoma cells

Transforming growth factor β (TGFβ) enhances invasion of breast and lung cancer cells through phosphorylation-dependent nuclear export of the nuclear receptor 4A1 (NR4A1, Nur77). This response is inhibited by the NR4A1 antagonist 1,1-bis(3'-indoly)-1-(p-hydroxyphenyl) methane (CDIM8) and we hypothesized that similar effects would be observed in Rhabdomyosarcoma (RMS) cells. Although some kinase inhibitors block TGFβ-induced invasion of embryonal RMS (ERMS) cells, the mechanism differs from breast and lung cancer cells since NR4A1 is extranuclear in ERMS cells. However, CDIM8 blocks basal and TGFβ-induced invasion of RD and SMS-CTR ERMS cell lines but not Rh30 alveolar RMS (ARMS) cells. Moreover, this response in ERMS cells was independent of SMAD7 degradation or activation of SMAD2/SMAD3. β-Catenin silencing decreased ERMS cell invasion and CDIM8 induced proteasome-independent downregulation of β-catenin. The novel mechanism of CDIM8-mediated inhibition of basal and TGFβ-induced ERMS cell invasion was due to activation of the Bcl-2-NR4A1 complex, mitochondrial disruption, induction of the tumor suppressor-like cytokine interleukin-24 (IL-24) which in turn downregulates β-catenin expression. Thus, the NR4A1 antagonist inhibits TGFβ-induced invasion of ERMS cells through initial targeting of cytosolic NR4A1.

Bis-Indole-Derived Nuclear Receptor 4A1 (NR4A1, Nur77) Ligands as Inhibitors of Endometriosis

Endometriosis is an inflammatory disease that primarily affects women during their reproductive years, and since current hormonal therapies are of concern, new hormone-independent treatment regimens are needed. The orphan nuclear receptor 4A1 (NR4A1, Nur77) is expressed in patient-derived (stromal) endometriotic cells and also epithelial cell lines, and we observed that knockdown of NR4A1 in patient-derived ectopic endometrium-isolated ovarian endometrioma (ESECT)-7 and ESECT-40 cells decreased cell proliferation and induced apoptosis. Moreover, the treatment of these cells with bis-indole derived NR4A1 ligands 1,1-bis(3'-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH) and its buttressed 3-chloro-5-methoxy analog (DIM-C-pPhOH-3-Cl-5-OCH3) inhibited cell growth and induced apoptosis and related genes. The compounds exhibit NR4A1 antagonist activities in both functional and transactivation assays whereas these effects were not observed in normal endometrial cells. We also observed that NR4A1 knockdown and treatment with NR4A1 antagonists decreased fibrosis, α-smooth muscle actin, and related pro-fibrotic genes in ESECT-7 and ESECT-40 cells, and similar results were observed in epithelial-derived endometriotic cell lines. Moreover, in an endometriosis mouse model with auto-transplantation and also in severe combined immune deficiency mice transplanted with human endometriotic cells treatment with 25 mg/kg/day DIM-C-pPhOH-3-Cl-5-OCH3 significantly inhibited growth and expansion of endometriotic lesions. Thus, bis-indole-derived NR4A1 ligands represent a novel class of drugs as nonhormonal therapy for endometriosis.

A Bis-Indole-Derived NR4A1 Antagonist Induces PD-L1 Degradation and Enhances Antitumor Immunity

PD-L1 is expressed in tumor cells and its interaction with PD-1 plays an important role in evading immune surveillance; this can be overcome using PD-L1 or PD-1 immunotherapy antibodies. This study reports a novel approach for targeting PD-L1. In human breast cancer cell lines and 4T1 mouse mammary tumor cells, PD-L1 expression was regulated by the nuclear receptor NR4A1/Sp1 complex bound to the proximal germinal center (GC)-rich region of the PD-L1 gene promoter. Treatment of breast cancer cells with bis-indole-derived NR4A1 antagonists including 1,1-bis(3'-indolyl)-1-(3-chloro-4-hydroxy-5-methoxyphenyl)methane (Cl-OCH3) decreased expression of PD-L1 mRNA, promoter-dependent luciferase activity, and protein. In in vivo studies using a syngeneic mouse model bearing orthotopically injected 4T1 cells, Cl-OCH3 decreased tumor growth and weight and inhibited lung metastasis. Cl-OCH3 also decreased expression of CD3⁺/CD4⁺/CD25⁺/FoxP3⁺ regulatory T cells and increased the Teff/Treg ratio. Therefore, the potent anticancer activities of NR4A1 antagonists are also accompanied by enhanced antitumor immunity in PD-L1-expressing triple-negative breast cancer and thus represent a novel class of drugs that mimic immunotherapy. SIGNIFICANCE: These findings show that the orphan nuclear receptor NR4A1 controls PD-L1 expression and identify a chemical probe capable of disrupting this regulatory axis.

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.

Thyroid Hormone Receptor β Inhibits Self-Renewal Capacity of Breast Cancer Stem Cells

Background: A subpopulation of cancer stem cells (CSCs) with capacity for self-renewal is believed to drive initiation, progression, and relapse of breast tumors. Methods: Since the thyroid hormone receptor β (TRβ) appears to suppress breast tumor growth and metastasis, we have analyzed the possibility that TRβ could affect the CSC population using MCF-7 cells grown under adherent conditions or as mammospheres, as well as inoculation into immunodeficient mice. Results: Treatment of TRβ-expressing MCF-7 cells (MCF7-TRβ cells) with the thyroid hormone triiodothyronine (T3) decreased significantly CD44⁺/CD24^- and ALDH⁺ cell subpopulations, the efficiency of mammosphere formation, the self-renewal capacity of CSCs in limiting dilution assays, the expression of the pluripotency factors in the mammospheres, and tumor initiating capacity in immunodeficient mice, indicating that the hormone reduces the CSC population present within the bulk MCF7-TRβ cultures. T3 also decreased migration and invasion, a hallmark of CSCs. Transcriptome analysis showed downregulation of the estrogen receptor alpha (ERα) and ER-responsive genes by T3. Furthermore, among the T3-repressed genes, there was an enrichment in genes containing binding sites for transcription factors that are key determinants of luminal-type breast cancers and are required for ER binding to chromatin. Conclusion: We demonstrate a novel role of TRβ in the biology of CSCs that may be related to its action as a tumor suppressor in breast cancer.

COUP-TFII in Health and Disease

The nuclear receptors (NRs) belong to a vast family of evolutionary conserved proteins acting as ligand-activated transcription factors. Functionally, NRs are essential in embryogenesis and organogenesis and in adulthood they are involved in almost every physiological and pathological process. Our knowledge of NRs action has greatly improved in recent years, demonstrating that both their expression and activity are tightly regulated by a network of signaling pathways, miRNA and reciprocal interactions. The Chicken Ovalbumin Upstream Promoter Transcription Factor II (COUP-TFII, NR2F2) is a NR classified as an orphan due to the lack of a known natural ligand. Although its expression peaks during development, and then decreases considerably, in adult tissues, COUP-TFII is an important regulator of differentiation and it is variably implicated in tissues homeostasis. As such, alterations of its expression or its transcriptional activity have been studied and linked to a spectrum of diseases in organs and tissues of different origins. Indeed, an altered COUP-TFII expression and activity may cause infertility, abnormality in the vascular system and metabolic diseases like diabetes. Moreover, COUP-TFII is actively investigated in cancer research but its role in tumor progression is yet to be fully understood. In this review, we summarize the current understanding of COUP-TFII in healthy and pathological conditions, proposing an updated and critical view of the many functions of this NR.

Retinoid X receptor gamma (RXRG) is an independent prognostic biomarker in ER-positive invasive breast cancer

BACKGROUND

Retinoid X Receptor Gamma (RXRG) is a member of the nuclear receptor superfamily and plays a role in tumour suppression. This study aims to explore the prognostic significance of RXRG in breast cancer.

METHODS

Primary breast cancer tissue microarrays (n = 923) were immuno-stained for RXRG protein and correlated with clinicopathological features, and patient outcome.

RESULTS

Nuclear RXRG expression was significantly associated with smaller tumour size (p = 0.036), lower grade (p < 0.001), lobular histology (p = 0.016), lower Nottingham Prognostic Index (p = 0.04) and longer breast cancer-specific survival (p < 0.001), and longer time to distant metastasis (p = 0.002). RXRG expression showed positive association with oestrogen receptor (ER)-related biomarkers: GATA3, FOXA1, STAT3 and MED7 (all p < 0.001) and a negative correlation with the Ki67 proliferation marker. Multivariate analysis demonstrated RXRG protein as an independent predictor of longer breast cancer-specific survival and distant metastasis-free survival. In the external validation cohorts, RXRG expression was associated with improved patients' outcome (p = 0.025). In ER-positive tumours, high expression of RXRG was associated with better patient outcome regardless of adjuvant systemic therapy. ER signalling pathway was the top predicted master regulator of RXRG protein expression (p = 0.005).

CONCLUSION

This study provides evidence for the prognostic value of RXRG in breast cancer particularly the ER-positive tumours.

Inhibition of NR4A1 Promotes ROS Accumulation and IL24-Dependent Growth Arrest in Rhabdomyosarcoma

Nuclear receptor 4A1 (NR4A1, Nur77) is overexpressed in rhabdomyosarcoma (RMS), and inactivation of NR4A1 (siNR4A1) or treatment with the NR4A1 antagonist 1,1-bis(3'-indoly)-1-(p-hydroxy-phenyl)methane (DIM-C-pPhOH) has antiproliferative and proapoptotic effects on RMS cells. However, the mechanism by which NR4A1 inhibition exerts these effects is poorly defined. Here, we report that NR4A1 silencing or inhibition resulted in accumulation of reactive oxygen species (ROS) and ROS-dependent induction of the tumor suppressor-like cytokine IL24 in RMS cells. Mechanistically, NR4A1 was found to regulate the expression of the proreductant genes thioredoxin domain-containing 5 (TXNDC5) and isocitrate dehydrogenase 1 (IDH1), which are downregulated in RMS cells following NR4A1 knockdown or inhibition. Silencing TXNDC5 and IDH1 also induced ROS accumulation and IL24 expression in RMS cells, suggesting that NR4A1 antagonists mediate their antiproliferative and apoptotic effects through modulation of proreductant gene expression. Finally, cotreatment with the antioxidant glutathione or IL24-blocking antibody reversed the effects of NR4A1 inhibition, demonstrating the importance of both ROS and IL24 in mediating the cellular responses. IMPLICATIONS: Overall, these data elucidate the mechanism by which NR4A1 inhibition functions to inhibit the proliferation, survival, and migration of RMS cells.

Potent inhibition of breast cancer by bis-indole-derived nuclear receptor 4A1 (NR4A1) antagonists

BACKGROUND

Nuclear receptor 4A1 (NR4A1) is overexpressed in mammary tumors, and the methylene-substituted bis-indole derivative 1,1-bis(3'-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH) acts as an NR4A1 antagonist (inverse agonist) and inhibits NR4A1-regulated pro-oncogenic pathways/genes in breast and other cancer cells.

METHODS

Buttressed analogs of DIM-C-pPhOH were synthesized by condensation of the substituted p-hydroxybenzaldehydes with indole. Breast cancer cell growth, survival, and migration assays were carried out by cell counting, Annexin V staining, and Boyden chamber assays, respectively. Changes in RNA and protein expression were determined by RT-PCR and western blots, respectively. Analysis of RNAseq results was carried out using Ingenuity Pathway Analysis, and in vivo potencies of NR4A1 antagonists were determined in athymic nude mice bearing MDA-MB-231 cells in an orthotopic model.

RESULTS

Ingenuity Pathway analysis of common genes modulated by NR4A1 knockdown or treatment with DIM-C-pPhOH showed that changes in gene expression were consistent with the observed decreased functional responses, namely inhibition of growth and migration and increased apoptosis. DIM-C-pPhOH is rapidly metabolized and the effects and potencies of buttressed analogs of DIM-C-pPhOH which contain one or two substituents ortho to the hydroxyl groups were investigated using NR4A1-regulated gene/gene products as endpoints. The buttressed analogs were more potent than DIM-C-pPhOH in both in vitro assays and as inhibitors of mammary tumor growth. Moreover, using 1,1-bis(3'-indolyl)-1-(3-chloro-4-hydroxy-5-methoxyphenyl)methane (DIM-C-pPhOh-3-Cl-5-OCH3) significant tumor growth inhibition was observed at doses as low as 2 mg/kg/d which was at least an order of magnitude more potent than DIM-C-pPhOH.

CONCLUSIONS

These buttressed analogs represent a more potent set of second generation NR4A1 antagonists as inhibitors of breast cancer.

Orphan nuclear receptor COUP-TFII is an oncogenic gene in renal cell carcinoma

BACKGROUND

Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) may be an oncogenic gene in renal cell carcinoma (RCC). However, the direct association between COUP-TFII expression and patient survival has not been investigated in patients with RCC, and the molecular oncogenesis of COUP-TFII in RCC remains unclear.

METHODS

The mRNA expression levels of COUP-TFII in the tumors of 283 patients with RCC were determined by RT-qPCR. The remaining 266 patients were categorized into low- and high-expression groups according to the cut off value generated by receiver operating curve (ROC) analysis. The function of COUP-TFII in RCC cells was tested by knockdown experiments in vitro.

RESULTS

In the present study, it was revealed that the mRNA expression levels of COUP-TFII were significantly higher in tumors compared with those in adjacent non-cancerous tissues, and that the overexpression of COUP-TFII was strongly associated with poor patient survival. It was further demonstrated that knockdown of COUP-TFII suppressed proliferation, and induced apoptosis and cell cycle arrest in RCC cells in vitro. This also resulted in the activation of the mitochondria-mediated apoptosis pathway, impaired migration and invasion of RCC cells through epithelial-mesenchymal transition in vitro, and suppressed tumor growth in vivo. In addition, it was revealed that the induction of cell migration and invasion by COUP-TFII was mediated, at least in part, by integrin subunit β1.

CONCLUSIONS

In summary, the present study indicated that COUP-TFII is an oncogenic gene in RCC, and a potential therapeutic target for the treatment of the disease.

MiR-142-3p suppresses the proliferation, migration and invasion through inhibition of NR2F6 in lung adenocarcinoma

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death worldwide and lung adenocarcinoma is its main type. MicroRNAs are small, non-coding and single-strand RNAs that regulate gene expression in human cancers. The aim of our study is to investigate the underlying molecular mechanism of miR-142-3p in NSCLC. The expression of miR-142-3p in lung adenocarcinoma tissues and cells was detected by RT-qPCR. Next, cell proliferation, migration, invasion and apoptosis were examined by CCK-8, scratch assay, transwell assay and flow cytometry in A549 and HCC827 cells, respectively. Then, the target of miR-142-3p was predicted by targetscanHuman 7.2 and confirmed using dual-luciferase reporter assay. Additionally, RT-qPCR and western blot were used to detect the expression of NR2F6, MMP2, MMP9 and caspase-3. The results showed that miR-142-3p expression was significantly decreased in tumor tissues and cells. Overexpression of miR-142-3p inhibited the proliferation, migration, invasion and promoted cell apoptosis in vitro, while knockdown of miR-142-3p had reversed function. Furthermore, NR2F6 was identified as a direct target of miR-142-3p, which was negatively correlated with miR-142-3p expression. Finally, miR-142-3p overexpression suppressed the expression of NR2F6, MMP2 and MMP9, but improved caspase-3 expression, while miR-142-3p knockdown got the opposite expression results. Suppressing MMP2 and MMP9 activities inhibited cell invasion. In summary, these findings indicated that miR-142-3p inhibits lung adenocarcinoma cell proliferation, migration and invasion, and enhances cell apoptosis by targeting NR2F6, suggesting that miR-142-3p may be a novel therapeutic target for lung adenocarcinoma treatment.

Epigenetic arginine methylation in breast cancer: emerging therapeutic strategies

Breast cancer is a heterogeneous disease, and the complexity of breast carcinogenesis is associated with epigenetic modification. There are several major classes of epigenetic enzymes that regulate chromatin activity. This review will focus on the nine mammalian protein arginine methyltransferases (PRMTs) and the dysregulation of PRMT expression and function in breast cancer. This class of enzymes catalyse the mono- and (symmetric and asymmetric) di-methylation of arginine residues on histone and non-histone target proteins. PRMT signalling (and R methylation) drives cellular proliferation, cell invasion and metastasis, targeting (i) nuclear hormone receptor signalling, (ii) tumour suppressors, (iii) TGF-β and EMT signalling and (iv) alternative splicing and DNA/chromatin stability, influencing the clinical and survival outcomes in breast cancer. Emerging reports suggest that PRMTs are also implicated in the development of drug/endocrine resistance providing another prospective avenue for the treatment of hormone resistance and associated metastasis. The complexity of PRMT signalling is further underscored by the degree of alternative splicing and the scope of variant isoforms (with distinct properties) within each PRMT family member. The evolution of PRMT inhibitors, and the ongoing clinical trials of PRMT inhibitors against a subgroup of solid cancers, coupled to the track record of lysine methyltransferases inhibitors in phase I/II clinical trials against cancer underscores the potential therapeutic utility of targeting PRMT epigenetic enzymes to improve survival outcomes in aggressive and metastatic breast cancer.

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 orphan nuclear receptor EAR-2 (NR2F6) inhibits hematopoietic cell differentiation and induces myeloid dysplasia in vivo

Background

In patients with myelodysplastic syndrome (MDS), bone marrow cells have an increased predisposition to apoptosis, yet MDS cells outcompete normal bone marrow (BM)-- suggesting that factors regulating growth potential may be important in MDS. We previously identified v-Erb A related-2 (EAR-2, NR2F6) as a gene involved in control of growth ability.

Methods

Bone marrow obtained from C57BL/6 mice was transfected with a retrovirus containing EAR-2-IRES-GFP. Ex vivo transduced cells were flow sorted. In some experiments cells were cultured in vitro, in other experiments cells were injected into lethally irradiated recipients, along with non-transduced bone marrow cells. Short-hairpin RNA silencing EAR-2 was also introduced into bone marrow cells cultured ex vivo.

Results

Here, we show that EAR-2 inhibits maturation of normal BM in vitro and in vivo and that EAR-2 transplant chimeras demonstrate key features of MDS. Competitive repopulation of lethally irradiated murine hosts with EAR-2-transduced BM cells resulted in increased engraftment and increased colony formation in serial replating experiments. Recipients of EAR-2-transduced grafts had hypercellular BM, erythroid dysplasia, abnormal localization of immature precursors and increased blasts; secondary transplantation resulted in acute leukemia. Animals were cytopenic, having reduced numbers of erythrocytes, monocytes and granulocytes. Suspension culture confirmed that EAR-2 inhibits granulocytic and monocytic differentiation, while knockdown induced granulocytic differentiation. We observed a reduction in the number of BFU-E and CFU-GM colonies and the size of erythroid and myeloid colonies. Serial replating of transduced hematopoietic colonies revealed extended replating potential in EAR-2-overexpressing BM, while knockdown reduced re-plating ability. EAR-2 functions by recruitment of histone deacetylases, and inhibition of differentiation in 32D cells is dependent on the DNA binding domain.

Conclusions

This data suggest that NR2F6 inhibits maturation of normal BM in vitro and in vivo and that the NR2F6 transplant chimera system demonstrates key features of MDS, and could provide a mouse model for MDS.

Interleukin-24 (IL24) Is Suppressed by PAX3-FOXO1 and Is a Novel Therapy for Rhabdomyosarcoma

Alveolar rhabdomyosarcoma (ARMS) patients have a poor prognosis, and this is primarily due to overexpression of the oncogenic fusion protein PAX3-FOXO1. Results of RNA-sequencing studies show that PAX3-FOXO1 represses expression of interleukin-24 (IL24), and these two genes are inversely expressed in patient tumors. PAX3-FOXO1 also regulates histone deacetylase 5 (HDAC5) in ARMS cells, and results of RNA interference studies confirmed that PAX3-FOXO1-mediated repression of IL24 is HDAC5-dependent. Knockdown of PAX3-FOXO1 decreases ARMS cell proliferation, survival, and migration, and we also observed similar responses in cells after overexpression of IL24, consistent with results reported for this tumor suppressor-like cytokine in other solid tumors. We also observed in double knockdown studies that the inhibition of ARMS cell proliferation, survival, and migration after knockdown of PAX3-FOXO1 was significantly (>75%) reversed by knockdown of IL24. Adenoviral-expressed IL24 was directly injected into ARMS tumors in athymic nude mice, and this resulted in decreased tumor growth and weight. Because adenoviral IL24 has already successfully undergone phase I in clinical trials, this represents an alternative approach (alone and/or combination) for treating ARMS patients who currently undergo cytotoxic drug therapies.

RORα and RORγ expression inversely correlates with human melanoma progression

The retinoic acid-related orphan receptors (RORs) regulate several physiological and pathological processes, including immune functions, development and cancer. To study the potential role of RORs in melanoma progression, we analysed RORα and RORγ expression in nevi and primary melanomas and non-lesional skin and metastases in relation to melanoma clinico-pathomorphological features. The expression of RORα and RORγ was lower in melanomas than in nevi and decreased during melanoma progression, with lowest levels found in primary melanomas at stages III and IV and in melanoma metastases. Their expression correlated with pathomorphological pTNM parameters being low in aggressive tumors and being high in tumors showing histological markers of good prognosis. Higher nuclear levels of RORα and RORγ and of cytoplasmic RORγ correlated with significantly longer overall and disease free survival time. Highly pigmented melanomas showed significantly lower level of nuclear RORs. This study shows that human melanoma development and aggressiveness is associated with decreased expression of RORα and RORγ, suggesting that RORs could be important in melanoma progression and host responses against the tumor. Furthermore, it suggests that RORα and RORγ might constitute a novel druggable target in anti-melanoma management using tumor suppressor gene therapy restoring their normal functions.

Nuclear receptor NR2F6 inhibition potentiates responses to PD-L1/PD-1 cancer immune checkpoint blockade

Analyzing mouse tumor models in vivo, human T cells ex vivo, and human lung cancer samples, we provide direct evidence that NR2F6 acts as an immune checkpoint. Genetic ablation of Nr2f6, particularly in combination with established cancer immune checkpoint blockade, efficiently delays tumor progression and improves survival in experimental mouse models. The target genes deregulated in intratumoral T lymphocytes upon genetic ablation of Nr2f6 alone or together with PD-L1 blockade reveal multiple advantageous transcriptional alterations. Acute Nr2f6 silencing in both mouse and human T cells induces hyper-responsiveness that establishes a non-redundant T-cell-inhibitory function of NR2F6. NR2F6 protein expression in T-cell-infiltrating human NSCLC is upregulated in 54% of the cases (n = 303) and significantly correlates with PD-1 and CTLA-4 expression. Our data define NR2F6 as an intracellular immune checkpoint that suppresses adaptive anti-cancer immune responses and set the stage for clinical validation of targeting NR2F6 for next-generation immuno-oncological regimens.

Immune checkpoints blockade (ICB) is a viable anti-cancer strategy. Here the authors show that nuclear receptor NR2F6 acts as an immune checkpoint in T cells and, using mouse models and human T cells, they show NR2F6 inhibition might improve current ICB therapy or work as an alternative therapeutic strategy.

LRH-1 expression patterns in breast cancer tissues are associated with tumour aggressiveness

The significance and regulation of liver receptor homologue 1 (LRH-1, NR5A2), a tumour-promoting transcription factor in breast cancer cell lines, is unknown in clinical breast cancers. This study aims to determine LRH-1/NR5A2 expression in breast cancers and relationship with DNA methylation and tumour characteristics. In The Cancer Genome Atlas breast cancer cohort NR5A2 expression was positively associated with intragenic CpG island methylation (1.4-fold expression for fully methylated versus not fully methylated, p=0.01) and inversely associated with promoter CpG island methylation (0.6-fold expression for fully methylated versus not fully methylated, p=0.036). LRH-1 immunohistochemistry of 329 invasive carcinomas and ductal carcinoma in situ (DCIS) was performed. Densely punctate/coarsely granular nuclear reactivity was significantly associated with high tumour grade (p<0.005, p=0.033 in invasive carcinomas and DCIS respectively), negative estrogen receptor status (p=0.008, p=0.038 in overall cohort and invasive carcinomas, respectively), negative progesterone receptor status (p=0.003, p=0.013 in overall cohort and invasive carcinomas, respectively), HER2 amplification (overall cohort p=0.034) and non-luminal intrinsic subtype (p=0.018, p=0.038 in overall cohort and invasive carcinomas, respectively). These significant associations of LRH-1 protein expression with tumour phenotype suggest that LRH-1 is an important indicator of tumour biology in breast cancers and may be useful in risk stratification.