ERK/MAPK regulates ERRγ expression, transcriptional activity and receptor-mediated tamoxifen resistance in ER+ breast cancer

A large-scale cancer-specific protein-DNA interaction network

Cancer development and progression are generally associated with gene dysregulation, often resulting from changes in the transcription factor (TF) sequence or expression. Identifying key TFs involved in cancer gene regulation provides a framework for potential new therapeutics. This study presents a large-scale cancer gene TF-DNA interaction network, as well as an extensive promoter clone resource for future studies. Highly connected TFs bind to promoters of genes associated with either good or poor cancer prognosis, suggesting that strategies aimed at shifting gene expression balance between these two prognostic groups may be inherently complex. However, we identified potential for oncogene-targeted therapeutics, with half of the tested oncogenes being potentially repressed by influencing specific activators or bifunctional TFs. Finally, we investigate the role of intrinsically disordered regions within the key cancer-related TF ESR1 in DNA binding and transcriptional activity, and found that these regions can have complex trade-offs in TF function. Altogether, our study broadens our knowledge of the TFs involved in cancer gene regulation and provides a valuable resource for future studies and therapeutics.

Exploring the impact of estrogen-related receptor gamma on metabolism and disease

Estrogen-related receptor gamma (ERRγ) is a member of the ERR orphan nuclear receptor family which possesses three subtypes, α, β, and γ. ERRγ is reportedly predominantly expressed in metabolically active tissues and cells, which promotes positive and negative effects in different tissues. ERRγ overexpression in the liver, pancreas, and thyroid cells is related to liver cancer, oxidative stress, reactive oxygen species (ROS) regulation, and carcinoma. Reduced ERRγ expression in the brain, immune cells, tumor cells, and energy metabolism causes neurological dysfunction, gastric cancer, and obesity. ERRγ is a constitutive receptor; however, its transcriptional activity also depends on co-regulators, agonists, and antagonists, which, when after forming a complex, can play a role in targeting and treating diseases. Moreover, ERRγ has proven crucial in regulating cellular and metabolic activity. However, many functions mediated via ERRγ remain unknown and require further exploration. Hence, considering the importance of ERRγ, this review focuses on the critical findings and interactions between ERRγ and co-regulators, agonists, and antagonists alongside its relationship with downstream and upstream signaling pathways and diseases. This review highlights new findings and provides a path to understanding the current ideas and future studies on ERRγ-mediated cellular activity.

DY131 activates ERRγ/TFAM axis to protect against metabolic disorders and acute kidney injury

Renal tubular injury is considered as the main pathological feature of acute kidney injury (AKI), and mitochondrial dysfunction in renal tubular cells is implicated in the pathogenesis of AKI. The estrogen-related receptor γ (ERRγ) is a member of orphan nuclear receptors which plays a regulatory role in mitochondrial biosynthesis, energy metabolism and many metabolic pathways. Online datasets showed a dominant expression of ERRγ in renal tubules, but the role of ERRγ in AKI is still unknown. In the present study, we investigated the role of ERRγ in the pathogenesis of AKI and the therapeutic efficacy of ERRγ agonist DY131 in several murine models of AKI. ERRγ expression was reduced in kidneys of AKI patients and AKI murine models along with a negative correlation to the severity of AKI. Consistently, silencing ERRγ in vitro enhanced cisplatin-induced tubular cells apoptosis, while ERRγ overexpression in vivo utilizing hydrodynamic-based tail vein plasmid delivery approach alleviated cisplatin-induced AKI. ERRγ agonist DY131 could enhance the transcriptional activity of ERRγ and ameliorate AKI in various murine models. Moreover, DY131 attenuated the mitochondrial dysfunction of renal tubular cells and metabolic disorders of kidneys in AKI, and promoted the expression of the mitochondrial transcriptional factor A (TFAM). Further investigation showed that TFAM could be a target gene of ERRγ and DY131 might ameliorate AKI by enhancing ERRγ-mediated TFAM expression protecting mitochondria. These findings highlighted the protective effect of DY131 on AKI, thus providing a promising therapeutic strategy for AKI.

Estrogen-related receptor alpha promotes thyroid tumor cell survival via a tumor subtype-specific regulation of target gene networks

Mortalin (encoded by HSPA9) is a mitochondrial chaperone often overexpressed in cancer through as-yet-unknown mechanisms. By searching different RNA-sequencing datasets, we found that ESRRA is a transcription factor highly correlated with HSPA9 in thyroid cancer, especially in follicular, but not C cell-originated, tumors. Consistent with this correlation, ESRRA depletion decreased mortalin expression only in follicular thyroid tumor cells. Further, ESRRA expression and activity were relatively high in thyroid tumors with oncocytic characteristics, wherein ESRRA and mortalin exhibited relatively high functional overlap. Mechanistically, ESRRA directly regulated HSPA9 transcription through a novel ESRRA-responsive element located upstream of the HSPA9 promoter. Physiologically, ESRRA depletion suppressed thyroid tumor cell survival via caspase-dependent apoptosis, which ectopic mortalin expression substantially abrogated. ESRRA depletion also effectively suppressed tumor growth and mortalin expression in the xenografts of oncocytic or ESRRA-overexpressing human thyroid tumor cells in mice. Notably, our Bioinformatics analyses of patient data revealed two ESRRA target gene clusters that contrast oncocytic-like and anaplastic features of follicular thyroid tumors. These findings suggest that ESRRA is a tumor-specific regulator of mortalin expression, the ESRRA-mortalin axis has higher significance in tumors with oncocytic characteristics, and ESRRA target gene networks can refine molecular classification of thyroid cancer.

Proteomic profiling reveals that ESR1 mutations enhance cyclin-dependent kinase signaling

Three quarters of all breast cancers express the estrogen receptor (ER, ESR1 gene), which promotes tumor growth and constitutes a direct target for endocrine therapies. ESR1 mutations have been implicated in therapy resistance in metastatic breast cancer, in particular to aromatase inhibitors. ESR1 mutations promote constitutive ER activity and affect other signaling pathways, allowing cancer cells to proliferate by employing mechanisms within and without direct regulation by the ER. Although subjected to extensive genetic and transcriptomic analyses, understanding of protein alterations remains poorly investigated. Towards this, we employed an integrated mass spectrometry based proteomic approach to profile the protein and phosphoprotein differences in breast cancer cell lines expressing the frequent Y537N and Y537S ER mutations. Global proteome analysis revealed enrichment of mitotic and immune signaling pathways in ER mutant cells, while phosphoprotein analysis evidenced enriched activity of proliferation associated kinases, in particular CDKs and mTOR. Integration of protein expression and phosphorylation data revealed pathway-dependent discrepancies (motility vs proliferation) that were observed at varying degrees across mutant and wt ER cells. Additionally, protein expression and phosphorylation patterns, while under different regulation, still recapitulated the estrogen-independent phenotype of ER mutant cells. Our study is the first proteome-centric characterization of ESR1 mutant models, out of which we confirm estrogen independence of ER mutants and reveal the enrichment of immune signaling pathways at the proteomic level.

ERRα: unraveling its role as a key player in cell migration

Cell migration is essential throughout the life of multicellular organisms, and largely depends on the spatial and temporal regulation of cytoskeletal dynamics, cell adhesion and signal transduction. Interestingly, Estrogen-related receptor alpha (ERRα) has been identified as a major regulator of cell migration in both physiological and pathological conditions. ERRα is an orphan member of the nuclear hormone receptor superfamily of transcription factors and displays many biological functions. ERRα is a global regulator of energy metabolism, and it is also highly involved in bone homeostasis, development, differentiation, immunity and cancer progression. Importantly, in some instances, the regulation of these biological processes relies on the ability to orchestrate cell movements. Therefore, this review describes how ERRα-mediated cell migration contributes not only to tissue homeostasis but also to tumorigenesis and metastasis, and highlights the molecular and cellular mechanisms by which ERRα finely controls the cell migratory potential.

A large-scale cancer-specific protein-DNA interaction network

Cancer development and progression are generally associated with dysregulation of gene expression, often resulting from changes in transcription factor (TF) sequence or expression. Identifying key TFs involved in cancer gene regulation provides a framework for potential new therapeutics. This study presents a large-scale cancer gene TF-DNA interaction network as well as an extensive promoter clone resource for future studies. Most highly connected TFs do not show a preference for binding to promoters of genes associated with either good or poor cancer prognosis, suggesting that emerging strategies aimed at shifting gene expression balance between these two prognostic groups may be inherently complex. However, we identified potential for oncogene targeted therapeutics, with half of the tested oncogenes being potentially repressed by influencing specific activator or bifunctional TFs. Finally, we investigate the role of intrinsically disordered regions within the key cancer-related TF estrogen receptor ɑ (ESR1) on DNA binding and transcriptional activity, and found that these regions can have complex trade-offs in TF function. Altogether, our study not only broadens our knowledge of TFs involved in the cancer gene regulatory network but also provides a valuable resource for future studies, laying a foundation for potential therapeutic strategies targeting TFs in cancer.

Mitogen-Activated Protein Kinase and Exploratory Nuclear Receptor Crosstalk in Cancer Immunotherapy

The three major mitogen-activated protein kinase (MAPK) pathways (ERK1/2, p38, and JNK/SAPK) are upstream regulators of the nuclear receptor superfamily (NRSF). These ligand-activated transcription factors are divided into subclasses comprising receptors for endocrine hormones, metabolic compounds (e.g., vitamins, diet), xenobiotics, and mediators released from host immune reactions such as tissue injury and inflammation. These internal and external cues place the NRSF at the frontline as sensors and translators of information from the environment towards the genome. For most of the former "orphan" receptors, physiological and synthetic ligands have been identified, opening intriguing opportunities for combination therapies with existing cancer medications. Hitherto, only preclinical data are available, warranting further validation in clinical trials in patients. The current review summarized the existing literature covering the expression and function of NRSF subclasses in human solid tumors and hematopoietic malignancies and their modulatory effects on innate (e.g., macrophages, dendritic cells) and adaptive (i.e., T cell subsets) immune cells, encouraging mechanistic and pharmacological studies in combination with current clinically approved therapeutics against immune checkpoint molecules (e.g., PD1).

SRSF5 Regulates the Expression of BQ323636.1 to Modulate Tamoxifen Resistance in ER-Positive Breast Cancer

About 70% of breast cancer patients are oestrogen receptor-positive (ER +ve). Adjuvant endocrine therapy using tamoxifen (TAM) is an effective approach for preventing local recurrence and metastasis. However, around half of the patients will eventually develop resistance. Overexpression of BQ323636.1 (BQ) is one of the mechanisms that confer TAM resistance. BQ is an alternative splice variant of NCOR2. The inclusion of exon 11 generates mRNA for NCOR2, while the exclusion of exon 11 produces mRNA for BQ. The expression of SRSF5 is low in TAM-resistant breast cancer cells. Modulation of SRSF5 can affect the alternative splicing of NCOR2 to produce BQ. In vitro and in vivo studies confirmed that the knockdown of SRSF5 enhanced BQ expression, and conferred TAM resistance; in contrast, SRSF5 overexpression reduced BQ expression and, thus, reversed TAM resistance. Clinical investigation using a tissue microarray confirmed the inverse correlation of SRSF5 and BQ. Low SRSF5 expression was associated with TAM resistance, local recurrence and metastasis. Survival analyses showed that low SRSF5 expression was associated with poorer prognosis. We showed that SRPK1 can interact with SRSF5 to phosphorylate it. Inhibition of SRPK1 by a small inhibitor, SRPKIN-1, suppressed the phosphorylation of SRSF5. This enhanced the proportion of SRSF5 interacting with exon 11 of NCOR2, reducing the production of BQ mRNA. As expected, SRPKIN-1 reduced TAM resistance. Our study confirms that SRSF5 is essential for BQ expression. Modulating the activity of SRSF5 in ER +ve breast cancer will be a potential approach to combating TAM resistance.

Estrogen-related receptor alpha drives mitochondrial biogenesis and resistance to neoadjuvant chemoradiation in esophageal cancer

Neoadjuvant chemoradiotherapy (nCRT) improves outcomes in resectable esophageal adenocarcinoma (EAC), but acquired resistance precludes long-term efficacy. Here, we delineate these resistance mechanisms. RNA sequencing on matched patient samples obtained pre-and post-neoadjuvant treatment reveal that oxidative phosphorylation was the most upregulated of all biological programs following nCRT. Analysis of patient-derived models confirms that mitochondrial content and oxygen consumption strongly increase in response to nCRT and that ionizing radiation is the causative agent. Bioinformatics identifies estrogen-related receptor alpha (ESRRA) as the transcription factor responsible for reprogramming, and overexpression and silencing of ESRRA functionally confirm that its downstream metabolic rewiring contributes to resistance. Pharmacological inhibition of ESRRA successfully sensitizes EAC organoids and patient-derived xenografts to radiation. In conclusion, we report a profound metabolic rewiring following chemoradiation and demonstrate that its inhibition resensitizes EAC cells to radiation. These findings hold broader relevance for other cancer types treated with radiation as well.

Emerging Roles of COX7RP and Mitochondrial Oxidative Phosphorylation in Breast Cancer

Metabolic alterations are critical events in cancers, which often contribute to tumor pathophysiology. While aerobic glycolysis is a known characteristic of cancer-related metabolism, recent studies have shed light on mitochondria-related metabolic pathways in cancer biology, including oxidative phosphorylation (OXPHOS), amino acid and lipid metabolism, nucleic acid metabolism, and redox regulation. Breast cancer is the most common cancer in women; thus, elucidation of breast cancer-related metabolic alteration will help to develop cancer drugs for many patients. We here aim to define the contribution of mitochondrial metabolism to breast cancer biology. The relevance of OXPHOS in breast cancer has been recently defined by the discovery of COX7RP, which promotes mitochondrial respiratory supercomplex assembly and glutamine metabolism: the latter is also shown to promote nucleic acid and fatty acid biosynthesis as well as ROS defense regulation. In this context, the estrogen-related receptor (ERR) family nuclear receptors and collaborating coactivators peroxisome proliferator-activated receptor-γ coactivator-1 (PGC-1) are essential transcriptional regulators for both energy production and cancer-related metabolism. Summarizing recent findings of mitochondrial metabolism in breast cancer, this review will aim to provide a clue for the development of alternative clinical management by modulating the activities of responsible molecules involved in disease-specific metabolic alterations.

Naringin Improves Osteoblast Mineralization and Bone Healing and Strength through Regulating Estrogen Receptor Alpha-Dependent Alkaline Phosphatase Gene Expression

Phytoestrogens are strongly recommended for treating osteoporosis. Our previous study showed that naringin, a citrus flavonoid, can enhance the bone mass in ovariectomized rats. In this study, we further elucidated the mechanisms of naringin-induced osteoblast maturation and bone healing. Treatment of human osteoblasts with naringin increased cell viability and proliferation. In parallel, exposure to naringin enhanced translocation of estrogen receptor alpha (ERα) to nuclei and its transactivation activity. Sequentially, naringin induced alkaline phosphatase (ALP) mRNA and protein expression and its enzyme activity. Pretreatment with methylpiperidinopyrazole (MPP), a specific inhibitor of ERα, attenuated naringin-induced augmentations in ERα transactivation activity, ALP gene expression, and cell mineralization. The beneficial effects of naringin were also confirmed in mouse MC3T3-E1 cells. Moreover, administration of mice with a bone defect with naringin increased levels of ERα and ALP in damaged sites and simultaneously enhanced the healing rate and bone strength. Nevertheless, treatment with MPP weakened naringin-triggered expression of ERα and ALP and improved bone healing and mass. Therefore, naringin could improve osteoblast mineralization and bone healing via regulating ERα-dependent ALP gene expression. Naringin can be clinically applied for treatment of osteoporosis-related bone diseases.

Lemur tyrosine kinase-3 (LMTK3) induces chemoresistance to cetuximab in colorectal cancer via the ERK/MAPK pathway

As an oncogenic kinase in multiple cancers, LMTK3 was deeply implicated in cancer pathogenesis. Nevertheless, its biological function in colorectal cancer (CRC) is still unclear. In this study, LMTK3 mRNA expression was assessed by RT-qPCR. LMTK3, phospho-ERK1/2 (p-ERK1/2), ERK1/2, and cleaved caspase-3 protein levels were detected by western blotting. Cetuximab (CTX)-resistant CRC cell models were constructed to investigate the mechanism of LMTK3-regulated CTX resistance in CRC. CTX half-maximal inhibitory concentration (IC₅₀), viability, apoptosis, cell cycle, migration, and invasion of CRC cells were analyzed via Cell Counting Kit-8 (CCK-8), flow cytometry, wound healing, and transwell assays. We found LMTK3 was distinctly upregulated in CRC tissues and cells, particularly in CTX-resistant CRC tissues and cells. LMTK3 inhibition lowered CTX half-maximal inhibitory concentration (IC₅₀) value, inhibited cell viability, induced cell apoptosis, triggered cell-cycle arrest, and impaired cell metastatic capability in CTX-resistant CRC cells. Moreover, we also demonstrated that LMTK3 induced CTX resistance in CRC via the activation of ERK/MAPK signaling in vitro. These results suggested a novel molecular mechanism by which LMTK3 participates in the development of CTX resistance in CRC.

Rosmanol induces breast cancer cells apoptosis by regulating PI3K/AKT and STAT3/JAK2 signaling pathways

Breast cancer is one of the most frequently diagnosed cancers amongst women; however, there is currently no effective treatment. Natural compounds are considered to contribute to cancer prevention and have a pivotal role in modulating apoptosis. Rosmanol is a phenolic diterpene compound with antioxidant and anti-inflammatory properties. In the present study, the effects of Rosmanol on breast cancer cell proliferation/apoptosis were investigated, and it was demonstrated that it inhibited the proliferation of MCF-7 and MDA-MB 231 cells but did not have a significant effect on normal human breast MCF-10A cells. In addition, the apoptotic process was accelerated by Rosmanol, through mitochondrial pathways and reactive oxygen species (ROS) production caused by DNA damage, which function further demonstrated by the attenuation and addition of the ROS inhibitor, N-acetyl-cysteine. It was also demonstrated that Rosmanol accelerated cell apoptosis, and arrested breast cancer cells in the S phase. Moreover, Rosmanol inhibited proliferation and promoted apoptosis of cancer cells via the inhibition of ERK and STAT3 signals, attributable to the increase in p-p38, the overexpression of protein inhibitor of activated STAT3, and the decrease in PI3K/AKT, ERK and JAK2/STAT3.

Progress in the Understanding of the Mechanism of Tamoxifen Resistance in Breast Cancer

Tamoxifen is a drug commonly used in the treatment of breast cancer, especially for postmenopausal patients. However, its efficacy is limited by the development of drug resistance. Downregulation of estrogen receptor alpha (ERα) is an important mechanism of tamoxifen resistance. In recent years, with progress in research into the protective autophagy of drug-resistant cells and cell cycle regulators, major breakthroughs have been made in research on tamoxifen resistance. For a better understanding of the mechanism of tamoxifen resistance, protective autophagy, cell cycle regulators, and some transcription factors and enzymes regulating the expression of the estrogen receptor are summarized in this review. In addition, recent progress in reducing resistance to tamoxifen is reviewed. Finally, we discuss the possible research directions into tamoxifen resistance in the future to provide assistance for the clinical treatment of breast cancer.

MicroRNA-381-A Key Transcriptional Regulator: Its Biological Function and Clinical Application Prospects in Cancer

MicroRNAs (miRNAs) are small non-coding RNA molecules that function by regulating messenger RNAs. Recent studies have shown that miRNAs play important roles in multiple processes of cancer development. MiR-381 is one of the most important miRNAs in cancer progression. MiR-381 is downregulated in some cancers and upregulated in other cancers, including glioma, epithelial sarcoma, and osteosarcoma. MiR-381 regulates epithelial-mesenchymal transition (EMT), chemotherapeutic resistance, radioresistance, and immune responses. Thus, miR-381 participates in tumor initiation, progression, and metastasis. Moreover, miR-381 functions in various oncogenic pathways, including the Wnt/β-catenin, AKT, and p53 pathways. Clinical studies have shown that miR-381 could be considered a biomarker or a novel prognostic factor. Here, we summarize the present studies on the role of miR-381 in cancer development, including its biogenesis and various affected signaling pathways, and its clinical application prospects. MiR-381 expression is associated with tumor stage and survival time, making miR-381 a novel prognostic factor.

Sophoridine exerts tumor-suppressive activities via promoting ESRRG-mediated β-catenin degradation in gastric cancer

Background

As a natural alkaloid product isolated from Sophora alopecuroides. L, Sophoridine reshapes gastric cancer immune microenvironment via inhibiting chemotaxis and M2 polarization of tumor-associated macrophages (TAMs). However, the exact effects and underlying mechanism of Sophoridine on gastric cancer cells remains poorly known.

Methods

The potential anti-tumor effects of Sophoridine on gastric cancer cell lines, including AGS and SGC7901 cells, were detected by CCK-8, EDU and colony forming assay, immunofluorescence, transwell assay, and flow cytometry. Molecular mechanisms of Sophoridine were investigated by siRNA transfection, nuclear/cytoplasmic extraction and western blot. The synergistic effects of Sophoridine with cisplatin on gastric cancer cells were further investigated in in vitro functional studies.

Results

Sophoridine exhibited potent tumor-suppressive activities in gastric cancer cells, including inhibition of proliferation, colony formulation, migration and invasion, as well as induction of apoptosis. In addition, we further showed that Sophoridine induced G2/M cell cycle arrest via inhibiting double-stranded DNA breaks repair and enhanced the efficacy of cisplatin in gastric cancer cells. Molecular studies further revealed that Sophoridine promoted β-catenin degradation by enhancing Estrogen-related receptor gamma (ESRRG) expression, but not depended on ubiquitination-proteasome pathway, either TRIM33-mediated (GSK3β-independent) or altered GSK3β activity, and thus exerted potent tumor-suppressive activities.

Conclusion

Sophoridine depends on targeting ESRRG/β-catenin pathway to exert tumor-suppressive activities in gastric cancer cells and enhances the anti-tumor effect of cisplatin. Our study provided the promising preclinical anti-tumor evidence for the potential application of Sophoridine against gastric cancer.

Nuclear Parkin Activates the ERRα Transcriptional Program and Drives Widespread Changes in Gene Expression Following Hypoxia

Parkin is an E3 ubiquitin ligase well-known for facilitating clearance of damaged mitochondria by ubiquitinating proteins on the outer mitochondrial membrane. However, knowledge of Parkin's functions beyond mitophagy is still limited. Here, we demonstrate that Parkin has functions in the nucleus and that Parkinson's disease-associated Parkin mutants, ParkinR42P and ParkinG430D, are selectively excluded from the nucleus. Further, Parkin translocates to the nucleus in response to hypoxia which correlates with increased ubiquitination of nuclear proteins. The serine-threonine kinase PINK1 is responsible for recruiting Parkin to mitochondria, but translocation of Parkin to the nucleus occurs independently of PINK1. Transcriptomic analyses of HeLa cells overexpressing wild type or a nuclear-targeted Parkin revealed that during hypoxia, Parkin contributes to both increased and decreased transcription of genes involved in regulating multiple metabolic pathways. Furthermore, a proteomics screen comparing ubiquitinated proteins in hearts from Parkin-/- and Parkin transgenic mice identified the transcription factor estrogen-related receptor α (ERRα) as a potential Parkin target. Co-immunoprecipitation confirmed that nuclear-targeted Parkin interacts with and ubiquitinates ERRα. Further analysis uncovered that nuclear Parkin increases the transcriptional activity of ERRα. Overall, our study supports diverse roles for Parkin and demonstrates that nuclear Parkin regulates transcription of genes involved in multiple metabolic pathways.

Quantitative hormone receptor (HR) expression and gene expression analysis in HR+ inflammatory breast cancer (IBC) vs non-IBC

Background

The purpose of this study was to determine the prognostic role of hormone receptor (HR) on inflammatory breast cancer (IBC) to elucidate its aggressive biological behavior.

Methods

We evaluated the expression of estrogen receptor (ER) and progesterone receptor (PR) by immunohistochemical staining and determined the predictive and prognostic role of HR expression on 189 patients with HR+/HER2– IBC and 677 patients with HR+/HER2– stage III non-IBC. Furthermore, we performed gene expression (GE) analyses on 137 patients with HR+/HER2– IBC and 252 patients with HR+/HER2– non-IBC to detect genes that are specifically overexpressed in IBC.

Results

The expression of ER% was significantly associated with longer distant disease-free survival and overall survival. However, there was no significant relationship between ER% and neoadjuvant chemotherapy outcome. In the GE study, 84 genes were identified as significantly distinguishing HR+ IBC from non-IBC. Among the top 15 canonical pathways expressed in IBC, the ERK/MAPK, PDGF, insulin receptor, and IL-7 signaling pathways were associated with the ER signaling pathway. Upregulation of the MYC gene was observed in three of these four pathways. Furthermore, HR+/HER2– IBC had significantly higher MYC amplification, and the genetic alteration was associated with poor survival outcome.

Conclusions

Higher ER expression was significantly associated with improved survival in both HR+/HER2– IBC and HR+/HER2– stage III non-IBC patients. HR+/HER2– IBC had several activated pathways with MYC upregulation, and the genetic alteration was associated with poor survival outcome. The results indicate that MYC may be a key gene for understanding the biology of HR+/HER2– IBC.

Circular RNA Expression Profiles in Nasopharyngeal Carcinoma by Sequence Analysis

Circular RNAs (circRNAs), as a burgeoning sort of non-coding RNAs (ncRNAs), can regulate the expression of parental genes as miRNA sponges. This study was designed to explore the circRNA expression profile of nasopharyngeal carcinoma (NPC). High-throughput sequencing was performed to identify the circRNA expression profile of NPC patients compared with healthy controls. A total of 93 upregulated circRNAs and 77 downregulated circRNAs were identified. The expression levels of the top three upregulated and three downregulated circRNAs annotated by circBase were validated by quantitative real-time PCR (qRT-PCR). GO and KEGG analyses showed that these differentially expressed circRNAs were potentially implicated in NPC pathogenesis. CircRNA-miRNA-target gene network analysis revealed a potential mechanism that hsa_circ_0002375 (circKITLG) may be involved in NPC through sponging up miR-3198 and interfering with its downstream targets. Silencing of circKITLG inhibited NPC cell proliferation, migration, and invasion in vitro. This study provides a leading and fundamental circRNA expression profile of NPC.

The Endocrine Disruptor Bisphenol A (BPA) Exerts a Wide Range of Effects in Carcinogenesis and Response to Therapy

BACKGROUND

Bisphenol A (BPA) is a synthetic plasticizer that is commonly used in the production of polycarbonate plastics and epoxy resins. Human exposure occurs when BPA migrates from food and beverage containers into the contents when heated or even under normal conditions of use. BPA exerts endocrine disruptor action due to its weak binding affinity for the estrogen receptors ERα and ERβ. BPA exerts other effects by activating the membrane receptor GPER (GPR30) and/or other receptors such as the estrogen-related receptors (ERRs).

OBJECTIVE

This review summarizes emerging data on BPA and cancer. These include data linking exposure to BPA with an increased risk of hormone-related cancers such as those of the ovary, breast, prostate, and even colon cancer. BPA can also induce resistance to various chemotherapeutics such as doxorubicin, cisplatin, and vinblastine in vitro. The development of chemoresistance to available therapeutics is an emerging significant aspect of BPA toxicity because it worsens the prognosis of many tumors.

CONCLUSION

Recent findings support a causal role of BPA at low levels in the development of cancers and in dictating their response to cytotoxic therapy. Accurate knowledge and consideration of these issues would be highly beneficial to cancer prevention and management.

Endocrinotherapy resistance of prostate and breast cancer: Importance of the NF‑κB pathway (Review)

Prostate cancer (PCa) and breast cancer (BCa) are two common sex hormone‑related cancer types with high rates of morbidity, and are leading causes of cancer death globally in men and women, respectively. The biological function of androgen or estrogen is a key factor for PCa or BCa tumorigenesis, respectively. Nevertheless, after hormone deprivation therapy, the majority of patients ultimately develop hormone‑independent malignancies that are resistant to endocrinotherapy. It is widely recognized, therefore, that understanding of the mechanisms underlying the process from hormone dependence towards hormone independence is critical to discover molecular targets for the control of advanced PCa and BCa. This review aimed to dissect the important mechanisms involved in the therapeutic resistance of PCa and BCa. It was concluded that activation of the NF‑κB pathway is an important common mechanism for metastasis and therapeutic resistance of the two types of cancer; in particular, the RelB‑activated noncanonical NF‑κB pathway appears to be able to lengthen and strengthen NF‑κB activity, which has been a focus of recent investigations.

Insights into the activation mechanism of human estrogen-related receptor γ by environmental endocrine disruptors

The estrogen-related receptor γ (ERRγ, NR3B3) is a constitutively active nuclear receptor which has been proposed to act as a mediator of the low-dose effects of a number of environmental endocrine-disrupting chemicals (EDCs) such as the xenoestrogen bisphenol-A (BPA). To better characterize the ability of exogenous compounds to bind and activate ERRγ, we used a combination of cell-based, biochemical, structural and computational approaches. A purposely created stable cell line allowed for the determination of the EC50s for over 30 environmental ERRγ ligands, including previously unknown ones. Interestingly, affinity constants (Kds) of the most potent compounds measured by isothermal titration calorimetry were in the 50-500 nM range, in agreement with their receptor activation potencies. Crystallographic analysis of the interaction between the ERRγ ligand-binding domain (LBD) and compounds of the bisphenol, alkylphenol and naphthol families revealed a partially shared binding mode and minimal alterations of the receptor conformation upon ligand binding. Further biophysical characterizations coupled to molecular dynamics simulations suggested a mechanism through which ERRγ ligands would exhibit their agonistic properties by preserving the transcriptionally active form of the receptor while rigidifying some loop regions with associated functions. This unique mechanism contrasts with the classical one involving a ligand-induced repositioning and stabilization of the C-terminal activation helix H12.

Next-generation unnatural monosaccharides reveal that ESRRB O-GlcNAcylation regulates pluripotency of mouse embryonic stem cells

Unnatural monosaccharides such as azidosugars that can be metabolically incorporated into cellular glycans are currently used as a major tool for glycan imaging and glycoproteomic profiling. As a common practice to enhance membrane permeability and cellular uptake, the unnatural sugars are per-O-acetylated, which, however, can induce a long-overlooked side reaction, non-enzymatic S-glycosylation. Herein, we develop 1,3-di-esterified N-azidoacetylgalactosamine (GalNAz) as next-generation chemical reporters for metabolic glycan labeling. Both 1,3-di-O-acetylated GalNAz (1,3-Ac₂GalNAz) and 1,3-di-O-propionylated GalNAz (1,3-Pr₂GalNAz) exhibit high efficiency for labeling protein O-GlcNAcylation with no artificial S-glycosylation. Applying 1,3-Pr₂GalNAz in mouse embryonic stem cells (mESCs), we identify ESRRB, a critical transcription factor for pluripotency, as an O-GlcNAcylated protein. We show that ESRRB O-GlcNAcylation is important for mESC self-renewal and pluripotency. Mechanistically, ESRRB is O-GlcNAcylated by O-GlcNAc transferase at serine 25, which stabilizes ESRRB, promotes its transcription activity and facilitates its interactions with two master pluripotency regulators, OCT4 and NANOG.

Per-O-acetylated unnatural monosaccharides are popular tools for glycan labeling in live cells but can undergo unwanted side reactions with cysteines. Here, the authors develop unnatural sugars in a partially esterified form that are inert towards cysteines, and use them to probe O-GlcNAcylation in mESCs.

ESRRG promoter hypermethylation as a diagnostic and prognostic biomarker in laryngeal squamous cell carcinoma

Background

Estrogen‐related receptor gamma (ESRRG) has been identified as a tumor suppressor gene in several cancers. We aimed to evaluate ESRRG promoter methylation in laryngeal squamous cell carcinoma (LSCC) and its relative clinical value in LSCC.

Methods

Bisulfite pyrosequencing assays were performed on 91 pairs of tumor and paracancer tissues from LSCC patients in China. The diagnostic value and overall survival (OS) were analyzed descriptively by receiver operating characteristic (ROC) curves and the Kaplan‐Meier methods, respectively.

Results

The ESRRG promoter was more frequently hypermethylated in tumor tissues than in adjacent tissues (P < 0.01). ESRRG promoter methylation was significantly increased in advanced T stage tumors (P < 0.01) and advanced clinical stage patients (P < 0.01). Moreover, the area under the ROC curve (AUC) value (0.81) indicated high discrimination accuracy. Furthermore, ESRRG hypermethylation was associated with poor OS, as confirmed by Kaplan‐Meier survival curves (P < 0.01).

Conclusion

Our study indicated that ESRRG promoter hypermethylation contributed to LSCC‐related risks, primarily tumor progression and survival prognosis, in patients. ESRRG promoter methylation could, therefore, be a diagnostic and prognostic biomarker in LSCC.

The PGC-1/ERR network and its role in precision oncology

Transcriptional regulators include a superfamily of nuclear proteins referred to as co-activators and co-repressors, both of which are involved in controlling the functions of several nuclear receptors (NRs). The Nuclear Receptor Signaling Atlas (NURSA) has cataloged the composition of NRs, co-regulators, and ligands present in the human cell and their effort has been identified in more than 600 potential molecules. Given the importance of co-regulators in steroid, retinoid, and thyroid hormone signaling networks, hypothesizing that NRs/co-regulators are implicated in a wide range of pathologies are tempting. The co-activators known as peroxisome proliferator-activated receptor gamma co-activator 1 (PGC-1) and their key nuclear partner, the estrogen-related receptor (ERR), are emerging as pivotal transcriptional signatures that regulate an extremely broad repertoire of mitochondrial and metabolic genes, making them very attractive drug targets for cancer. Several studies have provided an increased understanding of the functional and structural biology of nuclear complexes. However, more comprehensive work is needed to create different avenues to explore the therapeutic potential of NRs/co-activators in precision oncology. Here, we discuss the emerging data associated with the structure, function, and molecular biology of the PGC-1/ERR network and address how the concepts evolving from these studies have deepened our understanding of how to develop more effective treatment strategies. We present an overview that underscores new biological insights into PGC-1/ERR to improve cancer outcomes against therapeutic resistance. Finally, we discuss the importance of exploiting new technologies such as single-particle cryo-electron microscopy (cryo-EM) to develop a high-resolution biological structure of PGC-1/ERR, focusing on novel drug discovery for precision oncology.

miR-381 induces sensitivity of breast cancer cells to doxorubicin by inactivation of MAPK signaling via FYN

The emergence of drug resistance is still a daunting challenge for the effective therapy of cancer patients. miRNAs have been elucidated as an important regulator in chemoresistance of anti-cancer drugs. miR-381 is found to exert tumor-suppressive effect in breast cancer. However, its role in modulating the sensitivity of doxorubicin (DOX) remains unknown. In this study, we found that miR-381 expression was down-regulated in DOX-resistant breast cancer cells. miR-381 overexpression increased DOX sensitivity and enhanced DOX-induced apoptosis in breast cancer cells. Moreover, miR-381 could directly target FYN to suppress its expression. Additionally, FYN knockdown displayed similar effect on DOX sensitivity as miR-381 up-regulation. Furthermore, FYN overexpression partly reversed miR-381-induced sensitivity to DOX. Finally, enforced expression of miR-381 also improved DOX sensitivity of breast cancer cells in vivo. In summary, miR-381 inactivated MAPK signaling by down-regulating FYN, thereby promoting the chemosensitization of breast cancer cells to DOX. Therefore, miR-381/FYN/MAPK pathway may be applied as a novel target to overcome DOX resistance in breast cancer patients.

A five-gene signature may predict sunitinib sensitivity and serve as prognostic biomarkers for renal cell carcinoma

Sunitinib resistance is, nowadays, the major challenge for advanced renal cell carcinoma patients. Illuminating the potential mechanisms and exploring effective strategies to overcome sunitinib resistance are highly desired. We constructed a reliable gene signature which may function as biomarkers for prediction of sunitinib sensitivity and clinical prognosis. The gene expression profiles were obtained from The Cancer Genome Atlas database. By performing GEO2R analysis, numerous differentially expressed genes (DEGs) were found to be associated with sunitinib resistance. To acquire more precise DEGs, we integrated three different microarray datasets. Functional analysis revealed that these DEGs were mainly involved in Rap1 signaling pathway, p53 signaling pathway and Ras signaling pathway. Then, top five hub genes, BIRC5, CD44, MUC1, TF, CCL5, were identified from protein-protein interaction (PPI) network. Sub-network analysis carried out by MCODE plugin revealed that key DEGs were related with PI3K-Akt signaling pathway, Rap1 signaling pathway and VEGF signaling pathway. Next, we established sunitinib-resistant OS-RC-2 and 786-O cell lines and validated the expression of five hub genes in cell lines. To further evaluate the potentials of five-gene signature for predicting clinical prognosis, we analyzed RCC patients with gene expressions and overall survival information from two independent patient datasets. The Kaplan-Meier estimated the OS of RCC patients in the low- and high-risk groups according to gene expression signature. Multivariate Cox regression analysis indicated that the prognostic power of five-gene signature was independent of clinical features. In conclusion, we developed a five-gene signature which can predict sunitinib sensitivity and OS for advanced RCC patients, providing novel insights into understanding of sunitinib-resistant mechanisms and identification of RCC patients with poor prognosis.

Integrated molecular analysis of Tamoxifen-resistant invasive lobular breast cancer cells identifies MAPK and GRM/mGluR signaling as therapeutic vulnerabilities

Invasive lobular breast cancer (ILC) is an understudied malignancy with distinct clinical, pathological, and molecular features that distinguish it from the more common invasive ductal carcinoma (IDC). Mounting evidence suggests that estrogen receptor-alpha positive (ER+) ILC has a poor response to Tamoxifen (TAM), but the mechanistic drivers of this are undefined. In the current work, we comprehensively characterize the SUM44/LCCTam ILC cell model system through integrated analysis of gene expression, copy number, and mutation, with the goal of identifying actionable alterations relevant to clinical ILC that can be co-targeted along with ER to improve treatment outcomes. We show that TAM has several distinct effects on the transcriptome of LCCTam cells, that this resistant cell model has acquired copy number alterations and mutations that impinge on MAPK and metabotropic glutamate receptor (GRM/mGluR) signaling networks, and that pharmacological inhibition of either improves or restores the growth-inhibitory actions of endocrine therapy.

Structure-Dependent Activity of Polybrominated Diphenyl Ethers and Their Hydroxylated Metabolites on Estrogen Related Receptor γ: in Vitro and in Silico Study

Estrogen-related receptor γ (ERRγ) is an orphan nuclear receptor having functional cross-talk with classical estrogen receptors. Here, we investigated whether ERRγ is a potential target of polybrominated diphenyl ethers (PBDEs) and their hydroxylated metabolites (OH-PBDEs). By using a fluorescence competitive binding method established in our laboratory, the binding potencies of 30 PBDEs/OH-PBDEs with ERRγ were determined for the first time. All of the tested OH-PBDEs and some PBDEs bound to ERRγ with K_d values ranging from 0.13-13.61 μM. The OH-PBDEs showed much higher binding potency than their parent PBDEs. A quantitative structure-activity relationship (QSAR) model was developed to analyze the chemical binding potencies in relation to their structural and chemical characteristics. The QSAR model indicated that the molecular size, relative ratios of aromatic atoms, and hydrogen bond donors and acceptors were crucial factors for PBDEs/OH-PBDEs binding. By using a reporter gene assay, we found that most of the low-brominated PBDEs/OH-PBDEs exerted agonistic activity toward ERRγ, while high-brominated PBDEs/OH-PBDEs had no effect on the basal ERRγ activity. The docking results showed that the low-brominated PBDEs/OH-PBDEs tended to take an agonistic binding mode while the high-brominated ones tended to take an antagonistic binding mode. Overall, our results suggest ERRγ to be a potential novel target for PBDEs/OH-PBDEs.

Application of the CRISPR/Cas9 System to Drug Resistance in Breast Cancer

Clinical evidence indicates that drug resistance is a great obstacle in breast cancer therapy. It renders the disease uncontrollable and causes high mortality. Multiple mechanisms contribute to the development of drug resistance, but the underlying cause is usually a shift in the genetic composition of tumor cells. It is increasingly feasible to engineer the genome with the clustered regularly interspaced short palindromic repeats (CRISPR)/associated (Cas)9 technology recently developed, which might be advantageous in overcoming drug resistance. This article discusses how the CRISPR/Cas9 system might revert resistance gene mutations and identify potential resistance targets in drug-resistant breast cancer. In addition, the challenges that impede the clinical applicability of this technology and highlight the CRISPR/Cas9 systems are presented. The CRISPR/Cas9 system is poised to play an important role in preventing drug resistance in breast cancer therapy and will become an essential tool for personalized medicine.

Antimitotic activity of DY131 and the estrogen-related receptor beta 2 (ERRβ2) splice variant in breast cancer

Breast cancer remains a leading cause of cancer-related death in women, and triple negative breast cancer (TNBC) lacks clinically actionable therapeutic targets. Death in mitosis is a tumor suppressive mechanism that occurs in cancer cells experiencing a defective M phase. The orphan estrogen-related receptor beta (ERRβ) is a key reprogramming factor in murine embryonic and induced pluripotent stem cells. In primates, ERRβ is alternatively spliced to produce several receptor isoforms. In cellular models of glioblastoma, short form (ERRβsf) and beta2 (ERRβ2) splice variants differentially regulate cell cycle progression in response to the synthetic agonist DY131, with ERRβ2 driving arrest in G2/M.The goals of the present study are to determine the cellular function(s) of ligand-activated ERRβ splice variants in breast cancer and evaluate the potential of DY131 to serve as an antimitotic agent, particularly in TNBC. DY131 inhibits growth in a diverse panel of breast cancer cell lines, causing cell death that involves the p38 stress kinase pathway and a bimodal cell cycle arrest. ERRβ2 facilitates the block in G2/M, and DY131 delays progression from prophase to anaphase. Finally, ERRβ2 localizes to centrosomes and DY131 causes mitotic spindle defects. Targeting ERRβ2 may therefore be a promising therapeutic strategy in breast cancer.

Novel multi‑kinase inhibitor, T03 inhibits Taxol‑resistant breast cancer

Activation of kinase-associated signaling pathways is one of the leading causes of various malignant phenotypes in breast tumors. Strategies of drug discovery and development have investigated approaches to target the inhibition of protein kinase signaling. In the current study, the anti‑tumor activities of a novel multi‑kinase inhibitor, T03 were evaluated in breast cancer. T03 inhibited Taxol‑resistant breast cancer cell proliferation and induced cell cycle arrest and apoptosis in vitro and in vivo. The current results demonstrated that T03 downregulated c‑Raf, platelet‑derived growth factor receptor‑β and other kinases, thus inhibited Raf/mitogen‑activated protein kinase kinase/extracellular signal‑regulated kinase and Akt/mechanistic target of rapamycin survival pathways in MCF‑7 and MCF‑7/Taxol xenograft tumors. At a dose of 100 mg/kg, T03 inhibited tumor growth by 62.90 and 59.98% in tumor weight in MX‑1 and MX‑1/T xenograft models, respectively and by 62.60 and 60.22% in MCF‑7 and MCF‑7/T tumors, respectively. These data indicate that the novel multi‑kinase inhibitor, T03, may present as a potential compound to develop novel treatments against breast cancer and Taxol‑resistant breast tumors.

ERRγ: a Junior Orphan with a Senior Role in Metabolism

Estrogen-related receptor (ERR)γ is an orphan nuclear hormone receptor that belongs to the ERR subfamily of transcription factors. No endogenous ligand has been identified to date. ERRγ possesses ligand-independent transcriptional activity that is regulated by co-regulator interactions, and post-translational modifications (PTMs). Recent data from animal models have established ERRγ as a crucial mediator of multiple endocrine and metabolic signals. ERRγ plays important roles in pathological conditions such as insulin resistance, alcoholic liver injury, and cardiac hypertrophy, and controls energy metabolism in the heart, skeletal muscle, and pancreatic β cells. These findings corroborate the importance of ERRγ in metabolic homeostasis, and suggest that ERRγ is a good target for the treatment of metabolic diseases.

The miR-30 family: Versatile players in breast cancer

The microRNA family, miR-30, plays diverse roles in regulating key aspects of neoplastic transformation, metastasis, and clinical outcomes in different types of tumors. Accumulating evidence proves that miR-30 family is pivotal in the breast cancer development by controlling critical signaling pathways and relevant oncogenes. Here, we review the roles of miR-30 family members in the tumorigenesis, metastasis, and drug resistance of breast cancer, and their application to predict the prognosis of breast cancer patients. We think miR-30 family members would be promising biomarkers for breast cancer and may bring a novel insight in molecular targeted therapy of breast cancer.

MCAM/CD146 promotes tamoxifen resistance in breast cancer cells through induction of epithelial-mesenchymal transition, decreased ERα expression and AKT activation

Tamoxifen resistance presents a prominent clinical challenge in endocrine therapy for hormone sensitive breast cancer. However, the underlying mechanisms that contribute to tamoxifen resistance are not fully understood. In this study, we established a tamoxifen resistant MCF-7 cell line (MCF-7-Tam-R) by continuously incubating MCF-7 cells with 4-OH-tamoxifen. We found that melanoma cell adhesion molecule (MCAM/CD146), a unique epithelial-to-mesenchymal transition (EMT) inducer, was significantly up-regulated at both mRNA and protein levels in MCF-7-Tam-R cells compared to parental MCF-7 cells. Mechanistic research demonstrated that MCAM promotes tamoxifen resistance by transcriptionally suppressing ERα expression and activating the AKT pathway, followed by induction of EMT. Elevated MCAM expression was inversely correlated with recurrence-free and distant metastasis-free survival in a cohort of 4142 patients with breast cancer derived from a public database, particularly in the subgroup only treated with tamoxifen. These results demonstrate a novel function of MCAM in conferring tamoxifen resistance in breast cancer. Targeting MCAM might be a promising therapeutic strategy to overcome tamoxifen resistance in breast cancer patients.

Dioscin strengthens the efficiency of adriamycin in MCF-7 and MCF-7/ADR cells through autophagy induction: More than just down-regulation of MDR1

The purpose of present study was to investigate the effect of dioscin on activity of adriamycin (ADR) in ADR-sensitive (MCF-7) and ADR-resistant (MCF-7/ADR) human breast cancer cells and to clarify the molecular mechanisms involved. Antiproliferation effect of ADR was enhanced by dioscin in MCF-7 and MCF-7/ADR cells. Dioscin significantly inhibited MDR1 mRNA and protein expression and MDR1 promoter and nuclear factor κ-B (NF-κB) activity in MCF-7/ADR cells. Additionally, inhibitor κB-α (IκB-α) degradation was inhibited by dioscin. Moreover, dioscin induced the formation of vacuoles in the cytoplasm and protein level of LC3-II in MCF-7 and MCF-7/ADR cells. Autophagy inhibitor 3-MA abolished the effect of dioscin on ADR cytotoxicity. Dioscin inhibited phosphorylation of PI3K and Akt, resulting in upregulation of LC3-II expression. In conclusion, dioscin increased ADR chemosensitivity by down-regulating MDR1 expression through NF-κB signaling inhibition in MCF-7/ADR cells. Autophagy was induced by dioscin to ameliorate the cytotoxicity of ADR via inhibition of the PI3K/AKT pathways in MCF-7 and MCF-7/ADR cells. These findings provide evidence in support of further investigation into the clinical application of dioscin as a chemotherapy adjuvant.

Endocrine therapy resistance in estrogen receptor (ER)-positive breast cancer

Estrogen receptor (ER)-positive breast cancer represents the majority (∼70%) of all breast malignancies. In this subgroup of breast cancers, endocrine therapies are effective both in the adjuvant and recurrent settings, although resistance remains a major issue. Several high-throughput approaches have been used to elucidate mechanisms of resistance and to derive potential predictive markers or alternative therapies. In this review, we cover the state-of-the-art of endocrine-resistance biomarker discovery with regard to the latest technological developments, and discuss current opportunities and restrictions for their implementation into a clinical setting.

Bisphenol A Increases the Migration and Invasion of Triple-Negative Breast Cancer Cells via Oestrogen-related Receptor Gamma

Triple-negative breast cancer (TNBC) is characterized by great metastasis and invasion capability. Our study revealed that nanomolar bisphenol A (BPA), one of the most ubiquitous endocrine disruptors, can increase wound closure and invasion of both MDA-MB-231 and BT-549 cells. BPA treatment can increase protein and mRNA expression of matrix metalloproteinase-2 (MMP-2) and MMP-9, while had no effect on the expression of vimentin (Vim) and fibronectin (FN) in TNBC cells. The expression of G-protein-coupled receptor (GPER), which has been suggested to mediate rapid oestrogenic signals, was not varied in BPA-treated MDA-MB-231 and BT-549 cells. Its inhibitor G15 also had no effect on BPA-induced MMPs expression and cell invasion. Interestingly, BPA treatment can significantly increase the mRNA and protein expressions of oestrogen-related receptor γ (ERRγ), but not ERRα or ERRβ, in both MDA-MB-231 and BT-549 cells. The knock-down of ERRγ can markedly attenuate BPA-induced expression of MMP-2 and MMP-9 in TNBC cells. BPA treatment can activate both ERK1/2 and Akt in TNBC cells. Both inhibitors of ERK1/2 (PD98059) and Akt (LY294002) can attenuate BPA-induced ERRγ expression and cell invasion of MDA-MB-231 cells. Collectively, our data revealed that BPA can increase the expression of MMPs and in vitro motility of TNBC cells via ERRγ. Both activation of ERK1/2 and Akt participated in this process. Our study suggests that more attention should be paid to the roles of xenoestrogens such as BPA in the development and progression of TNBC.

Estrogen-related receptor γ is upregulated in liver cancer and its inhibition suppresses liver cancer cell proliferation via induction of p21 and p27

Orphan nuclear receptor estrogen-related receptor γ (ERRγ) regulates cell growth and tumorigenesis in various cancers. However, the clinical relevance of ERRγ to hepatocellular carcinoma (HCC) remains unclear. Here we examined the clinical significance of ERRγ in HCC and its potential as a therapeutic target. ERRγ levels in tissues from completely resected specimens from 190 HCC patients were examined immunohistochemically and their association with clinical stage and pathological grade was analyzed. Small interfering RNA (siRNA)-mediated knockdown of ERRγ (siRNA-ERRγ) or an ERRγ inverse agonist, GSK5182, were also used to examine the effects of ERRγ inhibition on the proliferation and growth of a human hepatoma cell line, PLC/PRF/5. Immunohistochemical analysis revealed that tumor tissues showed higher levels of ERRγ-positivity than adjacent non-tumor lesions. Tumors showing high levels of ERRγ immunoreactivity also had advanced tumor node metastasis (TNM) and Barcelona Clinic Liver Cancer stages and a higher Edmondson–Steiner grade. In addition, high-level expression of ERRγ in tumors of advanced TNM stage correlated with poorer overall survival. Treatment of PLC/PRF/5 cells with siRNA-ERRγ or GSK5182 inhibited proliferation through G1 arrest, increased expression of p21 and p27 and decreased expression of phosphorylated retinoblastoma protein. GSK5182-induced reactive oxygen species also suppressed the proliferation of PLC/PRF/5 cells. The present study showed that ERRγ expression is clinically significant in HCC; therefore, it can be considered a biomarker for HCC diagnosis. Moreover, the results provide a rationale for the use of ERRγ inhibitors such as GSK5182 as potential therapeutic agents.

Low doses of bisphenol A stimulate the proliferation of breast cancer cells via ERK1/2/ERRγ signals

The effects and mechanisms of bisphenol A (BPA) on the development of breast cancer are still not well illustrated. The present study revealed that nanomolar BPA significantly promoted the proliferation of both estrogen receptor (ER) positive (MCF-7) and negative (SkBr3) breast cancer cells, which was confirmed by up regulation of proliferating cell nuclear antigen (PCNA) and Bcl-2. Neither ERα nor G-protein-coupled estrogen receptor (GPER) mediated this effect of BPA because their inhibitors had no effect on the BPA induced cell proliferation. However, silencing of estrogen related receptor gamma (ERRγ) by its specific siRNA significantly abolished BPA induced proliferation of breast cancer cells, while si-ERRα had no similar effect. Moreover, nanomolar BPA up regulated the mRNA and protein levels of ERRγ and triggered its nuclear translocation via a time dependent manner. Further studies revealed that 10(-8)M BPA obviously increased the phosphorylation of ERK1/2, while had no similar effect on the phosphorylation of JNK and p38 MAPK. Further, PD 98059, the inhibitor of ERK1/2, significantly abolished the BPA induced up regulation of ERRγ and proliferation of breast cancer cells. Collectively, our results revealed that nanomolar BPA can trigger the proliferation of breast cancer cells via ERK1/2/ERRγ signals. Given that nanomolar BPA has been widely detected in human tissues, the clinical relevance of BPA and breast cancer progression should be further investigated.

ERRγ target genes are poor prognostic factors in Tamoxifen-treated breast cancer

BACKGROUND

One-third of estrogen (ER+) and/or progesterone receptor-positive (PGR+) breast tumors treated with Tamoxifen (TAM) do not respond to initial treatment, and the remaining 70% are at risk to relapse in the future. Estrogen-related receptor gamma (ESRRG, ERRγ) is an orphan nuclear receptor with broad, structural similarities to classical ER that is widely implicated in the transcriptional regulation of energy homeostasis. We have previously demonstrated that ERRγ induces resistance to TAM in ER+ breast cancer models, and that the receptor's transcriptional activity is modified by activation of the ERK/MAPK pathway. We hypothesize that hyper-activation or over-expression of ERRγ induces a pro-survival transcriptional program that impairs the ability of TAM to inhibit the growth of ER+ breast cancer. The goal of the present study is to determine whether ERRγ target genes are associated with reduced distant metastasis-free survival (DMFS) in ER+ breast cancer treated with TAM.

METHODS

Raw gene expression data was obtained from 3 publicly available breast cancer clinical studies of women with ER+ breast cancer who received TAM as their sole endocrine therapy. ERRγ target genes were selected from 2 studies that published validated chromatin immunoprecipitation (ChIP) analyses of ERRγ promoter occupancy. Kaplan-Meier estimation was used to determine the association of ERRγ target genes with DMFS, and selected genes were validated in ER+, MCF7 breast cancer cells that express exogenous ERRγ.

RESULTS

Thirty-seven validated receptor target genes were statistically significantly altered in women who experienced a DM within 5 years, and could classify several independent studies into poor vs. good DMFS. Two genes (EEF1A2 and PPIF) could similarly separate ER+, TAM-treated breast tumors by DMFS, and their protein levels were measured in an ER+ breast cancer cell line model with exogenous ERRγ. Finally, expression of ERRγ and these two target genes are elevated in models of ER+ breast cancer with hyperactivation of ERK/MAPK.

CONCLUSIONS

ERRγ signaling is associated with poor DMFS in ER+, TAM-treated breast cancer, and ESRRG, EEF1A2, and PPIF comprise a 3-gene signaling node that may contribute to TAM resistance in the context of an active ERK/MAPK pathway.

Cytoplasmic PELP1 and ERRgamma protect human mammary epithelial cells from Tam-induced cell death

Tamoxifen (Tam) is the only FDA-approved chemoprevention agent for pre-menopausal women at high risk for developing breast cancer. While Tam reduces a woman's risk of developing estrogen receptor positive (ER+) breast cancer, the molecular mechanisms associated with risk reduction are poorly understood. Prior studies have shown that cytoplasmic proline, glutamic acid and leucine rich protein 1 (PELP1) promotes Tam resistance in breast cancer cell lines. Herein, we tested for PELP1 localization in breast epithelial cells from women at high risk for developing breast cancer and found that PELP1 was localized to the cytoplasm in 36% of samples. In vitro, immortalized HMECs expressing a nuclear localization signal (NLS) mutant of PELP1 (PELP1-cyto) were resistant to Tam-induced death. Furthermore, PELP1-cyto signaling through estrogen-related receptor gamma (ERRγ) promoted cell survival in the presence of Tam. Overexpression of ERRγ in immortalized HMECs protected cells from Tam-induced death, while knockdown of ERRγ sensitized PELP1-cyto expressing HMECs to Tam. Moreover, Tam-induced HMEC cell death was independent of apoptosis and involved accumulation of the autophagy marker LC3-II. Expression of PELP1-cyto and ERRγ reduced Tam-induced LC3-II accumulation, and knockdown of ERRγ increased LC3-II levels in response to Tam. Additionally, PELP1-cyto expression led to the upregulation of MMP-3 and MAOB, known PELP1 and ERRγ target genes, respectively. Our data indicate that cytoplasmic PELP1 induces signaling pathways that converge on ERRγ to promote cell survival in the presence of Tam. These data suggest that PELP1 localization and/or ERRγ activation could be developed as tissue biomarkers for Tam responsiveness.

Role of miR-155 in drug resistance of breast cancer

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expressions at posttranscriptional level. Growing evidence points to their significant role in the acquisition of drug resistance in cancers. Studies show that miRNAs are often aberrantly expressed in human cancer cells which are associated with tumorigenesis, metastasis, invasiveness, and drug resistance. Breast cancer is the leading cause of cancer-induced death in women. Over the last decades, increasing attention has been paid to the effects of miRNAs on the development of breast cancer drug resistance. Among them, miR-155 takes part in a sequence of bioprocesses that contribute to the development of such drug resistance, including repression of FOXO3a, enhancement of epithelial-to-mesenchymal transition (EMT) and mitogen-activated protein kinase (MAPK) signaling, reduction of RhoA, and affecting the length of telomeres. In this review, we discuss the role of miR-155 in the acquisition of breast cancer drug resistance. This will provide a new way in antiresistance treatment of drug-resistant breast cancer.

Sequential release of drugs from hollow manganese ferrite nanocarriers for breast cancer therapy

Single drug therapies for cancer are often ineffective and may not provide long term clinical benefits.

Endocrine Resistance in Breast Cancer

Around 70% of all breast cancers are estrogen receptor alpha positive and hence their development is highly dependent on estradiol. While the invention of endocrine therapies has revolusioned the treatment of the disease, resistance to therapy eventually occurs in a large number of patients. This paper seeks to illustrate and discuss the complexity and heterogeneity of the mechanisms which underlie resistance and the approaches proposed to combat them. It will also focus on the use and development of methods for predicting which patients are likely to develop resistance.

The pERK of being a target: Kinase regulation of the orphan nuclear receptor ERRγ

Estrogen-related receptors (ERRs) are orphan members of the nuclear receptor superfamily that are important regulators of mitochondrial metabolism with emerging roles in cancer. In the absence of an endogenous ligand, ERRs are reliant upon other regulatory mechanisms that include protein/protein interactions and post-translational modification, though the cellular and clinical significance of this latter mechanism is unclear. We recently published a study in which we establish estrogen-related receptor gamma (ERRγ) as a target for extracellular signal-regulated kinase (ERK), and show that regulation of ERRγ by ERK has important consequences for the function of this receptor in cellular models of estrogen receptor-positive (ER+) breast cancer. In this Research Highlight, we discuss the implications of these findings from a molecular and clinical perspective.