Steviol glycosides affect functional properties and macromolecular expression of breast cancer cells.

Steviol glycosides, the active sweet components of stevia plant, have been recently found to possess a number of therapeutic properties, including some recorded anticancer ones against various cancer cell types (breast, ovarian, cervical, pancreatic, and colon cancer). Our aim was to investigate this anticancer potential on the two most commonly used breast cancer cell lines which differ in the phenotype and estrogen receptor (ER) status: the low metastatic, ERα+ MCF-7 and the highly metastatic, ERα-/ERß+ MDA-MB-231. Specifically, glycosides' effect was studied on cancer cells': (a) viability, (b) functionality (proliferation, migration, and adhesion), and (c) gene expression (mRNA level) of crucial molecules implicated in cancer's pathophysiology. Results showed that steviol glycosides induced cell death in both cell lines, in the first 24 hr, which was in line with the antiapoptotic BCL2 decrease. However, cells that managed to survive showcased diametrically opposite behavior. The low metastatic ERα+ MCF-7 cells acquired an aggressive phenotype, depicted by the upregulation of all receptors and co-receptors (ESR, PGR, AR, GPER1, EGFR, IGF1R, CD44, SDC2, and SDC4), as well as VIM and MMP14. On the contrary, the highly metastatic ERα-/ERß+ MDA-MB-231 cells became less aggressive as pointed out by the respective downregulation of EGFR, IGF1R, CD44, and SDC2. Changes observed in gene expression were compatible with altered cell functions. Glycosides increased MCF-7 cells migration and adhesion, but reduced MDA-MB-231 cells migratory and metastatic potential. In conclusion, the above data clearly demonstrate that steviol glycosides have different effects on breast cancer cells according to their ER status, suggesting that steviol glycosides might be examined for their potential anticancer activity against breast cancer, especially triple negative breast cancer (TNBC).

Estrogen receptor ß2 (ERß2)-mediated upregulation of hsa_circ_0000732 promotes tumor progression via sponging microRNA-1184 in triple-negative breast cancer (TNBC).

BACKGROUND: The role of estrogen receptor ß (ERß) in the pathogenesis and development of breast cancer (BC) is controversial, and it is currently considered to play contradictory roles in different phenotypes. ERß2 is thought to promote the BC process, but its role in triple-negative breast cancer (TNBC) has not been reported. METHODS: In this study, we collected tumor tissues from 15 patients with TNBC and obtained a variety of TNBC cell lines as research objects. The plasmid vectors and RNA interference techniques were used to change the level of target genes in cells, quantitative PCR and Western Blots were used to detect gene expression levels, CCK-8 and EdU assay were used to detect cell growth, and Transwell was used to detect cell migration and invasion. Dual-luciferase gene reports and RNA immunoprecipitation (RIP) were used to verify gene targeting relationships. RESULTS: ERß2 was up-regulated in TNBC tissues and promoted the growth, migration, and invasion of TNBC cells. ERß2 regulated hsa_circ_0000732 expression by binding to SCARF1 promoter. Knockdown of hsa_circ_0000732 inhibited TNBC cell proliferation, migration, and invasion by upregulating miR-1184. CONCLUSION: Our present study found that ERß2 is upregulated in some TNBC cells and promotes TNBC cell growth, migration and invasion by regulating hsa_circ_0000732 targeting miR-1184. The special role of ERß2 in TNBC may be the breakthrough of a targeted treatment strategy for TNBC.

Induction of estrogen receptor ß-mediated autophagy sensitizes breast cancer cells to TAD1822-7, a novel biphenyl urea taspine derivative.

BACKGROUND: Female breast cancer has become the most commonly diagnosed cancer worldwide. As a tumor suppressor, estrogen receptor ß (ERß) can be potentially targeted for breast cancer therapy. METHODS AND RESULTS: TAD1822-7 was evaluated for ERß-mediated autophagy and cell death using cell proliferation assay, Annexin V/PI staining, immunofluorescence, western blotting, ERß siRNA, ERß plasmid transfection and hypoxia cell models. TAD1822-7 upregulated ERß causing cell death and induced mitochondrial dysfunction and autophagy companied with mitochondrial located ERß. Enhanced levels of microtubule associated protein1 light chain 3 (LC3)-II and p62/SQSTM1 (p62) indicated that TAD1822-7 blocked the late-stage autolysosome formation, leading to cell death. Mechanistically, TAD1822-7-induced cell death was mediated by phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathways. Moreover, TAD1822-7 modulated hypoxia inducible factor (HIF) functions and autophagy via the inhibition of HIF-1ß in the context of hypoxia-induced autophagy. ERß overexpression and ERß agonist showed similar effects, whereas ERß siRNA abrogated TAD1822-7-induced cell death, the inhibition of PI3K/AKT pathway and autophagy. The involvement of PI3K/AKT pathway and autophagy was also demonstrated in TAD1822-7-treated hypoxic breast cancer cells. CONCLUSIONS: These findings provide new insight into the mechanism underlying the inhibitory effects of TAD1822-7 via ERß-mediated pathways in breast cancer cells.

Estrogen Receptor ß as a Possible Double-Edged Sword Molecule in Breast Cancer: A Mechanism of Alteration of Its Role by Exposure to Endocrine-Disrupting Chemicals.

Estrogen is essential for the growth and development of mammary glands and its signaling is associated with breast cancer growth. Estrogen can exert physiological actions via estrogen receptors α/ß (ERα/ß). There is experimental evidence suggesting that in ERα/ß-positive breast cancer, ERα promotes tumor cell proliferation and ERß inhibits ERα-mediated transcriptional activity, resulting in abrogation of cell growth. Therefore, ERß is attracting attention as a potential tumor suppressor, and as a biomarker and therapeutic target in the ERα/ß-positive breast cancer. Based on this information, we have hypothesized that some endocrine-disrupting chemicals (EDCs) that can perturb the balance between ERα and ERß expression levels in breast cancer cells might have effects on the breast cancer proliferation (i.e., down-regulation of the α-type of ER). We have recently reported that 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP), an active metabolite of bisphenol A, in ERα/ß-positive human breast cancer significantly down-regulates ERα expression, yet stimulates cell proliferation through the activation of ERß-mediated transcription. These results support our hypothesis by demonstrating that exposure to MBP altered the functional role of ERß in breast cancer cells from suppressor to promoter. In contrast, some EDCs, such as Δ9-tetrahydrocannabinol and bisphenol AF, can exhibit anti-estrogenic effects through up-regulation of ERß expression without affecting the ERα expression levels. However, there is no consensus on the correlation between ERß expression levels and clinical prognosis, which might be due to differences in exposed chemicals. Therefore, elucidating the exposure effects of EDCs can reveal the reason for inconsistent functional role of ERß in ERα/ß-positive breast cancer.

Key role of estrogen receptor ß in the organization of brain and behavior of the Japanese quail.

Estrogens play a key role in the sexual differentiation of the brain and behavior. While early estrogen actions exert masculinizing effects on the brain of male rodents, a diametrically opposite effect is observed in birds where estrogens demasculinize the brain of females. Yet, the two vertebrate classes express similar sex differences in the brain and behavior. Although ERα is thought to play a major role in these processes in rodents, the role of ERß is still controversial. In birds, the identity of the estrogen receptor(s) underlying the demasculinization of the female brain remains unclear. The aim of the present study was thus to determine in Japanese quail the effects of specific agonists of ERα (propylpyrazole triol, PPT) and ERß (diarylpropionitrile, DPN) administered at the beginning of the sensitive period (embryonic day 7, E7) on the sexual differentiation of male sexual behavior and on the density of vasotocin-immunoreactive (VT-ir) fibers, a known marker of the organizational action of estrogens on the quail brain. We demonstrate that estradiol benzoate and the ERß agonist (DPN) demasculinize male sexual behavior and decrease the density of VT-ir fibers in the medial preoptic nucleus and the bed nucleus of the stria terminalis, while PPT has no effect on these measures. These results clearly indicate that ERß, but not ERα, is involved in the estrogen-induced sexual differentiation of brain and sexual behavior in quail.

Role of estrogen receptor beta in neural differentiation of mouse embryonic stem cells.

The ability to propagate mature cells and tissue from pluripotent stem cells offers enormous promise for treating many diseases, including neurodegenerative diseases. Before such cells can be used successfully in neurodegenerative diseases without causing unwanted cell growth and migration, genes regulating growth and migration of neural stem cells need to be well characterized. Estrogen receptor beta (ERß) is essential for migration of neurons and glial cells in the developing mouse brain. To examine whether ERß influences differentiation of mouse embryonic stem cells (mESC) into neural lineages, we compared control and ERß knockout (BERKO) mESCs at defined stages of neural development and examined the effects of an ERß-selective ligand (LY3201) with a combination of global and targeted gene-expression profiling and the expression of key pluripotency markers. We found that ERß was induced in embryoid bodies (EBs) and neural precursor cells (NPCs) during development. Proliferation was higher in BERKO NPCs and was inhibited by LY3201. Neurogenesis was reduced in BERKO ES cells, and oligodendrogliogenesis was enhanced. BERKO EBs expressed higher levels of key ectodermal and neural progenitor markers and lower levels of markers for mesoderm and endoderm lineages. ERß-regulated factors are involved in cell adhesion, axon guidance, and signaling of Notch and GABA receptor pathways, as well as factors important for the differentiation of neuronal precursors into dopaminergic neurons (Engrailed 1) and for the oligodendrocyte fate acquisition (Olig2). Our data suggest that ERß is an important component for differentiation into midbrain neurons as well as for preventing precocious oligodendrogliogenesis.

The Genetic Background of Endometriosis: Can ESR2 and CYP19A1 Genes Be a Potential Risk Factor for Its Development?

Endometriosis is defined as the presence of endometrial foci, localized beyond their primary site, i.e., the uterine cavity. The etiology of this disease is rather complex. Its development is supported by hormonal, immunological, and environmental factors. During recent years, particular attention has been focused on the genetic mechanisms that may be of particular significance for the increased incidence rates of endometriosis. According to most recent studies, ESR2 and CYP19A1 genes may account for the potential risk factors of infertility associated with endometriosis. The paper presents a thorough review of the latest reports and data concerning the genetic background of the risk for endometriosis development.

Role of Differential Estrogen Receptor Activation in Airway Hyperreactivity and Remodeling in a Murine Model of Asthma.

Evidence suggests that airway hyperresponsiveness (AHR) is a characteristic feature of asthma. Epidemiological studies have confirmed that the severity of asthma is greater in women, suggesting a critical role of female sex steroid hormones (especially estrogen). Very few in vivo studies have examined the role of sex steroid hormones in asthma, and the sequence of events that occur through differential activation of estrogen receptors (ERs) remains to be determined in asthmatic airways. Our recent in vitro findings indicated that ERß had increased expression in asthmatic airway smooth muscle (ASM), and that its activation by an ERß-specific agonist downregulated airway remodeling. In this study, we translated the in vitro findings to a murine asthma model and examined the differential role of ER activation in modulating lung mechanics. C57BL/6J male, female, and ovariectomized mice were exposed to mixed allergen (MA) and subcutaneously implanted with sustained-release pellets of placebo, an ERα agonist (4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol [PPT]), and/or an ERß agonist (WAY-200070). We then evaluated the effects of these treatments on airway mechanics, biochemical, molecular, and histological parameters. Mice exposed to MA showed a significant increase in airway resistance, elastance, and tissue damping, and a decrease in compliance; pronounced effects were observed in females. Compared with PPT, WAY treatment significantly reversed the MA-induced changes. The increased mRNA/protein expression of ERα, ERß, and remodeling genes observed in MA-treated mice was significantly reversed in WAY-treated mice. This novel study indicates that activation of ERß signaling downregulates AHR and airway remodeling, and is a promising target in the development of treatments for asthma.

Bakuchiol exhibits anti-metastasis activity through NF-κB cross-talk signaling with AR and ERß in androgen-independent prostate cancer cells PC-3.

Androgen-independent prostate cancer (PCa) is a developed tumor derived from the local androgen dependent PCa, which often affects elderly men. Psoralea corylifolia L, a traditional Chinese medicine, has been widely used for PCa treatment as an important part of a common prescription, while the mechanism remains unclear. Our study was aimed to investigate the tumor-inhibitory effect of its main component bakuchiol in androgen-independent PCa cell line PC-3 cells. Bakuchiol significantly suppressed PC-3 cell proliferation and migration; the expressions of PCNA and MMP-9 were consistently down regulated as well. Meanwhile, both the constitutive and LPS-induced NF-κB activation were significantly inhibited by bakuchiol. The inhibitory effects of bakuchiol on cell proliferation, migration and invasion were recovered when LPS were added together with bakuchiol. SiRNA against androgen receptor (AR) or estrogen receptor ß (ERß) were transfected and the regulation of bakuchiol-suppressed proliferation, invasion, NF-κB signaling and MMP-9 secretion in response to LPS were blocked. Taken together, our data demonstrated that bakuchiol inactivated NF-κB signaling via AR and ERß, which contributes to inhibition of PC-3 cell proliferation and migration, indicating that bakuchiol is one of the key component from P. corylifolia L for PCa treatment and has a potential as anti-prostate cancer drug candidates.

Role of Estradiol Receptor Beta (ERß) on Arterial Pressure, Respiratory Chemoreflex and Mitochondrial Function in Young and Aged Female Mice.

We tested the hypothesis that ERß is involved in respiratory control in female mice. We used young adult (5-6 months-old) and aged (17-18 months-old) ERßKO or wild-type controls (WT) female mice to assess arterial blood pressure (via a tail-cuff sensor) and indices of respiratory pattern (sighs and apneas - recorded by whole body plethysmography at rest). We also measured respiratory parameters at rest and in response to brief (<10 min) exposure to hypoxia (12% O2) or hypercapnia (5% CO2). Because ERß is localized in mitochondria, and because estradiol and ERß agonist increase mitochondrial O2 consumption, we assessed the mitochondrial respiration (with a high-resolution oxygraph system) and the in vitro activity of the complex I of the electron transfer chain in samples of brain cortex in aged wild-type and ERßKO female mice. Compared to young WT mice, young ERßKO mice had elevated arterial blood pressure, but similar ventilatory responses to hypoxia and hypercapnia. In old ERßKO female mice compared to old WT mice, the arterial blood pressure was lower, the frequency of sighs was higher and the frequency of apneas was lower, and the hypoxic and hypercapnic ventilatory responses were reduced. In old ERßKO mice mitochondrial respiration and complex I activities in the brain cortex were lower than in WT mice. We conclude that ERß has age-specific effects on vascular and respiratory functions in female mice.

Opposing Effects of Cyclooxygenase-2 (COX-2) on Estrogen Receptor ß (ERß) Response to 5α-Reductase Inhibition in Prostate Epithelial Cells.

Current pharmacotherapies for symptomatic benign prostatic hyperplasia (BPH), an androgen receptor-driven, inflammatory disorder affecting elderly men, include 5α-reductase (5AR) inhibitors (i.e. dutasteride and finasteride) to block the conversion of testosterone to the more potent androgen receptor ligand dihydrotestosterone. Because dihydrotestosterone is the precursor for estrogen receptor ß (ERß) ligands, 5AR inhibitors could potentially limit ERß activation, which maintains prostate tissue homeostasis. We have uncovered signaling pathways in BPH-derived prostate epithelial cells (BPH-1) that are impacted by 5AR inhibition. The induction of apoptosis and repression of the cell adhesion protein E-cadherin by the 5AR inhibitor dutasteride requires both ERß and TGFß. Dutasteride also induces cyclooxygenase type 2 (COX-2), which functions in a negative feedback loop in TGFß and ERß signaling pathways as evidenced by the potentiation of apoptosis induced by dutasteride or finasteride upon pharmacological inhibition or shRNA-mediated ablation of COX-2. Concurrently, COX-2 positively impacts ERß action through its effect on the expression of a number of steroidogenic enzymes in the ERß ligand metabolic pathway. Therefore, effective combination pharmacotherapies, which have included non-steroidal anti-inflammatory drugs, must take into account biochemical pathways affected by 5AR inhibition and opposing effects of COX-2 on the tissue-protective action of ERß.

Changes in related circular RNAs following ERß knockdown and the relationship to rBMSC osteogenesis.

Recently, several studies have indicated that circular RNAs (circRNAs) play significant roles in various disease; however, little is known about the chronology of estrogen receptor beta (ERß) deficiency and altered circRNA expression, or their relationship with osteogenesis. Herein, we show through western-blot and quantitative real-time PCR assays, that when ERß is silenced, the expression of osteogenesis-related proteins and mRNAs were down-regulated. We then performed RNA-Seq to analyze differential circRNA expression between the control and ERß knockdown group. This analysis revealed that, 146 circRNAs were differentially expressed by fold-change≥2.0, p ≤ 0.05, and, among this group, 68 circRNAs were down-regulated, while 78 were up-regulated. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and PANTHER pathway analyses were performed to predict the function of these differentially expressed circRNAs. Finally, co-expressed targets gene, and circRNA-microRNA network were constructed for predicted miRNA sponges. This research suggested that ERß may through 2:27713879|27755789/2:240822115|240867796-miR-328-5p-mRNA axis to regulate osteogenic differentiation.

Divergent effects of ERα and ERß on fluid intake by female rats are not dependent on concomitant changes in AT1R expression or body weight.

Estradiol (E2) decreases both water and saline intakes by female rats. The ERα and ERß subtypes are expressed in areas of the brain that control fluid intake; however, the role that these receptors play in E2's antidipsogenic and antinatriorexigenic effects have not been examined. Accordingly, we tested the hypothesis that activation of ERα and ERß decreases water and saline intakes by female rats. We found a divergence in E2's inhibitory effect on intake: activation of ERα decreased water intake, whereas activation of ERß decreased saline intake. E2 decreases expression of the angiotensin II type 1 receptor (AT1R), a receptor with known relevance to water and salt intakes, in multiple areas of the brain where ERα and ERß are differentially expressed. Therefore, we tested for agonist-induced changes in AT1R mRNA expression by RT-PCR and protein expression by analyzing receptor binding to test the hypothesis that the divergent effects of these ER subtypes are mediated by region-specific changes in AT1R expression. Although we found no changes in AT1R mRNA or binding in areas of the brain known to control fluid intake associated with agonist treatment, the experimental results replicate and extend previous findings that body weight changes mediate alterations in AT1R expression in distinct brain regions. Together, the results reveal selective effects of ER subtypes on ingestive behaviors, advancing our understanding of E2's inhibitory role in the controls of fluid intake by female rats.

Cardiomyocyte-specific overexpression of oestrogen receptor ß improves survival and cardiac function after myocardial infarction in female and male mice.

ERß (oestrogen receptor ß) activation has been shown to be cardioprotective, but the cell types and mechanisms involved are not understood. To investigate whether ERß restricted to cardiomyocytes contributes to the observed cardioprotection, we tested the effects of cardiomyocyte-specific ERß-OE (ERß overexpression) on survival, cardiac remodelling and function after MI (myocardial infarction) and studied the molecular pathways potentially involved. Female and male mice with cardiomyocyte-specific ERß-OE and WT (wild-type) littermates were subjected to chronic anterior coronary artery ligation or sham surgery. Two weeks after MI, ERß-OE mice showed improved survival (100% and 83% compared with 76% and 58% in WT females and males respectively). ERß-OE was associated with attenuated LV (left ventricular) dilatation, smaller increase in heart weight, less lung congestion at similar MI size, and improved systolic and diastolic function in both sexes. We identified two potential pathways for ERß-mediated myocardial protection. First, male and female ERß-OE mice had a lower reduction of SERCA2a (sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase 2a) expression after MI, suggesting less reduction in diastolic Ca(2+)-reuptake into the sarcoplasmic reticulum post-MI. Secondly, male ERß-OE revealed attenuated cardiac fibrosis in the remote LV tissue and expression of fibrosis markers collagen I and III, periostin and miR-21. Cardiomyocyte-specific ERß-OE improved survival associated with reduced maladaptive remodelling, improved cardiac function and less heart failure development after MI in both sexes. These effects seem to be related, at least in part, to a better maintenance of Ca(2+) cycling in both sexes and a lower induction of cardiac fibrosis in males after MI.

Estrogen receptor α and ß are involved in the activation of lordosis behavior in estradiol-primed rats.

The present study was designed to assess the participation of estrogen receptors alpha (ERα) and beta (ERß) in the short-term facilitation of lordosis behavior in ovariectomized (ovx), estradiol (E2) primed rats. In experiment 1, dose response curves for PPT and DPN (ERα and ERß agonists, respectively) facilitation of lordosis behavior (lordosis quotient and lordosis score) were established by infusing these agonists into the right lateral ventricle (icv) in female rats injected 40h previously with 5µg of E2 benzoate. PPT doses of 0.08 and 0.4ng produced high lordosis quotients starting at 30min and continuing at 120 and 240min post-injection. DPN induced high levels of lordosis behavior at all times tested. However, the intensity of lordosis induced by both agonists was weak. In experiment 2, we tested the involvement of each ER in facilitation of lordosis by icv infusion of MPP (ERα-selective antagonist) or PHTPP (ERß-selective antagonist) prior to infusion of 2ng of free E2. Icv infusion of either MPP or PHTPP 30min before free E2 significantly depressed E2 facilitation of lordosis. The results suggest that both forms of ER are involved in the short-latency facilitation of lordosis behavior in E2-primed rats.

Hormone therapy and large bowel cancer revisited.

Many studies have investigated potential links between postmenopausal hormone therapy (HT) and the risk for colorectal cancer. Most of these studies showed some reduction in risk, but association with the exact grade of the tumor or with cancer mortality is less consistent. Activation of estrogen receptor beta (ERß) related cellular pathways is probably the pathophysiological basis for this HT effect, since ERßs exert antiproliferative and pro-apoptotic signaling, inhibit inflammatory signaling and modulate the tumor microenvironment. To note, the impact on health may not be substantial as the absolute numbers point at the order of only a few saved cases per 10 000 women per year of hormone use.

Implication of the estrogen receptors GPER, ESR1, ESR2 in post-testicular maturations of equine spermatozoa.

Estrogen receptors ESR1, ESR2 and GPER are present on mature ejaculated horse spermatozoa, suggesting these cells as putative targets for estrogens. Indeed, spermatozoa are exposed to high level of estrogens during the transit in the male and female genital tracts but their roles are not investigated. So, we evaluated in vitro the role of 17ß-estradiol during post-testicular maturations: regulation of motility, capacitation and acrosome reaction. Moreover according to the pseudo-seasonal breeder status of the stallion, we analyzed the putative seasonal variations in the presence of ESRs in spermatozoa. We showed that ESRs are more present on stallion sperm during the breeding season. We showed that capacitation and acrosome reaction are independent of estradiol action in horse. Estradiol can weakly modulate the motility and this effect is strictly associated with GPER and not with ESR1 and ESR2. The subcellular localization of GPER in the neck on stallion sperm is coherent with this effect. It seems that estrogens are not major regulators of sperm maturations associated to mare genital tract, so they could act during the epididymal maturations.

Estrogen receptor beta and ovarian cancer: a key to pathogenesis and response to therapy.

INTRODUCTION: Ovarian cancer remains the leading cause of mortality due to gynecological tumors. Estrogen receptors (ERs) seem to participate in tumor progression even in the absence of estrogens. Twenty years after the cloning of the second estrogen receptor, a wide spectrum of studies have shown its implication in both physiologic and pathologic pathways. ERß, being the predominant type of ER in normal ovary tissue, has not only been linked with pathogenesis of ovarian cancer, but also with response to treatment. Unlike ERα, which is primarily linked with cell growth, ERß presence is prominent in signaling pathways, cell cycle regulation and apoptosis. METHODS: Literature review of relevant published material (from PubMed, Scopus, and Cochrane databases) was conducted. RESULTS: Polymorphisms in the respective ESR2 gene, epigenetic modifications and isoforms of the receptor have been extensively studied to assess potential correlations with responsiveness to treatment and tumor behavior. Studies on the exact roles of ERß and its genetic variations in altering effectiveness and toxicity of ovarian cancer treatment regimens are lacking. CONCLUSION: Clinical utilization of ERß actions in the management of ovarian cancer is discussed in an up-to-date review.

Roles of ERα and ERß in estrogen-induced DDP chemoresistance in non-small cell lung cancer.

The role of estrogen in inducing chemoresistance is not yet fully understood. The objective of this study was to observe the relationship between estrogen levels and cellular response to chemotherapeutic drugs in non-small cell lung cancer (NSCLC) and to reveal the potential mechanisms involved. Cell viability was analyzed after pre-treating NSCLC cells with different levels of estrogen (E2), followed by treatment with an anti-tumor drug for 48 h. The roles of various estrogen receptors (ERs) were examined in vitro by blocking the activity of each ER individually. The ER pathway was further confirmed in NSCLC tissues. It was found that 10-1000 nM E2 resulted in a decreased cellular response to DDP in H1650 cells compared to the use of cisplatin alone (P < 0.05). However, this result was not demonstrated in H1299 cells, which lack p53. Both ERa and ERb were associated with E2-induced cisplatin chemoresistance, though they had opposite functions. p53 expression did not correlate with the expression of ERa or ERb individually. However, a statistically significant correlation between p53 expression and ERa to ERb mRNA ratio was observed (P < 0.001, R = -0.676). These findings suggest that E2-induced DDP chemoresistance depends on the balance between ERa and ERb expression and the p53 pathway.

Methyltransferase-like 17 physically and functionally interacts with estrogen receptors.

Estrogen exerts its physiological and pathological functions through two estrogen receptors (ERs), ERα and ERß, which act as transcription factors. Coregulators, including coactivators and corepressors, have been shown to be crucial for regulation of ER transcriptional activity. Although many coregulators have been identified to regulate activities of ERs, novel coregulators are still needed to be investigated. Here, we show that human methyltransferase-like 17 (METTL17), whose function is unknown, physically interacts with ERα and ERß, and functionally acts as a coactivator for ERs. METTL17 interacts with ER in vitro and in yeast and mammalian cells. Activation function-1 (AF1) and AF2 domains of ERs are responsible for the interaction between METTL17 and ERs. Knockdown of METTL17 reduces transcriptional activities of ERα and ERß in breast cancer cells, whereas METTL17 overexpression increases ERα and ERß transcriptional activities. Inhibition of METTL17 expression decreases mRNA and protein levels of ER target genes, including PR, cathepsin D, and pS2. Moreover, METTL17 knockdown reduces breast cancer cell growth. These results indicate that METTL17 is a novel coactivator of ERs and may play a role in breast tumorigenesis.