A New Role for Estrogen Receptor α in Cell Proliferation and Cancer: Activating the Anticipatory Unfolded Protein Response

Combined treatment of All-trans retinoic acid with Tamoxifen suppresses ovarian cancer

BACKGROUND

Ovarian cancer is a malignant tumor of the female reproductive system, and its mortality rate is as high as 70%. Estrogen receptor α (ERα)-positive ovarian cancer accounted for most of all ovarian cancer patients. ERα can promote the growth and proliferation of tumors.

METHODS

The combined effect of All-trans retinoic acid (ATRA) and tamoxifen was obtained by the combination screening of tamoxifen and compound library by MTS. In addition, colony formation assay, flow cytometry analysis, immunofluorescence staining, quantitative real-time polymerase chain reaction (PCR), western blot, and tumor xenotransplantation models were used to further evaluate the efficacy of tamoxifen and ATRA in vitro and in vivo for ER-α-positive ovarian cancer.

RESULTS

In our study, we found that All-trans retinoic acid (ATRA) can cooperate with tamoxifen to cause cell cycle arrest and apoptosis and inhibit ERα-positive ovarian cancer in vivo and in vitro. Further exploration of the mechanism found that ATRA can Inhibit genes related to the ERα signaling pathway, enhance the sensitivity of ERα-positive ovarian cancer cells to tamoxifen, and ascertain the effectiveness of tamoxifen and ATRA as treatments for ovarian cancer with an ERα-positive status.

CONCLUSION

Combination of ATRA and tamoxifen is a new way for the treatment of ERα-positive ovarian cancer.

ERα promotes SUMO1 transcription by binding with the ERE and enhances SUMO1-mediated protein SUMOylation in breast cancer

Background

Estrogen plays a crucial role in the tumorigenesis of breast cancer (BC), and epigenetic modification by SUMOylation is essential for cancer development. However, the mechanism underlying estrogen's actions on protein SUMOylation and its effect on BC development are still incompletely understood.

Methods

SUMO1 in BC cell lines was verified via real-time quantitative PCR (RT-qPCR) and western blot. Cell proliferation and colony formation assays was also performed to evaluate SUMOylation as mediated by SUMO1. Luciferase activity to examine whether E2 promoted the transcription of SUMO1, and chromatin immunoprecipitation (ChIP) assay to determine the binding of estrogen receptor alpha (ERα) to SUMO1 were conduction, and an animal model was used to evaluate the effects of E2-ERα-enhanced SUMO1 transcription.

Results

E2 promoted SUMO1 mRNA and protein expression levels in a dose- and time-dependent manner in ER-positive BC cells; it exerted no influence on SUMO2/3 expression; in E2-induced SUMO1 transcription, ERα, but not ERβ, was essential to the process. In addition, E2-ERα upregulated the transcription of SUMO1 by binding with an estrogen-response element half-site (1/2ERE, in the -134 to -123 bp region) of the SUMO1 promoter, and E2-ERα induced SUMO1 transcription-enhanced cellular viability in ER-positive BC cells. To further determine SUMOylation as mediated by SUMO1 in ER-positive BC, we evaluated novel SUMO1 target proteins such as Ras and demonstrated that E2 increased Ras SUMOylation and cellular proliferation by affecting downstream signaling-pathway transduction. Finally, our data revealed that E2-ERα enhanced SUMO1 transcription to promote tumor growth in a BC orthotopic tumor model.

Conclusions

Collectively, our results showed that E2 promoted the transcription and protein expression of SUMO1 via ERα binding to a 1/2ERE in the SUMO1 promoter, and that E2-ERα also augmented SUMO1-mediated Ras SUMOylation and mediated cellular responses in ER-positive BC. We therefore achieved significant insights into the mechanism involved in ER-positive BC development and provided a novel target for its treatment.

Insight into the Potential Mechanisms of Endocrine Disruption by Dietary Phytoestrogens in the Context of the Etiopathogenesis of Endometriosis

Phytoestrogens (PEs) are estrogen-like nonsteroidal compounds derived from plants (e.g., nuts, seeds, fruits, and vegetables) and fungi that are structurally similar to 17β-estradiol. PEs bind to all types of estrogen receptors, including ERα and ERβ receptors, nuclear receptors, and a membrane-bound estrogen receptor known as the G protein-coupled estrogen receptor (GPER). As endocrine-disrupting chemicals (EDCs) with pro- or antiestrogenic properties, PEs can potentially disrupt the hormonal regulation of homeostasis, resulting in developmental and reproductive abnormalities. However, a lack of PEs in the diet does not result in the development of deficiency symptoms. To properly assess the benefits and risks associated with the use of a PE-rich diet, it is necessary to distinguish between endocrine disruption (endocrine-mediated adverse effects) and nonspecific effects on the endocrine system. Endometriosis is an estrogen-dependent disease of unknown etiopathogenesis, in which tissue similar to the lining of the uterus (the endometrium) grows outside of the uterus with subsequent complications being manifested as a result of local inflammatory reactions. Endometriosis affects 10-15% of women of reproductive age and is associated with chronic pelvic pain, dysmenorrhea, dyspareunia, and infertility. In this review, the endocrine-disruptive actions of PEs are reviewed in the context of endometriosis to determine whether a PE-rich diet has a positive or negative effect on the risk and course of endometriosis.

The mitochondrial unfolded protein response (UPRmt): shielding against toxicity to mitochondria in cancer

Mitochondria are essential for tumor growth and progression. However, the heavy demand for mitochondrial activity in cancer leads to increased production of mitochondrial reactive oxygen species (mtROS), accumulation of mutations in mitochondrial DNA, and development of mitochondrial dysfunction. If left unchecked, excessive mtROS can damage and unfold proteins in the mitochondria to an extent that becomes lethal to the tumor. Cellular systems have evolved to combat mtROS and alleviate mitochondrial stress through a quality control mechanism called the mitochondrial unfolded protein response (UPR^mt). The UPR^mt system is composed of chaperones and proteases, which promote protein folding or eliminate mitochondrial proteins damaged by mtROS, respectively. UPR^mt is conserved and activated in cancer in response to mitochondrial stress to maintain mitochondrial integrity and support tumor growth. In this review, we discuss how mitochondria become dysfunctional in cancer and highlight the tumor-promoting functions of key components of the UPR^mt.

Evolution of 3-(4-hydroxyphenyl)indoline-2-one as a scaffold for potent and selective anticancer activity

Development of targeted anticancer modalities has prompted a new era in cancer treatment that is notably different from the age of radical surgery and highly toxic chemotherapy. Behind each effective compound is a rich and complex history from first identification of chemical matter, detailed optimization, and mechanistic investigations, ultimately leading to exciting molecules for drug development. Herein we review the history and on-going journey of one such anticancer scaffold, the 3-(4-hydroxyphenyl)indoline-2-ones. With humble beginnings in 19th century Bavaria, we review this scaffold's synthetic history and anticancer optimization, including its recent demonstration of tumor eradication of drug-resistant, estrogen receptor-positive breast cancer. Compounds containing the 3-(4-hydroxyphenyl)indoline-2-one pharmacophore are emerging as intriguing candidates for the treatment of cancer.

TXNIP Links Anticipatory Unfolded Protein Response to Estrogen Reprogramming Glucose Metabolism in Breast Cancer Cells

Estrogen and estrogen receptor (ER) play a fundamental role in breast cancer. To support the rapid proliferation of ER+ breast cancer cells, estrogen increases glucose uptake and reprograms glucose metabolism. Meanwhile, estrogen/ER activates the anticipatory unfolded protein response (UPR) preparing cancer cells for the increased protein production required for subsequent cell proliferation. Here, we report that thioredoxin-interacting protein (TXNIP) is an important regulator of glucose metabolism in ER+ breast cancer cells, and estrogen/ER increases glucose uptake and reprograms glucose metabolism via activating anticipatory UPR and subsequently repressing TXNIP expression. In 2 widely used ER+ breast cancer cell lines, MCF7 and T47D, we showed that MCF7 cells express high TXNIP levels and exhibit mitochondrial oxidative phosphorylation (OXPHOS) phenotype, while T47D cells express low TXNIP levels and display aerobic glycolysis (Warburg effect) phenotype. Knockdown of TXNIP promoted glucose uptake and Warburg effect, while forced overexpression of TXNIP inhibited glucose uptake and Warburg effect. We further showed that estrogen represses TXNIP expression and activates UPR sensor inositol-requiring enzyme 1 (IRE1) via ER in the breast cancer cells, and IRE1 activity is required for estrogen suppression of TXNIP expression and estrogen-induced cell proliferation. Our study suggests that TXNIP is involved in estrogen-induced glucose uptake and metabolic reprogramming in ER+ breast cancer cells and links anticipatory UPR to estrogen reprogramming glucose metabolism.

SOX2OT Long Noncoding RNA Is Regulated by the UPR in Oestrogen Receptor-Positive Breast Cancer

Endoplasmic reticulum (ENR) stress perturbs cell homeostasis and induces the unfolded protein response (UPR). In breast cancer, this process is activated by oestrogen deprivation and is associated with tamoxifen resistance. We present evidence that the transcription factor SOX2 and the long noncoding RNA SOX2 overlapping transcript (SOX2OT) are upregulated in oestrogen receptor-positive (ER+) breast cancer and in response to oestrogen deprivation. We examined the effect of the UPR on SOX2 and SOX2OT expression and the effect of SOX2OT on UPR pathways in breast cancer cell lines. The induction of the UPR by thapsigargin or glucose deprivation upregulates SOX2OT expression. This upregulation is also shown with the anti-oestrogen 4OH-tamoxifen and mTOR inhibitor everolimus in ER + breast cancer cells that are sensitive to oestrogen deprivation or everolimus treatment. SOX2OT overexpression decreased BiP and PERK expression. This effect of SOX2OT overexpression was confirmed on BiP and PERK pathway by q-PCR. Our results show that a long noncoding RNA regulates the UPR and evince a new function of SOX2OT as a participant of ENR stress reprogramming of breast cancer cells.

Quality Matters? The Involvement of Mitochondrial Quality Control in Cardiovascular Disease

Cardiovascular diseases are one of the leading causes of death and global health problems worldwide. Multiple factors are known to affect the cardiovascular system from lifestyles, genes, underlying comorbidities, and age. Requiring high workload, metabolism of the heart is largely dependent on continuous power supply via mitochondria through effective oxidative respiration. Mitochondria not only serve as cellular power plants, but are also involved in many critical cellular processes, including the generation of intracellular reactive oxygen species (ROS) and regulating cellular survival. To cope with environmental stress, mitochondrial function has been suggested to be essential during bioenergetics adaptation resulting in cardiac pathological remodeling. Thus, mitochondrial dysfunction has been advocated in various aspects of cardiovascular pathology including the response to ischemia/reperfusion (I/R) injury, hypertension (HTN), and cardiovascular complications related to type 2 diabetes mellitus (DM). Therefore, mitochondrial homeostasis through mitochondrial dynamics and quality control is pivotal in the maintenance of cardiac health. Impairment of the segregation of damaged components and degradation of unhealthy mitochondria through autophagic mechanisms may play a crucial role in the pathogenesis of various cardiac disorders. This article provides in-depth understanding of the current literature regarding mitochondrial remodeling and dynamics in cardiovascular diseases.

Potential roles of natural products in the targeting of proteinopathic neurodegenerative diseases

Defective proteostasis is associated with the gradual accumulations of misfolded proteins and is a hallmark of many age-associated neurodegenerative diseases. In the aged brain, maintenance of the proteostasis network presents a substantial challenge, and its loss contributes to the onset and progression of neurological diseases associated with cognitive decline due to the generation of toxic protein aggregates, a process termed 'proteinopathy'. Emerging evidence suggests that reversing proteinopathies by boosting proteostasis might provide an effective means of preventing neurodegeneration. From this perspective, phytochemicals may play significant roles as potent modulators of the proteostasis network, as previous reports have suggested they can interact with various network components to modify pathologies and confer neuroprotection. This review focuses on some potent phytochemicals that directly or indirectly modulate the proteostasis network and on their possible molecular targets. In addition, we propose strategies for the natural product-based modulation of proteostasis machinery that target proteinopathies.

(E)-4-(3-(3-(4-Methoxyphenyl)acryloyl)phenoxy)butyl 2-Hydroxybenzoate

A new hybrid compound of chalcone-salicylate (title compound) has been successfully synthesized using a linker mode approach under reflux condition. The structure of the title compound has been established by spectroscopic analysis including UV-Vis, FT-IR, HRMS, 1D, and 2D NMR. Then, computational approach was also applied in this study through molecular docking and MD simulation to explore its potency against breast cancer. The results of the molecular docking study showed that the title compound exhibited more negative value of binding free energy (−8.15 kcal/mol) than tamoxifen (−7.00 kcal/mol). In addition, no striking change in the positioning of the interacting residues was recorded before and after the MD simulations. Based on the studies, it can be predicted that the title compound has a cytotoxic activity potency against breast cancer through ERα inhibition and it presumably can be developed as anticancer agent candidate.

Secondary Resistant Mutations to Small Molecule Inhibitors in Cancer Cells

Secondary resistant mutations in cancer cells arise in response to certain small molecule inhibitors. These mutations inevitably cause recurrence and often progression to a more aggressive form. Resistant mutations may manifest in various forms. For example, some mutations decrease or abrogate the affinity of the drug for the protein. Others restore the function of the enzyme even in the presence of the inhibitor. In some cases, resistance is acquired through activation of a parallel pathway which bypasses the function of the drug targeted pathway. The Catalogue of Somatic Mutations in Cancer (COSMIC) produced a compendium of resistant mutations to small molecule inhibitors reported in the literature. Here, we build on these data and provide a comprehensive review of resistant mutations in cancers. We also discuss mechanistic parallels of resistance.

SOX2OT Long Noncoding RNA Is Regulated by the UPR in Oestrogen Receptor-Positive Breast Cancer

Endoplasmic reticulum (ER) stress perturbs cell homeostasis and induces the unfolded protein response (UPR). In breast cancer, this process is activated by oestrogen deprivation and is associated with tamoxifen resistance. We present evidence that the transcription factor SOX2 and the long noncoding RNA SOX2 overlapping transcript (SOX2OT) are up-regulated in oestrogen receptor-positive (ER+) breast cancer and in response to oestrogen deprivation. We examined the effect of the UPR on SOX2 and SOX2OT expression, and the effect of SOX2OT on UPR pathways in breast cancer cell lines. The induction of the UPR by thapsigargin or glucose deprivation up-regulates SOX2OT expression. This up-regulation is also shown with the anti-oestrogen 4OH-tamoxifen and mTOR inhibitor everolimus in ER + breast cancer cells that are sensitive to oestrogen deprivation or everolimus treatment. SOX2OT overexpression decreased BiP and PERK expression. This effect of SOX2OT overexpression was confirmed on BiP and PERK pathway by q-PCR. Our results show that a long noncoding RNA regulates the UPR and evince a new function of SOX2OT as a participant of ER stress reprogramming of breast cancer cells.

Growth hormone releasing hormone in the unfolded protein response context

The effects of Growth Hormone Releasing Hormone in human pathophysiology are not limited to those mediated by the Growth Hormone Releasing Hormone-Growth Hormone-Insulin-like Growth Factor-I axis. Receptors specific for this neuropeptide are expressed in a diverse variety of human tissues, to initiate multifarious signaling cascades, regulators of cellular homeostasis and survival. The Unfolded Protein Response is in charge of adaptive responses towards a plethora of challenges, able to trigger cellular repair or death. The possible involvement of Growth Hormone Releasing Hormone and its agonistic and antagonistic analogs in those events, may deliver exciting possibilities in the treatment of human disease, including the Acute Respiratory Distress Syndrome.

Resveratrol up-regulates ATP2A3 gene expression in breast cancer cell lines through epigenetic mechanisms

Resveratrol (RSV) is a phytoestrogen which has been related to chemoprevention of several types of cancer. In this work, we show up to a 6-fold increased expression of ATP2A3 gene induced by RSV that triggers apoptosis and changes of intracellular Ca²⁺ management in MCF-7 and MDA-MB-231 breast cancer cell lines. We explored epigenetic mechanisms for that RSV-induced ATP2A3 up-regulation. The results indicate that RSV-induced ATP2A3 up-regulation correlates with about 50% of reduced HDAC activity and reduced nuclear HDAC2 expression and occupancy on ATP2A3 promoter, increasing the global acetylation of histone H3 and the enrichment of histone mark H3K27Ac on the proximal promoter of the ATP2A3 gene in MDA-MB-231 cells. We also quantified HAT activity, finding that it can be boosted with RSV treatment; however, pharmacological inhibition of p300, one of the main HATs, did not have significant effects in RSV-mediated ATP2A3 gene expression. Additionally, DNMT activity was also reduced in cells treated with RSV, as well as the expression of Methyl-DNA binding proteins MeCP2 and MBD2. However, analysis of the methylation pattern of ATP2A3 gene promoter showed un-methylated promoter in both cell lines. Taken together, the results of this work help to explain, at the molecular level, how ATP2A3 gene is regulated in breast cancer cells, and the benefits of RSV intake observed in epidemiological data, studies with animals, and in vitro models.