Combined estrogenic and anti-estrogenic properties of estetrol on breast cancer may provide a safe therapeutic window for the treatment of menopausal symptoms

Estetrol Inhibits Endometriosis Development in an In Vivo Murine Model

Endometriosis is characterized by the growth of endometrial-like tissue outside the uterus, and it is associated with alterations in the expression of hormone receptors and inflammation. Estetrol (E4) is a weak estrogen that recently has been approved for contraception. We evaluated the effect of E4 on the growth of endometriotic-like lesions and the expression of TNF-α, estrogen receptors (ERs), and progesterone receptors (PRs) in an in vivo murine model. Endometriosis was induced surgically in female C57BL/6 mice. E4 was delivered via Alzet pump (3 mg/kg/day) from the 15th postoperative day for 4 weeks. E4 significantly reduced the volume (p < 0.001) and weight (p < 0.05) of ectopic lesions. Histologically, E4 did not affect cell proliferation (PCNA immunohistochemistry) but it did increase cell apoptosis (TUNEL assay) (p < 0.05). Furthermore, it modulated oxidative stress (SOD, CAT, and GPX activity, p < 0.05) and increased lipid peroxidation (TBARS/MDA, p < 0.01). Molecular analysis showed mRNA (RT-qPCR) and protein (ELISA) expression of TNF-α decreased (p < 0.05) and mRNA expression of Esr2 reduced (p < 0.05), in contrast with the increased expression of Esr1 (p < 0.01) and Pgr (p < 0.05). The present study demonstrates for the first time that E4 limited the development and progression of endometriosis in vivo.

Estetrol/GPER/SERPINB2 transduction signaling inhibits the motility of triple-negative breast cancer cells

BACKGROUND

Estetrol (E4) is a natural estrogen produced by the fetal liver during pregnancy. Due to its favorable safety profile, E4 was recently approved as estrogenic component of a new combined oral contraceptive. E4 is a selective ligand of estrogen receptor (ER)α and ERβ, but its binding to the G Protein-Coupled Estrogen Receptor (GPER) has not been described to date. Therefore, we aimed to explore E4 action in GPER-positive Triple-Negative Breast Cancer (TNBC) cells.

METHODS

The potential interaction between E4 and GPER was investigated by molecular modeling and binding assays. The whole transcriptomic modulation triggered by E4 in TNBC cells via GPER was explored through high-throughput RNA sequencing analyses. Gene and protein expression evaluations as well as migration and invasion assays allowed us to explore the involvement of the GPER-mediated induction of the plasminogen activator inhibitor type 2 (SERPINB2) in the biological responses triggered by E4 in TNBC cells. Furthermore, bioinformatics analysis was aimed at recognizing the biological significance of SERPINB2 in ER-negative breast cancer patients.

RESULTS

After the molecular characterization of the E4 binding capacity to GPER, RNA-seq analysis revealed that the plasminogen activator inhibitor type 2 (SERPINB2) is one of the most up-regulated genes by E4 in a GPER-dependent manner. Worthy, we demonstrated that the GPER-mediated increase of SERPINB2 is engaged in the anti-migratory and anti-invasive effects elicited by E4 in TNBC cells. In accordance with these findings, a correlation between SERPINB2 levels and a good clinical outcome was found in ER-negative breast cancer patients.

CONCLUSIONS

Overall, our results provide new insights into the mechanisms through which E4 can halt migratory and invasive features of TNBC cells.

Interrogating Estrogen Signaling Pathways in Human ER-Positive Breast Cancer Cells Forming Bone Metastases in Mice

Breast cancer bone metastases (BMET) are incurable, primarily osteolytic, and occur most commonly in estrogen receptor-α positive (ER+) breast cancer. ER+ human breast cancer BMET modeling in mice has demonstrated an estrogen (E2)-dependent increase in tumor-associated osteolysis and bone-resorbing osteoclasts, independent of estrogenic effects on tumor proliferation or bone turnover, suggesting a possible mechanistic link between tumoral ERα-driven osteolysis and ER+ bone progression. To explore this question, inducible secretion of the osteolytic factor, parathyroid hormone-related protein (PTHrP), was utilized as an in vitro screening bioassay to query the osteolytic potential of estrogen receptor- and signaling pathway-specific ligands in BMET-forming ER+ human breast cancer cells expressing ERα, ERß, and G protein-coupled ER. After identifying genomic ERα signaling, also responsibility for estrogen's proliferative effects, as necessary and sufficient for osteolytic PTHrP secretion, in vivo effects of a genomic-only ER agonist, estetrol (E4), on osteolytic ER+ BMET progression were examined. Surprisingly, while pharmacologic effects of E4 on estrogen-dependent tissues, including bone, were evident, E4 did not support osteolytic BMET progression (vs robust E2 effects), suggesting an important role for nongenomic ER signaling in ER+ metastatic progression at this site. Because bone effects of E4 did not completely recapitulate those of E2, the relative importance of nongenomic ER signaling in tumor vs bone cannot be ascertained here. Nonetheless, these intriguing findings suggest that targeted manipulation of estrogen signaling to mitigate ER+ metastatic progression in bone may require a nuanced approach, considering genomic and nongenomic effects of ER signaling on both sides of the tumor/bone interface.

Comparison of Estetrol Exposure between Women and Mice to Model Preclinical Experiments and Anticipate Human Treatment

Estetrol (E4) is a natural estrogen with promising therapeutic applications in humans. The European Medicines Agency and the Food and Drug Administration have approved the use of 15 mg E4/3 mg drospirenone for contraceptive indication. Phase III clinical trials with 15-20 mg E4 for the relief of climacteric complaints are currently running. Relevant data from preclinical animal models are needed to characterize the molecular mechanisms and the pharmacological effects of E4 and possibly to reveal new therapeutic applications and to anticipate potential adverse effects. Therefore, it is important to design experimental procedures in rodents that closely mimic or anticipate human E4 exposure. In this study, we compared the effects of E4 exposure after acute or chronic administration in women and mice. Women who received chronic E4 treatment per os at a dose of 15 mg once daily reached a steady state within 6 to 8 days, with a mean plasma concentration of 3.20 ng/mL. Importantly, with subcutaneous, intraperitoneal or oral administration of E4 in mice, a stable concentration over time that would mimic human pharmacokinetics could not be achieved. The use of osmotic minipumps continuously releasing E4 for several weeks provided an exposure profile mimicking chronic oral administration in women. Measurements of the circulating concentration of E4 in mice revealed that the mouse equivalent dose necessary to mimic human treatment does not fit with the allometric prediction. In conclusion, this study highlights the importance of precise definition of the most appropriate dose and route of administration to utilize when developing predictive preclinical animal models to mimic or anticipate specific human treatment.

Estetrol: From Preclinical to Clinical Pharmacology and Advances in the Understanding of the Molecular Mechanism of Action

Estetrol (E4) is the most recently described natural estrogen. It is produced by the human fetal liver during pregnancy and its physiological function remains unclear. E4 is the estrogenic component of a recently approved combined oral contraceptive. It is also in development for use as menopausal hormone therapy. In the context of these developments, the pharmacological activity of E4, alone or in combination with a progestin, has been extensively characterized in preclinical models as well as in clinical studies in women of reproductive age and postmenopausal women. Despite the clinical benefits, the use of oral estrogens for contraception or menopause is also associated with unwanted effects, such as an increased risk of breast cancer and thromboembolic events, due to their impact on non-target tissues. Preclinical and clinical data for E4 point to a tissue-specific activity and a more selective pharmacological profile compared with other estrogens, including a low impact on the liver and hemostasis balance. This review summarizes the characterization of the pharmacological properties of E4 as well as recent advances made in the understanding of the molecular mechanisms of action driving its activity. How the unique mode of action and the different metabolism of E4 might support its favorable benefit-risk ratio is also discussed.

Estetrol Increases Progesterone Genetic Response without Triggering Common Estrogenic Effects in Endometriotic Cell Lines and Primary Cultures

Estetrol (E4), a natural estrogen produced by the human fetal liver, is actively studied for menopause and breast cancer treatment. It has low side effects and preferential estrogen receptor alpha (ERα) affinity. There are no data about its effects on endometriosis, a common gynecological disease affecting 6-10% of cycling women, generating painful pelvic lesions and infertility. Current combined hormone treatment (progestins and estrogens) is safe and efficient; nevertheless, one-third of patients develop progesterone (P4) resistance and recurrence by reducing P4 receptors (PRs) levels. We aimed to compare E4 and 17β-estradiol (E2) effects using two human endometriotic cell lines (epithelial 11Z and stromal Hs832 cells) and primary cultures from endometriotic patients. We evaluated cell growth (MTS), migration (wound assay), hormone receptors levels (Western blot), and P4 response by PCR array. Compared to E2, E4 did not affect cell growth or migration but increased estrogen receptor alpha (ERα) and PRs, and reduced ERβ. Finally, the incubation with E4 improved the P4 gene response. In conclusion, E4 increased PRs levels and genetic response without inducing cell growth or migration. These results suggest that E4 might be useful for endometriosis treatment avoiding P4 resistance; however, evaluating its response in more complex models is required.

Profile of estetrol, a promising native estrogen for oral contraception and the relief of climacteric symptoms of menopause

INTRODUCTION

Estrogens used in women's healthcare have been associated with increased risks of venous thromboembolism (VTE) and breast cancer. Estetrol (E4), an estrogen produced by the human fetal liver, has recently been approved for the first time as a new estrogenic component of a novel combined oral contraceptive (E4/drospirenone [DRSP]) for over a decade. In phase 3 studies, E4/DRSP showed good contraceptive efficacy, a predictable bleeding pattern, and a favorable safety and tolerability profile.

AREAS COVERED

This narrative review discusses E4's pharmacological characteristics, mode of action, and the results of preclinical and clinical studies for contraception, as well as for menopause and oncology.

EXPERT OPINION

Extensive studies have elucidated the properties of E4 that underlie its favorable safety profile. While classical estrogens (such as estradiol) exert their actions via both activation of nuclear and membrane estrogen receptor α (ERα), E4 presents a specific profile of ERα activation: E4 binds and activates nuclear ERα but does not induce the activation of membrane ERα signaling pathways in specific tissues. E4 has a small effect on normal breast tissue proliferation and minimally affects hepatic parameters. This distinct profile of ERα activation, uncoupling nuclear and membrane activation, is unique.

Combined Oral Contraceptives and Venous Thromboembolism: Review and Perspective to Mitigate the Risk

Many factors must be considered and discussed with women when initiating a contraceptive method and the risk of venous thromboembolism (VTE) is one of them. In this review, we discuss the numerous strategies that have been implemented to reduce the thrombotic risk associated with combined oral contraceptives (COCs) from their arrival on the market until today. Evidences suggesting that COCs were associated with an increased risk of VTE appeared rapidly after their marketing. Identified as the main contributor of this risk, the dosage of the estrogen, i.e., ethinylestradiol (EE), was significantly reduced. New progestins were also synthetized (e.g., desogestrel or gestodene) but their weak androgenic activity did not permit to counterbalance the effect of EE as did the initial progestins such as levonorgestrel. Numerous studies assessed the impact of estroprogestative combinations on hemostasis and demonstrated that women under COC suffered from resistance towards activated protein C (APC). Subsequently, the European Medicines Agency updated its guidelines on clinical investigation of steroid contraceptives in which they recommended to assess this biological marker. In 2009, estradiol-containing COCs were marketed and the use of this natural form of estrogen was found to exert a weaker effect on the synthesis of hepatic proteins compared to EE. In this year 2021, a novel COC based on a native estrogen, i.e., estetrol, will be introduced on the market. Associated with drospirenone, this preparation demonstrated minor effects on coagulation proteins as compared with other drospirenone-containing COCs. At the present time, the standard of care when starting a contraception, consists of identifying the presence of hereditary thrombophilia solely on the basis of familial history of VTE. This strategy has however been reported as poorly predictive of hereditary thrombophilia. One rationale and affordable perspective which has already been considered in the past could be the implementation of a baseline screening of the prothrombotic state to provide health care professionals with objective data to support the prescription of the more appropriate contraceptive method. While this strategy was judged too expensive due to limited laboratory solutions, the endogenous thrombin potential-based APC resistance assay could now represent an interesting alternative.

Selective Estrogen Receptor Modulators in Gynecology Practice

Selective estrogen receptor (ER) modulators have variable tissue specific estrogen agonist and antagonist activities. Tamoxifen is approved for treatment and prevention of breast cancer; acts as an endometrial estrogen agonist. Raloxifene is approved for prevention and treatment of osteoporosis and prevention of breast cancer. The selective ER modulators bazedoxifene paired with conjugated estrogens relieves vasomotor symptoms and prevents bone loss with neutral effects on breast and amenorrhea similar to placebo. Ospemifene is approved to treat dyspareunia. Lasofoxifene is in development for resistant ER positive breast cancer. Estetrol (E4), synthesized by human fetal liver, has dual weak-estrogenic/antiestrogenic features, now approved as a contraceptive.

Estetrol and Mammary Gland: Friends or Foes?

Estrogens have pleiotropic effects on many reproductive and non-reproductive tissues and organs including the mammary gland, uterus, ovaries, vagina, and endothelium. Estrogen receptor α functions as the principal mediator of estrogenic action in most of these tissues. Estetrol (E4) is a native fetal estrogen with selective tissue actions that is currently approved for use as the estrogen component in a combined oral contraceptive and is being developed as a menopause hormone therapy (MHT, also known as hormone replacement therapy). However, exogenous hormonal treatments, in particular MHTs, have been shown to promote the growth of preexisting breast cancers and are associated with a variable risk of breast cancer depending on the treatment modality. Therefore, evaluating the safety of E4-based formulations on the breast forms a crucial part of the clinical development process. This review highlights preclinical and clinical studies that have assessed the effects of E4 and E4-progestogen combinations on the mammary gland and breast cancer, focusing in particular on the estrogenic and anti-estrogenic properties of E4. We discuss the potential advantages of E4 over current available estrogen-formulations as a contraceptive and for the treatment of symptoms due to menopause. We also consider the potential of E4 for the treatment of endocrine-resistant breast cancer.

Estetrol Combined to Progestogen for Menopause or Contraception Indication Is Neutral on Breast Cancer

Simple Summary

Hormonal treatments, especially those used to treat menopause symptoms are known to increase breast cancer risk. It is thus necessary to identify new formulations with a better benefit/risk profile. The aim of this translational study was to evaluate the breast cancer risk associated with a combination of a natural estrogen named estetrol, with progestogens such as natural progesterone and drospirenone. Since the assessment of breast cancer risk in patients during drug development is not possible given the requirement of long-term studies in large populations, this study provides new evidence that a therapeutic dose of estetrol for menopause treatment or contraception, combined with progesterone or drospirenone, may provide a better benefit/risk profile toward breast cancer risk compared to the hormonal treatments currently available for patients.

Abstract

Given the unequivocal benefits of menopause hormone therapies (MHT) and combined oral contraceptives (COC), there is a clinical need for new formulations devoid of any risk of breast cancer promotion. Accumulating data from preclinical and clinical studies support that estetrol (E4) is a promising natural estrogen for MHT and COC. Nevertheless, we report here that E4 remains active on the endometrium, even under a dose that is neutral on breast cancer growth and lung metastasis dissemination. This implies that a progestogen should be combined with E4 to protect the endometrium of non-hysterectomized women from hyperplasia and cancer. Through in vivo observations and transcriptomic analyses, our work provides evidence that combining a progestogen to E4 is neutral on breast cancer growth and dissemination, with very limited transcriptional impact. The assessment of breast cancer risk in patients during the development of new MHT or COC is not possible given the requirement of long-term studies in large populations. This translational preclinical research provides new evidence that a therapeutic dose of E4 for MHT or COC, combined with progesterone or drospirenone, may provide a better benefit/risk profile towards breast cancer risk compared to hormonal treatments currently available for patients.

Osteolytic effects of tumoral estrogen signaling in an estrogen receptor-positive breast cancer bone metastasis model

AIM

Estrogen receptor α-positive (ER+) subtypes of breast cancer have the greatest predilection for forming osteolytic bone metastases (BMETs). Because tumor-derived factors mediate osteolysis, a possible role for tumoral ERα signaling in driving ER+ BMET osteolysis was queried using an estrogen (E2)-dependent ER+ breast cancer BMET model.

METHODS

Female athymic Foxn1nu mice were inoculated with human ER+ MCF-7 breast cancer cells via the left cardiac ventricle post-E2 pellet placement, and age- and dose-dependent E2 effects on osteolytic ER+ BMET progression, as well as direct bone effects of E2, were determined.

RESULTS

Osteolytic BMETs, which did not form in the absence of E2 supplementation, occurred with the same frequency in young (5-week-old) vs. skeletally mature (16-week-old) E2 (0.72 mg)-treated mice, but were larger in young mice where anabolic bone effects of E2 were greater. However, in mice of a single age and across a range of E2 doses, anabolic E2 bone effects were constant, while osteolytic ER+ BMET lesion incidence and size increased in an E2-dose-dependent fashion. Osteoclasts in ER+ tumor-bearing (but not tumor-naive) mice increased in an E2-dose dependent fashion at the bone-tumor interface, while histologic tumor size and proliferation did not vary with E2 dose. E2-inducible tumoral secretion of the osteolytic factor parathyroid hormone-related protein (PTHrP) was dose-dependent and mediated by ERα, with significantly greater levels of secretion from ER+ BMET-derived tumor cells.

CONCLUSION

These results suggest that tumoral ERα signaling may contribute to ER+ BMET-associated osteolysis, potentially explaining the greater predilection for ER+ tumors to form clinically-evident osteolytic BMETs.

Pharmacology and Molecular Mechanisms of Clinically Relevant Estrogen Estetrol and Estrogen Mimic BMI-135 for the Treatment of Endocrine-Resistant Breast Cancer

Long-term estrogen deprivation (LTED) with tamoxifen (TAM) or aromatase inhibitors leads to endocrine-resistance, whereby physiologic levels of estrogen kill breast cancer (BC). Estrogen therapy is effective in treating patients with advanced BC after resistance to TAM and aromatase inhibitors develops. This therapeutic effect is attributed to estrogen-induced apoptosis via the estrogen receptor (ER). Estrogen therapy can have unpleasant gynecologic and nongynecologic adverse events. Here, we study estetrol (E4) and a model Selective Human ER Partial Agonist (ShERPA) BMI-135. Estetrol and ShERPA TTC-352 are being evaluated in clinical trials. These agents are proposed as safer estrogenic candidates compared with 17β-estradiol (E2) for the treatment of endocrine-resistant BC. Cell viability assays, real-time polymerase chain reaction, luciferase reporter assays, chromatin immunoprecipitation, docking and molecular dynamics simulations, human unfolded protein response (UPR) RT2 PCR profiler arrays, live cell microscopic imaging and analysis, and annexin V staining assays were conducted. Our work was done in eight biologically different human BC cell lines and one human endometrial cancer cell line, and results were compared with full agonists estrone, E2, and estriol, a benchmark partial agonist triphenylethylene bisphenol (BPTPE), and antagonists 4-hydroxytamoxifen and endoxifen. Our study shows the pharmacology of E4 and BMI-135 as less-potent full-estrogen agonists as well as their molecular mechanisms of tumor regression in LTED BC through triggering a rapid UPR and apoptosis. Our work concludes that the use of a full agonist to treat BC is potentially superior to a partial agonist given BPTPE's delayed induction of UPR and apoptosis, with a higher probability of tumor clonal evolution and resistance. SIGNIFICANCE STATEMENT: Given the unpleasant gynecologic and nongynecologic adverse effects of estrogen treatment, the development of safer estrogens for endocrine-resistant breast cancer (BC) treatment and hormone replacement therapy remains a priority. The naturally occurring estrogen estetrol and Selective Human Estrogen-Receptor Partial Agonists are being evaluated in endocrine-resistant BC clinical trials. This work provides a comprehensive evaluation of their pharmacology in numerous endocrine-resistant BC models and an endometrial cancer model and their molecular mechanisms of tumor regression through the unfolded protein response and apoptosis.

Beyond estrogen: advances in tissue selective estrogen complexes and selective estrogen receptor modulators

Selective estrogen receptor modulators (SERMs) are synthetic non-steroidal agents which have variable estrogen agonist and antagonist activities in different target tissues. Tamoxifen is an anti-estrogen in the breast used for treatment and prevention of breast cancer, with estrogen agonist activity in the uterus. Raloxifene prevents and treats osteoporosis and prevents breast cancer, and can be safely combined with vaginal but not systemic estrogen. The tissue selective estrogen complex combines conjugated equine estrogens (CEE) with the SERM bazedoxifene (BZA). The five Selective Estrogen Menopause and Response to Therapy studies, with up to 2 years of data, demonstrated that CEE/BZA 0.45 mg/BZA 20 mg improved vasomotor symptoms and vulvovaginal atrophy, prevented bone loss, and was neutral on breast tenderness, breast density, with breast cancer incidence similar to placebo. Protection against estrogen-induced endometrial hyperplasia and cancer was found, with similar amenorrhea rates to placebo. Ospemifene is approved to treat dyspareunia, with potential benefits on bone and the breast, while lasofoxifene is being developed to treat resistant estrogen receptor-positive breast cancer in women. Estetrol is an estrogen synthesized exclusively during pregnancy by the human fetal liver and initially considered a weak estrogen, but it appears to have dual weak estrogenic/anti-estrogenic features.

Method Development for Effect-Directed Analysis of Endocrine Disrupting Compounds in Human Amniotic Fluid

The developing fetus represents a highly sensitive period of exposure to endocrine disrupting compounds (EDCs). However, risk assessment of EDCs is hampered by the lack of data on direct in utero exposure. In this study, we developed a robust analytical methodology for the identification of a wide range of known and unknown EDCs in full-term amniotic fluid (AF). First, a method for extraction and fractionation of a broad range of polar and nonpolar EDCs was developed and validated. Maximal recoveries of reference compounds and minimal interference from the matrix were achieved with a combination of solid phase extraction and dispersive liquid/liquid extraction. Bioassay analysis using cell-based reporter gene assays revealed estrogenic, androgenic, and dioxin-like activity in AF extract corresponding to 1.4 nmol EEQ/L, 76.6 pmol DHT-EQ/L, and 10.1 pmol TEQ/L, respectively. Targeted analysis revealed 13 xenobiotics, phytoestrogens, and endogenous hormones in the AF extract that partly contributed to the bioassay activity. Separation of the complex mixture of chemicals in the AF extract with reversed-phase chromatographic fractionation and subsequent bioassay analysis revealed activity in fractions over a wide range of polarity, indicating diverse (unidentified) substances with potential ED activity. The method developed here represents the first methodological step in an effect-directed analysis approach to identify unknown biologically active compounds in the fetal environment.

Obesity as potential breast cancer risk factor for postmenopausal women

Breast cancer is the second highest prevalent cancer globally after lung cancer with 2.09 million cases during 2018. Adults about 1.9 billion were overweight and over 650 million out of these were obese during 2016. There is a significant relationship between breast cancer risk and obesity. Premature menopause and premenopausal obesity diminish the risk whereas postmenopausal obesity amplifies the risk, because adipose tissue acts as the major reservoir for estrogen biosynthesis after menopause. Lofty estrogen levels in serum along with enhanced peripheral site production of estrogen have been viewed as major reasons of developing breast cancer in overweight postmenopausal women. This review explains body fat as a peripheral site for estrogen biosynthesis, estrogen exposure affecting body fat distribution, and the mechanism of estrogen production from body fats.

Insight Analysis of Promiscuous Estrogen Receptor α-Ligand Binding by a Novel Machine Learning Scheme

Estrogen receptor α (ERα) plays a significant role in occurrence of breast cancer and may cause various adverse side-effects when ERα is an off-target protein. A theoretical model was derived to predict the binding affinity of ERα using the pharmacophore ensemble/support vector machine (PhE/SVM) scheme to consider the promiscuous characteristic of ERα. The estimations by PhE/SVM were discovered to be in good agreement with the observed values for those training molecules ( n = 31, r² = 0.80, q_CV² = 0.77, RMSE = 0.57, s = 0.58), test molecules ( n = 179, q² = 0.91-0.96, RMSE = 0.33, s = 0.26) and outliers ( n = 15, q² = 0.80-0.86, RMSE = 0.56, s = 0.49). When subjected to various statistical validations, the PhE/SVM model consistently fulfilled the strictest criteria. A mock test also asserted its predictivity. When compared with crystal structures, the calculated results are consistent with the reported ERα-ligand co-complex structure, and the plasticity nature of ERα is also disclosed. Consequently, this precise, fast, and robust model can be adopted to predict ERα-ligand binding affinities and to design safer non-ERα-targeted pharmaceuticals in the process of drug discovery and development.

Estriol: emerging clinical benefits

OBJECTIVE

Estriol is the main estrogen in pregnancy, but has received less attention outside gestation. It is well known that pregnancy has an immunosuppressive effect on many autoimmune diseases such as multiple sclerosis, psoriasis, thyroiditis, uveitis, and rheumatoid arthritis. Emerging evidence indicates that estriol has potential immunomodulatory benefits for many disease states including autoimmune, inflammatory, and neurodegenerative conditions. In this review, we discuss emerging roles for estriol in the treatment of menopausal symptoms, osteoporosis, cancer, hyperlipidemia, vascular disease, and multiple sclerosis. Estriol appears to offer a potentially cost-effective approach to a variety of conditions and may offer a wide range of health benefits.

METHODS

We reviewed the English language MEDLINE literature with estriol in the title with emphasis on publications including nonpregnant females between January 1974 and August 2016. Approximately 393 such articles were considered and 72 articles have been referenced in this review.

RESULTS

Estriol offers considerable benefits for postmenopausal women with reduced risks that are normally associated with traditional hormone therapies. These benefits include improved control of menopausal symptoms and better urogenital health. Moreover, the immunomodulatory role of estriol in reducing proinflammatory cytokines may be an important new therapeutic option for chronic autoimmune and neurodegenerative illnesses. Since it is a relatively weak estrogen, there is potential for use in men for conditions such as multiple sclerosis.

CONCLUSIONS

We conclude transvaginal estriol potentially offers a suitable physiologic delivery and cost-effective alternative to currently available estrogen regimens in selected patients. Additional studies on mode of delivery, safety, and efficacy merit further investigation.

Obesity and breast cancer - Role of estrogens and the molecular underpinnings of aromatase regulation in breast adipose tissue

One in eight women will develop breast cancer over their lifetime making it the most common female cancer. The cause of breast cancer is multifactorial and includes hormonal, genetic and environmental cues. Obesity is now an accepted risk factor for breast cancer in postmenopausal women, particularly for the hormone-dependent subtype of breast cancer. Obesity, which is characterized by an excess accumulation of body fat, is at the origin of chronic inflammation of white adipose tissue and is associated with dramatic changes in the biology of adipocytes leading to their dysfunction. Inflammatory factors found in the breast of obese women considerably impact estrogen signaling, mainly by driving changes in aromatase expression the enzyme responsible for estrogen production, and therefore promote tumor formation and progression. There is thus a strong link between adipose inflammation and estrogen biosynthesis and their signaling pathways converge in obese patients. This review describes how obesity-related factors can affect the risk of hormone-dependent breast cancer, highlighting the different molecular mechanisms and metabolic pathways involved in aromatase regulation, estrogen production and breast malignancy in the context of obesity.

Pharmacodynamic effects of the fetal estrogen estetrol in postmenopausal women: results from a multiple-rising-dose study

OBJECTIVE

Estetrol (E4) is an estrogen produced exclusively by the human fetal liver during pregnancy. In this study the pharmacodynamic effects of escalating doses of E4 in postmenopausal women were investigated.

METHODS

This was a partly randomized, open-label, multiple-rising-dose study in 49 postmenopausal women. Participants were randomized to receive either 2 mg E4 or 2 mg estradiol-valerate (E2 V) for 28 days. Subsequent dose-escalation groups were (non-randomized): 10, 20 and 40 mg E4. Blood samples were collected regularly for measuring endocrine and hemostasis variables, lipids and lipoproteins, fasting glucose and bone turnover markers.

RESULTS

Estetrol treatment resulted in a decrease of follicle-stimulating hormone and luteinizing hormone and an increase of sex-hormone binding globulin. Changes in hemostasis variables were small. A lowering effect on low-density lipoprotein cholesterol was accompanied with an increase in high-density lipoprotein cholesterol and no or minimal changes in triglycerides. The considerable decrease in osteocalcin levels in the three highest E4 dose groups and the small decrease in C-telopeptide levels were comparable to the E2 V control group and suggest a preventive effect on bone loss. All changes observed were dose-dependent.

CONCLUSIONS

In this study, estetrol treatment showed dose-dependent estrogenic effects on endocrine parameters, bone turnover markers, and lipids and lipoproteins. The effect on triglycerides was small as were the effects on hemostatic variables. These results support the further investigation of estetrol as a candidate for hormone therapy. Quantitatively, the effects of 10 mg estetrol were similar to the study comparator 2 mg estradiol valerate.

Concentration of sulfated glycosaminoglycans in the mammary tissue of female rats with the aging and about hormonal influence

It was to evaluate the concentration of sulfate glycosaminoglycans (GAG) in mammary tissue of the young and adult female rats and ovariectomized females rats after hormonal stimulation. For this purpose, 60 female rats were divided into six groups with 10 animals/each: nonovariectomized groups: G1 (5 months), and G2 (15 months) and ovariectomized groups: OG (vehicle); EG: (estradiol, 7 days of treatment), PG (progesterone acetate, 23 days of treatment) and EPG: (estradiol (7 days of treatment) and next progesterone acetate (23 days of treatment). Twenty-four hours after the last treatment, all animals were euthanized, the mammary tissue removed, processed for biochemical evaluation and quantification of the GAG. The comparison between groups showed that the concentration dermatan sulfate (DS) G1 was lower compared to G2, OG, EG (p < .05) and G2 was lower compared to OG (p < .05), and OG was higher compared to EG, GP, EPG (p < .05); and heparan sulfate (HS) G1 was higher compared to G2 (p < .05), and G2 was higher compared to OG, EP, PG and EPG (p < .05). These changes in the extracellular matrix might explain, at least in part, hormonal influence about sulfated glycosaminoglycans in response to physiological state/age, and in response to hormonal treatment in the mammary tissues.

Managing Menopausal Symptoms and Associated Clinical Issues in Breast Cancer Survivors

OBJECTIVE

Review evidence to guide management of menopausal signs and symptoms in women after breast cancer and make recommendations accordingly.

EVIDENCE

Randomized controlled clinical trials, observational studies, evidence-based guidelines, and expert opinion from professional societies.

BACKGROUND

Symptoms and clinical problems associated with estrogen depletion-sleep disorders, vulvovaginal atrophy (VVA), vasomotor symptoms (VMS), mood changes, depressive symptoms, cardiovascular disease, osteopenia, and osteoporosis-confront the estimated 9.3 million breast cancer survivors globally.

RECOMMENDATIONS

Following breast cancer, women should not generally be treated with menopausal hormone therapy or tibolone but should optimize lifestyle. Women with moderate to severe symptoms may benefit from mind-brain behavior or nonhormone, pharmacologic therapy. The selective serotonin/noradrenaline reuptake inhibitors and gabapentenoid agents improve VMS and quality of life. For osteoporosis, nonhormonal agents are available. Treatment of VVA remains an area of unmet need. Low-dose vaginal estrogen is absorbed in small amounts with blood levels remaining within the normal postmenopausal range but could potentially stimulate occult breast cancer cells, and although poorly studied, is not generally advised, particularly for those on aromatase inhibitors. Intravaginal dehydroepiandrosterone and oral ospemiphene have been approved to treat dyspareunia, but safety after breast cancer has not been established. Vaginal laser therapy is being used for VVA but efficacy from sham-controlled studies is lacking. Therapies undergoing development include lasofoxifene, neurokinin B inhibitors, stellate ganglion blockade, vaginal testosterone, and estetrol.

CONCLUSIONS

Nonhormone options and therapies are available for treatment of estrogen depletion symptoms and clinical problems after a diagnosis of breast cancer. Individualization of treatment is essential.

Estetrol, a Fetal Selective Estrogen Receptor Modulator, Acts on the Vagina of Mice through Nuclear Estrogen Receptor α Activation

The genitourinary syndrome of menopause has a negative impact on quality of life of postmenopausal women. The treatment of vulvovaginal atrophy includes administration of estrogens. However, oral estrogen treatment is controversial because of its potential risks on venous thrombosis and breast cancer. Estetrol (E4) is a natural estrogen synthesized exclusively during pregnancy by the human fetal liver and initially considered as a weak estrogen. However, E4 was recently evaluated in phase 1 to 2 clinical studies and found to act as an oral contraceptive in combination with a progestin, without increasing the level of coagulation factors. We recently showed that E4 stimulates uterine epithelial proliferation through nuclear estrogen receptor (ER) α, but failed to elicit endothelial responses. Herein, we first evaluated the morphological and functional impacts of E4 on the vagina of ovariectomized mice, and we determined the molecular mechanism mediating these effects. Vaginal epithelial proliferation and lubrication after stimulation were found to increase after E4 chronic treatment. Using a combination of pharmacological and genetic approaches, we demonstrated that these E4 effects on the vagina are mediated by nuclear ERα activation. Altogether, we demonstrate that the selective activation of nuclear ERα is both necessary and sufficient to elicit functional and structural effects on the vagina, and therefore E4 appears promising as a therapeutic option to improve vulvovaginal atrophy.

Accurate Control of 17β-Estradiol Long-Term Release Increases Reliability and Reproducibility of Preclinical Animal Studies

Estrogens are the subject of intensive researches aiming to elucidate their mechanism of action on the various tissues they target and especially on mammary gland and breast cancer. The use of ready-to-use slow releasing devices to administer steroids, especially estrogens, to small experimental animals remains the method of choice in terms of animal well-being and of safety for both the researcher and the animal. In this study, we evaluated and compared, in vitro and in vivo, the release kinetic of estradiol (E2) over sixty days from two different slow-releasing systems: the matrix pellet (MP) and the reservoir implant (RI). We compared the impact of these systems in three E2-sensitive mouse models : mammary gland development, human MCF7 adenocarcinoma xenograft and mouse melanoma progression. The real amount of E2 that is released from both types of devices could differ from manufacturer specifications due to inadequate release for MP and initial burst effect for RI. Compared to MP, the interindividual variability was reduced with RI thanks to a superior control of the E2 release. Depending on the dose-dependent sensitivity of the physiological or pathological readout studied, this could lead to an improvement of the statistical power of in vivo experiments and thus to a reduction of the required animal number. Altogether, our data draw attention on the importance to adequately select the slow-releasing device that is the most appropriated to a specific experiment to better fulfill the 3Rs rule (Replacement, Reduction, Refinement) related to animal welfare and protection.

Regulatory effects of estetrol on the endothelial plasminogen pathway and endothelial cell migration

BACKGROUND

Estetrol (E4) is a natural estrogen produced solely during human pregnancy. E4 is suitable for clinical use since it acts as a selective estrogen receptor modulator. In clinical trials E4 has been seen to have little or no effect on coagulation. Hence, it is interesting to investigate whether E4 alters endothelial-dependent fibrinolysis.

OBJECTIVES

We studied the effects of E4 on the fibrinolytic system and whether this could influence the ability of endothelial cells to migrate. In addition, we compared the effects of E4 with those of 17β-estradiol (E2).

STUDY DESIGN

Human umbilical vein endothelial cells (HUVEC) were obtained from healthy women. Expression of plasminogen-activator inhibitor-1 (PAI-1), urokinase-type plasminogen activator (u-PA) and tissue plasminogen activator (t-PA) proteins was evaluated by Western blot analysis. Endothelial cell migration was studied by razor-scrape horizontal and multiwell insert systems assays.

RESULTS

E4 increased the expression of t-PA, u-PA and PAI-1 in HUVEC, but less so than did equimolar amounts of E2. The effects of E4 on t-PA, u-PA and PAI-1 were mediated by the induction of the early-immediate genes c-Jun and c-Fos. E4 in combination with E2 antagonized the effects induced by pregnancy-like E2 concentrations but did not impair the effects of postmenopausal-like E2 levels. We also found that the increased synthesis of PAI-1, u-PA and t-PA induced by E2 and E4 is important for horizontal and three-dimensional migration of HUVEC.

CONCLUSIONS

These results support the hypothesis that E4 acts as an endogenous selective estrogen receptor modulator (SERM), controlling the fibrinolytic system and endothelial cell migration.

Clinical effects of the fetal estrogen estetrol in a multiple-rising-dose study in postmenopausal women

OBJECTIVE

Estetrol (E4) is a natural fetal estrogen. The safety of increasing doses of E4 and its preliminary effects on the vagina, endometrium and menopausal vasomotor symptoms were investigated.

STUDY DESIGN

This was a partly randomized, open-label, multiple-rising-dose study in 49 postmenopausal women. Subjects with an intact uterus were randomized to receive either 2mg E4 or 2mg estradiol-valerate (E2V) for 28days. Subsequent dose-escalation groups (non-randomized) were: 10mg E4 (intact uterus and ≥35 hot flushes/week); and 20mg and 40mg E4 (hysterectomized subjects).

MAIN OUTCOME MEASURE

Adverse events (AEs) and vaginal cytology were evaluated in all treatment groups; hot flushes/sweating and endometrial proliferation were analyzed with 2 and 10mg E4 and 2mg E2V.

RESULTS

Estetrol appeared to be safe, without serious drug-related AEs. In all the groups there was a clear shift from parabasal to superficial vaginal cells, indicating an estrogenic effect and a potential for the treatment of vulvovaginal atrophy. The endometrial thickness remained stable in the 2mg E4 group and increased with E2V and 10mg E4. A decrease in the mean number of hot flushes and sweating was seen with 2 and 10mg E4 and 2mg E2V.

CONCLUSIONS

Estetrol in a dose range of 2-40mg per day improved vaginal cytology and vasomotor symptoms in postmenopausal women. Endometrial proliferation occurred with the 10mg dose. Estetrol seems a safe and suitable candidate to develop further for hormone therapy.

Estetrol Modulates Endothelial Nitric Oxide Synthesis in Human Endothelial Cells

Estetrol (E4) is a natural human estrogen that is present at high concentrations during pregnancy. E4 has been reported to act as an endogenous estrogen receptor modulator, exerting estrogenic actions on the endometrium or the central nervous system but presenting antagonistic effects on the breast. Due to these characteristics, E4 is currently being developed for a number of clinical applications, including contraception and menopausal hormone therapy. Endothelial nitric oxide (NO) is a key player for vascular function and disease during pregnancy and throughout aging in women. Endothelial NO is an established target of estrogens that enhance its formation in human endothelial cells. We here addressed the effects of E4 on the activity and expression of the endothelial nitric oxide synthase (eNOS) in cultured human umbilical vein endothelial cells (HUVEC). E4 stimulated the activation of eNOS and NO secretion in HUVEC. E4 was significantly less effective compared to E2, and a peculiar concentration-dependent effect was found, with higher amounts of E4 being less effective than lower concentrations. When E2 was combined with E4, an interesting pattern was noted. E4 antagonized NO synthesis induced by pregnancy-like E2 concentrations. However, E4 did not impede the modest induction of NO synthesis associated with postmenopausal-like E2 levels. These results support the hypothesis that E4 may be a regulator of NO synthesis in endothelial cells and raise questions on its peculiar signaling in this context. Our results may be useful to interpret the role of E4 during human pregnancy and possibly to help develop this interesting steroid for clinical use.