Tamoxifen is a widely used anti‑estrogen drug in the endocrine therapy of breast cancer (BC). It blocks estrogen signaling by competitively binding to estrogen receptor α (ERα), thereby inhibiting the growth of BC cells. However, with the long‑term application of tamoxifen, a subset of patients with BC have shown resistance to tamoxifen, which leads to low overall survival and progression‑free survival. The molecular mechanism of resistance is mainly due to downregulation of ERα expression and abnormal activation of the PI3K/AKT/mTOR signaling pathway. Moreover, the downregulation of targeted gene expression mediated by DNA methylation is an important regulatory mode to control protein expression. In the present review, methylation and tamoxifen are briefly introduced, followed by a focus on the effect of methylation on tamoxifen resistance and sensitivity. Finally, the clinical application of methylation for tamoxifen is described, including its use as a prognostic indicator. Finally, it is hypothesized that when methylation is used in combination with tamoxifen, it could recover the resistance of tamoxifen.

BACKGROUND: Estrogen receptors express in nearly 70% of breast cancers (ER-positive). Estrogen receptor alpha plays a fundamental role as a significant factor in breast cancer progression for the early selection of therapeutic approaches. Accordingly, there has been a surge of attention to non-invasive techniques, including circulating Cell-free DNA (ccfDNA) or Cell-Free DNA (cfDNA), to detect and track ESR1 genotype. Therefore, this study aimed to examine the diagnosis accuracy of ESR1 mutation detection by cell-free DNA in breast cancer patientsthrough a systematic review and comprehensive meta-analysis.
METHODS: PubMed, Embase, and Web of Science databases were searched up to 6 April 2022. Diagnostic studies on ESR1 measurement by cfDNA, which was confirmed using the tumour tissue biopsy, have been included in the study. The sensitivity, specificity, accuracy, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR) and negative likelihood ratio (NLR) were considered to analyse the data.
RESULTS: Out of 649 papers, 13 papers with 15 cohorts, including 389 participants, entered the meta-analyses. The comprehensive meta-analysis indicated a high sensitivity (75.52, 95% CI 60.19-90.85), specificity (88.20, 95% CI 80.99-95.40), and high accuracy of 88.96 (95% CI 83.23-94.69) for plasma ESR1. We also found a moderate PPV of 56.94 (95% CI 41.70-72.18) but a high NPV of 88.53 (95% CI 82.61-94.44). We also found an NLR of 0.443 (95% CI 0.09-0.79) and PLR of 1.60 (95% CI 1.20-1.99).
CONCLUSIONS: This systematic review and comprehensive meta-analysis reveal that plasma cfDNA testing exhibits high sensitivity and specificity in detecting ESR1 mutations in breast cancer patients. This suggests that the test could be a valuable diagnostic tool. It may serve as a dependable and non-invasive technique for identifying ESR1 mutations in breast cancer patients. However, more extensive research is needed to confirm its prognostic value.

In this narrative review, we attempt to provide an overview of the evidence regarding the role of estrogen (receptors) in cutaneous melanoma (CM). We reviewed 68 studies and 4 systematic reviews and meta-analyses published from 2002 up to and including 2022. The prevailing presence of estrogen receptor β (ERβ) instead of estrogen receptor α (ERα) in CM is notable, with ERβ potentially playing a protective role and being less frequently detected in progressive cases. While men with CM generally experience a less favorable prognosis, this distinction may become negligible with advancing age. The role of oral contraceptives (OC) and hormone replacement therapy (HRT) in CM remains controversial. However, recent studies tend to associate the use of these exogenous hormones with a heightened risk of CM, mostly only when using estrogen therapy and not in combination with progesterone. On the contrary, the majority of studies find no substantial influence of in vitro fertilization (IVF) treatment on CM risk. Reproductive factors, including younger age at first childbirth, higher parity, and shorter reproductive life, show conflicting evidence, with some studies suggesting a lower CM risk. We suggest an important role for estrogens in CM. More research is needed, but the integration of estrogens and targeting the estrogen receptors in melanoma therapy holds promise for future developments in the field.

OBJECTIVE: Estrogen and progesterone play key roles in the maintenance of pregnancy, and their function is mediated via estrogen receptor 1 (ESR1)/estrogen receptor 2 (ESR2) and progesterone receptor (PGR), respectively. It has been suggested the genetic variations in ESR1, ESR2, and PGR may contribute to recurrent pregnancy loss (RPL); however, the available evidence remains controversial. This meta-analysis aimed to explore the relation of various polymorphisms in ESR1, ESR2, and PGR genes to the risk of RPL.
METHODS: A systematic literature search was conducted using PubMed and Scopus up to August 2023 to obtain relevant studies. The odds ratios (ORs) with 95% confidence intervals (95% CIs) were computed and pooled with the use of random-effects models to test the associations.
RESULTS: A total of 31 studies with 12 different polymorphisms, including 5 polymorphisms for ESR1, 3 polymorphisms for ESR2, and 4 polymorphisms for PGR, were analyzed in this meta-analysis. Overall, no significant relationship was found between various polymorphisms of ESR1 and ESR2 with RPL in any of the genetic analysis models. PGR rs590688 (C > G) polymorphism was significantly related to the elevated risk of RPL under the dominant (OR = 1.67; 95 %CI: 1.15-2.44), allelic (OR = 1.55; 95 %CI: 1.13-2.12), and GC vs. CC (OR = 1.55; 95 %CI: 1.07-2.23) models. No significant association was identified for other variants of PGR gene.
CONCLUSIONS: Unlike estrogen receptors, variations in PGR rs590688 (C > G) may be linked to the increased risk of RPL. More studies are required to confirm this finding.

Estrogen receptors (ERs) are transcription factors with two subtypes: estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), which are essential for the maintenance of human health and play a regulatory role in common diseases such as breast cancer, osteoporosis, neurodegenerative disorders, liver injuries and lung cancers. A number of phytochemicals extracted from various fruits and vegetables have been demonstrated to exhibit estrogenic effects and are termed phytoestrogens. As modulators of ERs, phytoestrogens can be involved in the prevention and treatment of multiple diseases as complementary or alternative therapeutic agents and have a variety of health benefits for humans. This article reviews the health benefits of phytoestrogens in clinical and epidemiologic studies for several diseases and also provides a detailed description of the molecular mechanisms of their action. A brief comparison of the advantages and disadvantages of natural phytochemicals compared to synthetic drugs is also presented. The role of phytoestrogens in the treatment of diseases and human health requires further research to fully realize their therapeutic potential.

Estrogen receptor 1 (ESR1) XbaI polymorphisms may affect breast cancer susceptibility; however, the results of previously published studies are inconsistent. This meta-analysis aimed to investigate the relationship between ESR1 XbaI polymorphism and breast cancer risk.  Methods: Articles from the PubMed, Embase, Cochrane Library, WoS, Scopus, Wanfang Data, CNKI, CBM and CQVIP databases were systematically searched to determine the association between ESR1 XbaI polymorphism and breast cancer risk. The pooled results were assessed using odds ratios (ORs) and 95% confidence intervals (CIs), followed by subgroup analysis.  Results: Twenty-two studies involving 12,821 cases and 14,739 control subjects were analyzed. The pooled results indicated that ESR1 XbaI polymorphism may decrease risk of breast cancer in AG vs. AA (co-dominant model: OR = 0.88, 95% CI = 0.79-0.97, P = 0.015) and AG + GG vs. AA models (dominant model: OR = 0.89, 95% CI = 0.80-0.98, P = 0.022). Subgroup analysis indicated significant associations between the ESR1 XbaI polymorphism and breast cancer risk were observed in Asian subjects, non-Hardy-Weinberg equilibrium study, post-menopausal status and hospital-based subgroups under the AG vs. AA and AG + GG vs. AA models (all P < 0.05).  Conclusions: Our analysis of pooled data indicated that AG genotype in ESR1 XbaI may be a protective factor for breast cancer patients in some subgroups.

Estrogen receptor‑associated receptor α (ERRα) is an orphan nuclear receptor that lacks corresponding ligands. ERRα recruits co‑regulators to regulate gene transcription and plays an important role in human physiological functions. Peroxisome proliferator‑activated receptor γ (PPARγ) is also a nuclear receptor that regulates the expression of target genes via a ligand‑dependent mechanism, thereby participating in a series of physiological processes. Both ERRα and PPARγ are involved in the process of energy metabolism and tumorigenesis. In the present review, a concise overview of the important roles governed by ERRα and PPARγ in metabolism and their association with various disease are provided.

Estrogen (17β-estradiol or E2) is a crucial regulator of the synthesis and secretion of pituitary reproductive hormones luteinizing hormone, follicle-stimulating hormone, and prolactin. In this review, we summarize the role of estrogen receptors in nonfunctioning pituitary neuroendocrine tumors (NF-Pitnets), focusing on immunoexpression and gonadotroph cell proliferation and apoptosis. Gonadotroph tumors are the most common subtype of NF-Pitnets. Two major estrogen receptor (ER) isoforms expressed in the pituitary are estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ). Overall, estrogen actions are mostly exerted through the ERα isoform on the pituitary. The G protein-coupled estrogen receptor (GPER) located at the plasma membrane may contribute to nongenomic effects of estrogen. Nuclear immunoreactivity for ERα and ERβ was highest among gonadotroph and null cell tumors. Silent corticotroph tumors are the least immunoreactive for both receptors. A significantly elevated ERα expression was observed in macroadenomas compared with microadenomas. ERα and ERβ may act in opposite directions to regulate the Slug-E-cadherin pathway and to affect invasiveness of NF-Pitnets. In the cellular pathway, ERs regulate estrogen-induced proliferation and differentiation and impact several signaling pathways including the MAPK and PI3K/Akt pathway. Estrogen was the first-discovered inducer of pituitary tumor transforming gene 1 that was abundantly expressed in NF-Pitnets. ERα can be a potential biomarker for predicting tumor size and invasiveness as well as therapeutic target for NF-Pitnets. Selective estrogen receptor modulators or antiestrogen may represent as an alternative choice for the treatment of NF-Pitnets.

OBJECTIVE: Approximately 70% of patients with metastatic breast cancer (MBC) are hormone receptor (HR)-positive. Recent studies have shown that CDK4/6 inhibitors (CDKI) improve survival in combination with ET in HR-positive, HER2-negative MBC. The risk of venous thromboembolism (VTE) is 3-4 times higher in patients with breast cancer (BC) than in patients without cancer. The risk is even higher in BC patients receiving ET and chemotherapy. The aim of the study was to determine the VTE risk of CDKIs plus ET versus ET alone in patients with HR-positive, HER2-negative MBC.
METHODS: We performed a systematic review and meta-analysis to demonstrate the risk of VTE in patients with HR-positive HER2-negative MBC treated with combined CDKIs and ET versus ET alone.
RESULTS: Eight randomized controlled trials (RCT) with a total of 4,557 patients were eligible. The study arms comprised of palbociclib or ribociclib or abemaciclib plus ET while the control arms utilized placebo plus ET. The VTE events were 56 (2%) in the CDKIs plus ET group compared to 10 (0.5%) in the control group. Pooled relative risk (RR) for VTE was 2.62 (95% CI 1.21-5.65; P = 0.01) and the risk difference (RD) was 0.01 (95% CI 0.00-0.03; P = 0.02). Over a median follow-up of up to 36 months, RR was 3.18 (95% CI 1.22-8.24; P = 0.02) and RD was 0.03 (95% CI 0.01-0.06, P = 0.008).
CONCLUSIONS: Our meta-analyses demonstrated that the addition of CDKIs to ET in patients with HR-positive HER 2-negative MBC contribute to a higher incidence of VTE. Further trials are required to define the actual relation and definitive incidence of VTE with different CDKIs.

In patients with hormone receptor-positive breast cancer, differentiating between patients with a low and a high risk of recurrence is an ongoing challenge. In current practice, prognostic clinical parameters are used for risk prediction. DNA methylation markers have been proven to be of additional prognostic value in several cancer types. Numerous prognostic DNA methylation markers for breast cancer have been published in the literature. However, to date, none of these markers are used in clinical practice.
We conducted a systematic review of PubMed and EMBASE to assess the number and level of evidence of published DNA methylation markers for hormone receptor-positive breast cancer. To obtain an overview of the reporting quality of the included studies, all were scored according to the REMARK criteria that were established as reporting guidelines for prognostic biomarker studies.
A total of 74 studies were identified reporting on 87 different DNA methylation markers. Assessment of the REMARK criteria showed variation in reporting quality of the studies. Eighteen single markers and one marker panel were studied in multiple independent populations. Hypermethylation of the markers RASSF1, BRCA, PITX2, CDH1, RARB, PCDH10 and PGR, and the marker panel GSTP1, RASSF1 and RARB showed a statistically significant correlation with poor disease outcome that was confirmed in at least one other, independent study.
This systematic review provides an overview on published prognostic DNA methylation markers for hormone receptor-positive breast cancer and identifies eight markers that have been independently validated. Analysis of the reporting quality of included studies suggests that future research on this topic would benefit from standardised reporting guidelines.