Methylation of ESR1 promoter induced by SNAI2-DNMT3B complex promotes epithelial-mesenchymal transition and correlates with poor prognosis in ERα-positive breast cancers

Estrogen receptor α (ERα) serves as an essential therapeutic predictor for breast cancer (BC) patients and is regulated by epigenetic modification. Abnormal methylation of cytosine phosphoric acid guanine islands in the estrogen receptor 1 (ESR1) gene promoter could silence or decrease ERα expression. In ERα-negative BC, we previously found snail family transcriptional repressor 2 (SNAI2), a zinc-finger transcriptional factor, recruited lysine-specific demethylase 1 to the promoter to transcriptionally suppress ERα expression by demethylating histone H3 lysine 4 dimethylation (H3K4me2). However, the role of SNAI2 in ERα-positive BC remains elusive. In this study, we observed a positive correlation between SNAI2 and ESR1 methylation, and SNAI2 promoted ESR1 methylation by recruiting DNA methyltransferase 3 beta (DNMT3B) rather than DNA methyltransferase 1 (DNMT1) in ERα-positive BC cells. Subsequent enrichment analysis illustrated that ESR1 methylation is strongly correlated with cell adhesion and junction. Knocking down DNMT3B could partially reverse SNAI2 overexpression-induced cell proliferation, migration, and invasion. Moreover, high DNMT3B expression predicted poor relapse-free survival and overall survival in ERα-positive BC patients. In conclusion, this study demonstrated the novel mechanisms of the ESR1 methylation mediated with the SNAI2/DNMT3B complex and enhanced awareness of ESR1 methylation's role in promoting epithelial-mesenchymal transition in BC.

ESR1 Methylation Measured in Cell-Free DNA to Evaluate Endocrine Resistance in Metastatic Breast Cancer Patients

ESR1 methylation was proposed as mechanism for endocrine resistance in metastatic breast cancer patients. To evaluate its potential as a minimally invasive biomarker, we investigated the feasibility of measuring ESR1 methylation in cell-free DNA (cfDNA) and its association with endocrine resistance. First, we provided evidence that demethylation in vitro restores ER expression. Subsequently, we found that ESR1 methylation in cfDNA was not enriched in endocrine-resistant versus endocrine-sensitive patients. Interestingly, we found a correlation between ESR1 methylation and age. Publicly available data confirm an age-related increase in ESR1 methylation in leukocytes, confounding the determination of the ESR1 methylation status of tumors using cfDNA.

The high methylation level of a novel 151-bp CpG island in the ESR1 gene promoter is associated with a poor breast cancer prognosis

BACKGROUND

The ESR1 gene suffers methylation changes in many types of cancers, including breast cancer (BC), the most frequently diagnosed cancer in women that is also present in men. Methylation at promoter A of ESR1 is the worse prognosis in terms of overall survival; thus, the early detection, prognostic, and prediction of therapy involve some methylation biomarkers.

METHODS

Therefore, our study aimed to examine the methylation levels at the ESR1 gene in samples from Mexican BC patients and its possible association with menopausal status.

RESULTS

We identified a novel 151-bp CpG island in the promoter A of the ESR1 gene. Interestingly, methylation levels at this CpG island in positive ERα tumors were approximately 50% less than negative ERα or control samples. Furthermore, methylation levels at ESR1 were associated with menopausal status. In postmenopausal patients, the methylation levels were 1.5-fold higher than in premenopausal patients. Finally, according to tumor malignancy, triple-negative cancer subtypes had higher ESR1 methylation levels than luminal/HER2+ or luminal A subtypes.

CONCLUSIONS

Our findings suggest that methylation at this novel CpG island might be a promising prognosis marker.

A Comprehensive Molecular Analysis of in Vivo Isolated EpCAM-Positive Circulating Tumor Cells in Breast Cancer

BACKGROUND

Circulating tumor cell (CTC) analysis is highly promising for liquid biopsy-based molecular diagnostics. We undertook a comprehensive molecular analysis of in vivo isolated CTCs in breast cancer (BrCa).

METHODS

In vivo isolated CTCs from 42 patients with early and 23 patients with metastatic breast cancer (MBC) were prospectively collected and analyzed for gene expression, DNA mutations, and DNA methylation before and after treatment. 19 healthy donor (HD) samples were analyzed as a control group. In identical blood draws, CTCs were enumerated using CellSearch® and characterized by direct IF staining.

RESULTS

All 19 HD samples were negative for CK8, CK18, CK19, ERBB2, TWIST1, VEGF, ESR1, PR, and EGFR expression, while CD44, CD24, ALDH1, VIM, and CDH2 expression was normalized to B2M (reference gene). At least one gene was expressed in 23/42 (54.8%) and 8/13 (61.5%) CTCs in early BrCa before and after therapy, and in 20/23 (87.0%) and 5/7 (71.4%) MBC before and after the first cycle of therapy. PIK3CA mutations were detected in 11/42 (26.2%) and 3/13 (23.1%) in vivo isolated CTCs in early BrCa before and after therapy, and in 11/23 (47.8%) and 2/7 (28.6%) MBC, respectively. ESR1 methylation was detected in 5/32 (15.7%) and 1/10 (10.0%) CTCs in early BrCa before and after therapy, and in 3/15(20.0%) MBC before the first line of therapy. The comprehensive molecular analysis of CTC revealed a higher sensitivity in relation to CellSearch or IF staining when based on creatine kinase selection.

CONCLUSIONS

In vivo-CTC isolation in combination with a comprehensive molecular analysis at the gene expression, DNA mutation, and DNA methylation level comprises a highly powerful approach for molecular diagnostic applications using CTCs.