Pyrosequencing quantified methylation level of BRCA1 promoter as prognostic factor for survival in breast cancer patient

The Tumor Suppressor BRCA1/2, Cancer Susceptibility and Genome Instability in Gynecological and Mammary Cancers

BRCA1 and BRCA2 germline alterations highly predispose women to breast and ovarian cancers. They are mostly found within the TNBC (Triple-Negative Breast Cancer) and the HGSOC (High-Grade Serous Ovarian Carcinoma) subsets, known by an aggressive phenotype, the lack of therapeutic targets and poor prognosis. Importantly, there is an increased risk for cervical cancer in BRCA1 and BRCA2 mutation carriers that raises questions about the link between the HPV-driven genome instability and BRCA1 and BRCA2 germline mutations. Clinical, preclinical, and in vitro studies explained the increased risk for breast and ovarian cancers by genome instability resulting from the lack or loss of many functions related to BRCA1 or BRCA2 proteins such as DNA damage repair, stalled forks and R-loops resolution, transcription regulation, cell cycle control, and oxidative stress. In this review, we decipher the relationship between BRCA1/2 alterations and genomic instability leading to gynecomammary cancers through results from patients, mice, and cell lines. Understanding the early events of BRCA1/2-driven genomic instability in gynecomammary cancers would help to find new biomarkers for early diagnosis, improve the sensitivity of emerging therapies such as PARP inhibitors, and reveal new potential therapeutic targets.

The Clinical and Pathological Profile of BRCA1 Gene Methylated Breast Cancer Women: A Meta-Analysis

BACKGROUND

DNA aberrant hypermethylation is the major cause of transcriptional silencing of the breast cancer gene 1 (BRCA1) gene in sporadic breast cancer patients. The aim of the present meta-analysis was to analyze all available studies reporting clinical characteristics of BRCA1 gene hypermethylated breast cancer in women, and to pool the results to provide a unique clinical profile of this cancer population.

METHODS

On September 2020, a systematic literature search was performed. Data were retrieved from PubMed, MEDLINE, and Scopus by searching the terms: "BRCA*" AND "methyl*" AND "breast". All studies evaluating the association between BRCA1 methylation status and breast cancer patients' clinicopathological features were considered for inclusion.

RESULTS

465 studies were retrieved. Thirty (6.4%) studies including 3985 patients met all selection criteria. The pooled analysis data revealed a significant correlation between BRCA1 gene hypermethylation and advanced breast cancer disease stage (OR = 0.75: 95% CI: 0.58-0.97; p = 0.03, fixed effects model), lymph nodes involvement (OR = 1.22: 95% CI: 1.01-1.48; p = 0.04, fixed effects model), and pre-menopausal status (OR = 1.34: 95% CI: 1.08-1.66; p = 0.008, fixed effects model). No association could be found between BRCA1 hypermethylation and tumor histology (OR = 0.78: 95% CI: 0.59-1.03; p = 0.08, fixed effects model), tumor grading (OR = 0.78: 95% CI :0.46-1.32; p = 0.36, fixed effects model), and breast cancer molecular classification (OR = 1.59: 95% CI: 0.68-3.72; p = 0.29, random effects model).

CONCLUSIONS

hypermethylation of the BRCA1 gene significantly correlates with advanced breast cancer disease, lymph nodes involvement, and pre-menopausal cancer onset.

BRCA1 Promoter Hypermethylation is Associated with Good Prognosis and Chemosensitivity in Triple-Negative Breast Cancer

The aberrant hypermethylation of BRCA1 promoter CpG islands induces the decreased expression of BRCA1 (Breast Cancer 1) protein. It can be detected in sporadic breast cancer without BRCA1 pathogenic variants, particularly in triple-negative breast cancers (TNBC). We investigated BRCA1 hypermethylation status (by methylation-specific polymerase chain reaction (MS-PCR) and MassARRAY^® assays), and BRCA1 protein expression using immunohistochemistry (IHC), and their clinicopathological significance in 248 chemotherapy-naïve TNBC samples. Fifty-five tumors (22%) exhibited BRCA1 promoter hypermethylation, with a high concordance rate between MS-PCR and MassARRAY^® results. Promoter hypermethylation was associated with reduced IHC BRCA1 protein expression (p = 0.005), and expression of Programmed death-ligand 1 protein (PD-L1) by tumor and immune cells (p = 0.03 and 0.011, respectively). A trend was found between promoter hypermethylation and basal marker staining (p = 0.058), and between BRCA1 expression and a basal-like phenotype. In multivariate analysis, relapse-free survival was significantly associated with N stage, adjuvant chemotherapy, and histological subtype. Overall survival was significantly associated with T and N stage, histology, and adjuvant chemotherapy. In addition, patients with tumors harboring BRCA1 promoter hypermethylation derived the most benefit from adjuvant chemotherapy. In conclusion, BRCA1 promoter hypermethylation is associated with TNBC sensitivity to adjuvant chemotherapy, basal-like features and PD-L1 expression. BRCA1 IHC expression is not a good surrogate marker for promoter hypermethylation and is not independently associated with prognosis. Association between promoter hypermethylation and sensitivity to Poly(ADP-ribose) polymerase PARP inhibitors needs to be evaluated in a specific series of patients.

Epigenetic modulation of BRCA-1 and MGMT genes, and histones H4 and H3 are associated with breast tumors

Aberrant patterns in promoter methylation of tumor-suppressor genes and posttranslational modifications of histone proteins are considered as major features of malignancy. In this study, we aimed to investigate promoter methylation of three tumor-suppressor genes (BRCA-1, MGMT, and P16) and three histone marks (H3K9ac, H3K18ac, and H4K20me3) in patients with breast tumors. This case-control study included 27 patients with malignant breast tumors (MBT) and 31 patients with benign breast tumors (BBT). The methylation-specific PCR was used for determining promoter methylation of BRCA-1, MGMT, and P16 genes. Western blot analysis was performed to detect histone lysine acetylation (H3K9ac and H3K18ac) and lysine methylation (H4K20me3). BRCA-1 promoter methylation was detected in 44.4% of the MBT whereas this alteration was found in 9.7% of BBT (P = 0.005). The Kaplan-Meier analysis indicated that hypermethylation in BRCA-1 promoter was significantly associated with poor overall survival of patients with breast cancer (P = 0.039). MGMT promoter methylation was identified in 18.5% of MBT and 0.0% of the BBT (P = 0.01). The frequency of P16 promoter methylation was 25.8% in BBT and 11.1% in MBT (P = 0.12). As compared with BBT, MBT samples displayed the aberrant patterns of histones marks with hypomethylation of H4K20 and hypoacetylation of H3K18 (P = 0.03 and P = 0.04, respectively). There was a negative significant correlation between H3K9ac levels and tumor size in MBT group (r = -0.672; P = 0.008). The present findings suggest that promoter hypermethylation of MGMT and BRCA-1 genes along with alterations in H3K18ac and H4K20me3 levels may have prognostic values in patients with breast cancer. Moreover, the detection of these epigenetic modifications in breast tumors could be helpful in finding new methods for breast cancer therapy.

Methylation Analysis Using Microarrays: Analysis and Interpretation

This chapter discusses analysis and interpretation of large-scale Illumina DNA methylation microarray data, used in the context of cancer studies. We outline commonly used normalization procedures and list issues to consider regarding data preprocessing. Focusing on software packages for R, we describe methods for finding features in the methylation data that are of importance for generating and testing hypotheses in cancer research, like differentially methylated positions or regions and global methylation trends.

Association of BRCA1 Promoter Methylation with Breast Cancer in Asia: A Meta- Analysis

Objective:

The aim of this study was to determine the degree of association of BRCA1 promoter methylation with breast cancer in Asia.

Methods:

The study sample for the present meta-analysis was provided by published research articles on associations of BRCA1 promoter methylation with breast cancer in Asia accessed through databases on PubMed, ProQuest and EBSCO published between 1997 and November 2017. Pooled odds ratios (OR) were calculated with fixed and random-effect models. Data were processed using Review Manager 5.3 (RevMan 5.3).

Results:

Of a total of 475 articles, 11 studies were included in our systematic review with meta-analysis of relevant data. The results showed a highly significant association between BRCA1 promoter methylation with breast cancer in Asia (OR = 8.78 [95% CI 4.15-18.56, p < 0.00001]).

Conclusion:

This analysis confirmed association between BRCA1 promoter methylation and breast cancer in Asia. BRCA1 promoter assessment might be a predictive or diagnostic aid for breast cancer prediction.

The synthetic antihyperlipidemic drug potassium piperate selectively kills breast cancer cells through inhibiting G1-S-phase transition and inducing apoptosis

Piper longum L. is a well-known traditional antihyperlipidemic medicine in China, containing medicinal constituents of piperine, pipernonaline and piperlonguminine in its fruit. However, the antitumor properties of these constituents have not yet been studied. We found that potassium piperate (GBK), a derivative of piperine, inhibited proliferation of cancer cells. GBK selectively inhibited the G1-S-phase transition in breast cancer cells and the G1 arrest was correlated with induction of p27 expression, which is an inhibitor for cyclin-dependent kinases, and inhibition of cyclin A, cyclin E and cyclin B expression. Moreover, GBK treatment led to a downregulation of the mini-chromosome maintenance protein expression and induction of mitochondrial-dependent cell apoptosis in breast cancer cells. Our results also suggested that GBK might also inhibit cancer cell proliferation through epigenetic signaling pathways. A synergistic effect in inhibition of cancer cell proliferation was found when GBK was combined with chemotherapy medicines etoposide phosphate or cisplatin at middle or low doses in vitro. These results show that GBK is a novel potential anti-breast cancer drug that inhibits cell proliferation and promotes cell apoptosis.

Epigenetics of breast cancer: Biology and clinical implication in the era of precision medicine

In the last years, mortality from breast cancer has declined in western countries as a consequence of a more widespread screening resulting in earlier detection, as well as an improved molecular classification and advances in adjuvant treatment. Nevertheless, approximately one third of breast cancer patients will develop distant metastases and eventually die for the disease. There is now a compelling body of evidence suggesting that epigenetic modifications comprising DNA methylation and chromatin remodeling play a pivotal role since the early stages of breast cancerogenesis. In addition, recently, increasing emphasis is being placed on the property of ncRNAs to finely control gene expression at multiple levels by interacting with a wide array of molecules such that they might be designated as epigenetic modifiers. In this review, we summarize the current knowledge about the involvement of epigenetic modifications in breast cancer, and provide an overview of the significant association of epigenetic traits with the breast cancer clinicopathological features, emphasizing the potentiality of epigenetic marks to become biomarkers in the context of precision medicine.

Epigenetic regulation of DNA repair genes and implications for tumor therapy

DNA repair represents the first barrier against genotoxic stress causing metabolic changes, inflammation and cancer. Besides its role in preventing cancer, DNA repair needs also to be considered during cancer treatment with radiation and DNA damaging drugs as it impacts therapy outcome. The DNA repair capacity is mainly governed by the expression level of repair genes. Alterations in the expression of repair genes can occur due to mutations in their coding or promoter region, changes in the expression of transcription factors activating or repressing these genes, and/or epigenetic factors changing histone modifications and CpG promoter methylation or demethylation levels. In this review we provide an overview on the epigenetic regulation of DNA repair genes. We summarize the mechanisms underlying CpG methylation and demethylation, with de novo methyltransferases and DNA repair involved in gain and loss of CpG methylation, respectively. We discuss the role of components of the DNA damage response, p53, PARP-1 and GADD45a on the regulation of the DNA (cytosine-5)-methyltransferase DNMT1, the key enzyme responsible for gene silencing. We stress the relevance of epigenetic silencing of DNA repair genes for tumor formation and tumor therapy. A paradigmatic example is provided by the DNA repair protein O⁶-methylguanine-DNA methyltransferase (MGMT), which is silenced in up to 40% of various cancers through CpG promoter methylation. The CpG methylation status of the MGMT promoter strongly correlates with clinical outcome and, therefore, is used as prognostic marker during glioblastoma therapy. Mismatch repair genes are also subject of epigenetic silencing, which was shown to correlate with colorectal cancer formation. For many other repair genes shown to be epigenetically regulated the clinical outcome is not yet clear. We also address the question of whether genotoxic stress itself can lead to epigenetic alterations of genes encoding proteins involved in the defense against genotoxic stress.

BRCA1 protein expression and subcellular localization in primary breast cancer: Automated digital microscopy analysis of tissue microarrays

Purpose

Mutations in BRCA1 are associated with familial as well as sporadic aggressive subtypes of breast cancer, but less is known about whether BRCA1 expression or subcellular localization contributes to progression in population-based settings.

Methods

We examined BRCA1 expression and subcellular localization in invasive breast cancer tissues from an ethnically diverse sample of 286 patients and 36 normal breast tissue controls. Two different methods were used to label breast cancer tissues for BRCA1: (1) Dual immunofluoresent staining with BRCA1 and cytokeratin 8/18 and (2) immunohistochemical staining using the previously validated MS110 mouse monoclonal antibody. Slides were visualized and quantified using the VECTRA Automated Multispectral Image Analysis System and InForm software.

Results

BRCA1 staining was more intense in normal than in invasive breast tissue for both cytoplasmic (p<0.0001) and nuclear (p<0.01) compartments. BRCA1 nuclear to cytoplasmic ratio was higher in breast cancer cells than in normal mammary epithelial cells. Reduced BRCA1 expression was associated with high tumor grade and negative hormone receptors (estrogen receptor, progesterone receptor and Her2). On the other hand, high BRCA1 expression correlated with basal-like tumors (high CK5/6 and EGFR), and high nuclear androgen receptor staining. Lower nuclear to cytoplasmic ratio of BRCA1 correlated significantly with high Ki67 labeling index (p< 0.05) and family history of breast cancer (p = 0.001).

Conclusion

Findings of this study indicate that alterations in BRCA1 protein expression and subcellular localization in breast cancer correlate with poor prognostic markers and aggressive tumor features. Further large-scale studies are required to assess the potential relevance of BRCA1 protein expression and localization in routine classification of breast cancer.

Pyrosequencing quantified methylation level of miR-124 predicts shorter survival for patients with myelodysplastic syndrome

Background

Aberrant CpG island methylation has been increasingly recognized as a common event in myelodysplastic syndrome (MDS). To date, most of the previous studies of miR-124 in MDS have focused on epigenetic changes and little is known about the underlying mechanism through which miR-124 regulates CDK6 expression.

Results

In the present study, we employed pyrosequencing analysis to quantify the methylation levels of upstream regions of the miR-124 genes (miR-124-1, miR-124-2 and miR-124-3) in 56 primary MDS patients. We found the three miR-124 genes were methylated in MDS patients. Univariate analysis revealed that the World Health Organization (WHO) classification, marrow blast count, karyotype, International Prognostic Scoring System (IPSS), mean corpuscular volume, as well as high methylation of miR-124-1, miR-124-2 and miR-124-3 were significantly related to overall survival. In leukaemia-free survival, patients who were older and had an advanced WHO classification, high marrow blast counts, high IPSS risk and high methylation of miR-124-1 and miR-124-2 progressed rapidly to acute myeloid leukaemia. Multivariate analysis demonstrated that high methylation of miR-124-3 was an independent factor of overall survival. Median survival of patients with high miR-124-3 methylation was significantly shorter (7.6 months) than patients with low methylation (32.7 months; P = 0.010). A functional study revealed that silencing of miR-124 resulted in upregulation of its target gene, cyclin dependent kinase CDK6, which in turn promoted cell proliferation in the MDS cell line SKM-1.

Conclusions

High methylation of miR-124-3 predicts shorter survival for patients with MDS, which may be a useful prognostic marker in MDS.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-017-0388-5) contains supplementary material, which is available to authorized users.

Levels of DNA Methylation Vary at CpG Sites across the BRCA1 Promoter, and Differ According to Triple Negative and "BRCA-Like" Status, in Both Blood and Tumour DNA

Triple negative breast cancer is typically an aggressive and difficult to treat subtype. It is often associated with loss of function of the BRCA1 gene, either through mutation, loss of heterozygosity or methylation. This study aimed to measure methylation of the BRCA1 gene promoter at individual CpG sites in blood, tumour and normal breast tissue, to assess whether levels were correlated between different tissues, and with triple negative receptor status, histopathological scoring for BRCA-like features and BRCA1 protein expression. Blood DNA methylation levels were significantly correlated with tumour methylation at 9 of 11 CpG sites examined (p<0.0007). The levels of tumour DNA methylation were significantly higher in triple negative tumours, and in tumours with high BRCA-like histopathological scores (10 of 11 CpG sites; p<0.01 and p<0.007 respectively). Similar results were observed in blood DNA (6 of 11 CpG sites; p<0.03 and 7 of 11 CpG sites; p<0.02 respectively). This study provides insight into the pattern of CpG methylation across the BRCA1 promoter, and supports previous studies suggesting that tumours with BRCA1 promoter methylation have similar features to those with BRCA1 mutations, and therefore may be suitable for the same targeted therapies.