Methylation is less abundant in BRCA1-associated compared with sporadic breast cancer

The Tumour Microenvironment and Epigenetic Regulation in BRCA1 Pathogenic Variant-Associated Breast Cancers

Background/Objectives: BRCA1 pathogenic variant (PV)-associated breast cancers are most commonly seen in hereditary genetic conditions such as the autosomal-dominant Hereditary Breast and Ovarian Cancer (HBOC) syndrome, and rarely in sporadic breast cancer. Such breast cancers tend to exhibit greater aggressiveness and poorer prognoses due to the influence of BRCA1 pathogenic variants (PVs) on the tumour microenvironment. Additionally, while the genetic basis of BRCA1 PV breast cancer is well-studied, the role of epigenetic mediators in the tumourigenesis of these hereditary breast cancers is also worth exploring. Results: PVs in the BRCA1 gene interact with stromal cells and immune cells, promoting epithelial-mesenchymal transition, angiogenesis, and affecting oestrogen levels. Additionally, BRCA1 PVs contribute to breast cancer development through epigenetic effects on cells, including DNA methylation and histone acetylation, leading to the suppression of proto-oncogenes and dysregulation of cytokines. In terms of epigenetics, lysine-specific demethylase 1 (LSD-1) is considered a master epigenetic regulator, governing both transcriptional repression and activation. It exerts epigenetic control over BRCA1 and, to a lesser extent, BRCA2 genes. The upregulation of LSD-1 is generally associated with a poorer prognosis in cancer patients. In the context of breast cancer in BRCA1/2 PV carriers, LSD-1 contributes to tumour development through various mechanisms. These include the maintenance of a hypoxic environment and direct suppression of BRCA1 gene expression. Conclusions: While LSD-1 itself does not directly cause mutations in BRCA1 or BRCA2 genes, its epigenetic influence sheds light on the potential role of LSD-1 inhibitors as a therapeutic approach in managing breast cancer, particularly in individuals with BRCA1/2 PVs. Targeting LSD-1 may help counteract its detrimental effects and provide a promising avenue for therapy in this specific subgroup of breast cancer.

Differential methylation of circulating free DNA assessed through cfMeDiP as a new tool for breast cancer diagnosis and detection of BRCA1/2 mutation

BACKGROUND

Recent studies have highlighted the importance of the cell-free DNA (cfDNA) methylation profile in detecting breast cancer (BC) and its different subtypes. We investigated whether plasma cfDNA methylation, using cell-free Methylated DNA Immunoprecipitation and High-Throughput Sequencing (cfMeDIP-seq), may be informative in characterizing breast cancer in patients with BRCA1/2 germline mutations for early cancer detection and response to therapy.

METHODS

We enrolled 23 BC patients with germline mutation of BRCA1 and BRCA2 genes, 19 healthy controls without BRCA1/2 mutation, and two healthy individuals who carried BRCA1/2 mutations. Blood samples were collected for all study subjects at the diagnosis, and plasma was isolated by centrifugation. Cell-free DNA was extracted from 1 mL of plasma, and cfMeDIP-seq was performed for each sample. Shallow whole genome sequencing was performed on the immuno-precipitated samples. Then, the differentially methylated 300-bp regions (DMRs) between 25 BRCA germline mutation carriers and 19 non-carriers were identified. DMRs were compared with tumor-specific regions from public datasets to perform an unbiased analysis. Finally, two statistical classifiers were trained based on the GLMnet and random forest model to evaluate if the identified DMRs could discriminate BRCA-positive from healthy samples.

RESULTS

We identified 7,095 hypermethylated and 212 hypomethylated regions in 25 BRCA germline mutation carriers compared to 19 controls. These regions discriminate tumors from healthy samples with high accuracy and sensitivity. We show that the circulating tumor DNA of BRCA1/2 mutant breast cancers is characterized by the hypomethylation of genes involved in DNA repair and cell cycle. We uncovered the TFs associated with these DRMs and identified that proteins of the Erythroblast Transformation Specific (ETS) family are particularly active in the hypermethylated regions. Finally, we assessed that these regions could discriminate between BRCA positives from healthy samples with an AUC of 0.95, a sensitivity of 88%, and a specificity of 94.74%.

CONCLUSIONS

Our study emphasizes the importance of tumor cell-derived DNA methylation in BC, reporting a different methylation profile between patients carrying mutations in BRCA1, BRCA2, and wild-type controls. Our minimally invasive approach could allow early cancer diagnosis, assessment of minimal residual disease, and monitoring of response to therapy.

Harnessing Epigenetics for Breast Cancer Therapy: The Role of DNA Methylation, Histone Modifications, and MicroRNA

Breast cancer exhibits various epigenetic abnormalities that regulate gene expression and contribute to tumor characteristics. Epigenetic alterations play a significant role in cancer development and progression, and epigenetic-targeting drugs such as DNA methyltransferase inhibitors, histone-modifying enzymes, and mRNA regulators (such as miRNA mimics and antagomiRs) can reverse these alterations. Therefore, these epigenetic-targeting drugs are promising candidates for cancer treatment. However, there is currently no effective epi-drug monotherapy for breast cancer. Combining epigenetic drugs with conventional therapies has yielded positive outcomes and may be a promising strategy for breast cancer therapy. DNA methyltransferase inhibitors, such as azacitidine, and histone deacetylase inhibitors, such as vorinostat, have been used in combination with chemotherapy to treat breast cancer. miRNA regulators, such as miRNA mimics and antagomiRs, can alter the expression of specific genes involved in cancer development. miRNA mimics, such as miR-34, have been used to inhibit tumor growth, while antagomiRs, such as anti-miR-10b, have been used to inhibit metastasis. The development of epi-drugs that target specific epigenetic changes may lead to more effective monotherapy options in the future.

Evaluating DNA Methylation in Random Fine Needle Aspirates from the Breast to Inform Cancer Risk

Introduction

Critical regulatory genes are functionally silenced by DNA hypermethylation in breast cancer and premalignant lesions. The objective of this study was to examine whether DNA methylation assessed in random fine needle aspirates (rFNA) can be used to inform breast cancer risk.

Methods

In 20 women with invasive breast cancer scheduled for surgery at Johns Hopkins Hospital, cumulative methylation status was assessed in a comprehensive manner. rFNA was performed on tumors, adjacent normal tissues, and all remaining quadrants. Pathology review was conducted on blocks from all excised tissue. The cumulative methylation index (CMI) for 12 genes was assessed by a highly sensitive QM-MSP assay in 280 aspirates and tissue from 11 incidental premalignant lesions. Mann-Whitney and Kruskal Wallis tests were used to compare median CMI by patient, location, and tumor characteristics.

Results

The median age of participants was 49 years (interquartile range [IQR]: 44-58). DNA methylation was detectable at high levels in all tumor aspirates (median CMI = 252, IQR: 75-111). Methylation was zero or low in aspirates from adjacent tissue (median CMI = 11, IQR: 0-13), and other quadrants (median CMI = 2, IQR: 1-5). Nineteen incidental lesions were identified in 13 women (4 malignant and 15 premalignant). Median CMI levels were not significantly different in aspirates from quadrants (p = 0.43) or adjacent tissue (p = 0.93) in which 11 methylated incidental lesions were identified.

Conclusions

The diagnostic accuracy of methylation based on rFNA alone to detect premalignant lesions or at-risk quadrants is poor and therefore should not be used to evaluate cancer risk. A more targeted approach needs to be evaluated.

G-Quadruplex Matters in Tissue-Specific Tumorigenesis by BRCA1 Deficiency

How and why distinct genetic alterations, such as BRCA1 mutation, promote tumorigenesis in certain tissues, but not others, remain an important issue in cancer research. The underlying mechanisms may reveal tissue-specific therapeutic vulnerabilities. Although the roles of BRCA1, such as DNA damage repair and stalled fork stabilization, obviously contribute to tumor suppression, these ubiquitously important functions cannot explain tissue-specific tumorigenesis by BRCA1 mutations. Recent advances in our understanding of the cancer genome and fundamental cellular processes on DNA, such as transcription and DNA replication, have provided new insights regarding BRCA1-associated tumorigenesis, suggesting that G-quadruplex (G4) plays a critical role. In this review, we summarize the importance of G4 structures in mutagenesis of the cancer genome and cell type-specific gene regulation, and discuss a recently revealed molecular mechanism of G4/base excision repair (BER)-mediated transcriptional activation. The latter adequately explains the correlation between the accumulation of unresolved transcriptional regulatory G4s and multi-level genomic alterations observed in BRCA1-associated tumors. In summary, tissue-specific tumorigenesis by BRCA1 deficiency can be explained by cell type-specific levels of transcriptional regulatory G4s and the role of BRCA1 in resolving it. This mechanism would provide an integrated understanding of the initiation and development of BRCA1-associated tumors.

A Novel Gene Prognostic Signature Based on Differential DNA Methylation in Breast Cancer

Background: DNA methylation played essential roles in regulating gene expression. The impact of DNA methylation status on the occurrence and development of cancers has been well demonstrated. However, little is known about its prognostic role in breast cancer (BC).

Materials: The Illumina Human Methylation450 array (450k array) data of BC was downloaded from the UCSC xena database. Transcriptomic data of BC was downloaded from the Cancer Genome Atlas (TCGA) database. Firstly, we used univariate and multivariate Cox regression analysis to screen out independent prognostic CpGs, and then we identified methylation-associated prognosis subgroups by consensus clustering. Next, a methylation prognostic model was developed using multivariate Cox analysis and was validated with the Illumina Human Methylation27 array (27k array) dataset of BC. We then screened out differentially expressed genes (DEGs) between methylation high-risk and low-risk groups and constructed a methylation-based gene prognostic signature. Further, we validated the gene signature with three subgroups of the TCGA-BRCA dataset and an external dataset GSE146558 from the Gene Expression Omnibus (GEO) database.

Results: We established a methylation prognostic signature and a methylation-based gene prognostic signature, and there was a close positive correlation between them. The gene prognostic signature involved six genes: IRF2, KCNJ11, ZDHHC9, LRP11, PCMT1, and TMEM70. We verified their expression in mRNA and protein levels in BC. Both methylation and methylation-based gene prognostic signatures showed good prognostic stratification ability. The AUC values of 3-years, 5-years overall survival (OS) were 0.737, 0.744 in the methylation signature and 0.725, 0.715 in the gene signature, respectively. In the validation groups, high-risk patients were confirmed to have poorer OS. The AUC values of 3 years were 0.757, 0.735, 0.733 in the three subgroups of TCGA dataset and 0.635 in GSE146558 dataset.

Conclusion: This study revealed the DNA methylation landscape and established promising methylation and methylation-based gene prognostic signatures that could serve as potential prognostic biomarkers and therapeutic targets.

Automated and rapid detection of cancer in suspicious axillary lymph nodes in patients with breast cancer

Preoperative staging of suspicious axillary lymph nodes (ALNs) allows patients to be triaged to ALN dissection or to sentinel lymph node biopsy (SLNB). Ultrasound-guided fine needle aspiration (FNA) and cytology of ALN is moderately sensitive but its clinical utility relies heavily on the cytologist's experience. We proposed that the 5-h automated GeneXpert system-based prototype breast cancer detection assay (BCDA) that quantitatively measures DNA methylation in ten tumor-specific gene markers could provide a facile, accurate test for detecting cancer in FNA of enlarged lymph nodes. We validated the assay in ALN-FNA samples from a prospective study of patients (N = 230) undergoing SLNB. In a blinded analysis of 218 evaluable LN-FNAs from 108 malignant and 110 benign LNs by histology, BCDA displayed a sensitivity of 90.7% and specificity of 99.1%, achieving an area under the ROC curve, AUC of 0.958 (95% CI: 0.928-0.989; P < 0.0001). Next, we conducted a study of archival FNAs of ipsilateral palpable LNs (malignant, N = 72, benign, N = 53 by cytology) collected in the outpatient setting prior to neoadjuvant chemotherapy (NAC). Using the ROC-threshold determined in the prospective study, compared to cytology, BCDA achieved a sensitivity of 94.4% and a specificity of 92.5% with a ROC-AUC = 0.977 (95% CI: 0.953-1.000; P < 0.0001). Our study shows that the automated assay detects cancer in suspicious lymph nodes with a high level of accuracy within 5 h. This cancer detection assay, scalable for analysis to scores of LN FNAs, could assist in determining eligibility of patients to different treatment regimens.

Estrogen receptor α is involved in the regulation of ITGA8 methylation in estrogen receptor-positive breast cancer

Background

Integrin subunit α 8 (ITGA8) methylation has been associated with the development of several cancers, but its contribution to breast cancer remains unclear. The present study aimed to investigate the methylation status of ITGA8, and the underlying regulatory mechanisms of ITGA8 methylation in breast cancer.

Methods

ITGA8 expression was investigated using the Gene Expression Profiling Interactive Analysis 2 (GEPIA2) database and the Breast Cancer Gene-Expression Miner v.4.4 (bc-GenExMiner v4.4). The association between ITGA8 expression levels and the survival rate of breast cancer patients was evaluated using The Cancer Genome Atlas (TCGA) database and Gene Expression-based Outcome for Breast Cancer Online (GOBO): Gene Set Analysis. Methylation-specific PCR (MSP) was used to detect the methylation of ITGA8. Protein level of ITGA8 was determined by Western blot analysis.

Results

ITGA8 was expressed at low levels in human breast cancer cells compared to non-tumorigenic breast cells and breast tissue, and was upregulated in estrogen receptor (ER)-positive tissue compared with ER-negative tissue (P<0.01). ITGA8 gene expression was negatively associated with breast tumor stage and survival rate in all breast cancer patients. However, ER-positive patients with low ITGA8 expression showed poorer distant metastasis-free survival (DMFS) and recurrence-free survival (RFS) rates than patients with high ITGA8 expression. This was not observed in the ER-negative population. Mechanistically speaking, hypermethylation of ITGA8 was discovered in ER-positive breast cancer cells. Administration of the methylation inhibitor, 5-aza-2’-deoxycytidine (5-aza-dC), significantly elevated protein expression of ITGA8 in ER-positive breast cancer cells compared to ER-negative cells. The positive association between ITGA8 status and methylation was also observed in clinical tissue specimens. When treated with 17-beta-estradiol, an antagonist of ERα, 5-aza-dC-induced upregulation of ITGA8 in ER-positive breast cancer cells was no longer observed.

Conclusions

Low ITGA8 expression in ER-positive breast cancer might be caused by the hypermethylation of ITGA8, a process dependent on ERα. Our findings provide an important foundation for investigations into ITGA8-targeted treatment strategies for ER-positive breast cancer.

BRCA1-Dependent Transcriptional Regulation: Implication in Tissue-Specific Tumor Suppression

Germ-line mutations in breast cancer susceptibility gene 1 (BRCA1) predominantly predispose women to breast and ovarian cancers. BRCA1 is best known for its functions in maintenance of genomic integrity including repairing DNA double-strand breaks through homologous recombination and suppressing DNA replication stress. However, whether these universally important BRCA1 functions in maintenance of genomic stability are sufficient to account for its tissue-specific tumor-suppressing function remains unclear. Accumulating evidence indicates that there are previously underappreciated roles of BRCA1 in transcriptional regulation and chromatin remodeling. In this review, we discuss the functional significance of interactions between BRCA1 and various transcription factors, its role in epigenetic regulation and chromatin dynamics, and BRCA1-dependent crosstalk between the machineries of transcription and genome integrity. Furthermore, we propose a model of how transcriptional regulation could contribute to tissue-dependent tumor-suppressing function of BRCA1.

DNA methylation profiling in MEN1-related pancreatic neuroendocrine tumors reveals a potential epigenetic target for treatment

OBJECTIVE

Epigenetic changes contribute to pancreatic neuroendocrine tumor (PanNET) development. Hypermethylation of promoter DNA as a cause of tumor suppressor gene silencing is a well-established oncogenic mechanism that is potentially reversible and therefore an interesting therapeutic target. Multiple endocrine neoplasia type 1 (MEN1) is the most frequent cause of inherited PanNETs. The aim of this study was to determine promoter methylation profiles in MEN1-related PanNETs.

DESIGN AND METHODS

Methylation-specific multiplex ligation-dependent probe amplification was used to assess promoter methylation of 56 tumor suppressor genes in MEN1-related (n = 61) and sporadic (n = 34) PanNETs. Differences in cumulative methylation index (CMI), individual methylation percentages and frequency of promoter hypermethylation between subgroups were analyzed.

RESULTS

We found promoter methylation of a large number of potential tumor suppressor genes. CMI (median CMI: 912 vs 876, P = 0.207) was the same in MEN1-related and sporadic PanNETs. We found higher methylation percentages of CASP8 in MEN1-related PanNETs (median: 59% vs 16.5%, P = 0.002). In MEN1-related non-functioning PanNETs, the CMI was higher in larger PanNETs (>2 cm) (median: 969.5 vs 838.5; P = 0.021) and in PanNETs with liver metastases (median: 1036 vs 869; P = 0.013). Hypermethylation of MGMT2 was more frequent in non-functioning PanNETs compared to insulinomas (median: 44.7% vs 8.3%; P = 0.022). Hypermethylation of the Von Hippel-Lindau gene promoter was observed in one MEN1-related PanNET and was associated with loss of protein expression.

CONCLUSION

Promoter hypermethylation is a frequent event in MEN1-related and sporadic PanNETs. Targeting DNA methylation could be of therapeutic value in MEN1 patients with advanced PanNETs.

Quantitation of DNA Methylation by Quantitative Multiplex Methylation-Specific PCR (QM-MSP) Assay

The defining feature of the Quantitative Multiplex Methylation-Specific PCR (QM-MSP) method to sensitively quantify DNA methylation is the two-step PCR approach for a multiplexed analysis of a panel of up to 12 genes in clinical samples with minimal quantities of DNA. In the first step, for up to 12 genes tested, one pair of gene-specific primers (forward and reverse) amplifies the methylated and unmethylated copies of the same gene simultaneously and in multiplex, in one PCR reaction. This methylation-independent amplification step produces amplicons of up to 10⁹ copies per μL after 36 cycles of PCR. In the second step, the amplicons of the first reaction (STEP 1) are quantified with a standard curve using real-time PCR and two independent fluorophores to detect methylated/unmethylated DNA of each gene in the same well (e.g., 6FAM and VIC). One methylated copy is detectable in 100,000 reference gene copies. Methylation is reported on a continuous scale. For the gene panel, the highest level of normal DNA methylation above which a sample would be called positive is derived by using Receiver Operating Characteristic (ROC), maximizing assay specificity and sensitivity to distinguish between normal/benign versus tumor DNA. QM-MSP can be applied to clinical samples of fresh or fixed ductal cells, ductal fluid, nipple fluid, fine needle aspirates, core biopsies, and tumor tissue sections.

The clinical value of aberrant epigenetic changes of DNA damage repair genes in human cancer

The stability and integrity of the human genome are maintained by the DNA damage repair (DDR) system. Unrepaired DNA damage is a major source of potentially mutagenic lesions that drive carcinogenesis. In addition to gene mutation, DNA methylation occurs more frequently in DDR genes in human cancer. Thus, DNA methylation may play more important roles in DNA damage repair genes to drive carcinogenesis. Aberrant methylation patterns in DNA damage repair genes may serve as predictive, diagnostic, prognostic and chemosensitive markers of human cancer. MGMT methylation is a marker for poor prognosis in human glioma, while, MGMT methylation is a sensitive marker of glioma cells to alkylating agents. Aberrant epigenetic changes in DNA damage repair genes may serve as therapeutic targets. Treatment of MLH1-methylated colon cancer cell lines with the demethylating agent 5′-aza-2′-deoxycytidine induces the expression of MLH1 and sensitizes cancer cells to 5-fluorouracil. Synthetic lethality is a more exciting approach in patients with DDR defects. PARP inhibitors are the most effective anticancer reagents in BRCA-deficient cancer cells.

DNA promoter hypermethylation in nipple fluid: a potential tool for early breast cancer detection

Introduction

Nipple fluid aspiration provides direct non-invasive sampling of fluid from the mammary ductal system, where the majority of breast cancers originate. DNA promoter hypermethylation (“methylation”) occurs early and at high frequency in breast carcinogenesis, bearing the potential as a biomarker for cancer detection at its earliest stages. We assessed methylation in nipple fluid from breasts of healthy women, of women with sporadic breast cancer and of their contralateral breasts. Our goal was to investigate whether nipple fluid can be used as a reliable methylation biomarker source.

Methods

Methylation levels of 13 genes were analysed by quantitative multiplex-methylation specific PCR (QM-MSP) in nipple fluid samples from breasts of healthy women, and from the affected and contralateral breasts of breast cancer patients.

Results

Methylation analysis of the low-volume nipple fluid samples was feasible. Despite the generally low methylation levels, cancerous and healthy breasts nipple fluid could be discriminated with an area under the receiver operating characteristic curve (AUC) of 0.64 (p<0.01) based on a multivariate model including AKR1B1, ALX1, RASSF1A and TM6SF1. Within-patient differences between cancerous and contralateral nipple fluid samples were less prominent.

Conclusions

Cancerous nipple fluid contains increased levels of methylation of tumor suppressor genes that potentially could serve as a biomarker for early breast cancer detection.

Molecular profile of nasopharyngeal carcinoma: analysing tumour suppressor gene promoter hypermethylation by multiplex ligation-dependent probe amplification

Aims

To assess differences in methylation profiles, and thus pathogenesis, between Epstein-Barr virus (EBV)-positive and negative nasopharyngeal carcinomas (NPCs). Also, promoter hypermethylation is a common phenomenon in early carcinogenesis to inactivate tumour suppressor genes. Since epigenetic changes are reversible, the therapeutic application of methylation inhibitors could provide treatment options.

Methods

We evaluated promoter hypermethylation profiles of 22 common tumour suppressor genes in 108 NPCs using methylation-specific multiplex ligation-dependent probe amplification. Correlation between methylation, clinicopathological features (including EBV) and survival was examined. Cluster analysis was also performed.

Results

Hypermethylation of RASSF1A and ESR1 was significantly more frequent in EBV-positive NPC, while hypermethylation of DAPK1 was more frequent in EBV-negative NPC. In logistic regression, age, with EBV-positive NPC occurring at earlier age, and RASSF1, with RASSF1 hypermethylation being more frequent in EBV-positive NPC, remained significant. In EBV-positive NPC, hypermethylation of RASSF1A predicted worse overall survival (OS) (HR 3.058,95% CI 1.027 to 9.107). In EBV-negative NPC, hypermethylated adenomatous polyposis coli (APC) was a predictor of poor disease-free survival (DFS) (HR 6.868, 95% CI 2.142 to 22.022).

Conclusion

There are important epigenetic differences between EBV-negative and EBV-positive NPCs, with EBV-negative NPC having a more similar hypermethylation profile to other head and neck squamous cell carcinomas than EBV-positive NPC. Hypermethylation of RASSF1A might contribute to worse OS in EBV-positive NPC, and may be an important event in the pathogenesis of EBV-infected NPC. Hypermethylation of APC might contribute to worse DFS in EBV-negative NPC.

Hypermethylation of CDKN2A exon 2 in tumor, tumor-adjacent and tumor-distant tissues from breast cancer patients

BACKGROUND

Breast carcinogenesis is a multistep process involving genetic and epigenetic changes. Tumor tissues are frequently characterized by gene-specific hypermethylation and global DNA hypomethylation. Aberrant DNA methylation levels have, however, not only been found in tumors, but also in tumor-surrounding tissue appearing histologically normal. This phenomenon is called field cancerization. Knowledge of the existence of a cancer field and its spread are of clinical relevance. If the tissue showing pre-neoplastic lesions is not removed by surgery, it may develop into invasive carcinoma.

METHODS

We investigated the prevalence of gene-specific and global DNA methylation changes in tumor-adjacent and tumor-distant tissues in comparison to tumor tissues from the same breast cancer patients (n = 18) and normal breast tissues from healthy women (n = 4). Methylation-sensitive high resolution melting (MS-HRM) analysis was applied to determine methylation levels in the promoters of APC, BRCA1, CDKN2A (p16), ESR1, HER2/neu and PTEN, in CDKN2A exon 2 and in LINE-1, as indicator for the global DNA methylation extent. The methylation status of the ESR2 promoter was determined by pyrosequencing.

RESULTS

Tumor-adjacent and tumor-distant tissues frequently showed pre-neoplastic gene-specific and global DNA methylation changes. The APC promoter (p = 0.003) and exon 2 of CDKN2A (p < 0.001) were significantly higher methylated in tumors than in normal breast tissues from healthy women. For both regions, significant differences were also found between tumor and tumor-adjacent tissues (p = 0.001 and p < 0.001, respectively) and tumor and tumor-distant tissues (p = 0.001 and p < 0.001, respectively) from breast cancer patients. In addition, tumor-adjacent (p = 0.002) and tumor-distant tissues (p = 0.005) showed significantly higher methylation levels of CDKN2A exon 2 than normal breast tissues serving as control. Significant correlations were found between the proliferative activity and the methylation status of CDKN2A exon 2 in tumor (r = -0.485, p = 0.041) and tumor-distant tissues (r = -0.498, p = 0.036).

CONCLUSIONS

From our results we can conclude that methylation changes in CDKN2A exon 2 are associated with breast carcinogenesis. Further investigations are, however, necessary to confirm that hypermethylation of CDKN2A exon 2 is associated with tumor proliferative activity.

The relationship of single-strand breaks in DNA to breast cancer risk and to tissue concentrations of oestrogens

CONTEXT

Clinical study of breast cancer patients in Chicago, IL, USA.

OBJECTIVE

Ascertain the utility of measurements of single-strand breaks (SSB) in DNA for assessment of breast cancer risk.

METHODS

Fine-needle aspirates of the breast, SSB by nick translation, percent breast density (PBD), Gail model risk, cumulative methylation index (CMI), enzymes of DNA repair and tissue antioxidants.

RESULTS

DNA repair enzymes and 4-hydroxyestradiol were negatively associated with SSB; CMI and PBD were positively associated.

CONCLUSIONS

Quantitative measurement of SSBs by this procedure indicates the relative number of SSBs and is related to promoter methylation, antioxidant availability and percent breast density.

DNA Methylation in Breast Tumor from High-risk Women in the Breast Cancer Family Registry

To examine DNA methylation profiles in breast tumors of women with a strong breast cancer family history, we measured methylation by bisulfite sequencing in 40 genes in 40 breast tumor tissues from women in the Breast Cancer Family Registry. We selected candidate genes from analysis of the Cancer Genome Atlas project (TCGA) breast data. Compared to TCGA breast cancer, BCFR cases are younger and more likely to be ER-negative. Overall, we found that many of the methylation differences between BCFR tumor and normal adjacent tissues were smaller than that in TCGA samples. We found only 32% of tested genes were hypermethylated in BCFR; the largest difference was 36.1% for SEPW1, and the smallest difference was 10% for RYR2. These data suggest the importance of examining breast cancer cases including familial cases enriched with early-onset cancers to identify methylation markers that can be examined in blood as biomarkers for early detection.

Inheritance of deleterious mutations at both BRCA1 and BRCA2 in an international sample of 32,295 women

BACKGROUND

Most BRCA1 or BRCA2 mutation carriers have inherited a single (heterozygous) mutation. Transheterozygotes (TH) who have inherited deleterious mutations in both BRCA1 and BRCA2 are rare, and the consequences of transheterozygosity are poorly understood.

METHODS

From 32,295 female BRCA1/2 mutation carriers, we identified 93 TH (0.3 %). "Cases" were defined as TH, and "controls" were single mutations at BRCA1 (SH1) or BRCA2 (SH2). Matched SH1 "controls" carried a BRCA1 mutation found in the TH "case". Matched SH2 "controls" carried a BRCA2 mutation found in the TH "case". After matching the TH carriers with SH1 or SH2, 91 TH were matched to 9316 SH1, and 89 TH were matched to 3370 SH2.

RESULTS

The majority of TH (45.2 %) involved the three common Jewish mutations. TH were more likely than SH1 and SH2 women to have been ever diagnosed with breast cancer (BC; p = 0.002). TH were more likely to be diagnosed with ovarian cancer (OC) than SH2 (p = 0.017), but not SH1. Age at BC diagnosis was the same in TH vs. SH1 (p = 0.231), but was on average 4.5 years younger in TH than in SH2 (p < 0.001). BC in TH was more likely to be estrogen receptor (ER) positive (p = 0.010) or progesterone receptor (PR) positive (p = 0.013) than in SH1, but less likely to be ER positive (p < 0.001) or PR positive (p = 0.012) than SH2. Among 15 tumors from TH patients, there was no clear pattern of loss of heterozygosity (LOH) for BRCA1 or BRCA2 in either BC or OC.

CONCLUSIONS

Our observations suggest that clinical TH phenotypes resemble SH1. However, TH breast tumor marker characteristics are phenotypically intermediate to SH1 and SH2.

Promoter Methylation Status of Breast Cancer Susceptibility Gene 1 and 17 Beta Hydroxysteroid Dehydrogenase Type 1 Gene in Sporadic Breast Cancer Patients

Epigenetic modifications are involved in breast carcinogenesis. Identifying genes that are epigenetically silenced via methylation could select target patients for diagnostic as well as therapeutic potential. We assessed promoter methylation of breast cancer susceptibility gene 1 (BRCA1) and 17 Beta Hydroxysteroid Dehydrogenase Type 1 (17βHSD-1) in normal and cancer breast tissues of forty sporadic breast cancer (BC) cases using restriction enzyme based methylation-specific PCR (REMS-PCR). In cancerous tissues, BRCA1 and 17βHSD-1 were methylated in 42.5% and 97.5%, respectively, while normal tissues had 35% and 95% methylation, respectively. BRCA1 methylation in normal tissues was 12.2-fold more likely to associate with methylation in cancer tissues (p < 0.001). It correlated significantly with increased age at menopause, mitosis, the negative status of Her2, and the molecular subtype "luminal A" (p = 0.048, p = 0.042, p = 0.007, and p = 0.049, resp.). Methylation of BRCA1 and 17βHSD-1 related to luminal A subtype of breast cancer. Since a small proportion of normal breast epithelial cells had BRCA1 methylation, our preliminary findings suggest that methylation of BRCA1 may be involved in breast tumors initiation and progression; therefore, it could be used as a biomarker for the early detection of sporadic breast cancer. Methylation of 17βHSD-1 in normal and cancer tissue could save patients the long term use of adjuvant antiestrogen therapies.

Incidence of BRCA1 somatic mutations and response to neoadjuvant chemotherapy in Chinese women with triple-negative breast cancer

BACKGROUND

The prevalence of BRCA1 somatic mutations status in triple-negative breast cancer (TNBC) has not been well documented. The aims of this study were to determine the frequency of BRCA1 somatic mutations and to investigate the association between BRCA1 deleterious somatic mutation status and response to neoadjuvant chemotherapy in women with TNBC.

METHODS

Two hundred and five TNBC patients without BRCA1 germline mutations were enrolled in this study. Fresh tumor tissues were available for this cohort of 205 patients, including 112 patients with fresh core needle biopsy tumor tissues before treatment and 93 patients with fresh tumor tissues procured after surgery. BRCA1 somatic mutations were determined in the tumor samples using PCR-direct sequencing assay. Among the 112 patients with core needle biopsy samples, 97 patients received neoadjuvant chemotherapy.

RESULTS

Eight patients (3.9%) carried a BRCA1 pathogenic somatic mutation in this cohort of 205 TNBC patients. These eight BRCA1 deleterious somatic mutations included five frameshift or nonsense mutations (c.191_212del22, c.1664delA, c.4674_4675+17del, c.3671_3672insTTCC, c.1162A>T), one splicing site mutation (c.134+2T>G) and two missense mutations (c.5511G>C and c.286G>A). No significant differences in tumor characteristics between BRCA1 deleterious somatic mutation carriers and non-carriers were observed. The pCR (pathologic complete response) rate was 32.0% in the 97 patients who received neoadjuvant chemotherapy. BRCA1 deleterious somatic mutation carriers (n=5) had a higher pCR rate than did non-carriers (n=92) (BRCA1 carriers vs non-carriers, 60.0% vs 30.4%, P=0.32), although it did not reach a significance due to a small sample size.

CONCLUSIONS

A small subset of TNBC patients carried a BRCA1 deleterious somatic mutation; BRCA1 somatic mutation carriers are likely to respond to neoadjuvant chemotherapy.

Assessing Heavy Metal and PCB Exposure from Tap Water by Measuring Levels in Plasma from Sporadic Breast Cancer Patients, a Pilot Study

Breast cancer (BrCA) is the most common cancer affecting women around the world. However, it does not arise from the same causative agent among all women. Genetic markers have been associated with heritable or familial breast cancers, which may or may not be confounded by environmental factors, whereas sporadic breast cancer cases are more likely attributable to environmental exposures. Approximately 85% of women diagnosed with BrCA have no family history of the disease. Given this overwhelming bias, more plausible etiologic mechanisms should be investigated to accurately assess a woman’s risk of acquiring breast cancer. It is known that breast cancer risk is highly influenced by exogenous environmental cues altering cancer genes either by genotoxic mechanisms (DNA mutations) or otherwise. Risk assessment should comprehensively incorporate exposures to exogenous factors that are linked to a woman’s individual susceptibility. However, the exact role that some environmental agents (EA) play in tumor formation and/or cancer gene regulation is unclear. In this pilot project, we begin a multi-disciplinary approach to investigate the intersection of environmental exposures, cancer gene response, and BrCA risk. Here, we present data that show environmental exposure to heavy metals and PCBs in drinking water, heavy metal presence in plasma of nine patients with sporadic BrCA, and Toxic Release Inventory and geological data for a metal of concern, uranium, in Northeast Georgia.

Methylation biomarkers for pleomorphic lobular breast cancer - a short report

Background

Pleomorphic invasive lobular cancer (pleomorphic ILC) is a rare variant of ILC that is characterized by a classic ILC-like growth pattern combined with an infiltrative ductal cancer (IDC)-like high nuclear atypicality. There is an ongoing discussion whether pleomorphic ILC is a dedifferentiated form of ILC or in origin an IDC with a secondary loss of cohesion. Since gene promoter hypermethylation is an early event in breast carcinogenesis and thus may provide information on tumor progression, we set out to compare the methylation patterns of pleomorphic ILC, classic ILC and IDC. In addition, we aimed at analyzing the methylation status of pleomorphic ILC.

Methods

We performed promoter methylation profiling of 24 established and putative tumor suppressor genes by methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) analysis in 20 classical ILC, 16 pleomorphic ILC and 20 IDC cases.

Results

We found that pleomorphic ILC showed relatively low TP73 and MLH1 methylation levels and relatively high RASSF1A methylation levels compared to classic ILC. Compared to IDC, pleomorphic ILC showed relatively low MLH1 and BRCA1 methylation levels. Hierarchical cluster analysis revealed a similar methylation pattern for pleomorphic ILC and IDC, while the methylation pattern of classic ILC was different.

Conclusion

This is the first report to identify TP73, RASSF1A, MLH1 and BRCA1 as possible biomarkers to distinguish pleomorphic ILC from classic ILC and IDC.

DNA methylation as a promising landscape: A simple blood test for breast cancer prediction

Breast cancer is the most common malignancy among women worldwide. Risk assessment is one of the main services delivered by cancer clinics. Biomarker analysis on different tissues including the peripheral blood can provide crucial information. One of the potential epigenetic biomarkers (epimarkers) is introduced as the peripheral blood DNA methylation pattern. This study was conducted to evaluate the potential value of peripheral blood epimarkers as an accessible tool to predict the risk of breast cancer development. WBC's DNA was the focus of several case-control studies at both genome wide and candidate gene levels to reveal epigenetic changes accounting for predisposition to breast cancer, leading to suggest that ATM, TITF1, SFRP1, NUP155, NEUROD1, ZNF217, DBC2, DOK7 and ESR1 genes and the LINE1, Alu and Sat2 DNA elements could be considered as the potential epimarkers. To address that by which mechanisms WBC's DNA methylation patterns could be linked to the propensity to breast cancer, several contemplations have been offered. Constitutional epimutation during embryonic life, and methylation changes secondary to either environmental exposures or tumor-mediated immune response, are the two main mechanisms. One can deduce that epimarkers based on their potential properties or regulatory impacts on cancer-related genes may be employed for risk prediction, prognosis, and survival inferences that are highly required for breast cancer management toward personalized medicine.

CXCL12 and ADAM23 hypermethylation are associated with advanced breast cancers

More than 25% of the patients with breast cancer (BC) develop metastatic disease. In the present study, we investigated the relationship between DNA methylation levels in genes regulating cell growth, invasiveness, and metastasis and advanced BCs and evaluated the clinical utility of methylation profiles for detecting metastatic potential. Pyrosequencing was used to quantify methylation levels in 11 cancer-associated genes in primary tumors (PTs), lymph node metastases (LNMs), plasma (PL), and blood cells from 206 patients with invasive BC. Protein expression was evaluated using immunohistochemistry. PTs showed hypermethylation of A isoform of the RAS-association domain family 1 (RASSF1A), adenomatous polyposis coli (APC), chemokine C-X-C motif ligand 12 (CXCL12), and disintegrin and metalloprotease domain 23 (ADAM23) (means 38.98%, 24.84%, 12.04%, and 10.01%, respectively). Positive correlations were identified between methylations in PTs and LNMs, but not between PL and PTs. The cumulative methylation of PTs and LNMs manifested similar spectrums of methylated genes that indicate the maintaining of aberrant methylation during breast tumorigenesis. Significantly increased methylation levels in RASSF1A, APC, CXCL12, and ADAM23 were found in estrogen receptor (ER) positive BCs in comparison with ER negative cases. Regarding these results, the evaluation of DNA methylation could be more informative in testing of patients with ER positive BC. The risk for LNMs development and higher proliferation of cancer cells measured through Ki-67 expression was increased by hypermethylation of CXCL12 and ADAM23, respectively. Therefore, the quantification of CXCL12 and ADAM23 methylation could be useful for the prediction of advanced stage of BC.

Promoter hypermethylation profiling of distant breast cancer metastases

Promoter hypermethylation of tumor suppressor genes seems to be an early event in breast carcinogenesis and is potentially reversible. This makes methylation a possible therapeutic target, a marker for treatment response and/or a prognostic factor. Methylation status of 40 tumor suppressor genes was compared between 53 primary breast tumors and their corresponding metastases to brain, lung, liver, or skin. In paired analyses, a significant decrease in methylation values was seen in distant metastases compared to their primaries in 21/40 individual tumor suppressor genes. Furthermore, primary tumors that metastasized to the liver clustered together, in line with the finding that primary breast carcinomas that metastasized to the brain, skin, or lung, showed higher methylation values in up to 27.5 % of tumor suppressor genes than primary carcinomas that metastasized to the liver. Conversion in methylation status of several genes from the primary tumor to the metastasis had prognostic value, and methylation status of some genes in the metastases predicted survival after onset of metastases. Methylation levels for most of the analyzed tumor suppressor genes were lower in distant metastases compared to their primaries, pointing to the dynamic aspect of methylation of these tumor suppressor genes during cancer progression. Also, specific distant metastatic sites seem to show differences in methylation patterns, implying that hypermethylation profiles of the primaries may steer site-specific metastatic spread. Lastly, methylation status of the metastases seems to have prognostic value. These promising findings warrant further validation in larger patient cohorts and more tumor suppressor genes.

Epigenetic changes in BRCA1-mutated familial breast cancer

Familial breast cancer occurs in about 10% of breast cancer cases. Germline mutation in BRCA1 is the most penetrant predisposition for the disease. Mutated BRCA1 leads to disease by causing genome instability via multiple mechanisms including epigenetic changes. This review summarizes recent progress in studying the correlation between BRCA1 predisposition and epigenetic alterations in BRCA1-type familial breast cancer.

Methylation profiling of ductal carcinoma in situ and its relationship to histopathological features

Introduction

DNA methylation is a well-studied biomarker in invasive breast cancer, but its role in ductal carcinoma in situ (DCIS) is less well characterized. The aims of this study are to assess the methylation profile in DCIS for a panel of well-characterized genes that are frequently methylated in breast cancer, to investigate the relationship of methylation with pathological features, and to perform a proof-of-principle study to evaluate the practicality of methylation as a biomarker in diagnostic DCIS material.

Methods

Promoter CpG island methylation for a panel of 11 breast cancer-related genes was performed by methylation-sensitive high resolution melting (MS-HRM). Formalin-fixed, paraffin-embedded (FFPE) biopsies from 72 samples of pure DCIS (DCIS occurring in the absence of synchronous invasive carcinoma), 10 samples of mixed DCIS (DCIS adjacent to invasive carcinoma), and 18 samples of normal breast epithelium adjacent to a DCIS lesion were micro-dissected prior to DNA extraction.

Results

Methylation was seen for all the tested genes except BRCA1. RASSF1A was the most frequently methylated gene (90% of DCIS samples) and its methylation was associated with comedo necrosis (p = 0.018). Cluster analysis based on the methylation profile revealed four groups, the highly methylated cluster being significantly associated with high nuclear grade, HER2 amplification, negative estrogen receptor (ER) α status, and negative progesterone receptor (PgR) status, (p = 0.038, p = 0.018, p <0.001, p = 0.001, respectively). Methylation of APC (p = 0.017), CDH13 (p = 0.017), and RARβ (p <0.001) was associated with negative ERα status. Methylation of CDH13 (p <0.001), and RARβ (p = 0.001) was associated with negative PgR status. Methylation of APC (p = 0.013) and CDH13 (p = 0.026) was associated with high nuclear grade. Methylation of CDH13 (p = 0.009), and RARβ (p = 0.042) was associated with HER2-amplification.

Conclusions

DNA methylation can be assessed in FFPE-derived samples using suitable methodologies. Methylation of a panel of genes that are known to be methylated in invasive breast cancer was able to classify DCIS into distinct groups and was differentially associated with phenotypic features in DCIS.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-014-0423-9) contains supplementary material, which is available to authorized users.

BRCA1 promoter methylation is a marker of better response to platinum-taxane-based therapy in sporadic epithelial ovarian cancer

BACKGROUND

The aim of the current study was to investigate the role of BRCA1 promoter methylation as predictive factor of response to platinum-taxane-based therapy in sporadic ovarian cancer.

PATIENTS AND METHODS

BRCA1 promoter methylation was analyzed in 42 sporadic epithelial ovarian cancers. The results were validated in a second cohort of 137 ovarian cancer patients.

RESULTS

BRCA1 promoter methylation was observed in 35.7 % of patients in the first group and in 33.6 % in the second group. BRCA1 promoter methylation was associated with significant increase in median progression-free survival (PFS) of ovarian cancer patients receiving adjuvant platinum-taxane-based chemotherapy (P = 0.008). Multivariate analysis revealed that BRCA1 promoter methylation remains a favorable factor in regard to PFS (HR 0.52; 95 % CI 0.32-0.85, P = 0.009) after adjustment for other prognostic factors. Under the patients with recurrent disease, BRCA1 promoter methylation was associated with significant longer median PFS of 18.5 months in comparison with 12.8 months PFS for patients without BRCA1 promoter methylation.

CONCLUSIONS

BRCA1 promoter methylation is predictive for better response to platinum-taxane-based therapy in EOC.

Validation of DNA promoter hypermethylation biomarkers in breast cancer--a short report

PURPOSE

DNA promoter hypermethylation of tumor suppressor genes is known to occur early in cancer development, including breast cancer. To improve early breast cancer detection, we aimed to investigate whether the identification of DNA promoter hypermethylation might be of added value.

METHODS

The methylation status of a panel of 19 candidate genes (AKR1B1, ALX1, ARHGEF7, FZD10, GHSR, GPX7, GREM1, GSTP1, HOXD1, KL, LHX2, MAL, MGMT, NDRG2, RASGRF2, SFRP1, SFRP2, TM6SF1 and TMEFF2) was determined in formalin-fixed paraffin-embedded normal breast and breast cancer tissue samples using gel-based methylation-specific PCR (MSP).

RESULTS

The promoters of the AKR1B1, ALX1, GHSR, GREM1, RASGRF2, SFRP2, TM6SF1 and TMEFF2 genes were found to be significantly differentially methylated in normal versus malignant breast tissues. Based on sensitivity, specificity and logistic regression analyses the best performing genes for detecting breast cancer were identified. Through multivariate analyses, we found that AKR1B1 and TM6SF1 could detect breast cancer with an area under the curve (AUC) of 0.986 in a receiver operating characteristic (ROC) assessment.

CONCLUSIONS

Based on our data, we conclude that AKR1B1 and TM6SF1 may serve as candidate methylation biomarkers for early breast cancer detection. Further studies are underway to evaluate the methylation status of these genes in body fluids, including nipple aspirates and blood.

Epigenetic epidemiology of cancer

Epigenetic epidemiology includes the study of variation in epigenetic traits and the risk of disease in populations. Its application to the field of cancer has provided insight into how lifestyle and environmental factors influence the epigenome and how epigenetic events may be involved in carcinogenesis. Furthermore, it has the potential to bring benefit to patients through the identification of diagnostic markers that enable the early detection of disease and prognostic markers that can inform upon appropriate treatment strategies. However, there are a number of challenges associated with the conduct of such studies, and with the identification of biomarkers that can be applied to the clinical setting. In this review, we delineate the challenges faced in the design of epigenetic epidemiology studies in cancer, including the suitability of blood as a surrogate tissue and the capture of genome-wide DNA methylation. We describe how epigenetic epidemiology has brought insight into risk factors associated with lung, breast, colorectal and bladder cancer and review relevant research. We discuss recent findings on the identification of epigenetic diagnostic and prognostic biomarkers for these cancers.

HPV-positive oropharyngeal squamous cell carcinoma is associated with TIMP3 and CADM1 promoter hypermethylation

Oropharyngeal squamous cell carcinoma (OPSCC) is associated with human papillomavirus (HPV) in a proportion of tumors. HPV-positive OPSCC is considered a distinct molecular entity with a prognostic advantage compared to HPV-negative cases. Silencing of cancer-related genes by DNA promoter hypermethylation may play an important role in the development of OPSCC. Hence, we examined promoter methylation status in 24 common tumor suppressor genes in a group of 200 OPSCCs to determine differentially methylated genes in HPV-positive versus HPV-negative primary OPSCC. Methylation status was correlated with HPV status, clinical features, and patient survival using multivariate methods. Additionally, methylation status of 16 cervical squamous cell carcinomas (SCC) was compared with HPV-positive OPSCC. Using methylation-specific probe amplification, HPV-positive OPSCC showed a significantly higher cumulative methylation index (CMI) compared to HPV-negative OPSCC (P=0.008). For the genes CDH13, DAPK1, and RARB, both HPV-positive and HPV-negative OPSCC showed promoter hypermethylation in at least 20% of the tumors. HPV status was found to be an independent predictor of promoter hypermethylation of CADM1 (P < 0.001), CHFR (P = 0.027), and TIMP3 (P < 0.001). CADM1 and CHFR showed similar methylation patterns in OPSCC and cervical SCC, but TIMP3 showed no methylation in cervical SCC in contrast to OPSCC. Methylation status of neither individual gene nor CMI was associated with survival. These results suggest that HPV-positive tumors are to a greater extent driven by promotor hypermethylation in these tumor suppressor genes. Especially CADM1 and TIMP3 are significantly more frequently hypermethylated in HPV-positive OPSCC and CHFR in HPV-negative tumors.

Differential methylation relative to breast cancer subtype and matched normal tissue reveals distinct patterns

Due to the heterogeneous nature of breast cancer and the widespread use of single-gene studies, there is limited knowledge of multi-gene, locus-specific DNA methylation patterns in relation to molecular subtype and clinical features. We, therefore, quantified DNA methylation of 70 candidate gene loci in 140 breast tumors and matched normal tissues and determined associations with gene expression and tumor subtype. Using Sequenom’s EpiTYPER platform, approximately 1,200 CpGs were interrogated and revealed six DNA methylation patterns in breast tumors relative to matched normal tissue. Differential methylation of several gene loci was observed within all molecular subtypes, while other patterns were subtype-dependent. Methylation of numerous gene loci was inversely correlated with gene expression, and in some cases, this correlation was only observed within specific breast tumor subtypes. Our findings were validated on a larger set of tumors and matched adjacent normal tissue from The Cancer Genome Atlas dataset, which utilized methylation data derived from both Illumina Infinium 27 and 450 k arrays. These findings highlight the need to control for subtype when interpreting DNA methylation results, and the importance of interrogating multiple CpGs across varied gene regions.

BRCA1 promoter methylation is a marker of better response to anthracycline-based therapy in sporadic TNBC

The aim of the current study was to investigate the role of BRCA1 gene aberrations in sporadic triple-negative breast cancer (TNBC) and its impact on anthracycline-based therapy. BRCA1 promoter methylation was analyzed in 70 TNBC and compared with the clinical and pathologic characteristics. As a control group, we used 70 patients with non-TNBC. BRCA1 promoter methylation was observed in 65.2 % of patients and was similar in both groups. BRCA1 promoter methylation was associated with decreased intensity of BRCA1 protein expression (P = 0.002) and significant increase of median disease-free survival (DFS) of TNBC patients receiving adjuvant anthracycline-based chemotherapy (P = 0.001). Multivariate analysis revealed that BRCA1 promoter methylation remains a favorable factor in regard to DFS (HR 0.224; 95 % CI 0.092-0.546, P = 0.001) in TNBC after adjustment for other prognostic factors. In contrast, in non-TNBC, BRCA1 promoter methylation was not associated with any clinical and pathologic parameters. BRCA1 promoter methylation is a common mechanism of BRCA1 gene aberration in sporadic breast cancer and is predictive for better response to anthracycline-based therapies.

Different methylation and microRNA expression pattern in male and female familial breast cancer

Epigenetic regulation, has been very scarcely explored in familial breast cancer (BC). In the present study RASSF1A and RAR beta promoter methylation and miR17, miR21, miR 124, and let-7a expression were investigated to highlight possible differences of epigenetic regulation between male and female familial BC, also in comparison with sporadic BC. These epigenetic alterations were studied in 56 familial BC patients (27 males and 29 females) and in 16 female sporadic cases. RASSF1A resulted more frequently methylated in men than women (76% vs. 28%, respectively, P = 0.0001), while miR17 and let-7a expression frequency was higher in women than in men (miR17: 66% in women vs. 41% in men, P < 0.05; let-7a: 45% in women vs. 15% in men, P = 0.015). RASSF1A methylation affected 27.6% of familial BC while 83% of familial cases showed high expression of the gene (P = 0.025); on the contrary, only 17% of familial BC presented RAR beta methylation and 55% of familial cases overexpressed this gene (P = 0.005). Moreover, miR17, miR21, and let-7a resulted significantly overexpressed in familial compared to sporadic BC. RASSF1A overexpression (86% vs. 65%, P = 0.13) and RAR beta overexpression (57% vs. 32%, P = 0.11) were higher in BRCA1/2 carriers even if not statistical significance was reached. BRCA mutation carriers also demonstrated significant overexpression of: miR17 (93% vs. 35%, P = 0.0001), let-7a (64% vs. 16%, P = 0.002), and of miR21 (100% vs. 65%, P = 0.008). In conclusion, the present data suggest the involvement of RASSF1A in familial male BC, while miR17 and let-7a seem to be implied in familial female BC.

Redefining the impact of nutrition on breast cancer incidence: is epigenetics involved?

Breast cancer incidence is rising worldwide with an increase in aggressive neoplasias in young women. Possible factors involved include lifestyle changes, notably diet that is known to make an impact on gene transcription. However, among dietary factors, there is sufficient support for only greater body weight and alcohol consumption whereas numerous studies revealing an impact of specific diets and nutrients on breast cancer risk show conflicting results. Also, little information is available from middle- and low-income countries. The diversity of gene expression profiles found in breast cancers indicates that transcription control is critical for the outcome of the disease. This suggests the need for studies on nutrients that affect epigenetic mechanisms of transcription, such as DNA methylation and post-translational modifications of histones. In the present review, a new examination of the relationship between diet and breast cancer based on transcription control is proposed in light of epidemiological, animal and clinical studies. The mechanisms underlying the impact of diets on breast cancer development and factors that impede reaching clear conclusions are discussed. Understanding the interaction between nutrition and epigenetics (gene expression control via chromatin structure) is critical in light of the influence of diet during early stages of mammary gland development on breast cancer risk, suggesting a persistent effect on gene expression as shown by the influence of certain nutrients on DNA methylation. Successful development of breast cancer prevention strategies will require appropriate models, identification of biological markers for rapid assessment of preventive interventions, and coordinated worldwide research to discern the effects of diet.

Epigenetic progression of columnar cell lesions of the breast to invasive breast cancer

Promoter hypermethylation of several tumour suppressor genes often occurs during breast carcinogenesis, but little is known about epigenetic silencing in the possible precursor columnar cell lesion (CCL). Promoter hypermethylation of 50 different tumour suppressor genes was assessed in normal breast tissue (N = 10), CCL (N = 15), ductal carcinoma in situ (DCIS) grade I originating in CCL (N = 5) and paired CCL (N = 15) with DCIS (N = 7) and/or invasive carcinoma (N = 14) by Methylation-specific multiplex ligation-dependent probe amplification. Increasing mean cumulative methylation levels were found from normal breast tissue to CCL to DCIS and invasive carcinoma (P < 0.001) with similar methylation levels in DCIS and invasive carcinoma. Methylation levels and frequencies (in the overall analysis and analysis of only the synchronous lesions) were the highest for RASSF1, CCND2, ID4, SCGB3A1 and CDH13. The methylation levels of ID4, CCND2, and CDH13 increased significantly from normal breast tissue to CCL and to DCIS/invasive carcinoma. RASSF1, SCGB3A1 and SFRP5 had significant higher methylation levels in CCL compared to normal breast tissue, but showed no significant differences between CCL, DCIS and invasive carcinoma. Also, no difference was found between CCLs with and without atypia, or CCLs with or without synchronous cancer. In conclusion, promoter hypermethylation for several established tumour suppressor genes is already present in CCLs, underlining that promoter hypermethylation is an early event in breast carcinogenesis. Atypia in CCL or the presence of synchronous more advanced lesions does not seem to be accompanied by higher methylation levels.

Promoter hypermethylation in male breast cancer: analysis by multiplex ligation-dependent probe amplification

Introduction

Epigenetic events are, along with genetic alteration, important in the development and progression of cancer. Promoter hypermethylation causes gene silencing and is thought to be an early event in carcinogenesis. The role of promoter hypermethylation in male breast cancer has not yet been studied.

Methods

In a group of 108 male breast cancers, the methylation status of 25 genes was studied using methylation-specific multiplex ligation-dependent probe amplification. Methylation of more than 15% was regarded indicative for promoter hypermethylation. Methylation status was correlated with clinicopathological features, with patients' outcome and with 28 female breast cancer cases.

Results

Promoter hypermethylation of the genes MSH6, WT1, PAX5, CDH13, GATA5 and PAX6 was seen in more than 50% of the cases, but was uncommon or absent in normal male breast tissue. High overall methylation status was correlated with high grade (P = 0.003) and was an independent predictor of poor survival (P = 0.048; hazard ratio 2.5). ESR1 and GSTP1 hypermethylation were associated with high mitotic count (P = 0.037 and P = 0.002, respectively) and high grade (both P = 0.001). No correlation with survival was seen for individual genes. Compared with female breast cancers (logistic regression), promoter hypermethylation was less common in a variety of genes, particularly ESR1 (P = 0.005), BRCA1 (P = 0.010) and BRCA2 (P < 0.001). The most frequently hypermethylated genes (MSH6, CDH13, PAX5, PAX6 and WT1) were similar for male and female breast cancer.

Conclusion

Promoter hypermethylation is common in male breast cancer and high methylation status correlates with aggressive phenotype and poor survival. ESR1 and GSTP1 promoter hypermethylation seem to be involved in development and/or progression of high-grade male breast cancer. Although female and male breast cancer share a set of commonly methylated genes, many of the studied genes are less frequently methylated in male breast cancer, pointing towards possible differences between male and female breast carcinogenesis.

Epigenetic modification and cancer: mark or stamp?

Hypotheses are built upon data, but data require hypotheses before they can be understood. The development of the 'two-hit' hypothesis of carcinogenesis was a key event in cancer genetics because it provided a testable model of how tumours develop. In this commentary on 'Promoter hypermethylation patterns in Fallopian tube epithelium of BRCA1 and BRCA2 germline mutation carriers' by Bijron et al. published in the February 2012 issue of Endocrine-Related Cancer, the need for new grammar and some new hypotheses in epigenetics is discussed. Meanwhile, data suggesting an important role of epigenetic modification in the cause, progression and treatment of cancer continues to accumulate.

Distinct patterns of promoter CpG island methylation of breast cancer subtypes are associated with stem cell phenotypes

Although DNA methylation profiles in breast cancer have been connected to breast cancer molecular subtype, there have been no studies of the association of DNA methylation with stem cell phenotype. This study was designed to evaluate the promoter CpG island methylation of 15 genes in relation to breast cancer subtype, and to investigate whether the patterns of CpG island methylation in each subtype are associated with their cancer stem cell phenotype represented by CD44+/CD24- and ALDH1 expression. We performed MethyLight analysis of the methylation status of 15 promoter CpG island loci involved in breast cancer progression (APC, DLEC1, GRIN2B, GSTP1, HOXA1, HOXA10, IGF2, MT1G, RARB, RASSF1A, RUNX3, SCGB3A1, SFRP1, SFRP4, and TMEFF2) and determined cancer stem cell phenotype by CD44/CD24 and ALDH1 immunohistochemistry in 36 luminal A, 33 luminal B, 30 luminal-HER2, 40 HER2 enriched, and 40 basal-like subtypes of breast cancer. The number of CpG island loci methylated differed significantly between subtypes, and was highest in the luminal-HER2 subtype and lowest in the basal-like subtype. Methylation frequencies and levels in 12 of the 15 genes differed significantly between subtypes, and the basal-like subtype had significantly lower methylation frequencies and levels in nine of the genes than the other subtypes. CD44+/CD24- and ALDH1+ putative stem cell populations were most enriched in the basal-like subtype. Methylation of promoter CpG islands was significantly lower in CD44+/CD24-cell (+) tumors than in CD44+/CD24-cell (-) tumors, even within the basal-like subtype. ALDH1 (+) tumors were also less methylated than ALDH1 (-) tumors. Our findings showed that promoter CpG island methylation was different in relation to breast cancer subtype and stem cell phenotype of tumor, suggesting that breast cancers have distinct patterns of CpG island methylation according to molecular subtypes and these are associated with different stem cell phenotypes of the tumor.

Promoter hypermethylation patterns in fallopian tube epithelium of BRCA1 and BRCA2 germ line mutation carriers

BRCA1/2 germ line mutation carriers have a high risk of developing fallopian tube carcinoma (FTC), thought to occur through different early (p53 signatures) and later (dysplasia, intra-epithelial carcinoma) premalignant stages. Promoter hypermethylation of tumour suppressor genes is known to play a key role in (early) carcinogenesis. However, little is known about methylation in normal and (pre)malignant fallopian tube tissue. We identified 14 areas of p53 accumulation in the fallopian tubes of BRCA mutation carriers. Cells from these areas were harvested together with cells from adjacent benign appearing areas. An age-matched non-BRCA sporadic control group (n=13) and eight sporadic FTCs were included as negative and positive controls respectively. Methylation-specific multiplex ligation-dependent probe amplification was used to assess promoter methylation of 70 tumour suppressor genes in all samples. We observed a gradual increase in methylation from sporadic control tissue (median cumulative methylation index (CMI) 568.19) through normal tissue and from areas of p53 accumulation in BRCA carriers (median CMI 687.54 and 676.72) to FTC (median CMI 780.97). Furthermore, the methylation percentage of many individual tumour suppressor genes differed significantly between these groups, gradually increasing as for CMI. Between areas with and without p53 accumulation in BRCA mutation carriers no significant differences were found. In this paper, we have shown that BRCA mutation carriers display increased methylation of tumour suppressor genes in their non-malignant fallopian tube epithelium, closer to methylation levels in FTC than to normal sporadic tissue. Methylation could, therefore, play an important role in the increased risk of gynaecological malignancies in BRCA mutation carriers.

Genomic instability in breast and ovarian cancers: translation into clinical predictive biomarkers

Breast and ovarian cancer are among the most common malignancies diagnosed in women worldwide. Together, they account for the majority of cancer-related deaths in women. These cancer types share a number of features, including their association with hereditary cancer syndromes caused by heterozygous germline mutations in BRCA1 or BRCA2. BRCA-associated breast and ovarian cancers are hallmarked by genomic instability and high sensitivity to DNA double-strand break (DSB) inducing agents due to loss of error-free DSB repair via homologous recombination (HR). Recently, poly(ADP-ribose) polymerase inhibitors, a new class of drugs that selectively target HR-deficient tumor cells, have been shown to be highly active in BRCA-associated breast and ovarian cancers. This finding has renewed interest in hallmarks of HR deficiency and the use of other DSB-inducing agents, such as platinum salts or bifunctional alkylators, in breast and ovarian cancer patients. In this review we discuss the similarities between breast and ovarian cancer, the hallmarks of genomic instability in BRCA-mutated and BRCA-like breast and ovarian cancers, and the efforts to search for predictive markers of HR deficiency in order to individualize therapy in breast and ovarian cancer.

Methylation profiles of the BRCA1 promoter in hereditary and sporadic breast cancer among Han Chinese

The development of breast cancer is a multistep process associated with complex changes in host gene expression patterns including inactivation of tumor suppressor genes and activation of oncogenes. Critically, hereditary predisposition plays a significant role in cancer susceptibility. However, mutation of the BRCA1 gene is found only in the minority of hereditary breast cancer, which indicates that there might be alternative, novel mechanisms contributing to inactivation of the BRCA1 gene. Studies have shown that aberrant methylation of genomic DNA plays an important role in carcinogenesis. The aim of this study was to investigate whether DNA methylation may be an alternative mechanism for the inactivation of BRCA1 as an epigenetic modification of the genome and whether hereditary breast cancer has a different BRCA1 methylation phenotype pattern than sporadic breast cancer. The pattern of CpG island methylation within the promoter region of BRCA1 was assessed by bisulfite sequencing DNA from peripheral blood cells of 72 patients with hereditary predisposition but without BRCA1 mutations and 30 sporadic breast cancer controls. The overall methylation level in patients with hereditary predisposition was significantly lower than that in the sporadic control group. However, patients with hereditary predisposition showed a significantly higher methylation susceptibility for the sites -518 when compared to controls. These results suggest that there might be different BRCA1 promoter methylation levels and patterns in sporadic and hereditary breast cancer in peripheral blood DNA. These findings may facilitate the early diagnosis of hereditary breast cancer.

Aberrant promoter CpG methylation and its translational applications in breast cancer

Breast cancer is a complex disease driven by multiple factors including both genetic and epigenetic alterations. Recent studies revealed that abnormal gene expression induced by epigenetic changes, including aberrant promoter methylation and histone modification, plays a critical role in human breast Carcinogenesis. Silencing of tumor suppressor genes (TSGs) by promoter CpG methylation facilitates cells growth and survival advantages and further results in tumor initiation and progression, thus directly contributing to breast tumorigenesis. Usually, aberrant promoter methylation of TSGs, which can be reversed by pharmacological reagents, occurs at the early stage of tumorigenesis and therefore may serve as a potential tumor marker for early diagnosis and therapeutic targeting of breast cancer. In this review, we summarize the epigenetic changes of multiple TSGs involved in breast pathogenesis and their potential clinical applications as tumor markers for early detection and treatment of breast cancer.

Methylated genes in breast cancer: associations with clinical and histopathological features in a familial breast cancer cohort

BACKGROUND

Hundreds of hypermethylated genes have been described in breast cancer, yet the nature and contribution of these genes in their methylated state to overall risk and prognosis is under-characterized in non-sporadic breast cancers. We therefore compared associations of DNA methylation with tumor stage, hormone/growth receptor status, and clinical outcomes in a familial breast cancer cohort. Because few previous methylation studies have considered the oncogenic or tumor suppressor properties of their gene sets, this functional status was included as part of our correlative analysis.

RESULTS

We found methylation of oncogenes was associated with better prognostic indicators, whereas tumor suppressor gene methylation was associated with a more severe phenotype in women that were either HER2+ or lymph node positive at diagnosis, and/or tended to recur or develop distant metastases. For example, the methylation of the tumor suppressor gene APC was strongly associated with a specific subset of tumors that were both ER+ and HER2+, while methylation of the TWIST oncogene was associated with breast cancers that did not metastasize.

METHODS

This was a retrospective, hospital-based study of n = 99 archival breast tumors derived from women with a germline genetic BRCA1 or BRCA2 mutation and/or familial breast cancer history. DNA methylation was quantified from formalin fixed, paraffin embedded tumors using the established protocol of quantitative multiplex-methylation specific PCR (QM-MSP). Non-parametric statistics were used to analyze candidate gene methylation in association with clinical outcomes.

CONCLUSION

We report several novel, positive associations between percent methylation of the APC, RASSF1A, TWIST, ERα, CDH1, and Cyclin D2 genes and key variables such as tumor stage, hormone and growth receptor status, and a history of recurrent or metastatic disease. Our data suggest the potential utility of parsing gene methylation by functional status and breast tumor subtype.

New insights into the prevention and treatment of familial breast cancer

Individuals who inherit a deleterious mutation in BRCA1 or BRCA2 are at very high risk for breast cancer but there are several strategies available for successfully managing this risk. Breast cancers that develop in the context of germline BRCA gene mutation present challenges for management but also opportunities. DNA damaging agents, like cisplatin, and the new class of drugs called PARP inhibitors exploit the underlying defect in DNA damage repair to great effect.

Genomic signature of BRCA1 deficiency in sporadic basal-like breast tumors

About 10-20% of all breast carcinomas show a basal-like phenotype, while ∼ 90% of breast tumors from BRCA1-mutation carriers are of this subtype. There is growing evidence that BRCA1-mutated tumors are not just a specific subset of the basal-like tumors, but that (the majority of) basal-like tumors show a dysfunctional BRCA1 pathway. This has major treatment implications, because emerging regimens specifically targeting DNA repair mechanisms would then be most effective against these tumors. To further understand the involvement of BRCA1 deficiency in sporadic basal-like tumors, we investigated 41 basal-like tumors for BRCA1 mRNA expression by quantitative real-time polymerase chain reaction, BRCA1 promoter methylation, their genomic profile by array-CGH, and gene expression levels by whole genome expression arrays. Array-CGH results were compared to those of 34 proven BRCA1-mutated tumors. Basal-like tumors were subdivided into two equal groups: deficient and proficient in BRCA1 gene expression. The chromosomal makeup of BRCA1 deficient sporadic basal-like tumors was similar to that of BRCA1-mutated tumors. BRCA1 proficient sporadic basal-like tumors were more similar to nonbasal-like tumors. Only half of the basal-like breast tumors are actually deficient in BRCA1 expression. Gain of chromosome arm 3q is a marker for BRCA1 deficiency in hereditary and sporadic breast tumors.

Transcriptionally repressed genes become aberrantly methylated and distinguish tumors of different lineages in breast cancer

Aberrant promoter hypermethylation is frequently observed in cancer. The potential for this mechanism to contribute to tumor development depends on whether the genes affected are repressed because of their methylation. Many aberrantly methylated genes play important roles in development and are bivalently marked in ES cells, suggesting that their aberrant methylation may reflect developmental processes. We investigated this possibility by analyzing promoter methylation in 19 breast cancer cell lines and 47 primary breast tumors. In cell lines, we defined 120 genes that were significantly repressed in association with methylation (SRAM). These genes allowed the unsupervised segregation of cell lines into epithelial (EPCAM+ve) and mesenchymal (EPCAM-ve) lineages. However, the methylated genes were already repressed in normal cells of the same lineage, and >90% could not be derepressed by treatment with 5-aza-2'-deoxycytidine. The tumor suppressor genes APC and CDH1 were among those methylated in a lineage-specific fashion. As predicted by the epithelial nature of most breast tumors, SRAM genes that were methylated in epithelial cell lines were frequently aberrantly methylated in primary tumors, as were genes specifically repressed in normal epithelial cells. An SRAM gene expression signature also correctly identified the rare claudin-low and metaplastic tumors as having mesenchymal characteristics. Our findings implicate aberrant DNA methylation as a marker of cell lineage rather than tumor progression and suggest that, in most cases, it does not cause the repression with which it is associated.