Clinical significance of promoter hypermethylation of ERβ and RARβ2 in tumor and serum DNA in Indian breast cancer patients

Noninvasive prediction of axillary lymph node status in breast cancer using promoter profiling of circulating cell-free DNA

BACKGROUND

Lymph node metastasis (LNM) is one of the most important factors affecting the prognosis of breast cancer. The accurate evaluation of lymph node status is useful to predict the outcomes of patients and guide the choice of cancer treatment. However, there is still lack of a low-cost non-invasive method to assess the status of axillary lymph node (ALN). Gene expression signature has been used to assess lymph node metastasis status of breast cancer. In addition, nucleosome footprint of cell-free DNA (cfDNA) carries gene expression information of its original tissues, so it may be used to evaluate the axillary lymph node status in breast cancer.

METHODS

In this study, we found that the cfDNA nucleosome footprints between the ALN-positive patients and ALN-negative patients showed different patterns by implementing whole-genome sequencing (WGS) to detect 15 ALN-positive and 15 ALN-negative patients. In order to further evaluate its potential for assessing ALN status, we developed a classifier with multiple machine learning models by using 330 WGS data of cfDNA from 162 ALN-positive and 168 ALN-negative samples to distinguish these two types of patients.

RESULTS

We found that the promoter profiling between the ALN-positive patients and ALN-negative patients showed distinct patterns. In addition, we observed 1071 genes with differential promoter coverage and their functions were closely related to tumorigenesis. We found that the predictive classifier based on promoter profiling with a support vector machine model, named PPCNM, produced the largest area under the curve of 0.897 (95% confidence interval 0.86-0.93).

CONCLUSIONS

These results indicate that promoter profiling can be used to distinguish ALN-positive patients from ALN-negative patients, which may be helpful to guide the choice of cancer treatment.

Clinical associations of ESR2 (estrogen receptor beta) expression across thousands of primary breast tumors

Estrogen receptor alpha (ERα, encoded by ESR1) is a well-characterized transcription factor expressed in more than 75% of breast tumors and is the key biomarker to direct endocrine therapies. On the other hand, much less is known about estrogen receptor beta (ERβ, encoded by ESR2) and its importance in cancer. Previous studies had some disagreement, however most reports suggested a more favorable prognosis for patients with high ESR2 expression. To add further clarity to ESR2 in breast cancer, we interrogated a large population-based cohort of primary breast tumors (n = 3207) from the SCAN-B study. RNA-seq shows ESR2 is expressed at low levels overall with a slight inverse correlation to ESR1 expression (Spearman R = −0.18, p = 2.2e−16), and highest ESR2 expression in the basal- and normal-like PAM50 subtypes. ESR2-high tumors had favorable overall survival (p = 0.006), particularly in subgroups receiving endocrine therapy (p = 0.03) and in triple-negative breast cancer (p = 0.01). These results were generally robust in multivariable analyses accounting for patient age, tumor size, node status, and grade. Gene modules consistent with immune response were associated to ESR2-high tumors. Taken together, our results indicate that ESR2 is generally expressed at low levels in breast cancer but associated with improved overall survival and may be related to immune response modulation.

The role of estrogen receptor beta in breast cancer

Breast cancer, a malignant tumor originating from mammary epithelial tissue, is the most common cancer among women worldwide. Challenges facing the diagnosis and treatment of breast cancer necessitate the search for new mechanisms and drugs to improve outcomes. Estrogen receptor (ER) is considered to be important for determining the diagnosis and treatment strategy. The discovery of the second estrogen receptor, ERβ, provides an opportunity to understand estrogen action. The emergence of ERβ can be traced back to 1996. Over the past 20 years, an increasing body of evidence has implicated the vital effect of ERβ in breast cancer. Although there is controversy among scholars, ERβ is generally thought to have antiproliferative effects in disease progression. This review summarizes available evidence regarding the involvement of ERβ in the clinical treatment and prognosis of breast cancer and describes signaling pathways associated with ERβ. We hope to highlight the potential of ERβ as a therapeutic target.

Prognostic DNA methylation markers for hormone receptor breast cancer: a systematic review

BACKGROUND

In patients with hormone receptor-positive breast cancer, differentiating between patients with a low and a high risk of recurrence is an ongoing challenge. In current practice, prognostic clinical parameters are used for risk prediction. DNA methylation markers have been proven to be of additional prognostic value in several cancer types. Numerous prognostic DNA methylation markers for breast cancer have been published in the literature. However, to date, none of these markers are used in clinical practice.

METHODS

We conducted a systematic review of PubMed and EMBASE to assess the number and level of evidence of published DNA methylation markers for hormone receptor-positive breast cancer. To obtain an overview of the reporting quality of the included studies, all were scored according to the REMARK criteria that were established as reporting guidelines for prognostic biomarker studies.

RESULTS

A total of 74 studies were identified reporting on 87 different DNA methylation markers. Assessment of the REMARK criteria showed variation in reporting quality of the studies. Eighteen single markers and one marker panel were studied in multiple independent populations. Hypermethylation of the markers RASSF1, BRCA, PITX2, CDH1, RARB, PCDH10 and PGR, and the marker panel GSTP1, RASSF1 and RARB showed a statistically significant correlation with poor disease outcome that was confirmed in at least one other, independent study.

CONCLUSION

This systematic review provides an overview on published prognostic DNA methylation markers for hormone receptor-positive breast cancer and identifies eight markers that have been independently validated. Analysis of the reporting quality of included studies suggests that future research on this topic would benefit from standardised reporting guidelines.

Dietary fat and obesity as modulators of breast cancer risk: Focus on DNA methylation

Breast cancer (BC) is the most common cancer and second leading cause of cancer mortality in women worldwide. Validated biomarkers enhance efforts for early detection and treatment, which reduce the risk of mortality. Epigenetic signatures have been suggested as good biomarkers for early detection, prognosis and targeted therapy of BC. Here, we highlight studies documenting the modifying effects of dietary fatty acids and obesity on BC biomarkers associated with DNA methylation. We focus our analysis on changes elicited in writers of DNA methylation (i.e., DNA methyltransferases), global DNA methylation and gene-specific DNA methylation. To provide context, we precede this discussion with a review of the available evidence for an association between BC incidence and both dietary fat consumption and obesity. We also include a review of well-vetted BC biomarkers related to cytosine-guanine dinucleotides methylation and how they influence BC risk, prognosis, tumour characteristics and response to treatment. LINKED ARTICLES: This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc.

Functional relevance of promoter CpG island of human Angiotensin II type 1 receptor (AT1R) gene

Angiotensin II type 1 receptor can activate number of signalling pathways upon stimulation and consequently its involvement in cancer progression have also been revealed. But which epigenetic mechanisms are involved in its regulation, need to be further explored. In-silico analysis revealed a promoter CpG island (CGI) which was cloned and assayed for functional activity using reporter gene system. The effect of methylation on this CGI was analysed through varying degree of methyltransferase treatment of cloned fragment. Results thus obtained were validated by direct sequencing. To further establish the status of this effect, in-vivo analysis was done through screening of methylation pattern in the targeted region among hypertensives (HTN) and normotensives (NTN) using PCR-Bisulphite sequencing. Additionally, clinical details of all participants, biochemical parameters and lifestyle related information was also collected and statistically evaluated. Reporter gene assay assigned functional activity to the cloned promoter CpG island. Increased dose and durations of methyltransferase treatment decreased the expression of reporter gene indicating the role of promoter DNA methylation. Among all the human samples screened, only one of the HTN individual was found to have single hemi-methylated CpG site at a position which happens to be a part of Sp1 transcription factor binding site. To conclude, CpG island in the promoter region of AT1R (CpG.P.AT1R) gets regulated through epigenetic mechanism of DNA methylation.

Liquid biopsy prediction of axillary lymph node metastasis, cancer recurrence, and patient survival in breast cancer: A meta-analysis

BACKGROUND

Liquid biopsies using circulating tumor DNA (ctDNA) and cell-free DNA (cfDNA) have been developed for early cancer detection and patient monitoring. To investigate the clinical usefulness of ctDNA aberrations and cfDNA levels in patients with breast cancer (BC), we conducted a meta-analysis of 69 published studies on 5736 patients with BC.

METHODS

The relevant publications were identified by searching PubMed and Embase databases. The effect sizes of outcome parameters were pooled using a random-effects model.

RESULTS

The ctDNA mutation rates of TP53, PIK3CA, and ESR1 were approximately 38%, 27%, and 32%, respectively. High levels of cfDNA were associated with BCs rather than with healthy controls. However, these detection rates were not satisfactory for BC screening. Although the precise mechanisms have been unknown, high cfDNA levels were significantly associated with axillary lymph node metastasis (odds ratio [OR] = 2.148, P = .030). The ctDNA mutations were significantly associated with cancer recurrence (OR = 3.793, P < .001), short disease-free survival (univariate hazard ratio [HR] = 5.180, P = .026; multivariate HR = 3.605, P = .001), and progression-free survival (HR = 1.311, P = .013) rates, and poor overall survival outcomes (HR = 2.425, P = .007).

CONCLUSION

This meta-analysis demonstrates that ctDNA mutation status predicts disease recurrence and unfavorable survival outcomes, while cfDNA levels can be predictive of axillary lymph node metastasis in patients with BC.

Preliminary analysis of the association between methylation of the ACE2 promoter and essential hypertension

The aim of the present study was to investigate whether methylation of the angiotensin I converting enzyme 2 (ACE2) promoter increases the risk of essential hypertension (EH). A total of 96 patients with EH were recruited and 96 sex‑ and age‑matched healthy controls. Methylation of 5 CpG dinucleotides in the ACE2 promoter was quantified using bisulfite pyrosequencing. Logistic regression and multiple linear regression were used to adjust for confounding factors and the generalized multifactor dimensionality reduction (GMDR) method was applied to investigate high‑order interactions. Methylation of CpG4 (adjusted P=0.020) and CpG5 (adjusted P=0.036) was significantly higher in patients with EH, with frequency 97.56±5.65% and 12.75±4.15% in EH individuals and 95.73±9.11% and 11.47±3.67% in healthy controls. GMDR detected significant interaction among the 5 CpG sites (odds ratio=7.33, adjusted P=0.01). Furthermore, receiver operating characteristic curves identified that CpG5 methylation was a significant predictor of EH. Notably, CpG2 methylation was significantly higher in males than in females (adjusted P=0.018). Conversely, CpG5 methylation was significantly lower in males (adjusted P=0.032). These results indicated that aberrant methylation of the ACE2 promoter may be associated with EH risk. In addition, sex may significantly influence ACE2 methylation.

Circulating Tumor DNA as Biomarkers for Cancer Detection

Detection of circulating tumor DNAs (ctDNAs) in cancer patients is an important component of cancer precision medicine ctDNAs. Compared to the traditional physical and biochemical methods, blood-based ctDNA detection offers a non-invasive and easily accessible way for cancer diagnosis, prognostic determination, and guidance for treatment. While studies on this topic are currently underway, clinical translation of ctDNA detection in various types of cancers has been attracting much attention, due to the great potential of ctDNA as blood-based biomarkers for early diagnosis and treatment of cancers. ctDNAs are detected and tracked primarily based on tumor-related genetic and epigenetic alterations. In this article, we reviewed the available studies on ctDNA detection and described the representative methods. We also discussed the current understanding of ctDNAs in cancer patients and their availability as potential biomarkers for clinical purposes. Considering the progress made and challenges involved in accurate detection of specific cell-free nucleic acids, ctDNAs hold promise to serve as biomarkers for cancer patients, and further validation is needed prior to their broad clinical use.

Methylated circulating tumor DNA in blood: power in cancer prognosis and response

Circulating tumor DNA (ctDNA) in the plasma or serum of cancer patients provides an opportunity for non-invasive sampling of tumor DNA. This 'liquid biopsy' allows for interrogations of DNA such as quantity, chromosomal alterations, sequence mutations and epigenetic changes, and can be used to guide and improve treatment throughout the course of the disease. This tremendous potential for real-time 'tracking' in a cancer patient has led to substantial research efforts in the ctDNA field. ctDNA can be distinguished from non-tumor DNA by the presence of tumor-specific mutations and copy number variations, and also by aberrant DNA methylation, with both DNA sequence and methylation changes corresponding to those found in the tumor. Aberrant methylation of specific promoter regions can be a very consistent feature of cancer, in contrast to mutations, which typically occur at a wide range of sites. This consistency makes ctDNA methylation amenable to the design of widely applicable clinical assays. In this review, we examine ctDNA methylation in the context of monitoring disease status, treatment response and determining the prognosis of cancer patients.

Do circulating tumor cells, exosomes, and circulating tumor nucleic acids have clinical utility? A report of the association for molecular pathology

Diagnosing and screening for tumors through noninvasive means represent an important paradigm shift in precision medicine. In contrast to tissue biopsy, detection of circulating tumor cells (CTCs) and circulating tumor nucleic acids provides a minimally invasive method for predictive and prognostic marker detection. This allows early and serial assessment of metastatic disease, including follow-up during remission, characterization of treatment effects, and clonal evolution. Isolation and characterization of CTCs and circulating tumor DNA (ctDNA) are likely to improve cancer diagnosis, treatment, and minimal residual disease monitoring. However, more trials are required to validate the clinical utility of precise molecular markers for a variety of tumor types. This review focuses on the clinical utility of CTCs and ctDNA testing in patients with solid tumors, including somatic and epigenetic alterations that can be detected. A comparison of methods used to isolate and detect CTCs and some of the intricacies of the characterization of the ctDNA are also provided.

Epigenetic Biomarkers of Breast Cancer Risk: Across the Breast Cancer Prevention Continuum

Epigenetic biomarkers, such as DNA methylation, can increase cancer risk through altering gene expression. The Cancer Genome Atlas (TCGA) Network has demonstrated breast cancer-specific DNA methylation signatures. DNA methylation signatures measured at the time of diagnosis may prove important for treatment options and in predicting disease-free and overall survival (tertiary prevention). DNA methylation measurement in cell free DNA may also be useful in improving early detection by measuring tumor DNA released into the blood (secondary prevention). Most evidence evaluating the use of DNA methylation markers in tertiary and secondary prevention efforts for breast cancer comes from studies that are cross-sectional or retrospective with limited corresponding epidemiologic data, raising concerns about temporality. Few prospective studies exist that are large enough to address whether DNA methylation markers add to the prediction of tertiary and secondary outcomes over and beyond standard clinical measures. Determining the role of epigenetic biomarkers in primary prevention can help in identifying modifiable pathways for targeting interventions and reducing disease incidence. The potential is great for DNA methylation markers to improve cancer outcomes across the prevention continuum. Large, prospective epidemiological studies will provide essential evidence of the overall utility of adding these markers to primary prevention efforts, screening, and clinical care.

Association of AGTR1 Promoter Methylation Levels with Essential Hypertension Risk: A Matched Case-Control Study

The purpose of the present study was to investigate whether methylation of the angiotensin II type 1 receptor (AGTR1) promoter contributed to the risk of essential hypertension (EH). A total of 96 EH cases and 96 gender- and age-matched healthy controls were recruited. Methylation of 8 CpG dinucleotides (CpG1-8) in the AGTR1 promoter was examined using the bisulphite pyrosequencing technology. Three CpG dinucleotides (CpG6-8) could not be well sequenced, therefore only the remaining 5 CpG sites were analysed. A significantly lower CpG1 methylation level was identified in EH cases than in controls (cases vs. controls: 6.74 ± 4.32% vs. 9.66 ± 5.45%, p = 0.007), and no significant association was observed in the remaining analyses. In addition, significantly lower CpG1 (p = 0.028) and higher CpG2 (p = 0.032) methylation levels were observed in males than in females. In the breakdown association test by gender, a higher CpG1 methylation level was also identified in EH in both males (p = 0.034) and females (p = 0.020). Receiver operating characteristic curves showed that CpG1 methylation was a significant predictor of EH. Furthermore, CpG1 methylation was inversely correlated with uric acid levels in controls. The present study suggests that CpG1 hypomethylation in the AGTR1 promoter is likely associated with the risk of EH in the population assessed.

Circulating DNA and Survival in Solid Tumors

BACKGROUND

The ability to undertake molecular analysis to inform on prognosis and predictors of response to therapy is limited by accessibility of tissue. Measurement of total circulating free DNA (cfDNA) or circulating tumor DNA (ctDNA) in peripheral blood may allow easier access to tumor material and help to predict clinical outcomes.

METHODS

A systematic review of electronic databases identified publications exploring the association between cfDNA or ctDNA and overall survival (OS) in solid tumors. HRs for OS were extracted from multivariable analyses and included in a meta-analysis. Pooled HRs were computed and weighted using generic inverse variance and random-effect modeling. For studies not reporting multivariable analyses, univariable ORs were estimated from Kaplan-Meier curves for OS at 1 and 3 years.

RESULTS

Thirty-nine studies comprising 4,052 patients were included in the analysis. Detection of ctDNA was associated with a significantly worse OS in multivariable analyses [HR, 2.70; 95% confidence interval (CI), 2.02-3.61; P < 0.001). Similar results were observed in the univariable analyses at 3 and 1 year (OR, 4.83; 95% CI, 3.20-7.28; P < 0.001).There was also a statistically significant association between high total cfDNA and worse OS for studies reporting multivariable and univariate data at 3 years (HR, 1.91; 95% CI, 1.59-2.29; P < 0.001 and OR, 2.82; 95% CI, 1.93-4.13; P < 0.001, respectively).

CONCLUSIONS

High levels of total cfDNA and presence of ctDNA are associated with worse survival in solid tumors.

IMPACT

Circulating DNA is associated with worse outcome in solid tumors.

Promoter Methylation of the Retinoic Acid Receptor Beta2 (RARβ2) Is Associated with Increased Risk of Breast Cancer: A PRISMA Compliant Meta-Analysis

Background

Epigenetic studies demonstrate that an association may exist between methylation of the retinoic acid receptor beta2 (RARβ2) gene promoter and breast cancer onset risk, tumor stage, and histological grade, however the results of these studies are not consistent. Hence, we performed this meta-analysis to ascertain a more comprehensive and accurate association.

Materials and Methods

Relevant studies were retrieved from the PubMed, Embase and Chinese National Knowledge Infrastructure databases up to February 28, 2015. After two independent reviewers screened the studies and extracted the necessary data, meta-analysis was performed using Review Manager 5.2 software.

Results

Nineteen eligible articles, including 20 studies, were included in our analysis. Compared to non-cancerous controls, the frequency of RARβ2 methylation was 7.27 times higher in patients with breast cancer (odds ratio (OR) = 7.27, 95% confidence interval (CI) = 3.01–17.52). Compared to late-stage RARβ2 methylated patients, the pooled OR of early-stage ones was 0.81 (OR = 0.81, 95% CI = 0.55–1.17). The OR of low-grade RARβ2 methylated patients was 0.96 (OR = 0.96, 95% CI = 0.74–1.25) compared to high-grade RARβ2 methylated patients.

Conclusion

RARβ2 methylation is significantly increased in breast cancer samples when compared to non-cancerous controls. RARβ2 could serve as a potential epigenetic marker for breast cancer detection and management.

Promoter Hypermethylation in White Blood Cell DNA and Breast Cancer Risk

The role of gene-specific methylation in white blood cells (WBC) as a marker of breast cancer risk is currently unclear. We determined whether promoter hypermethylation in blood DNA of candidate tumor suppressor genes frequently methylated in breast tumors can be used as a surrogate biomarker for breast cancer risk. Promoter methylation of BRCA1, CDH1 and RARβ was analyzed in WBC DNA from a population-based sample of 1,021 breast cancer patients and 1,036 controls by the MethyLight assay. Gene-specific promoter methylation in the DNA of 569 tumor tissue samples was also analyzed to determine the correlation of methylation levels with blood from the same individual. Hypermethylation of BRCA1 (OR: 1.31; 95% CI: 0.98-1.75) in WBC was associated with an increased risk of breast cancer when positive methylation was defined as ≥0.1% methylated. There was lack of concordance between tumor tissue and paired WBC DNA methylation. These results provide limited support that hypermethylation of BRCA1 in WBC DNA may be useful for determination of breast cancer risk. Additional studies with larger numbers of genes are needed to fully understand the relationship between WBC methylation and breast cancer risk.

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.

Interplay between estrogen and retinoid signaling in breast cancer--current and future perspectives

All-trans-retinoic acid (RA) is a promising agent for breast cancer treatment, but it induces several adverse effects and the few clinical trials performed up to now in breast cancer patients have provided disappointing results. The combination of RA and antiestrogenic compounds, such as tamoxifen, synergistically decreases the proliferation of breast cancer cells and an interplay between retinoid and estrogen signaling has begun to be unraveled, turning these combinations into an appealing strategy for breast cancer treatment. This review focus on the current knowledge regarding the interplay between retinoid and estrogen signaling in breast cancer and the combinations of RA with antiestrogens, aiming their future utilization in cancer therapy.

Regulation of estrogen receptor β1 expression in breast cancer by epigenetic modification of the 5' regulatory region

ERβ1 is often down-regulated in breast cancer compared to normal breast but mechanisms surrounding this are unclear. We examined whether loss of heterozygosity (LOH) or methylation at ERβ promoters (0N, 0K) and/or untranslated exon 0N were involved in ERβ down-regulation in breast cancer tissues and cell lines and if treatment with the de-methylating agent 5-aza-deoxycytidine and/or the histone deacetylase inhibitor Trichostatin A could influence expression in vitro. We found no evidence of correlation between LOH at 14q22-24 (genomic locus containing ERβ/ESR2), and ERβ1 expression in primary breast cancers. A negative correlation between ERβ1 mRNA expression and methylation status was observed for promoter 0N in BT-20, MDA-MB-453 and T47D cells. Promoter 0K was consistently unmethylated. In primary breast tumours, methylation of the untranslated exon 0N, downstream of promoter 0N, but not of promoter 0N itself, correlated with down-regulation of ERβ. In MDA-MB-453 cells, treatment with 5-aza-deoxycytidine was sufficient to induce ERβ1 expression from the 0N promoter while in BT-20 both agents were required. Examination of various sites on ESR2 highlighted epigenetic but not genetic regulation of ERβ1. In particular methylation adjacent to promoter 0N was a key regulatory event for ERβ1 silencing. A combination of de-methylating agents and histone deacetylase inhibitors fully restored ERβ1 expression which may offer a novel therapeutic angle for breast cancer management.

The clinical utilization of circulating cell free DNA (CCFDNA) in blood of cancer patients

Qualitative and quantitative testing of circulating cell free DNA (CCFDNA) can be applied for the management of malignant and benign neoplasms. Detecting circulating DNA in cancer patients may help develop a DNA profile for early stage diagnosis in malignancies. The technical issues of obtaining, using, and analyzing CCFDNA from blood will be discussed.

Circulating nucleic acids as biomarkers in breast cancer

During tumor development, tumor cells release their nucleic acids into the blood circulation. This process occurs by apoptotic and necrotic cell deaths along with active cell secretion, resulting in high levels of circulating DNA, mRNA, and microRNA in the blood of patients with breast cancer. As circulating cell-free tumor nucleic acids may reflect the characteristics of the primary tumor and even of micrometastatic cells, they may be excellent blood biomarkers for screening breast cancer. Assays that allow the repetitive monitoring of patients by using blood samples as liquid biopsy may be efficient in assessing cancer progression in patients whose tumor tissue is not available. This review evaluates the recent data on the potential use of circulating cell-free nucleic acids as biomarkers for breast cancer.