DNA methylation index and methylation profile of invasive ductal breast tumors

Droplet digital PCR analysis of CDH13 methylation status in Slovak women with invasive ductal breast cancer

Identifying novel epigenetic biomarkers is a promising way to improve the clinical management of patients with breast cancer. Our study aimed to determine the methylation pattern of 25 tumor suppressor genes (TSG) and select the best methylation biomarker associated with clinicopathological features in the cohort of Slovak patients diagnosed with invasive ductal carcinoma (IDC). Overall, 166 formalin-fixed, paraffin-embedded (FFPE) tissues obtained from patients with IDC were included in the study. The methylation status of the promoter regions of 25 TSG was analyzed using semiquantitative methylation-specific MLPA (MS-MLPA). We identified CDH13 as the most frequently methylated gene in our cohort of patients. Further analysis by ddPCR confirmed an increased level of methylation in the promoter region of CDH13. A significant difference in CDH13 methylation levels was observed between IDC molecular subtypes LUM A versus HER2 (P = 0.0116) and HER2 versus TNBC (P = 0.0234). In addition, significantly higher methylation was detected in HER2+ versus HER2- tumors (P = 0.0004) and PR- versus PR+ tumors (P = 0.0421). Our results provide evidence that alteration in CDH13 methylation is associated with clinicopathological features in the cohort of Slovak patients with IDC. In addition, using ddPCR as a methylation-sensitive method represents a promising approach characterized by higher precision and technical simplicity to measure the methylation of target CpGs in CDH13 compared to other conventional methods such as MS-MLPA.

The Yin and Yang of Breast Cancer: Ion Channels as Determinants of Left-Right Functional Differences

Breast cancer is a complex and heterogeneous disease that displays diverse molecular subtypes and clinical outcomes. Although it is known that the location of tumors can affect their biological behavior, the underlying mechanisms are not fully understood. In our previous study, we found a differential methylation profile and membrane potential between left (L)- and right (R)-sided breast tumors. In this current study, we aimed to identify the ion channels responsible for this phenomenon and determine any associated phenotypic features. To achieve this, experiments were conducted in mammary tumors in mice, human patient samples, and with data from public datasets. The results revealed that L-sided tumors have a more depolarized state than R-sided. We identified a 6-ion channel-gene signature (CACNA1C, CACNA2D2, CACNB2, KCNJ11, SCN3A, and SCN3B) associated with the side: L-tumors exhibit lower expression levels than R-tumors. Additionally, in silico analyses show that the signature correlates inversely with DNA methylation writers and with key biological processes involved in cancer progression, such as proliferation and stemness. The signature also correlates inversely with patient survival rates. In an in vivo mouse model, we confirmed that KI67 and CD44 markers were increased in L-sided tumors and a similar tendency for KI67 was found in patient L-tumors. Overall, this study provides new insights into the potential impact of anatomical location on breast cancer biology and highlights the need for further investigation into possible differential treatment options.

When left does not seem right: epigenetic and bioelectric differences between left- and right-sided breast cancer

Background

During embryogenesis lateral symmetry is broken, giving rise to Left/Right (L/R) breast tissues with distinct identity. L/R-sided breast tumors exhibit consistently-biased incidence, gene expression, and DNA methylation. We postulate that a differential L/R tumor-microenvironment crosstalk generates different tumorigenesis mechanisms.

Methods

We performed in-silico analyses on breast tumors of public datasets, developed xenografted tumors, and conditioned MDA-MB-231 cells with L/R mammary extracts.

Results

We found L/R differential DNA methylation involved in embryogenic and neuron-like functions. Focusing on ion-channels, we discovered significant L/R epigenetic and bioelectric differences. Specifically, L-sided cells presented increased methylation of hyperpolarizing ion channel genes and increased Ca²⁺ concentration and depolarized membrane potential, compared to R-ones. Functional consequences were associated with increased proliferation in left tumors, assessed by KI67 expression and mitotic count.

Conclusions

Our findings reveal considerable L/R asymmetry in cancer processes, and suggest specific L/R epigenetic and bioelectric differences as future targets for cancer therapeutic approaches in the breast and many other paired organs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00440-5.

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.

Hemimethylation Patterns in Breast Cancer Cell Lines

DNA methylation is an epigenetic event that involves adding a methyl group to the cytosine (C) site, especially the one that pairs with a guanine (G) site (ie, CG or CpG site), in a human genome. This event plays an important role in both cancerous and normal cell development. Previous studies often assume symmetric methylation on both DNA strands. However, asymmetric methylation, or hemimethylation (methylation that occurs only on 1 DNA strand), does exist and has been reported in several studies. Due to the limitation of previous DNA methylation sequencing technologies, researchers could only study hemimethylation on specific genes, but the overall genomic hemimethylation landscape remains relatively unexplored. With the development of advanced next-generation sequencing techniques, it is now possible to measure methylation levels on both forward and reverse strands at all CpG sites in an entire genome. Analyzing hemimethylation patterns may potentially reveal regions related to undergoing tumor growth. For our research, we first identify hemimethylated CpG sites in breast cancer cell lines using Wilcoxon signed rank tests. We then identify hemimethylation patterns by grouping consecutive hemimethylated CpG sites based on their methylation states, methylation "M" or unmethylation "U." These patterns include regular (or consecutive) hemimethylation clusters (eg, "MMM" on one strand and "UUU" on another strand) and polarity (or reverse) clusters (eg, "MU" on one strand and "UM" on another strand). Our results reveal that most hemimethylation clusters are the polarity type, and hemimethylation does occur across the entire genome with notably higher numbers in the breast cancer cell lines. The lengths or sizes of most hemimethylation clusters are very short, often less than 50 base pairs. After mapping hemimethylation clusters and sites to corresponding genes, we study the functions of these genes and find that several of the highly hemimethylated genes may influence tumor growth or suppression. These genes may also indicate a progressing transition to a new tumor stage.

Promoter hypermethylation in ductal carcinoma in situ of the male breast

Ductal carcinoma in situ (DCIS) of the male breast is very rare and has hardly been studied molecularly. In males, we compared methylation status of 25 breast cancer-related genes in pure DCIS (n = 18) and invasive breast carcinoma (IBC) with adjacent DCIS (DCIS-AIC) (n = 44) using methylation-specific multiplex ligation-dependent probe amplification. Results were compared to female breast cancer (BC). There were no significant differences in methylation features between male pure DCIS, DCIS-AIC and IBC after correction for multiple comparisons. In paired analysis of IBC and adjacent DCIS, CADM1 showed a significantly higher absolute methylation percentage in DCIS (P = 0.002). In cluster analysis, two clusters stood out with respectively infrequent and frequent methylation (GATA5, KLLN, PAX6, PAX5, CDH13, MSH6 and WT1 were frequently methylated). Compared to female DCIS, methylation was in general much less common in male DCIS, especially for VHL, ESR1, CDKN2A, CD44, CHFR, BRCA2, RB1 and STK11. In contrast, THBS1 and GATA5 were more frequently methylated in male DCIS. In conclusion, there is frequent methylation of GATA5, KLLN, PAX6, PAX5, CDH13, MSH6 and WT1 in male DCIS. Since there was little change in the methylation status for the studied genes from pure male DCIS to DCIS-AIC and IBC, methylation of these seven genes is more likely to occur early in male breast carcinogenesis. Based on the current markers male DCIS seems to be an epigenetically more advanced precursor of male BC, although in comparison to its female counterpart it appears that fewer loci harbor methylation, pointing to differences between male and female breast carcinogenesis with regard to the studied loci.

Promoter Methylation Status of the Retinoic Acid Receptor-Beta 2 Gene in Breast Cancer Patients: A Case Control Study and Systematic Review

Background

We aimed to determine the promoter methylation status of the retinoic acid receptor-beta 2 (RARβ2) gene among breast cancer patients and to review relevant studies in this field in various populations.

Methods

We analyzed 400 samples which comprised blood specimens from 102 breast cancer patients, 102 first-degree female relatives of patients, 100 cancer-free females, 48 breast cancer tissues, and 48 adjacent normal breast tissues from the same patients. The RARβ2 methylation status was determined using methylation-specific polymerase chain reaction (MSP) and DNA sequencing methods.

Results

The presence of combined partially methylated (MU) and fully methylated (MM) forms of the RARβ2 gene (MU+MM) in the blood of patients was associated with susceptibility to breast cancer (odds ratio = 4.7, p = 0.05). A significantly higher frequency of the MM genotype was observed in cancer tissue (10.4%) compared to matched adjacent normal breast tissue (0%) (p = 0.02).

Conclusion

We found a higher frequency of RARβ2 gene methylation in the blood and cancer tissues of patients compared to the blood of controls and adjacent normal breast tissues. The survey of studies on various populations demonstrated a higher RARβ2 methylation frequency in breast cancer patients compared to normal individuals, and many reports suggest a significant association between hypermethylation of the gene and susceptibility to breast cancer.

Active and secondhand smoke exposure throughout life and DNA methylation in breast tumors

PURPOSE

Tobacco smoke exposure has been associated with altered DNA methylation. However, there is a paucity of information regarding tobacco smoke exposure and DNA methylation of breast tumors.

METHODS

We conducted a case-only analysis using breast tumor tissue from 493 postmenopausal and 225 premenopausal cases in the Western New York Exposures and Breast Cancer (WEB) study. Methylation of nine genes (SFN, SCGB3A1, RARB, GSTP1, CDKN2A, CCND2, BRCA1, FHIT, and SYK) was measured with pyrosequencing. Participants reported their secondhand smoke (SHS) and active smoking exposure for seven time periods. Unconditional logistic regression was used to estimate odds ratios (OR) of having methylation higher than the median.

RESULTS

SHS exposure was associated with tumor DNA methylation among postmenopausal but not premenopausal women. Active smoking at certain ages was associated with increased methylation of GSTP1, FHIT, and CDKN2A and decreased methylation of SCGB3A1 and BRCA1 among both pre- and postmenopausal women.

CONCLUSION

Exposure to tobacco smoke may contribute to breast carcinogenesis via alterations in DNA methylation. Further studies in a larger panel of genes are warranted.

Promoter hypermethylation of RARβ2, DAPK, hMLH1, p14, and p15 is associated with progression of breast cancer: A PRISMA-compliant meta-analysis

BACKGROUND

Numerous studies have investigated the associations between RARβ2, DAPK, hMLH1, p14, and p15 promoter hypermethylation and clinical progression of patients with breast cancer, however the results remained uncertain due to the small sample size. Therefore, we performed a meta-analysis to explore the role of RARβ2, DAPK, hMLH1, p14, and p15 promoter hypermethylation in the susceptibility and clinical progression of breast cancer.

METHODS

Eligible studies were obtained by searching Medicine, Embase, Web of knowledge, and Chinese National Knowledge Infrastructure (CNKI) databases. The odds ratios (OR) and 95% confidence intervals (CI) were calculated to evaluate the associations of RARβ2, DAPK, hMLH1, p14, and p15 promoter hypermethylation with breast cancer pathogenesis. Trial sequential analysis (TSA) was applied to observe the reliability of pooled results of RARβ2 gene, and obtain a conservative required information size (RIS).

RESULTS

In primary screened 445 articles, 39 literatures with 4492 breast cancer patients were finally enrolled in the final meta-analysis. The results indicated that the frequency of RARβ2 promoter hypermethylation in case group was significantly higher than the frequency of control group (OR = 7.21, 95% CI = 1.54-33.80, P < .05). The RARβ2 promoter hypermethylation had a significant association with lymph node metastasis of breast cancer (OR = 2.13, 95% CI = 1.04-4.47, P < .05). And, the RARβ2 promoter hypermethylation was more common in the breast cancer patients of TNM III-IV stage than those patients of TNM I-II stage (OR = 1.85, 95% CI = 1.33-2.57, P < .05). In addition, the promoter hypermethylation of DAPK, hMLH1, and p14 genes were significantly associated with the susceptibility of breast cancer (for DAPK, OR = 4.93, 95% CI = 3.17-7.65; for hMLH1, OR = 1.84, 95% CI = 1.26-1.29; for p14, OR = 22.52, 95% CI = 7.00-72.41; for p15, OR = 2.13, 95% CI = 0.30-15.07).

CONCLUSIONS

Our findings revealed that the RARβ2 promoter hypermethylation significantly increased the risk of breast cancer. In the meantime, the meta-analysis demonstrated that there were significant associations of RARβ2 promoter hypermethylation with lymph node metastasis and TNM-stage of breast cancer patients. In addition, DAPK, hMLH1, and p14 genes promoter hypermethylation were significantly associated with the susceptibility of breast cancer.

EBV Associated Breast Cancer Whole Methylome Analysis Reveals Viral and Developmental Enriched Pathways

Background: Breast cancer (BC) ranks among the most common cancers in Sudan and worldwide with hefty toll on female health and human resources. Recent studies have uncovered a common BC signature characterized by low frequency of oncogenic mutations and high frequency of epigenetic silencing of major BC tumor suppressor genes. Therefore, we conducted a pilot genome-wide methylome study to characterize aberrant DNA methylation in breast cancer.

Results: Differential methylation analysis between primary tumor samples and normal samples from healthy adjacent tissues yielded 20,188 differentially methylated positions (DMPs), which is further divided into 13,633 hypermethylated sites corresponding to 5339 genes and 6,555 hypomethylated sites corresponding to 2811 genes. Moreover, bioinformatics analysis revealed epigenetic dysregulation of major developmental pathways including hippo signaling pathway. We also uncovered many clues to a possible role for EBV infection in BC.

Conclusion: Our results clearly show the utility of epigenetic assays in interrogating breast cancer tumorigenesis, and pinpointing specific developmental and viral pathways dysregulation that might serve as potential biomarkers or targets for therapeutic interventions.

Epigenomic and Transcriptomic Characterization of Secondary Breast Cancers

BACKGROUND

Molecular alterations impact tumor prognosis and response to treatment. This study was designed to identify transcriptomic and epigenomic signatures of breast cancer (BC) tumors from patients with any prior malignancy.

METHODS

RNA-sequencing and genome-wide DNA methylation profiles from BCs were generated in the Cancer Genome Atlas project. Patients with secondary breast cancer (SBC) were separated by histological subtype and matched to primary breast cancer controls to create two independent cohorts of invasive ductal (IDC, n = 36) and invasive lobular (ILC, n = 40) carcinoma. Differentially expressed genes, as well as differentially methylated genomic regions, were integrated to identify epigenetically regulated abnormal gene pathways in SBCs.

RESULTS

Differentially expressed genes were identified in IDC SBCs (n = 727) and in ILC SBCs (n = 261; Wilcoxon's test; P < 0.05). In IDC SBCs, 105 genes were upregulated and hypomethylated, including an estrogen receptor gene, and 73 genes were downregulated and hypermethylated, including genes involved in antigen presentation and interferon response pathways (HLA-E, IRF8, and RELA). In ILC SBCs, however, only 17 genes were synchronously hypomethylated and upregulated, whereas 46 genes hypermethylated and downregulated. Interestingly, the SBC gene expression signatures closely corresponded with each histological subtype with only 1.51% of genes overlapping between the two histological subtypes.

CONCLUSIONS

Differential gene expression and DNA methylation signatures are seen in both IDC and ILC SBCs, including genes that are relevant to tumor growth and proliferation. Differences in gene expression signatures corresponding with each histological subtype emphasize the importance of disease subtype-specific evaluations of molecular alterations.

Lifetime exposure to ambient air pollution and methylation of tumor suppressor genes in breast tumors

BACKGROUND

We previously reported increased risk of breast cancer associated with early life exposure to two measures of air pollution exposure, total suspended particulates (TSP) and traffic emissions (TE), possible proxies for exposure to polycyclic aromatic hydrocarbons (PAHs). Exposure to PAHs has been shown to be associated with aberrant patterns of DNA methylation in peripheral blood of healthy individuals. Exposure to PAHs and methylation in breast tumor tissue has received little attention. We examined the association of early life exposure to TSP and TE with patterns of DNA methylation in breast tumors.

METHODS

We conducted a study of women enrolled in the Western New York Exposures and Breast Cancer (WEB) Study. Methylation of nine genes (SFN, SCGB3A1, RARB, GSTP1, CDKN2A CCND2, BRCA1, FHIT, and SYK) was assessed using bisulfite-based pyrosequencing. TSP exposure at each woman's home address at birth, menarche, and when she had her first child was estimated. TE exposure was modeled for each woman's residence at menarche, her first birth, and twenty and ten years prior to diagnosis. Unconditional logistic regression was employed to estimate odds ratios (OR) of having methylation greater than the median value, adjusting for age, secondhand smoke exposure before age 20, current smoking status, and estrogen receptor status.

RESULTS

Exposure to higher TSP at a woman's first birth was associated with lower methylation of SCGB3A1 (OR = 0.48, 95% CI: 0.23-0.99) and higher methylation of SYK (OR = 1.86, 95% CI: 1.03-3.35). TE at menarche was associated with increased methylation of SYK (OR = 2.37, 95% CI: 1.05-5.33). TE at first birth and ten years prior to diagnosis was associated with decreased methylation of CCND2 (OR ten years prior to diagnosis=0.48, 95% CI: 0.26-0.89). Although these associations were nominally significant, none were significant after adjustment for multiple comparisons (p < 0.01).

CONCLUSIONS

We observed suggestive evidence that exposure to ambient air pollution throughout life, measured as TSP and TE, may be associated with DNA methylation of some tumor suppressor genes in breast tumor tissue. Future studies with a larger sample size that assess methylation of more sites are warranted.

TP73 DNA methylation and upregulation of ΔNp73 are associated with an adverse prognosis in breast cancer

AIM

Accumulated evidence suggests that aberrant methylation of the TP73 gene and increased levels of ΔNp73 in primary tumours correlate with poor prognosis. However, little is known regarding the transcriptional and functional regulation of the TP73 gene in breast cancer. The aim of the present study was to determine the expression of the ΔNp73 isoform, its relationship with DNA methylation of TP73 and their clinical prognostic significance in breast cancer patients.

METHODS

TP73 gene methylation was studied in TCGA datasets and in 70 invasive ductal breast carcinomas (IDCs). The expression of p73 isoforms was evaluated by immunohistochemistry (IHC) and Western blot and correlated with clinicopathological variables and clinical outcome.

RESULTS

We observed that the methylation of diverse CpG islands of TP73 differed significantly between molecular subtypes. An inverse correlation was found between p73 protein expression and the methylation status of the TP73 gene. The expression of exon 3' of p73 (only expressed in ΔNp73) was significantly higher in patients with wild-type p53. Immunohistochemical analysis revealed that all p73 isoforms were localised in both the nuclear and cytoplasmic compartments. We confirmed a positive association between the expression of ∆Np73 and high histological grade.

CONCLUSIONS

Our findings suggest that high expression of ΔNp73 could be used to determine the aggressiveness of IDCs and could be incorporated in the pathologist's report.

Asymmetric Cancer Hallmarks in Breast Tumors on Different Sides of the Body

During the last decades it has been established that breast cancer arises through the accumulation of genetic and epigenetic alterations in different cancer related genes. These alterations confer the tumor oncogenic abilities, which can be resumed as cancer hallmarks (CH). The purpose of this study was to establish the methylation profile of CpG sites located in cancer genes in breast tumors so as to infer their potential impact on 6 CH: i.e. sustained proliferative signaling, evasion of growth suppressors, resistance to cell death, induction of angiogenesis, genome instability and invasion and metastasis. For 51 breast carcinomas, MS-MLPA derived-methylation profiles of 81 CpG sites were converted into 6 CH profiles. CH profiles distribution was tested by different statistical methods and correlated with clinical-pathological data. Unsupervised Hierarchical Cluster Analysis revealed that CH profiles segregate in two main groups (bootstrapping 90–100%), which correlate with breast laterality (p = 0.05). For validating these observations, gene expression data was obtained by RealTime-PCR in a different cohort of 25 tumors and converted into CH profiles. This analyses confirmed the same clustering and a tendency of association with breast laterality (p = 0.15). In silico analyses on gene expression data from TCGA Breast dataset from left and right breast tumors showed that they differed significantly when data was previously converted into CH profiles (p = 0.033). We show here for the first time, that breast carcinomas arising on different sides of the body present differential cancer traits inferred from methylation and expression profiles. Our results indicate that by converting methylation or expression profiles in terms of Cancer Hallmarks, it would allow to uncover veiled associations with clinical features. These results contribute with a new finding to the better understanding of breast tumor behavior, and can moreover serve as proof of principle for other bilateral cancers like lung, testes or kidney.

DNA methylation and breast tumor clinicopathological features: The Western New York Exposures and Breast Cancer (WEB) study

We evaluated the association between methylation of 9 genes, SCGB3A1, GSTP1, RARB, SYK, FHIT, CDKN2A, CCND2, BRCA1, and SFN in tumor samples from 720 breast cancer cases with clinicopathological features of the tumors and survival. Logistic regression was used to estimate odds ratios (OR) of methylation and Cox proportional hazards models to estimate hazard ratios (HR) between methylation and breast cancer related mortality. Estrogen receptor (ER) and progesterone receptor (PR) positivity were associated with increased SCGB3A1 methylation among pre- and post-menopausal cases. Among premenopausal women, compared with Stage 0 cases, cases of invasive cancer were more likely to have increased methylation of RARB (Stage I OR = 4.7, 95% CI: 1.1-19.0; Stage IIA/IIB OR = 9.7, 95% CI: 2.4-39.9; Stage III/IV OR = 5.6, 95% CI: 1.1-29.4) and lower methylation of FHIT (Stage I OR = 0.2, 95% CI: 0.1-0.9; Stage IIA/IIB OR = 0.2, 95% CI: 0.1-0.8; Stage III/IV OR = 0.6, 95% CI: 0.1-3.4). Among postmenopausal women, methylation of SYK was associated with increased tumor size (OR = 1.7, 95% CI: 1.0-2.7) and higher nuclear grade (OR = 2.0, 95% CI 1.2-3.6). Associations between methylation and breast cancer related mortality were observed among pre- but not post-menopausal women. Methylation of SCGB3A1 was associated with reduced risk of death from breast cancer (HR = 0.41, 95% CI: 0.17-0.99) as was BRCA1 (HR = 0.41, 95% CI: 0.16-0.97). CCND2 methylation was associated with increased risk of breast cancer mortality (HR = 3.4, 95% CI: 1.1-10.5). We observed differences in methylation associated with tumor characteristics; methylation of these genes was also associated with breast cancer survival among premenopausal cases. Understanding of the associations of DNA methylation with other clinicopathological features may have implications for prevention and treatment.

The potential of identification of a malignancy-associated biomarker in breast cancer diagnosis and research: hTERT gene DNA methylation

BACKGROUND

DNA hypermethylation has been documented to be prominent at a CpG island rich region about 600 bp upstream the transcription start site of the hTERT gene using qualitative methylation specific PCR on DNA isolated from tumor cell lines. In order to assess the potential significance of this biomarker in breast cancer research and diagnosis, we explored if such findings are reproducible on surgically resected fresh breast tumor cells.

METHODS

Using quantitative pyrosequencing technology, we investigated and present methylation status of four CpG islands of this region in a cohort of 77 invasive breast carcinomas using normal breast tissue as controls.

RESULTS

Globally, a significant hypermethylation in tumor cells was observed in the four CpG islands as a sum, in comparison to methylation of the normal breast tissue. Individually, certain CpG islands displayed methylation greater than 50% in about 3/4 of the 77 breast cancers, but in none of the normal breast tissue. Our results highlight the value of DNA hypermethylation in the -600 bp region of the hTERT gene as a potential marker for breast cancer diagnosis.

CONCLUSIONS

We believe that integration of this novel, malignancy-associated molecular testing with morphology is of significant value in the accurate interpretation of small tumor sample size obtained via fine needle aspiration biopsy, ductal lavage, and nipple fluid aspirates both in clinical practice and in breast cancer research. Diagn. Cytopathol. 2016;44:670-675. © 2016 Wiley Periodicals, Inc.

DNA methylation assessment as a prognostic factor in invasive breast cancer using methylation-specific multiplex ligation dependent probe amplification

DNA methylation of promoter regions is a common molecular mechanism for inactivation of tumor suppressor genes that participates in carcinogenesis. Determining the methylation status of genes in cancer and their association with clinical features play an essential role in early diagnosis, prognosis and determine appropriate treatment for patients. The purpose of the present study was to evaluate the methylation of tumor suppressor genes in patients with invasive ductal carcinoma (IDC). Furthermore, we evaluated the association between clinical parameters and DNA methylation as a biomarker in diagnostic IDC patients. The methylation-specific multiplex ligation dependent probe amplification (MS-MLPA) assay was used to analyze the methylation profile of 24 genes in formalin-fixed paraffin embedded (FFPE) tissue samples from 75 patients with IDC. Each of the patients showed a distinctive methylation profile. We observed higher methylation in the RASSF1 (48 %), CDH13 (44 %) and GSTP1 (36 %) genes. Some of the methylated genes were associated with clinical features. Methylation of GSTP1 (P=0.028) and RASSF1 (P=0.012) were related with lymph node metastasis. Methylation of GSTP1 (P=0.005) was associated with high histological grade. Moreover, concurrent methylation of GSTP1 and CDH13 was observed in IDC patients (p<0.001). Hierarchical cluster analysis based on the methylation profile revealed two main clusters of patients, the highly methylated cluster being significantly associated with high histological grade and lymph node metastasis. The results of this study indicate that the methylation status of RASSF1 and CDH13 and GSTP1 can be a prognostic marker to better management of IDC patients.

Inhibitory effect of isoamericanol A from Jatropha curcas seeds on the growth of MCF-7 human breast cancer cell line by G2/M cell cycle arrest

Although various parts of J. curcas (Jatropha curcas L., Euphorbiaceae) have long been used as traditional folk medicines for their antiviral, analgesic, and/or antidotal efficacies, we are the first to investigate the role of anti-carcinogenicity of isoamericanol A (IAA) from the seed extract. Our results showed that IAA is capable of inhibiting cell proliferation in a dose-dependent manner on the human cancer cell lines of MCF-7, MDA-MB231, HuH-7, and HeLa. Flow cytometry analysis showed IAA significantly induces cell cycle arrest at G2/M on MCF-7 cells. At both protein and mRNA levels examined by western blot and real-time PCR, the results revealed increased expression of BTG2 (B-cell translocation gene 2), p21 (p21^WAF1/CIPI), and GADD45A (growth arrest and DNA-damage-inducible, alpha) after IAA treatment, but inversed expression in CDK1 (cyclin-dependent kinase 1) and cyclins B1 and B2. All these effects contribute to G2/M cell cycle arrest. Furthermore, these results coincide with the changes in molecular expressions determined by DNA-microarray analysis. Our findings indicate that IAA has an inhibitory effect on cell proliferation of MCF-7 through cell cycle arrest, giving it great potential as a future therapeutic reagent for cancers.

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.

Emerging technologies for studying DNA methylation for the molecular diagnosis of cancer

DNA methylation is an epigenetic mechanism that plays a key role in regulating gene expression and other functions. Although this modification is seen in different sequence contexts, the most frequently detected DNA methylation in mammals involves cytosine-guanine dinucleotides. Pathological alterations in DNA methylation patterns are described in a variety of human diseases, including cancer. Unlike genetic changes, DNA methylation is heavily influenced by subtle modifications in the cellular microenvironment. In all cancers, aberrant DNA methylation is involved in the alteration of a large number of oncological pathways with relevant theranostic utility. Several technologies for DNA methylation mapping have been developed recently and successfully applied in cancer studies. The scope of these technologies varies from assessing a single cytosine-guanine locus to genome-wide distribution of DNA methylation. Here, we review the strengths and weaknesses of these approaches in the context of clinical utility for the molecular diagnosis of human cancers.

Epigenetic variations in breast cancer progression to lymph node metastasis

Breast cancer is a heterogeneous disease characterized by the accumulation of genetic and epigenetic alterations that contribute to the development of regional and distant metastases. Lymph node metastasis (LNM) status is the single most important prognostic factor. Metastatic cancer cells share common molecular alterations with those of the primary tumor, but in addition, they develop distinct changes that allow the cancer to progress. There is an urgent need for molecular studies which focus on identifying genomic and epigenomic markers that can predict the progression to metastasis. The objective of this study was to identify epigenetic similarities and differences between paired primary breast tumor (PBT) and LNM. We employed Methylation-Specific-MLPA (Multiplex ligation-dependent probe amplification) to assess the methylation status of 33 cancer-related genes in a cohort of 50 paired PBT and LNM specimens. We found that the methylation index, which represents the degree of aberrantly methylated genes in a specimen, was maintained during the progression to LNM. However, some genes presented differential methylation profiles. Interestingly, PAX6 presented a significant negative correlation between paired PBT and LNM (p = 0.03), which indicated a switch from methylated to unmethylated status in the progression from PBT to LNM. We further identified that the methylation status of PAX6 on the identified CpG site functionally affected the expression of PAX6 at the mRNA level. Our study unraveled significant epigenetic changes during the progression from PBT to LNM, which may contribute to improved prognosis, prediction and therapeutic management of metastatic breast cancer patients.

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.

Retinoic acid reduces migration of human breast cancer cells: role of retinoic acid receptor beta

Breast cancer is the most common malignancy in women and the appearance of distant metastases produces the death in 98% of cases. The retinoic acid receptor β (RARβ) is not expressed in 50% of invasive breast carcinoma compared with normal tissue and it has been associated with lymph node metastasis. Our hypothesis is that RARβ protein participates in the metastatic process. T47D and MCF7 breast cancer cell lines were used to perform viability assay, immunobloting, migration assays, RNA interference and immunofluorescence. Administration of retinoic acid (RA) in breast cancer cells induced RARβ gene expression that was greatest after 72 hrs with a concentration 1 μM. High concentrations of RA increased the expression of RARβ causing an inhibition of the 60% in cell migration and significantly decreased the expression of migration-related proteins [moesin, c-Src and focal adhesion kinase (FAK)]. The treatment with RARα and RARγ agonists did not affect the cell migration. On the contrary, the addition of the selective retinoid RARβ-agonist (BMS453) significantly reduced cell migration comparable to RA inhibition. When RARβ gene silencing was performed, the RA failed to significantly inhibit migration and resulted ineffective to reduce moesin, c-Src and FAK expressions. RARβ is necessary to inhibit migration induced by RA in breast cancer cells modulating the expression of proteins involved in cell migration.

Comparison of methylation profiling in cancerous and their corresponding normal tissues from korean patients with breast cancer

BACKGROUND

Aberrant DNA hypermethylation plays a pivotal role in carcinogenesis and disease progression; therefore, accurate measurement of differential gene methylation patterns among many genes is likely to reveal biomarkers for improved risk assessment. We evaluated the gene hypermethylation profiles of primary breast tumors and their corresponding normal tissues and investigated the association between major clinicopathological features and gene hypermethylation.

METHODS

A single reaction using methylation-specific multiplex ligation-dependent probe amplification was used to analyze the DNA methylation status of 24 tumor suppressor genes in 60 cancerous tissues and their corresponding normal tissues from patients with primary breast cancer.

RESULTS

In cancerous breast tissues, 21 of 24 genes displayed promoter methylation in one or more samples. The most frequently methylated genes included RASSF1 (43.3%), APC (31.7%), CDKN2B (25.0%), CDH13 (23.3%), GSTP1 (16.7%), and BRCA1 (10%). APC was associated with lymph node metastasis, and BRCA1 was associated with negative estrogen receptor and negative progesterone receptor expression. In normal breast tissues, 8 of 24 tumor suppressor genes displayed promoter hypermethylation; CDKN2B (28.3%) and RASSF1 (8.3%) hypermethylation were most frequently observed.

CONCLUSIONS

RASSF1 and CDKN2B hypermethylation in Korean breast cancer patients were the most frequent in cancerous tissue and corresponding normal tissue, respectively. Our data indicates that methylation of specific genes is a frequent event in morphologically normal breast tissues adjacent to breast tumors as well as the corresponding breast cancers. This study also suggests that gene methylation is linked to various pathological features of breast cancer; however, this requires confirmation in a larger study.