Promoter hypermethylation of TMS1, BRCA1, ERalpha and PRB in serum and tumor DNA of invasive ductal breast carcinoma patients

DNA methylation and histone modifications in breast cancer

Breast cancer is caused by progressive genetic alterations and epigenetic changes that trigger tumor development. Among the epigenetic alterations descried in breast cancer, DNA promoter methylation has been extensively studied and observed in genes involved in several critical signaling pathways that initiate and promote breast tumorigenesis. In addition to DNA hypermethylation, global methylation levels have been observed to decrease with breast cancer progression. In close connection with DNA methylation changes, histone modifications, especially the acetylation and methylation of histone lysines, play an essential role in the nucleosomes remodeling and gene expression regulation in breast cancer.

DNA methylation in pre-diagnostic serum samples of breast cancer cases: results of a nested case-control study

BACKGROUND

Promoter methylation of tumor suppressor genes is a frequent and early event in breast carcinogenesis. Paired tumor tissue and serum samples from women with breast cancer show that promoter methylation is detectable in both sample types, with good concordance. This suggests the potential for these serum markers to be used for breast cancer detection.

METHODS

The current study was a case-control study nested within the prospective New York University Women's Health Study cohort aimed to assess the ability of promoter methylation in serum to detect pre-clinical disease. Cases were women with blood samples collected within the 6 months preceding breast cancer diagnosis (n=50). Each case was matched to 2 healthy cancer-free controls and 1 cancer-free control with a history of benign breast disease (BBD).

RESULTS

Promoter methylation analysis of four cancer-related genes: -RASSF1A, GSTP1, APC and RARβ2, - was conducted using quantitative methylation-specific PCR. Results showed that the frequency of methylation was lower than expected among cases and higher than expected among controls. Methylation was detected in the promoter region of: RASSF1A in 22.0%, 22.9% and 17.2% of cases, BBD controls and healthy controls respectively; GSTP1 in 4%, 10.4% and 7.1% respectively; APC in 2.0%, 4.4% and 4.2% respectively and RARβ2 in 6.7%, 2.3% and 1.1% respectively.

CONCLUSION

Methylation status of the four genes included in this study was unable to distinguish between cases and either control group. This study highlights some methodological issues to be addressed in planning prospective studies to evaluate methylation markers as diagnostic biomarkers.

Promoter methylation status and expression of estrogen receptor alpha in familial breast cancer patients

The hypermethylation of estrogen receptor alpha (ERα) promoter is a common molecular alteration in sporadic breast cancer (BC), but its involvement in familial BC remains largely unknown. In the present study, we analyzed the methylation statuses of four regions (ER1, ER3, ER4, and ER5) of the ERα promoter and the ERα expression levels of 113 familial BC patients in a Han Chinese Population from northeastern China and evaluated the association between major clinicopathological features and the hypermethylation statuses of the ERα gene. Tumor samples were analyzed for ERα methylation status by the methylation-specific polymerase chain reaction for ERα, PR, p53, BRCA-1, and BRCA-2 by immunohistochemical (IHC) staining and for Her-2 status by IHC and fluorescence in situ hybridization (FISH). ERα methylation was observed in tumor tissues in 47/113 (41.6%) familial BC patients. There were no significant differences in the methylation statuses among ER1 (20.4%), ER3 (18.6%), ER4 (17.7%), and ER5 (19.5%; χ (2) = 3.89, p > 0.05). An association between ERα expression level and its promoter methylation level was found. In addition, ERα methylation was significantly correlated with tumor size, PR expression, p53 nuclear accumulation, and BRCA-1 and BRCA-2 statuses. In conclusion, in familial BC patients, the level of ERα gene promoter methylation correlates with ERα expression, PR, p53 nuclear accumulation, and BRCA-1 and BRCA-2 statuses. Epigenetic alteration of ERα gene may play an important role in the pathogenesis of familial BC.

Hypoxia-induced epigenetic regulation and silencing of the BRCA1 promoter

Disruption of the BRCA1 tumor suppressor can be caused not only by inherited mutations in familial cancers but also by BRCA1 gene silencing in sporadic cancers. Hypoxia, a key feature of the tumor microenvironment, has been shown to downregulate BRCA1 at the transcriptional level via repressive E2F4/p130 complexes. Here we showed that hypoxia also drives epigenetic modification of the BRCA1 promoter, with decreased H3K4 methylation as a key repressive modification produced by the lysine-specific histone demethylase LSD1. We also observed increased H3K9 methylation coupled with decreased H3K9 acetylation. Similar modifications were seen in the RAD51 promoter, which is also downregulated by hypoxia, whereas exactly opposite changes were seen in the promoter of the hypoxia-inducible gene VEGF. In cells containing the BRCA1 promoter driving a selectable HPRT gene, long-term silencing of the promoter was observed following exposure to hypoxic stress. Clones with silenced BRCA1 promoters were detected at frequencies of 2% or more following hypoxia, but at less than 6 × 10(-5) without hypoxia. The silenced clones showed decreased H3K4 methylation and decreased H3K9 acetylation in the BRCA1 promoters, consistent with the acute effects of hypoxic stress. Hypoxia-induced BRCA1 promoter silencing persisted in subsequent normoxic conditions but could be reversed by treatment with a histone deacetylase (HDAC) inhibitor but not with a DNA methylation inhibitor. Interestingly, treatment of cells with inhibitors of poly(ADP-ribose) polymerase (PARP) can cause short-term repression of BRCA1 expression, but such treatment does not produce H3K4 or H3K9 histone modification or BRCA1 promoter silencing. These results suggest that hypoxia is a driving force for long-term silencing of BRCA1, thereby promoting genome instability and tumor progression.

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.

Progesterone receptor isoform-specific promoter methylation: association of PRA promoter methylation with worse outcome in breast cancer patients

PURPOSE

ERα and PR levels are critical determinants for breast cancer prognosis and response to endocrine therapy. Although PR is known to be silenced by methylation of its promoter, few studies have correlated methylation with PR levels and outcome in breast cancer. There is only one previous small study comparing methylation of the two PR isoforms, PRA and PRB, which are expressed from different promoters, and finally, there is no prior knowledge of associations between isoform-specific methylation and outcome.

EXPERIMENTAL DESIGN

We conducted a cohort-based study to test for associations between PRA and PRB methylation, expression, and clinical outcome in tamoxifen-treated patients (n = 500), and in patients who underwent surgery only (n = 500). Methylation and PR levels were measured by bisulfite pyrosequencing and ligand-binding assay, respectively.

RESULTS

Low PR levels were significantly associated with worse outcome in all patients. PRA and PRB promoters were methylated in 9.6% and 14.1% of the breast tumors, respectively. The majority (74%) of PR-negative tumors were not methylated despite the significant inverse correlation of methylation and PR levels. PRA methylation was significantly associated with PRB methylation, although a subset of tumors had PRA only (3.9%) or PRB only (8.3%) methylated. Methylation of PRA, but not PRB was significantly associated with worse outcome in the tamoxifen-treated group.

CONCLUSIONS

Mechanisms other than promoter methylation may be more dominant for loss of PR. Isoform-specific methylation events suggest independent regulation of PRA and PRB. Finally, this article shows for the first time that PRA methylation plays a unique role in tamoxifen-resistant breast cancer.

In silico analysis and DHPLC screening strategy identifies novel apoptotic gene targets of aberrant promoter hypermethylation in prostate cancer

BACKGROUND

Aberrant DNA methylation has been implicated as a key survival mechanism in cancer, whereby promoter hypermethylation silences genes essential for many cellular processes including apoptosis. Limited data is available on the methylation profile of apoptotic genes in prostate cancer (CaP). The aim of this study was to profile methylation of apoptotic-related genes in CaP using denaturing high performance liquid chromatography (DHPLC).

METHODS

Based on an in silico selection process, 13 genes were screened for methylation in CaP cell lines using DHPLC. Quantitative methylation specific PCR was employed to determine methylation levels in prostate tissue specimens (n = 135), representing tumor, histologically benign prostate, high-grade prostatic intraepithelial neoplasia and benign prostatic hyperplasia. Gene expression was measured by QRT-PCR in cell lines and tissue specimens.

RESULTS

The promoters of BIK, BNIP3, cFLIP, TMS1, DCR1, DCR2, and CDKN2A appeared fully or partially methylated in a number of malignant cell lines. This is the first report of aberrant methylation of BIK, BNIP3, and cFLIP in CaP. Quantitative methylation analysis in prostate tissues identified 5 genes (BNIP3, CDKN2A, DCR1, DCR2 and TMS1) which were frequently methylated in tumors but were unmethylated in 100% of benign tissues. Furthermore, 69% of tumors were methylated in at least one of the five-gene panel. In the case of all genes, except BNIP3, promoter hypermethylation was associated with concurrent downregulation of gene expression.

CONCLUSION

Future examination of this "CaP apoptotic methylation signature" in a larger cohort of patients is justified to further evaluate its value as a diagnostic and prognostic marker.

Quantitative analysis of promoter methylation in exfoliated epithelial cells isolated from breast milk of healthy women

Promoter methylation analysis of genes frequently silenced in breast cancer is a promising indicator of breast cancer risk, as these methylation events are thought to occur long before presentation of disease. The numerous exfoliated epithelial cells present in breast milk may provide the breast epithelial DNA needed for detailed methylation analysis and assessment of breast cancer risk. Fresh breast milk samples and health, lifestyle, and reproductive history questionnaires were collected from 111 women. Pyrosequencing analysis was conducted on DNA isolated from the exfoliated epithelial cells immunomagnetically separated from the total cell population in the breast milk of 102 women. A total of 65 CpG sites were examined in six tumor suppressor genes: PYCARD (also known as ASC or TMS1), CDH1, GSTP1, RBP1 (also known as CRBP1), SFRP1, and RASSF1. A sufficient quantity of DNA was obtained for meaningful analysis of promoter methylation; women donated an average of 86 ml of milk with a mean yield of 32,700 epithelial cells per ml. Methylation scores were in general low as expected of benign tissue, but analysis of outlier methylation scores revealed a significant relationship between breast cancer risk, as indicated by previous biopsy, and methylation score for several CpG sites in CDH1, GSTP1, SFRP1, and RBP1. Methylation of RASSF1 was positively correlated with women's age irrespective of her reproductive history. Promoter methylation patterns in DNA from breast milk epithelial cells can likely be used to assess breast cancer risk. Additional studies of women at high breast cancer risk are warranted.

BRCA1 promoter methylation in peripheral blood cells is associated with increased risk of breast cancer with BRCA1 promoter methylation

BRCA1 promoter methylation reportedly plays an important part in the pathogenesis of human breast cancer. In the present study, we investigated whether or not BRCA1 promoter methylation in peripheral blood cells (PBCs) can serve as a risk factor for developing breast cancer. The association of BRCA1 promoter methylation in PBCs with breast cancer risk was examined in a case-control study (200 breast cancer patients and 200 controls). BRCA1 promoter methylation in PBCs and breast tumors was determined with a methylation-specific quantitative PCR assay. BRCA1 promoter methylation in PBCs was seen in 43 (21.5%) of the breast cancer patients and in 27 (13.5%) of the controls. The odds ratio for breast cancer adjusted for other epidemiological risk factors was 1.73 (1.01-2.96) and was statistically significant (P = 0.045). When breast tumors were classified into those with and without BRCA1 promoter methylation, the odds ratio was 0.84 (0.43-1.64) (P = 0.61) for BRCA1 promoter methylation-negative and 17.78 (6.71-47.13) (P < 0.001) for BRCA1 promoter methylation-positive breast tumors. BRCA1 promoter methylation in PBCs is significantly associated with risk of breast cancer with BRCA1 promoter methylation. This seems to indicate that BRCA1 promoter methylation in PBCs may constitute a novel risk factor for breast cancer with BRCA1 promoter methylation.

Cell-free DNA in the blood as a solid tumor biomarker--a critical appraisal of the literature

Circulating cell-free DNA (cfDNA) has been suggested as a cancer biomarker. Several studies assessed the usefulness of quantitative and qualitative tumor-specific alterations of cfDNA, such as DNA strand integrity, frequency of mutations, abnormalities of microsatellites, and methylation of genes, as diagnostic, prognostic, and monitoring markers in cancer patients. Most of the papers that could be evaluated in this review resulted in a positive conclusion. However, methodical diversity without the traceability of data and differently designed and often underpowered studies resulted in divergent results between studies. In addition, the limited diagnostic sensitivity and specificity of cfDNA alterations temper the effusive hope of novel tumor markers, raising similar issues as those for other tumor markers. To validate the actual clinical validity of various cfDNA alterations as potential cancer biomarkers in practice for individual tumor types, the main problems of the observed uncertainties must be considered in future studies. These include methodical harmonization concerning sample collection, processing, and analysis with the traceability of measurement results as well as the realization of well-designed prospective studies based on power analysis and sample size calculations.

Improving early breast cancer detection: focus on methylation

The need for additional breast cancer screening tools is indisputably high, as one may conclude from the high rate of interval malignancies in women undergoing regular screening. DNA promoter methylation frequently occurs during breast carcinogenesis and is an early event in this process. Moreover, a field defect for methylation has been described and methylation values can reliably be assessed in limited amounts of DNA. Simultaneous detection of methylation of a panel of genes in breast fluids and/or blood derivatives could be both sufficiently specific and sensitive to be of additive value to current imaging-based screening methods. This review describes the recent developments in methylation detection in breast fluids, serum and plasma that paved the way for large prospective studies. These studies will provide us with the definite answer as to what will be the additive value of defining the methylation status of specific genes to current imaging-based screening methods.

Overexpression of CDC25B, CDC25C and phospho-CDC25C (Ser216) in vulvar squamous cell carcinomas are associated with malignant features and aggressive cancer phenotypes

BACKGROUND

CDC25 phosphatases are important regulators of the cell cycle. Their abnormal expression detected in a number of tumors implies that their dysregulation is involved in malignant transformation. However, the role of CDC25s in vulvar cancer is still unknown. To shed light on their roles in the pathogenesis and to clarify their prognostic values, expression of CDC25A, CDC25B and CDC25C in a large series of vulvar squamous cell carcinomas were examined.

METHODS

Expression of CDC25A, CDC25B, CDC25C and phosphorylated (phospho)-CDC25C (Ser216) were examined in 300 vulvar carcinomas using immunohistochemistry. Western blot analysis was utilized to demonstrate CDC25s expression in vulvar cancer cell lines. Kinase and phosphatase assays were performed to exclude cross reactivity among CDC25s isoform antibodies.

RESULTS

High nuclear CDC25A and CDC25B expression were observed in 51% and 16% of the vulvar carcinomas, respectively, whereas high cytoplasmic CDC25C expression was seen in 63% of the cases. In cytoplasm, nucleus and cytoplasm/nucleus high phospho-CDC25C (Ser216) expression was identified in 50%, 70% and 77% of the carcinomas, respectively. High expression of CDC25s correlated significantly with malignant features, including poor differentiation and infiltration of vessel for CDC25B, high FIGO stage, presence of lymph node metastases, large tumor diameter, poor differentiation for CDC25C and high FIGO stage, large tumor diameter, deep invasion and poor differentiation for phospho-CDC25C (Ser216). In univariate analysis, high expression of phospho-CDC25C (Ser216) was correlated with poor disease-specific survival (p = 0.04). However, such an association was annulled in multivariate analysis.

CONCLUSIONS

Our results suggest that CDC25C and phospho-CDC25C (Ser216) play a crucial role and CDC25B a minor role in the pathogenesis and/or progression of vulvar carcinomas. CDC25B, CDC25C and phospho-CDC25C (Ser216) were associated with malignant features and aggressive cancer phenotypes. However, the CDC25s isoforms were not independently correlated to prognosis.

Clinical significance of promoter hypermethylation of DNA repair genes in tumor and serum DNA in invasive ductal breast carcinoma patients

AIMS

The clinical relevance of frequent methylation of CpG islands of key cancer genes in breast cancer is being increasingly recognized. Our study aimed to evaluate the promoter methylation status of DNA repair genes-BRCA1MGMT and GSTP1 in tumor and circulating DNA of invasive ductal breast carcinoma patients.

MAIN METHODS

Methylation-specific PCR was carried out to investigate the promoter methylation status of genes in tumor and circulating DNA of 100 breast cancer patients in a prospective study. The effect of promoter methylation on protein expression was evaluated by immunohistochemistry.

KEY FINDINGS

The frequency of tumor hypermethylation was 27% in BRCA1, 32% in MGMT and 25% in GSTP1 and correlated with methylation of these genes in paired serum DNA. Immunohistochemical analysis showed no detectable expression of BRCA1 and MGMT in 51/89 (57%) and 35/89 (39%) tumors, respectively. MGMT promoter methylation mediated gene silencing was associated with loss of its protein expression (p=0.002, O.R.=4.5, 95% C.I.=1.7-12.0). BRCA1 promoter methylation was not associated with loss of its protein expression, indicating that methylation is not the sole mechanism accounting for the loss/reduced BRCA1 protein expression. Importantly, GSTP1 and BRCA1 hypermethylation were found to be independent of other prognostic factors in predicting disease recurrence (p=0.02, HR=7.6, 95% C.I.=1.4-44.1; p=0.04, HR=6.2, 95% C.I.=1.1-35.7).

SIGNIFICANCE

Our study underscores the potential utility of DNA methylation of these genes in serum as a promising biomarker and can serve as a surrogate for tumor DNA methylation for diagnosis and prognosis of breast cancer.

Hypermethylation of the progesterone receptor A in constitutive antiprogestin-resistant mouse mammary carcinomas

Most breast carcinomas that are estrogen receptor (ER) and progesterone receptor (PR) positive respond initially to an endocrine therapy, but over time, they develop resistance (acquired hormone resistance). Others, however, fail to respond from the beginning (constitutive resistance). Overcoming hormone resistance is one of the major desirable aims in breast cancer treatment. Using the medroxyprogesterone acetate (MPA)-induced breast cancer mouse model, we have previously demonstrated that antiprogestin-responsive tumors show a higher expression level of PR isoform A (PRA) than PR isoform B (PRB), while tumors with constitutive or acquired resistance show a higher expression level of PRB. The aim of this study was to investigate whether PRA silencing in resistant tumors was due to PRA methylation. The CpG islands located in the PRA promoter and the first exon were studied by methylation-specific PCR (MSP) in six different tumors: two antiprogestin-responsive, two constitutive-resistant, and two with acquired resistance. Only in constitutive-resistant tumors, PRA expression was silenced by DNA methylation. Next, we evaluated the effect of a demethylating agent, 5-aza-2'-deoxycytidine, on PRA expression and antiprogestin responsiveness. In constitutive-resistant tumors, 5-aza-2'-deoxycytidine treatment in vitro and in vivo restored PRA expression and antiprogestin RU-486 responsiveness. Furthermore, high levels of DNA methyltransferase (Dnmts) 1 and 3b were detected in these tumors. In conclusion, our results suggest that methyltransferase inhibitors in combination with antiprogestins may be effective in the treatment of constitutive-resistant carcinomas with a high DNA methyltransferase level.

Epigenetic Signatures in Breast Cancer: Clinical Perspective

There is now a compelling body of evidences sustaining the importance of epigenetic mechanisms in the development and progression of cancer. DNA methylation, post-translational histone and other protein modifications, microRNA expression, and nucleosome positioning, all act together to exert their cellular effects. The epigenome is responsible for controlling gene expression thus defining cell differentiation and tissue specificity. This review will focus on DNA methylation and histone modification because these epigenetic events are widely implicated in cancer development and progression. We will in particular address the translational aspects of breast cancer epigenomics including the development of biomarkers and the prospects for epigenetic based pharmacologic treatments. The analysis of DNA methylation has the advantage over other molecular methods (e.g. single gene mutation, microsatellite analysis) that it can be detected with a very high degree of specificity even in the presence of excess unmethylated DNA. Furthermore, the presence of specific CpG methylation signatures makes methylation-based markers attractive diagnostic, prognostic, and predictive tools for better management of breast cancer patients.

Epigenetic regulation in estrogen receptor positive breast cancer--role in treatment response

Recent advances in breast cancer treatment have allowed increasing numbers of patients with estrogen receptor (ER) positive (+) breast cancer to receive various forms of endocrine therapy. Unfortunately, de novo and acquired resistance to endocrine therapy remains a major challenge in the clinic. A number of possible mechanisms for drug resistance have been described, which include activation of growth factor receptor pathways, overexpression of ER coactivators, and metabolic resistance due to polymorphisms in metabolizing enzymes. While many of these changes are caused by genetic alterations, there is also increasing evidence to implicate epigenetic gene regulatory mechanisms in the development of endocrine resistance. Since epigenetic modifications are easier to reverse than genetic mutations, they are appealing therapeutic targets, and thus future improvements in medical care for breast cancer patients will depend upon a better understanding of the roles epigenetic modifications play in endocrine resistance. In this review we will focus on recent advances made in the understanding of epigenetic gene regulation in estrogen response and endocrine resistance in breast cancer. We will also summarize current clinical-translational advances in epigenetic therapy, and discuss potential future clinical use of epigenetic changes as therapeutic targets, especially with respect to endocrine treatment.

Utility of DNA methylation markers for diagnosing cancer

DNA methylation occurs at the CpG residues and serves as a powerful epigenetic mechanism that negatively regulates gene expression. This process is catalyzed by DNA methyltransferases and occurs within "CpG islands" found in the promoter regions of >70% of human genes. Given the important role of DNA methylation in regulating gene expression, un-programmed changes in methylation patterns are expected to either silence or activate transcription of tumor suppressor genes (via hypermethylation) or oncogenes (via demethylation), respectively, and by doing so promote a disease state. In light of the fact that a number of different cancers are frequently associated with hypermethylated tumor suppressor genes together with the observation that tumor derived genomic DNAs are present in various body fluids including serum/plasma, urine, sputum and bronchial lavage, methylated DNA has shown tremendous promise to serve as a robust biomarker for detecting cancer. Over the last several years protocols for capturing small amounts of DNA in circulation have been developed. Once captured, DNA methylation may be readily monitored by restriction enzyme digestion or bisulfite conversion followed by amplification of the desired genomic region with the polymerase chain reaction (PCR). New technologies which employ methyl-binding protein or antibodies that bind specifically to methylated-CpG residues have now enabled investigators to interrogate the status of entire "DNA methyome" of diseased tissue in an efficient and cost-effective manner. In this review, we describe the various tumor suppressor genes that are frequently hypermethylated in different cancers and how these and other methylated loci may be employed as clinically useful biomarkers for diagnosing cancer noninvasively using readily available body fluids.

Promoter methylation and the detection of breast cancer

Mammographic screening has been shown to reduce breast cancer mortality in women over the age of 50 years, and to a lesser extent in younger women. The sensitivity of mammography, however, is reduced in some groups of women. There remains a need for a minimally invasive, cost-effective procedure that could be used along side mammography to improve screening sensitivity. Silencing of tumor suppressor genes through promoter hypermethylation is known to be a frequent and early event in carcinogenesis. Further, changes in methylation patterns observed in tumors are also detectable in the circulation of women with breast cancer. This makes these alterations candidate markers for early tumor detection. In this paper, we review the current literature on promoter hypermethylation changes and breast cancer and discuss issues that remain to be addressed in order for the potential of these markers to augment the sensitivity of screening mammography. In general, studies in well-defined populations, including appropriate controls and larger numbers are needed. Further, focus on the optimization of methods of methylation detection in small amounts of DNA is needed.

CpG hypomethylation of MDR1 gene in tumor and serum of invasive ductal breast carcinoma patients

OBJECTIVES

Multidrug resistance 1 (MDR1) gene encodes P-glycoprotein (P-gp), a transmembrane calcium-dependent efflux pump, implicated in drug resistance. In this prospective study, methylation status of MDR1 promoter and its correlation with clinicopathological parameters were evaluated in tumor and serum of breast cancer patients.

DESIGN AND METHODS

Methylation-specific PCR was carried out to investigate the promoter methylation status of MDR1 in tumor and serum of 100 patients with invasive ductal carcinomas of breast (IDCs). The effect of promoter methylation on protein expression was evaluated by immunohistochemistry.

RESULTS

MDR1 was hypomethylated in 47% tumors and 44% paired sera of IDC patients and correlated significantly with increased tumor size and advanced tumor stage. Promoter hypomethylation of MDR1 in serum DNA showed 98% specificity and 50% sensitivity.

CONCLUSIONS

Hypomethylation of MDR1 promoter in IDCs accounted for P-gp overexpression and aggressive biologic behavior in a subset of patients. Detection of these epigenetic changes in circulating DNA may not only enhance insight into the biological behavior of the primary tumor of an individual but may also provide valuable information regarding prognosis that can be readily monitored throughout the disease course.

CpG island tumor suppressor promoter methylation in non-BRCA-associated early mammary carcinogenesis

BACKGROUND

Only 5% of all breast cancers are the result of BRCA1/2 mutations. Methylation silencing of tumor suppressor genes is well described in sporadic breast cancer; however, its role in familial breast cancer is not known.

METHODS

CpG island promoter methylation was tested in the initial random periareolar fine-needle aspiration sample from 109 asymptomatic women at high risk for breast cancer. Promoter methylation targets included RARB (M3 and M4), ESR1, INK4a/ARF, BRCA1, PRA, PRB, RASSF1A, HIN-1, and CRBP1.

RESULTS

Although the overall frequency of CpG island promoter methylation events increased with age (P<0.0001), no specific methylation event was associated with age. In contrast, CpG island methylation of RARB M4 (P=0.051), INK4a/ARF (P=0.042), HIN-1 (P=0.044), and PRA (P=0.032), as well as the overall frequency of methylation events (P=0.004), was associated with abnormal Masood cytology. The association between promoter methylation and familial breast cancer was tested in 40 unaffected premenopausal women in our cohort who underwent BRCA1/2 mutation testing. Women with BRCA1/2 mutations had a low frequency of CpG island promoter methylation (15 of 15 women had <or=4 methylation events), whereas women without a mutation showed a high frequency of promoter methylation events (24 of 25 women had 5-8 methylation events; P<0.0001). Of women with a BRCA1/2 mutation, none showed methylation of HIN-1 and only 1 of 15 women showed CpG island methylation of RARB M4, INK4a/ARF, or PRB promoters.

CONCLUSIONS

This is the first evidence of CpG island methylation of tumor suppressor gene promoters in non-BRCA1/2 familial breast cancer.

Epigenetic alterations in the breast: Implications for breast cancer detection, prognosis and treatment

Epigenetic alterations of the genome such as DNA promoter methylation and chromatin remodeling play an important role in tumorigenesis. Recent findings indicate epigenetic modifications as key factors in breast carcinogenesis. These modifications are quite appealing as targets for preventative care and therapeutics because of their potential for reversal. Future medical care for breast cancer patients will likely depend upon a better understanding of the roles epigenetic modifications play in carcinogenesis. Here, we discuss the importance of epigenetics in breast cancer detection, prognosis, and therapy with an emphasis on mechanisms and epigenetic contributions to field cancerization effects.

Des-gamma-carboxy prothrombin increases the expression of angiogenic factors in human hepatocellular carcinoma cells

AIMS

Des-gamma-carboxyl prothrombin (DCP) is a serum protein produced by hepatocellular carcinoma (HCC) cells. The aim of this study was to evaluate the angiogenic activity of DCP in HCC cells.

MAIN METHODS

The proliferation of HCC cells was measured by 3-[4, 5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay. The growth of HCC cells was also evaluated in vivo by using the xenografts in nude mice. The enzyme-linked immunosorbent assay (ELISA) was employed to measure the levels of angiogenic factors in supernatant of cell culture. The expression of angiogenic factors was examined by Western blot analysis and immunohistochemical staining.

KEY FINDINGS

DCP displayed the stimulation of HCC cell growth in a dose (5-80 ng/ml) and time (24-96 h) dependent manner. The increase of cell growth was also observed in nude mice bearing well-established, palpable HepG2 and SMMC-7721 xenografts after 2 weeks administration of DCP. HCC cell growth was accompanied by the elevated levels of angiogenic factors. The levels of vascular endothelial growth factor (VEGF), transforming growth factor-alpha (TGF-alpha) and basic fibroblast growth factor (bFGF) in supernatant of SMMC-7721 cells were increased from 47, 126, and 60 pg/10(6) cells/24 h to 400, 208, and 298 pg/10(6) cells/24 h, respectively, after 72 h incubation with 80 ng/ml of DCP. The results of Western blot analysis and immunohistochemical staining of HCC xenografts also showed the significant increase of VEGF, TGF-alpha, and bFGF in HCC cells.

SIGNIFICANCE

These results provide the information that DCP is a type of growth factor in progression of HCC.

Epigenetic alterations of CDH1 and APC genes: relationship with activation of Wnt/beta-catenin pathway in invasive ductal carcinoma of breast

Activation of canonical Wnt/beta-catenin pathway in Invasive Ductal Carcinoma of Breast (IDCs) was recently reported from our laboratory. Herein, we analyzed promoter methylation status of CDH1 and Adenomatous polyposis coli (APC) genes in 50 IDCs and correlated with expression of E-cadherin (E-CD) and APC proteins and with activation of oncogenic Wnt/beta-catenin signaling pathway components, Dvl, beta-catenin and CyclinD1. Further, Wnt/beta-catenin driven epithelial mesenchymal transition (EMT) was investigated by correlating the expression of Dvl, beta-catenin and CyclinD1 with vimentin expression in these IDCs. Promoter hypermethylation was observed in 25/50 (50%) IDCs for CDH1 and in 11/50 (22%) tumors for APC, associated with loss of expression of E-CD and APC proteins; concordant hypermethylation of these genes was observed in paired patients' sera. Further, 57% of tumors harboring CDH1 methylation and 50% tumors harboring the methylated APC gene showed nuclear localization of beta-catenin, suggesting activation of the canonical Wnt/beta-catenin pathway. Our study demonstrates significant association between vimentin expression and nuclear beta-catenin (p=0.001; Odds ratio (OR)=25.6) and Dvl (p=0.023; OR=8.0), suggesting that EMT may be driven by Wnt/beta-catenin activation in IDCs. In conclusion, we demonstrate correlation of CDH1 and APC promoter methylation with loss of E-CD and APC proteins and with activation of Wnt/beta-catenin signaling pathway. Association of nuclear Dvl and beta-catenin with vimentin expression suggests the importance of Wnt/beta-catenin pathway driven EMT in IDCs. The concordance between CDH1 and APC methylation in IDCs and paired circulating DNA underscores the utility of serum DNA as a non-invasive tool for methylation analysis in IDC patients.

Alternative splicing and the progesterone receptor in breast cancer

Progesterone receptor status is a marker for hormone responsiveness and disease prognosis in breast cancer. Progesterone receptor negative tumours have generally been shown to have a poorer prognosis than progesterone receptor positive tumours. The observed loss of progesterone receptor could be through a range of mechanisms, including the generation of alternatively spliced progesterone receptor variants that are not detectable by current screening methods. Many progesterone receptor mRNA variants have been described with deletions of various whole, multiple or partial exons that encode differing protein functional domains. These variants may alter the progestin responsiveness of a tissue and contribute to the abnormal growth associated with breast cancer. Absence of specific functional domains from these spliced variants may also make them undetectable or indistinguishable from full length progesterone receptor by conventional antibodies. A comprehensive investigation into the expression profile and activity of progesterone receptor spliced variants in breast cancer is required to advance our understanding of tumour hormone receptor status. This, in turn, may aid the development of new biomarkers of disease prognosis and improve adjuvant treatment decisions.

Clinical significance of promoter hypermethylation of RASSF1A, RARbeta2, BRCA1 and HOXA5 in breast cancers of Indian patients

Promoter hypermethylation of genes is implicated in the pathogenesis of many cancers, including breast cancer. Herein, we analyzed the promoter methylation status of a panel of critical growth regulatory genes, RASSF1A, RARbeta2, BRCA1 and HOXA5, in 54 breast cancers and 5 distant normal breast tissues of Indian patients. The methylation data were correlated with clinicopathological characteristics and hormone receptor status to determine the impact of methylation in breast carcinogenesis. Promoter hypermethylation of RASSF1A was observed in 39/54 (72%), HOXA5 in 36/54 (67%), BRCA1 in 15/54 (28%) and RARbeta2 in 8/54 (15%) breast cancers. Our most significant findings were the association of RASSF1A methylation with nodal metastasis (p=0.05); and RARbeta2 methylation with age (all tumors in patients in the older age group were methylated, p=0.04). Further, the interactions between DNA methylation and hormone receptor biology in breast cancer cells are beginning to be clearly understood. In this context the association of HOXA5 methylation with loss of ERalpha (p=0.009) is noteworthy.