Early Event In Breast Carcinogenesis Research Articles

Epigenetic alterations at distal enhancers are linked to proliferation in human breast cancer.

Aberrant DNA methylation is an early event in breast carcinogenesis and plays a critical role in regulating gene expression. Here, we perform genome-wide expression-methylation Quantitative Trait Loci (emQTL) analysis through the integration of DNA methylation and gene expression to identify disease-driving pathways under epigenetic control. By grouping the emQTLs using biclustering we identify associations representing important biological processes associated with breast cancer pathogenesis including regulation of proliferation and tumor-infiltrating fibroblasts. We report genome-wide loss of enhancer methylation at binding sites of proliferation-driving transcription factors including CEBP-β, FOSL1, and FOSL2 with concomitant high expression of proliferation-related genes in aggressive breast tumors as we confirm with scRNA-seq. The identified emQTL-CpGs and genes were found connected through chromatin loops, indicating that proliferation in breast tumors is under epigenetic regulation by DNA methylation. Interestingly, the associations between enhancer methylation and proliferation-related gene expression were also observed within known subtypes of breast cancer, suggesting a common role of epigenetic regulation of proliferation. Taken together, we show that proliferation in breast cancer is linked to loss of methylation at specific enhancers and transcription factor binding and gene activation through chromatin looping.

Crosstalk between microRNA expression and DNA methylation drives the hormone-dependent phenotype of breast cancer

BackgroundAbnormal DNA methylation is observed as an early event in breast carcinogenesis. However, how such alterations arise is still poorly understood. microRNAs (miRNAs) regulate gene expression at the post-transcriptional level and play key roles in various biological processes. Here, we integrate miRNA expression and DNA methylation at CpGs to study how miRNAs may affect the breast cancer methylome and how DNA methylation may regulate miRNA expression.MethodsmiRNA expression and DNA methylation data from two breast cancer cohorts, Oslo2 (n = 297) and The Cancer Genome Atlas (n = 439), were integrated through a correlation approach that we term miRNA-methylation Quantitative Trait Loci (mimQTL) analysis. Hierarchical clustering was used to identify clusters of miRNAs and CpGs that were further characterized through analysis of mRNA/protein expression, clinicopathological features, in silico deconvolution, chromatin state and accessibility, transcription factor binding, and long-range interaction data.ResultsClustering of the significant mimQTLs identified distinct groups of miRNAs and CpGs that reflect important biological processes associated with breast cancer pathogenesis. Notably, two major miRNA clusters were related to immune or fibroblast infiltration, hence identifying miRNAs associated with cells of the tumor microenvironment, while another large cluster was related to estrogen receptor (ER) signaling. Studying the chromatin landscape surrounding CpGs associated with the estrogen signaling cluster, we found that miRNAs from this cluster are likely to be regulated through DNA methylation of enhancers bound by FOXA1, GATA2, and ER-alpha. Further, at the hub of the estrogen cluster, we identified hsa-miR-29c-5p as negatively correlated with the mRNA and protein expression of DNA methyltransferase DNMT3A, a key enzyme regulating DNA methylation. We found deregulation of hsa-miR-29c-5p already present in pre-invasive breast lesions and postulate that hsa-miR-29c-5p may trigger early event abnormal DNA methylation in ER-positive breast cancer.ConclusionsWe describe how miRNA expression and DNA methylation interact and associate with distinct breast cancer phenotypes.

P53 alteration in morphologically normal/benign breast tissue in patients with triple-negative high-grade breast carcinomas: breast p53 signature?

p53 alterations have been identified in approximately 23% of breast carcinomas, particularly in hormone receptor-negative high-grade carcinomas. It is considered to be an early event in breast carcinogenesis. Nevertheless, the putative precursor lesion of high-grade breast carcinoma remains elusive. Breast excision specimens from 93 triple-negative high-grade invasive ductal carcinomas, 48 estrogen receptor (ER)-positive/progesterone receptor-positive/Her2-negative non-high-grade invasive ductal carcinomas, and 50 mammoplasty breasts were selected. At least 2 tissue blocks with tumor and adjacent benign tissue were sectioned and subjected to immunohistochemistry staining for p53. TP53 gene sequencing was performed on select tumors. Further immunohistochemistry staining for ER and Ki-67 was performed on consecutive sections of tissue with p53-positive normal/benign cells. Of the 93 high-grade carcinomas, 51 (55%) were positive for p53 alteration, whereas only 3 (6.25%) of the 48 non-high-grade carcinomas were p53 altered. Focal p53 positivity in adjacent normal/benign breast tissue was identified in 19 cases, and 18 of them also had p53 alteration in their carcinomas. Only 1 case had focal p53 staining in normal/benign tissue, but the tumor was negative for p53 alteration. No p53 staining positivity was identified in the mammoplasty specimens. The p53-stained normal/benign cells were ER negative and did not show an increase in the Ki-67 labeling index. These findings indicate that the p53 staining positivity in normal/benign breast tissue is not a random event. It could be considered as the "p53 signature" in breast and serve as an indicator for future potential risk of p53-positive high-grade breast carcinoma.

Potential of breastmilk analysis to inform early events in breast carcinogenesis: rationale and considerations.

This review summarizes methods related to the study of human breastmilk in etiologic and biomarkers research. Despite the importance of reproductive factors in breast carcinogenesis, factors that act early in life are difficult to study because young women rarely require breast imaging or biopsy, and analysis of critical circulating factors (e.g., hormones) is often complicated by the requirement to accurately account for menstrual cycle date. Accordingly, novel approaches are needed to understand how events such as pregnancy, breastfeeding, weaning, and post-weaning breast remodeling influence breast cancer risk. Analysis of breastmilk offers opportunities to understand mechanisms related to carcinogenesis in the breast, and to identify risk markers that may inform efforts to identify high-risk women early in the carcinogenic process. In addition, analysis of breastmilk could have value in early detection or diagnosis of breast cancer. In this article, we describe the potential for using breastmilk to characterize the microenvironment of the lactating breast with the goal of advancing research on risk assessment, prevention, and detection of breast cancer.

Abstract P6-07-11: On the origin of T>C transition mutations in breast cancer

Abstract Background: Mutations in cancer driver genes are thought to occur early in tumorigenesis. Examination of the sequence context enables the inference of causality. For example, C>A transversions in lung malignancies are ascribed to tobacco smoke. A large proportion of clonal and subclonal mutations in breast cancer are attributed to the APOBEC cytidine deaminases. However, 26% of clonal mutations in cancer genes in the breast and 15% of subclonal mutations are T>C transitions [Sci Transl Med. 2015;7:283ra54]. The purpose of this study was to determine if the T>C transitions are likely an early event in breast carcinogenesis and look for clues to the mechanism by which they are produced. Methods: Histologically normal tissue adjacent to a cancer provides a window into the early steps of oncogenesis. BAM files of exome sequencing data from 11 matched trios of tumor, adjacent normal tissue and blood (leukocyte DNA) from the TCGA (The Cancer Genome Atlas) breast cancer dataset were downloaded from the UCSC cgHUB repository. Mutations were called using the MuTect software (Broad Institute, Cambridge, MA). As a validation cohort, data was downloaded from 29 additional specimens that had been added to TCGA subsequent to the initial data set, and analyzed as above. RNA-Seq data from the initial adjacent normal was downloaded from the TCGA data portal. The epithelia from 20 frozen tissue cores from healthy premenopausal donors to the Susan G. Komen Tissue Bank were microdissected and the RNA isolated. RNA-sequencing was carried out using the Life Technologies SOLiD Platform. RPKM gene expression values from TCGA and sequencing of the Komen normal tissues were merged, quantile normalized, and batch effect corrected. Normalization and differential gene expression was performed using Partek Genomics Suite. Results: C>T and T>C transition mutations make up the majority of the mutations in histologically normal tissue adjacent to breast cancer. Displaying mutations in their trinucleotide context, i.e., by the sequence context immediately 5' and 3' to the mutated base revealed that T>C mutations most frequently occur in the 5'-ATG-3', 5'-CTG-3' and 5'-ATA-3' contexts. Analysis of the RNA-Seq data discovered 1821 genes to be differentially expressed (FDR<5%). Relevant to the questions being addressed in this study, the expression of Nitric Oxide Synthase 3, an enzyme that synthesizes nitric oxide from L-arginine, is 4-times greater in adjacent normal (p= 4.55E-03). [Of note, published data reveals no significant contamination of adjacent normal with tumor in the TCGA breast data.] Conclusions: NOS3 expression is enhanced in certain inflammatory environments as well as by estrogen. Nitric oxide induces DNA damage; one mechanism is through the N2O3 pathway. Reaction of DNA with N2O3 leads to the deamination adenine to form hypoxanthine. Thymine-DNA glycosylase (TDG) initiates base excision repair (BER). Talhaoui et al [Nucleic Acids Res. 2014;42:6300-13] have recently shown that TDG excises T when it is paired with hypoxanthine. Downstream in this aberrant BER pathway the abasic site is repaired to a C resulting in the T>C transition. The excision of the T is efficient only in a specific nucleotide context, which is 5'-TpG-3', as was observed in our study. Citation Format: Choi M, Radovich M, Brown C, Clare SE. On the origin of T>C transition mutations in breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-07-11.

Methylation biomarkers for pleomorphic lobular breast cancer - a short report

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

Promoter hypermethylation profiling of distant breast cancer metastases.

Promoter hypermethylation of tumor suppressor genes seems to be an early event in breast carcinogenesis and is potentially reversible. This makes methylation a possible therapeutic target, a marker for treatment response and/or a prognostic factor. Methylation status of 40 tumor suppressor genes was compared between 53 primary breast tumors and their corresponding metastases to brain, lung, liver, or skin. In paired analyses, a significant decrease in methylation values was seen in distant metastases compared to their primaries in 21/40 individual tumor suppressor genes. Furthermore, primary tumors that metastasized to the liver clustered together, in line with the finding that primary breast carcinomas that metastasized to the brain, skin, or lung, showed higher methylation values in up to 27.5 % of tumor suppressor genes than primary carcinomas that metastasized to the liver. Conversion in methylation status of several genes from the primary tumor to the metastasis had prognostic value, and methylation status of some genes in the metastases predicted survival after onset of metastases. Methylation levels for most of the analyzed tumor suppressor genes were lower in distant metastases compared to their primaries, pointing to the dynamic aspect of methylation of these tumor suppressor genes during cancer progression. Also, specific distant metastatic sites seem to show differences in methylation patterns, implying that hypermethylation profiles of the primaries may steer site-specific metastatic spread. Lastly, methylation status of the metastases seems to have prognostic value. These promising findings warrant further validation in larger patient cohorts and more tumor suppressor genes.Electronic supplementary materialThe online version of this article (doi:10.1007/s10549-015-3362-y) contains supplementary material, which is available to authorized users.

DNA Hypermethylation Detected in Invasive Breast Cancer

DNA methylation as an early event in breast carcinogenesis has been frequently studied in tumor samples. The aim of this study was to compare the relationship between DNA methylation levels of genes associated with invasivity and metastasising and aberrant protein expression. A total 55 healthy controls and 185 patients with primary breast cancer, as well as plasma and peripheral blood cells has been analysed by using pyrosequencing method. The expression of 11 proteins in paraffin-embedded biopsy was evaluated by immunohistochemistry. Genes containing CpG islands in promotor region were suggested for screening because they could be epigenetically regulated with high probability. DNA methylation of APC, ADAM23, CXCL12, ESR1, PGR B, CDH1, RASSF1A, SYK, TIMP3, BRMS1 and SOCS1 genes has been detected. DNA hypermethylation of tumor suppressor genes is tumor-specific and could be used for recognition of tumor cells. We

Changed lineage composition is an early event in breast carcinogenesis.

The epithelium compartment of the human breast is made up of a branching ductal-lobular system, which is lined by a single layer of luminal epithelial cells surrounded by contractile myoepithelial cells. The co-ordinated development of these two cell types, and maintenance of their relative proportions, is fundamentally important for normal breast morphogenesis. Changes in cell type composition is one of the hallmark features of breast cancer progression, and the vast majority of breast tumors are comprised of luminal cells only, with a complete absence of myoepithelial cells. Despite this striking alteration in relative proportions of luminal and myoepithelial cells in invasive breast cancers compared with normal breast tissue, the steps in this dramatic change in cellular composition remain poorly characterised, nor is it known whether loss of myoepithelial cells is an early event in carcinogenesis. In a panel of breast tissues, we quantitated the proportion of luminal cells relative to the surrounding myoepithelial cell layer in a panel of normal and pre-invasive breast tissue samples, including lesions with proliferative disease without atypia (PDWA), columnar cell lesions (CCL), atypical ductal hyperplasia (ADH), and DCIS, and correlated these findings with proliferation in the same lesions. The study findings showed that changes in lineage composition correlate with increased proliferation, and are one of the earliest events in breast carcinogenesis. Therefore not only are myoepithelial cells important in distinguishing between invasive and non-invasive tumors, their relative proportion compared with luminal cell numbers may provide a new potential indicator of which premalignant lesions are at higher risk of progression to invasive disease.

Abstract LB-256: Estrogen and its receptors alpha and beta in different stages of breast carcinogenesis.

Abstract Excessive exposure to Estrogen has long been indicated to increase breast cancer risk. Although the anti-estrogen endocrine therapy by selective estrogen receptor modulator (SERM) is widely used to treat the ERα-positive breast cancers, there are several mysteries in the field: 1) Some ERα positive breast cancers do not respond to tamoxifen; 2) Some ERα negative breast cancers also respond to tamoxifen; 3) Strikingly, physiological estrogen can cause dramatic tumor regression of long-term tamoxifen-resistant ERα-positive breast cancer; 4) When ERα is overexpressed in genetically engineered mice, mammary tumors form but they do not progress to invasive cancer, which indicates that the activation of ERα alone does not fully explain the action of estrogen. To uncover these mysteries, we focus on the following two main points: 1) Role of ERβ, the second estrogen receptor, which is the more abundant ER in the normal breast. Estradiol, the main type of estrogen, binds with ERα and ERβ with the similar affinity, but there are quite differences for some SERMs. 2) Differential function of two ERs in each stage of breast carcinogenesis. Breast cancer is a heterogeneous disease and also is a chronically developed disease, which occurs through a series of steps. The tumor cells in different development steps have distinct molecular profiles and clinical behaviors. First we used a large set of well-documented surgical excised human ductal breast cancer samples and carefully examined the tumor histology and the expression of ERα and ERβ by IHC staining. Most of these samples contained normal areas as well as areas of hyperplasia, ductal carcinoma in situ (DCIS) and invasive ductal cancer (IDC). We compared ERα and ERβ expression in different cancer stages within each woman. Our results suggest that ERβ loss is an early event in breast carcinogenesis, ERα has dual role in cancer proliferation and invasion, and ERβ/ERα ratio seems to be one of the determinants for the breast cancer initiation and progression to malignancy. Then we use inducible ERα transgenic mouse model to verify the findings in the human samples study. This ERα transgenic mouse develops DCIS, but not IDC. We use estradiol as well as several specific ligands for ERα and ERβ to treat this mouse and also generate a unique animal model by crossing ERα transgenic mouse with ERβ knockout mice to address the differential role of ERα and ERβ in breast cancer initiation and progression. The clinical application of our findings will be discussed. Citation Format: Bo Huang, Yoko Omoto, Hirotaka Iwase, Hiroko Yamashita, Tatsuya Toyama, Margaret Warner, Jan-Åke Gustafsson. Estrogen and its receptors alpha and beta in different stages of breast carcinogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-256. doi:10.1158/1538-7445.AM2013-LB-256

Abstract B89: Endogenous hormone levels and lobular involution of the breast among healthy, postmenopausal women in the Komen Tissue Bank Study

Abstract Background: Terminal ductal lobular units (TDLUs), the functional units of the breast for lactation, are the structures from which most breast cancers arise. TDLU involution, reflecting atrophy and loss of TDLUs, has been related to lower subsequent breast cancer risk. The predictors of such breast tissue aging, however, are not well defined. Given that estrogens and other hormones play a central role in the etiology of postmenopausal breast cancers, we conducted a study to assess the relationship between four hormones and sex hormone-binding globulin (SHBG) with markers of TDLU involution. Methods: Subjects included healthy women who volunteered between 2009 and 2011 to participate in the Komen Tissue Bank Study. Participants completed a risk factor questionnaire, provided a blood sample, and donated breast tissue for research. Our analysis was restricted to postmenopausal women who were not currently taking menopausal hormones (n=153). A pathologist, masked to patient data, assessed tissue sections for the presence of TDLUs and, among sections containing TDLUs (n=88), measured TDLU diameters for up to ten TDLUs per section. Both presence of TDLUs and TDLU diameter are inversely related to involution. Chemiluminescent immunometric assays were used to measure serum levels of estradiol (E2), SHBG, follicle-stimulating hormone (FSH), and prolactin. Percent free E2 was calculated from measured E2 and SHBG levels. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the presence of TDLUs (none or any) associated with tertiles of serum hormone and SHBG levels. Multivariable ordinal logistic regression was used to calculate ORs, 95% CIs, and p-trend for TDLU diameter categorized as tertiles (≥218.4, 218.4-281, and ≥281 microns) with serum hormone and SHBG levels. All models were adjusted for potential confounding factors. Results: The study population was 87.6% Caucasian with a mean age of 59.5 years, and >2/3 of the women were overweight or obese. Increasing percent free E2 was significantly associated with larger TDLU diameter (OR>2.53 vs. ≥1.99: 5.58, 95% CI: 1.48-21.07; p-trend=0.01), whereas increasing SHBG was associated with smaller TDLU diameter (OR>73nmol/L vs. ≥38 nmol/L: 0.19, 95% CI: 0.05-0.74; p-trend=0.02). Total E2 (p-trend=0.49), FSH (p-trend=0.85), and prolactin (p-trend=0.58) were not associated with TDLU diameter. We did not find significant relationships between the presence of TDLUs and any of the serum levels. Our observed relationships were not modified by age or other breast cancer risk factors, including BMI, years since menopause, and history of bilateral oophorectomy. Conclusion: Based on limited data, these findings suggest that sex hormones may play a role in TDLU involution. Thus, TDLU involution may represent one mechanism by which hormone levels influence breast cancer risk. TDLU measurements may therefore be helpful in assessing breast cancer risk as a marker of breast tissue aging. Analysis of the relationships between hormones and TDLU involution among premenopausal women may provide additional insights into early events in breast carcinogenesis. Citation Format: Zeina G. Khodr, Mark E. Sherman, Ruth M. Pfeiffer, Gretchen L. Gierach, Louise A. Brinton, Roni T. Falk, Deesha Patel, Laura Linville, Susan E. Clare, Daniel Visscher, Carolyn Mies, Stephen Hewitt, Anna Maria Storniolo, Jonine D. Figueroa. Endogenous hormone levels and lobular involution of the breast among healthy, postmenopausal women in the Komen Tissue Bank Study. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr B89.

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

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

The Susan G. Komen for the Cure Tissue Bank at the IU Simon Cancer Center: A Unique Resource for Defining the “Molecular Histology” of the Breast

"Molecular histology" of the breast may be conceptualized as encompassing the normative ranges of histologic structure and marker expression in normal breast tissues in relation to a woman's age and life experiences. Studies of molecular histology can aid our understanding of early events in breast carcinogenesis and provide data for comparison with diseased breast tissues. Until recently, lack of epidemiologically annotated, optimally prepared normal breast tissues obtained from healthy women presented a barrier to breast cancer research. The Komen Tissue Bank at Indiana University (Indianapolis, IN) is a unique biorepository that was developed to overcome this limitation. The Bank enrolls healthy donors who provide questionnaire data, blood, and up to four breast biopsies, which are prepared as both formalin-fixed, paraffin-embedded and frozen tissues. The resource is accessible to researchers worldwide through a proposal submission, review, and approval process. As of November 2010, the Bank had collected specimens and information from 1,174 donors. In this review, we discuss the importance of studying normal breast tissues, assess the strengths and limitations of studying normal tissues obtained from different sources, and summarize the features of the Komen Tissue Bank. As research projects are completed, results will be posted on the Bank's website.

Role of Fos‐related antigen 1 in the progression and prognosis of ductal breast carcinoma

AimsFos-related antigen 1 (Fra-1) is a member of the activator protein 1 (AP-1) transcription factor family. Our objective was to evaluate the role of Fra-1 expression in breast carcinoma progression and prognosis.Methods and resultsFra-1 expression was investigated by immunohistochemistry in two tissue microarrays containing, respectively, 85 ductal carcinoma in situ (DCIS) and 771 invasive ductal carcinoma (IDC) samples. Staining was observed in the nucleus and cytoplasm of the carcinomas, but only nuclear staining was considered to be positive. Fibroblasts associated with IDC were also Fra-1-positive. The frequency of Fra-1 positivity in IDC (22.8%) was lower than that in DCIS (42.2%). No association was found between Fra-1 and clinico-pathological variables in DCIS. In IDC, Fra-1 expression correlated with aggressive phenotype markers, including: high grade, oestrogen receptor negativity and human epidermal growth factor receptor 2 (HER-2) positivity (P = 0.001, 0.015 and 0.004, respectively), and marginally with the presence of metastasis (P = 0.07). Fra-1 was more frequently positive in basal-like (34%) and in HER-2-positive (38.5%) subtypes than in luminal subtypes. Fra-1 presence did not correlate with survival.ConclusionsA high frequency of Fra-1 in DCIS tumours may be associated with early events in breast carcinogenesis. Although Fra-1 expression correlated with features of a more aggressive phenotype in IDC, no relationship with overall survival was found.

Epigenetic reprogramming of breast cancer cells with oocyte extracts

BackgroundBreast cancer is a disease characterised by both genetic and epigenetic alterations. Epigenetic silencing of tumour suppressor genes is an early event in breast carcinogenesis and reversion of gene silencing by epigenetic reprogramming can provide clues to the mechanisms responsible for tumour initiation and progression. In this study we apply the reprogramming capacity of oocytes to cancer cells in order to study breast oncogenesis.ResultsWe show that breast cancer cells can be directly reprogrammed by amphibian oocyte extracts. The reprogramming effect, after six hours of treatment, in the absence of DNA replication, includes DNA demethylation and removal of repressive histone marks at the promoters of tumour suppressor genes; also, expression of the silenced genes is re-activated in response to treatment. This activity is specific to oocytes as it is not elicited by extracts from ovulated eggs, and is present at very limited levels in extracts from mouse embryonic stem cells. Epigenetic reprogramming in oocyte extracts results in reduction of cancer cell growth under anchorage independent conditions and a reduction in tumour growth in mouse xenografts.ConclusionsThis study presents a new method to investigate tumour reversion by epigenetic reprogramming. After testing extracts from different sources, we found that axolotl oocyte extracts possess superior reprogramming ability, which reverses epigenetic silencing of tumour suppressor genes and tumorigenicity of breast cancer cells in a mouse xenograft model. Therefore this system can be extremely valuable for dissecting the mechanisms involved in tumour suppressor gene silencing and identifying molecular activities capable of arresting tumour growth. These applications can ultimately shed light on the contribution of epigenetic alterations in breast cancer and advance the development of epigenetic therapies.

Genetic mutations and expression of p53 in non-invasive breast lesions

Breast carcinogenesis results from the accumulation of numerous somatic genetic alterations. Although mutations of the tumor suppressor gene p53 are among the most common alterations identified in invasive breast carcinomas, it is not clear whether its alteration occurs frequently in non-invasive breast lesions, including usual ductal hyperplasia (UDH), atypical ductal hyperplasia (ADH) and ductal carcinoma insitu (DCIS). p53 mutations were examined in 140 cases of non-invasive breast lesions, including UDH, ADH and DCIS, by high-resolution melting (HRM), followed by DNA sequence analysis. Two hundred and forty cases of non-invasive breast lesions were subjected to the immunohistochemical staining of p53 protein. The HRM and sequencing analysis demonstrated that the positive rates of p53 mutation were 0.0, 12.7and 21.6% in UDH, ADH and DCIS, respectively. p53 protein expression was detected in none of the UDH, 14.6% of the ADH and 31.4% of the DCIS samples. Statistically, p53 mutation and protein accumulation gradually increased from UDH to ADH and to DCIS (P<0.05). There was a significantly positive association between p53 mutations and expression in these samples. p53 mutations and accumulation occur in non-invasive breast lesions, including ADH and DCIS, and may represent early events in breast carcinogenesis.

Is the Expression of Inducible (iNOS) and Endothelial (eNOS) Nitric Oxide Synthases an Early Event in Breast Carcinogenesis?

Is the Expression of Inducible (iNOS) and Endothelial (eNOS) Nitric Oxide Synthases an Early Event in Breast Carcinogenesis?

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.

Abstract LB-61: Comparative study of different diagnostic techniques (AI, MLPA, FISH) in breast cancer patients with 1q25.3 alterations

Abstract Background: Breast cancer is the most frequently diagnosed malignancy among women and is the leading cause of cancer related death worldwide. Molecular genetic studies have revealed many subgroups of breast cancer within which the genomic alterations affecting chromosome arm 1q are considered to be an early event in breast carcinogenesis and are correlated with favorable prognosis for the patients. We have found a high percentage of concordance between the AI and MLPA assays pointing towards gain of the 1q25.3 region in breast cancer. Aims: Our main objective was to compare the sensitivity and specificity of AI and synthetic probe-based MLPA with other cytogenetic method (FISH) in breast cancer patients with or without previously confirmed alterations within 1q25.3. Methods: FISH was performed on formalin-fixed paraffin-embedded tumor material in order to verify previous findings and assess the level of genetic alterations of 1q25.3 in breast cancer. The 1q25.3 test and 1p35 reference probes labeled with different fluorochromes were utilized for analysis. Results: A total of 70 nuclei from each breast cancer case were examined and scored for the percentage of 1q25.3 alterations. The non-tumorigenic nuclei obtained from healthy individuals served as adequate cut-off for the 1q25.3-specific changes. The overall FISH results are consistent with results obtained from previous analysis in the majority of analysed cases. Furthermore, FISH resolved the level of 1q25.3 alterations in few cases that were uncertain by AI and MLPA analysis. Conclusion: This study shows that both AI and MLPA assays are able to map regions of copy number changes in the cancer genome and are in concordance with molecular cytogenetics. These three techniques proved to be an efficient tool for diagnosis of 1q25.3 alterations, however, confusing results in AI and MLPA analysis might be obtained while using non-microdissected tumor DNA as a template. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-61.

Epigenetic Silencing of the p16 INK4a Tumor Suppressor Is Associated with Loss of CTCF Binding and a Chromatin Boundary

The p16(INK4a) tumor suppressor gene is a frequent target of epigenetic inactivation in human cancers, which is an early event in breast carcinogenesis. We describe the existence of a chromatin boundary upstream of the p16 gene that is lost when this gene is aberrantly silenced. We show that the multifunctional protein CTCF associates in the vicinity of this boundary and absence of binding strongly coincides with p16 silencing in multiple types of cancer cells. CTCF binding also correlates with RASSF1A and CDH1 gene activation, and CTCF interaction is absent when these genes are methylated and silenced. Interestingly, defective poly(ADP-ribosyl)ation of CTCF and dissociation from the molecular chaperone Nucleolin occur in p16-silenced cells, abrogating its proper function. Thus, destabilization of specific chromosomal boundaries through aberrant crosstalk between CTCF, poly(ADP-ribosyl)ation, and DNA methylation may be a general mechanism to inactivate tumor suppressor genes and initiate tumorigenesis in numerous forms of human cancers.