Dataset Information

High-Resolution Bisulfite-Sequencing of Peripheral Blood DNA Methylation in Early-Onset and Familial Risk Breast Cancer Patients.

ABSTRACT: PURPOSE:Understanding and explaining hereditary predisposition to cancer has focused on the genetic etiology of the disease. However, mutations in known genes associated with breast cancer, such as BRCA1 and BRCA2, account for less than 25% of familial cases of breast cancer. Recently, specific epigenetic modifications at BRCA1 have been shown to promote hereditary breast cancer, but the broader potential for epigenetic contribution to hereditary breast cancer is not yet well understood. EXPERIMENTAL DESIGN:We examined DNA methylation through deep bisulfite sequencing of CpG islands and known promoter or regulatory regions in peripheral blood DNA from 99 patients with familial or early-onset breast or ovarian cancer, 6 unaffected BRCA mutation carriers, and 49 unaffected controls. RESULTS:In 9% of patients, we observed altered methylation in the promoter regions of genes known to be involved in cancer, including hypermethylation at the tumor suppressor PTEN and hypomethylation at the proto-oncogene TEX14. These alterations occur in the form of allelic methylation that span up to hundreds of base pairs in length. CONCLUSIONS:Our observations suggest a broader role for DNA methylation in early-onset, familial risk breast cancer. Further studies are warranted to clarify these mechanisms and the benefits of DNA methylation screening for early risk prediction of familial cancers.

SUBMITTER: Chen J

PROVIDER: S-EPMC6726519 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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High-Resolution Bisulfite-Sequencing of Peripheral Blood DNA Methylation in Early-Onset and Familial Risk Breast Cancer Patients.

Chen Justin J Haanpää Maria K MK Gruber Joshua J JJ Jäger Natalie N Ford James M JM Snyder Michael P MP

Clinical cancer research : an official journal of the American Association for Cancer Research 20190607 17

<h4>Purpose</h4>Understanding and explaining hereditary predisposition to cancer has focused on the genetic etiology of the disease. However, mutations in known genes associated with breast cancer, such as <i>BRCA1</i> and <i>BRCA2</i>, account for less than 25% of familial cases of breast cancer. Recently, specific epigenetic modifications at <i>BRCA1</i> have been shown to promote hereditary breast cancer, but the broader potential for epigenetic contribution to hereditary breast cancer is not ...[more]

PMID: 31175093

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Project description:BackgroundColorectal cancer (CRC) cases with an age of onset <40 years suggests a germline genetic cause. In total, 51 simplex cases were included to test the hypothesis of CRC as a mendelian trait caused by either heterozygous autosomal dominant or bi-allelic autosomal recessive pathogenic variants.MethodsThe cohort was whole exome sequenced (WES) at 100× coverage. Both a dominant- and recessive model were used for searching predisposing genetic factors. In addition, we assayed recessive variants of potential moderate risk that were enriched in our young-onset CRC cohort. Variants were filtered using a candidate cancer gene list or by selecting variants more likely to be pathogenic based on variant type (e.g., loss-of-function) or allele frequency.ResultsWe identified one pathogenic variant in PTEN in a patient subsequently confirmed to have a hereditary hamartoma tumor syndrome (Cowden syndrome) and one patient with a pathogenic heterozygous variant in PMS2 that was originally not identified by WES due to low quality reads resulting from pseudogenes. In addition, we identified three heterozygous candidate missense variants in known cancer susceptibility genes (BMPR1A, BRIP1, and SRC), three truncating variants in possibly novel cancer genes (CLSPN, SEC24B, SSH2) and four candidate missense variants in ACACA, NR2C2, INPP4A, and DIDO1. We also identify five possible autosomal recessive candidate genes: ATP10B, PKHD1, UGGT2, MYH13, TFF3.ConclusionTwo clear pathogenic variants were identified in patients that had not been identified clinically. Thus, the chance of detecting a hereditary cancer syndrome in patients with CRC at young age but without family history is 2/51 (4%) and therefore the clinical benefit of genetic testing in this patient group is low. Of note, using stringent filtering, we have identified a total of ten candidate heterozygous variants and five possibly biallelic autosomal recessive candidate genes that warrant further study.

Project description:BackgroundWomen with a family history of breast cancer face considerable uncertainty about whether to pursue standard screening, intensive screening, or prophylactic surgery. Accurate and individualized risk-estimation approaches may help these women make more informed decisions. Although highly penetrant genetic variants have been associated with familial breast cancer (FBC) risk, many individuals do not carry these variants, and many carriers never develop breast cancer. Common risk variants have a relatively modest effect on risk and show limited potential for predicting FBC development. As an alternative, we hypothesized that additional genomic data types, such as gene-expression levels, which can reflect genetic and epigenetic variation, could contribute to classifying a person's risk status. Specifically, we aimed to identify common patterns in gene-expression levels across individuals who develop FBC.MethodsWe profiled peripheral blood mononuclear cells from women with a family history of breast cancer (with or without a germline BRCA1/2 variant) and from controls. We used the support vector machines algorithm to differentiate between patients who developed FBC and those who did not. Our study used two independent datasets, a training set of 124 women from Utah (USA) and an external validation (test) set from Ontario (Canada) of 73 women (197 total). We controlled for expression variation associated with clinical, demographic, and treatment variables as well as lymphocyte markers.ResultsOur multigene biomarker provided accurate, individual-level estimates of FBC occurrence for the Utah cohort (AUC = 0.76 [0.67-84]) . Even at their lower confidence bounds, these accuracy estimates meet or exceed estimates from alternative approaches. Our Ontario cohort resulted in similarly high levels of accuracy (AUC = 0.73 [0.59-0.86]), thus providing external validation of our findings. Individuals deemed to have "high" risk by our model would have an estimated 2.4 times greater odds of developing familial breast cancer than individuals deemed to have "low" risk.ConclusionsTogether, these findings suggest that gene-expression levels in peripheral blood cells reflect genomic variation associated with breast cancer risk and that such data have potential to be used as a non-invasive biomarker for familial breast cancer risk.

Dataset Information

High-Resolution Bisulfite-Sequencing of Peripheral Blood DNA Methylation in Early-Onset and Familial Risk Breast Cancer Patients.

Publications

High-Resolution Bisulfite-Sequencing of Peripheral Blood DNA Methylation in Early-Onset and Familial Risk Breast Cancer Patients.

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