Project description:Xenoestrogens are part of a group of agents termed endocrine disruptors because of their capacity to perturb normal hormonal actions. It has been suggested that xenoestrogens may contribute to the development of hormone-dependent cancers, such as breast and endometrial cancers. Bisphenol A (BPA) is polymerized to manufacture polycarbonate plastic and epoxy resins. Human exposure occurs when BPA leaches from plastic-lined food and beverage cans. In the present work we are aiming to determine if BPA has carcinogenic properties by using an in vitro system. For this purpose the human breast epithelial cells MCF-10F were treated with 10-3M to 10-9M BPA continuously for two weeks. The MCF-10F cells treated with 10-3M and 10-4M BPA died, indicating that these concentrations were toxic for the human breast epithelial cells. The cells treated with 10-5M to 10-9M BPA were evaluated for formation of solid masses in collagen and invasion capacity, both phenotypes that are indicators of cell transformation. MCF-10F treated with 10-5M, 10-6M, 10-7M, 10-8M and 10-9M BPA formed a high percentage of solid masses (34.6%, 20%, 42.4%, 31.8% and 32.2%, respectively). Ten passages after BPA treatments, the invasive capacities of the cells were evaluated using Boyden chambers. The invasion capacity was lower in the cells treated at high concentrations of BPA (10-5M and 10-6M), and there was an increased invasion for the cells treated at low BPA concentration (10-9M) although, in all the cases the differences were not significant to the controls. Expression and DNA methylation analyses were performed with the cells treated with 10-5M and 10-6M BPA. We found that these cells showed an increased expression of BRCA1, BARD1, CtIP, RAD51 and BRCC3, all genes involved in DNA repair, and downregulation of PDCD5 and BCL2L11 (also known as BIM), both involved in apoptosis. The upregulation of CtIP was related to hypomethylation of the promoter/exon1 of this gene. Furthermore, BPA induced silencing of BCL2L11 by hypermethylation. This is the first demonstration that BPA induces neoplastic transformation of breast epithelial cells and that aberrant DNA methylation of genes involved in DNA repair and apoptosis could be involved in the initiation of the neoplastic process.

Project description:BackgroundDiesel exhaust particles (DEP), which contain hazardous compounds, are emitted during the combustion of diesel. As approximately one-third of the vehicles worldwide use diesel, there are growing concerns about the risks posed by DEP to human health. Long-term exposure to DEP is associated with airway hyperresponsiveness, pulmonary fibrosis, and inflammation; however, the molecular mechanisms behind the effects of DEP on the respiratory tract are poorly understood. Such mechanisms can be addressed by examining transcriptional and DNA methylation changes. Although several studies have focused on the effects of short-term DEP exposure on gene expression, research on the transcriptional effects and genome-wide DNA methylation changes caused by long-term DEP exposure is lacking. Hence, in this study, we investigated transcriptional and DNA methylation changes in human adenocarcinoma alveolar basal epithelial A549 cells caused by prolonged exposure to DEP and determined whether these changes are concordant.ResultsDNA methylation analysis using the Illumina Infinium MethylationEPIC BeadChips showed that the methylation levels of DEP-affected CpG sites in A549 cells changed in a dose-dependent manner; the extent of change increased with increasing dose reaching the statistical significance only in samples exposed to 30 µg/ml DEP. Four-week exposure to 30 µg/ml of DEP significantly induced DNA hypomethylation at 24,464 CpG sites, which were significantly enriched for DNase hypersensitive sites, genomic regions marked by H3K4me1 and H3K27ac, and several transcription factor binding sites. In contrast, 9,436 CpG sites with increased DNA methylation levels were significantly overrepresented in genomic regions marked by H3K27me3 as well as H3K4me1 and H3K27ac. In parallel, gene expression profiling by RNA sequencing demonstrated that long-term exposure to DEP altered the expression levels of 2,410 genes, enriching 16 gene sets including Xenobiotic metabolism, Inflammatory response, and Senescence. In silico analysis revealed that the expression levels of 854 genes correlated with the methylation levels of the DEP-affected cis-CpG sites.ConclusionsTo our knowledge, this is the first report of genome-wide transcriptional and DNA methylation changes and their associations in A549 cells following long-term exposure to DEP.

Project description:Xenoestrogens are part of a group of agents termed endocrine disruptors because of their capacity to perturb normal hormonal actions. It has been suggested that xenoestrogens may contribute to the development of hormone-dependent cancers, such as breast and endometrial cancers. Bisphenol A (BPA) is polymerized to manufacture polycarbonate plastic and epoxy resins. Human exposure occurs when BPA leaches from plastic-lined food and beverage cans. In the present work we are aiming to determine if BPA has carcinogenic properties by using an in vitro system. For this purpose the human breast epithelial cells MCF-10F were treated with 10-3M to 10-9M BPA continuously for two weeks. The MCF-10F cells treated with 10-3M and 10-4M BPA died, indicating that these concentrations were toxic for the human breast epithelial cells. The cells treated with 10-5M to 10-9M BPA were evaluated for formation of solid masses in collagen and invasion capacity, both phenotypes that are indicators of cell transformation. MCF-10F treated with 10-5M, 10-6M, 10-7M, 10-8M and 10-9M BPA formed a high percentage of solid masses (34.6%, 20%, 42.4%, 31.8% and 32.2%, respectively). Ten passages after BPA treatments, the invasive capacities of the cells were evaluated using Boyden chambers. The invasion capacity was lower in the cells treated at high concentrations of BPA (10-5M and 10-6M), and there was an increased invasion for the cells treated at low BPA concentration (10-9M) although, in all the cases the differences were not significant to the controls. Expression and DNA methylation analyses were performed with the cells treated with 10-5M and 10-6M BPA. We found that these cells showed an increased expression of BRCA1, BARD1, CtIP, RAD51 and BRCC3, all genes involved in DNA repair, and downregulation of PDCD5 and BCL2L11 (also known as BIM), both involved in apoptosis. The upregulation of CtIP was related to hypomethylation of the promoter/exon1 of this gene. Furthermore, BPA induced silencing of BCL2L11 by hypermethylation. This is the first demonstration that BPA induces neoplastic transformation of breast epithelial cells and that aberrant DNA methylation of genes involved in DNA repair and apoptosis could be involved in the initiation of the neoplastic process. MCF-10F, a normal-like Homo sapiens breast epithelial cell (HBEC) line that is ERa-negative PR-negative, was maintained in high calcium medium at 37Â°C and 5% CO2 until confluent. These cells were treated with different concentrations of BPA continuously for two weeks, adding fresh media every day. As controls, MCF-10F cells were not treated and maintained in the regular media or treated with 0.284% DMSO (vehicle). The cells treated with 10-5M or 10-6M BPA after the invasion assay were collected and expanded during 6 passages. DNA was isolated from the cells using a DNA extraction kit (Qiagen).

Dataset Information

Expression and DNA methylation changes in human breast epithelial cells after bisphenol A exposure.

Publications

Expression and DNA methylation changes in human breast epithelial cells after bisphenol A exposure.

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