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Epigenomic Analysis of Aberrantly Methylated Genes in Colorectal Cancer

ABSTRACT: Determination of the profile of genes commonly aberrantly methylated in colorectal cancer (CRC) has substantial potential value for diagnostic and therapeutic application. However, our knowledge of the DNA methylation pattern in CRC is currently limited. Therefore, we analyzed the methylation profile of 27,578 CpG sites spanning more than 14,000 genes in CRC and in adjacent normal mucosa using beadchip array-based technology. We identified 621 CpG sites located in promoter region and CpG islands that were significantly hypermethylated in CRC compared to normal mucosa. Genes on chromosome 18 showed promoter hypermethylation most frequently. According to gene ontology analysis, the most common biologically relevant class of genes affected by methylation was the class associated with the cadherin signaling pathway. In comparison with genome-wide expression array, mRNA expression was more like to be down-regulated in the genes demonstrating promoter hypermethylation, although this was not statistically significant. We validated 10 CpG sites that were shown to be hypermethylated in the array studies (ADHFE1, BOLL, SLC6A15, ADAMTS5, TFPI2, EYA4, NPY, TWIST1, LAMA1, GAS7) and 2 CpG sites showing hypomethylaion (MAEL, SFT2D3) in CRC compared to normal mucosa using pyrosequencing. The methylation status measured by pyrosequencing was consistent with the methylation array data. In conclusion, we have shown that methylation profiling based on beadchip arrays is an effective method for screening for aberrantly methylated genes in CRC. In addition, we identified novel methylated genes that are candidate diagnostic or prognostic markers for CRC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE17648 | GEO | 2009/08/18

SECONDARY ACCESSION(S): PRJNA118597

REPOSITORIES: GEO

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Project description:Background an Aim: Epigenetics are thought to play a major role in the carcinogenesis of patients that develop multiple colorectal cancers (CRC) in the non-hereditary setting. Previous studies have suggested concordant DNA hypermethylation between tumor pairs. However, only a few methylation markers have been analyzed. This study was aimed at describing the underlying epigenetic signature that differentiates multiple from solitary colorectal cancer tumors using a genome-scale DNA methylation profiling. Patients and Methods: We used a population-based cohort (EPICOLON II) of 12 patients with synchronous CRC and 29 age- sex- and tumor location-paired solitary CRC patients. DNA methylation profiling was performed using the Illumina Infinium HM27 DNA methylation assay. The most significantly hypermethylated CpG sites results were validated by Methylight. Tumors samples were also analyzed for the CpG Island Methylator Phenotype (CIMP) using the Infinium DNA methylation data; KRAS and BRAF mutations; microsatellite instability; and immunohistochemistry for MLH1/MSH2/MSH6/PMS2. Functional annotation clustering of differentially methylated genes between multiple and solitary CRCs was performed. Results: We identified 102 CpG sites that showed significant DNA hypermethylation in multiple versus solitary tumors (difference in M-NM-2 value >0.1 and p<0.05). Methylight assays validated the array results for 4 selected significantly hypermethylated genes (MAP1B, HTRA1, ALOX15, TIMP3) identified in the profiling (p=0.0002). Based on the Infinium data, 8/12 (66.6%) of multiple tumors were classified as CIMP-high, as compared to 5/29 (17%) solitary tumors (p=0.004). CIMP-high tumors displayed significant hypermethylation in 301 CpG sites (difference in M-NM-2 value >0.1; p value <0.05). Interestingly, 76/102 (74.5%) of the hypermethylated CpG sites found in multiple vs. solitary tumors were also seen to be hypermethylated in CIMP-H tumors. Functional analysis of hypermethylated genes found in multiple vs. solitary tumors showed the presence and enrichment of genes involved in different tumorigenic functions. Conclusions: Multiple colorectal cancers are associated with a distinct methylation phenotype, with a close association between tumor multiplicity and CIMP-high. Our results may be important to unravel the underlying mechanism of tumor multiplicity in the non-hereditary scenario, and provide novel potential biomarkers for identifying high-risk patients and tailoring surveillance strategies. We used a population-based cohort (EPICOLON II) of 12 patients with synchronous CRC and 29 solitary CRC patients. DNA methylation profiling was performed using the Illumina Infinium HM27 DNA methylation assay.

Project description:Genetic abnormalities of cholangiocarcinoma (CCA) have been widely studied; however, epigenomic changes related to cholangiocarcinogenesis have been less well characterized. We have profiled the DNA methylomes of 28 primary CCA and six matched adjacent normal tissues using Infinium’s HumanMethylation27 BeadChips with the aim of identifying gene sets aberrantly epigenetically regulated in CCA. Using a linear model for microarray data we identified 1610 differentially methylated autosomal CpG sites with 809 CpG sites (representing 603 genes) being hypermethylated and 801 CpG sites (representing 712 genes) being hypomethylated in CCA versus adjacent normal (false discovery rate ? 0.05). Gene Ontology and Gene Set Enrichment analyses identified gene sets significantly associated with hypermethylation at linked CpG sites in CCA including homeobox genes and target genes of PRC2, EED, SUZ12 and Histone H3 trimethylation at lysine 27. We confirmed frequent hypermethylation at the homeobox genes HOXA9 and HOXD9 by bisulfite pyrosequencing in a larger cohort of CCA (n = 103). Our findings indicate a key role for hypermethylation of multiple CpG sites at genes associated with a stem cell-like phenotype as a common molecular aberration in CCA. These data have implications for CCA carcinogenesis, as well as possible novel treatment options using histone methyltransferase inhibitors. Methods: Thirty-two primary CCA, 6 matched adjacent normal, 5 CCA cell lines and an immortal biliary cell line were analyzed for DNA methylation profiles using the Infinium HumanMethylation27 BeadChip. Differential methylation was statistically analyzed using LIMMA. Specific functional terms and Gene Set Enrichment Analysis were performed to identify specific function of aberrantly methylated genes. Results: We identified 711 and 590 autosomal CpG sites as being hypermethylated and hypomethylated representing 527 and 521 genes, respectively, in CCA compared to adjacent normal (false discovery rate 0.05). A number of gene sets were significantly associated with hypermethylation at linked CpG sites in CCA including homeobox genes and the target genes of PRC2, EED, SUZ12, and H3K27me3, whereas target genes of NOS and OCT4 were hypomethylated at linked CpG sites in tumors. Frequent aberrant DNA methylation at HOXA9 and HOXD9 was confirmed by bisulfite pyrosequencing in a larger cohort of CCA (n = 107). Conclusions: This is the first report of a DNA methylation profile of multiple CpG sites at genes associated with a stem cell-like phenotype as a common molecular aberration in CCA. These data have implications for CCA carcinogenesis, as well as possible novel treatment options using histone methyltransferase inhibitors. Array-based methylation profiling was performed using the Infinium HumanMethylation27 BeadChip in 28 primary cholangiocarcinomas and six matched adjacent normal tissues. The reproducibility of the Infinium HumanMethylation27 BeadChips was evaluated using five technical replicates of the ovarian cancer cell line PEO1. Differential methylation cutoff was estimated from five technical replicates by bootstrap resampling and set at ?? ? 0.15 corresponding to a FDR ? 0.05.

Project description:Background an Aim: Epigenetics are thought to play a major role in the carcinogenesis of patients that develop multiple colorectal cancers (CRC) in the non-hereditary setting. Previous studies have suggested concordant DNA hypermethylation between tumor pairs. However, only a few methylation markers have been analyzed. This study was aimed at describing the underlying epigenetic signature that differentiates multiple from solitary colorectal cancer tumors using a genome-scale DNA methylation profiling. Patients and Methods: We used a population-based cohort (EPICOLON II) of 12 patients with synchronous CRC and 29 age- sex- and tumor location-paired solitary CRC patients. DNA methylation profiling was performed using the Illumina Infinium HM27 DNA methylation assay. The most significantly hypermethylated CpG sites results were validated by Methylight. Tumors samples were also analyzed for the CpG Island Methylator Phenotype (CIMP) using the Infinium DNA methylation data; KRAS and BRAF mutations; microsatellite instability; and immunohistochemistry for MLH1/MSH2/MSH6/PMS2. Functional annotation clustering of differentially methylated genes between multiple and solitary CRCs was performed. Results: We identified 102 CpG sites that showed significant DNA hypermethylation in multiple versus solitary tumors (difference in β value >0.1 and p<0.05). Methylight assays validated the array results for 4 selected significantly hypermethylated genes (MAP1B, HTRA1, ALOX15, TIMP3) identified in the profiling (p=0.0002). Based on the Infinium data, 8/12 (66.6%) of multiple tumors were classified as CIMP-high, as compared to 5/29 (17%) solitary tumors (p=0.004). CIMP-high tumors displayed significant hypermethylation in 301 CpG sites (difference in β value >0.1; p value <0.05). Interestingly, 76/102 (74.5%) of the hypermethylated CpG sites found in multiple vs. solitary tumors were also seen to be hypermethylated in CIMP-H tumors. Functional analysis of hypermethylated genes found in multiple vs. solitary tumors showed the presence and enrichment of genes involved in different tumorigenic functions. Conclusions: Multiple colorectal cancers are associated with a distinct methylation phenotype, with a close association between tumor multiplicity and CIMP-high. Our results may be important to unravel the underlying mechanism of tumor multiplicity in the non-hereditary scenario, and provide novel potential biomarkers for identifying high-risk patients and tailoring surveillance strategies.

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Epigenomic Analysis of Aberrantly Methylated Genes in Colorectal Cancer

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