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The DNA methylation profile of liver tumors in C3H mice and identification of differentially methylated regions involved in the regulation of tumorigenic genes

ABSTRACT: Background: C3H mice have been frequently used in cancer studies as animal models of spontaneous liver tumors and chemically induced hepatocellular carcinoma (HCC). Epigenetic modifications, including DNA methylation, are among pivotal control mechanisms of gene expression leading to carcinogenesis. Although information on somatic mutations in liver tumors of C3H mice is available, epigenetic aspects are yet to be clarified. Methods: We performed next generation sequencing-based analysis of DNA methylation and microarray analysis of gene expression to explore genes regulated by DNA methylation. Overlaying these data, we selected cancer-related genes whose expressions are inversely correlated with DNA methylation levels in the associated differentially methylated regions (DMRs) located around transcription start sites (TSSs) (promoter DMRs). We further assessed mutuality of the selected genes for expression and DNA methylation in human HCC using the Cancer Genome Atlas (TCGA) database. Results: We obtained data on genome-wide DNA methylation profiles in the normal and tumor livers of C3H mice. We identified promoter DMRs of genes which are reported to be related to cancer and whose expressions are inversely correlated with the DNA methylation, including Mst1r, Slpi and Extl1. The association between DNA methylation and gene expression was confirmed using a DNA methylation inhibitor 5- aza-2'-deoxycytidine (5-aza-dC) in Hepa1c1c7 cells and Hepa1-6 cells. Overexpression of Mst1r in Hepa1c1c7 cells illuminated a novel downstream pathway via IL-33 upregulation. Database search indicated that gene expressions of Mstr1 and Slpi are upregulated and the TSS upstream regions are hypomethylated also in human HCC. These results suggest that DMRs, including those of Mst1r and Slpi, are involved in liver tumorigenesis in C3H mice, and also possibly in human HCC. Conclusions: Our study clarified genome wide DNA methylation landscape of C3H mice. The data provide useful information for further epigenetic studies of mice models of HCC. The present study particularly proposed novel DNA methylation-regulated pathways for Mst1r and Slpi, which may be applied not only to mouse HCC but also to human HCC.

ORGANISM(S): Mus musculus

PROVIDER: GSE111420 | GEO | 2018/04/04

REPOSITORIES: GEO

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Project description:Purpose: Aberrantly methylated DNA are hallmarks for many cancers, HCC included. Tumor shed its DNA into circulation stream, and serum DNA methylation analysis is a less-invasive and accessable way to judge the primary tumor status. The goals of this study are to compare DNA methylation profiling in serum cell-free DNA from different stages of HCC progression including healthy control, chronic HBV carrier, HBV-related liver Cirrhosis and HCC, to establish HCC development-related aberrnat DNA methylation patterns. Methods: MBD methylCap/seq was carried out to screen differentially methylated CpG islands in serum cell-free DNA on four different stage of HBV-related HCC development. MSP and multiplex-BSP validation was performed using independent serum DNA or tumor and adjacent tissues. Results: Using a MBD methylCap/seq platform, we produced 33- to 37- million raw reads per sample and mapped them, in about half of the raw reads, to human genome(build h19) in the serum cf DNA of healthy control, HBV carrier, HBV cirrhosis and HCC. The mapped reads formed 180k to 260k peaks per sample, with 160 k common peaks shared by four samples. After subtraction of the common peaks, there left 51k, 107k and 78 k DMRs representing hypermethylations, in HBV carrier, HBV cirrhosis and HCC, respectively. We define those DMRs as early, middle and late when these DMRS occurred and maintained in HBV carrier, HBV cirrhosis and HCC, which including 27k, 24k and 19k DMRs, corresponding to 1,416, 1,337, 1,006 genes. GO analysis of them revealed gene categories and pathways associated with tumorogenenisis related process Conclusions: Our study represents the first detailed analysis of serum cf-DNA methylation profiling in the progression of HBV related HCC development. The processed data analysis here offers a comprehensive evaluation of DNA methylation in serum cf DNA. We conclude that MBD methylCap/seq based methylation profiling would benefit epigenetic research in HCC.

Project description:To further our understanding of the role of DNA methylation in development, Methylated DNA Immunoprecipitation (MeDIP) was used in conjunction with a NimbleGen promoter plus CpG island array to identify Tissue and Developmental Stage specific Differentially Methylated DNA Regions (T-DMRs and DS-DMRs) on a genome-wide basis. Four tissues (brain, heart, liver, and testis) from C57BL/6J mice were analyzed at three developmental stages (15 day embryo, E15; new born, NB; 12 week adult, AD). Almost 5,000 adult T-DMRs and 10,000 DS-DMRs were identified. Surprisingly, almost all DS-DMRs were tissue specific (i.e., methylated and ummenthylated in one or more non-overlapping tissues), indicating that the vast majority of unique sequence DNA methylation has tissue specificity. Also, many DS-DMRs were methylated at early development stages (E15 and NB) but unmethylated in adult, indicating “demethylation” has a prominent role in tissue differentiation. The pattern of DNA methylation in adult testis was dramatically different from somatic tissues in many aspects, mostly notably with a very strong bias of methylation in non-CpGi (CpG island) promoter regions (94%). Although the majority of T-DMRs and DS-DMRs tended to be in non-CpGi promoter regions, a relatively large number were also located in CpGi in promoter, intra-genic and inter-genic regions (>15% of all CpGi). Gene Ontology analysis of genes with methylation in non-CpGi promoters indicates enrichment of genes related to membrane proteins and G-protein coupled receptors. Our data also suggest regulatory roles of DNA methylation outside of promoter regions and in alternative promoter selection. Overall, our studies indicate that change in DNA methylation during development is a dynamic, widespread and tissue-specific process involving both DNA methylation and demethylation. Comparison of DNA methylation across 3 developmental stages (15 day embryo, newborn, and adult) for four tissues (brain, heart, liver and testis)

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The DNA methylation profile of liver tumors in C3H mice and identification of differentially methylated regions involved in the regulation of tumorigenic genes

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