Unknown,Transcriptomics,Genomics,Proteomics

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Gene Expression Data for female C57BL/6, Mdr2-KO and Mdr2-KO/IL6-KO at the age of 14 months

ABSTRACT: Chronic inflammation is a common underlying condition associated with tumor development, accounting for approximately 20% of human cancers. This association is especially apparent in Hepatocellular carcinoma (HCC), which often develops on the background of chronic hepatitis and hepatic fibrosis, slowly unfolding on a background of chronic inflammation. HCC is one of the most common tumors worldwide, exhibiting a very poor prognosis and high mortality rate with limited available therapeutic tools. The etiology of liver cancer is well known, however there is still a lack of precise knowledge about pathogenesis of HCC. IL-6 have been shown to be of importance for liver protection and prevention of liver injury in animal models of acute sclerosing cholangitis and correlate with increased HCC in human patients. Using a murine model of chronic cholangitis based on the ablation of the Mdr2 gene, this study has examined the role of IL-6 signaling in chronic hepatitis and in the subsequent development of liver cancer. The main observations of this study are that IL-6 signaling in female Mdr2-KO mice protects from the development of liver injury and fibrosis, but simultaneously reduced tumor initiation. To reveal the affected molecular pathways that lead to increased cholestasis and bile acid ?induced liver injury, and increased tumorigenesis in the female IL-6 deficient Mdr2-KO/IL6-KO mice, we performed gene array analysis and identified distinct classes of differentially-expressed genes in these mice. We performed genome-scale gene expression profiling by Affymetrix analysis on tumor-free livers samples from Mdr2-KO, Mdr2-KO/IL6-KO, and wild type C57BL/6 mice at the age of 14 months.

ORGANISM(S): Mus musculus

SUBMITTER: Jonathan Axelrod

PROVIDER: E-GEOD-37559 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Chronic liver inflammation precedes the majority of hepatocellular carcinomas (HCC). Here, we explore the connection between chronic inflammation and DNA methylation in the liver at the late precancerous stages of HCC development in Mdr2/Abcb4-knockout (Mdr2-KO) mice, a model of inflammation-mediated HCC. Using methylated DNA immunoprecipitation (MeDIP) followed by hybridization with Agilent CpG Islands (CGIs) microarrays we found specific CGIs in 76 genes which were hypermethylated in the Mdr2-KO liver compared to age-matched controls. Methylation of thirty among these genes was highly specific to the studied HCC model. We revealed that in most tested cases, the observed hypermethylation resulted from an age-dependent decrease of methylation of the specific CGIs in control livers with no decrease in mutant mice. Chronic inflammation did not change global levels of DNA methylation in Mdr2-KO liver, but caused a 2-fold decrease of the global 5-hydroxymethylcytosine level in mutants compared to controls. This decrease could result from a less efficient age-dependent demethylation of specific CpG sites in the liver of Mdr2-KO mutants, as described above. Expression of some tested hypermethylated genes was increased in Mdr2-KO livers compared to controls (28%), others were either similarly expressed (44%), or not expressed in the liver (28%). Liver cell fractionation revealed, that the relative hypermethylation of specific CGIs in Mdr2-KO compared to control livers affected either hepatocyte, or non-hepatocyte, or both fractions. There was only episodic correlation between changes of gene methylation and expression in cell fractions. Conclusion: Chronic liver inflammation causes hypermethylation of specific CGIs, which may affect both hepatocytes and non-hepatocyte liver cells. These changes may serve as markers of an increased regenerative activity and of a precancerous microenvironment in the chronically inflamed liver. Two-condition experiment, Mdr2-KO vs Mdr2-/+ liver tissue from 12m-old male FVB strain mice. Biological replicates: 3 control replicates, 3 knockout replicates.

Project description:Mouse models of hepatocellular carcinoma (HCC) simulate specific subgroups of human HCC. We investigated hepatocarcinogenesis in Mdr2-KO mice, a model of inflammation-associated HCC, using gene expression profiling and immunohistochemical analyses. Gene expression profiling demonstrated that although Mdr2-KO mice differ from other published murine HCC models, they share several important deregulated pathways and many coordinately differentially expressed genes with human HCC datasets. Analysis of genome positions of differentially expressed genes in liver tumors revealed a prolonged region of down-regulated genes on murine chromosome 8 in three of the six analyzed tumor samples. This region is syntenic to human chromosomal regions that are frequently deleted in human HCC and harbor multiple tumor suppressor genes. Real-time RT-PCR analysis of 16 tumor samples confirmed down-regulation of several tumor suppressors in most tumors. We demonstrate that in the aged Mdr2-KO mice, cyclin D1 nuclear level is increased in dysplastic hepatocytes that do not form nodules; however, it is decreased in dysplastic nodules and in liver tumors. We found that this decrease is mostly at the protein, rather than the mRNA level. These findings raise the question on the role of cyclin D1 at early stages of hepatocarcinogenesis in the Mdr2-KO HCC model. Furthermore, we show that most liver tumors in Mdr2-KO mice were characterized by the absence of b-catenin activation. In conclusion, the Mdr2-KO mouse may serve as a model for b-catenin-negative subgroup of human HCCs characterized by low nuclear cyclin D1 levels in tumor cells and by down-regulation of multiple tumor suppressor genes. Experiment Overall Design: The liver RNA samples from six Mdr2-KO tumors, six non-tumorous liver tissues (four matched and two unmatched), as well as from three control heterozygous mice at 16 months of age were subjected to gene expression profiling using the genome scale Affymetrix Mouse Genome 430 2.0 Array.

Dataset Information

Gene Expression Data for female C57BL/6, Mdr2-KO and Mdr2-KO/IL6-KO at the age of 14 months

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