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Deciphering Cell-Specific Responses to Oncogenic Stress in the Liver

ABSTRACT: Each cell type responds uniquely to stress and fractionally contributes to global and tissue-specific stress responses. Hepatocytes, liver macrophages (MΦ), and sinusoidal endothelial cells (SEC) play functionally important and interdependent roles in adaptive processes such as wound healing, obesity, and tumor growth. Although these cell types demonstrate significant phenotypic and functional heterogeneity, their distinctions enabling disease-specific responses remain understudied. To address this, we developed a strategy for simultaneous isolation and quantification of these liver cell types based on antigenic cell surface marker expression in response to DEN and found that while there was only a marginal increase in hepatocyte number, MΦ and SEC populations were quantitatively increased. Global gene expression profiling of hepatocytes, MΦ and SEC identified characteristic gene “fingerprints” that define each cell type and their distinct physiological or oncogenic stress signatures. Integration of these cell-specific gene fingerprints with available hepatocellular carcinoma (HCC) patient microarray data demonstrates that the hepatocyte-specific response strongly correlates with the human HCC gene expression profile. Liver-specific MΦ and SEC gene signatures demonstrate significant alterations in inflammatory and angiogenic gene regulatory pathways, which may impact the hepatocyte response to oncogenic stress. Further validation confirms alterations in components of two key pathways, AP-1 and p53, that have been previously associated with HCC onset and progression. Our data reveal unique gene expression patterns that serve as molecular “fingerprints” for the cell-centric responses to pathologic stimuli in the distinct microenvironment of the liver. The technical advance highlighted in this study provides an essential resource for assessing hepatic cell-specific contributions to oncogenic stress, information that could unveil previously unappreciated molecular mechanisms for the cellular crosstalk that underlies the development of hepatic cancer.

ORGANISM(S): Mus musculus

PROVIDER: GSE67225 | GEO | 2015/09/20

SECONDARY ACCESSION(S): PRJNA279287

REPOSITORIES: GEO

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Project description:Each cell type responds uniquely to stress and fractionally contributes to global and tissue-specific stress responses. Hepatocytes, liver macrophages (M?), and sinusoidal endothelial cells (SEC) play functionally important and interdependent roles in adaptive processes such as wound healing, obesity, and tumor growth. Although these cell types demonstrate significant phenotypic and functional heterogeneity, their distinctions enabling disease-specific responses remain understudied. To address this, we developed a strategy for simultaneous isolation and quantification of these liver cell types based on antigenic cell surface marker expression in response to DEN and found that while there was only a marginal increase in hepatocyte number, M? and SEC populations were quantitatively increased. Global gene expression profiling of hepatocytes, M? and SEC identified characteristic gene “fingerprints” that define each cell type and their distinct physiological or oncogenic stress signatures. Integration of these cell-specific gene fingerprints with available hepatocellular carcinoma (HCC) patient microarray data demonstrates that the hepatocyte-specific response strongly correlates with the human HCC gene expression profile. Liver-specific M? and SEC gene signatures demonstrate significant alterations in inflammatory and angiogenic gene regulatory pathways, which may impact the hepatocyte response to oncogenic stress. Further validation confirms alterations in components of two key pathways, AP-1 and p53, that have been previously associated with HCC onset and progression. Our data reveal unique gene expression patterns that serve as molecular “fingerprints” for the cell-centric responses to pathologic stimuli in the distinct microenvironment of the liver. The technical advance highlighted in this study provides an essential resource for assessing hepatic cell-specific contributions to oncogenic stress, information that could unveil previously unappreciated molecular mechanisms for the cellular crosstalk that underlies the development of hepatic cancer. Total RNA isolated from each specific cell type (Hepatocyte (PH), Sinusoidal Endothelial Cell (SEC), and Macrophage (MP)) pooled from 3-4 DEN-treated mice and compared to their untreated counterparts.

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:Hepatocyte dedifferentiation is a major source of hepatocellular carcinoma (HCC), but its mechanisms are unknown. We explored the p73 expression in HCC tumors and studied the effects of transcriptionally active p73 (TAp73) in HCC cells. Expression profiles of p73 and patient clinical data were collected from the Genomic Data Commons (GDC) data portal and the TSVdb database, respectively. Global gene expression profiles were determined by pan-genomic 54K microarrays. The Gene Set Enrichment Analysis was used to identify TAp73-regulated gene sets. The effects of TAp73 were analyzed in monolayer cell culture, 3D-tumoroid and xenograft models in zebrafish using western blot, flow cytometry, fluorescence imaging, real-time polymerase chain reaction (RT-PCR), immunohistochemistry and morphological examination. TAp73 was significantly upregulated in HCC, and its high expression indicated poor patient survival. The induced expression of TAp73 caused landscape expression changes including genes involved in growth signaling, cell cycle, stress response, immunity, metabolism and development. HCC cells overexpressing TAp73 had lost hepatocyte lineage biomarkers including ALB, CYP3A4, AFP, HNF4α. In contrast, TAp73 upregulated genes promoting cholangiocyte lineage such as YAP, JAG1 and ZO-1, accompanied with an increase in metastatic ability. Our findings strongly suggest that TAp73 is a major promoter of malignant dedifferentiation of HCC cells Hepatocellular carcinoma (HCC) is a highly complex and heterogeneous type of cancer. Hepatocyte dedifferentiation is one of the important steps in the development of HCC. However, its molecular mechanisms are not well known. In this study, we report that TAp73 which is the major transcriptionally active form of p73 is overexpressed in HCC. Mechanically, TAp73 suppresses the expression of the hepatocyte markers including CYP3A4, AFP, ALB, HNF4a, while increasing the expression of several cholangiocyte markers in HCC cell lines. In conclusion, this report reveals a pro-oncogenic role for TAp73 in liver cancer.

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Deciphering Cell-Specific Responses to Oncogenic Stress in the Liver

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