Project description:Background - Hepatocellular carcinomas (HCCs) are heterogeneous tumors with respect to etiology, cell of origin and biology. The course of the disease is unpredictable and is in part dependent on the tumor microenvironment. One of the microenvironmental factors is hypoxia, which is known to promote aggressiveness in other malignant tumors. We hypothesized that certain regions in HCC exist with chronic hypoxia and a characteristic gene expression pattern. Moreover, during the development of HCC there is an important contribution of this chronic hypoxia on prognosis via this gene expression. Until now, most research has been performed in acute hypoxic models (< 24 hours). Methods – Human hepatoblastoma cells HepG2 were cultured in either normoxic (20% O2) or hypoxic (2% O2) conditions for 72 hrs, the time it takes to adapt to chronic hypoxia. After 3 days the cells were harvested and analyzed by microarray technology. The highly significant differentially expressed genes were selected and used to assess the clinical value of our in vitro chronic hypoxia gene signature in four published patient studies. Three of these independent microarray studies on HCC patients were used as training sets to determine a minimal prognostic gene set and one study was used for validation. Gene expression analysis and correlation with clinical outcome was assessed with the bioinfomatic method of Goeman et al (). Results – In the HepG2 cells, 3592 genes were differentially expressed in cells cultured at 2% oxygen for 72 hrs. Out of these, 265 showed a high significant change (2-fold change and p=0.0001). The level of gene expression after 72 hrs was different from the acute hypoxic response (during the first 24 hours) and represented chronicity. Using computational methods we identified 7 out of the 265 highly significant genes that showed correlation with prognosis in all three different training sets and this was independently validated in a 4th dataset. With our approach we could include the largest number of HCC patients in one single study. Conclusion – We identified a 7-gene signature, which is associated with chronic hypoxia and predicts prognosis in patients with HCC. In the future this signature could be used as a diagnostic tool. In addition, chronic hypoxia gene expression information can be used in the search for new therapeutic targets. Two conditions were compared and each sample has a biological replicate. Samples are hybridized in dye-swap, resulting in 4 hybridizations.

Project description:An integrative transcriptomics analysis was performed to evaluate the clinical relevance of genes associated with hepatocyte differentiation in human hepatocellular carcinoma (HCC). The well-established HepaRG cell line model was used to define a gene expression signature reflecting the status of tumor hepatocyte differentiation. This signature was able to stratify HCC patients into clinically relevant molecular subtypes. Then, a minimal subset of 7 differentiation-associated genes was identified to predict a poor prognosis in several cancer datasets. Hepatocellular carcinoma (HCC) is a deadly cancer worldwide as a result of a frequent late diagnosis which limits the therapeutic options. Tumor progression is correlated with a dedifferentiation of hepatocytes, the main parenchymal cells in the liver. Here, we hypothesized that the level of expression of genes reflecting the differentiation status of tumor hepatocytes could be clinically relevant in defining subsets of patients with variable clinical outcomes. To test this hypothesis, an integrative transcriptomic approach was used to stratify a cohort of 139 HCC patients based on a gene expression signature established using a well-controlled in vitro model of tumor hepatocyte differentiation in HepaRG cell line. First, we validated the HepaRG model by identifying a robust gene expression signature associated with hepatocyte differentiation and liver metabolism. This signature was able to distinguish specific developmental stages in mice. More importantly, the signature identified a subset of human HCC associated with a poor prognosis and cancer stem cell features. By using an independent HCC dataset (TCGA), a minimal subset of 7 differentiation-related genes was shown to predict a reduced overall survival, not only in patients with HCC but also in other types of cancers (e.g. kidney, pancreas, skin). In conclusion, the study demonstrates that genes reflecting the differentiation status of tumor hepatocytes are clinically relevant for predicting the prognosis of HCC patients.

Project description:Background - Hepatocellular carcinomas (HCCs) are heterogeneous tumors with respect to etiology, cell of origin and biology. The course of the disease is unpredictable and is in part dependent on the tumor microenvironment. One of the microenvironmental factors is hypoxia, which is known to promote aggressiveness in other malignant tumors. We hypothesized that certain regions in HCC exist with chronic hypoxia and a characteristic gene expression pattern. Moreover, during the development of HCC there is an important contribution of this chronic hypoxia on prognosis via this gene expression. Until now, most research has been performed in acute hypoxic models (< 24 hours). Methods – Human hepatoblastoma cells HepG2 were cultured in either normoxic (20% O2) or hypoxic (2% O2) conditions for 72 hrs, the time it takes to adapt to chronic hypoxia. After 3 days the cells were harvested and analyzed by microarray technology. The highly significant differentially expressed genes were selected and used to assess the clinical value of our in vitro chronic hypoxia gene signature in four published patient studies. Three of these independent microarray studies on HCC patients were used as training sets to determine a minimal prognostic gene set and one study was used for validation. Gene expression analysis and correlation with clinical outcome was assessed with the bioinfomatic method of Goeman et al (). Results – In the HepG2 cells, 3592 genes were differentially expressed in cells cultured at 2% oxygen for 72 hrs. Out of these, 265 showed a high significant change (2-fold change and p=0.0001). The level of gene expression after 72 hrs was different from the acute hypoxic response (during the first 24 hours) and represented chronicity. Using computational methods we identified 7 out of the 265 highly significant genes that showed correlation with prognosis in all three different training sets and this was independently validated in a 4th dataset. With our approach we could include the largest number of HCC patients in one single study. Conclusion – We identified a 7-gene signature, which is associated with chronic hypoxia and predicts prognosis in patients with HCC. In the future this signature could be used as a diagnostic tool. In addition, chronic hypoxia gene expression information can be used in the search for new therapeutic targets.

Project description:During embryogenesis, Hepatocyte Growth Factor (HGF) elicits a distinctive morphogenetic program, the invasive growth, by the activation of MET, whose aberrant activation in cancer drives metastatic progression. Aim of this work is to define and characterize the transcriptional signature of invasive growth, and to verify its activation in human cancers. Global expression profiling was carried out on mouse liver stem/progenitor cells (MLP-29) stimulated for different times, one, six and twenty-four hours, in vitro with HGF to define the invasive growth signature. Meta-analysis of human cancer microarray data was carried out to dissect the transcriptional modules of the invasive growth that are aberrantly activated during carcinogenesis of hepatocellular carcinoma. Differential expression analysis identified 2643 regulated genes by HGF, the invasive growth signature, subdivided in 11 gene expression clusters revealing waves of time coded transcriptional regulation. Those waves have been in-silico associated with the regulative role of the transcriptional unit of Rela/Nfkbia and Fos/Jun and biological features recapitulating the physiological invasive growth phenotype observed in cell line, such as cell motility and scattering, cellular proliferation and protection from apoptosis, cytoskeletal rearangement. Genomic meta-analysis on hepatocellular carcinoma identified of a core genes set (323 gene symbols), consistently regulated between MLP-29 and human tumors and significantly associated with cancer aggressiveness and metastasis p.val < 1*10-6, HR=5.404 CI= 2.570-11.365. The invasive growth signature recapitulates the physiopatological program driven by the stimulation of HGF in normal embryonic liver cells and its activity is observed in HCC as well as in several other tumors. This signature is associated with neoplastic progression and reliably predicts human HCC disease outcome, suggesting the involvement of the invasive growth and cancer in cancer progression. These results prompt the future application of anti-met target therapies in HCC and the application of the signature for both prognostic and predictive purposes.

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A genomic enhancer signature associates with Hepatocellular Carcinoma prognosis

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