Unknown,Transcriptomics,Genomics,Proteomics

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Oncogenic activation of RNA binding proteins and c-Myc signaling in hepatocellular carcinoma

ABSTRACT: Global transcriptomic alterations of both coding and non-coding RNA species are a ubiquitous feature associated with human cancers including hepatocellular carcinoma (HCC). Dysregulation of RNA-binding proteins (RBPs), the key regulators of RNA processing, is one mechanism in which cancer cells select to promote tumorigenesis. We analyzed genomic alterations amongst a family of more than 800 mRNA RBPs (mRBPs) in 1,225 clinical specimens from HCC patients and found that RBPs are significantly activated through gene amplification in a subset of tumors with poor prognosis, suggesting their potential oncogenic roles in HCC progression. Amongst the top candidates, RD binding protein (RDBP) was further characterized for its oncogenic role and effects on the HCC transcriptome. While the activation of RDBP induced an oncogenic phenotype, the abrogation of RDBP in HCC cells significantly decreased cancer associated phenotypes such as cell proliferation, migration/invasion and tumorigenicity in vivo. Further microarray analyses revealed that RDBP-dependent genes were tumor-related with a significant enrichment for c-Myc targets, suggesting interplay between RDBP and c-Myc signaling. Similar data were also found in HCC clinical specimens where c-Myc amplification was uncommon. Consistently, the RDBP-dependent c-Myc target gene signature was able to predict HCC patient survival in two independent cohorts of more than 400 patients. Taken together, our results suggest that oncogenic activation of RDBP is a novel mechanism that contributes to global transcriptome imbalance that is selective for the activation of c-Myc oncogenic signaling in HCC. We used microarray analysis to determine the affects of siRNA mediated RDBP knockdown in HCC transcriptome in cell lines. Hep3b and Huh1 cells were transfected with RDBP or scramble control siRNA for 48 hours in quadruplicates. Quality control using Spearman or Pearson correlation removes outliers resulting in triplicates for each group

ORGANISM(S): Homo sapiens

SUBMITTER: Hien Dang

PROVIDER: E-GEOD-73219 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Development of targeted therapy for hepatocellular carcinoma (HCC) remains a major challenge. We have recently identified an elevated expression of the fifth subunit of COP9 signalosome (CSN5) in early HCC as compared to dysplastic stage. In the present study, we explored the possibility of CSN5 being a potential therapeutic target for HCC. We demonstrate that CSN5 knockdown by small interfering (si) RNA caused a block in cell proliferation and cell cycle progression, and induced apoptosis of HCC cells in vitro. The transcriptomic analysis of CSN5 knockdown signature by microarray showed that the anti-proliferative effect was driven by a common subset of molecular alterations including downregulation of CDK6 or ITGB1, which are involved in cell cycle regulation or tumor invasion and functionally interconnected with key oncogenic regulators such as TGFβ1 and MYC. Western blot assay showed that CSN5 depletion significantly increases the phosphorylation of Smad2/3 and decreases the expression of ITGB1, CDK6 and cyclin D1 proteins, restoring the tumor suppressive function of RB and thereby contributing to inhibition of cell cycle progression. In addition, CSN5 knockdown increased the expression of Bak but decreased the level of Bcl-2, subsequently leading to apoptosis through the activation of caspase-3. A chemically modified variant of CSN5 siRNA was then selected for in vivo application based on the growth inhibitory effect and minimal induction of unwanted immune response. Systemic delivery of the CSN5 3/8 variant by stable-nucleic-acid-lipid-particles (SNALP) significantly suppressed the tumor growth in Huh7-luc+ orthotopic xenograft model. Taken together, these results indicate that CSN5 plays a pivotal role in HCC pathogenesis and maybe an attractive molecular target for systemic HCC therapy. Huh7 and HepG2 cells were treated with CSN5 siRNA and negative control siRNA for 48 hours and subjected to Illumina microarray analysis. 4 replicates each.

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Oncogenic activation of RNA binding proteins and c-Myc signaling in hepatocellular carcinoma

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