Unknown,Transcriptomics,Genomics,Proteomics

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DNA methyltransferase inhibitor zebularine inhibits human hepatic carcinoma cells proliferation and induces apoptosis.

ABSTRACT: Hepatocellular carcinoma is one of the most common cancers in world wide. During tumorigenesis, tumor suppressor and cancer-related genes are commonly silenced by aberrant DNA methylation in their promoter regions. Zebularine [1-(β-ᴅ-ribofuranosyl)-1,2-dihydropyrimidin-2-one] acts as an inhibitor of DNA methylation and exhibits chemical stability and minimal cytotoxicity both in vitro and in vivo. In this study, we explore the effect and possible mechanism of action of zebularine on hepatocellular carcinoma cell line HepG2. Here, we demonstrated that zebularine exhibited antitumor activity on HepG2 cells by inhibiting cell proliferation and inducing apoptosis. Zebularine treatment down-regulated CDK2 and phosphorylation of retinoblastoma protein (RB), and up-regulated p21WAF/CIP1 and p53. We also found that zebularine treatment up-regulated phosphorylation of p44/42 MAPK. These results suggest that p44/42 MAPK pathway play a role in zebularine induced cell cycle arrest by regulating activity of p21WAF/CIP1 and Rb. Furthermore, we found that zebularine induced apoptosis. Although proapoptotic protein Bax levels were not affected, antiapoptotic protein Bcl-2 level was down-regulated with zebularine treatment. The data in the present study suggest that the action of the double-stranded RNA-dependent protein kinase (PKR) is involved in inducing apoptosis with zebularine. These results provide a novel mechanism of zebularine-induced cell growth arrest and apoptosis in hepatocellular carcinoma. Three each independent batches of zebuluarine-treated and control HepG2 cells were subjected to illumina Human methylation 450K Beadchip analysis.

ORGANISM(S): Homo sapiens

SUBMITTER: Kazuhiko Nakabayashi

PROVIDER: E-GEOD-42490 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Hepatocellular carcinoma (HCC) is a frequent cancer with poor prognosis and with limited possibilities for anti-cancer treatment. Evidence has recently accumulated suggesting that multiple signaling pathways are activated in human cancer. It has been recently shown by exosome sequencing of HCC that 161 putative driver genes are associated with 11 recurrently altered pathways, suggesting that we need to inhibit these multiple pathways for HCC therapy. THOC5, a member of transcription/export (TREX) complex, that plays a role in less than 1% of mRNA processing in normal cells such as fibroblasts or macrophages, is not required for maintenance of mature hepatocytes. In this study, we have examined the role of THOC5 in human HCC. Enhanced THOC5 expression was not observed in differentiation grading 1 (G1) human HCC, but 78% of G2 and G3 exhibited increased levels of THOC5. Furthermore, the 50% depletion of THOC5 in hepatocellular carcinoma cell lines, Huh7 and HepG2 causes lipid accumulation and apoptosis. Transcriptome analysis using THOC5 depleted Huh7 and HepG2 cells revealed that 1049 and 837 genes were downregulated upon depletion of THOC5 in Huh7 and HepG2 cells, respectively. Among these genes, 396 were commonly downregulated in both cell lines. Some of these, such as tissue inhibitor of metalloproteinase 3 (TIMP3), tripartite motif containing 24 (TRIM24), ribosomal protein S6 kinase polypeptide 3 (RPS6KA3) and transmembrane emp24-like trafficking protein 10 (TMED10) are known to be fine tuners for several signal transduction pathways. The expression of these proteins was correlated with the THOC5 expression level in HCC. To inhibit multiple signaling pathways we are currently examining the effects of a combination of siRNAs against THOC5 target genes in HCC cell lines. Our data suggest that THOC5, which controls a set of genes that are involved in HCC malignancy can be a potential biomarker for HCC. In addition, THOC5 target gene, TMED10 may also be a novel biomarker of HCC. Furthermore, the suppression of the THOC5 gene per se or multiple THOC5 target genes may represent a novel strategy for cancer therapy. Huh7 and HepG2 cells were infected with lentiviral THOC5 and control shRNAs. Five days after infection, total RNAs were isolated and subjected to microarray analysis.

Project description:Molecular targeted therapy has shown promise as a treatment for advanced hepatocellular carcinoma (HCC). Sorafenib, a multikinase inhibitor, recently received FDA approval for the treatment of advanced HCC. However, although sorafenib is well tolerated, concern for its safety has been expressed. Celecoxib (CelebrexM-BM-.) is a selective cyclooxygenase-2 (COX-2) inhibitor wich exhibits antitumor effects in human HCC cells. The present study examined the interaction between celecoxib and sorafenib in two human liver tumor cell lines HepG2 and Huh7. Our data showed that each inhibitor reduced cell growth and the combination of celecoxib with sorafenib synergistically inhibited cell growth and increased apoptosis. To better understand the molecular mechanisms underlying the synergistic antitumor activity of combination, we investigated the expression profile of the combination-treated liver cancer cell lines, using microarray analysis. Combination treatment significantly altered expression levels of 1,986 and 2,483 transcripts in HepG2 and Huh7 cells, respectively. Genes, functionally involved in cell death, signal transduction and regulation of transcription were predominantly up-regulated, while genes implicated in metabolism, cell cycle control and DNA replication and repair were mainly down-regulated upon treatment. However, combination-treated HCC cell line displayed specificity in the expression and activity of crucial factors involved in hepatocarcinogenesis. The altered expression of some of these genes was confirmed by semiquantitative and quantitative RT-PCR and by Western blotting. Many novel genes emerged from our transcriptomics analyses, and further functional analyses may determine whether these genes can serve as potential molecular targets for more effective anti-HCC strategies. To identify new potential mechanisms of combined action of celecoxib and sorafenib, their effects on global gene expression in both cell lines were investigated and compared using the DNA microarray technology. Agilent 44K Human Whole Genome Oligonucleotide Microarrays (containing ~44,000 genes) were used to identify global gene expression changes in the HepG2 and Huh7 hepatocellular carcinoma (HCC) cell lines, following simultaneous treatment with 50 M-BM-5M celecoxib and 7.5 M-BM-5M sorafenib for 48 hours. All microarray experiments (a total of four) were performed in duplicates applying dye-swaps to avoid labeling bias.

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DNA methyltransferase inhibitor zebularine inhibits human hepatic carcinoma cells proliferation and induces apoptosis.

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