Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Expression profiling of primary glioma samples

ABSTRACT: Background: Signaling by receptor tyrosine kinases (RTK) is frequently dysregulated in gliomas. Inter-individual variability in the causes for dysregulated RTK signaling may have hampered the efficacy of targeted therapies. Using gene expression modules around key regulators in the RAS-RAF-MEK-MAPK cascade and in the phosphatidylinositol 3-kinase-AKT pathways, we developed a âRMPAâ clustering scheme to distinguish gliomas with varying extents of RTK signaling. Results: We identified gene modules consistently co-expressed with NF1 (NF1-M), Sprouty (SPRY-M) and PTEN (PTEN-M) in gliomas. Their signatures enabled robust clustering of adult diffuse gliomas of WHO grades II-IV into RMPAhigh and RMPAlow phenotypes in a morphology-independent manner. In five independent data sets from three continents containing more than 1500 adult diffuse gliomas, RMPAhigh gliomas were associated with poor prognosis while RMPAlow gliomas were not. The RMPAhigh and RMPAlow glioma subtypes showed distinct levels of the activities of RAS-RAF-MEK-MAPK cascade and PI3K-AKT pathway and harbored unique sets of genomic alterations in the RTK signaling-related genes. The RMPAhigh gliomas contained large numbers of immature vessel cells and tumor associated macrophages and both cell types expressed high levels of pro-angiogenic RTKs including MET, VEGFR1, KDR, EPHB4 and NRP1. Conclusion: Inter-glioma variability in RTK signaling activities can be defined using the RMPA clustering scheme. The combined signatures of NF1-M, SPRY-M and PTEN-M reflect RTK signaling activity both in the glioma cells and in the glioma microenvironment. Our data show that RTK signaling in the glioma microenvironment may play a pivotal role in glioma progression. Transcriptome data from 22 fresh gliomas (2 astrocytoma II, 1 oligodendrocytoma II, 7 oligoastrocytoma II, 4 anaplastic oligoastrocytoma III and 8 GBM) were obtained using Affymetrix Human Gene 1.0 ST Array. Unsupervised hierarchical clustering of the expression data for the SPRY-M, NF1-M and PTEN-M was performed on these transcriptome data to identify samples with RMPAhigh or RMPAlow signature.

ORGANISM(S): Homo sapiens

SUBMITTER: Xiaolong Fan

PROVIDER: E-GEOD-74462 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Gliomas are aggressive primary brain tumors, presenting surgery limitations due to their highly infiltrative potential. The expression of Angiotensin II (Ang II) receptors in human astrocytomas was previously associated with a poor prognosis. Accordingly, this study was undertaken to reveal the molecular mechanisms underlying Ang II actions in gliomas through the transcriptomic analysis of glioma cells exposed to Ang II. C6 glioma cells were treated with Ang II and specific antagonists of AT1 and AT2. Total RNA was isolated at three and six hours intervals and submitted to oligonucleotide microarray protocol. The differentially expressed genes were obtained by paired t-tests with p<0.05 and interpreted using Venn diagrams, functional enrichment and protein interaction network analyses. Validation of microarray results was carried out through qPCR experiments of selected genes. We found a high number of significant genes with low fold changes in gene expression at the time intervals studied. These genes were regulated in a time dependent-manner, with most gene expression changes being exclusive to one of the time intervals evaluated. Our results indicated that blocking AT1 or AT2 changed the expression of genes involved in regulation of transcription, cell cycle, cell proliferation, differentiation, apoptosis, cell adhesion, cell migration, regulation of actin cytoskeleton, protein transport and protein ubiquitination. Additionally, the signaling pathways over-represented by the significant genes were ErbB, mTOR, MAPK, neurotrophin, insulin and Wnt. Finally, interactome analyses revealed hub genes associated with cell proliferation, survival, migration, transport, structural support, neurotrophin pathway, MAPK signaling and Wnt signaling. Taken together, our findings implicate Ang II-transcriptional regulation in glioma progression by means of the modulation of genes participating in protumoral functions. This transcriptome pattern is observed upon Ang II activation of either AT1 or AT2 receptors, thereby highlighting the relevance of both receptor subtypes in glioma progression. Interactome analyses disclosed hub genes regulated by Ang II which may present higher control over their networks. These genes participate in biological functions that could enhance the degree of malignancy in gliomas and thus should be further explored. C6 cells were cultured in Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% fetal bovine serum, 100 Units/ml penicillin and 100 M-BM-5g/ml streptomycin. Cells were seeded in cell culture dishes and incubated at 37M-BM-0C/ 5% CO2 until becoming confluent. Then, these cells were pre-treated (30 minutes) with either AT1 receptor antagonist (Losartan: 10-5M) or AT2 receptor antagonist (PD123319: 10-5M) followed by Ang II treatment (10-7 M) according to the treatment scheme: Group 1 M-bM-^@M-^S control; Group 2 M-bM-^@M-^S cells only treated with Ang II; Group 3 M-bM-^@M-^S cells pre-treated (30 minutes) with Losartan and then treated with Ang II; Group 4 M-bM-^@M-^S cells pre-treated (30 minutes) with PD123319 and then treated with Ang II. To identify which genes were significantly differentially expressed, paired t-tests (p<0.05) were performed in the following comparisons: Ang II x Control (3h); Ang II x Control (6h); Ang II +Los x Ang II (3h); Ang II +Los x Ang II (6h); Ang II +PD123319 x Ang II (3h); Ang II +PD123319 x Ang II (6h).

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Expression profiling of primary glioma samples

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