Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Epigenomic profiling of Glioblastoma Stem Cells (U3117) subjected to TET1, TET2 or TET3 protein knockouts and subsequent treatment with ascorbic acid.

ABSTRACT: Glioblastoma (GBM) is a fatal disease with a poor prognosis, whose aetiology involves profound molecular alterations. Given the limited progress made in recent years, research into new therapeutic avenues may improve the treatment of GBM patients. In this work, we have characterised the epigenomic landscape of patient-derived glioblastoma stem cells in the context of a proneural GBM subtype (U31117). We performed a systematic knockdown of each of the TET proteins (TET1, TET2 and TET3) and explored the consequences of their deletion at the level of DNA methylation (5mC) and hydroxymethylation (5hmC). Global 5hmC levels were then restored using a low dose of ascorbic acid, and the epigenetic landscape of all these conditions was examined using high-content DNA methylation microarrays (Illumina MethylationEPIC Beadchip platform).

ORGANISM(S): Homo sapiens

SUBMITTER: Mario Fraga F.

PROVIDER: E-MTAB-13504 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Brain tumors are among the most malignant cancers and can arise from neural stem cells or oligodendrocyte progenitor cells (OPCs). Glioma-propagating cells (GPCs) that have stem-like properties have been derived from tumor variants such as glioblastoma multiforme (GBM) and oligodendroglial tumors, the latter being more chemosensitive with better prognosis. It has been suggested that such differences in chemosensitivity arise from the different profiles of OPCs versus neural stem cells. We thus explored if GPCs derived from these glioma variants can serve as reliable in vitro culture systems for studies. We utilized gene expression analyses, since GBM and oligodendrogliomas can be molecularly classified. Accordingly, we derived a gene signature distinguishing oligodendroglial GPCs from GBM GPCs collated from different studies, which was enriched for the Wnt, Notch and TGF-beta pathways. Using a novel method in glioma biology, the Connectivity Map, we mapped the strength of gene signature association with patient gene expression profiles in 2 independent glioma databases [GSE16011, http://caintegrator-info.nci.nih.gov/rembrandt]. Our gene signature consistently stratified survival in glioma patients. This data would suggest that in vitro low passage GPCs are similarly driven by transcriptomic changes that characterize the favorable outcome of oligodendrogliomas over GBM. Additionally, the gene signature was associated with the 1p/19q co-deletion status, the current clinical indicator of chemosensitivity. Our gene signature detects molecular heterogeneity in oligodendroglioma patients that cannot be accounted for by histology or the 1p/19q status alone, and highlights the limitation of morphology-based histological analyses in tumor classification, consequently impacting on treatment decisions. Total RNA obtained from primary neurosphere culture from brain tumor specimens of 6 patients were compared. Replicate arrays were performed for all 6 neurosphere cultures.

Project description:Glioblastoma (GBM) is the most common and most aggressive primary brain tumor in adults. The existence of a small population of stem-like tumor cells that efficiently propagate tumors and resist cytotoxic therapy is one proposed mechanism leading to the resilient behavior of tumor cells and poor prognosis. In this study, we performed an in-depth analysis of the DNA methylation landscape in GBM-derived cancer stem cells (GSCs). Parallel comparisons of primary tumors and GSC lines derived from these tumors with normal controls (a neural stem cell (NSC) line and normal brain tissue) identified groups of hyper- and hypomethylated genes that display a trend of either increasing or decreasing methylation levels in the order of controls, primary GBMs, and their counterpart GSC lines, respectively. Interestingly, concurrent promoter hypermethylation and gene body hypomethylation were observed in a subset of genes including MGMT, AJAP1 and PTPRN2. These unique DNA methylation signatures were also found in primary GBM-derived xenograft tumors indicating that they are not tissue culture-related epigenetic changes. Integration of GSC-specific epigenetic signatures with gene expression analysis further identified candidate tumor suppressor genes that are frequently down regulated in GBMs such as SPINT2, NEFM and PENK. Forced re-expression of SPINT2 reduced glioma cell proliferative capacity, anchorage independent growth, cell motility, and tumor sphere formation in vitro. The results from this study demonstrate that GSCs possess unique epigenetic signatures that may play important roles in the pathogenesis of GBM. The reduced representation bisulfite sequencing (RRBS) approach (Meissner et al., 2008) was used to generate genome-wide single-base resolution CpG methylation profiles of three primary GBMs (1063T, 1133T, and 1142T) and three GSC lines (1063S, 1133S, 1142S) derived from these primary GBM tumors. The NSC line and the normal brain (NB) tissue sample were used as controls for comparison purposes. In addition, we analyzed three GBM xenograft tumor tissue samples (Mayo22, Mayo39, Mayo59) developed by Dr. Jann N. Sarkaria of Mayo Clinic.

Project description:Glioblastoma multiforme (GBM) is the most aggressive form of brain tumors. Despite radical surgery and radiotherapy supported by chemotherapy, the disease still remains incurable with extremely low median survival rate of 12-15 months from the time of initial diagnosis. The main cause of treatment failure is considered to be the presence of cells that are resistant to such treatment. MicroRNAs (miRNAs) as regulators of gene expression are involved in the tumor pathogenesis, including GBM. MiR-338 is a brain specific miRNA which has been described to target pathways involved in proliferation and differentiation. In our study, miR-338-3p and -5p were differentially expressed in GBM tissue in comparison to non-tumor brain tissue. Overexpression of miR-338-3p with miRNA mimic did not show any changes in proliferation rates in GBM cell lines (A172, T98G, U87MG). On the other hand, pre-miR-338-5p notably decreased proliferation and caused cell cycle arrest. Since radiation is currently the main treatment modality in GBM, we combined overexpression of pre-miR-338-5p with radiation, which led to significantly decreased of cell proliferation, and increased cell cycle arrest and apoptosis in comparison to only irradiated cells. To better elucidate the mechanism of action, we performed gene expression profiling analysis that revealed targets of miR-338-5p being Ndfip1, Rheb, ppp2R5a. These genes have been described to be involved in DNA damage response, proliferation and cell cycle regulation. To our knowledge, this is the first study to describe role of miR-338-5p in GBM and its potential to improve sensitivity of GBM to radiation. Study was performed on three glioblastoma multiforme cell lines A172, T98G and U87MG. This experiment was performed on Affymetrix GeneChip Human Gene ST 1.0 to elucidate the targets of miRNA-338-5p. Cell lines were seeded 24 hours prior transfection. After transfection with pre-miR338-5p or negative control cell were cultured for 24 hours and harvested. RNA was isolated using MirVana miRNA Isolation Kit (Ambion, USA) and checked for RNA integrity by Bioanalyzer 2100 and purity by ratios 260/280>1.8 and 260/230>1.8 by Nanodrop2000.

Dataset Information

Epigenomic profiling of Glioblastoma Stem Cells (U3117) subjected to TET1, TET2 or TET3 protein knockouts and subsequent treatment with ascorbic acid.

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