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IDH1 mutation defines methylation class and survival in human glioma

ABSTRACT: Astrocytoma, oligodendroglioma, oligoastrocytoma, and ependymoma are the main histologic subtypes of glioma. The molecular character of these subtypes has profound implications for understanding their causes and treatment. We describe the epigenetic landscape of these tumor types using novel DNA methylation profiling tools. There is a robust association of methylation profile with tumor histology and IDH1 mutation status. Furthermore, tumors with IDH1 mutation independently predict a tumor hypermethylator phenotype, histology, TP53 mutation status, patient age, and survival. Integrating tumor epigenetic and genetic alterations, this work provides a critical step toward better defining the somatic nature of glioma which will have great potential to impact clinical approaches to disease. This work provides an important step forward in classification of malignant brain tumors using DNA methylation profiling, integrating knowledge regarding IDH1 mutation in gliomas. The epigenetic homogeneity of the IDH1 mutant subclass despite histologic diversity implies that IDH1 mutation is a “driver” or functional determinant of a distinct DNA methylation phenotype, suggesting a novel role for an altered metabolic profile in the brain. This association occurs across histologic subtypes and demonstrates a clear relationship between genetic alteration and epigenetic profile. Fresh frozen tumor tissues were obtained from the University of California San Francisco (UCSF) Brain Tumor Research Center tissue bank with appropriate institutional review board approval. Tumors were diagnosed between 1990 and 2003. Tumor samples were defined as secondary GBM if the patients had prior histological diagnosis of a low-grade glioma. Tumors had previously been reviewed by UCSF neuropathologists to assign histologic subtype and grade. Normal brain tissue samples were from cancer-free patients who underwent temporal lobe resection as treatment for epilepsy at UCSF.

ORGANISM(S): Homo sapiens

SUBMITTER: Brock Christensen

PROVIDER: E-GEOD-20395 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

DNA methylation, isocitrate dehydrogenase mutation, and survival in glioma.

Christensen Brock C BC Smith Ashley A AA Zheng Shichun S Koestler Devin C DC Houseman E Andres EA Marsit Carmen J CJ Wiemels Joseph L JL Nelson Heather H HH Karagas Margaret R MR Wrensch Margaret R MR Kelsey Karl T KT Wiencke John K JK

Journal of the National Cancer Institute 20101216 2

<h4>Background</h4>Although much is known about molecular and chromosomal characteristics that distinguish glioma histological subtypes, DNA methylation patterns of gliomas and their association with other tumor features such as mutation of isocitrate dehydrogenase (IDH) genes have only recently begun to be investigated.<h4>Methods</h4>DNA methylation of glioblastomas, astrocytomas, oligodendrogliomas, oligoastrocytomas, ependymomas, and pilocytic astrocytomas (n = 131) from the Brain Tumor Rese ...[more]

PMID: 21163902

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Project description:Integrated profiling of somatic molecular alterations present in tumors is necessary to further our understanding of the tumorigenic process. We investigated the potential relationships between gene copy number alterations and DNA methylation profiles in a case series of pleural mesotheliomas (n=23). Gene copy number (CN) alterations profiled with 500K SNP arrays and DNA methylation measured at over 750 cancer-related genes with methylation bead-arrays were examined concomitantly. Considering each probed locus, there were no instances of significantly correlated CN alteration and methylation (no loci with Q < 0.05) and averaging loci over their associated genes revealed only two genes with significantly correlated CN and methylation alterations (Q < 0.04). In contrast to the lack of discrete correlations, the overall extent of tumor CN alteration was significantly associated with DNA methylation profile when comparing CN alteration extent among methylation profile classes (P < 0.02), and there was evidence that this association was partially attributable to prevalent allele loss observed at the maintenance DNA methyltransferase DNMT1. Taken together, this work indicates a strong association between global genetic and global epigenetic dysregulation in mesothelioma rather than a discrete, local coordination of gene inactivation, and further highlights the utility and necessity of integrative genomics approaches in cancer biology. Mesotheliomas were obtained following surgical resection at Brigham and Women’s Hospital through the International Mesothelioma Program from a pilot study conducted in 2002 and an incident case series beginning in 2005 as previously described (PMIDs: 19118007 and 19638575). All patients provided informed consent under the approval of the appropriate Institutional Review Boards. Clinical information, including histologic diagnosis was obtained from pathology reports. The study pathologist confirmed the histologic diagnoses and further assessed the percent tumor from resected specimens (mean >60%). DNA extraction and methylation analysis: DNA from fresh frozen tissue and matched whole blood was isolated with QIAamp DNA mini kit (Qiagen, Valencia, CA) following the manufacturer’s protocol. Tumor DNA was modified with sodium bisulfite using the EZ DNA Methylation Kit (Zymo Research, Orange, CA). Illumina GoldenGate® methylation bead arrays interrogated 1505 CpG loci associated with 803 cancer-related genes processed at the UCSF Institute for Human Genetics, Genomics Core Facility using methods described in (28). The GoldenGate methylation data used in the analysis has been previously described (PMIDs: 19118007 and 19638575).

Dataset Information

IDH1 mutation defines methylation class and survival in human glioma

Publications

DNA methylation, isocitrate dehydrogenase mutation, and survival in glioma.

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