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Modeling epigenetic lesions that cause gliomas [ChIP-Seq]

ABSTRACT: Epigenetic lesions that disrupt gene regulatory elements and expression are increasingly recognized as pervasive drivers of human cancers. However, we currently lack the in vitro and in vivo models required to functionally validate such lesions and their tumorigenic impact. Here we model aberrations that arise in Isocitrate Dehydrogenase mutant (IDHmut) lower-grade gliomas, which exhibit profound DNA hypermethylation. We initially focus on a CTCF insulator downstream of the PDGFRA oncogene that is recurrently disrupted in IDHmut gliomas. We demonstrate that disruption of the syntenic insulator in mouse oligodendrocyte-progenitor cells (OPCs) allows an OPC-specific enhancer to contact and induce PDGFRA, thereby increasing proliferation. In contrast, insulator disruption did not affect PDGFRA expression in neural progenitor cells (NPCs), which lack the enhancer. We also model a second recurrent epigenetic lesion in IDHmut gliomas, the methylation-dependent silencing of the CDKN2A tumor suppressor. We show that inactivation of CDKN2A/p19ARF by de novo promoter methylation or mutation drives OPC proliferation and synergizes with PDGFRA insulator loss. Finally, we use lentiviruses to coordinately inactivate the PDGFRA insulator and CDKN2A in mouse corpus callosum, resulting in low-grade gliomagenesis in vivo. Our study recapitulates recurrent epigenetic lesions in mouse models and demonstrates that combination of PDGFRA activation and CDKN2A silencing can transform OPCs in vitro and drive gliomagenesis in vivo.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE225732 | GEO | 2023/07/25

REPOSITORIES: GEO

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Project description:Purpose: To define copy number alterations and gene expression signatures underlying pediatric high-grade glioma (HGG). Patients and Methods: We conducted a high-resolution analysis of genomic imbalances in 78 de novo pediatric HGG, including 7 diffuse intrinsic pontine gliomas, and 10 HGG cases arising in children who received cranial irradiation for a previous cancer, using Affymetrix 500K GeneChips. Gene expression signatures for 53 tumors were analyzed with Affymetrix U133v2 arrays. Results were compared with publicly available data from adult tumors. Results: Pediatric and adult glioblastoma were clearly distinguished by frequent gain of chromosome 1q (30% vs 9%) and lower frequency of chromosome 7 gain (13% vs 74%), respectively. The most common focal amplifications also differed, with PDGFRA and EGFR predominant in childhood and adult populations respectively. These common alterations in pediatric HGG were detected at higher frequency in irradiation-induced tumors, suggesting that these are initiating events in childhood gliomagenesis. CDKN2A was the most common tumor suppressor gene targeted by homozygous deletion in pediatric HGG. No IDH1 hotspot mutations were found in pediatric tumors, highlighting molecular differences in pathogenesis between childhood HGG and adult secondary glioblastoma. Integrated copy number and gene expression data indicated that deregulated PDGFRA signaling plays a major role in pediatric HGG. Conclusions: Integrated molecular profiling showed substantial differences in the molecular features underlying pediatric and adult HGG, indicating that findings in adult tumors cannot be simply extrapolated to younger patients. PDGFRA may be a useful target for pediatric HGG including diffuse pontine gliomas. Keywords: disease state analysis 78 samples for SNP analysis, including 10 samples arising in children who received cranial irradiation for a previous cancer and 7 diffuse pontine gliomas; 53 of them with gene expression analysis; 2 tumor grades To have access to SNP CEL files, please contact Dr. Suzanne Baker (suzzane.baker@stjude.org).

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Modeling epigenetic lesions that cause gliomas [ChIP-Seq]

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