Modeling epigenetic lesions that cause gliomas [ChIP-Seq]
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. Overall design: CTCF occupancy characterization, histone H3K27 acetylation profiling in mouse NPC and OPC cells. DNA methylation profiling (capture bisulfite sequencing) on human glioma samples.