3D Chromatin Remodeling Potentiates Transcriptional Programs Driving Cell Invasion [Hi-C]

Epigenetic mechanisms often play an important role in driving tumor progression towards metastasis. It is less clear that deregulation of chromatin architecture, including topologically associated domains (TADS), contributes to cancer progression. CTCF is a central regulator of three dimensional chromatin structure that undergoes copy number loss in over half of all breast cancers, but the impact of this defect on epigenetic programming and chromatin architecture remains obscure. We find that the reduced pools of CTCF in hemizygous models potentiates cell invasion. Underlying this phenotype is the activation of oncogenic networks including the PI3K signaling cascade, which presents therapeutic vulnerabilities, especially to mTOR inhibitors. Deregulation of these oncogenic pathways is largely due to the loss of CTCF insulation, allowing a reorganization of long-range chromatin contacts at the subTAD level that is associated with aberrant programming of H3K27 acetylation at enhancer/promoter regions. Thus, lowered CTCF levels lead to chromatin reorganization facilitating pro-invasive transcriptional programs. Examination of mRNA expression, CTCF binding, H3K4me3, H3K27ac, DNA Methylation and chromatin conformation underlying the oncogenic phenotypes potentiated by CTCF LOH in mammalian breast epithelial cells.