Synthetic epigenetic reprogramming of mesenchymal to epithelial states using the CRISPR/dCas9 platform in triple negative breast cancer [ATAC-seq]

Epithelial-mesenchymal transition (EMT) is a reversible transcriptional program subverted by cancer cells to drive cancer progression. Transcription factor ZEB1 is a master regulator of EMT, driving disease recurrence in poor outcome triple negative breast cancer (TNBC).  Here, we silence ZEB1 in TNBC models by CRISPR-mediated epigenetic editing, resulting in nearly complete repression of ZEB1 in vivo, accompanied by long-lasting tumor inhibition. Integrated transcriptomic and epigenetic profiling identified a ZEB1-dependent gene-signature associated with transcriptional up-regulation, promoter DNA demethylation and enhanced chromatin accessibility in core cell adhesion loci, demonstrating epigenetic reprogramming towards a more epithelial state. Epigenetic shifts induced by ZEB1-silencing are enriched in a subset of human breast tumors, illuminating a clinically-relevant hybrid-like state. Thus, the synthetic epi-silencing of ZEB1 induces stable “lock-in” epigenetic reprogramming of mesenchymal tumors associated with a distinct epigenetic landscape. We outline approaches to stably reprogram EMT for targeting poor outcome breast cancers driven by oncogenic transcription factors. Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq) SUM159 cells with pLV-KRAB and a combination of 4 gRNAs targeting the promoter of ZEB1 or empty vector (control).