TGF-ß and RAS jointly unmask primed enhancers to drive metastasis (DRIPc-seq)

Epithelial-to-mesenchymal transitions (EMTs) and extracellular matrix (ECM) remodeling are distinct yet important processes during carcinoma invasion and metastasis. TGF-ß and RAS, signaling through SMAD and RAS-responsive element-binding protein 1 (RREB1), jointly trigger expression of EMT and fibrogenic factors as two discrete arms of a common transcriptional response in carcinoma cells. Here we demonstrate that both arms form a program for lung adenocarcinoma pulmonary metastasis and identify chromatin determinants tying the expression of the constituent genes to TGF-ß and RAS dual inputs. RREB1 binds near H4K16ac histone marks and histone H2A.Z-loaded nucleosomes at enhancers in the fibrogenic genes IL11, PDGFB, and HAS2 and the EMT transcription factor SNAI1, priming these enhancers for activation by a SMAD4-INO80 nucleosome remodeling complex in response to TGF-ß. These regulatory properties set the fibrogenic EMT program apart from RAS-independent TGF-ß gene responses and illuminate the operation and vulnerabilities of a transcriptional program that promotes metastatic outgrowth. Overall design: Genome binding/occupancy profiling by high throughput sequencing of 393T3 cells, a cell line derived from a lung tumor from a KrasG12D;p53-/- (KP) genetically engineered mouse model, treated with SB505124 or TGF-ß for 1.5 h