TGF-β and RAS jointly unmask primed enhancers to drive metastasis.

Epithelial-to-mesenchymal transitions (EMTs) and extracellular matrix (ECM) remodeling are distinct yet important processes during carcinoma invasion and metastasis. Transforming growth factor β (TGF-β) 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 come together to form a program for lung adenocarcinoma metastasis and identify chromatin determinants tying the expression of the constituent genes to TGF-β and RAS inputs. RREB1 localizes to H4K16acK20ac marks in histone H2A.Z-loaded nucleosomes at enhancers in the fibrogenic genes interleukin-11 (IL11), platelet-derived growth factor-B (PDGFB), and hyaluronan synthase 2 (HAS2), as well as the EMT transcription factor SNAI1 , priming these enhancers for activation by a SMAD4-INO80 nucleosome remodeling complex in response to TGF-β. These regulatory properties segregate the fibrogenic EMT program from RAS-independent TGF-β gene responses and illuminate the operation and vulnerabilities of a bifunctional program that promotes metastatic outgrowth. [Display omitted] • TGF-β and RAS drive expression of EMT and fibrogenic genes that jointly fuel metastasis • Epigenetic determinants segregate different programs within a global TGF-β response • RAS/MAPK-regulated RREB1 primes enhancers for activation by SMAD-recruited INO80 • Targeting RREB1 selectively inhibits LUAD metastasis During carcinoma metastasis, malignant progenitors undergo a TGF-β-dependent EMT associated with fibroblast activation and extracellular matrix remodeling in the tumor microenvironment. RAS-activated RREB1 primes enhancers of EMT and fibrogenic genes in lung adenocarcinoma cells for activation by chromatin remodeling complexes that the TGF-β/SMAD pathway recruits to these enhancers. Inhibiting RREB1 disables this pro-metastatic process. [ABSTRACT FROM AUTHOR]