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

Area of Science:

• Molecular Biology
• Cancer Research
• Epigenetics

Background:

• Epithelial-to-mesenchymal transitions (EMTs) and extracellular matrix (ECM) remodeling are critical for carcinoma invasion and metastasis.
• Transforming growth factor β (TGF-β) and RAS signaling pathways are known to induce these processes, but their coordinated regulation is not fully understood.

Purpose of the Study:

• To elucidate the molecular mechanisms by which TGF-β and RAS signaling jointly regulate EMT and ECM remodeling in lung adenocarcinoma metastasis.
• To identify the chromatin determinants that link gene expression to TGF-β and RAS signaling inputs.

Main Methods:

• The study investigates the roles of RAS-responsive element-binding protein 1 (RREB1), SMAD proteins, and chromatin modifications in regulating fibrogenic and EMT genes.
• Chromatin immunoprecipitation and gene expression analyses were employed to identify regulatory elements and their associated factors.

Main Results:

• RREB1, along with specific histone marks (H4K16acK20ac) on histone H2A.Z nucleosomes, localizes to enhancers of fibrogenic genes (IL11, PDGFB, HAS2) and the EMT factor SNAI1.
• These primed enhancers are subsequently activated by a SMAD4-INO80 complex in response to TGF-β, demonstrating a coordinated transcriptional program.
• This regulatory mechanism segregates the fibrogenic EMT program from other TGF-β responses.

Conclusions:

• The coordinated action of TGF-β and RAS signaling, mediated by RREB1 and specific chromatin states, drives lung adenocarcinoma metastasis.
• Understanding these regulatory networks reveals vulnerabilities in the metastatic program that could be therapeutically targeted.