TGF‐beta Signaling Regulates NADPH Oxidase 4 (Nox4) – Dependent Oxidative Stress and Migration of Human Breast Epithelial Cells

Abstract

The epithelial to mesenchymal transition (EMT) is a mechanism by which epithelial cells acquire migratory properties in processes dependent on TGFβ-mediated modulation of extracellular matrix (ECM) proteins during organ development, wound healing, fibrosis, and cancer metastasis. Recent observations suggest ROS play important roles in TGFβ-induced EMT of many cell types; however, little is known about redox-dependent mechanisms in response to TGFβ in breast epithelial cells. Our studies suggest Nox4, a member of the NADPH oxidase (Nox) family, is a source of ROS during induction of EMT in normal and mestastatic breast epithelial cells. We found TGFβ induces Nox4 expression (mRNA and protein) and ROS generation in normal (MCF10A) and metastatic (MDA-MB-231) human breast epithelial cells, whereas cells expressing a dominant-negative form of Nox4 showed decreased ROS production upon TGFβ treatment. Furthermore, TGFβ induces the Nox4 promoter and expression of constitutively active TGFβ receptor type I further increased Nox4 promoter activity, mRNA, protein expression, and ROS generation. Moreover, expression of dominant-negative Nox4 reduced TGFβ-induced wound healing, cell migration, and fibronectin mRNA expression. These data indicate Nox4 contributes to ROS production that may be critical for EMT progression in breast epithelial cells. Supported by the Intramural Research Program of the NIAID.