Activation of NADPH oxidase subunit NCF4 induces ROS-mediated EMT signaling in HeLa cells.

The epithelial-mesenchymal transition (EMT) is a critical biological process characterized by morphological and behavioral changes in cells. The regulatory and signaling mechanisms of both developmental and pathological EMT have been investigated. Reactive oxygen species (ROS) play a role in early EMT, but the exact mechanism by which ROS are involved is unclear. We investigated ROS-mediated EMT in human HeLa cells. Transforming growth factor beta (TGF-β) treatments lead to dramatic NADPH oxidase 2 (NOX2) inductions in HeLa cells; antioxidant treatment prevented TGF-β-driven EMT. Over-expression of the p40phox subunit (NCF4) led to activation of the NOX2 complex and ROS production. We showed that NOX2 and NOX5 mRNA was increased, along with increased expression of several matrix metalloproteinases (MMPs) in response to NCF4 expression. Moreover, these changes were reversible upon ROS scavenging. Down-regulation of E-cadherin and up-regulation of Snail, Slug and vimentin occurred at the transcriptional level. We also showed that new EMT regulator, YB-1 is a downstream target in ROS-induced EMT. Together, these data suggest that ROS switching is necessary for increased EMT but is not required for the morphological changes that accompany EMT.