A mitochondrial thioredoxin-sensitive mechanism regulates TGF-β-mediated gene expression associated with epithelial-mesenchymal transition.

Transforming growth factor (TGF)-β is a pro-oncogenic cytokine that induces the epithelial-mesenchymal transition (EMT), a crucial event in tumor progression. During TGF-β-mediated EMT in NMuMG mouse mammary epithelial cells, we observed sustained increases in reactive oxygen species (ROS) levels in the cytoplasm and mitochondria with a concomitant decrease in mitochondrial membrane potential and intracellular glutathione levels. In pseudo ρ0 cells, whose respiratory chain function was impaired, the increase in intracellular ROS levels was abrogated, suggesting an important role of mitochondrial activity as a trigger for TGF-β-stimulated ROS generation.