Epidermal growth factor promotes transforming growth factor-β1-induced epithelial-mesenchymal transition in HK-2 cells through a synergistic effect on Snail

Abstract

Epithelial-mesenchymal transition (EMT) is a central mechanism for wound healing, tissue repair, organ fibrosis and carcinoma progression in adults. Evidence shows that both epidermal growth factor (EGF) and transforming growth factor-β1 (TGF-β1) are upregulated during renal interstitial fibrosis, and that co-stimulation of EGF and TGF-β1 could induce renal tubular epithelial cells to undergo EMT more effectively than EGF or TGF-β1 alone. This study was intended to explore the molecular mechanism underlying this effect. HK-2 cells underwent apparent EMT with increased cell motility after co-stimulation of EGF and TGF-β1 as compared with TGF-β1 or EGF alone. Co-stimulation of EGF and TGF-β1 resulted in rapid and robust ERK1/2 activation and induced persistent high expression of Snail protein. Treatment with the MEK inhibitor U0126 followed by co-stimulation with EGF and TGF-β1 prevented the upregulation of Snail protein, EMT and motility, without impairing Snail mRNA. TGF-β1 induced Snail at the transcriptional level, which was not influenced by EGF. Inhibition of Snail expression by siRNA interference also prevented EMT caused by co-stimulation of EGF and TGF-β1. These data suggest that EGF promotes TGF-β1-induced EMT through a synergistic effect on Snail at the post-transcriptional level in HK-2 cells.