Activation of the Erk pathway is required for TGF-beta1-induced EMT in vitro

Neoplasia. Sep-Oct 2004;6(5):603-10. doi: 10.1593/neo.04241.

Abstract

Transforming growth factor-beta1 (TGF-beta1) can be tumor-suppressive through the activation of the Smad-mediated signaling pathway. TGF-beta1 can also enhance tumor progression by stimulating epithelial-to-mesenchymal transition (EMT) through additional pathways. EMT is characterized by the acquisition of a fibroblast-like cell morphology, dissolution of tight junctions, disruption of adherence junctions, and formation of actin stress fibers. There is evidence linking the activation of mitogen-activated protein kinase pathways to the induction of TGF-beta1-mediated EMT. However, the role of Erk in the induction of TGF-beta1-mediated EMT remains unclear. TGF-beta1 treatment of normal murine mammary gland (NMuMG) epithelial cells resulted in increased gene expression of Ras, Raf, MEK1/2, and Erk1/2, as shown by microarray analysis and real-time polymerase chain reaction. Upon 24 and 48 hours of treatment with TGF-beta1, NMuMG and mouse cortical tubule (MCT) epithelial cells underwent EMT as shown by changes in cell morphology, delocalization of zonula occludens-1 and E-cadherin from cell-cell junctions, and formation of actin stress fibers. TGF-beta1 treatment also resulted in increased levels of phosphorylated Erk and Erk kinase activity. Treatment with an MEK inhibitor, U0126, inhibited increased Erk phosphorylation and kinase activity, and blocked TGF-beta1-induced EMT in both cell lines. These data show that TGF-beta1 induces the activation of the Erk signaling pathway, which is required for TGF-beta1-mediated EMT in vitro.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Butadienes / pharmacology
  • Cell Differentiation / genetics
  • Cell Differentiation / physiology
  • Cell Line
  • Epithelial Cells / cytology*
  • Epithelial Cells / drug effects
  • Epithelial Cells / enzymology*
  • Gene Expression / drug effects
  • MAP Kinase Kinase 1 / antagonists & inhibitors
  • MAP Kinase Kinase 1 / genetics
  • MAP Kinase Kinase 1 / physiology
  • MAP Kinase Signaling System*
  • Mammary Glands, Animal / cytology
  • Mesoderm / cytology
  • Mice
  • Nitriles / pharmacology
  • Oligonucleotide Array Sequence Analysis
  • Phosphorylation / drug effects
  • Transforming Growth Factor beta / pharmacology
  • Transforming Growth Factor beta / physiology*
  • Transforming Growth Factor beta1
  • Up-Regulation

Substances

  • Butadienes
  • Nitriles
  • Tgfb1 protein, mouse
  • Transforming Growth Factor beta
  • Transforming Growth Factor beta1
  • U 0126
  • MAP Kinase Kinase 1