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

• Published in: Neoplasia (New York, N.Y.) N.Y.), 2004-09, Vol.6 (5), p.603-610
• Main Authors: Xie, Lu, Law, Brian K, Chytil, Anna M, Brown, Kimberly A, Aakre, Mary E, Moses, Harold L
• Format: Article
• Language: English
• Subjects: 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; Mammary Glands, Animal - cytology; MAP Kinase Kinase 1 - antagonists & inhibitors; MAP Kinase Kinase 1 - genetics; MAP Kinase Kinase 1 - physiology; MAP Kinase Signaling System; 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
• ISSN: 1522-8002

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.