Activation of the Erk pathway is required for TGF-beta1-induced EMT in vitro.
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.
Xie
Lu
L
Vanderbilt-Ingram Cancer Center, 2220 Pierce Avenue South, Vanderbilt University, Nashville, TN 37232, USA.
Law
Brian K
BK
Chytil
Anna M
AM
Brown
Kimberly A
KA
Aakre
Mary E
ME
Moses
Harold L
HL
D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D002460:Cell Line; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D015870:Gene Expression / Q000187:drug effects; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D020935:MAP Kinase Signaling System; D008321:Mammary Glands, Animal / Q000166:cytology; D008648:Mesoderm / Q000166:cytology; D051379:Mice; D009570:Nitriles / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000494:pharmacology / Q000502:physiology*; D053773:Transforming Growth Factor beta1; D015854:Up-Regulation
D002070:Butadienes; D009570:Nitriles; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C113580:U 0126; D048369:MAP Kinase Kinase 1