Activation of the Erk Pathway Is Required for TGF-β1-Induced EMT In Vitro

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.

Inhibition of tumor growth and metastasis by a self-therapeutic nanoparticle

“…It is well known that the down-regulation of E-Cad expression is the hallmark of epithelial plasticity (9,41). Our data demonstrated that AuNP treatment resulted in a substantial increase in E-Cad expression with simultaneous decrease in Vimentin, Snail, and N-Cad expression in ovarian cancer cells, further supporting anti-EMT function of unmodified AuNPs (Fig.…”

“…Together the results obtained from qRT-PCR and the cytokine array indicate that the AuNP treatment in the ovarian cancer cell lines does modulate the expression of the growth both at the transcriptional and translational level. Since the proteins discussed above are collectively known to induce EMT (19,25,41), these results suggest a possible anti-EMT function of AuNPs.…”

Epithelial-mesenchymal transition induced by the stromal cell-derived factor-1/CXCR4 system in oral squamous cell carcinoma cells

“…Under these conditions, EMT is defined as the occurrence of a variable proportion of tumor cells that upregulate mesenchymal markers such as vimentin and snail, and that downregulate epithelial markers such as E-cadherin (17,18). The expression of these EMT markers is induced by a number of growth factor/receptor systems such as the hepatocyte growth factor (HGF)/c-met system (19)(20)(21) and the transforming growth factor (TGF)-ß/TGF-ß receptor system (22,23), both of which are associated with a more aggressive phenotype of cancer cells. However, little information is available regarding the type of EMT induced by chemokine system(s), including the SDF-1/CXCR4 system, despite abundant evidence of the diverse malignant behaviors of such systems in cancer cells.…”

Activation of Bone Morphogenetic Protein Signaling by a Gemini Vitamin D3 Analogue Is Mediated by Ras/Protein Kinase Cα

“…Many studies of cross-talk between Ras and TGF-h/Smad signaling have been described during the last decade (31)(32)(33)(34)(35). Yue et al (31) reported that TGF-h activated the Ras/MAPK pathway required for the autocrine TGF-h production and Smad1 regulation.…”

“…Ras was also suggested as a mediator of pleiotropic TGF-h1 signaling in developing neurons (32). The activation of Ras/MAPK or the presence of oncogenic Ras was shown to enhance TGF-hinduced epithelial-mesenchymal transition (33,34). More importantly, it has been shown that 1a,25(OH) 2 D 3 regulates the MAPK pathway by activating Ras/RAF-1 signaling in muscle cells and in myeloid leukemic cells (17,18).…”