2736

GLI2

In melanoma cells, high expression of the transcription factor GLI2 is associated with increased invasive potential and loss of E-cadherin expression, an event reminiscent of the epithelial-to-mesenchymal transition (EMT). Herein, we provide evidence that GLI2 represses E-cadherin gene (CDH1) expression in melanoma cells via distinct mechanisms, enhancing transcription of the EMT-activator ZEB1 and cooperative repression of CDH1 gene transcription via direct binding of both GLI2 and ZEB1 to two closely positioned Kruppel-like factor-binding sites within the CDH1 promoter. GLI2 silencing rescued CDH1 expression except in melanoma cell lines in which the CDH1 promoter was hypermethylated. Proximity ligation assays identified GLI2-ZEB1 complexes in melanoma cell nuclei, proportional to endogenous GLI2 and ZEB1 expression, and whose accumulation was enhanced by the classical EMT inducer TGF-beta. These data identify GLI2 as a critical modulator of the cadherin switch in melanoma, a molecular process that is critical for metastatic spread of the disease.CI - (c) 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Neuroblastoma is the second most common extracranial malignant solid tumor that occurs in childhood, and metastasis is one of the major causes of death in neuroblastoma patients. The epithelial-mesenchymal transition (EMT) is an important mechanism for both the initiation of tumor invasion and subsequent metastasis. Therefore, this study investigated the mechanism by which transforming growth factor (TGF)-beta1 induces EMT in human neuroblastoma cells. Using quantitative RT-qPCR and western blot analyses, we found that the mRNA and protein expression levels of E-cadherin were significantly decreased, whereas that of alpha-SMA was significantly increased after neuroblastoma cells were treated with different concentrations of TGF-beta1. A scratch test and Transwell migration assay revealed that cell migration significantly and directly correlated with the concentration of TGF-beta1 indicating that TGF-beta1 induced EMT in neuroblastoma cells and led to their migration. Inhibiting Smad2/3 expression did not affect the expression of the key molecules involved in EMT. Further investigation found that the expression of the glioblastoma transcription factor (Gli) significantly increased in TGF-beta1-stimulated neuroblastoma cells undergoing EMT, accordingly, interfering with Gli1/2 expression inhibited TGF-beta1-induced EMT in neuroblastoma cells. GANT61, which is a targeted inhibitor of Gli1 and Gli2, decreased cell viability and promoted cell apoptosis. Thus, TGF-beta1 induced EMT in neuroblastoma cells to increase their migration. Specifically, EMT induced by TGF-beta1 in neuroblastoma cells did not depend on the Smad signaling pathway, and the transcription factor Gli participated in TGF-beta1-induced EMT independent of Smad signaling.