TGF-β in Epithelial to Mesenchymal Transition and Metastasis of Liver Carcinoma.
ABSTRACT Hepatocellular carcinoma (HCC) and cholangiocellular carcinoma (CCC) represent the majority of hepatic malignancies and are among the most frequent causes of cancer deaths worldwide with a rising incidence in western countries. Upon progression of liver cancer, the epithelial to mesenchymal transition (EMT) is considered a key process that drives intrahepatic metastasis. EMT is the transformation of epithelial cells to a mesenchymal phenotype exacerbating motility and invasiveness of various epithelial cell types. In this review we focus on EMT in hepatic fibrosis, HCC and CCC that is governed by the transforming growth factor (TGF)-β signaling. This cytokine has been shown to play diverse and conflicting roles in malignant development, acting as a tumor-suppressor in early cancerogenesis but enhancing tumor dissemination in later stages of tumor progression. Importantly, TGF-β can induce EMT in a variety of cancers including HCC and CCC, even though the complex molecular mechanisms underlying this process are not yet fully understood. We aim at collecting recent findings on the impact of TGF-β-induced EMT in liver carcinoma progression and at discussing new insights on promising drugable targets for future therapeutic approaches against CCC and HCC.
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ABSTRACT: To determine the expression characteristics of connective tissue growth factor (CTGF/CCN2) in human hepatocellular carcinoma (HCC) in histology and to elucidate the roles of CCN2 on hepatoma cell cycle progression and metastasis in vitro. Liver samples from 36 patients (who underwent hepatic resection for the first HCC between 2006 and 2011) and 6 normal individuals were examined for transforming growth factor β1 (TGF-β1) or CCN2 mRNA by in situ hybridization. Computer image analysis was performed to measure integrated optimal density of CCN2 mRNA-positive cells in carcinoma foci and the surrounding stroma. Fibroblast-specific protein-1 (FSP-1) and E-cadherin were examined to evaluate the process of epithelial to mesenchymal transition, α-smooth muscle actin and FSP-1 were detected to identify hepatic stellate cells, and CD34 was measured to evaluate the extent of vascularization in liver tissues by immunohistochemical staining. CCN2 was assessed for its stimulation of HepG2 cell migration and invasion using commercial kits while flow cytometry was used to determine CCN2 effects on HepG2 cell-cycle. In situ hybridization analysis showed that TGF-β1 mRNA was mainly detected in connective tissues and vasculature around carcinoma foci. In comparison to normal controls, CCN2 mRNA was enhanced 1.9-fold in carcinoma foci (12.36 ± 6.08 vs 6.42 ± 2.35) or 9.4-fold in the surrounding stroma (60.27 ± 28.71 vs 6.42 ± 2.35), with concomitant expression of CCN2 and TGF-β1 mRNA in those areas. Epithelial-mesenchymal transition phenotype related with CCN2 was detected in 12/36 (33.3%) of HCC liver samples at the edges between carcinoma foci and vasculature. Incubation of HepG2 cells with CCN2 (100 ng/mL) resulted in more of the cells transitioning into S phase (23.85 ± 2.35 vs 10.94 ± 0.23), and induced a significant migratory (4.0-fold) and invasive (5.7-fold) effect. TGF-β1-induced cell invasion was abrogated by a neutralizing CCN2 antibody showing that CCN2 is a downstream mediator of TGF-β1-induced hepatoma cell invasion. These data support a role for CCN2 in the growth and metastasis of HCC and highlight CCN2 as a potential novel therapeutic target.World Journal of Gastroenterology 12/2012; 18(47):7070-8. · 2.55 Impact Factor
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ABSTRACT: The role of the epithelial-to-mesenchymal transition (EMT) during hepatocellular carcinoma (HCC) progression is well established, however the regulatory mechanisms modulating this phenomenon remain unclear. Here, we demonstrate that transcription factor glioma-associated oncogene 1 (GLI1) modulates EMT through direct up-regulation of SNAI1 and serves as a downstream effector of the transforming growth factor-β1 (TGFβ1) pathway, a well-known regulator of EMT in cancer cells. Overexpression of GLI1 increased proliferation, viability, migration, invasion, and colony formation by HCC cells. Conversely, GLI1 knockdown led to a decrease in all the above-mentioned cancer-associated phenotypes in HCC cells. Further analysis of GLI1 regulated cellular functions showed that this transcription factor is able to induce EMT and identified SNAI1 as a transcriptional target of GLI1 mediating this cellular effect in HCC cells. Moreover, we demonstrated that an intact GLI1-SNAI1 axis is required by TGFβ1 to induce EMT in these cells. Together, these findings define a novel cellular mechanism regulated by GLI1, which controls the growth and EMT phenotype in HCC.PLoS ONE 01/2012; 7(11):e49581. · 3.73 Impact Factor