[Mechanisms Of Signal Transduction] Connective Tissue Growth Factor Is Overexpressed in Esophageal Squamous Cell Carcinoma and Promotes Tumorigenicity through -Catenin-T-cell Factor/Lef Signaling
Connective tissue growth factor (CTGF or CCN2), a member of the CCN family, is involved in diverse biological processes such as cell adhesion, proliferation, and angiogenesis. In this study, we show that overexpression of CTGF occurred in a significant proportion of esophageal squamous cell carcinoma (ESCC) samples that were of a high tumor grade and metastatic. Forced expression of CTGF in Eca109 ESCC cells accelerated their growth in culture and significantly increased tumor formation in nude mice, whereas RNA interference-mediated knockdown of CTGF in ESCC cells significantly inhibited cell growth and colony formation, as well as tumorigenicity in vivo. Moreover, overexpression of CTGF in ESCC cells resulted in the accumulation and nuclear translocation of β-catenin, leading to activation of β-catenin-T-cell factor (TCF)/Lef signaling. Up-regulation of c-Myc and cyclin D1, two target genes of β-catenin-TCF/Lef signaling, was also observed in the CTGF-overexpressing cells. These effects of CTGF in ESCC cells were abolished by transfection with either dominant negative β-catenin or dominant negative TCF4. Furthermore, we identified a β-catenin-TCF/Lef-binding site (TBE) in the promoter region of CTGF and found that CTGF is a transcriptional target of β-catenin-TCF/Lef signaling. Taken together, these results revealed that the interaction of CTGF and β-catenin-TCF/Lef forms a positive feedback loop, which could contribute to the tumorigenicity of ESCC.