Wnt-1 but not epidermal growth factor induces beta-catenin/T-cell factor-dependent transcription in esophageal cancer cells

Abstract

beta-Catenin plays an important role in signal transduction pathways that regulate cellular differentiation and proliferation. The increased concentration of this protein in the cytoplasm favors its binding to the T-cell factor (TCF) family of DNA-binding proteins, and it subsequently translocates to the nucleus, where it induces transcription of specific genes. We explored mechanisms that lead to activation of beta-catenin/TCF-dependent transcription in esophageal squamous cell carcinoma (ESCC) independent of adenomatous polyposis coli and beta-catenin mutation. Electrophoresis mobility shift assay demonstrated that TCF4 and beta-catenin form a complex and have DNA binding activity. However, there was no constitutive activation of beta-catenin/TCF-dependent transcription. Coculture experiments demonstrated that Wnt-1, but not Wnt-5A and Wnt-7A, activated the TCF reporter gene. Additionally, when cultured with Wnt-1-conditioned media, ESCC cell lines showed an accumulation of beta-catenin in the cytoplasm. Although both Wnt and epidermal growth factor inactivate glycogen synthase kinase 3beta, activation of epidermal growth factor receptor did not stabilize beta-catenin. A comparison of extracellular stimuli suggests that specific Wnt family members stabilize beta-catenin with resulting activation of TCF-dependent transcription in ESCC.