Transcriptional Activation of ZEB1 by Slug Leads to Cooperative Regulation of the Epithelial–Mesenchymal Transition-Like Phenotype in Melanoma

Abstract

The E-box-binding zinc finger transcription factors Slug and ZEB1 are important repressors of E-cadherin, contributing to epithelial-mesenchymal transition (EMT) in primary epithelial cancers. Activator or repressor status of EMT transcription factors defines consequences for tumorigenesis. We show that changes in expression levels of Slug in melanoma cell lines lead to concomitant alterations of ZEB1 expression. Electrophoretic mobility shift, luciferase reporter, and chromatin immunoprecipitation assays identified Slug as a direct transcriptional activator at E-boxes of the ZEB1 promoter. Transcriptional activation of ZEB1 was demonstrated to be specific for Slug, as EMT regulators Snail and Twist failed to influence ZEB1 expression. Slug and ZEB1 cooperatively repressed E-cadherin expression resulting in decreased adhesion to human keratinocytes, but promoted migration of melanoma cells. Our results show that the transcriptional activity of ZEB1 is increased by Slug, suggesting a hierarchical organized expression of EMT transcription factors through directed activation, triggering an EMT-like process in melanoma.

A novel hypoxia-associated subset of FN1highMITFlow melanoma cells: identification, characterization, and prognostic value

“…39,42 Other epithelial-to-mesenchymal transition-regulatory transcription factors like SNAI1 and SNAI2 are not expressed in the FN1 high MITF low melanoma cells; SNAI1/2 are early epithelial-to-mesenchymal transition markers implicated in the initial induction of a migratory phenotype, whereas ZEB1 is an important regulator of the maintenance of this phenotype. 40,43 MITF was recently proposed as the transcriptional switch that drives stem-like melanoma cells toward differentiation, 29 which is in line with our hypothesis that FN1 high MITF low melanoma cells may represent a reservoir of slow-cycling stemlike/tumor-driving cells. Interestingly, hypoxia represses MITF expression and thereby enhances the metastatic potential of melanoma cells.…”

“…[32][33][34][35][36][37] In addition, hypoxia and its effector HIF2A have recently been suggested to induce epithelial-to-mesenchymal transition through the inhibition of miRNA-200b and the subsequent induction of ZEB1. 38,39 ZEB1 is a well-established epithelial-to-mesenchymal transition inducer in melanoma cells 40 and generally promotes tumorigenicity and stemness. 41 We observed an increase in ZEB1 protein in A375 melanoma cells cultured in hypoxic conditions, although ZEB1 mRNA levels did not change.…”

High Motility of Triple-negative Breast Cancer Cells Is Due to Repression of Plakoglobin Gene by Metastasis Modulator Protein SLUG

“…It inhibits PUMA to block the induction of anoikis in the cancer cells (31)(32)(33). Although cancer cells with abnormally high levels of SLUG protein are highly motile (8,(35)(36)(37)(38), direct association of SLUG with cellular motility is not established until our study. Using the isogenic breast cancer cell system, we have shown here that the motility of the SLUG-negative cells is increased significantly with the expression of SLUG in these cells.…”

A conserved role for Snail as a potentiator of active transcription

“…In summary, our study revealed a direct activator role for Drosophila Snail, a function that is seemingly conserved from flies to humans (Sakai et al 2006;Stemmer et al 2008;Reece-Hoyes et al 2009;Hu et al 2010;Tao et al 2011;Wels et al 2011;Hahn et al 2013) and places the Snail family of proteins in the category of dually acting TFs.…”

“…Although the studies in HepG2 cells and in quail show that full activation by Snail requires a partner factor, vertebrate Snail proteins can also activate on their own in vitro (Huang et al 2009;Tao et al 2011;Wels et al 2011;Hahn et al 2013). Potential synergistic effects have not been analyzed in these studies.…”