The transcription factors Slug and Snail act as repressors of Claudin-1 expression in epithelial cells

Abstract

Claudin-1 is an integral membrane protein component of tight junctions. The Snail family of transcription factors are repressors that play a central role in the epithelial-mesenchymal transition, a process that occurs during cancer progression. Snail and Slug members are direct repressors of E-cadherin and act by binding to the specific E-boxes of its proximal promoter. In the present study, we demonstrate that overexpression of Slug or Snail causes a decrease in transepithelial electrical resistance. Overexpression of Slug and Snail in MDCK (Madin-Darby canine kidney) cells down-regulated Claudin-1 at protein and mRNA levels. In addition, Snail and Slug are able to effectively repress human Claudin-1-driven reporter gene constructs containing the wild-type promoter sequence, but not those with mutations in two proximal E-box elements. We also demonstrate by band-shift assay that Snail and Slug bind to the E-box motifs present in the human Claudin-1 promoter. Moreover, an inverse correlation in the levels of Claudin-1 and Slug transcripts were observed in breast cancer cell lines. E-box elements in the Claudin-1 promoter were found to play a critical negative regulatory role in breast cancer cell lines that expressed low levels of Claudin-1 transcript. Significantly, in invasive human breast tumours, high levels of Snail and Slug correlated with low levels of Claudin-1 expression. Taken together, these results support the hypothesis that Claudin-1 is a direct downstream target gene of Snail family factors in epithelial cells.

Snail silencing effectively suppresses tumour growth and invasiveness

“…Snail induces a full EMT when overexpressed in epithelial Madin Darby canine kidney (MDCK) cells leading to the acquisition of a motile/invasive phenotype (Cano et al, 2000;Peinado et al, 2004b). In agreement with this role, Snail (also known as Snail1) has also been found to downregulate the expression of additional epithelial genes, such as occluding, claudins or muc1 (Guaita et al, 2002;Ikenouchi et al, 2003;Ohkubo and Ozawa, 2004;Martinez-Estrada et al, 2005), or to induce the expression of mesenchymal and invasive genes, like fibronectin and metalloproteinase (MMP)-9 (Cano et al, 2000;Guaita et al, 2002;Jorda et al, 2005). Snail expression has been detected in increasing number of different human carcinoma and melanoma cell lines (reviewed in Peinado et al, 2004a).…”

Transcriptional regulation of cell polarity in EMT and cancer

“…In fact, direct binding of SNAI1/SNAI2 to conserved E-box elements in the corresponding promoters has been reported for occludin, claudin-1 and claudin-7 (Ikenouchi et al, 2003;Martı´nez-Estrada et al, 2006). Interestingly, downregulation of claudin-4, the junctional adhesion molecule-1 (JAM-1/JAM-A) and Dlg3 has been detected in gene profiling studies of carcinoma cells, as well as in Madin-Darby canine kidney (MDCK) cells undergoing EMT after expression of SNAI1, SNAI2, E47 or other EMT regulators (De Craene et al, 2005b;Moreno-Bueno et al, 2006;Peinado et al, 2008).…”

“…Apart from E-cadherin, other epithelial genes initially downregulated by Snail and ZEB factors are components of the tight junctions, including occludin and several members of the claudin family (Ikenouchi et al, 2003;Ohkubo and Ozawa, 2004;De Craene et al, 2005b;Vandewalle et al, 2005;Martı´nez-Estrada et al, 2006). In fact, direct binding of SNAI1/SNAI2 to conserved E-box elements in the corresponding promoters has been reported for occludin, claudin-1 and claudin-7 (Ikenouchi et al, 2003;Martı´nez-Estrada et al, 2006).…”

RUNX3 is multifunctional in carcinogenesis of multiple solid tumors

“…Transcription repressors Snail and Slug are believed to have important functions in initiating the pathological EMT process. On oncogenic stimulation, they directly repress transcription of adherens-junction protein E-cadherin (Batlle et al, 2000;Cano et al, 2000) and tight-junction protein claudin-1 (Martinez- Estrada et al, 2006), facilitating loss of cell adhesion. Another inducer of EMT during malignant progression is TGF-b signaling, which results in the dissolution of tight junctions.…”