O-GlcNAcylation affects β-catenin and E-cadherin expression, cell motility and tumorigenicity of colorectal cancer

Abstract O- GlcNAcylation, the addition of β-N-acetylglucosamine ( O -GlcNAc) moiety to Ser/Thr residues, is a sensor of the cell metabolic state. Cancer diseases such as colon, lung and breast cancer, possess deregulated O-GlcNAcylation. Studies during the last decade revealed that O-GlcNAcylation is implicated in cancer tumorigenesis and proliferation. The Wnt/β-catenin signaling pathway and cadherin-mediated adhesion are also implicated in epithelial-mesenchymal transition (EMT), a key cellular process in invasion and cancer metastasis. Often, deregulation of the Wnt pathway is caused by altered phosphorylation of its components. Specifically, phosphorylation of Ser or Thr residues of β-catenin affects its location and interaction with E-cadherin, thus facilitating cell-cell adhesion. Consistent with previous studies, the current study indicates that β-catenin is O -GlcNAcylated. To test the effect of O -GlcNAcylation on cell motility and how O -GlcNAcylation might affect β-catenin and E-cadherin functions, the enzyme machinery of O -GlcNAcylation was modulated either with chemical inhibitors or by gene silencing. When O -GlcNAcase (OGA) was inhibited, a global elevation of protein O -GlcNAcylation and increase in the expression of E-cadherin and β-catenin were noted. Concomitantly with enhanced O -GlcNAcylation, β-catenin transcriptional activity were elevated. Additionally, fibroblast cell motility was enhanced. Stable silenced cell lines with adenoviral OGA or adenoviral O -GlcNAc transferase (OGT) were established. Consistent with the results obtained by OGA chemical inhibition by TMG, OGT-silencing led to a significant reduction in β-catenin level. In vivo , murine orthotropic colorectal cancer model indicates that elevated O -GlcNAcylation leads to increased mortality rate, tumor and metastasis development. However, reduction in O -GlcNAcylation promoted survival that could be attributed to attenuated tumor and metastasis development. The results described herein provide circumstantial clues that O -GlcNAcylation deregulates β-catenin and E-cadherin expression and activity in fibroblast cell lines and this might influence EMT and cell motility, which may further influence tumor development and metastasis.