Positive expression of E-cadherin suppresses cell adhesion to fibronectin via reduction of α5β1 integrin in human breast carcinoma cells

E-cadherin mainly mediated the epithelial cell–cell adhesion, and integrin signaling can modulate the signaling pathway of E-cadherin in the different levels. Up to now, however, it is still unclear that whether E-cadherin could interfere with cell–matrix interaction, a typical adhesion through integrins. In this study we investigated the effects of E-cadherin on cell–matrix adhesion and α5β1 integrin expression in human breast carcinoma cells. It was found that either mRNA or protein level of α5 and β1 subunits of integrin decreased in E-cad-231 compared with Mock-231. Furthermore, the promoter activity of α5 gene was inhibited in E-cad-231 compared with Mock-231. Consistently, phosphorylated focal adhesion kinase, a closer key downstream protein kinase of integrin signaling, were also down-regulated in E-cad-231. Furthermore, distribution of β-catenin was observed and data showed β-catenin was accumulated in the nucleus in Mock-231, while disappeared from the nucleus and mainly accumulated near the cell surface membrane in E-cad-231. LiCl, a molecule that can inhibit the GSK-3β activity and down-regulate β-catenin degradation, could inversely stimulate expression of α5 and β1 integrin. Taken together, these results indicated that positive expression of E-cadherin inhibits the cell adhesion to extracellular matrix mediated by α5β1 integrin signaling.