Integrin regulation of beta-catenin signaling in ovarian carcinoma.

Reversible modulation of integrin-regulated cell-matrix adhesion and epithelial (E)-cadherin-mediated cell-cell adhesion plays a critical role in the establishment of ovarian cancer metastases. In contrast to most epithelial cell-derived tumors that down-regulate E-cadherin expression during progression, acquisition of E-cadherin expression accompanies malignant transformation of the ovarian surface epithelium and is maintained in peritoneal metastases. Metastatic epithelial ovarian cancer cells are disseminated intraperitoneally and preferentially adhere via integrins to interstitial collagens in the peritoneal cavity. This study was undertaken to determine whether integrin engagement influences E-cadherin and β-catenin localization and function. The data demonstrate that multivalent integrin engagement results in increased internalization of E-cadherin, inhibition of GSK-3β, elevated levels of nuclear β-catenin, increased β-catenin-regulated promoter activation, and transcriptional activation of Wnt/β-catenin target genes. Blocking β-catenin transcriptional control with inhibitor of β-catenin and Tcf-4 reduces cellular invasion, suggesting a key role for β-catenin nuclear signaling in EOC invasion and metastasis. These studies support a model wherein cell-matrix engagement regulates the functional integrity of cell-cell contacts, leading to increased β-catenin nuclear signaling and enhanced cellular invasive activity. Furthermore, these results provide a mechanism for activation of Wnt/β-catenin signaling in the absence of activating mutations in this pathway.