Integrin alpha(v)beta(3)/vitronectin interaction affects expression of the urokinase system in human ovarian cancer cells.

The urokinase type plasminogen activator (uPA), together with its receptor uPAR and the plasminogen activator inhibitor type-1 (PAI-1) plays a pivotal role during tumor invasion and metastasis. Integrins, via interaction with the extracellular matrix (ECM), control cell adhesion and motility. The two systems are functionally linked because uPAR and PAI-1 bind to the ECM component vitronectin (VN). Because integrin signaling alters gene expression patterns, we investigated whether the expression levels of uPA, uPAR, and PAI-1 are affected by ECM/integrin interactions. Expression of uPA, uPAR, and PAI-1 was significantly enhanced when human ovarian cancer cells (OV-MZ-6) were cultivated on fibronectin or collagen type IV. In contrast, VN induced down-regulation of uPA and uPAR while increasing PAI-1 by up to 4-fold. VN-dependent decrease of uPA protein was paralleled by a significant reduction of uPA promoter activity that was even more pronounced upon alpha(v)beta(3) overexpression and depended on the presence of intact Rel protein-binding sites. The activity of Rel transcription factors was also significantly reduced upon alpha(v)beta(3)-mediated cell adhesion to VN. The activity of the Rel-unresponsive PAI-1 promoter was up to 5-fold induced as a function of alpha(v)beta(3)/VN interaction. Thus, the balance between available concentrations of uPA, uPAR, PAI-1, and integrins in human ovarian cancer cells might provide a switch within the regulation of their invasive phenotype.