Integrin αvβ3/Vitronectin Interaction Affects Expression of the Urokinase System in Human Ovarian Cancer Cells

Sandra Hapke,Horst Kessler,Nuria Arroyo De Prada,Anke Benge,Manfred Schmitt,Ernst Lengyel,Ute Reuning

doi:10.1074/jbc.m100181200

Abstract

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.

Highlights

Tumor invasion into the surrounding tissue and metastasis require a finely tuned regulation of the formation and the loosening of adhesive contacts of tumor cells with the extracellular matrix (ECM).1 These complex events depend on the concerted and controlled expression of adhesion molecules and proteolytic enzymes [1]
Human Ovarian Cancer Cells Adhere with Different Strength to ECM Components—Adhesion of OV-MZ-6 cells to the ECM proteins LN, collagen type I (Col-I), collagen type IV (Col-IV), FN, and VN was analyzed in comparison with cells that were allowed to attach to noncoated cell culture dishes (Fig. 1A)
Expression of urokinase type plasminogen activator (uPA), uPAR, and plasminogen activator inhibitor type-1 (PAI-1) Is Regulated as a Function of Ovarian Cancer Cell Adhesion to Purified ECM Proteins—OV-MZ-6 cells were cultivated in cell culture plates precoated with selected ECM proteins and the antigen content of uPA and PAI-1 determined in cell culture supernatants as well as that of uPAR in cell lysates (Fig. 1B)

Summary

Introduction

Tumor invasion into the surrounding tissue and metastasis require a finely tuned regulation of the formation and the loosening of adhesive contacts of tumor cells with the extracellular matrix (ECM).1 These complex events depend on the concerted and controlled expression of adhesion molecules and proteolytic enzymes [1]. VN-mediated modulation of uPA, uPAR, and PAI-1 expression could be reversed to expression levels noticed in OV-MZ-6 cells plated on noncoated or PL-coated cell culture dishes when OV-MZ-6 cells were cultivated in the presence of the cyclic peptide cRGDfV, which disrupts ␣v␤3/VN interaction and OV-MZ-6 cell adhesion to VN (data not shown).

Results

Conclusion