VASCULAR ENDOTHELIAL GROWTH-FACTOR INDUCES TISSUE FACTOR AND MATRIX METALLOPROTEINASE PRODUCTION IN ENDOTHELIAL-CELLS - CONVERSION OF PROTHROMBIN TO THROMBIN RESULTS IN PROGELATINASE-A ACTIVATION AND CELL-PROLIFERATION

Production of vascular endothelial growth factor (VEGF) by cancer cell s at invasive and metastatic sites is an important aspect of tumor ang iogenesis. Although known primarily as a mitogen and a vascular permea bility factor (VPF) for endothelial cells, VEGF/VPF has been proposed to induce the expression of procoagulant factors in endothelial cells. In this study, we have explored the ramifications of VEGF induction o f tissue factor (TF) in human umbilical vein endothelial cells (HUVECs ) and subsequent activation of progelatinase A. Within 3 hr of incubat ion with VEGF/VPF, endothelial cells accelerate TF generation as measu red using chromogenic substrate assays for coagulation factors Xa and thrombin. Incubation of VEGF/VPF-pre-treated cells with prothrombin an d factors X, Va, and VIIa at 37 degrees C and subsequent generation of thrombin resulted in activation of secreted endothelial progelatinase A as demonstrated by gelatin zymography. Anti-thrombin III or antibod ies to TF inhibited thrombin generation and progelatinase A activation . VEGF/VPF also directly increased HUVEC secretion of interstitial col lagenase, tissue inhibitor of metalloproteinases (TIMP-1) and, to a le sser extent, gelatinase A. The effect of thrombin on endothelial proli feration in serum-free media was examined. Thrombin was a growth facto r for HUVECs at a Tower dose than that required for progelatinase A ac tivation. Whereas TIMP-2 abrogated thrombin-induced progelatinase A ac tivation, it had no significant effect on thrombin-induced endothelial cell growth. We propose that an early step in tumor angiogenesis invo lves VEGF-induced thrombin generation and increased MMP production wit h subsequent activation of endothelial progelatinase A and degradation of the underlying basement membrane. (C) 1998 Wiley-Liss, Inc.