Molecular mechanisms linking thrombosis and angiogenesis in cancer

In this brief review, the authors concentrate on selected issues related to the newly described role of tissue factor (TF), the major activator of mammalian blood coagulation, as a regulator of angiogenesis and of tumor growth and metastasis. Previously, TF had been considered strictly as the primary activator of the coagulation cascade; however, it has recently been demonstrated that overexpression of the TF gene in murine tumor cells leads to increased transcription of the gene for vascular permeability factor/vascular endothelial growth factor (VEGF), a proangiogenic factor and decreased transcription of the gene for thrombospondin (TSP), an antiangiogenic factor Conversely, underexpression of TF leads to decreased VEGF and increased TSP transcription. When grown in mice and compared With low TF-producing tumor cells, high TF-producing tumor cells stimulate angiogenesis by approximately twofold. This effect of TF appears to be independent of its clot-promoting procoagulant activity (PCA) and suggests that TF regulates the angiogenic properties of tumor cells by altering the production of growth regulatory molecules (for example, VEGF) that can act on vascular endothelial cells (VECs). There is substantial preliminary evidence that the regulation of tumor angiogenesis can be mediated by TF via both fibrin clotting-dependent and fibrin clotting-independent mechanisms. (C) 1997, Elsevier Science Ltd.