Summary
Tissue factor (TF), the major initiator of blood coagulation, serves as a regulator
of angiogenesis, tumor growth and metastasis. In several models, TF expression mediates
upregulation of the proangiogenic vasular endothelial growth factor (VEGF) that can
directly act on endothelial cells to promote vessel formation. This occurs through
ligand binding, activation of signaling cascades, signal transduction and alteration
of growth factor expression and is mediated by both, coagulation-dependent and -independent
pathways. Depending on the cell type and the biological settings, TF seems to affect
cellular properties through (i) factor VIIa (FVIIa)-dependent proteolysis of factor
Xa (FXa) and thrombin and subsequent activation of proteinase activated receptor (PAR)
-1 and PAR-2, (ii) through direct FVIIa signaling and mitogen activated protein (MAP)
kinase activation, that is conferred by a not yet identified receptor, (iii) through
interaction of FVII(a) proteolytic activity and signaling of the cytoplasmic domain
and (iv) through cytoplasmic signaling independent of ligand binding. The role of
phosphorylation of the cytoplasmic domain and the pathways controlling phosphorylation
of TF remain poorly understood.
Key words
Angiogenesis - vasculogenesis - VEGF - metastasis - tumor growth