Cooperation between fibronectin and heparin in the mobilization of capillary endothelium.

Angiogenesis is indispensable to sustain promotion and growth of metastases. As a contribution to the understanding of the angiogenesis process, the experiments reported showed that: (a) fibronectin is involved in the mobilization of capillary endothelium which is the first event in angiogenesis; (b) antifibronectin serum can block the mobilization, and neutralization of the antiserum can restore it; (c) the combination of fibronectin + heparin is a powerful mobilizer of capillary endothelium, and (d) fragments of the fibronectin and heparin molecules in combination can mobilize capillary endothelium as effectively as the intact molecules. The results are interpreted to indicate that molecules normally present in the extracellular matrix like heparin and fibronectin, may act as angiogenesis effectors when the physiological structure of the tissue is altered, for instance by lytic enzymes released by metastatic neoplastic cells.