ANGIOGENIC FACTORS ARE HEMATOPOIETIC GROWTH-FACTORS AND VICE-VERSA

Angiogenic factors are potent growth factors promoting proliferation a nd differentiation of vascular endothelial cells. Recent evidence sugg est that these factors also promote hematopoietic cell growth. The maj or group of angiogenic growth factors is the fibroblast growth factor (FGF) family. Two prototypes, acidic FGF and basic FGF, have been demo nstrated to interact with granulopoiesis and megakaryocytopoiesis. Bas ic FGF stimulates granulopoiesis in long term bone marrow cultures whi le acidic and basic FGF promote megakaryocytopoiesis. These effects ar e presumably mediated via specific FGF receptors, that have been ident ified in bone marrow and leukemia cell lines. Besides the FGF family, angiogenic inhibitors such as platelet factor-4 (PF-4) have been found to exhibit an inhibitory effect on megakaryocytopoiesis. In contrast, it has been demonstrated that hematopoietic growth factors including granulocyte-macrophage colony-stimulating factor (GM-CSF), or erythrop oietin promote angiogenesis in vivo and in vitro. In light of these re cent observations and the common origin of endothelial cells and hemat opoietic cells, it is suggested that angiogenic factors are hematopoie tic growth factors and vice versa. However, these data must be interpr eted with caution and a careful in vivo evaluation should be donebefor e these observed in vivo effects are proven to be significant to the p hysiopathology of hematopoiesis or angiogenesis.