Phosphoinositide 3 kinase is critical for survival, mitogenesis and migration but not for differentiation of endothelial cells.
Angiogenesis involves endothelial cell invasion and migration into the surrounding tissue where cells differentiate, to form new lumen-containing vessels. We have investigated the role of phosphoinositide 3-kinase (PI3-kinase) in vascular endothelial growth factor (VEGF)- and fibroblast growth factor (FGF)-induced angiogenesis. Angiogenesis in vivo in chick embryos was inhibited by treatment with the PI3-kinase inhibitors wortmannin and LY294002. Stimulation of primary bovine capillary endothelial (BCE) cells with FGF-2, VEGF-A(165), or a combination of the two induced PI3-kinase activity in vitro and subsequent activation of the serine/threonine kinase Akt. The combination of FGF-2 and VEGF-A(165) led to an additive response. Activation of PI3-kinase was strictly required for FGF-2- and VEGF-A(165)-induced migration and DNA synthesis of BCE cells. Tubular morphogenesis was unaffected by treatment with wortmannin or LY294002, but survival of the tubular structures was dependent on PI3-kinase activity. VEGF-A(165) and FGF-2 induced increased stability of the tubular structures in a synergistic manner. These data indicate that PI3-kinase activity is required for migration, mitogenicity and survival but not for differentiation of endothelial cells during angiogenesis.