Angiogenic factors typically bind to specific receptors on the surface of endothelial cells, which line the inside of blood vessels. This binding activates a cascade of intracellular signals that result in the proliferation, migration, and differentiation of endothelial cells, ultimately leading to the formation of new blood vessels. For example, VEGF binds to its receptors, VEGFR-1 and VEGFR-2, initiating a series of events that promote angiogenesis.