In 1970, Judah Folkman et al. described a factor secreted by tumors causing angiogenisis and called it tumor angiogenesis factor.[4] In 1983 Senger et al. identified a vascular permeability factor secreted by tumors in guinea pigs and hamsters.[2] In 1989 Ferrara and Henzel described an identical factor in bovine pituitary follicular cells which they purified, cloned and named VEGF. [5] A similar VEGF alternative splicing was discovered by Tischer et al. in 1991.[6] Between 1996 and 1997, Christinger and De Vos obtained the crystal structure of VEGF, first at 2.5 Å resolution and later at 1.9 Å.[7][8][9]