The original member of the family of endothelial cell growth factors referred to as vascular endothelial growth factors. Vascular endothelial growth factor-A was originally isolated from tumor cells and referred to as "tumor angiogenesis factor" and "vascular permeability factor". Although expressed at high levels in certain tumor-derived cells it is produced by a wide variety of cell types. In addition to stimulating vascular growth and vascular permeability it may play a role in stimulating vasodilation via nitric oxide-dependent pathways. alternative splicing of the mRNA for vascular endothelial growth factor a results in several isoforms of the protein being produced.