As their name suggests, Vascular Endothelium Growth Factors (VEGFs) are a family of proteins which play a critical role in angiogenesis by stimulating the proliferation and migration of blood vessels endothelial cells. This family comprises five members in mammals: VEGF-A (also referred to as VEGF) to VEGF-D as well as the Placental Growth Factor (PGF).

Alternative splicing of mRNA from the 8-exon VEGFA gene leads to multiple isoforms of VEGF-A, based on exons 6 and 7, and divides them into two groups according to the eighth exon splice site: pro-angiogenic isoforms (noted VEGF_xxx) and anti-angiogenic isoforms (noted VEGF_xxxb).

More than other living cells, tumor cells have high needs in oxygen and nutrients to sustain their rapid growth. Cells located in the centre of the tumor usually have a lack of oxygen supply and then produce high levels of VEGFs to stimulate angiogenesis in their neighbourhood. Inhibition of VEGFs activity thus led to promising clinical studies to inhibit cancer cells proliferation.