VEGF plays several key roles in the invasive growth and metastasis of malignant tumours: VEGF secreted by tumour cells specifically binds to three different tyrosine kinase receptors (VEGFR1/2/3) in vascular endothelial cells and phosphorylates tyrosine residues in the intracellular domains after the formation of the dimer. This evidence concerns the gene FLT1 and neoplasm.