Vascular endothelial growth factors(VEGFs)respectively bind to each of three receptor tyrosine kinases (RTKs),known as Flt-1,KDR and Flt-4.Since VEGFs and their respective families of receptor tyrosine kinases (VEGFRs)are critical proteins which can regulate vascular development during angiogenesis,we decided to explore the inhibitory effects of soluble kinase insert domain-containing receptor(sKDR)on endothelial cells and angiogenesis.Total RNA was extracted from human umbilical vein endothelial cells(HUVEC),and cDNA of extracellular domains 1-4 was amplified and recombined with pQE40 vector.After being expressed,affinity purified,renatured and analyzed by Western blot,the sKDR was assayed for its effects on endothelial cells by[3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide](MTT),and on angiogenesis by chick chorioallantoic membrane(CAM)experiment.sKDR cDNA of 1150 bp was obtained via real-time polymerase chain reaction(RT-PCR),and sKDR was expressed by pQE40 procaryotic expression system,purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)analysis with only one band and proved by Western blot.MTT assay demonstrateds that sKDR could inhibit the VEGF-stimulated HUVEC from proliferation,and CAM experiment showed sKDR could block the VEGF-induced angiogenesis.sKDR has the biological activity to bind with VEGF ligands and is a potential target for tumor anti-angiogenesis therapy.