背景资料:FLT1 is a receptor-tyrosine kinase that is activated upon binding with VEGF-A, VEGF-B and PGF. It plays an important role in the development of embryonic vasculature, and as a negative regulator of embryonic angiogenesis by inhibiting excessive proliferation of endothelial cells. However, it can promote PGF-mediated endothelial cell proliferation, survival and angiogenesis in adults, although this seems to be cell-type specific. It also contributes to cancer cell survival, proliferation, migration, and invasion, as well as tumour angiogenesis, metastasis, and recruitment of tumour-infiltrating macrophages. It has a very high affinity for VEGF-A and may function as a negative regulator of VEGF-A signalling by limiting the amount of free VEGF-A and preventing its binding to KDR. Isoforms lacking a transmembrane domain may function as decoy receptors for VEGF-A. Furthermore, it mediates phosphorylation of PI3K, leading to activation of the downstream signalling pathway, as well as mediating the activation of the MAPK signalling pathway, and of the Akt/PKB signalling pathway.