IGFBP3 belongs to the IGFBP family. IGFBP3 functions as the major carrying protein for IGF1 and IGF2 in the circulation, modulates IGF activity, and inhibits cell growth. IGFBP3 binds IGF-II more than IGF-I. Endothelial IGFBP3 forms a ternary complex with IGF-I or IGF-II and an 85 kD glycoprotein (ALS). IGFBP3 levels increase in the presence of IGF-I, insulin and other growth-stimulating factors such as growth hormone, epidermal growth factor, and phorbol esters. IGFBP3 may control angiogenesis and cell responses in the corpus luteum by autocrine/paracrine mechanisms. IGFBP3 also possesses growth-inhibitory and -potentiating effects that are independent of IGF and are mediated through specific receptors. As a specific IGFBP3-binding protein, transferrin blocks IGFBP3-induced cell proliferation and IGFBP3-induced apoptosis. (from OMIM 146732, SWISS-PROT P17936, and NCI)