Description_x000D_ Biochem/physiol Actions_x000D_ Human IGFBP-3 is the major insulin-like growth factor (IGF) binding protein in plasma, where it exists in a ternary complex with IGF-I or IGF-II and the acid-labile subunit (ALS)._x000D_ IGFBPs (insulin like growth factor binding proteins) regulate bioavailability of IGFs (insulin like growth factors) in cells. Binding between IGFs and IGFBPs reduces the availability of the IGFs. However, IGFBPs also concentrate IGFs in specific areas to potentiate their effects at right time. IGFBP3 binds to IGF-1. It is a tumor suppressor and is downregulated in many cancers. In serum, IGFs, IGFBP3 and the acid labile subunit (ALS) exist together as a complex. This complex is important for increasing the half life of serum IGFs._x000D_ Physical form_x000D_ Lyophilized from a 0.2 μm filtered solution in 30% acetonitrile and 0.1% TFA._x000D_ Analysis Note_x000D_ The biological acitivity is measured as the ability to inhibit the biological activity of 14 ng/ml recombinant human IGF-I on MCF-7 cells.