Altered IGFBPs are able to bind IGF, but the release is inhibited by resistance to protease cleavage and/or reduced binding to extracellular matrix (ECM). Alterations have been made in IGFBP-2 to the linker domain in particular and to two amino acid motifs found to be important for ECM binding. IGF-1 mediated proliferation of cancer cells have been inhibited by use of the altered IGFBPs.