An isolated protein complex is provided which includes a growth factor, growth factor binding protein and vitronectin. Preferably, the isolated protein complex includes an insulin-like growth factor-I, insulin-like growth factor binding protein-3 or insulin-like growth factor binding protein-5 and vitronectin. Also provided are methods of modulating cell proliferation and/or migration by administering said protein complex for the purposes of wound healing, skin repair and tissue replacement therapy. Conversely, by using agents that disrupt growth factor protein complexes formed in vivo, growth factor-driven cell proliferation and/or migration may be suppressed such as for the purposes of treating cancers, psoriasis, atherosclerosis and wounds prone to hypertrophic scarring.