Engineering epidermal growth factor for enhanced mitogenic potency.

Successful use of growth factors in therapeutic and bioprocessing applications requires overcoming two attenuation mechanisms: growth factor depletion and receptor down-regulation. Current ameliorative strategies use physiologically inappropriate high growth-factor concentrations, along with periodic media refeeding in vitro and reinjection or controlled-release devices in vivo. We demonstrate a new approach derived from understanding how these attenuation mechanisms arise from ligand/receptor trafficking processes. Specifically, a recombinant epidermal growth factor (EGF) mutant with reduced receptor binding affinity is a more potent mitogenic stimulus for fibroblasts than natural EGF or transforming growth factor alpha because of its altered trafficking properties.