A need exists for a source of biologically active human proteins, particularly those with complex tertiary or quaternary structure which require modification for full biological activity. Current production of recombinant molecules by bacteria has limited ability to satisfy this need. Cultured mammalian cells provide greater promise as production systems. Cell lines, such as Chinese hamster ovary (CHO), have been shown capable of expressing and properly processing a variety of human recombinant proteins, and are adaptable to large- scale cultivation in serum free media. This work addresses the need for an improved expression system to facilitate the production of proteins that are composed of two different subunits. The system proposed will utilize a plasmid vector containing transcription promoters from SV40 and the mouse mammary tumor virus, which is integrated into the genome of Chinese hamster ovary cells (CHO). In this construction, both promoters will be capable of directing high levels of production, and the ratio of synthesis of the two proteins produced can be adjusted to achieve the proper ratio of precursor proteins for efficient folding and final assembly. The plasmid will be constructed and tested for expression using bacterial reporter genes. Growth and expression in serum free media will be optimized in the production of human Insulin-like Growth Factor-1 (1GF-1), a small biologically important peptide currently produced by this laboratory using a recombinant bacterial system. The medical use of peptides and proteins is an immature pharmaceutical market. However, clinical usage is expected to grow substantially during the next five years. Data indicates the current annual market for medically important peptides/proteins exceeds $175.6 million. However, peptides world markets associated with the mammalian cell technology addressed in this proposal could reach $3.04 billion by 1991.
