Cellular engineering for the high-level production of recombinant proteins in mammalian cell systems

The market for protein-drugs has steadily increased due their increased use as alternatives to traditional small molecule drugs. While some therapeutic proteins have been produced in microbial systems, mammalian cell systems such as Chinese hamster ovary (CHO) cells are widely used as the host cell system. To increase the efficiency of producing therapeutic proteins, many researchers have attempted to solve the critical problems that occur in mammalian cell systems. As a result, several serum-free media and advanced culture methods have been developed, and protein productivity has increased considerably through the development of efficient selection methods. However, the prevalence of apoptosis during mammalian cell culture still remains a significant problem. Based on the understanding of apoptotic mechanisms and related proteins, anti-apoptotic engineering has steadily progressed. In this study, we review the strategies that have been developed for high-level production of recombinant proteins in the CHO cell system via a selection of clones, target-gene amplification, optimization of culture systems and an inhibition of apoptosis through genetic modification.