Strategies for enhancing productivity and quality of monoclonal anti-body in CHO cells

Abstract

Chinese hamster ovary (CHO) cells are the most commonly used mammalian hosts for the produc-tion of therapeutic proteins. One of the strategies for increasing overall product yield CHO cell culture is productivity enhancer like sodium butyrate (NaBu). Though a number of reports have demonstrated that the addition of NaBu to culture media enhances the qp in CHO cells, the addition of NaBu causes apoptotic cell death, and consequently, shortens culture longevity. Therefore, in batch culture of CHO cells, the addition of NaBu often resulted in only marginal increase in recombinant protein production. In the first, I demonstrated that IGF-1(major growth factor in serum-free medium for CHO cells) withdrawal in combination with NaBu addition significantly increased specific productivity of monoclonal antibody (Mab) and markedly retarded cell death, leading to extended culture longevity. For instance, at 3 mM NaBu, cell viability fell below 80% after day 4 in IGF-1-containing medium, but it remained over 80% after day18 in IGF-1-deficient medium. Due to the enhanced qMab and the extended culture longevity, approximately 2-fold increase in total antibody production was achieved in pseudo-perfusion culture with 1 mM NaBu in IGF-1-deficient medium, compared to the culture in IGF-1-containing medium. The change in the expression of cellular proteins, c-Myc and Bcl-2 was investigated. Both the withdrawal of IGF-1 and the addition of NaBu decreased the expression of c-Myc. However, the decrease of c-Myc expression itself is not likely to be the critical factor for the retardation of cell death. To better understand the retarded cell death in IGF-1-deficient medium with NaBu, further investiga-tions would be highly needed. The expression of endogenous Bcl-2 was enhanced by the addition of NaBu in a dose-dependent manner while it was not affected by the withdrawal of IGF-1. In addition, both the with-drawal of IGF-1 and the addition of NaBu reduced metabolic rates, qGlc, qLa...