Genetic Factors Affecting the Quality of Recombinant Therapeutic Proteins in CHO Cells

Recombinant therapeutic proteins (RTPs) are widely used to treat various major diseases. Chinese hamster ovary (CHO) cells are the preferred mammalian cell expression system for the production of RTPs. However, maintaining high productivity while ensuring good-quality RTPs is still challenging. Glycosylation, aggregation, charge variants, and degradation are the main quality attributes of RTPs and can impact their safety, biological activity, stability, and half-life. Modifications of associated genetic factors have been performed to improve the quality of the RTPs. For example, knocking out the α-1,6-fucosyltransferase (FUT8) gene results in the production of fucose-free antibodies, significantly enhancing antibody-dependent cellular cytotoxicity (ADCC). Overexpressing the molecular chaperone GRP78 reduces antibody aggregation rates while improving cell survival rates. Knocking out the carboxypeptidase D (CpD) gene completely eliminates C-terminal lysine heterogeneity, thereby improving the antibody charge uniformity. The deletion of the insulin-degrading enzyme (IDE) gene nearly eliminates insulin degradation. Understanding the genetic factors that influence the quality of therapeutic proteins during CHO cell culture is essential for the production of high-quality therapeutic proteins. This review summarizes the genetic factors contributing to RTP heterogeneity in CHO cells and discusses innovative strategies to address this heterogeneity, such as CRISPR/Cas9-mediated gene knockout, synergistic glycosyltransferase overexpression, and host cell engineering.