Intracellular response of CHO cells to oxidative stress and its influence on metabolism and antibody production

Abstract Chinese hamster ovary (CHO) cells are widely used for the manufacture of therapeutic mAbs with high productivity processes generating 5–10 g/L mAb. High productivity processes impose considerable strain on the intracellular metabolic and redox homeostasis resulting in increased oxidative stress. We investigated the mechanisms by which oxidative stress affects the productivity of a mAb producing CHO cell line by controlling bioreactors at dissolved oxygen (DO) set-points ranging from 20 to 175% of air saturation. The results showed that for the 20–75% DO conditions, despite similar growth and viability, there were significant differences in productivity, consumptions of oxygen and amino acids, intracellular redox, and mitochondrial function. Our results demonstrate that as the external dissolved oxygen increased, intracellular H 2 O 2 increased, mitochondrial function diminished, flux into one-carbon metabolism pathway decreased, and cells diverted metabolic activity from mAb production. Intriguingly, although the reductase activities were similar irrespective of the DO concentration, the intracellular reduced-to-oxidized glutathione ratios were low for all conditions, which demonstrated that the intracellular antioxidant mechanisms had difficulties managing oxidative stress. Combined, these results indicate that mAb production may be limited by the cell’s capacity to manage oxidative stress and thus provide a new attribute to leverage during upstream process development.