(173e) The Metabolic Phenotypes of Industrial IgG-Expressing CHO Cells

CHO cells are now accumulating antibody titers that exceed their viable cell density on a mass basis.  This has largely been the product of dedicated efforts in media optimization and high-throughput screening.  Still, surprisingly little is known about the underlying metabolic reprogramming associated with the high-titer phenotype.  Currently the biotech industry relies predominantly on two CHO expression systems, glutamine synthetase (GS) and dihydrofolate reductase (DHFR).  First, we considered a fed-batch DHFR system.  During the peak antibody production phase, total nutrient consumption was reduced by 40% in comparison to exponential growth phase, indicating that substantial increases in carbon and energetic efficiency were associated with peak antibody production.  Through ¹³C metabolic flux analysis (MFA) and examination of intracellular redox state, we found that elevated oxidative mitochondrial metabolism corresponded with peak antibody production.  In contrast, peak cell growth was characterized by elevated glycolytic metabolism. 

Second, we performed experiments to examine the metabolic rewiring of a fed-batch GS system using ¹³C MFA and metabolomics.  We directly compared ten unique IgG-secreting GS clones to two empty-vector (i.e., non-producing) GS clones. We observed drastic elevations in the TCA cycle flux of IgG-producing clones, which did not occur in the empty-vector GS clones.  This study enabled us to systematically assess the impact of IgG production on the central metabolism of CHO host lines, in contrast to the impact of GS overexpression alone.  This presentation will discuss the central metabolic trends observed among both GS and DHFR expression systems as a means to provide potential metabolic targets to further enhance IgG productivity and titer.