Cell Survival in CHO Cell Cultures Grown in a Defined Protein Free Medium

Abstract

Animal cells, primarily hybridomas, important for diagnostic and pharmaceutical production have been shown to die almost exclusively via apoptosis when entering the stationary phase. Recently similar reports have been presented for CHO (Chinese Hamster Ovary) cells grown in batch cultures under optimal conditions for high product yield ¹. Experiments performed in small scale using a defined protein free medium, with the sole addition of recombinant insulin, enabled us to investigate the importance of physiological parameters and their effect on cell survival. We show here that a CHO cell line engineered to produce a recombinant therapeutic protein is capable of inducing the apoptotic programme under batch culture conditions in a 2 L reactor, as measured by the TUNEL assay (DNA end-labeling). Cells are arrested in the Gl phase of the cell cycle though insulin is present in excess and no apparent depletion of nutrients is at hand. Proliferation ceases and viability decreases although the concentration of inhibiting metabolites is low.