Bcl-2 over-expression reduced the serum dependency and improved the nutrient metabolism in a NS0 cells culture

Cell death in mammalian cell culture: molecular mechanisms and cell line engineering strategies

Cell death is a fundamentally important problem in cell lines used by the biopharmaceutical industry. Environmental stress, which can result from nutrient depletion, by-product accumulation and chemical agents, activates through signalling cascades regulators that promote death. The best known key regulators of death process are the Bcl-2 family proteins which constitute a critical intracellular checkpoint of apoptosis cell death within a common death pathway. Engineering of several members of the anti-apoptosis Bcl-2 family genes in several cell types has extended the knowledge of their molecular function and interaction with other proteins, and their regulation of cell death. In this review, we describe the various modes of cell death and their death pathways at molecular and organelle level and discuss the relevance of the growing knowledge of anti-apoptotic engineering strategies to inhibit cell death and increase productivity in mammalian cell culture.

Enhancement of recombinant protein production in Chinese hamster ovary cells through anti-apoptosis engineering using30Kc6 gene

It was previously reported that silkworm hemolymph (SH) inhibits apoptosis and increases the production of recombinant human erythropoietin (EPO) in Chinese hamster ovary (CHO) cells. The apoptosis-inhibiting component in SH is a member of 30K protein family. In this study, the CHO cell line producing EPO was manipulated genetically to express the 30Kc6 gene encoding a 30K protein in the hemolymph of the silkworm, Bombyx mori. The transient expression of 30Kc6 significantly suppressed the cell death induced by serum deprivation. A stable cell line expressing 30Kc6 with an anti-apoptotic property was established. The stable expression of 30Kc6 inhibited serum-deprivation-induced apoptosis and increased the cell density and EPO titer by 5- and 10-fold, respectively. The positive effects of the 30Kc6 expression on cell viability and productivity were due to the stable maintenance of the mitochondrial activity. The 30Kc6 expression efficiently suppressed the depolarization of the mitochondrial membrane and subsequently balanced the generation/consumption of ATP. The use of the 30Kc6 gene is expected to provide a new method of host cell engineering for improving the productivity of the recombinant protein.

Effect of Bcl-2 overexpression on cell cycle and antibody productivity in chemostat cultures of myeloma NS0 cells

Chemostat cultures of NS0 cell lines were carried out at dilution rates ranging from 0.8 d(-1) to 0.2 d(-1). Compared with the control, the viable cell density of the Bcl-2 cell line was approximately 10% higher at 0.8 d(-1) and increased to 55% when the dilution rate was reduced to 0.2 d(-1). As the dilution rate was reduced, the viability of the two cultures diverged reaching a difference of 43% at 0.2 d(-1). The specific growth rate of the control cells was the same as the dilution rate down to a value of 0.6 d(-1). By contrast, the specific growth rate of Bcl-2 cells was parallel to the dilution rate down to a value as low as 0.3 d(-1). For both NS0 cell lines, the G1 cell population decreased, while the S and G2/M cell populations increased as the dilution rate was reduced. The antibody titer of the control cells increased from 7 to 21 microg.ml(-1) as the dilution rate was reduced from 0.8 to 0.2 d(-1). With an initial increase from 2 to 15 microg.ml(-1) as the dilution rate was reduced from 0.8 to 0.4 d(-1), the antibody titer of the Bcl-2 cells remained constant as the dilution rate was further reduced to 0.2 d(-1). A good correlation between specific antibody production rate and the percentage of G2/M cells was observed.