Effect of Bcl-2 and membrane proteoglycan overexpression on transient gene expression in mammalian cells

Abstract

Chinese hamster ovary (CHO) and human embryonic kidney 293 (HEK293) cells are the most popular host cells for transient production of therapeutic proteins. Recently, the transient gene expression (TGE) system has been considered as an appealing alternative to stable cell line construction technology for the rapid and cost-effective production of therapeutic proteins for high-throughput screening and pre-clinical analysis (Rosser et al. 2005). HEK293E cells have been used for the TGE platform due to their high transfection effi-ciency and productivity. CHO cells are preferred because protein production with similar characteristics in further stable cell line production, even though productivity is lower than HEK293E cells. These host cells require high transfection efficiency in order to enhance productivity because plasmids are retained and ex-pressed in an episomal condition. In addition, every batch to produce recombinant proteins using the TGE technique needs a discrete transfection process. Therefore, the selection of an inexpensive and efficient trans-fection reagent is the primary interest. Taken together, attempts to enhance the productivity using the TGE system with efficient gene delivery polymer, polyethylenimine (PEI), in CHO and HEK293 cells have been made in this study. PEI, a cationic polymer, has been used widely in TGE because it is inexpensive and capable of effi-cient gene delivery. PEI condenses DNA into nanostructures, forming DNA/PEI polyplexes, which are then internalized through endocytosis. The formulation of DNA/PEI polyplexes, which is often described as the N/P ratio, plays an important role in both transfection efficiency and cell viability. The transfection efficiency is inversely related to the toxicity of PEIs. More PEIs increase the transfection efficiency but induce more cytotoxicity. PEI is known to have relatively low cytotoxicity at working concentrations, yet it can induce cytotoxicity because a large amount of free PEIs ca...