Enhanced transient recombinant protein production in CHO cells through the co-transfection of the product gene with Bcl-xL

Transient gene expression is gaining popularity as a method to rapidly produce recombinant proteins in mammalian cells. Although significant improvements have been made, in terms of expression, more improvements are needed to compete with the yields achievable in stable gene expression. Much progress has come from optimization of transfection media and parameters, as well as altering culturing conditions to enhance productivity. Recent studies have included cell lines engineered for apoptosis resistance through the constitutive expression of an anti-apoptotic protein, Bcl-x(L). In this study, we examine an alternative method of using the benefits of anti-apoptotic gene expression to enhance the transient expression of biotherapeutics, namely, through the co-transfection of Bcl-x(L) and the product-coding gene. CHO-S cells were co-transfected with the product-coding gene and a vector containing Bcl-x(L) using polyethylenimine. Cells co-transfected with Bcl-x(L) showed reduced levels of apoptosis, increased specific productivity, and an overall increase in product yield of approximately 100%. Similar results were produced by employing another antiapoptotic protein, Bcl-2 delta, in CHO cells, or through the co-transfection with Bcl-x(L) using HEK-293E cells. This work provides an alternative method for increasing yields of therapeutic proteins in TGE applications without generating a stable cell line and subsequent screening, which are both time- and resource-consuming.