Large-Scale Transient Expression of Therapeutic Proteins in Mammalian Cells

Research of the molecular and cellular biology of mammalian cells would be highly restricted if not for the development of methods to deliver exogenous DNA into cultivated cells. Transient transfection of mammalian cells became a routine research tool following a landmark publication by Graham and Van der Eb, who presented the calcium phosphate method as an assay to test the infectivity of purified viral DNA in 1973 ( 1 ). For the first time, this technique allowed the delivery of genes into animal cells without the help of a virus. Novel techniques for nonviral gene transfer have been developed and improved since then. Today, numerous commercial transfection agents for a wide range of cell lines are available ( 2 ). This chapter focuses on the two leading methods for large-scale applications of transient gene expression (TGE): calcium phosphate DNA coprecipitates ( 3 , 4 ) and polyethylenimine (PEI)-DNA polyplexes ( 5 , 6 ). Although calcium phosphate DNA coprecipitation is a well-established method that has been modified for high efficiency by many authors ( 7 – 12 ), PEI has only recently been developed as a transfection vehicle ( 13 – 15 ), but it has achieved rapid acceptance for large-scale suspension transfections because of its simplicity in handling and its efficacy of gene transfer to many different cell types. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.