Stable and Transient Expression of Human Coagulation Factor IX in Mammalian Expression Systems; CHO Versus HEK Cells

[Background]Selecting a host system for the expression of recombinant proteins should be carefully evaluated prior to the initiation of any bio therapeutic development programs. Since different hosts express proteins with various efficiencies and with different posttranslational modifications, changing hosts may impact the expected activity of the protein. The main expression systems have members of the mammalian cell family, however, there are remarkable differences between the species. The most generally used mammalian hosts for the production of recombinant proteins are CHO and HEK293 cells.[Objectives]In order to compare the differences between HEK versus CHO cells, the human coagulation factor IX in a transient and stable expression was examined.[Methods]After transfection of CHO and HEK cells with an hFIX-expressing mammalian plasmid, pcDNA-hFIX, transient expression was analyzed on the culture supernatant during 72 hours. The stable clones were also recovered after 10 weeks of geneticin selection.The expression and activity of the hFIX was evaluated by performing enzyme-linked immunosorbent assay (ELISA) as well as a coagulation test, respectively. The γ-carboxylation of the hFIX was confirmed by evaluation of the expressed protein, after being precipitated with barium citrate.[Results]Although the stable CHO clones secreted hFIX protein 30% higher than HEK cells, the transient HEK cell line proved to be superior in the production of total hFIX protein (%42 increased) and functional hFIX (%29 higher) relative to the CHO cell line. Moreover, specific activity and the fully γ-carboxylated hFIX are almost constant in transient and stable expression, indicating that γ-carboxylation efficiency in both CHO and HEK cell lines is almost equal.[Conclusions]In conclusion, transient transfection studies with HEK cells provide a simple and strong method for a high production of recombinant proteins in weeks, a process which is more time consuming in the CHO cell line.