HEK-INV for high titer TGE
Several cell lines are used for the production of recombinant proteins and antibodies, whereby CHO cells are the most widely used in biopharmaceutical production. To guarantee high product consistency it is highly desirable to use the same host cell line for early stage operations and later production. However, cell specific productivity of CHO cells in TGE processes is now often lower than in human cells. On the other hand, HEK293 cells are the most widely used human cell lines for expression of recombinant proteins in research and industrial applications. Both are easy to handle and grow well in suspension in CD-ACF (chemically defined and animal component free) culture media. This is very important since actively dividing cells are transfected more efficiently than non-dividing cells as the nuclear envelope breakdown during cell division promotes nuclear transport of DNA.
During recent decades, many HEK293 descendants have been generated by genetic modification, directed evolution and cloning. One of the most popular genetic elements for modification is the EBNA-1 gene in conjunction with the oriP of the Epstein-Barr virus which enhances protein expression by episomal replication and maintenance of plasmids, as well as nuclear import by containing a nuclear localization signal (NLS). Similar modifications and improvements can be achieved by using the SV40 large T-antigen of the SV40 virus in conjunction with the SV40ori. All in all, HEK293 cells are available as more or less native cells (e.g. 293 Freestyle or ATCC CRL-1573) or engineered cells (ATCC CRL-11268, ATCC CRL-10852) whereby most companies appear to have implemented their “own” HEK cell line. Indeed, InVivo uses the recently finalized HEK-INV cell line for high titer transient gene expression. To generate this optimized host cell line, we utilized a directed evolution approach. For this purpose, an iterative process of evolution rounds followed by metabolomic phenotype analysis and selection of cells was performed. In detail, we mainly focused on productivity and growth characteristics. This way, the new cell line showed a 3‑fold increase in human IgG1 productivity in comparison to the parental HEK293 host cell line.
Based on the original CHO cell line generated by Puck in 1957, nowadays various CHO cell lines are used for transient gene expression. These cell lines are mainly derived from four descendants – the CHO-K1 by Kao and Puck (1968), the dhfr-negative variants DG44 and DUK X B11 by Urlaub and Chasin (1983) and CHO-S by Tilkins (1991). CHO cells are known to have an instable genotype, so it must be assumed that many quasispecies are used in different laboratories. Similar to the HEK cell family, genetic modified CHO cell lines are also available e.g. CHO-T. In addition, InVivo is currently developing its own CHO TGE platform based on a DG44 derivate.