Enhancing CHO cell productivity through a dual selection system using
Aspg and Gs in glutamine free medium
Abstract
The dominant method for generating Chinese hamster ovary (CHO) cell
lines that produce high titers of biotherapeutic proteins utilizes
selectable markers such as dihydrofolate reductase (Dhfr) or glutamine
synthetase (Gs), alongside inhibitory compounds like methotrexate (MTX)
or methionine sulfoximine (MSX), respectively. Recent work has shown the
importance of asparaginase (Aspg) for growth in media lacking
glutamine–the selection medium for Gs-based selection systems. We
generated a Gs/Aspg double knockout CHO cell line and evaluated its
utility as a novel dual selectable system via co-transfection of
Gs-Enbrel and Aspg-Enbrel plasmids. Using the same selection conditions
as the standard Gs system, the resulting cells from the Gs/Aspg dual
selection showed substantially improved specific productivity and titer
compared to the standard Gs selection method, however, with reduced
growth rate and viability. Following adaptation in selection medium, the
cells improved viability and growth while still achieving
~5-fold higher specific productivity and
~3-fold higher titer than Gs selection alone. We
anticipate that with further optimization of culture medium and
selection conditions this approach would serve as an effective addition
to workflows for the industrial production of recombinant
biotherapeutics.