By
selecting antibodies (blue and yellow) with strong affinity for particular
targets, scientists can label or isolate proteins of interest, or even modulate
the function of those proteins in living cells.
Insights
into cellular productivity could boost generation of proteins with valuable
research and medical applications
The immune system generates antibodies to
mark threats that need to be eliminated, and these protein complexes bind their
targets with remarkable strength and selectivity. Scientists have learned how
to generate cell lines that can produce large quantities of specific
‘monoclonal’ antibodies (mAbs) with desirable properties; these mAbs are
powerful tools for diagnostics, medicine and biological research.
The selection of suitable cell lines is an
important aspect of large-scale production, as these can vary considerably in
their individual mAb output. To assist manufacturing facilities in maximizing
the generation of these precious molecules, Ying Swan Ho’s team at the A*STAR
Bioprocessing Technology Institute in Singapore has identified key features of
top-performing cells in mAb-producing cultures1.
Previous efforts have sought genetic
differences that might affect production, but Ho and co-workers instead devised
a strategy that allowed them to directly compare levels of metabolically active
molecules present in Chinese hamster ovary (CHO) cells that secrete large or
small amounts of a given mAb. “This approach enabled us to gain a deeper
insight into the metabolic milieu that supports recombinant protein production
in mammalian cell cultures,” explains Ho.
The researchers cultivated CHO clones that
were either high or low mAb producers, where productivity differed by up to
28-fold. They observed clear differences between the two groups in levels of
molecules associated with several key metabolic pathways. For example,
high-producer clones contained elevated levels of compounds associated with the
electron transport chain, a mechanism that generates the adenosine triphosphate
(ATP) molecules that power virtually every cellular process.
As energy and mAb production ramp up, cells
also generate large quantities of molecules known as reactive oxygen species,
which can inflict serious damage on the cell. This threat can be neutralized by
molecules such as reduced glutathione (GSH). Ho and co-workers determined that
high producers of mAbs also generated greater amounts of GSH than their
low-production counterparts.
These findings offer a more global view into how
CHO cells might brace themselves to handle the rigors of large-scale protein
synthesis. The researchers now intend to explore the individual contributions
of these various metabolic pathways. “This will be done by evaluating the
effects of increasing the cellular pools of these metabolites on mAb
productivity in different cell lines,” says Ho. With a deeper understanding of
the key pathways, scientists should be able to either improve the selection of
mAb-producing clones or modify culture conditions to ensure that the cells can
work as hard as possible.
The A*STAR-affiliated researchers
contributing to this research are from the Bioprocessing Technology Institute
References
- Chong, W. P. K., Thng, S. H., Hiu, A. P., Lee,
D.-Y., Chan, E. C. Y. & Ho, Y. S. LC-MS-based metabolic
characterization of high monoclonal antibody-producing Chinese hamster
ovary cells. Biotechnology and Bioengineering 109, 3103–3111
(2012). | article
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