Optimize, Adapt and Overcome - 39

Optimize, Adapt, and Overcome: Tips from the Cell Line Development Front * How to Improve Cell-Line Productivity

its CHO-K1 cell line. First, Selexis identified an
epigenetic DNA element (SGE) that increases
the transcription rate at the site of integration
by favoring a unique recombination mode.
Each copy of the integrated transgene is in
active transcriptional mode.
Our approach for speed, productivity, and
quality includes a) codon optimization of the
gene of interest (GOI), b) promoter sequence
adapted to CHO cells, c) epigenetic DNA element
(SGE), d) transfection procedure, e) selection with
ClonePix, f ) serum-free media, and g) animalderived component-free feed.
Dr. Powers
The goal in our ExpiCHO system was to improve
protein yield, as this was the primary barrier to
the use of transient CHO systems for screening
of lead molecules. The approach that we took in
the development of this product was to optimize
every aspect of this system (cells, media, feeds,
enhancers, transfection reagents, protocols), and
it was only by this systems-based approach that
we were able to achieve the results that we did:
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orders of magnitude higher titers (up to 3 g/L)
than what is achievable with existing transient
CHO-based systems.

GEN What, if anything, will the

application of CRISPR/Cas9 or related
gene-editing techniques have on future
cell-line development?

Dr. Tedesco
CRISPR is the only available gene-editing approach effective enough to enable knockout
studies even without clonal cell selection. For
example, a pool of cells transduced with a lentiviral CRISPR construct can often harbor knockout
cells at high enough frequency to assess geneknockout effects on drug sensitivity. These "quick
and dirty" assays aren't possible with any other
genome-editing methods.
However, to make reliable cell models for more
sophisticated studies, the targeted genetic
change is just the first step. Downstream
characterization of cells to assess secondary
or off-target effects that might have been

introduced is essential and requires much
time and effort.
Dr. Pankiewicz
The CRISPR/Cas9 technology is a powerful
genome-engineering tool that is winning
popularity due to its efficiency, specificity, and
relative simplicity compared to other technologies. This system was successfully used to mutate
genes in diverse organisms and cell lines
including CHO cells.
I believe that CRISPR/Cas9 technology will be
further used to engineer CHO cells to express
proteins with desired quality, higher specific
productivity, and better stability of expression; to
improve clone selection systems; and to develop
efficient targeted transgene-integration systems.
Dr. Alberts
CRISPR/Cas9 can have a tremendous impact on
cell-line development. Using CRISPR, you can
easily, quickly, and precisely insert your specific
gene and promoter stably into the genome.
Furthermore, the utility of CRISPR allows the

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Optimize, Adapt and Overcome

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