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Cell Line Optimization

Despite improved production yields over the past years improvement in cell line generation, stability and yields is still of relevance. Endogenous alternatives to CMV and EF1a promoters could lead to more stable cell lines with higher yields.

Furthermore, alternative cell line systems with specific characteristics are not as developed as CHO cells and are in need of increased production yields.


We apply our SuRE™ screening approach to identify the optimal (combination) of regulatory elements to drive transgene expression and our AIM™ technology to identify favourable integration sites and their expression levels.

Organism and condition-specific promoters for optimal expression vector

Cell culture systems for production of recombinant proteins have seen a strong development since the early 2000’s. In CHO cells, the working horse for the production of therapeutic proteins, antibody production levels have increased from less than 0.5 gr/l in 2003 to an average of 4 gr/l today, peaking at double that at times. To date, CMV and EF1a have been the go to promoters. However, particularly CMV is known to be susceptible to methylation losing expression over time.


Using endogenous promoters should provide a more stable and higher expression levels. Recently we have demonstrated that for CHO cell lines. In situations, it is preferred towork with inducible promoters. For instance when producing viral vectors in HEK cell lines. The expression of the Rep protein required but it is toxic to the cell. Controlling when it is expressed will benefit the cell line and manufacturing process.  Improving expression vectors with organism and condition-specific promotors can impact yields for these systems significantly.


Our standard screening process relies on an initial genome-wide SuRE™ screen in a cell-line system. This allows us to identify approximately 100 promising candidate promoters and enhancers from an exhaustive screen of the entire genome. In a next round another exhaustive screen is performed for all potential combinations (of 2) of all 100 elements. We refer to this as the ‘hybrid’ screen and the optimal promoter/enhancer combination resulting from this screen is then transferred for use in your expression vector. 

Off-the-shelf promoters available

For CHO cell lines we have generated endogenous promoters which are available for testing and licensing. Please go to our "off-the-shelf"page for more information.

Our Annogen promoter, identified in platform-specific and condition-specific screening program

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AIM™ Integration Site Mapping

In addition, we can identify gene insertions and asses their expression levels for > 100,000 integrations in parallel. The output of this screening for your cell line will give you more insight in cell line generation approach. We can identify e.g. CHO or HEK sites for maximum expression levels, select specific sites for targeted (low copy) integration, identify inducible sites, etc.

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