We Evaluate the ExpiCHO-S Cell Line For Protein Expression
Within the Department of Protein Science and Structural Biology at Sygnature Discovery, we offer a range of eukaryotic cell lines to express recombinant protein(s). These include HEK cell lines such as HEK293-6E (on licence from the NRC, Canada) and Expi293F (on licence from Thermo Fisher) as well as a CHO line, CHO-3E7 (also on licence from the NRC).
Due to an increase in demand for our mammalian expression platforms we decided to benchmark the ExpiCHO-S line (on an R&D license from Thermo Fisher Scientific). To evaluate this, we compared the expression of secreted TIMP2 protein. We have extensive experience producing this target protein over several years and cell-lines. This protein also has intermediate expression levels making it a good candidate for assessing changes in expression levels. We tested expression in CHO-3E7 cells, using our in-house optimised protocol, and in ExpiCHO-S cells, using the Thermo Fisher Scientific transfection kit. Thermo Fisher suggests three different protocols for protein expression in ExpiCHO-S, called STANDARD, HIGH and MAX. In the standard protocol, ExpiCHO-S are transfected and incubated at 37oC until harvest, with a feed at 24 h post-transfection. The high protocol includes a feed at 24 h like the standard, but also a temperature shift at 32oC post-feeding. The max protocol has two feeds, at day 1 and day 5 post-feeding, in addition to the temperature shift.
Our data on the expression of secreted TIMP2 show a significant increase in expression using all three protocols for ExpiCHO-S (Figure. 1). These results were mirrored by the expression of our internal control (mCherry, Figure 2 – left), suggesting ExpiCHO-S in combination with the supplied Thermo Scientific protocols would be a great addition to our expression portfolio
Figure. 1. Coomassie stain (left) and Anti-His HRP-mouse monoclonal, chemiluminescence (right) after Day 8 harvest.
Interestingly, the expression of intracellular mCherry did not appear to improve significantly in ExpiCHO-S cells (Figure. 2 – right) when compared to our in-house CHO-3E7 production platform, suggesting that CHO-3E7 might be a better choice for intracellular proteins due to the difference in media/transfection costs.
Figure. 2. mCherry control expression from an intracellular (left) and secreted (right) construct.
These findings highlight how screening different cell-lines for different targets early in the process could potentially save time and money in order to deliver the desired quantity of recombinant protein(s).
Here at Sygnature Discovery we are happy to assist our clients in early screening to identify the process that is best for their particular project needs.
