CHOK1SV GS-KO SSI Expression System: A Combination of the Fer1L4 Locus and Glutamine Synthetase Selection
February 7, 2021
There are several requirements for an ideal host cell line for the production of biopharmaceuticals. The key attribute, however, is stable product expression for a minimum of 50 generations. Integration of the expression system is therefore a crucial step in the cell line development process and can be achieved in two ways: random integration (RI) and site-specific integration (SSI). RI is known to create a relatively large amount of clone phenotypic variations since the number and orientation of integrated gene copies are highly variable. To reduce the variability in expression, the SSI system can be used. This system allows predicting the integration site of the expression system, which simplifies the development of biopharmaceutical products. Historically, SSI systems were less efficient than RI systems, but they provided an advantage over RI hosts by reducing the number of clones variants.
Feary et al. described the construction and evaluation of a CHO-based SSI host: CHOK1SV GS-KO with an expression system integrated at the stable Fer1L4 locus. The clones with the integrated expression system were evaluated for the ability to produce five different mAbs. The concentration of the products was comparable to or greater than those achieved with the best cell lines derived via the state-of-the-art RI approach. All constructed SSI hosts demonstrated excellent performance concerning expression and generational stability. These results show clear advantages of this SSI host over traditional RI systems.
In this work, Genedata Selector was used for the genomic characterization of the new cell line via Targeted Locus Amplification.