Chinese Hamster Ovary [CHO] cells are the workhorse for production of modern biopharmaceuticals, with total sales of CHO-produced proteins exceeding 100 Billion US Dollars/year today. CHO cells are however immortalised cells with a high propensity for genetic change. Judging from published culture records, CHO cell populations have undergone hundreds of population doublings since their origin in the late 1950s. Different cell populations were established and named during the first two decades after their generation, such as CHO-Pro-, CHO-K1, CHO-DG44, CHO-S, CHO-DUK, CHO-DXB-11, CHO-LA, etc. to indicate origin and certain phenotypic features. These names are commonly used in scientific publications still today. This article tries to raise questions about the relevance of such names. We argue that their use creates a false sense of identity. To substantiate this claim, we discuss the long (and poorly recorded) history of CHO cells as well as their highly complex genetics. Finally, we suggest an alternative naming system for CHO cells which provides more relevant information to the performance of these cells. Implementation of such a system should improve interpretation and comparability between laboratories. This, in turn will help scientific communities and industrial users to attain the full potential of CHO cells.

Viral vectors for gene therapy, such as recombinant Adeno-Associated Viruses (rAAV), are produced in Human Embryonic Kidney (HEK) 293 cells. However, the presence of the SV40 T-antigen-encoding CDS SV40GP6 and SV40GP7 in the HEK293T genome raises safety issues when these cells are used in manufacturing for clinical purposes. We developed a new T-antigen-negative HEK cell line from ExcellGene’s proprietary HEKExpress®, using the CRISPR-Cas9 strategy. We obtained a high number of clonally-derived cell populations and all of them were demonstrated T-antigen negative. Stability study and AAV production evaluation showed that the deletion of the T-antigen-encoding locus did not impact neither cell growth nor viability nor productivity. The resulting CMC-compliant cell line, named HEKzeroT®, is able to produce high AAV titers, from small to large scale.