Investigating the use of DNA repair as a strategy to enhance production stability in Chinese Hamster Ovary (CHO) cell lines

Chinese hamster ovary (CHO) cells are the preferred and most widely used cell line for biopharmaceutical companies in terms of manufacturing mass amounts of recombinant therapeutic proteins. This is due to CHO cells having various characteristics that are vital to the production of therapeutic proteins that sets it apart from other cell lines. One advantage to CHO cells is their increased ability to adapt. This adaptability, although beneficial, has its drawbacks, as it is owed to the inherent genetic instability of CHO cells. It has been hypothesized that the genetic instability of CHO cells comes from the cells inability to efficiently fix double strand breaks (DSBs) due to various SNPs in DSB related genes. In this study, four different CHO secreting alkaline phosphatase (SEAP) cell lines expressing an unmutated DSB related gene (Wrn, Wrn +Xrcc6, Rad1, or Rad1 + Xrcc6) was compared to CHO-SEAP WT. The cell line containing solely Wrn performed similarly to WT in terms of DSB repair, while the Rad1 cell line repaired DSBs more inefficiently. On the other hand, it was observed that cell lines expressing double DSB genes had opposite effects, as DSB repair worsened in Wrn + Xrcc6 and improved in Rad1+Xrcc6. This observation was further validated when comparing the SEAP titer of these cell line cultures over a period of about 8 weeks. The cell lines expressing Xrcc6 had lower SEAP titer per cell. However, once the cells were irradiated, these cell lines outperformed the cell lines containing only one DNA repair gene (Wrn or Rad1). This suggests the vital role that Xrcc6 plays in the CHO DSB repair system