text: Traditionally, Chinese hamster ovary (CHO) cells are associated with the establishment of stable cell lines for biologics. Recently, however, attempts to engineer CHO cells for transient protein production have garnered recognition. CHO cells were among the earliest established cell lines for in vitro cultivation, and their potential as a host for production and manufacturing of biological products remains popular. CHO cells are preferable for transient expression due to their easy industrial scale-up, versatility for the production of diverse biomolecules, and low risk of infection of human viruses, among other advantages. Three primary expression systems have been established:
  # EBNA-1-engineered CHO cell line
  # CHO EBNA LT cell line, which is carried apart from the EBNA-1 gene and the mouse polyomavirus large T antigen
  # EpiCHO system, which consists of a CHO cell line transfected with the polyomavirus large T antigen gene and a DNA expression vector encoding polyomavirus origin (PyOri) for autonomous replication and EBV EBNA-1 and OriP for plasmid retention.