A novel autoregulated proliferation-controlled production process using recombinant CHO cells

Controlled proliferation bioprocesses have shown great enhancement of heterologous protein production. This novel technology has been implemented here using a multicistronic expression unit encoding the product gene and a cytostatic cell-cycle-arresting gene (p27) under control of a single tetracycline-repressible (tet(off)) promoter. The strict genetic linkage of both genes allows the dissection of the production process into a nonproductive growth phase (dicistronic expression unit repressed) followed by a proliferation-inhibited production phase (dicistronic expression unit induced) when the cells have reached an optimal cell density. Based on rapid degradation of the external repressible agents tetracycline (tet) and doxycycline (dox) in the cell culture medium, we developed a self-regulated process for transition from the growth phase to the production phase in a fashion that is dependent only on the starting cell population and the initial concentration of the tetracyclines. With this process, no change in medium is required to accomplish the transition from growth to production phase. The two-phase bioprocess achieved here by tet switch-controlled proliferation is reliable and allows a growth-arrested production phase of at least 7 days, during which cells remain in a well-defined, highly viable physiological state and show enhanced heterologous protein production. This Tet(SWITCH) process is readily adaptable to a variety of industrial processes designed for production of difficult-to-express protein pharmaceuticals.