High‐Level Recombinant Protein Production in CHO Cells Using an Adenoviral Vector and the Cumate Gene‐Switch

Fast and efficient production of recombinant proteins for structural and functional studies is a crucial issue for research and for industry. To this end, we have developed an efficient system to generate in less than 2 months, starting from the cDNA, pools of CHO cells stably expressing high-level of recombinant proteins. It is based on lentiviral vectors (LVs) for stable transduction coupled with the cumate gene-switch for inducible and efficient gene expression. Transcription is initiated upon binding of the cumate transactivator (cTA) or the reverse cTA (rcTA) to the CR5 promoter. Binding of cTA or rcTA is preventedorinduced byadditionofcumaterespectively. We first validated the CHO/LV production system with an LV carrying the secreted alkaline phosphatase (SEAP), whose expression was linked to the green fluorescent protein (GFP) through an internal ribosome entry site (IRES). CHO cells stably expressing the cTA (CHO-cTA) were transduced at various multiplicity of infection (MOI). Pools of cells were incubated at 37 and 308C during 10 days. Optimal SEAP production (65 mg/mL) was achieved at 308C with a MOI of 200. The pool stability was demonstrated for 48 days of culture by GFP expression analysis. The system was also evaluated using LV expressing three typical therapeutic proteins (a protein made up of the extracellular domain of CD200 fused to IgG Fc region (CD200Fc), a chimeric antibody (chB43), and erythropoietin (EPO)). CHO cells expressing rcTA (CHO-Cum2) were transduced with these LVs at a MOI of 200 and production was tested at 308C. After 13 days of culture, 235, 160, and 206 mg/mL of CD200Fc, chB43, and EPO were produced, respectively. The ON/OFF ratio of these pools was equal to 6 for CD200Fc, 16 for chB43, and 74 for EPO. In conclusion, thissystemshouldbe veryusefulto produce mgquantities of recombinant proteins in a timely manner in serum free suspension culture of CHO cells for preclinical studies. Biotechnol. Bioeng. 2010;106: 203-215.