Availability of oncogene activated production system for mass production of light chain of human antibody in CHO cells

We previously established a ras-oncogene amplified Chinese hamster ovary (C HO) cell line, named ras clone I, as an universal host cell line for oncoge ne activated production (OAP) system to mass-produce recombinant protein by activation of the cytomegalovirus immediate early (CMV) promoter with ras protein. The lambda light chain (C5 lambda) of human monoclonal antibody HB 4C5 is expected to be potentially useful for lung cancer targeting. We gene rated a C5 lambda hyper-producing cell line by transfecting ras clone I wit h the C5 lambda gene expression plasmid regulated by the CMV promoter, of w hich productivity was 5.3 times greater than the hyper productive CHO cell line generated by using conventional CHO cells. Introduction of the adenovi rus E1A gene into the hyper-producing cell line derived from ras clone I re sulted in further 9.5 times enhancement of the productivity, suggesting the synergistic effect of E1A and ras oncogenes on the recombinant protein pro duction driven by the CMV promoter. In addition, intracellular accumulation of C5 lambda and upregulation of BiP was found in hyper-producing cell lin es which were introduced E1A and ras oncogene. This result suggests that ex cessive intracellular accumulation of C5 lambda protein, which might be cau sed by that the amount of produced C5 lambda in ER is beyond the ability of CHO cells to secrete, might signal the BiP promoter. Our data imply that r as clone I is available as a general host cell for establishing the recombi nant protein hyper-producing CHO cells by the OAP system, and suggest that further mass production of recombinant proteins in the OAP system can be po ssible by clarifying the accurate role of upregulated BiP protein.