Oncogene Activated Production System to Enhance Cellular Recombinant Protein Productivity

Abstract

In order to enhance cellular recombinant protein productivity by using the specific promoter activation with oncogenes, the ras oncogene was cotransfected with the dihydrofolate reductase (dfhr) gene into a recombinant BHK-21 cell line, BCI-8, producing human interleukin-6 (IL-6) under control of the cytomegalo virus immediate early promoter (CMV promoter). A single step gene amplification of ras using 50 nM methotrexate (MTX) resulted in the rapid establishment of a stable hIL-6 hyper-producing clone exhibiting about 35 times higher productivity compared to BCI-8 cells. Other oncogenes such as myc,myb, fos, and jun and adenovirus E1A did not enhance cellular productivity. To rapidly establish hIL-6 hyper-producing cell lines, we created host cell lines from BHK-21 cells which were ‘primed’ with amplified ras oncogene expression units prior to the introduction of a producing gene. The primed BHK cell lines were demonstrated to produce many stable highly hIL-6 productive cells achieving about 15 times higher productivity as compared to original BHK cells upon introduction of the producing gene. Furthermore, the ElA gene elevated the hIL-6 production level in the ras-amplified hIL-6 hyper-producing cells by about 10 times, suggesting a synergistic action between the E1A and ras oncogenes.