High Expression of Human Monoclonal Antibodies in CHO Cells Selected Using a Cycloheximide Resistance Marker

Abstract

In our previous study, we developed a novel cycloheximide resistance (cyh ^R) marker for use in mammalian cells. In experiments using human monoclonal antibody genes, vectors containing this cyh ^R marker produced cycloheximide resistant CHO clones whose maximum expression levels were significantly higher than that of the neo ^R/G418 clones. The expression levels of cyh ^R clones were 3 to 4 times higher than those of neo ^R clones, in protein-free suspension culture. The maximum yield of antibody in cyh ^R clones reached over 700 mg/L in a typical fed-batch culture using a 3L-bioreactor. Cell growth studies showed no difference in doubling times between cyh ^R and neo ^R clones expressing antibodies and stability of expression in the absence of antibiotic was also demonstrated. The cyh ^R system thus provides a significantly more efficient method for selection of high-expressing CHO clones without the need for gene amplification, and in a substantially shorter time frame than methods currently in use.