Characterization of recombinant CHO cells in the course of gene amplification

Abstract

Chinese hamster ovary cell (CHO) production of humanized antibody was increased by amplification of cotransfected glutamine synthetase (GS) gene using additional rounds of selection with GS inhibitor methionine sulfoximine (MSX). The highest producer (HP) subclones were isolated from each MSX level and was characterized with respect to antibody production, cell growth rate, cell size and mitochondria content. HP subclones showed variable productivities, copy numbers and cellular characteristics that didn’t increase concomitantly to MSX increase. Generally, low production stability was observed during long-term culture. Presence of selection pressure didn’t prevent the drastic productivity drop observed within 10 generations during the long-term culture. Addition of glutamine enhanced the productivity and higher accumulative antibody yields were obtained in glutamine containing media, compared to the glutamine-free media. Significant decrease of copy numbers was observed, but the prod