Secretion analysis of intracellular “difficult-to-express” immunoglobulin G (IgG) in Chinese hamster ovary (CHO) cells
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The Chinese hamster ovary (CHO) cell line is the most widely used host cell for therapeutic antibody production. Although its productivity has been improved by various strategies to satisfy the growing global demand, some difficult-to-express (DTE) antibodies remain at low secretion levels. To improve the production of various therapeutic antibodies, it is necessary to determine possible rate-limiting steps in DTE antibody secretion in comparison with other high IgG producers. Here, we analyzed the protein secretion process in CHO cells producing the DTE immunoglobulin G (IgG) infliximab. The results from chase assays using a translation inhibitor revealed that infliximab secretion could be nearly completed within 2 h, at which time the cells still retained about 40% of heavy chains and 65% of light chains. Using fluorescent microscopy, we observed that these IgG chains remained in the endoplasmic reticulum and Golgi apparatus. The cells inefficiently form fully assembled heterodimer IgG by making LC aggregates, which may be the most serious bottleneck in the production of DTE infliximab compared with other IgG high producers. Our study could contribute to establish the common strategy for constructing DTE high-producer cells on the basis of rate-limiting step analysis.
KeywordsAnimal cell culture Chinese hamster ovary cell Therapeutic antibody production Difficult-to-express IgG Protein secretion
This work was partially financially supported by the Japan Agency for Medical Research and Development (AMED; JP17ae0101003, JP18ae0101056, JP18ae0101057) and by Grants-in-aid for Scientific Research from the Japan Society for the Promotion of Science (JSPS; JP26630433, JP26249125, JP17H06157, and JP17J00927). We thank Katie Oakley, Ph.D., from Edanz Group for editing a draft of this manuscript.
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The authors declare that they have no conflict of interest.
Research involving human participants and/or animals
This manuscript does not contain information about the research involving human participants and/or animals
Informed consent is not necessary because we do not report a study involving human participants and/or animals.
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