title: Overexpression of cold-inducible RNA-binding protein increases interferon-gamma production in Chinese-hamster ovary cells.
abstract: Culturing recombinant CHO (Chinese-hamster ovary) cells at low temperatures (30-33 degrees C) increases specific recombinant protein productivity by 2-5-fold. However, even though the specific productivity is increased, cell growth is decreased in low-temperature culture such that the final recombinant protein titre remains unchanged or is even diminished, owing to the lower cell density. Exposing mammalian cells to low temperatures results in a change in the expression of many 'cold-stress' genes. CIRP (cold-inducible RNA-binding protein) is a cold-stress protein that is highly expressed at 32 degrees C, but not at 37 degrees C. In the present study we demonstrated that overexpression of CIRP at 37 degrees C can increase the recombinant-protein titre in CHO cells. Stable overexpression of CIRP at 37 degrees C improved the final titre of CHO IFN-gamma, a recombinant CHO cell line producing human IFN-gamma (interferon-gamma), by 25% in adherent culture and up to 40% in suspension culture. Real-time PCR analysis showed that the increase in the recombinant IFN-gamma titre could be attributed to increased recombinant IFN-gamma mRNA levels, while growth data showed that CIRP overexpression did not result in growth arrest in CHO IFN-gamma cells. Glycan analysis showed that the increase in IFN-gamma titre as a result of CIRP overexpression did not affect the site occupancy, glycan structures or sialic acid content of IFN-gamma. Using this strategy, the final IFN-gamma titre was increased by 40% compared with current temperature-based strategies. Furthermore, there is no decrease in cell growth or recombinant-protein glycosylation quality, as previously observed in low-temperature culture.
authors.affiliation: Department of Molecular Engineering of Biological and Chemical Systems, Singapore-MIT (Massachusetts Institute of Technology) Alliance, National University of Singapore, Singapore 117576.
authors.forename: Hong Kiat
authors.initials: HK
authors.lastname: Tan
authors.forename: May May
authors.initials: MM
authors.lastname: Lee
authors.forename: Miranda G S
authors.initials: MG
authors.lastname: Yap
authors.forename: Daniel I C
authors.initials: DI
authors.lastname: Wang
mesh_terms: D000818:Animals; D016466:CHO Cells; D003080:Cold Temperature; D006224:Cricetinae; D003412:Cricetulus; D024861:Genetic Enhancement / Q000379:methods*; D006801:Humans; D007371:Interferon-gamma / Q000235:genetics / Q000378:metabolism*; D015202:Protein Engineering / Q000379:methods*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis*; D015854:Up-Regulation
chemical_list: C491390:CIRBP protein, human; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D007371:Interferon-gamma