Effects of ubiquitous chromatin opening element (UCOE) on recombinant anti-TNFα antibody production and expression stability in CHO-DG44 cells

Chinh Chung Doan; Thanh Long Le; Nguyen Quynh Chi Ho; Nghia Son Hoang

doi:10.1007/s10616-021-00503-1

Effects of ubiquitous chromatin opening element (UCOE) on recombinant anti-TNFα antibody production and expression stability in CHO-DG44 cells

Cytotechnology. 2022 Feb;74(1):31-49. doi: 10.1007/s10616-021-00503-1. Epub 2021 Oct 23.

Authors

Chinh Chung Doan^{1

2}, Thanh Long Le^{1

2}, Nguyen Quynh Chi Ho¹, Nghia Son Hoang^{1

2}

Affiliations

¹ Department of Animal Biotechnology, Institute of Tropical Biology, Vietnam Academy of Science and Technology, 9/621 Xa lo Ha Noi Street, Linh Trung Ward, Thu Duc City, Ho Chi Minh City, Vietnam.
² Faculty of Biotechnology, Graduate University of Science and Technology, Vietnam Academy of Science and Technology, Cau Giay District, 18 Hoang Quoc Viet Street, Ha Noi City, Vietnam.

Abstract

To date, the production of antibodies (mAbs) usually faces the risks of transgene expression reduction and instability, especially after long-time culture. The inclusion of ubiquitous chromatin opening element (UCOE) into expression vectors was reported to enhance protein production and maintain transgene expression stability in CHO cell lines. Thus, we investigate the effects of UCOE on recombinant monoclonal anti-TNFα antibody (mAbTNFα) production and expression stability in CHO-DG44 cells. In our study, non-UCOE and UCOE-based vectors encoding mAbTNFα were constructed and introduced into the CHO-DG44 cells. Cell pools and single-cell clones were obtained by selecting transfected cells with G418, amplifying them by treatment with methotrexate (MTX), and isolating them by limiting dilution. The effects of UCOE on mAb production and stable transgene expression in transfected cells were analyzed via the correlation between mAb yields and mRNA expression level variations, and gene copy number changes. The UCOE pool exhibited higher mAb yield compared to non-UCOE pool. The UCOE was associated with higher transgene transcriptional activity, leading to improvement of mAb production after MTX-mediated gene amplification. The incorporation of UCOE generated cells allowed isolation of greater numbers of positive clones with higher expression. Despite the slightly decreased mAb yield, UCOE clones still retain stable long-term expression in the absence of selective pressure, which was explained by the loss of transgene copies rather than due to the decline of transcriptional activity. In addition, the purified mAb had primary chemical and biological characteristics similar to those of adalimumab. The results showed that the incorporation of UCOE within vectors provides significant advantages in the generation of high-producing clones, enhancement of mAb production, and improvement of gene expression stability.

Keywords: CHO-DG44 cells; Gen expression stability; UCOE; mAb production; mAbTNFα.