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Restoration of DNA repair mitigates genome instability and increases productivity of Chinese hamster ovary cells.

ABSTRACT: Chinese hamster ovary (CHO) cells are the primary host for manufacturing of therapeutic proteins. However, productivity loss is a major problem and is associated with genome instability, as chromosomal aberrations reduce transgene copy number and decrease protein expression. We analyzed whole-genome sequencing data from 11 CHO cell lines and found deleterious single-nucleotide variants in DNA repair genes. Comparison with primary Chinese hamster cells confirmed DNA repair to be compromised in CHO. Correction of key DNA repair genes by single-nucleotide variant reversal or expression of intact complementary DNAs successfully improved DNA repair and mitigated karyotypic instability. Moreover, overexpression of intact copies of LIG4 and XRCC6 in a CHO cell line expressing secreted alkaline phosphatase mitigated transgene copy loss and improved protein titer retention. These results show that correction of DNA repair genes yields improvements in genome stability in CHO, and provide new opportunities for cell line development for sustainable protein expression.

SUBMITTER: Spahn PN

PROVIDER: S-EPMC8821244 | biostudies-literature | 2022 Mar

REPOSITORIES: biostudies-literature

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Restoration of DNA repair mitigates genome instability and increases productivity of Chinese hamster ovary cells.

Spahn Philipp N PN Zhang Xiaolin X Hu Qing Q Lu Huiming H Hamaker Nathaniel K NK Hefzi Hooman H Li Shangzhong S Kuo Chih-Chung CC Huang Yingxiang Y Lee Jamie C JC Davis Anthony J AJ Ly Peter P Lee Kelvin H KH Lewis Nathan E NE Lewis Nathan E NE

Biotechnology and bioengineering 20220105 3

Chinese hamster ovary (CHO) cells are the primary host for manufacturing of therapeutic proteins. However, productivity loss is a major problem and is associated with genome instability, as chromosomal aberrations reduce transgene copy number and decrease protein expression. We analyzed whole-genome sequencing data from 11 CHO cell lines and found deleterious single-nucleotide variants in DNA repair genes. Comparison with primary Chinese hamster cells confirmed DNA repair to be compromised in CH ...[more]

PMID: 34953085

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Project description:Biopharmaceuticals are medical compounds derived from biological sources and are often manufactured by living cells, primarily Chinese hamster ovary (CHO) cells. CHO cells display variation among cell clones, leading to growth and productivity differences that influence the product's quantity and quality. The biological and environmental factors behind these differences are not fully understood. To identify metabolites with a consistent relationship to productivity or cell death over time, we analyzed the extracellular metabolome of 11 CHO clones with different growth and productivity characteristics over 14 days. However, in bioreactor processes, metabolic profiles and process variables are both strongly time-dependent, confounding the metabolite-process variable relationship. To address this, we customized an existing hierarchical approach for handling time dependency to highlight metabolites with a consistent correlation to a process variable over a selected timeframe. We benchmarked this new method against conventional orthogonal partial least squares (OPLS) models. Our hierarchical method highlighted several metabolites consistently related to productivity or cell death that the conventional method missed. These metabolites were biologically relevant; most were known already, but some that had not been reported in CHO literature before, such as 3-methoxytyrosine and succinyladenosine, had ties to cell death in studies with other cell types. The metabolites showed an inverse relationship with the response variables: those positively correlated with productivity were typically negatively correlated with the death rate, or vice versa. For both productivity and cell death, the citrate cycle and adjacent pathways (pyruvate, glyoxylate, pantothenate) were among the most important. In summary, we have proposed a new method to analyze time-dependent omics data in bioprocess production. This approach allowed us to identify metabolites tied to cell death and productivity that were not detected with traditional models.

Project description:Introduction: The growing demand for recombinant proteins in medicine has prompted biopharmaceutical companies to seek ways to maximize the manufacturing process. Despite its known negative impact on cell growth, temperature shift (TS) has emerged as a cost-effective strategy to enhance protein quantity and quality in Chinese Hamster Ovary cells (CHO). As cells adapt their growth and protein synthesis rate to the environment through influencing mTOR complex 1 (mTORC1), here we evaluated the potential of mTORC1 signaling engineering to improve the production of granulocyte-macrophage colony-stimulating factor (GM-CSF) protein in stable CHO cells at low temperature. Methods: First, the expression of genes that negatively control mTORC1 functions in response to environmental fluctuations, including TSC1, AMPK, MAPKAPK5, and MARK4 genes, was assessed via real-time qPCR in CHO-K1 after a temperature shift from 37°C to 30°C. Then, plasmids harboring the shRNAs targeting these genes were constructed into the PB513B-1 plasmid with expression driven by either the constitutive CMV promoter or the cold-inducible HSP90 promoter. Finally, the impact of transient gene downregulation was evaluated on GM-CSF and mTOR proteins productivity in GM-CSF-producing CHO-K1 cells using ELISA and Western-blot assays, respectively. The growth rate of the transfected cells at the two temperatures was evaluated using flow cytometry. Results: Hypothermic conditions promote the upregulation of mTORC1 inhibitor genes, especially TSC1 and MAPKAPK5, while downregulating S6K, a key effector of the mTORC1 signaling pathway, in CHO-K1 cells. Transcription and protein levels of mTOR increased upon transfection, "pB513-b CMV-P/4shRNAs/GFP" plasmid, "pB513-bHSP90-P/4sh-RNAs/GFP" and pB513B-1 plasmid as mock group in GM-CSF-producing CHO-K1 cells (approximately 60%), along with a high transcript level of S6K. Cell growth-related characteristics were improved, albeit with distinct effects at different temperatures. Notably, these changes were more efficient at 30°C when utilizing the HSP90 promoter, resulting in a three-fold increase in GM-CSF production after 3 days. Conclusion: This study highlights the importance of temperature regulation and mTORC1 modulation in CHO cellular processes, particularly in recombinant protein production. Understanding these mechanisms paves the way for developing innovative strategies to enhance cell growth, protein synthesis, and overall bioprocess performance, particularly in manufacturing human therapeutic proteins.

Dataset Information

Restoration of DNA repair mitigates genome instability and increases productivity of Chinese hamster ovary cells.

Publications

Restoration of DNA repair mitigates genome instability and increases productivity of Chinese hamster ovary cells.

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