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Takagi Y, Kikuchi T, Wada R, Omasa T. The enhancement of antibody concentration and achievement of high cell density CHO cell cultivation by adding nucleoside. Cytotechnology 2017; 69:511-521. [PMID: 28251404 DOI: 10.1007/s10616-017-0066-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 01/05/2017] [Indexed: 01/05/2023] Open
Abstract
Recently, with the dramatic increase in demand for therapeutic antibodies, Chinese hamster ovary (CHO) cell culture systems have made significant progress in recombinant antibody production. Over the past two decades, recombinant antibody productivity has been improved by more than 100-fold. Medium optimization has been identified as an important key approach for increasing product concentrations. In this study, we evaluated the effects of deoxyuridine addition to fed-batch cultures of antibody-expressing CHO cell lines. Furthermore, we investigated the effects of combined addition of deoxyuridine, thymidine, and deoxycytidine. Our results suggest that addition of these pyrimidine nucleosides can increase CHO cell growth, with no significant change in the specific production rate. As a result of the increased cell growth, the antibody concentration was elevated and we were able to achieve more than 9 g/L during 16 days of culture. Similar effects of nucleoside addition were observed in fed-batch cultures of a Fab fragment-expressing CHO cell line, and the final Fab fragment concentration was more than 4 g/L. This nucleoside addition strategy could be a powerful platform for efficient antibody production.
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Affiliation(s)
- Yasuhiro Takagi
- Institute of Bioscience and Bioindustry, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima, 770-8506, Japan
- Biotechnology Laboratories, Astellas Pharma Inc., 5-2-3 Tokodai, Tsukuba, Ibaraki, 300-2698, Japan
| | - Takuya Kikuchi
- Biotechnology Laboratories, Astellas Pharma Inc., 5-2-3 Tokodai, Tsukuba, Ibaraki, 300-2698, Japan
| | - Ryuta Wada
- Biotechnology Laboratories, Astellas Pharma Inc., 5-2-3 Tokodai, Tsukuba, Ibaraki, 300-2698, Japan
| | - Takeshi Omasa
- Institute of Bioscience and Bioindustry, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima, 770-8506, Japan.
- Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
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Weng T, Poth JM, Karmouty-Quintana H, Garcia-Morales LJ, Melicoff E, Luo F, Chen NY, Evans CM, Bunge RR, Bruckner BA, Loebe M, Volcik KA, Eltzschig HK, Blackburn MR. Hypoxia-induced deoxycytidine kinase contributes to epithelial proliferation in pulmonary fibrosis. Am J Respir Crit Care Med 2015; 190:1402-12. [PMID: 25358054 DOI: 10.1164/rccm.201404-0744oc] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
RATIONALE Idiopathic pulmonary fibrosis (IPF) is a deadly lung disease with few therapeutic options. Apoptosis of alveolar epithelial cells, followed by abnormal tissue repair characterized by hyperplastic epithelial cell formation, is a pathogenic process that contributes to the progression of pulmonary fibrosis. However, the signaling pathways responsible for increased proliferation of epithelial cells remain poorly understood. OBJECTIVES To investigate the role of deoxycytidine kinase (DCK), an important enzyme for the salvage of deoxynucleotides, in the progression of pulmonary fibrosis. METHODS DCK expression was examined in the lungs of patients with IPF and mice exposed to bleomycin. The regulation of DCK expression by hypoxia was studied in vitro and the importance of DCK in experimental pulmonary fibrosis was examined using a DCK inhibitor and alveolar epithelial cell-specific knockout mice. MEASUREMENTS AND MAIN RESULTS DCK was elevated in hyperplastic alveolar epithelial cells of patients with IPF and in mice exposed to bleomycin. Increased DCK was localized to cells associated with hypoxia, and hypoxia directly induced DCK in alveolar epithelial cells in vitro. Hypoxia-induced DCK expression was abolished by silencing hypoxia-inducible factor 1α and treatment of bleomycin-exposed mice with a DCK inhibitor attenuated pulmonary fibrosis in association with decreased epithelial cell proliferation. Furthermore, DCK expression, and proliferation of epithelial cells and pulmonary fibrosis was attenuated in mice with conditional deletion of hypoxia-inducible factor 1α in the alveolar epithelium. CONCLUSIONS Our findings suggest that the induction of DCK after hypoxia plays a role in the progression of pulmonary fibrosis by contributing to alveolar epithelial cell proliferation.
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Affiliation(s)
- Tingting Weng
- 1 Department of Biochemistry and Molecular Biology, The University of Texas-Houston Medical School, Houston, Texas
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Austin WR, Armijo AL, Campbell DO, Singh AS, Hsieh T, Nathanson D, Herschman HR, Phelps ME, Witte ON, Czernin J, Radu CG. Nucleoside salvage pathway kinases regulate hematopoiesis by linking nucleotide metabolism with replication stress. ACTA ACUST UNITED AC 2012; 209:2215-28. [PMID: 23148236 PMCID: PMC3501349 DOI: 10.1084/jem.20121061] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Nucleotide deficiency causes replication stress (RS) and DNA damage in dividing cells. How nucleotide metabolism is regulated in vivo to prevent these deleterious effects remains unknown. In this study, we investigate a functional link between nucleotide deficiency, RS, and the nucleoside salvage pathway (NSP) enzymes deoxycytidine kinase (dCK) and thymidine kinase (TK1). We show that inactivation of dCK in mice depletes deoxycytidine triphosphate (dCTP) pools and induces RS, early S-phase arrest, and DNA damage in erythroid, B lymphoid, and T lymphoid lineages. TK1(-/-) erythroid and B lymphoid lineages also experience nucleotide deficiency but, unlike their dCK(-/-) counterparts, they still sustain DNA replication. Intriguingly, dCTP pool depletion, RS, and hematopoietic defects induced by dCK inactivation are almost completely reversed in a newly generated dCK/TK1 double-knockout (DKO) mouse model. Using NSP-deficient DKO hematopoietic cells, we identify a previously unrecognized biological activity of endogenous thymidine as a strong inducer of RS in vivo through TK1-mediated dCTP pool depletion. We propose a model that explains how TK1 and dCK "tune" dCTP pools to both trigger and resolve RS in vivo. This new model may be exploited therapeutically to induce synthetic sickness/lethality in hematological malignancies, and possibly in other cancers.
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Affiliation(s)
- Wayne R Austin
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
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Requirement for deoxycytidine kinase in T and B lymphocyte development. Proc Natl Acad Sci U S A 2009; 107:5551-6. [PMID: 20080663 DOI: 10.1073/pnas.0913900107] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Deoxycytidine kinase (dCK) is a rate-limiting enzyme in deoxyribonucleoside salvage, a metabolic pathway that recycles products of DNA degradation. dCK phosphorylates and therefore activates nucleoside analog prodrugs frequently used in cancer, autoimmunity, and viral infections. In contrast to its well established therapeutic relevance, the biological function of dCK remains enigmatic. Highest levels of dCK expression are found in thymus and bone marrow, indicating a possible role in lymphopoiesis. To test this hypothesis we generated and analyzed dCK knockout (KO) mice. dCK inactivation selectively and profoundly affected T and B cell development. A 90-fold decrease in thymic cellularity was observed in the dCK KO mice relative to wild-type littermates. Lymphocyte numbers in the dCK KO mice were 5- to 13-fold below normal values. The severe impact of dCK inactivation on lymphopoiesis was unexpected given that nucleoside salvage has been thought to play a limited, "fine-tuning" role in regulating deoxyribonucleotide triphosphate pools produced by the de novo pathway. The dCK KO phenotype challenges this view and indicates that, in contrast to the great majority of other somatic cells, normal lymphocyte development critically requires the deoxyribonucleoside salvage pathway.
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Keszler G, Spasokoukotskaja T, Csapo Z, Talianidis I, Eriksson S, Staub M, Sasvari-Szekely M. Activation of deoxycytidine kinase in lymphocytes is calcium dependent and involves a conformational change detectable by native immunostaining. Biochem Pharmacol 2004; 67:947-55. [PMID: 15104248 DOI: 10.1016/j.bcp.2003.10.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Deoxycytidine kinase (dCK), the principal deoxynucleoside salvage enzyme, plays a seminal role in the bioactivation of a wide array of cytotoxic nucleoside analogues. Recently, activation of dCK has been considered as a protective cellular response to a number of DNA-damaging agents in lymphocytes. Regarding the molecular mechanism of the enzyme activation, a post-translational modification by protein phosphorylation has been suggested. Here we provide evidence that both the activation process and the maintenance of the activated state require free cytosolic calcium. BAPTA-AM, a cell-permeable calcium chelator selectively inhibited the activation of dCK in a time- and concentration-dependent manner while extracellular calcium depletion had no effect. On the other hand, elevation of cytoplasmic calcium levels by thapsigargin did not potentiate the enzyme, referring to the permissive function of calcium in the activation process. Denaturing Western blots of extracts from lymphocytes incubated with 2-chlorodeoxyadenosine, aphidicolin and/or BAPTA-AM clearly demonstrated that dCK protein levels were unchanged during these treatments. However, a striking correlation was found between enzyme activity and the intensity of dCK-specific signals in native Western blots. Extracts from CdA-treated cells were much better recognized by the antibody raised against the C-terminal peptide of dCK than the BAPTA-AM-treated samples. These results indicate that the calcium-dependent activation of dCK is accompanied by a conformational change that renders the C-terminal epitope more accessible to the antibody.
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Affiliation(s)
- Gergely Keszler
- Institute of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, P.O. Box 260, H-1444 Budapest, Hungary.
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Csapo Z, Keszler G, Safrany G, Spasokoukotskaja T, Talianidis I, Staub M, Sasvari-Szekely M. Activation of deoxycytidine kinase by gamma-irradiation and inactivation by hyperosmotic shock in human lymphocytes. Biochem Pharmacol 2003; 65:2031-9. [PMID: 12787883 DOI: 10.1016/s0006-2952(03)00182-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Deoxycytidine kinase (dCK) is a key enzyme in the intracellular metabolism of deoxynucleosides and their analogues, phosphorylating a wide range of drugs used in the chemotherapy of leukaemia and solid tumours. Previously, we found that activity of dCK can be enhanced by incubating primary cultures of lymphocytes with substrate analogues of the enzyme, as well as with various genotoxic agents. Here we present evidence that exposure of human lymphocytes to 0.5-2 Gy dosage of gamma-radiation as well as incubation of cells with calyculin A, a potent inhibitor of protein phosphatase 1 and 2A, both elevate dCK activity without changing the level of dCK protein. When cells were gamma-irradiated in the presence of calyculin A, a more pronounced activation of dCK was observed. In contrast, both basal and stimulated dCK activities were reduced by hyperosmotic treatment of the cells. DNA repair determined by the Comet assay and by thymidine incorporation was induced by irradiation. Complete repair of gamma-irradiated DNA was detected within 1 hr following the irradiation along with dCK activation, but the rate of repair was not accelerated by calyculin A. These data provide evidence for the activation of dCK upon DNA damage and repair that seems to be mediated by phosphorylation of the enzyme, suggesting the role of dCK in DNA repair processes.
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Affiliation(s)
- Zsolt Csapo
- Institute of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, P.O. Box 260, H-1444 Budapest, Hungary
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Van Den Neste E, Smal C, Cardoen S, Delacauw A, Frankard J, Ferrant A, Van den Berghe G, Bontemps F. Activation of deoxycytidine kinase by UV-C-irradiation in chronic lymphocytic leukemia B-lymphocytes. Biochem Pharmacol 2003; 65:573-80. [PMID: 12566084 DOI: 10.1016/s0006-2952(02)01559-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Deoxycytidine kinase (dCK), a key enzyme of the deoxynucleoside salvage pathway, might have a preponderant role in DNA synthesis in resting chronic lymphocytic leukemia B-lymphocytes. In these cells, two important enzymes in deoxynucleoside triphosphate production, ribonucleotide reductase and thymidine kinase (TK), both cell-cycle regulated, are indeed very weakly expressed. This study investigated the regulation of dCK activity in response to UV-C light, a condition which causes DNA lesions and DNA repair synthesis. We observed that activity of dCK in B-CLL cells was upregulated up to 3-fold, 30 min after irradiation with 30 J/m(2) UV-C, whereas TK activity was unchanged. Activation of dCK by UV-C light was caused neither by a change in concentration of a low molecular weight metabolite nor by an increase in the amount of dCK protein. Activation of dCK by UV-C was mimicked by H(2)O(2), markedly counteracted by N-acetylcysteine, a general antioxidant, and completely abolished by the growth factor receptor inhibitor suramin. Taken together, these results indicate that dCK activity is upregulated by UV-C light through a postranslational modification that may be initiated at the cell surface through oxidative mechanisms. Suramin also suppressed the increase in DNA repair synthesis elicited by UV-C irradiation, suggesting that upregulation of dCK activity could contribute to the normal completion of DNA repair synthesis elicited by UV light.
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Affiliation(s)
- Eric Van Den Neste
- Laboratory of Physiological Chemistry, Christian de Duve Institute of Cellular Pathology, Avenue Hippocrate 75, UCL-ICP 7539, B-1200 Brussels, Belgium.
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Spasokukotskaja T, Sasvári-Székely M, Taljanidisz J, Staub M. Compartmentation of dCTP pools disappears after hydroxyurea or araC treatment in lymphocytes. FEBS Lett 1992; 297:151-4. [PMID: 1551421 DOI: 10.1016/0014-5793(92)80348-k] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The calculated rate of DNA synthesis using [5-3H]TdR was about 4 times higher than in the case of [5-3H]CdR labeling, even after correction for the specific radioactivities of the intracellular pools. These data show a compartmentation of dCTP pools in lymphocytes. Hydroxyurea increased the specific activities of both dTTP and dCTP pools so that the calculated rate of DNA synthesis became equal. The same effect was found for araC treatment, but not for fluorodeoxyuridine. dCTP was supplied from CTP which is the lowest ribonucleotide pool in lymphocytes. Different functions of the two dCTP pools are proposed: one serving DNA replication; the other one supplies phospholipid precursors and DNA repair.
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Affiliation(s)
- T Spasokukotskaja
- 1st Institute of Biochemistry, Semmelweis University Medical School, Budapest, Hungary
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Spasokukotskaja T, Taljanidisz J, Sasvári-Székely M, Staub M. Deoxycytidine is salvaged not only into DNA but also into phospholipid precursors. III. dCOP-diacylglycerol formation in tonsillar lymphocytes. Biochem Biophys Res Commun 1991; 174:680-7. [PMID: 1993063 DOI: 10.1016/0006-291x(91)91471-n] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In addition to the water-soluble deoxyliponucleotides (Spasokukotskaja et al. (1988), Biochem. Biophys. Res. Commun. 155, 923), a lipid compound was shown to be labeled from external 3H-deoxycytidine (5-3H-CdR) in infant tonsillar lymphocytes. Chlorpromazine enhanced the labeling of this compound, identified by TLC as 3H-dCDP-diacylglycerol (3H-dCOP-DAG). The deoxynucleotide salvage pathway seems to be the main source for dCDP-DAG synthesis, as hydroxyurea increased its labeling from CdR. myo-Inositol induced the disappearance of 5-3H-dCOP-DAG, suggesting its utilization for phosphatidylinositol synthesis. 3H-Arabinosyl-Cytosine (araC) is also incorporated into the lipidic fraction at a rate comparable to its incorporation into DNA, supporting the effect of araC on membrane functions.
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Affiliation(s)
- T Spasokukotskaja
- 1st Institute of Biochemistry, Semmelweis University Medical School, Budapest, Hungary
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