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Chinese hamster ovary cell

May 01, 2024

Chinese hamster ovary (CHO) cells are a family of immortalized cell lines[1] derived from epithelial cells of the ovary of the Chinese hamster, often used in biological and medical research and commercially in the production of recombinant therapeutic proteins.[1][2] They have found wide use in studies of genetics, toxicity screening, nutrition and gene expression, and particularly since the 1980s to express recombinant proteins. CHO cells are the most commonly used mammalian hosts for industrial production of recombinant protein therapeutics.[2]

CHO cells adhered to a surface, seen under phase-contrast microscopy

History edit

Chinese hamsters had been used in research since 1919, where they were used in place of mice for typing pneumococci. They were subsequently found to be excellent vectors for transmission of kala-azar (visceral leishmaniasis), facilitating Leishmania research.[3][4]

In 1948, the Chinese hamster was first used in the United States for breeding in research laboratories. In 1957, Theodore T. Puck obtained a female Chinese hamster from Dr. George Yerganian's laboratory at the Boston Cancer Research Foundation and used it to derive the original Chinese hamster ovary (CHO) cell line. Since then, CHO cells have been a cell line of choice because of their rapid growth in suspension culture and high protein production.[3][5]

The thrombolytic medication against myocardial infarction alteplase (Activase) was approved by the US Food and Drug Administration in 1987. It was the first commercially available recombinant protein produced from CHO cells.[3][6] CHO cells continue to be the most widely used manufacturing approach for recombinant protein therapeutics and prophylactic agents. [7][8] In 2018, 10 of the 15 highest selling drugs were made in CHO cells.[citation needed]

Properties edit

All CHO cell lines are deficient in proline synthesis.[9] Also, CHO cells do not express the epidermal growth factor receptor (EGFR), which makes them ideal in the investigation of various EGFR mutations.[10]

Furthermore, Chinese hamster ovary cells are able to produce proteins with complex glycosylations, post-translational modifications (PTMs) similar to those produced in humans. They are easily growable in large-scale cultures and have great viability, which is why they are ideal for GMP protein production. Also, CHO cells are tolerant to variations in parameters, be it oxygen levels, pH-value, temperature or cell density.[11]

Having a very low chromosome number (2n=22) for a mammal, the Chinese hamster is also a good model for radiation cytogenetics and tissue culture.[12]

Variants edit

Since the original CHO cell line was described in 1956, many variants of the cell line have been developed for various purposes.[9][additional citation(s) needed] In 1957, CHO-K1 was generated from a single clone of CHO cells.[13] According to an industry source, however, scientist Theodore Puck first isolated CHO-K1 in 1968.[1] Puck and colleagues reported starting a cell line of Chinese hamster ovarian origin in 1957.[14][15] Variants of K1 include the deposits in ATCC, ECACC, and a version adapted for growth in protein-free medium.[13]

CHO-K1 was mutagenized in the 1970s with ethyl methanesulfonate to generate a cell line lacking dihydrofolate reductase (DHFR) activity, referred to as CHO-DXB11 (also referred to as CHO-DUKX).[16] However, these cells, when mutagenized, could revert to DHFR activity, making their utility for research somewhat limited.[16] Subsequently in 1983, CHO cells were mutagenized with gamma radiation to yield a cell line in which both alleles of the DHFR locus were completely eliminated, termed CHO-DG44.[17] These DHFR-deficient strains require glycine, hypoxanthine, and thymidine for growth.[17] Cell lines with mutated DHFR are useful for genetic manipulation as cells transfected with a gene of interest along with a functional copy of the DHFR gene can easily be screened for in thymidine-lacking media. Due to this, CHO cells lacking DHFR are the most widely used CHO cells for industrial protein production.

More recently, other selection systems have become popular and with vector systems that can more efficiently target active chromatin in CHO cells, antibiotic selection (puromycin) can be used as well to generate recombinant cells expressing proteins at high level. This sort of system requires no special mutation, so that non-DHFR-deficient host cell culture have been found to produce excellent levels of proteins.

Since CHO cells have a very high propensity of genetic instability (like all immortalised cells) one should not assume that the names applied indicate their usefulness for manufacturing purposes. For example, the three K1 offspring cultures available in 2013 each have significant accumulated mutations compared to each other.[13] Most, if not all industrially used CHO cell lines are now cultivated in animal component free media or in chemically defined media, and are used in large scale bioreactors under suspension culture.[9][13] The complex genetics of CHO cells and the issues concerning clonal derivation of cell population was extensively discussed.[18][19]

Genetic manipulation edit

Much of the genetic manipulation done in CHO cells is done in cells lacking DHFR enzyme. This genetic selection scheme remains one of the standard methods to establish transfected CHO cell lines for the production of recombinant therapeutic proteins. The process begins with the molecular cloning of the gene of interest and the DHFR gene into a single mammalian expression system. The plasmid DNA carrying the two genes is then transfected into cells, and the cells are grown under selective conditions in a thymidine-lacking medium. Surviving cells will have the exogenous DHFR gene along with the gene of interest integrated in its genome.[20][21] The growth rate and the level of recombinant protein production of each cell line varies widely. To obtain a few stably transfected cell lines with the desired phenotypic characteristics, evaluating several hundred candidate cell lines may be necessary.

The CHO and CHO-K1 cell lines can be obtained from a number of biological resource centres such as the European Collection of Cell Cultures, which is part of the Health Protection Agency Culture Collections. These organizations also maintain data, such as growth curves, timelapse videos of growth, images, and subculture routine information.[22]

Industrial use edit

CHO cells are the most common mammalian cell line used for mass production of therapeutic proteins such as monoclonal antibodies, used in 70% of therapeutic mAbs.[2] They can produce recombinant protein on the scale of 3–10 grams per liter of culture.[9] Products of CHO cells are suitable for human applications, as these mammalian cells perform human-like post-translational modifications to recombinant proteins, which is key to the functioning of several proteins.[23]

See also edit

 
Wikimedia Commons has media related to CHO cells.

References edit

  1. ^ a b c Eberle, Christian (3 May 2022). "CHO cells – 7 facts about the cell line derived from the ovary of the Chinese hamster". evitria. Retrieved 30 January 2024.
  2. ^ a b c Wurm FM (2004). "Production of recombinant protein therapeutics in cultivated mammalian cells". Nature Biotechnology. 22 (11): 1393–1398. doi:10.1038/nbt1026. PMID 15529164. S2CID 20428452.
  3. ^ a b c "Vital Tools A Brief History of CHO Cells" (PDF). LSF Magazine. Winter 2015. pp. 38–47. Retrieved 5 April 2023.
  4. ^ Young C, Smyly H, Brown C (March 1924). "Experimental kala-azar in a hamster". Experimental Biology and Medicine. 21 (6): 357–359. doi:10.3181/00379727-21-182. ISSN 1535-3702.
  5. ^ Fanelli, Alex (2016). "CHO Cells". Retrieved 28 November 2017.
  6. ^ Du C; Webb C (2011). "Cellular Systems". Comprehensive Biotechnology. Elsevier. pp. 11–23. doi:10.1016/b978-0-08-088504-9.00080-5. ISBN 9780080885049.
  7. ^ Tihanyi B, Nyitray L (December 2020). "Recent advances in CHO cell line development for recombinant protein production". Drug Discovery Today. 38: 25–34. doi:10.1016/j.ddtec.2021.02.003. hdl:10831/82853. PMID 34895638. However, 70% of biologics, and almost all mAbs, are produced in Chinese hamster ovary (CHO) cells, as the most commonly used and preferred hosts for biopharmaceutical protein production.
  8. ^ Liang K, Luo H, Li Q (2023). "Enhancing and stabilizing monoclonal antibody production by Chinese hamster ovary (CHO) cells with optimized perfusion culture strategies". Frontiers in Bioengineering and Biotechnology. 11: 1112349. doi:10.3389/fbioe.2023.1112349. PMC 9895834. PMID 36741761. Since 2016, about 70% of all rBPs and mAbs were produced from Chinese hamster ovary (CHO) cell lines
  9. ^ a b c d Wurm FM; Hacker D (2011). "First CHO genome". Nature Biotechnology. 29 (8): 718–20. doi:10.1038/nbt.1943. PMID 21822249. S2CID 8422581.
  10. ^ Ahsan, A.; S. M. Hiniker; M. A. Davis; T. S. Lawrence; M. K. Nyati (2009). "Role of Cell Cycle in Epidermal Growth Factor Receptor Inhibitor-Mediated Radiosensitization". Cancer Research. 69 (12): 5108–5114. doi:10.1158/0008-5472.CAN-09-0466. PMC 2697971. PMID 19509222.
  11. ^ "CHO cells - 7 facts about the cell line derived from the ovary of the Chinese hamster". evitria AG. 3 May 2022.
  12. ^ Tjio J. H.; Puck T. T. (1958). "Genetics of somatic mammalian cells. II. chromosomal constitution of cells in tissue culture". J. Exp. Med. 108 (2): 259–271. doi:10.1084/jem.108.2.259. PMC 2136870. PMID 13563760.
  13. ^ a b c d Lewis NE; Liu X; Li Y; Nagarajan H; Yerganian G; O'Brien E; et al. (2013). "Genomic landscapes of Chinese hamster ovary cell lines as revealed by the Cricetulus griseus draft genome". Nature Biotechnology. 31 (8): 759–765. doi:10.1038/nbt.2624. PMID 23873082.
  14. ^ Puck TT, Cieciura SJ, Robinson A (1958). "Genetics of Somatic Mammalian Cells: III. Long-Term Cultivation of Euploid Cells from Human and Animal Subjects". Journal of Experimental Biology. 108 (6): 945–956. doi:10.1084/jem.108.6.945. PMC 2136918. PMID 13598821.
  15. ^ Ham RG (1965). "CLONAL GROWTH OF MAMMALIAN CELLS IN A CHEMICALLY DEFINED, SYNTHETIC MEDIUM". Proceedings of the Natural Academy of Sciences. 53 (2): 288–293. doi:10.1073/pnas.53.2.288. PMC 219509. PMID 14294058.
  16. ^ a b Urlaub G; Chasin LA (July 1980). "Isolation of Chinese hamster cell mutants deficient in dihydrofolate reductase activity". Proceedings of the National Academy of Sciences of the United States of America. 77 (7): 4216–4220. Bibcode:1980PNAS...77.4216U. doi:10.1073/pnas.77.7.4216. PMC 349802. PMID 6933469.
  17. ^ a b Urlaub G; Kas E; Carothers AD; Chasin LA (June 1983). "Deletion of the diploid dihydrofolate reductase locus from cultured mammalian cells". Cell. 33 (2): 405–412. doi:10.1016/0092-8674(83)90422-1. PMID 6305508.
  18. ^ Wurm, Florian; Wurm, Maria (2017). "Cloning of CHO cells, productivity and genetic stability – a discussion". Processes. 5 (4): 20. doi:10.3390/pr5020020.
  19. ^ Reinhart, D; Damjanovic, L; Kaisermayer, C; Sommeregger, W; Gili, A; Gasselhuber, B; Castan, A; Mayrhofer, P; Grünwald-Gruber, C; Kunert, R (March 2019). "Bioprocessing of Recombinant CHO-K1, CHO-DG44, and CHO-S: CHO Expression Hosts Favor Either mAb Production or Biomass Synthesis". Biotechnology Journal. 14 (3): e1700686. doi:10.1002/biot.201700686. PMID 29701329. S2CID 13844297.
  20. ^ Lee F; Mulligan R; Berg P; Ringold G (19 November 1981). "Glucocorticoids regulate expression of dihydrofolate reductase cDNA in mouse mammary tumour virus chimaeric plasmids". Nature. 294 (5838): 228–232. Bibcode:1981Natur.294..228L. doi:10.1038/294228a0. PMID 6272123. S2CID 2501119.
  21. ^ Kaufman RJ; Sharp PA (25 August 1982). "Amplification and expression of sequences cotransfected with a modular dihydrofolate reductase complementary DNA gene". Journal of Molecular Biology. 159 (4): 601–621. doi:10.1016/0022-2836(82)90103-6. PMID 6292436.
  22. ^ "General Cell Collection: CHO-K1". Hpacultures.org.uk. 2000-01-01. Retrieved 2013-05-21.
  23. ^ Tingfeng, Lai; et al. (2013). "Advances in Mammalian Cell Line Development Technologies for Recombinant Protein Production". Pharmaceuticals. 6 (5): 579–603. doi:10.3390/ph6050579. PMC 3817724. PMID 24276168.

External links edit

  • Chinese Hamster Genome Database
  • Puck TT, Cieciura SJ, Robinson A (December 1958). "Genetics of somatic mammalian cells. III. Long-term cultivation of euploid cells from human and animal subjects". J. Exp. Med. 108 (6): 945–56. doi:10.1084/jem.108.6.945. PMC 2136918. PMID 13598821.
  • Cellosaurus entry for CHO
  • Cellosaurus entry for CHO-K1
  • Cellosaurus entry for CHO-DG44
  • Cellosaurus entry for CHO-DXB11

May 01, 2024
chinese, hamster, ovary, cell, chinese, hamster, ovary, cells, family, immortalized, cell, lines, derived, from, epithelial, cells, ovary, chinese, hamster, often, used, biological, medical, research, commercially, production, recombinant, therapeutic, protein. Chinese hamster ovary CHO cells are a family of immortalized cell lines 1 derived from epithelial cells of the ovary of the Chinese hamster often used in biological and medical research and commercially in the production of recombinant therapeutic proteins 1 2 They have found wide use in studies of genetics toxicity screening nutrition and gene expression and particularly since the 1980s to express recombinant proteins CHO cells are the most commonly used mammalian hosts for industrial production of recombinant protein therapeutics 2 CHO cells adhered to a surface seen under phase contrast microscopy Contents 1 History 2 Properties 3 Variants 4 Genetic manipulation 5 Industrial use 6 See also 7 References 8 External linksHistory editChinese hamsters had been used in research since 1919 where they were used in place of mice for typing pneumococci They were subsequently found to be excellent vectors for transmission of kala azar visceral leishmaniasis facilitating Leishmania research 3 4 In 1948 the Chinese hamster was first used in the United States for breeding in research laboratories In 1957 Theodore T Puck obtained a female Chinese hamster from Dr George Yerganian s laboratory at the Boston Cancer Research Foundation and used it to derive the original Chinese hamster ovary CHO cell line Since then CHO cells have been a cell line of choice because of their rapid growth in suspension culture and high protein production 3 5 The thrombolytic medication against myocardial infarction alteplase Activase was approved by the US Food and Drug Administration in 1987 It was the first commercially available recombinant protein produced from CHO cells 3 6 CHO cells continue to be the most widely used manufacturing approach for recombinant protein therapeutics and prophylactic agents 7 8 In 2018 10 of the 15 highest selling drugs were made in CHO cells citation needed Properties editAll CHO cell lines are deficient in proline synthesis 9 Also CHO cells do not express the epidermal growth factor receptor EGFR which makes them ideal in the investigation of various EGFR mutations 10 Furthermore Chinese hamster ovary cells are able to produce proteins with complex glycosylations post translational modifications PTMs similar to those produced in humans They are easily growable in large scale cultures and have great viability which is why they are ideal for GMP protein production Also CHO cells are tolerant to variations in parameters be it oxygen levels pH value temperature or cell density 11 Having a very low chromosome number 2n 22 for a mammal the Chinese hamster is also a good model for radiation cytogenetics and tissue culture 12 Variants editSince the original CHO cell line was described in 1956 many variants of the cell line have been developed for various purposes 9 additional citation s needed In 1957 CHO K1 was generated from a single clone of CHO cells 13 According to an industry source however scientist Theodore Puck first isolated CHO K1 in 1968 1 Puck and colleagues reported starting a cell line of Chinese hamster ovarian origin in 1957 14 15 Variants of K1 include the deposits in ATCC ECACC and a version adapted for growth in protein free medium 13 CHO K1 was mutagenized in the 1970s with ethyl methanesulfonate to generate a cell line lacking dihydrofolate reductase DHFR activity referred to as CHO DXB11 also referred to as CHO DUKX 16 However these cells when mutagenized could revert to DHFR activity making their utility for research somewhat limited 16 Subsequently in 1983 CHO cells were mutagenized with gamma radiation to yield a cell line in which both alleles of the DHFR locus were completely eliminated termed CHO DG44 17 These DHFR deficient strains require glycine hypoxanthine and thymidine for growth 17 Cell lines with mutated DHFR are useful for genetic manipulation as cells transfected with a gene of interest along with a functional copy of the DHFR gene can easily be screened for in thymidine lacking media Due to this CHO cells lacking DHFR are the most widely used CHO cells for industrial protein production More recently other selection systems have become popular and with vector systems that can more efficiently target active chromatin in CHO cells antibiotic selection puromycin can be used as well to generate recombinant cells expressing proteins at high level This sort of system requires no special mutation so that non DHFR deficient host cell culture have been found to produce excellent levels of proteins Since CHO cells have a very high propensity of genetic instability like all immortalised cells one should not assume that the names applied indicate their usefulness for manufacturing purposes For example the three K1 offspring cultures available in 2013 each have significant accumulated mutations compared to each other 13 Most if not all industrially used CHO cell lines are now cultivated in animal component free media or in chemically defined media and are used in large scale bioreactors under suspension culture 9 13 The complex genetics of CHO cells and the issues concerning clonal derivation of cell population was extensively discussed 18 19 Genetic manipulation editMuch of the genetic manipulation done in CHO cells is done in cells lacking DHFR enzyme This genetic selection scheme remains one of the standard methods to establish transfected CHO cell lines for the production of recombinant therapeutic proteins The process begins with the molecular cloning of the gene of interest and the DHFR gene into a single mammalian expression system The plasmid DNA carrying the two genes is then transfected into cells and the cells are grown under selective conditions in a thymidine lacking medium Surviving cells will have the exogenous DHFR gene along with the gene of interest integrated in its genome 20 21 The growth rate and the level of recombinant protein production of each cell line varies widely To obtain a few stably transfected cell lines with the desired phenotypic characteristics evaluating several hundred candidate cell lines may be necessary The CHO and CHO K1 cell lines can be obtained from a number of biological resource centres such as the European Collection of Cell Cultures which is part of the Health Protection Agency Culture Collections These organizations also maintain data such as growth curves timelapse videos of growth images and subculture routine information 22 Industrial use editCHO cells are the most common mammalian cell line used for mass production of therapeutic proteins such as monoclonal antibodies used in 70 of therapeutic mAbs 2 They can produce recombinant protein on the scale of 3 10 grams per liter of culture 9 Products of CHO cells are suitable for human applications as these mammalian cells perform human like post translational modifications to recombinant proteins which is key to the functioning of several proteins 23 See also edit nbsp Wikimedia Commons has media related to CHO cells Cell culture Drug development Preclinical developmentReferences edit a b c Eberle Christian 3 May 2022 CHO cells 7 facts about the cell line derived from the ovary of the Chinese hamster evitria Retrieved 30 January 2024 a b c Wurm FM 2004 Production of recombinant protein therapeutics in cultivated mammalian cells Nature Biotechnology 22 11 1393 1398 doi 10 1038 nbt1026 PMID 15529164 S2CID 20428452 a b c Vital Tools A Brief History of CHO Cells PDF LSF Magazine Winter 2015 pp 38 47 Retrieved 5 April 2023 Young C Smyly H Brown C March 1924 Experimental kala azar in a hamster Experimental Biology and Medicine 21 6 357 359 doi 10 3181 00379727 21 182 ISSN 1535 3702 Fanelli Alex 2016 CHO Cells Retrieved 28 November 2017 Du C Webb C 2011 Cellular Systems Comprehensive Biotechnology Elsevier pp 11 23 doi 10 1016 b978 0 08 088504 9 00080 5 ISBN 9780080885049 Tihanyi B Nyitray L December 2020 Recent advances in CHO cell line development for recombinant protein production Drug Discovery Today 38 25 34 doi 10 1016 j ddtec 2021 02 003 hdl 10831 82853 PMID 34895638 However 70 of biologics and almost all mAbs are produced in Chinese hamster ovary CHO cells as the most commonly used and preferred hosts for biopharmaceutical protein production Liang K Luo H Li Q 2023 Enhancing and stabilizing monoclonal antibody production by Chinese hamster ovary CHO cells with optimized perfusion culture strategies Frontiers in Bioengineering and Biotechnology 11 1112349 doi 10 3389 fbioe 2023 1112349 PMC 9895834 PMID 36741761 Since 2016 about 70 of all rBPs and mAbs were produced from Chinese hamster ovary CHO cell lines a b c d Wurm FM Hacker D 2011 First CHO genome Nature Biotechnology 29 8 718 20 doi 10 1038 nbt 1943 PMID 21822249 S2CID 8422581 Ahsan A S M Hiniker M A Davis T S Lawrence M K Nyati 2009 Role of Cell Cycle in Epidermal Growth Factor Receptor Inhibitor Mediated Radiosensitization Cancer Research 69 12 5108 5114 doi 10 1158 0008 5472 CAN 09 0466 PMC 2697971 PMID 19509222 CHO cells 7 facts about the cell line derived from the ovary of the Chinese hamster evitria AG 3 May 2022 Tjio J H Puck T T 1958 Genetics of somatic mammalian cells II chromosomal constitution of cells in tissue culture J Exp Med 108 2 259 271 doi 10 1084 jem 108 2 259 PMC 2136870 PMID 13563760 a b c d Lewis NE Liu X Li Y Nagarajan H Yerganian G O Brien E et al 2013 Genomic landscapes of Chinese hamster ovary cell lines as revealed by the Cricetulus griseus draft genome Nature Biotechnology 31 8 759 765 doi 10 1038 nbt 2624 PMID 23873082 Puck TT Cieciura SJ Robinson A 1958 Genetics of Somatic Mammalian Cells III Long Term Cultivation of Euploid Cells from Human and Animal Subjects Journal of Experimental Biology 108 6 945 956 doi 10 1084 jem 108 6 945 PMC 2136918 PMID 13598821 Ham RG 1965 CLONAL GROWTH OF MAMMALIAN CELLS IN A CHEMICALLY DEFINED SYNTHETIC MEDIUM Proceedings of the Natural Academy of Sciences 53 2 288 293 doi 10 1073 pnas 53 2 288 PMC 219509 PMID 14294058 a b Urlaub G Chasin LA July 1980 Isolation of Chinese hamster cell mutants deficient in dihydrofolate reductase activity Proceedings of the National Academy of Sciences of the United States of America 77 7 4216 4220 Bibcode 1980PNAS 77 4216U doi 10 1073 pnas 77 7 4216 PMC 349802 PMID 6933469 a b Urlaub G Kas E Carothers AD Chasin LA June 1983 Deletion of the diploid dihydrofolate reductase locus from cultured mammalian cells Cell 33 2 405 412 doi 10 1016 0092 8674 83 90422 1 PMID 6305508 Wurm Florian Wurm Maria 2017 Cloning of CHO cells productivity and genetic stability a discussion Processes 5 4 20 doi 10 3390 pr5020020 Reinhart D Damjanovic L Kaisermayer C Sommeregger W Gili A Gasselhuber B Castan A Mayrhofer P Grunwald Gruber C Kunert R March 2019 Bioprocessing of Recombinant CHO K1 CHO DG44 and CHO S CHO Expression Hosts Favor Either mAb Production or Biomass Synthesis Biotechnology Journal 14 3 e1700686 doi 10 1002 biot 201700686 PMID 29701329 S2CID 13844297 Lee F Mulligan R Berg P Ringold G 19 November 1981 Glucocorticoids regulate expression of dihydrofolate reductase cDNA in mouse mammary tumour virus chimaeric plasmids Nature 294 5838 228 232 Bibcode 1981Natur 294 228L doi 10 1038 294228a0 PMID 6272123 S2CID 2501119 Kaufman RJ Sharp PA 25 August 1982 Amplification and expression of sequences cotransfected with a modular dihydrofolate reductase complementary DNA gene Journal of Molecular Biology 159 4 601 621 doi 10 1016 0022 2836 82 90103 6 PMID 6292436 General Cell Collection CHO K1 Hpacultures org uk 2000 01 01 Retrieved 2013 05 21 Tingfeng Lai et al 2013 Advances in Mammalian Cell Line Development Technologies for Recombinant Protein Production Pharmaceuticals 6 5 579 603 doi 10 3390 ph6050579 PMC 3817724 PMID 24276168 External links editChinese Hamster Genome Database Recombinant Protein Therapeutics from CHO Cells 20 Years and Counting Puck TT Cieciura SJ Robinson A December 1958 Genetics of somatic mammalian cells III Long term cultivation of euploid cells from human and animal subjects J Exp Med 108 6 945 56 doi 10 1084 jem 108 6 945 PMC 2136918 PMID 13598821 Cellosaurus entry for CHO Cellosaurus entry for CHO K1 Cellosaurus entry for CHO DG44 Cellosaurus entry for CHO DXB11 Retrieved from https en wikipedia org w index php title Chinese hamster ovary cell amp oldid 1201640581, wikipedia, wiki, book, books, library,

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