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All About CHO – A discussion on everything from the basics to troubleshooting
Last week, we finished our Ask the Expert discussion on All About CHO. While CHO cells are a popular choice for biopharmaceutical manufacturing, they can still present a challenge to work with. With so many cell culture scientists regularly searching for ways to improve on product yield, product quality, cost, and a myriad of other manufacturing challenges faced with biopharmaceutical manufacturing, we felt that CHO cell production was a great topic to pursue.
This session, sponsored by Life Technologies and hosted by Timothy Fawcett, Ph.D. was a good discussion and with such a broad topic, we had quite a range of questions. Dr. Fawcett who has been in biotechnology for over 30 years, provided real hands-on suggestions that readers could benefit from right away.
Question topics included:
- Why CHO cells are so popular in biomanufacturing
- Different types of CHO cells
- CHO genome sequence
- Shipping requirements
- Lactic acid build up in culture
I have selected a few of the submitted questions and answers to include below. For a full list of questions and answers, please see Ask the Expert – Everything CHO.
Hi, I am wondering if the CHO genomic sequence known?
This is a good question and the answer is yes! The paper by Xun Xu et al., Nature Biotechnology, Vol 29, No 8, 201, pg 735. reports that a CHO-K1 ancestral cel line was sequenced. There were 24,383 predicted genes. What is very interesting about the paper is that the authors focused on investigating genes involved in glycosylation. Homologs of most human glycosylation-associated genes are present in the CHO-K1 genome. The authors also point out correctly that this is important since CHO cells are used to make human like therapeutic antibodies and glycosylation patterns are critical to function and turnover rates. Ultimately this research may lead to making CHO cells even better for bio-production than it already is.
What is the difference between all these different types of CHO cells? I read about CHO-K1 and CHO-DG44 all the time.
There are many types of CHO (Chinese Hamster Ovary) cells in use today. It is a bit of a mystery when CHO cells originated but it is thought the line was derived in the 1960′s. Dr. Theodore Puck received a female Chinese Hamster from a laboratory at the Boston Cancer Research Foundation and used the animal to derive the original cell lines. One line was known as CHO-K1, was obtained from those first CHO lines. CHO-K1 is an adherent line and was traditionally grown of F12 Medium supplemented with 10% FBS. The CHO lines were thought to be important because they had few chromosomes for a mammalian cell and were used for radiation cytogenetics and they were known for their ease of culturing. CHO-K1 cells also do not express EGFR.
CHO-DG44 cells were derived from the original CHO-K1 cells by several rounds of mutagenesis that deleted both copies of the dhfr genes. Dihydrofolate reductase (dhfr) is required for the de novo synthesis of purines, thymidylic acid, and certain amino acids and is required for growth and proliferation of CHO cells. As a result CHO-DG44 cells require glycine, hypoxanthine and thymidine (GHT) for growth. This requirement allows for selection of recombinant clones by transfection of recombinant DNA plasmids containing a gene of interest and the replacement dhfr gene if cells grow on GHT minus medium then they have taken up the recombinant plasmid DNA and hopefully the gene of interest as well.