Chinese Hamster Ovary cell
Encyclopedia
Chinese hamster ovary cells are a cell line derived from the ovary
of the Chinese hamster
. They are often used in biological and medical research and commercially in the production of therapeutic proteins. They were introduced in the 1960s and grow as a cultured
monolayer
. They require the amino acid
proline
in their culture medium.
CHO cells are used in studies of genetics, toxicity screening, nutrition and gene expression, particularly to express recombinant
proteins. Today, CHO cells are the most commonly used mammalian hosts for industrial production of recombinant protein therapeutics.
The use of the Chinese hamster in research began in 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 (also known as visceral leishmaniasis
), facilitating research in epidemiology
.
In 1948, the Chinese hamster was brought to the United States for breeding in research laboratories.
In the following years, the Chinese hamster became noteworthy for the cell lines that were derived from its tissues. Having a very low chromosome
number (2n=22) for a mammal
, the Chinese hamster is an ideal model for radiation cytogenetics and tissue culture.
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 and high protein production. They have become the mammalian equivalent of E. coli in research and biotechnology today, especially when long-term, stable gene expression and high yields of proteins are required.
CHO cells do not express the Epidermal growth factor receptor
(EGFR), which makes them ideal in the investigation of various EGFR mutations.
CHO-K1 was derived from the original cell lines; it contains a slightly lower amount of DNA than the original CHO. CHO-K1 was mutagenized to generate CHO-DXB11 (also referred to as CHO-DUKX or CHO-DUK-XB11), a cell line lacking DHFR activity (Urblaub and Chasin, 1980). These cells have a deletion of one dhfr allele and a missense mutation in the other. Subsequently, the proline-dependent CHO-pro3- strain, another derivative of the original CHO cell line, was mutagenized to yield CHO-DG44, a cell line with deletions of both dhfr alleles (Urlaub et al., 1983). These two DHFR-minus strains require glycine, hypoxanthine, and thymidine (GHT) for growth.
Although not initially intended recombinant protein manufacture, DHFR-minus CHO cells were used for a number of pioneering experiments demonstrating stable transfection with an exogenous dhfr gene via selection in GHT-minus medium (Ringold et al., 1981; Kaufman and Sharp, 1982; Scahill et al., 1983). This genetic selection scheme remains one of the standard methods to establish stably transfected CHO cell lines for the production of recombinant therapeutic proteins. The multistep process begins with the molecular cloning of the gene of interest (GOI) and the dhfr gene in a single or in separate mammalian expression vectors. The plasmid DNA(s) carrying the two genes are then delivered into cells by transfection, and the cells are grown under selective conditions in GHT-minus medium. Each surviving cell will have one or more copies of the exogenous dhfr gene, usually along with the GOI, integrated in its genome (Ringold et al., 1981; Kaufman and Sharp, 1982; Scahill et al., 1983). The integrated plasmid copy number varies widely from one recombinant cell to another, but there is almost always only one integration site per cell even if multiple plasmids are transfected (Wurm 1990). The growth rate and the level of recombinant protein production of each cell line also vary widely. To obtain a few stably transfected cell lines with the desired phenotypic characteristics, it may be necessary to evaluate several hundred candidate cell lines.
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 (ECACC) which is part of the Health Protection Agency Culture Collections. CHO-K1 data, such as growth curves, timelapse videos of growth, images and subculture routine information are available from ECACC.
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
of the Chinese hamster
Chinese hamster
The Chinese hamster , is a species of hamster originating from the deserts of northern China and Mongolia.- Description :...
. They are often used in biological and medical research and commercially in the production of therapeutic proteins. They were introduced in the 1960s and grow as a cultured
Microbiological culture
A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. Microbial cultures are used to determine the type of organism, its abundance in the sample being tested,...
monolayer
Monolayer
- Chemistry :A Langmuir monolayer or insoluble monolayer is a one-molecule thick layer of an insoluble organic material spread onto an aqueous subphase. Traditional compounds used to prepare Langmuir monolayers are amphiphilic materials that possess a hydrophilic headgroup and a hydrophobic tail...
. They require the amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
proline
Proline
Proline is an α-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that the human body can synthesize it. It is unique among the 20 protein-forming amino acids in that the α-amino group is secondary...
in their culture medium.
CHO cells are used in studies of genetics, toxicity screening, nutrition and gene expression, particularly to express recombinant
Recombinant DNA
Recombinant DNA molecules are DNA sequences that result from the use of laboratory methods to bring together genetic material from multiple sources, creating sequences that would not otherwise be found in biological organisms...
proteins. Today, CHO cells are the most commonly used mammalian hosts for industrial production of recombinant protein therapeutics.
The use of the Chinese hamster in research began in 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 (also known as visceral leishmaniasis
Visceral leishmaniasis
Visceral leishmaniasis , also known as kala-azar, black fever, and Dumdum fever, is the most severe form of leishmaniasis. Leishmaniasis is a disease caused by protozoan parasites of the Leishmania genus. This disease is the second-largest parasitic killer in the world , responsible for an...
), facilitating research in epidemiology
Epidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...
.
In 1948, the Chinese hamster was brought to the United States for breeding in research laboratories.
In the following years, the Chinese hamster became noteworthy for the cell lines that were derived from its tissues. Having a very low chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
number (2n=22) for a mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
, the Chinese hamster is an ideal model for radiation cytogenetics and tissue culture.
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 and high protein production. They have become the mammalian equivalent of E. coli in research and biotechnology today, especially when long-term, stable gene expression and high yields of proteins are required.
CHO cells do not express the Epidermal growth factor receptor
Epidermal growth factor receptor
The epidermal growth factor receptor is the cell-surface receptor for members of the epidermal growth factor family of extracellular protein ligands...
(EGFR), which makes them ideal in the investigation of various EGFR mutations.
CHO-K1 was derived from the original cell lines; it contains a slightly lower amount of DNA than the original CHO. CHO-K1 was mutagenized to generate CHO-DXB11 (also referred to as CHO-DUKX or CHO-DUK-XB11), a cell line lacking DHFR activity (Urblaub and Chasin, 1980). These cells have a deletion of one dhfr allele and a missense mutation in the other. Subsequently, the proline-dependent CHO-pro3- strain, another derivative of the original CHO cell line, was mutagenized to yield CHO-DG44, a cell line with deletions of both dhfr alleles (Urlaub et al., 1983). These two DHFR-minus strains require glycine, hypoxanthine, and thymidine (GHT) for growth.
Although not initially intended recombinant protein manufacture, DHFR-minus CHO cells were used for a number of pioneering experiments demonstrating stable transfection with an exogenous dhfr gene via selection in GHT-minus medium (Ringold et al., 1981; Kaufman and Sharp, 1982; Scahill et al., 1983). This genetic selection scheme remains one of the standard methods to establish stably transfected CHO cell lines for the production of recombinant therapeutic proteins. The multistep process begins with the molecular cloning of the gene of interest (GOI) and the dhfr gene in a single or in separate mammalian expression vectors. The plasmid DNA(s) carrying the two genes are then delivered into cells by transfection, and the cells are grown under selective conditions in GHT-minus medium. Each surviving cell will have one or more copies of the exogenous dhfr gene, usually along with the GOI, integrated in its genome (Ringold et al., 1981; Kaufman and Sharp, 1982; Scahill et al., 1983). The integrated plasmid copy number varies widely from one recombinant cell to another, but there is almost always only one integration site per cell even if multiple plasmids are transfected (Wurm 1990). The growth rate and the level of recombinant protein production of each cell line also vary widely. To obtain a few stably transfected cell lines with the desired phenotypic characteristics, it may be necessary to evaluate several hundred candidate cell lines.
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 (ECACC) which is part of the Health Protection Agency Culture Collections. CHO-K1 data, such as growth curves, timelapse videos of growth, images and subculture routine information are available from ECACC.
External links
- CHO cells Transfection and Selection Data
- Chinese Hamster Genome Database
- http://hugroup.cems.umn.edu/HuGroup/PDFs/Jayapal_et_al_CHO_Review.pdf