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Chinese hamster ovary (CHO) cells are a mammalian cell line derived from the ovary of the Chinese hamster (Cricetulus griseus), widely used in laboratories as host cells for making recombinant proteins. This page is general reference for researchers and lab staff, not medical advice, and compares the two main selection systems used to build CHO production lines.
Short answer
CHO cells are a long-established hamster ovary cell line. Because they multiply quickly and can produce large amounts of protein, they serve as host cells for protein-based therapies; NIST describes them as “microscopic medicine factories”. The cells are production hosts, not a treatment themselves.
Definition and scope
ATCC’s catalogue entry for CHO-K1 (CCL-61) lists the species as Cricetulus griseus, the tissue as ovary, the morphology as epithelial-like and the growth mode as adherent. ATCC describes CCL-61 as a subclone of the parental CHO line, which was started from an ovary biopsy of an adult Chinese hamster in 1957 (depositor: T. T. Puck). Its recommended culture conditions are F-12K medium with 10% fetal bovine serum, at 37 °C and 5% CO2.
CHO cells and CHO cell lines
“CHO cells” is the general term. A “CHO cell line” (or “CHO cell lines” in the plural) is a specific, named derivative such as CHO-K1, DXB11 or DG44, each with its own history and genetic background. Records of which line, which source and which medium were used belong in any methods section, because the lines are not interchangeable.
How CHO cells are used in practice
NIST notes that CHO cells make protein-based therapies for conditions including leukemia, hemophilia and cancer, and that the arrival of recombinant DNA technology in the 1980s expanded their use. A 2022 review of high-yield clone screening (Yang et al., Frontiers in Bioengineering and Biotechnology) adds that CHO post-translational modifications are similar to those of human cells and that using CHO can avoid human virus infection of the product.
To make a production line, a gene for the protein is introduced into a host and cells that carry it are selected. The review describes two common selection systems.
Selection systems compared
| Feature | DHFR system | Glutamine synthetase (GS) system |
|---|---|---|
| Host cells | DXB11 and DG44, CHO mutants with the DHFR gene mutated or deleted | CHO-K1 was the first line used in the GS system |
| Selection marker | DHFR (host needs glycine-hypoxanthine-thymidine medium unless DHFR is supplied by transfection) | Glutamine synthetase, with the inhibitor MSX in glutamine-free medium |
| Raising expression | Gradual escalation of methotrexate (MTX) | Can reach sufficient expression in one selection round |
Source: Yang et al. 2022, PMC9247297 (read 2026-11-07). The table is limited to what that review states; other CHO derivatives and suspension-adapted lines are described by their suppliers.
Where it matters for labs and supply decisions
A record-keeping checklist for a CHO line
- Line identity: the exact name (for example CHO-K1, ATCC CCL-61) and the supplier’s product sheet.
- Growth mode and medium: ATCC lists CCL-61 as adherent in F-12K with 10% FBS; if a protocol uses a different medium or serum-free conditions, record it. See the dictionary entries for fetal bovine serum, chemically defined media and xeno-free media.
- Selection system: DHFR or GS, and the selection agent used (MTX or MSX).
- Biosafety: follow the biosafety level on the supplier’s current product sheet and your institution’s biosafety committee requirements.
Host cell proteins
Host-cell proteins from CHO cells can contaminate a protein product, and NIST notes they can potentially cause an adverse immune reaction. NIST has built a mass-spectral library of CHO peptides, available through the NIST Mass Spectrometry Data Center, to identify them, noting that immunoassays are slower and do not identify the contaminant.
A reference cell line
NIST offers NISTCHO (RM 8675), a CHO line engineered by MilliporeSigma in collaboration with NIST and NIIMBL that expresses a non-originator version of the NISTmAb antibody, described as an open-access line any researcher can obtain.
For assays run on cultured cells, see our guides to the cell proliferation assay, the Caco-2 cell line and viral titer.
Common misunderstandings
- “CHO cells are a treatment.” They are the host that manufactures protein-based therapies; the product, not the cell, is the therapy.
- “All CHO cells are the same.” Lines differ by derivation and genetic background, and selection systems depend on the host (DHFR-deficient DXB11/DG44 versus CHO-K1 in the GS system).
- “CHO is a human cell line like HeLa.” CHO cells are from a Chinese hamster.
FAQ
What are Chinese hamster ovary cells used for?
Mainly as host cells for producing recombinant proteins, including protein-based therapies, according to NIST.
What is a CHO cell line?
A named derivative of the original hamster ovary culture, such as CHO-K1, DXB11 or DG44.
What do CHO cells need to grow?
For ATCC CCL-61: F-12K medium with 10% FBS at 37 °C and 5% CO2, as an adherent culture. Other lines and serum-free processes use other media.
Sources
- ATCC, CHO-K1 (CCL-61) product page, https://www.atcc.org/products/ccl-61 (read 2026-11-07).
- NIST, “CHO and Tell”, https://www.nist.gov/news-events/news/2018/02/cho-and-tell (read 2026-11-07).
- NIST, NISTCHO monoclonal antibody-producing cell line, https://www.nist.gov/programs-projects/nistcho-monoclonal-antibody-producing-cell-line (read 2026-11-07).
- Yang et al., “Screening Strategies for High-Yield CHO Cell Clones”, Front Bioeng Biotechnol 2022, https://pmc.ncbi.nlm.nih.gov/articles/PMC9247297 (read 2026-11-07).
