CHO Cell Transfection: Reagents, Methods, Protocols

CHO Cells

CHO cells (Chinese Hamster Ovary cells) are a laboratory-cultured cell line derived from cells of the ovaries of Chinese hamsters. Chinese hamsters are a popular laboratory mammal, partially due to their small size and low chromosome number, which makes them a good model for tissue culture and radiation studies. CHO cells are a commonly-used mammalian cell model used in biology, medical and pharmaceutical research. In addition, they are frequently used for commercial purposes to manufacture therapeutic recombinant proteins.

CHO Cell Line Origin

CHO is an acronym for Chinese Hamster Ovary, which alludes to the origin of the CHO cell line, a line that has become a hugely popular research tool in the molecular biology community. The Chinese Hamster was brought to the US in 1948. In 1957, T. Puck obtained a Chinese hamster from a lab at the Boston Cancer Research Foundation, where he used it to derive the original CHO cell line. Since then, CHO cells have been found useful for many research purposes.

Characteristics of CHO Cells

Over the 60 year history of CHO cell studies, multiple different lines with different attributes have been derived from the original cell line. A common CHO derivative is CHO-K1, which has less DNA than the original CHO cells. A later mutation of CHO-K1 generated CHO-DXB11 (also known as CHO-DUKX), which lacks dihydrofolate reductase (DHFR) activity. Another offshoot of the original CHO cell line was CHO-pro3, which is proline-dependent. CHO-pro3 was then later mutated to create CHO-DG44, which also is DHFR-deficient (link).

CHO cells are important in research for their stability due to a low rate of spontaneous transformation.  Also, the biomanufactured recombinant proteins generated by CHO cells are functionally and structurally similar to native proteins. These include CD4 cell surface antigen, interferon, factor VIII and prorenin.

DHFR-deficient CHO Cell Lines and Stable Transfection

The DHFR-deficient strains require supplementation with glycine, hypoxanthine and thymidine. These strains were used to demonstrate that an exogenous DHFR gene could be stably transfected and selected using glycine/hypoxanthine/thymidine deficient (i.e. GHT-minus) media into cells that would otherwise be DHFR-deficient. This selection method has become a standard method for the establishment of stable transfection in CHO cell lines intended for production of therapeutic proteins. A gene that expresses the protein of interest and the DHFR gene are either combined in one mammalian expression vector or put into separate vectors. The plasmid or plasmids then are transfected into the CHO cells and the cells are grown in GHT-minus media to provide a selective environment. As a result, all surviving cells have copies of the DHFR gene and the gene of interest integrated into their genome.

Links

Chinese Hamster Ovary (Wikipedia)

CHO Transfection Kit – Commercially available from Altogen Biosystems

CHO Cell Line – Commercially available from ATCC

CHO Xenograft Studies – In Vivo Laboratory Contract Research by Xenograft Labs

Stable CHO RNAi Cell Line Generation – Gene silencing in CHO cells

In Vivo Transfection Products – Commercially available from Altogen Biosystems