CHO Cell Transfection: Reagents, Methods, Protocols

CHO cells (Chinese Hamster Ovary cells) are a laboratory-cultured cell line derived from cells from 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. They are a commonly-used mammalian cell model used in biology and in 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 55 year history of CHO cell study, several different lines with different attributes have been derived from the original cell line. A common CHO derivative is CHO-K1, which has, to some extent, less DNA than 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).

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 (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 on one mammalian expression vector or put into separate vector. The plasmid or plasmids then are transfected into the CHO cells and the cells are then 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

CRO Pre-clinical Research Services – Commercially available from Altogen Laboratories

In Vivo Transfection Products – Commercially available from Altogen Biosystems