The CHO-K1 cell line was derived as a subclone from the parental CHO cell line established from the excised tissue of adult Chinese hamster ovary by T. T. Puck in 1957. Unlike the original CHO line, CHO-K1 cells require proline in the medium for growth in culture.

Often utilized as a transfection host, the CHO-K1 line is susceptible to a number of viruses including vesicular stomatitis (Indiana strain) and the Getah virus. CHO-K1 cells are resistant to poliovirus 2, Modoc virus, and button willow virus. The cells, which exhibit characteristics typical of epithelial cells and grow adherently to plastic and glass in culture, are negative for reverse transcriptase.

A standard cell line in molecular biology laboratories around the globe, CHO-K1 cells have been used for a wide array of research purposes. Studies that have utilized the cell line range from examinations of the mutational spectrum of 6-nitrosochrysene (6-NOC) in the hprt gene to analysis of the signaling pathway of apoptotic induction by oxidized low-density lipoprotein (oxLDL). CHO-K1 cells have also been employed to determine the effect of various cytotoxins on the assembly of filamentous actin and cell division, as well as to gain knowledge regarding the expression of certain human genes. For instance, one recent study demonstrated that CHO-K1 fibroblasts exhibit several preadipocyte-like characteristics, and that the expression of the human (beta)3 AR gene modifies the expression of PPAR(gamma) mRNA in these cells, resulting in the formation of lipids under certain culture conditions.

MitoTracker Orange CMTM Ros was utilized to fluorescently label the active mitochondria in a culture of Chinese hamster ovary cells (illustrated above). The specimen was additionally labeled with Oregon Green 488 conjugated to phalloidin and Hoechst 33258 to visualize the intracellular F-actin network and nuclear DNA, respectively. Images were recorded in grayscale with a 12-bit digital camera coupled to either a Nikon E-600 or Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.

Distribution of Mitochondria and Filamentous Actin in CHO-K1 Cell Cultures - The culture of CHO-K1 cells presented in this section was labeled with a triplet of fluorophores, including MitoTracker Orange CMTM Ros, Oregon Green 488, and Hoechst 33258. The Oregon Green probe was conjugated to phalloidin in order to target filamentous actin.