The U-2 OS cell line was initiated in the 1960s by J. Ponten and E. Saksela from bone tissue removed from a moderately differentiated sarcoma of the tibia found in a fifteen-year-old girl diagnosed with osteosarcoma. Testing has shown that the human epithelial line is negative for simian virus 40, respiratory syncytial virus, and adenoviruses.

In the early 1970s, major stocks of the U-2 OS line were discovered to be contaminated with mycoplasmas, a group of parasitic pathogenic microorganisms, but the contamination was subsequently eliminated. U-2 OS cells are positive for both insulin-like growth factor I (IGF-I) and insulin-like growth factor II (IGF II) receptors. The established line also expresses various antigens, including blood type A, Rh+, HLA A2, Aw30, B12, Bw35, and B40(+/-).

Osteosarcoma, also known as also known as osteogenic sarcoma, is a common variety of bone cancer that most typically affects large bones, such as those of the arms and legs. Osteosarcomas usually form from osteoblasts and are particularly prevalent among adolescents undergoing rapid growth. The tumors are twice as likely to occur in boys as girls, presumably because males are generally considerably larger than females and, therefore, experience greater physical growth. Osteosarcoma tends to be aggressive and may metastasize early during the progression of the disease. No predisposing risk factor can be identified in most patients that develop osteosarcoma.

The adherent culture of human osteosarcoma cells (U-2 OS line) featured in the digital image above was transfected with a pDsRed-Mitochondria plasmid subcellular localization vector, thus localizing a red fluorescent protein tag to the intracellular mitochondrial network. The culture was also immunofluorescently labeled with mouse anti-alpha-tubulin followed by a secondary antibody (goat anti-mouse IgG) conjugated to Marina Blue to target microtubules. Cell nuclei were counterstained with SYTOX Green. 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.

Proximity of the Mitochondrial and Filamentous Actin Networks in U-2 OS Cells - The proximity of the intracellular mitochondrial and filamentous actin networks was visualized in a culture of human osteosarcoma cells with MitoTracker Red CMXRos and Alexa Fluor 488 conjugated to phalloidin. DNA in the cell nucleus was counterstained with 4',6-diamidino-2-phenylindole (DAPI).

Osteosarcoma Cells Triple Labeled with MitoTracker Red CMXRos, Alexa Fluor 488, and Hoechst 33342 - The mitochondrion-selective stain MitoTracker Red CMXRos was utilized to label the mitochondrial network in a culture of U-2 OS cells, and the popular cell-permeant nuclear counterstain Hoechst 33342 was used to label cell nuclei. In addition, filamentous actin was targeted with Alexa Fluor 488 conjugated to phalloidin.

Localizing Mitochondria in Human Bone Cancer Cells with DsRed Fluorescent Protein - Immunofluorescence, a subcellular localization vector, and a classic nucleic acid stain were utilized to triple label a culture of U-2 OS cells. The specimen was transfected with a pDsRed-Mitochondria plasmid localization vector to localize a red fluorescent protein tag to the intracellular mitochondrial network and was treated with mouse anti-alpha-tubulin followed by a secondary goat anti-mouse antibody conjugated to Marina Blue to target the microtubule network. Cell nuclei were counterstained with SYTOX Green.

F-Actin and Mitochondria Distribution in U-2 OS Cell Cultures - Cultured osteosarcoma cells (U-2 OS line) were labeled with MitoTracker Red CMXRos (red emission) and Alexa Fluor 488 (green emission) conjugated to phalloidin, targeting mitochondria and F-actin, respectively. The culture was counterstained with DAPI, which fluoresces blue upon binding to AT regions of DNA (labeling the nucleus).

Visualizing the Actin Cytoskeletal Framework, the Mitochondrial Network, and the Nucleus in Osteosarcoma Cells - The relationship between the filamentous actin cytoskeletal framework and the mitochondrial network was visualized in the culture of human osteosarcoma cells presented in this section with the green fluorescent dye Alexa Fluor 488 conjugated to phalloidin and MitoTracker Red CMXRos, respectively. DNA in the cell nucleus was targeted with Hoechst 33342.

U2-OS Cancer Cell Cultures Stained with MitoTracker Red CMXRos, Alexa Fluor 488, and DAPI - F-actin, mitochondria, and cell nuclei were fluorescently labeled in the culture of U-2 OS cells presented in this section with MitoTracker Red CMXRos, Alexa Fluor 488 conjugated to phalloidin, and DAPI, respectively.