Activation In Vitro, by 5-lododeoxyuridine, of a Latent Virus Resembling C-Type Virus in a Human Sarcoma Cell Line

A biopsy specimen of an undifferentiated human sarcoma contained particles resembling type-C particles of oncornavirus. Cultures of this neoplasm grew as spindle cells that after 8 weeks transformed to epithelioid-like cells with rounded cells that piled up and were shed into the culture fluid. Cells from cultures were devoid of virus-like particles on repeated electron microscopic examination. Attempts to activate a virus by cocultivation with normal human cells or by exposure to ultraviolet or X-ray irradiation failed to yield virus, as determined by electron microscopy or focus formation of normal cells with cell-free filtrates from the culture. However, when the cells were cultured in medium containing 5-iododeoxyuridine, budding particles resembling those formed by C-type oncornavirus were observed.