Cytology and growth characteristics of human tumour astrocytes transformed by Rous sarcoma virus.

Human tumour astrocytes (118MG) were exposed in vitro to the Engelbreth-Holm strain of Rous sarcoma virus at a multiplicity of infection of one. Morphological transformation of the cells in 60-mm plates was complete in 9-11 weeks after viral exposure. The transformed cells {EH-i 18MG) grew as a monolayer, upon which nests of rounded cells developed. From these nests, rounded cells shed into the medium and in turn on seeding formed a monolayer and repeated the cycle. The transformed cells contained the viral group-specific antigen in the cytoplasm, and produced Rous sarcomas in chickens. No complete virus was demonstrated in the mammalian cells. Electron micrographs of the parent 118MG and transformed EH-118MG cells gave further details of the structure of cytoplasmic protrusions which were formed in some of the free EH-i 18MG but not in the 118MG cells. Their nature is completely unknown.