In vitro transformation of primary and continuous rat fibroblasts by Rous sarcoma virus (Schmidt-Ruppin).

In vitro transformation of rat fibroblasts by the SCHMIDT-RUPPIN strain of Rous sarcoma virus is described. Primary rat embryo fibroblasts were transformed in 2 to 6 weeks after infection with the virus. The transformed cells were large, refractile and polygonal in appearance and produced multilayer colonies. Injection of the transformed cells to young and weanling Sprague-Dawley rats induced fibrosarcomas. The continuous cell line of rat fibroblasts was transformed by Rous sarcoma virus (SCHMIDT--RUPPIN) after I4 to 25 weeks. The transformation developed gradually from ~ or z islands of transformed cells per culture to a solid sheet of transformed cells. Cell cultures initiated tumours in young and weanling rats at the site of injection. Tumours grew slowly in weanling rats, while younger animals died f rom large tumours. These differences between young and old rats may reflect the immunological status of the host and/or the decrease in susceptibility of host cells to transformation by inoculated cell cultures.