Characterization of virus-free guinea pig tumors induced by Kirsten sarcoma virus

Tumors were induced by Kirsten sarcoma virus (KiSV) in an inbred guinea pig, strain 13. The tumor cells were established in culture and characterized. The KiSV-induced sarcoma cells were virus-free and nonproducing; however, they contained resuable sarcoma genome. A type B guinea pig retravirus was readily activated from the tumor cells after induction with 5-bromodeoxyuridine (BUDR). BUDR induction of guinea pig retravirus was further enhanced by treatment with dexamethasone, a synthetic glucocorticoid hormone.