Increased pathogenicity of avian sarcoma virus B77 in cyclophosphamide treated chickens.

: The course of sarcoma development was studied in cyclophosphamide treated and control chickens injected with avian sarcoma virus B77 (B77V). It was found that the incidence of sarcomas was the same for both groups of birds. Progressive growth of sarcomas as well as high tumor mortality was observed in drug treated birds, whereas frequent regressions occurred in controls. The drug treatment after B77V infection did not change the response patterns and no cytostatic effect of the drug was observed. Cyclophosphamide treatment improved the rescuability of B77V genome from the transformed virogenic mouse and rat cells in vivo.