Abstract
Two 2-nitronaphthofuran derivatives exhibited a dose-dependent lethal effect on Rous sarcoma virus-tranformed chicken embryo fibroblasts. When they were added at time of infection, they prevented cell transformation, but not virus replication, in a dose-dependent manner. Since the two derivatives inhibited mainly the DNA sythesis, we assume that they altered some early DNA-dependent cell event required for cell transformation and not for the integration of provirus.