The RNA tumor viruses--background and foreground.

The members of the RNA tumor virus (or leukovirus) group of animal viruses replicate via a DNA intermediate and transmit their information stably in cells as DNA. Although some of these viruses are capable of inducing neoplastic transformation, others are not. These viruses may be related to spontaneous neoplasia, but the relationship is that of analogy rather than etiology. The relationship of these viruses to human disease is unknown. Two models of spontaneous neoplasia that involve either activation of the information of a transforming RNA tumor virus or the creation of information for neoplastic transformation by recombination involving information transfer from RNA to DNA are being tested in model systems.