Experimental carcinogenesis: induction of multiple tumors by viruses.

Many viruses are able to cause the development of tumors when inoculated into suitable vertebrate hosts. Among them, polyoma virus can induce tumors in several mammalian species: not only many different kinds of tumor, but a large number of tumors within a single individual. Tissue culture studies employing cells from mice and hamsters, as well as observations of the manner of tumor development following polyoma virus injection in these species in vivo, suggest that some, or all, of the tumors so induced are multiple primaries. Because of the availability of mice of different genetic constitutions, the relative ease with which mouse cells from both normal and malignant tissue can cultivate in vitro, the known responses of mice to many carcinogenic agents, as well as the availability of transplantable, metastasizing mouse tumors, it is believed the polyoma virus/mouse host system would provide a highly suitable model in which an experimental approach to the elucidation of mechanisms for the origin of multiple tumors would be possible.