Influence of Mammary Tumor Virus on the Tumor-Producing Capabilities of Nodule Outgrowth Free of Mammary Tumor Virus

Summary

The hypothesis that mouse mammary tumor virus (MTV) can participate in the production of neoplastic variants within a population of nodule cells, as well as in the production of nodule variants, has been tested and answered in the affirmative. When virus-free nodule outgrowths were used as the test material, outgrowths infected with MTV gave rise to a significantly greater number of tumors within a shorter time than did the same outgrowths which remained virus-free. Thus the model for mammary gland tumorigenesis has been extended to include the action of MTV as an inciter of both the nodule and the neoplastic transformation. The existence of such virus-free nodules offers an excellent opportunity to study the individual and combined effects of chemical carcinogens and viruses on the neoplastic transformation.