Molecular Evidence for a Viral Etiology of Human Leukemias, Lymphomas, and Sarcomas

Abstract

The experiments described were designed to probe further the etiologic significance of the earlier findings in human leukemia and lymphoma by Hehlmann and associates^13,14 and in sarcoma by Kufe and colleagues¹⁶ of RNA homologous to that of the Rauscher leukemia virus (RLV). The data obtained indicate that at least a portion of the viral-related RNA we were detecting is in the form of a 70S-RNA template physically associated with a reverse transcriptase, two of the diagnostic features of the RNA tumor viruses. Further, the DNA synthesized by the leukemic reverse transcriptase on its own endogenous template is related in sequence to RLV-RNA. This last finding completes the logic of our earlier experiments in which the DNA synthesized on RLV-RNA was used as a probe to find the viral-related information in leukemic cells. Finally, the data show that a reverse transcriptase and 70S RNA are associated with a particle possessing the exact density of oncogenic RNA viruses. The data we have detailed show that human leukemic cells contain a 70S RNA encapsulated with RNA-instructed DNA polymerase in a particle possessing the density characteristic of RNA viruses. Further, the DNA synthesized by the human RNA-enzyme complex hybridizes specifically with the RNA of a murine leukemogenic agent. Similar data are now available with human mammary cancers. Thus, for both leukemias and adenocarcinomas of the breast, four diagnostic features of the corresponding animal tumor viruses are exhibited by particles found in these analogous human neoplasias. The accumulating evidence for the involvement of RNA tumor viruses in at least some forms of human cancer is becoming more convincing. Final proof still requires the demonstration that the particles identified in human neoplastic tissues are infectious and transforming agents.