Morphological Transformation of Rat Embryo Cells Induced by Diethylnitrosamine and Murine Leukemia Viruses2

Abstract

Secondary cultures of rat embryo cells were treated simultaneously with 0.1 mM diethylnitrosamine (DENA) and with either CF-1 or Rauscher C-type RNA murine leukemia virus. Cells treated with virus or chemical alone and untreated cultures were observed as controls. For 21 days, the chemically treated cultures were fed repeatedly with media containing DENA. After this period, DENA was removed permanently from the media, and the subcultures were subdivided 1:2 twice a week. The murine leukemia viruses multiplied in the rat cells, and each of the inoculated samples became an infected carrier culture. Virus-infected cells appeared slightly altered in that they were more crowded and seemed more epithelioid, but remained unchanged in all other aspects. Cells treated only with DENA appeared to remain normal, but virus-infected, DENA-treated cultures became overgrown with randomly oriented spindle cells between the sixth and twelfth subcultures. All cultures remained diploid for approximately 26–32 subcultures, after which only cultures treated with both virus and DENA became aneuploid. Untreated cultures or cultures treated with DENA alone or virus alone did not undergo morphological transformation and did not become aneuploid. These results, which indicated that both DENA and virus were required for transformation, suggested that the C-type RNA oncogene provided specific information for the transformation event.