Malignant progression of a transformed rat cell line by transfer of the v-fos oncogene.

Transfer of the v-fos oncogene into a rat cell line transformed by Rous sarcoma virus increased both the spontaneous and experimental lung-metastasis. Metastatic ability of each v-fos transferred cell line was dependent on both the manner of integration and transcriptional amount of the v-fos oncogene, but did not correlate with the growth rate in vivo. Expression of the src, myc or ras genes were not altered by transfer of the v-fos gene, except that the myc expression was enhanced in the cell line, which acquired augmentation of growth rate in vivo but not metastatic potential to the lung. Cells of the metastatic lung nodules of each cell line also possessed exogenous fos DNA and the transcripts. These results suggest that v-fos oncogene functions in the transfected cells and causes malignant progression.