A molecular approach to leukemogenesis: mouse lymphomas contain an activated c-ras oncogene.

Abstract

By inducing mouse thymomas with carcinogens and .gamma.-radiation, the potential of tumor DNA to induce foci was studied in rodent fibroblasts. A high percentage of the tumors used transformed the cultured cells, and the oncogenic phenotype segregated with extra copies of the c-ras gene family. There appears to be selectivity in the activated gene because so far all analyzed tumors induced by carcinogen activated the N-ras gene, and those induced by radiation activated the K-ras gene. The K-ras gene is the cellular counterpart of the viral ras oncogene in Kirsten murine sarcoma virus, but the N-ras was not yet found in a retrovirus. The transformed cells have a marked increase in expression of the oncogene at the RNA and protein level. This model system might be a powerful tool in the study of leukemogenesis.