Chromosomes of Tumor Cells. I. Murine Leukemias Induced by One or Two Injections of 7,12-Dimethylbenz[a]anthracene

Abstract

One or two injections of 7,12-dimethylbenz[a]anthracene (DMBA) into baby mice of the low-leukemic Swiss stock resulted in a high incidence of lymphatic leukemias. The first mouse, which died at 65 days of age, had a thymic lymphosarcoma, greatly enlarged spleen and lymph nodes, and infiltration of leukemic cells in the kidneys and lungs. Four months after DMBA injection 50 percent of all mice developed leukemias, which were transplantable to adults of the same mouse strain. The chromosome number was studied in thymic lymphosarcomas of 16 mice and in various infiltrated organs of 3 mice. Fifteen of the 16 thymic lymphosarcomas consisted of a population of cells containing predominantly 41 chromosomes, as compared with 40 chromosomes in normal tissues. There were also aneuploid cells in the infiltrated spleen and lymph nodes. Cells having predominantly 42 chromosomes were observed in the enlarged thymus, spleen, and lymph nodes of one mouse. The preference of one aneuploid chromosome number in the thymic lymphosarcomas is discussed in regard to formation and selection of the neoplastic cell.