Trisomy no. 15 in murine thymomas induced by chemical carcinogens, X-irradiation, and an endogenous murine leukemia virus.

Chromosome banding techniques were used to examine the karyotype of tumor cells from thymic lymphomas induced by three different carcinogens (X-irradiation, polycyclic aromatic hydrocarbons, and an endogenous leukemogenic virus) after injection into neonatal mice of 2 different inbred mouse strains (CFW/D and C57BL/Ka). A total of 89 tumors were studied, and of these 85.4% were characterized by a modal chromosome number of 41. The additional chromosome was the result of a specific abnormality identified as trisomy of chromosome no. 15. The results obtained were independent of the carcinogenic agents and the strain of mouse used. Of the 13 tumors found to have a normal chromosome complement, 4 were induced by X-irradiation and the remaining 9 by the chemical carcinogens. All 15 virus-induced tumors analyzed had a modal chromosome number of 41.