Karyotypic changes in serial transfers of leukemic cells of AKR mouse.

Four spontaneous AKR leukemias (T67, T68, T70, and T74) with a modal chromosome number of 40 were transplanted serially to syngeneic mice in order to assess the significance of trisomy 15 and other karyotypic changes in the development of leukemia. In T67 and T70, the chromosomally normal cell disappeared completely or decreased considerably in frequency at the first passage in vivo. The karyotype of the modal cells changed continuously in T67 during transplantation, conserving trisomy 17, while the pseudodiploid cells with trisomy 15 and monosomy X were stable from the first to the seventh transplant generations of T70. In contrast to these results, the primary cell population of T68 and T74 with modal cells having a normal karyotype remained essentially unchanged throughout 7 or 15 transplant generations, despite the occurrence of aneuploidy, which included trisomy 15 or trisomy 17 in low frequencies. It is thus evident that the diploid cell is compatible with being leukemic and that neither trisomy 15 nor trisomy 17 is necessary for the initiation and progression of AKR leukemia, although the former was detected in three of four primary leukemias used for this experiment and in all four during transplantation.