Chromosomal aberrations observed in 52 mouse myeloid leukemias

Chromosomes of 52 cases of mouse myeloid leukemia were examined. There were 5 myeloblastic leukemias, 22 granulocytic leukemias, 17 myelomonocytic leukemias, and 8 monocytic leukemias. Fifty cases were radiation induced and the other 2 were nonirradiated. Each case had leukemic cells with 1 to 10 marker chromosomes. Partially deleted No. 2 chromosomes appeared in 49 cases, including 2 nonirradiated cases. These deleted No. 2 chromosomes were varied in size, and they were classified into 7 types according to morphological features. There was no type-dependent difference in histological or cytological features among the 7 types. It was found that the chromosomal segment lying between Regions 2C and 2D was commonly missing from all of the deleted No. 2 chromosomes. In addition to such No. 2 chromosomes, an anomaly in chromosome 6 was observed in 16 cases, of which 12 cases were granulocytic leukemia. The abnormalities of chromosomes 3 and 9 were next most frequent, appearing in 14 cases each. Besides such structural anomalies, numerical changes involving the Y chromosome (33 cases), chromosome 6(6 cases), and chromosome 15 (4 cases) were also found. Characteristics of the karyotypes of the mouse myeloid leukemia in comparison with other leukemias were noted. The significance of the specific segments of the chromosomes which were commonly missing or trisomic in the karyotypes of neoplasias in mice, rats and humans was discussed. It was suggested that the genesis of myeloid leukemia was greatly influenced by the genetic information on chromosome 2 in mice.