Chromosome studies of two transplantable leukemias of BN mice

Karyotypes of two transplantable murine ascites leukemias, LBN/a2 and LBN/b3, were studied with the use of the trypsin-Giemsa technique. The original tumors arose in adult female mice of strains BN/a and BN/b after prolonged antilymphocyte globulin administration. The karyotypes of both leukemias showed similar patterns. Both were hyperdiploid with modal chromosome numbers of 41 and 42 in LBN/a2 and LBN/b3, respectively. The cells consisted of an average of 37 normal chromosomes and 4--5 abnormal chromosomes. The most consistent karyotype deviation was monosomy of the X-chromosome and of several autosomes: no. 9, 14, and 7 in the LBN/a2 line and no. 7, 12, 14, and 9 in the LBN/b3 line. In most LBN/b3 cells and in a lower proportion of LBN/a2 cells, trisomy of chromosome no. 15 was found. With regard to the occurrence of abnormal marker chromosomes, both tumors exhibited great cell-to-cell variation. Two of the markers were common to both leukemia lines.