Non-random duplication of chromosome 15 in murine T-cell leukemias: further studies on translocation heterozygotes.

Four combinations of translocation heterozygotes with cytogenetically distinct chromosomes 15 were used to investigate whether the T-cell leukemia-associated duplication of chromosome 15 is a non-random or a random event. In leukemias of AKR x CBAT6T6F1 (Group 1) and C57BL x CBAT6T F1 (Group IV) crosses the duplication was non-random, affecting the AKR-derived chromosome 15 (Group 1) and CBAT6T6-derived T (14;15) 6 chromosome (Group IV), respectively. In contrast, in leukemias induced in CBA x CBA T6T6F1 combinations (Group III) - where both chromosomes 15 (normal and translocated) were CBA-derived-the duplication was random. Similarly, in the Rb6;15 x CBAT6T6F1 cross (group II) the duplication of chromosome 15 appeared to be random. The results supported the hypothesis that the genetic content of chromosome 15 rather than its translocated state is decisive for the preferential duplication of this chromosome in T-cell leukemogenesis. However, the genetic background of the strain from which chromosome 15 is derived may also influence the duplication pattern of individual tumors.