A SPECIFIC CHROMOSOMAL DELETION IN MURINE LEUKEMIC-CELLS INDUCED BY RADIATION WITH DIFFERENT QUALITIES

G-banded metaphase chromosomes prepared from 14 male CBA/Ca mice with histologically confirmed myeloid leukemia (ML) were studied in an effo rt to identify specific chromosomal changes associated with radiation leukemogenesis. The chromosome studies were undertaken as part of a la rger investigation of radiation carcinogenesis, in which mice were exp osed to radiation of several different qualities, i.e., x-rays, gamma- rays and ''monoenergetic'' fast neutrons of 5 mean energies ranging fr om 0.2 to 14 MeV. The 14 ML cases showed no histologically phenotypic differences and they were transplantable in syngeneic mice. We detecte d a specific chromosomal deletion in 1 copy of mouse chromosome 2 at r egions D-E in all radiation-induced ML cells, regardless of radiation quality. Our results strongly implicate the involvement of genes withi n or close to regions D-E of chromosome 2 in radiation leukemogenesis. In addition to the specific deletion in chromosome 2, loss or gain of the Y chromosome was also detected in some cells from 6 ML cases. Bec ause this hypo- or hyperploidy occurred in only a small fraction of le ukemic cells, a causative role in radiation leukemogenesis appears unl ikely.