Chromosomal instability in acute myelocytic leukemia and myelodysplastic syndrome patients among atomic bomb survivors

To clarify the mechanism of leukemogenesis in atomic bomb survivors, leukem ic cells were investigated using fluorescence in situ hybridization (FISH) analysis on the basis of conventional G-banding in patients with a history of radiation exposure and also in de novo patients. Conventional G-banding showed higher incidences (p < 0.005) of structural and numerical abnormalit ies without any specific types of chromosome aberrations in the group expos ed to a dose of more than one Gy, compared to the non-exposed group. FISH a nalysis revealed significantly higher incidences (P < 0.05) of subclones wi th monosomy 7 and deletion of the 20q13.2 region, which were not found in c onventional cytogenetic analysis in the exposed group (more than one Gy) co mpared to the non-exposed controls. Furthermore, segmental jumping transloc ation (SJT) of the c-MYC gene region was observed only in the exposed group . These chromosomal instability suggested that the leukemic cells from the heavily exposed patients contained persistent cellular genetic instability which may strongly influence the development of leukemia in people exposed to radiation.