Abstract
We developed a model to explain the frequency of clonal chromosome aberrations. We now show that application of our model to data from published reports gives good agreement between the calculated and observed numbers of clones. As our model, based on data of A-bomb survivors collected 50 years after irradiation, explains data for Chernobyl workers collected 5-6 years after the event, we conclude that clonal expansion is completed within the time needed for recovery from radiation-decreased lymphocyte counts. A recent study (Mori et al., PNAS 99; 8242, 2002) showed that not only ALL-specific translocations occurred in 1% of cord blood samples of ordinary newborns (100-fold more frequent than pediatric ALL frequency with the same translocation) but also that the translocation-bearing B (or pre-B) cells were clonally expanded to 1/1,000. We propose that ALL in A-bomb survivors was not due to induction of leukemia-specific translocations but that radiation affected a few individuals who, at the time of the bombing, had spontaneously-derived expanded levels of cells potentially leukemogenic, but not leukemia causing. [J Radiat Res 44:400 (2003)]
