Chromosome aberrations in bone marrow cells from Japanese patients with thorotrastosis

Exposure of bone marrow cells to alpha-particle radiation causes various ty pes of chromosome abnormalities and hematological malignancies. We performe d chromosome analysis of hematopoietic stem cells from the bone marrow of 5 2 Japanese patients with thorotrastosis and 21 age-matched controls. The fr equency of cells with stable chromosome abnormalities was significantly hig her in the patients with thorotrastosis. Further studies found 14 clonal ch romosome aberrations in cells from 11 patients (21.2%); clones observed in the cells from 2 of these patients had high frequencies of chromosome abnor malities. In one case, 68 to 100% of the cells analyzed had a large partial loss in the short arm of chromosome 1 and a translocation between the shor t arms of chromosomes 2 and 3 [46,XY,1p-,t(2p+;3p-)]. The cells from the ot her patient contained a clone with partial loss of both the short and long arms of chromosome 5 (46,XX,5p-,5q-). The frequency of this clone has been constant for the last 15 years (6-24%). We also analyzed bone marrow mononu clear cells from 17 of the patients for mutations of the TP53 tumor suppres sor gene (formerly known as p53). However, no mutation was found in any of the cells, including those from the 2 patients with abnormal clones. Moreov er, repeated medical examinations showed no evidence of leukemia or myelody splasia in these patients. Our study suggests that exposure of bone marrow cells to alpha-particle radiation may induce clonal chromosomal aberrations at a high frequency. (C) 1999 by Radiation Research Society.