Characterization of late-arising chromosome aberrations in human B-cell lines established from α-ray– or γ-ray–irradiated lymphocytes

To clarify the characteristics of late-arising (delayed) chromosome aberrations after irradiation in human lymphocytes, 30 B-cell lines were established from the peripheral blood from a healthy adult donor, the lymphocytes of which were exposed to α-rays or γ-rays and then used for experiments. Chromosome aberrations were serially observed at several passages by both conventional cytogenetics and fluorescence in situ hybridization analysis using subtelomere probes. These B-cell lines derived from lymphocytes with a history of radiation exposure had higher percentages of delayed chromosome aberrations, such as dicentrics, rings, endoreduplication, hyperdiploid, hyperploidy, and telomere association. Furthermore, α-ray exposure induced higher chromosome instability than γ-ray exposure, indicating that delayed chromosome aberrations were related with radiation quality. Chromosome instabilities were also observed at the subtelomere. Cell lines showing high chromosome instability had high DNA-PK activity, low expressions of Ku70, p53, and TRF1 proteins after stimulation with radiation. These results indicate that mechanisms underlying delayed chromosome aberrations might be epigenetic, and multiple factors such as defects of DNA-PK, subtelomere, and telomere might be associated.