Evans, H. H., Horng, M-F., Ricanati, M., Diaz-Insua, M., Jordan, R. and Schwartz, J. L. Induction of Genomic Instability in TK6 Human Lymphoblasts Exposed to 137Cs γ Radiation: Comparison to the Induction by Exposure to Accelerated 56Fe Particles. Radiat. Res. 159, 737–747 (2003).
The induction of genomic instability in TK6 human lymphoblasts by exposure to 137Cs γ radiation was investigated by measuring the frequency and characteristics of unstable clones isolated approximately 36 generations after exposure. Clones surviving irradiation and control clones were analyzed for 17 characteristics including chromosomal aberrations, growth defects, alterations in response to a second irradiation, and mutant frequencies at the thymidine kinase and Na /K ATPase loci. Putative unstable clones were defined as those that exhibited a significant alteration in one or more characteristics compared to the controls. The frequency and characteristics of the unstable clones were compared in clones exposed to 137Cs γ rays or 56Fe particles. The majority of the unstable clones isolated after exposure to either γ rays or 56Fe particles exhibited chromosomal instability. Alterations in growth characteristics, radiation response and mutant frequencies occurred much less often than cytogenetic alterations in these unstable clones. The frequency and complexity of the unstable clones were greater after exposure to 56Fe particles than to γ rays. Unstable clones that survived 36 generations after exposure to γ rays exhibited increases in the incidence of dicentric chromosomes but not of chromatid breaks, whereas unstable clones that survived 36 generations after exposure to 56Fe particles exhibited increases in both chromatid and chromosome aberrations.