Evans, H. H., Horng, M-F., Evans, T. E., Jordan, R. and Schwartz, J. L. Genotoxic Effects of High-Energy Iron Particles in Human Lymphoblasts Differing in Radiation Sensitivity. Radiat. Res. 156, 186–194 (2001).
The effects of 56Fe particles and 137Cs γ radiation were compared in TK6 and WTK1 human lymphoblasts, two related cell lines which differ in TP53 status and in the ability to rejoin DNA double-strand breaks. Both cell lines were more sensitive to the cytotoxic and clastogenic effects of 56Fe particles than to those of γ rays. However, the mutagenicity of 56Fe particles and γ rays at the TK locus was the same per unit dose and was higher for γ rays than for 56Fe particles at isotoxic doses. The respective RBEs for TK6 and WTK1 cells were 1.5 and 1.9 for cytotoxicity and 2.5 and 1.9 for clastogenicity, but only 1 for mutagenicity. The results indicate that complex lesions induced by 56Fe particles are repaired less efficiently than γ-ray-induced lesions, leading to fewer colony-forming cells, a slightly higher proportion of aberrant cells at the first division, and a lower frequency of viable mutants at isotoxic doses. WTK1 cells (mutant TP53) were more resistant to the cytotoxic effects of both γ rays and 56Fe particles, but showed greater cytogenetic and mutagenic damage than TK6 cells (TP53 ). A deficiency in the number of damaged TK6 cells (a) reaching the first mitosis after exposure and (b) forming viable mutants can explain these results.
