Mitotic indices and proportion of binucleated cells with micronuclei are increased in RA5 and RG2 cells compared with HL60 after IR. Cells were irradiated with 2 Gy γ-IR (A-B), 6 Gy γ-IR (C-D), or ∼ 1.5 Gy α-particles (E-F) and assayed for mitotic index (A,C,E) and percent of binucleated cells with micronuclei (B,D,F). Data are mean ± SEM from 3 independent experiments. Samples were scored as indicated in “Micronucleus assay.” Two-way, repeated-measures ANOVA with Bonferroni posttests were performed to analyze significance of each treatment between HL60 and resistant cells. *P < .05. **P < .01.***P < .001.