Cells expressing BCR/ABL(Y177F) mutant displayed reduced ROS and mutagenic activity. Freshly transformed p190BCR/ABL wild-type (wt) and p190BCR/ABL(Y177F) cells were cultured continuously for 8 weeks in the presence of IL-3. (A) ROS was measured by fluorescence. (B) The percentage of IM-resistant cells (% of IM-resistant cells) was determined by clonogenic assay performed in the absence of IL-3 and the presence or absence of IM. Mutation rate in BCR/ABL kinase is shown. ^*P = .002 compared with wild-type group.