Spectrum of point mutations in patients with imatinib mesylate resistance compared with mutations recovered from in vitro assay in the presence of imatinib mesylate. Ba/F3-p210^BCR-ABL exposed to ENU and cultured in the presence of imatinib mesylate at graded concentrations. Bars represent the frequencies of mutations that occur in patients with imatinib mesylate resistance, as summarized by Hughes et al.²⁷  Asterisks denote mutations that appeared in the screen but that have not been described clinically.