STI571-resistant cells remain sensitive to SCH66336.

Parental (A) and STI571-resistant Baf/BCR-ABL cells (B, C) were seeded at 5 × 10⁴ cells/mL in cytokine-free RPMI + 10% inactivated fetal bovine serum in the presence of DMSO (control), SCH66336 (FTI), or STI571 (STI). BaF/BCR-ABL-r and BaF/BCR-ABL T315I are resistant to STI571 because of the amplification and mutation of BCR-ABL, respectively. Viable cells were assessed at daily intervals by dye exclusion, and results are representative of at least 3 experiments. (D) Hematopoietic progenitor cells were derived from STI571-naive patients (white bars, n = 3) or from patients clinically resistant to STI571 (gray bars, n = 5) and were grown in methylcellulose containing the indicated concentration of SCH66336 or STI571. Numbers are normalized to control (DMSO) and are presented as means ± SD of duplicate plates.