Cells resistant to SCH66336 are also resistant to other small molecule inhibitors but not to vincristine. The viability of cells was determined after treatment for 24 hours with (A) 10 μm FTI-276, (B) 20 μM GGTI-298, (C) 5 μM STI571, or (D) 0.5 μM vincristine. The result shown is 1 of 2 independently performed experiments with similar results. The data points show the mean ± SEM of triplicate measurements.