Activating N-Ras mutations were found in the M14(R)5214 and M14(R)701 cell lines and play a role in resistance to FLT3 TKIs. (A) Sequence analysis of cDNA from the Molm14, M14(R)5214, and M14(R)701 cell lines. (B) Molm14 and Molm14 cells (300 000 cells/mL) transduced with the lentiviral vector, wt N-Ras or N-Ras G12V, were treated with CEP-701 for 48 hours at 37°C. Cellular activity/proliferation was determined using the MTT assay in triplicates. Error bars represent standard error of the mean (SEM).