Gefitinib induces whole-genome expression modulation consistent with neutrophil maturation. Gene expression profiling was done in triplicate 6 hours and 24 hours after treatment with either 10 μM gefitinib or 0.02% DMSO in HL-60 cells. These patterns were compared with expression profiles distinguishing primary patient AML cells from normal human neutrophils. Using the signal-to-noise (SNR) metric, the genes distinguishing the 9 primary AML samples from the 3 normal neutrophil samples (Neut) were identified and then reordered according to their degree of regulation by gefitinib in HL-60 cells. The top 25 genes in each direction are shown. Expression levels greater than the mean are shown in red; those less than the mean are shown in blue.