Gefitinib induces maturation-associated myeloid cell surface markers. Fluorescence-activated cell sorting analysis was performed with FITC-labeled antibodies for CD14 and CD11b. AML cell lines were incubated for 5 days before analysis with DMSO vehicle or with gefitinib at a dose optimized for morphologic changes: HL-60 (10 μM), Kasumi-1 (5 μM), and U937 (7.5 μM). Viable cells were gated based on forward and side scatter patterns and fluorescence was determined. Shaded in gray are the DMSO-treated controls and outlined in black are the gefitinib-treated cells.