Effects of activated Notch1 on the differentiation of HL-60 cells. Two-color flow cytometric analysis for GFP and CD11b on transduced HL-60 cells in the absence (day 0) and in the presence of 1 μm ATRA (A and C) or 4 nm TPA (B and D). At each time point, cells were harvested, washed, and labeled with anti-CD11b PE-conjugated MoAb and analyzed by FACS. Contour plots (A and B) represent fluorescence intensity for CD11b on the x-axis and for GFP on the y-axis. Values in the line graphics (C and D) represent the mean percentage of CD11b-expressing cells in the GFP-positive population in four (C) and two (D) independent experiments. Bars represent standard error.