ATRA induces differentiation in EVI-1–positive AML. (A) Flow cytometric analysis of CD11b expression in PML-RARA mutated (upper) and EVI-1–positive (lower) AML cases incubated with or without ATRA for 7 days. (B) Quantification of CD11b expression in 13 EVI-1–positive AML cases (red lines, responders; blue lines, nonresponders) and 7 EVI-1–negative AML cases (black lines). (C) Morphologic examination (×10 0.25 objective) of cells from an EVI-1–positive AML case (upper) and an EVI-1–negative AML case (lower) before and after treatment with ATRA for 14 days. (D) Quantification (by flow cytometry) of cell viability (number of cells per number of beads) in AML cases incubated with or without ATRA for 7 days. Relative number of cells in EVI-1–positive AML cases (left: red lines, responders; blue lines, nonresponders), in EVI-1–negative cases (right, black lines) and in a PML-RARA–mutated AML case (right, purple line). (E) Number of myeloid blasts (CD45^dim/CD33⁺) and lymphocytes (CD45^high/SSC^low) relative to the number of measured beads in EVI-1–positive AML cases that showed a reduced number of total cells upon ATRA incubation (responders, D, left, 5/13 cases). Incubation of AML3 with 0.1 µM ATRA was not done in this experiment. (F) Flow cytometric analysis of AML cells treated with ATRA for 7 days and labeled with annexin-V and 7-AAD. Shown is the number of annexin-V–positive cells relative to the number of beads.