Hit compounds induce myeloid differentiation and apoptosis. (A) May-Grunwald Giemsa staining of Kasumi-1 cells treated with DMSO, 160 nM methotrexate, or 80 nM methylprednisolone for 72 hours viewed under 1000× magnification. Both methotrexate and methylprednisolone induced visual evidence of myeloid differentiation. (B) Induction of myeloid differentiation signature in Kasumi-1 cells after 72 hours of treatment with indicated concentrations of methotrexate or methylprednisolone. Each condition was evaluated in replicates of 7 for hits and 14 for DMSO and untreated cells. (C) CD11b/CD14 cell-surface staining of Kasumi-1 cells at 72 hours. Treatment with methotrexate induced CD11b up-regulation and a small population of CD11b/CD14 double-positive cells. Methylprednisolone (160 nM) induced minimal up-regulation of CD14 and double-positive cells. (D) Annexin V/propidium iodide staining of Kasumi-1 cells after 72 hours of treatment with 40 to 160 nM methotrexate or methylprednisolone. Both compounds increased annexin V cell-surface staining in a dose-responsive manner.