UNC1999 prolongs survival of MLL-AF9–induced murine leukemia models in vivo. (A) Kaplan-Meier curve showing leukemia kinetics after transplantation of MLL-AF9–induced primary murine leukemia into syngeneic mice. Starting from day 7 posttransplantation, mice received oral administration of either vehicle (blue) or 50 mg/kg UNC1999 (red) twice per day. Black lines (top) represent nontransplanted normal mice treated with vehicle or UNC1999. Cohort size, 6 to 7 mice. (B) Typical Wright-Giemsa staining images of the peripheral blood smears prepared from the vehicle- (top) and UNC1999-treated (bottom) leukemia mice 25 days posttransplantation. (C-E) Summary of counts of the WBCs (C), neutrophils (D), and RBCs (E) in the peripheral blood of vehicle- (white) or UNC1999-treated (black) leukemia mice at the indicated date posttransplantation. *P < .05; **P < .01; ***P < .001. (F) Summary of H3K27me3 levels in cells isolated from bone marrow or spleen of vehicle- (LV) and UNC1999-treated (LT) leukemia mice as quantified by flow cytometry. *P < .05; **P < .01. (G) Fold-change in p16Ink4a and p19Arf gene expression in cells isolated from bone marrow or spleen of the UNC1999-treated (black) leukemia mice in comparison with vehicle-treated (white). *P < .05; **P < .01. (H-I) Summary of cell-cycle status of cells isolated from bone marrow (H) or spleen (I) of vehicle- (white) and UNC1999-treated (black) leukemia mice 25 days posttransplantation. *P < .05; **P < .01. (J) Flow cytometry (performed 25 days posttransplantation) detects leukemia cells (labeled by bicistronic GFP expression in x-axis) and their c-Kit expression (y-axis) in the bone marrow or spleen after treating mice with either vehicle or 50 mg/kg UNC1999. (K) Comparison of sizes of lymph nodes isolated from the MLL-AF9–induced leukemia mice after treatment with either vehicle or 50 mg/kg UNC1999. BM, bone marrow; GFP, green fluorescent protein; LT, UNC1999-treated leukemia mice; LV, vehicle-treated leukemia mice; RBC, red blood cell; SP, spleen.