Figure 6. MLN8237 shows anti-leukemic activity in vitro and in vivo.

(A) Pretreatment with MLN8237, but not AZD1152-HQPA, impaired the ability of 6133/MPL cells to induce leukemia. 6133/MPL cells were incubated with 1 µM MLN8237 or 3 µM AZD1152-HQPA. One million live cells were transplanted to mice and survival of the mice was monitored. n=6 (DMSO), n=5 (MLN8237) and n= 4 (AZD1152-HQPA). MLN vs DMSO, p=0.067; AZD vs DMSO, p=0.26. (B) Measurement of drug concentration in plasma after a single dose of MLN8237. C57Bl/6 mice were dosed orally with 15 mg/kg of MLN8237, and plasma concentrations of the drug were assessed at different time points post-treatment; n=3 animals per time point. (C–G) MLN8237 reduced tumor load of 6133/MPL cell transplanted mice. Forty-eight hr after transplantation of 6133/MPL cells, mice were fed arginine (solvent for MLN8237) or MLN8237 at 10 and 15 mg/kg by oral gavage twice a day for 10 days. MLN8237 reduced white cell count in the peripheral blood (C) and decreased spleen and liver weight of transplanted mice (D,E). MLN8237 reduced infiltration of megakaryoblasts in the liver (F) and lung (G) in transplanted mice detected by H&E staining of tissue sections. (H) MLN8237 induced polyploidization of 6133/MPL cells in vivo. Forty-eight hr after transplantation of 6133/MPL cells, mice were given arginine or 15 mg/kg MLN8237 by oral gavage twice a day for 3 days and the DNA content of the transplanted cells in bone marrow was evaluated by flow cytometry. Left, representative flow plots. Right, Bar graph of mean ± SD; ** p<0.01. n=4 animals per group. (I, J) MLN8237 induced polyploidization and inhibited proliferation of human non DS-AMKL blasts. Human CD41+ non-DS-AMKL blasts isolated from primary NSG recipients were treated with DMSO or 0.1 µM MLN8237 for 6 days. Results are representative of two independent experiments in duplicate. Error bars represent mean ± SD; * p<0.05, ** p<0.01.