Figure 5.

Effects of ON044580 on monosomy 7 MDS and chronic myelogenous leukemia (CML) patient samples. (a) Short-term exposure to ON044580 is cytotoxic to cells expressing oncogenic forms of JAK2 and ABL kinases but not to normal bone marrow cells. Ba/F3:JAK2-V617F cells, HEL cells, K562 cells, and mononuclear cells isolated from normal mouse bone marrow were treated with increasing concentrations of ON044580 for 2 hours. The cells were then washed and allowed to grow in complete medium in the absence of the compound. The data are plotted as percentage viability as compared to DMSO-treated controls. Concentration-dependent growth inhibition was observed for all three oncogenic cell lines, whereas mouse bone marrow cells subjected to identical conditions were unaffected. (b) Ex vivo treatment of monosomy 7 MDS patient bone marrow cells with ON044580 causes favorable cytogenetic changes. MDS patient bone marrow mononuclear cells were cultured in colony-supporting conditions and treated with 0.5 μM and 1.0 μM ON044580. This led to a dose-dependant decrease in the total number of monosomy 7 cells while maintaining/increasing the total number of diploid cells. (c–e) ON044580 induces apoptosis in refractory, chronic phase and blast crisis stages of CML patients. Purified blood samples from a refractory CML patient (c), a CML patient in blast crisis (d), and a chronic phase CML patient (e) were incubated with the indicated concentrations of ON044580, and one untreated sample was kept as a control. After 48 hours, the apoptosis was measured by Annexin-V/IP method. Cells accumulated in the lower right and upper right quadrants indicate the percentage of cells in the early and late stage of apoptosis, respectively.