Figure 1.
Primary AML blasts from 88 patients were isolated at diagnosis and treated in vitro with (A) voreloxin and Ara-C for 48 h and LD50 values were calculated (the mean LD50 for voreloxin was 2.3 μM (±1.9) and for Ara-C was 4.90 μM (±5.0).) (B) Mean LD50 values for voreloxin, Ara-C and etoposide in myeloid cell lines NB4 and HL-60 following 48 h of treatment with each drug. The effects of each drug were tested using an MTS assay. Annexin V and propidium iodide (PI) positivity were measured by flow cytometry to determine whether (C) voreloxin or (D) etoposide resulted in induction of apoptosis following 48 h treatment of myeloid cell lines NB4 and HL-60 with a range of concentrations. Both voreloxin and etoposide resulted in significant increases in the proportion of cells undergoing apoptosis identified by positivity for annexin V and PI staining across all the concentrations tested. The LD50 for voreloxin in the cell lines was 0.203 μM for NB4 cells and 0.061 μM for HL-60 cells. The LD50 of etoposide was 0.78 μM in NB4 cells and 4.23 μM for HL-60 cells. Activation of caspase-3 was measured by flow cytometry to confirm the pathway of apoptosis initiation in NB4 and HL-60 cells treated for 48 h with (E) voreloxin and (F) etoposide. Both voreloxin and etoposide generated significant activation of caspase-3 in the cell lines at all concentrations tested. Significant differences (P<0.05) with respect to the untreated control samples are indicated in each case by *.