Deferasirox (DFX) was recently found to have anti-leukemia effect both in vitro and in vivo. DFX can also potently inhibit the generation of intracellular reactive oxygen species (ROS). On the other hand, the generation of ROS by Doxorubicin (DOX) is critical for the cytotoxicity on both leukemia and normal heart cells. It is not known whether combining DFX and DOX will have synergistic or antagonizing effect on leukemic cells. Similarly, it is also unknown whether adding DFX to DOX will have protective effect on normal heart cell.
Cells of human acute myeloid leukemia (AML) cell line THP1, mice AML cell line WEHI3, and rat normal heart cell line H9C2 were treated with Doxorubicin 5microM for various duration in the presence of absence of DFX pretreatment (100microM for 10 minutes). Intracellular ROS generation was measured by the detection of 2,7-dichlorodihydrofluorescein (DCF) fluorescence intensity using flow cytometry. Apoptosis was determined by Annexin V-Propidium Iodide staining using flow cytometry. Cytotoxicity was determined by Trypan blue exclusion assay.
Although intracellular ROS was reduced, DFX alone induced apoptosis of THP1 (from 3% to 18%) and WEHI3 (from 31% to 49%) AML cells. DOX-induced ROS production was also significantly reduced when THP1, WEHI3, and H9C2 cells were pretreated with DFX (Figure 1a, 1b, 1c respectively). However, the DOX-induced apoptosis of THP1 and WEHI3 AML cells were not antagonized by DFX (Figure 2a). 24 hours after exposure to this physiological dose DOX, all the WEHI3 cells died in both DFX treated or untreated group (figure 2b). More importantly, DFX-pretreated H9C2 heart cells had fewer cell death (3.7%) after exposure to DOX (5microM for 24 hours) compared to non-DFX pretreated cells (8.5%).
DFX alone induced apoptosis in two different AML cell lines. DFX also markedly reduced the ROS generation due to DOX treatment. However, DFX did not negatively influence the pro-apoptotic and cytotoxic effect of DOX on these AML cell lines. Interestingly, DFX also markedly reduced the DOX-induced ROS generation and DOX-induced cell death in normal rat heart cell, which might have protective effect on DOX-related cardiomyopathy. We are now using Balb/c-WEHI3 AML mice model to test whether DFX can protect cardiomyocytes from DOX-related damage while maintain the cytotoxic effect of DOX on AML cells.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.