Caspase-independent cell death without generation of reactive oxygen species in irradiated MOLT-4 human leukemia cells.

Cellular Immunology(2009)

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To improve our understanding of ionizing radiation effects on immune cells, we investigated steps leading to radiation-induced cell death in MOLT-4, a thymus-derived human leukemia cell. After exposure of MOLT-4 cells to 4Gy of X-rays, irradiated cells sequentially showed increase in intracellular reactive oxygen species (ROS), decrease in mitochondrial membrane potential, and eventually apoptotic cell death. In the presence of the caspase inhibitor z-VAD-fmk, irradiated cells exhibited necrotic characteristics such as mitochondrial swelling instead of apoptosis. ROS generation was not detected during this necrotic cell death process. These results indicate that radiation-induced apoptosis in MOLT-4 cells requires elevation of intracellular ROS as well as activation of a series of caspases, whereas the cryptic necrosis program—which is independent of intracellular ROS generation and caspase activation—is activated when the apoptosis pathway is blocked.
Apoptosis,Caspase,Immune cells,Ionizing radiation,Necrosis,Reactive oxygen species
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