NADPH Oxidases Inhibitors Induce Oxidative Stress and Apoptosis in Acute Myeloid Leukemia Cells

Regulation of redox metabolism is crucial in leukemogenesis and reactive oxygen species (ROS) are recognized as key players in cell signaling. Low ROS level is associated with quiescence whereas higher level promotes proliferation and ROS homeostasis relies on a tightly regulated balance between the prooxidant and antioxidant systems. Although the antioxidant system is extensively studied in acute myeloid leukemia (AML), the prooxidant system remains to be investigated.

NADPH oxidases (NOX) are well known to generate ROS, and yet, little is known about their activity in AML. Therefore, we characterized the seven NOX complexes (NOX1, NOX2, NOX3, NOX4, NOX5, DUOX1 and DUOX2) in 25 human myeloid leukemia cell lines (M0 to M7 FAB subtypes) and the effects of two NOX inhibitors (diphenyleneiodonium -DPI- and VAS3947) by qRT-PCR, western-blotting, enzymatic assays and metabolic analyses (Seahorse XF96 analyzer).

NOX transcriptional and protein profiles are variable with higher expression of NOX2 among monocytic/monoblastic leukemia cells. Nevertheless, an equivalent level of enzymatic activity was observed across AML all FAB subtypes, suggesting either different antioxidant capacities or compensation by other NOX. Although DPI and VAS3947, two NOX inhibitors, efficiently blocked this activity and reduced cell proliferation, they unexpectedly triggered a strong oxidative stress and apoptosis by increasing mitochondrial superoxide and cytoplasmic ROS production, respectively.

Our data introduce NOX as potential therapeutic targets and suggest an in-depth investigation about the mode of actions of available inhibitors to consider therapeutic use.