XDH and myeloid leukemia: Many metabolic pathways contributing to ROS production such as xanthine oxidoreductase (XOR), uncoupled nitric oxide (NO) synthase (NOS), cytochrome P450 mono-oxygenase (CYP), cyclo-oxygenase (COX) and NADPH oxidase (NOX) activities are altered in myeloid leukemia (Figure 1) [16,38,39].