NOS3 and acute myeloid leukemia: Interestingly, we found among the common highest upregulated genes in ECs upon AML engraftment Nox4, a NAPDH oxidase expressed in the vasculature and involved in the response to hypoxia via production of reactive oxygen species (ROS), activation of nitric oxide synthase 3 (NOS3), and release of nitric oxide (NO) (Craige et al., 2011) (Figure 4C).