As NO is the major mediator of vascular permeability in both physiological and several pathological conditions (Aramoto et al., 2004, Fukumura et al., 2001, Fukumura et al., 2006, Mayhan, 1999), we investigated whether the AML-derived upregulation of Nox4 in ECs influenced NO production in the BM vascular niche. Here, NOX4 is linked to acute myeloid leukemia.