PECAM1 and acute myeloid leukemia: Consistent with a decrease in CD31+Sca-1high vessels (i.e., arterioles) (Fig. 1a, g), we observed increased vessel permeability in the MllPTD/WT/Flt3ITD/ITD AML mouse (TRITC-150 kDa dextran, red) and FLT3-ITD+ PDX (FITC-150 kDa dextran, green) (Additional file 1: Fig. S5a, b).