A. REH VECT, REH CDH5, and REH PECAM1 were labeled with CellTracker green dye then incubated HBMEnd for the indicated times. B and C. Nalm-27 and SUP-B15 cells were labeled with CellTracker green dye then treated with neutralizing antibodies against VE-cadherin (B), PECAM-1 (C), or matched isotype control antibodies for 15 min. Following this pretreatment, Nalm-27 and SUP-B15 cells were incubated with HBMEnd for 15 min. Following incubation, non-adherent leukemia cells were removed and the remaining adherent population was recovered by trypsinization. The number of adherent leukemic cells was determined using flow cytometry by collecting the number of fluorescently labeled events that occurred during 30 s of high flow rate. Data are expressed as mean number of adherent cells + standard error of the mean (SEM, N=3) and are representative of at least three independent experiments. *p<0.05