WIN55212-2-mediated inhibition of differentiation of human monocytic U937 cells is CB1- and CB2-receptor-dependent. Differentiation of U937 cells was induced by 25 nM PMA in the presence of 3 μM or 5 μM WIN55212-2 (figure 2a or figure 2b, respectively) with or without co-incubation with 2 μM AM251 (CB1-inhibition) and/or 2 μM AM630 (CB2-inhibition). Adherent cells were separated and quantified after different time points up to 72 h by FACS analysis. Percentage of control group at time point zero is shown. Data are shown as mean +/- SD, n = 8; *p < 0.05, **p < 0.01, ***p < 0.001 in comparison with the PMA/WIN55212-2 -treated group without CB1- or CB2-inhibition.