Fig. 3. Flow cytometry histograms of cell surface antigen expression by AML. A, U937 cells were incubated in the presence of GM-CSF (200 units/ml) and bryostatin-1 (10-8 M), hydroxyurea (100 µg/ml), or phenylbutyrate (1.5 mM) for 120 h and analyzed for CD11b expression by flow cytometry. B, AML blasts from patient number 2 were incubated with bryostatin-1 (10-8 M) and GM-CSF (200 units/ml) for 120 h and then evaluated for CD15 expression. Experimental groups are depicted by solid lines, whereas dotted lines represent untreated control cells. Cell numbers of all groups remained constant throughout the 5-day incubation.