ATRA and GFs modulate differentiation and cell growth through MAP kinase pathways. (A) CD11b expression was detected by flow cytometry 3 days after incubation with the indicated agents. Values represent mean (numbers above bars) ± SD of 2 independent experiments done in duplicates. (B) Cells were counted 5 days after incubation with the indicated agents. Data represent mean ± SD of quadruplicate samples from one experiment, which has been repeated with a similar result. The statistical significance of differences between control and treated samples is indicated by asterisks, and between treated samples by plus symbols. ^***/+++P < .001, ^**/++P < .01, ^*/+P < .05. (C) Induction of apoptosis was measured by FACS after treatment of U-937 cells with ATRA and/or GFs or positive control Campthotecin (CAMPTO) for the indicated time points. Percentage of early (Annexin+, TOPRO-) and late (Annexin+, TOPRO+) apoptosis was estimated in 2 independent experiments, one of which is presented here.