Pharicin B enhances the differentiation-inducing effect of ATRA in NB4 cells. (A-B) NB4 cells were incubated with 1 or 2μM pharicin B and/or 10⁻⁸M ATRA for the indicated days, and viable cells were determined by trypan-blue exclusion assay (A), and CD11b-positive cells were counted by flow cytometry (B). *P < .001 between pharicin B/ATRA- and ATRA-treated cells. (C-D) The morphology (C) and NBT staining (D) during the 3-day treatment are indicated. In panel D, the values represent means ± SD) of NBT-positive percentages of triplicate samples. All experiments were repeated 3 times.