ATRA-dependent loss of cellular S100A10 corresponds to decreased cellular plasminogen binding, plasmin generation, and invasive capability of APL cells. NB4 cells were treated with ATRA for the indicated times then incubated with uPA (50nM) for 10 minutes at room temperature. Cells were washed and incubated with plasminogen (0.5μM) followed by the addition of the plasmin substrate, S2251. The rate of plasmin generation was measured at 405 nm. Statistical analysis was performed by Student t test (***P < .001), and data are expressed as Δ405 nm/s ± SD of 3 independent experiments (A). ATRA-treated NB4 cells were incubated with 200nM FITC plasminogen for 1 hour at 4°C, and plasminogen binding was measured by FACS. Statistical analysis was performed by one-way ANOVA with Tukey multiple comparisons, and data are expressed as the percentage of specific binding ± SD of 3 independent experiments (B). ATRA-treated NB4 cells (1 × 10⁵ cells) were added to the upper chamber of Matrigel-coated (C) or fibrin-coated (D) chambers in the absence of FBS that also contained plasminogen (0.5μM). The lower chamber contained FBS as chemoattractant. Data are expressed as the mean number of cells per 40× field ± SD of 3 independent experiments. Statistical analysis was performed by one-way ANOVA (with Tukey multiple comparisons) in comparison to untreated NB4 cells (NT; ***P < .001).