Response to ATRA treatment is compromised when Pml NBs are disrupted. (A) Differentiation of BM cells from secondary recipients determined by in vitro NBT assay following treatment with DMSO (vehicle control) or ATRA (1 μM) (n ≥ 4). A minimum of 1100 cells were counted per sample using Nikon NIS Elements C software. Two-tailed unpaired Student t test analysis was performed. (B) Representative contour plots of leukemic blasts treated with DMSO (vehicle control) or ATRA (1 µM) for the myeloid differentiation markers CD11b and Gr1. (C) Survival of secondary recipients treated with ATRA (5 mg) or placebo pellets from day 7 posttransplantation (n ≥ 5). This graph represents pooled data from 3 independent experiments. The log-rank test was used. I, implantation; T, transplantation.