Transcriptional activities of APL blasts displaying different sensitivities to ATRA in vitro. Within the subset of SAGE tags that matched genes with described functions and that were registered according to the HuGO nomenclature, the abundances of SAGE tags from a proliferative NB4 library (UnT) were compared with their respective levels in both ATRA-treated NB4 (Diff) and polymorpho-nuclear neutrophil (PMN) libraries. Variations (P values) were calculated between proliferative NB4 cells and cells induced to differentiate by a 48-hour exposure to 1 μM ATRA (Diff/UnT). The proliferative NB4 library was also compared with the granulocytes (PMN/UnT). By mining NB4 gene expression data relative to the granulocytic phenotype, 48 underexpressed genes (A) were separated from 35 up-regulated genes (B). A cluster of 75 retinoid-induced genes that were barely detectable in the granulocyte but clearly induced by retinoid during NB4 cell differentiation (C). Heterogeneity at day 3 in the differentiation of 3 APL blasts (NBt test) exerting distinct sensitivities to ATRA (D). Data from the Relative Quantity gene expression (RQ) analysis. Transcriptional modulation (Log₁₀ RQ) was calculated for blasts treated for 3 days with ATRA (0.1 μM) in comparison with an untreated control. Clusters of retinoid-responsive genes (E), granulocytic markers (F), chromatin remodelers, transcription factors, and coregulators (G). Genes involved in retinoic acid metabolism and the inflammatory response to maturation (H).