miRNA profiles of NB4 cell line upon ATRA treatment. (A) Morphology of May-Grünwald-Giemsa (MGG)–stained NB4 cells treated or not with ATRA (1 μM) for 4 days. Maturation was monitored by the Nitroblue Tetrazolium (NBT) dye reduction assay and the percentage of NBT-positive cells obtained at day 4 of treatment is indicated (bottom left). (B-D) NB4 cells were treated with 1 μM ATRA for 16 hours. (B) RT-qPCR analysis of RARB mRNA expression in NB4 cells upon ATRA treatment. Results are indicated as fold change, 1 being the cycle threshold (Ct) obtained in the absence of treatment. (C) Table of miRNAs modulated by ATRA. See “Methods.” (D) miRNA-specific RT-qPCRs performed in untreated (black histograms) and ATRA-treated NB4 cells (gray histograms). The asterisk (*) indicates an absence of amplification. Results are indicated as fold change, 1 being the value obtained in the absence of treatment.