ATRA and FK228 induce p21 mRNA in NB4 cells. Induction of p21 mRNA expression in NB4 cells treated with ATRA (1.0 μM) and/or FK228 (3.0 nM) for 24 hours analyzed by TaqMan RT-PCR analysis. The p21 mRNA expression in each sample was normalized to B2M mRNA expression. Control NB4 cells were used as the calibrator (p21 mRNA level in control NB4 cells = 1). Graphs show the mean ± SD of results from more than 3 independent experiments. A statistically significant difference was determined by ANOVA and Fisher post hoc tests (^**P < .01).