p21 is highly up-regulated in L428^tetPU.1 cells after PU.1 induction. (A) Heatmap of DNA microarray analysis comparing the gene expression profiles of L428^tetPU.1 cells after PU.1 induction at days 0, 1, and 3. p21 (CDKN1A) mRNA was highly up-regulated after PU.1 induction. (B) p21 mRNA was up-regulated in both L428^tetPU.1 and KM-H2^tetPU.1 cells after PU.1 induction. Real-time PCR was performed 1 and 3 days after PU.1 induction. (C) p21 protein was up-regulated in L428^tetPU.1 but not in KM-H2^tetPU.1 cells after PU.1 induction. Western blot for p21, PU.1, and actin was performed 1 and 3 days after PU.1 induction.