Phosphorylation of wild-type p53 is induced by DNA damage in AML. (A) Idarubicin treatment of AML blasts led to rapid accumulation of numerous full-length p53 isoforms of high acidity. The blue line indicates the resting pI of the most acidic full-length p53 isoform for this representative AML patient sample (AML-P18). (B) The change in pI of full-length p53 following idarubicin treatment was measured in AML blast samples from 6 patients. The acidic movement of full-length p53 relative to that in untreated cells was statistically significant (n = 6). Similar results were obtained for normal PBMCs. (C) Phosphorylation of p53 at 5 residues (serines 15, 20, 37, 46, and 392) and total per-cell level of p53 were detected by phospho-specific flow cytometry in AML blast samples from 6 patients. Phosphorylation and accumulation of p53 in AML blast samples following DNA damage was measured as the log10-fold increase in MFI at 4 hours following idarubicin treatment, as compared to cells treated with idarubicin and fixed immediately (0 hours). Black indicates a comparable MFI was observed at 4 hours and 0 hours.
