Effect of NONO-aspirin prodrugs on p53 phosphorylation in MDA-MB-231 cells. The cells were treated with 50 μM IPA/NO-aspirin (blue) or 75 μM DEA/NO-aspirin (green), respectively at 37 °C, and protein was collected at various time points (1–44 h). P-p53 was quantified by Western blot. Lanes 1–6 (20 μg of protein): IPA/NO-aspirin at 1, 3, 6, 10, 20, 44 h; Lanes 6–12: DEA/NO-aspirin at 1, 6, 10, 20, 30, 44 h; Lane 15: control. p-P53 protein at different time points was quantified by Western blot with respect to control, which was treated as 100%. Protein levels are normalized to the loading control HPRT.