Sublethal p53 stabilization modulates DR expression and increases sensitivity to CART19. (A-B) mRNA levels (A) and MFI (B) of Fas (CD95), DR5 (TNFRSF10B), and/or CD19 (protein only) in TP53^WT and TP53^Mut Nalm6 and RCH-ACV cell models with or without p53 stabilization using the mouse double minute 2 homolog (MDM2) inhibitor idasanutlin (50 nM) for 16 hours, assessed by real-time qPCR and flow cytometry, respectively. Each data point represents a mean (± SD) of 3 biological replicates with 2 in panel A or 1 technical replicate(s) each in panel B and is normalized to the mean of the TP53^WT control condition in panel A. (C-D) mRNA levels (C) and MFI (D) of Fas (CD95) and DR5 (TNFRSF10B) in 4 TP53^WT and 2 TP53^Mut PDXs with or without p53 stabilization using the MDM2 inhibitor idasanutlin (50 nM) for 16 hours, assessed by real-time qPCR and flow cytometry, respectively. Each data point represents a mean, per PDX sample, of biological triplicates with 2 in panel C or 1 technical replicate(s) each in panel D and is normalized to the mean of the TP53^WT control condition of a biological replicate. (E) Nalm6 and RCH-ACV TP53^WT and TP53^Mut cells were pretreated with the MDM2 inhibitor idasanutlin for 16 hours, followed by a washout, and subsequent CART19 treatment for 16 hours at an effector-to-target ratio of 1:40. CART19-mediated killing was determined by flow cytometric assessment of cells positive for 7-aminoactinomycin D (7-AAD), normalized for the target-only control. Each data point represents a mean of 3 (Nalm6) or 4 (RCH-ACV) biological T-cell donors and 3 technological replicates each. In panels A-E, indicated differences between control and MDM2-inhibited conditions were evaluated for significance using paired 2-tailed t tests. ns, nonsignificant; ∗, 0.01 ≤ P-value < 0.05; ∗∗, 0.001 ≤ P-value < 0.01; ∗∗∗, 0.0001 ≤ P-value < 0.001; ∗∗∗∗, P-value < 0.0001.