CAR T cells against PDX cells in vitro and long-lasting leukemia control in vivo. (A) Untransduced T cells and CAR T cells were cocultured with CD19⁺ ALL-265 PDX cells at an E:T ratio of 0.2:1. Cytotoxicity was investigated 48 hours later (n = 3). (B) Untransduced T cells, _RV19BB_TCR⁺, _RV19BB_CRTCR⁺, and _RV19BB_CRTRBC⁻ CARs were cocultured with CD19⁺ ALL-265 PDX cells at an E:T ratio of 1:1. Proliferation was analyzed after 72 hours by flow cytometry (n = 3). A 2-tailed paired Student t test or 1-way ANOVA was performed to determine statistical significance. (C) NSG mice were injected with ALL-265 PDX cells, followed by IV T-cell injection (2 × 10⁷ cells) of _RV19BB_CRTCR⁺ CAR T cells or _RV19BB_CRTRBC⁻ CAR T cells or PBS 3 days after. (D-E) At indicated time points after T-cell injection, PDX leukemia burden was monitored by BLI. (D) Bioluminescence pictures and (E) quantification of leukemia burden are shown for mice suffering from ALL-265 PDX-cell–induced leukemia and treated with PBS (n = 3), _RV19BB_CRTCR⁺ (n = 5), or _RV19BB_CRTRBC⁻ (n = 4; see also supplemental figures). (F) Kaplan-Meier analysis of survival of mice treated with PDX cells. A 2-tailed paired Student t test was performed to determine statistical significance.