PBX1 and leukemia: T cells expressing a CAR containing an anti-mouse CD19 scFv incorporating a FLAG sequence and a CD28 costimulatory domain fused to mouse CD3zeta, followed by a 2A sequence and a truncated EGFR 13 (Figure S1A) were used to target a murine leukemia driven by the E2A-PBX1 fusion protein (E2A-PBX)14, 15, 16.