NGFR and acute lymphoblastic leukemia: PDX ALL cells were lentivirally transduced to express a luciferase for in vivo imaging (Terziyska et al., 2012), an artificial antigen (truncated nerve growth factor receptor [NGFR]) for magneto-activated cell sorting (Fehse et al., 1997) and a red fluorochrome for cell sorting by flow cytometry (Figures S1A and S1B).