UCART123 cells were readily detectable in several of the mice that died from CD123 negative relapsed tumor (Sample 13, Sample 16 from 1 × 106 UCART123 group, and sample 5 from 10 × 106 UCART123 group, Supplementary Table 1), consistent with relapse due to the loss of the target and not because of lack of persistence of UCART123 cells. Here, IL3RA is linked to neoplasm.