AFF1 and leukemia: As CD19+ blasts from the same leukemia (both in patients and CRISPRKMT2A::AFF1 ALL) have variable expression of CD133, we prospectively isolated CD133+ and CD133– blasts from CRISPRKMT2A::AFF1 leukemias to determine the correlation between CD133 expression and the molecular and functional characteristics of PROM1-high leukemias (supplemental Figure 2A).