CD123 is overexpressed by up to 95% of leukemic blasts, including LSCs in AML and a majority of B cell acute lymphoblastic leukemia (B-ALL) blasts, but is low or absent on normal hematopoietic stem cells (HSC) or cells outside the hematopoietic lineage [37–41]. This evidence concerns the gene IL3RA and acute lymphoblastic leukemia.