BCR and acute lymphoblastic leukemia: In the BCP-ALL subtypes t(12;21)ETV6-RUNX1, t(9;22)BCR-ABL1, and 11q23/MLL, a fusion gene was detected by RNA-sequencing in all but one t(12;21) patient (ALL_504) and patients with the HeH subtype had the lowest frequency of fusion genes (Fig. 1b).