How slightly different BCR-ABL1 isoforms (p190BCR-ABL1 vs p210BCR-ABL1) can trigger such diverse diseases (CML has an indolent course and TKI therapy results in stable remissions in the great majority of cases; Ph + ALL is much more aggressive, responses to TKIs are not durable and prognosis is relatively poor) has long been under investigation. Here, ABL1 is linked to acute lymphoblastic leukemia.