ABL1 and acute lymphoblastic leukemia: In adults, 30–40% of patients with precursor-B ALL express the BCR-ABL oncogene as the result of the Philadelphia-translocation t(9;22)(q34;q11) defining a very high-risk profile.1, 2 The BCR-ABL oncoprotein is a constitutively active tyrosine kinase involved in hematopoietic cell transformation.