BCR-ABL1 is a fusion gene usually formed via a t(9;22) (q34;q11) translocation (Faderl et al. 1999). This translocation results in the Philadelphia chromosome. In rare cases lacking the traditional t(9;22) translocation, other translocations result in the creation of the BCR-ABL1 fusion gene. These sometimes involve multiple chromosomes.
BCR-ABL1 is present in all cases of chronic myeloid leukemia, but it is also involved in other cancers. These include pediatric B-cell acute lymphoblastic leukemia (3-5%), adult B-cell acute lymphoblastic leukemia (25-30%), acute myeloid leukemia (rare), and T-cell acute lymphoblastic leukemia (rare; De Braekeleer et al. 2011).
ABL1 kinase inhibitors have been developed as targeted therapies against BCR-ABL1 positive malignancies.