ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: Targeted therapy is successful in some uncommon cancers, such as the tyrosine kinase inhibitors of the Bcr-Abl1 chimeric tyrosine kinase that results from reciprocal translocation between the BCR (break-point cluster region) gene on chromosome 22 and the Abelson (ABL1) gene on chromosome 9 in chronic myelogenous leukemia.