A reciprocal translocation between chromosomes 22 and 9 produces the Philadelphia chromosome, which is often found in patients with chronic myelogenous leukemia. The chromosome 22 breakpoint for this translocation is located within the BCR gene. The translocation produces a fusion protein which is encoded by sequence from both BCR and ABL, the gene at the chromosome 9 breakpoint. BCR-ABL and its mutants can promote and maintain the malignant behavior of the cancer cells. The identification of BCR-ABL as a driver gene has led to the rapid development of anticancer therapeutics agents, including Imatinib, Dasatinib, Ponatinib and Nilotinib.