BCR and acute lymphoblastic leukemia: The Philadelphia chromosome (Ph), the result of a balanced translocation between chromosomes 9 and 22, leads to the constitutively active breakpoint cluster region, Abelson (BCR–ABL) tyrosine kinase, which is critical for the pathogenesis of both chronic myeloid leukemia (CML) and Ph-positive acute lymphoblastic leukemia (Ph+ALL) [1–3].