RNA in Patients With Chronic Myelogenous Leukemia

C HRONIC MYELOGENOUS LEUKEMIA (CML) is characterized by two major phases. The chronic phase lasts an average of 3 years and is characterized primarily by accumulation of granulocytes and their precursors in the bone marrow and peripheral blood. This is followed by the acute phase (blast crisis) in which the leukemia cells fail to differentiate and to respond to regulatory factors of myelopoiesis. In some patients there is an intermediate accelerated phase. A specific chromosomal abnormality, the Philadelphia chromosome (Ph’), is present in 90% to 95% of CML patients.2 This aberration results from a reciprocal translocation between chromosomes 9 and 22 designated t(9:22).3 Recent molecular studies implicate the abi oncogene and the bcr gene in CML. As a result of the translocation, abl is moved from chromosome 9 into the bcr gene on chromosome 22. The fused bcr-abl gene is transcribed into a large chimeric RNA which presumably initiates at the bcr promoter and is composed of bcr sequences 5’ of the translocation point on chromosome 22 and sequences ofchromosome 9 including abi, located downstream of the transbocation