Origin of Chronic Myelocytic Leukemia in a Precursor of Pre-B Lymphocytes

THE cause of the malignant transformation of hematopoietic cells in human chronic myelocytic leukemia is unknown. However, the demonstration of a characteristic and specific chromosomal rearrangement involving chromosomes 9 and 22,^1,2 known as the Philadelphia chromosome, has suggested a common causative factor in this disorder. In addition, studies of the Philadelphia chromosome and the X-linked enzyme glucose-6-phosphate dehydrogenase have implied that the origin of chronic myelocytic leukemia is a monoclonal stem cell.^3,4 The studies strongly suggested that, in at least some of these patients, the cellular target of malignant transformation is a progenitor with the potential for differentiation into granulocytes,.