WHICH PROGENITOR IS THE TARGET-CELL IN THE DEVELOPMENT OF ACUTE PROMYELOCYTIC LEUKEMIA

Acute promyelocytic leukemia (APL) is characterized by the t(15;17) wh ich involves the PML gene and the retinoic acid receptor alpha (RAR al pha) gene, and the subsequent PML/RAR alpha fusion gene is a key event in the leukemogenesis of APL. We found that the PML/RAR alpha fusion gene was expressed in both granulocytic/macrophage and erythroid colon ies in a few patients with APL. In some instances of acute myelogenous leukemia (AML), erythrocytes or platelets also expressed the glucose- 6-phosphate dehydrogenase (G-6-PD) isoenzymes which were detected in t he leukemic cells. Some APL cells show basophilic and monocytoid diffe rentiation and these findings suggest that the leukemic precursor of A PL is derived from a more primitive cell stage than the promyelocyte. The precursor cells appear to be derived from heterogeneous levels.