CHANGES OF NUCLEOLAR ORGANIZER REGIONS IN GRANULOPOIETIC PRECURSORS DURING THE COURSE OF CHRONIC MYELOID-LEUKEMIA

The aim of the present study was to analyze the nucleolar organizer re gion (AgNOR) pattern of granulopoietic precursors in chronic myeloid l eukemia (CML) at diagnosis and during the course of the disease. Clust ers of AgNORs and isolated dots were counted separately in 24 cases of CML at diagnosis, in 19 cases during the relapse of the chronic phase after treatment, and in 16 cases of blast crisis. For comparison, 20 cases of normal bone marrow were studied. Each cell type had its own c haracteristic AgNOR pattern, as has been described for normal bone mar row. There was no significant difference in the number of AgNORs betwe en cells in the peripheral blood and bone marrow. Compared with normal granulopoiesis, myeloblasts in CML at diagnosis had lower numbers of clusters, which decreased further during relapse of chronic phase and in blast crisis. Promyelocytes and myelocytes showed significantly few er dots. The number of AgNOR clusters correlates inversely with the du ration of the cell cycle. Therefore, these findings are consistent wit h the progressive loss in proliferative activity of immature precursor s described during the course of CML. As the number of dots indicates cellular maturation, their lower number in promyelocytes and myelocyte s in CML favors the concept of a discordant maturation process describ ed in this desease. The separate counting of clusters and dots provide s a useful, simple, and cheap method of describing cytokinetic changes during the course of this myeloproliferative disorder.