Abnormalities in the erythroid progenitor compartments in patients with chronic myelogenous leukemia (CML).

Peripheral blood and bone marrow specimens from 6 patients with Ph1-positive CML were evaluated for their content of erythropoietic and granulopoietic colony-forming progenitor cells. Specimens obtained from untreated patients showed marked increases in all compartments the most dramatic of which were for CFU-E and circulating CFU-C. This increased cell flow down the early stages of the red cell pathway in CML suggests that heightened proliferation and differentiation of primitive hemopoietic cells may be a more general phenomenon than previously suspected in this disease. In 5 of 6 patients, abnormal erythroid progenitors capable of proliferation and differentiation into hemoglobinized erythroblasts in cultures containing less than 0.002 units of erythropoietin/ml were regularly detected. In the 6th patient abnormal growth was not seen in cultures of the initial marrow obtained but was detected in cultures set up with peripheral blood taken 7 months later. The unexplained amplification of the erythropoietic compartment and the ability of some of these cells to mature in vitro in the virtual absence of erythropoietin is at variance with the anemia characteristic of untreated patients. This suggests the possibility of a major differentiation block at the level of CFU-E. Further studies of the properties of erythroid progenitors in these patients should help to provide new insights into the pathogenesis of CML and may provide useful markers for monitoring engrafted cell function after autotransplantation of patients in blast crisis.