CAMAL: evidence for an inhibitory role in normal granulopoiesis.

Maintenance of normal granulopoiesis requires complex interactions between positive (stimulatory) and negative (inhibitory) regulatory molecules, the cells that produce them and their targets. In myeloid leukemia these signals continue to operate but in an obviously unbalanced fashion, allowing the emergence and eventual dominance of the malignant clone. In this study, a common antigen in myeloid leukemia (CAMAL) has been shown to bind to normal leukocyte membranes. At similar concentrations (between 10 and 15 micrograms/ml), leukemia-derived CAMAL caused profound inhibition of normal colony growth in the myeloid progenitor cell assay but had no inhibitory effect on granulocyte-macrophage colony-forming unit (CFU-GM) growth from myeloid leukemia patients in active disease states. These preliminary results indicated the myeloid leukemia cells possessed apparent differences in responsiveness to CAMAL-mediated regulation compared to normal cells. Lack of or decreased responsiveness to inhibition by leukemia-derived CAMAL may facilitate dominance of the malignant clone over normal cells.