The effect of low dose ARA-C on in-vitro haemopoiesis of marrow cells from myelodysplastic patients.

The effect of low dose (10(-12)-10(-7) M) ARA-C on differentiation and proliferation in liquid and semisolid culture of marrow cells from 13 patients with myelodysplastic syndrome (MDS) were studied following incubation in liquid culture with low dose ARA-C. In six of ten patients an increasing number of myeloid cells acquired the morphologic appearance of mature monocyte-macrophages. Increasing number of cells reacted positively to fluoride sensitive naphthyl acetate esterase and specifically bound MY4 monoclonal antibody. Phagocytosis and killing of Candida albicans by monocyte-macrophages incubated with low dose ARA-C was normal and similar to that of the untreated cells. All MDS patients showed reduced myeloid colony and increased cluster formation. Low dose ARA-C had slight but non-significant inhibitory effects on myeloid colony growth. The results indicated that the differentiation pattern of myeloid precursor cells form a subset of MDS patients was altered by exposure to low dose ARA-C in vitro.