In Vitro Biology of the Hematopoietic System in Myelodysplastic Syndromes

Abstract

The myelodysplastic syndromes (MDS) comprise a heterogeneous group of hematological disorders characterized by ineffective hematopoiesis with a high frequency of progression into acute myeloid leukemia (AML; [Heaney and Golde, 1999]). During the last few years, compelling evidence has accumulated indicating the clonal nature of MDS ([Kere et al., 1987]; [Janssen et al., 1989]). The identity of the cell in which transformation takes place, however, is still not clear. Some studies suggest that the transformation event in MDS occurs at the level of a committed myeloid progenitor ([Kroef et al., 1993]; [Saitoh et al., 1998]); this is supported by the fact that MDS rarely transforms into acute lymphoblastic leukemia. In contrast, a recent study by [Nilsson et al (2000)] shows evidence that transformation may occur on a lympho-myeloid stem cell, suggesting that the apparent myeloid-lineage restriction is a result of the transforming event itself. Regardless of these two possible scenarios the fact is that severe hematopoietic alterations exist in MDS, both at the level of hematopoietic progenitors and their marrow microenvironment ([Yoshida, 1987]; [Mayani, 1993]).