Increased peripheral stem cell pool in MDS: an indication of disease progression?

The colony-forming capacity of the peripheral blood stem/progenitor cells ( PBSC) in different forms of myelodysplastic syndrome (MDS) was investigated . In most cases of refractory anemia (RA) the colony growth of PBSC was def initely reduced as compared to the controls. However, in RA with unfavorabl e chromosomal aberrations, in refractory anemia with ringed sideroblasts (R ARS) and in advanced stages of MDS such as refractory anemia with excess bl asts (RAEB) and refractory anemia in transformation (RAEB-t), the number of myeloid progenitor cells increased up to 100-fold. In chronic myelomonocyt ic leukemia (CMML), the increase was even more marked, up to 350-fold. Alth ough the number of PBSC was strongly elevated, these cells were not able to restore hematopoiesis in vivo. In conclusion, the increase of circulating colony-forming cells (CFC) seems to be associated with disease progression, and thus, the evaluation of PBSC could be an important parameter in the di agnosis of MDS. (C) 2001 Elsevier Science Ltd. All rights reserved.