Blast colony-forming cells in myelodysplastic syndrome: decreased potential to generate erythroid precursors.

In vitro colony-forming abilities of highly purified primitive hematopoietic cells in eight cases of myelodysplastic syndrome (MDS) were studied using the blast cell colony assay. Blast cell colony formation from seven normal bone marrow (NBM) samples was studied in parallel. Blast cell colonies were formed in 7/8 cases of MDS, the numbers not significantly differing from those generated by NBM. In contrast the more mature hematopoietic progenitors (granulocyte-erythroid-macrophage-megakaryocyte colony-forming unit, CFU-GEMM; erythroid burst-forming units, BFU-E; granulocyte colony-forming units, CFU-G; eosinophilic colony-forming units, CFU-Eo) were severely depressed in numbers in MDS marrow. After replating of blast cell colonies in secondary cultures, colonies were obtained in 5/8 MDS cases. A marked difference was evident in the composition of the secondary colonies between MDS and normal marrow. Whereas secondary colonies derived from normal blast cell colonies consisted of about 45% of erythroid cells, MDS blast colonies generated mainly colonies of the granulocytic-monocytic lineage and no erythroid colonies. The normal quantitative level of CFU-blast progenitors in MDS in the context of their impaired ability to generate lineage specific progeny upon secondary plating suggests that the incompetence of maturation of MDS may reside in the CFU-blast progenitor cell being incapable of properly responding to growth factor stimulation.