Altered responses of purified blast cells from the myelodysplastic syndromes to colony-stimulating factors in vitro: comparison with normal blast cells.

To evaluate the effects of colony-stimulating factors (CSFs) on pathological cells from myelodysplastic syndromes (MDS), the blast cells from 19 MDS patients (eight low-risk MDS, six high-risk MDS, and five leukemic transformation of MDS [LT-MDS]) and four normal volunteers were successfully enriched by separating CD34-positive cells by the use of immunomagnetic beads, and their responsiveness to granulocyte or granulocyte-macrophage CSF (G-CSF or GM-CSF) was examined in short-term liquid suspension culture. The proliferation of MDS blast cells was clearly promoted by these CSFs in all cases examined, but considerable percentages of them often remained immature compared with the favorable maturation of normal blast cells, especially in the more advanced disease groups (LT-MDS and high-risk MDS) that included two prominent cases with a remarkable blast cell growth without maturation induction by CSFs. The expression of esterase activities was rather sluggish in the MDS cases, in contrast to normal expression. These data showed that MDS blast cells proliferate in response to CSFs but that maturation is less than that observed with normal blast cells in vitro. Much care should be taken with in vivo application of CSFs to high-risk MDS patients.