Effect of in vivo treatment with RH GM-CSF on in vitro growth of haematopoietic progenitors in patients with myelodysplastic syndromes

Background. Recombinant (r) human (h) granulocyte/macrophage colony stimulating factor (rh GM-CSF) has been shown to increase the number of peripheral blood (PB) neutrophils, eosinophils and monocytes in myelodysplastic syndromes (MDS). The aims of this study were: 1) to evaluate the effect of rh GM-CSF therapy on the in vitro growth of granulocyte-erythroid-macrophage-megakaryocyte colonies (CFU-GEMM), erythroid colonies (BFU-E), and granulocyte-macrophage colonies (CFU-GM) in patients with MDS; 2) to assess in these patients, while they are being treated in vivo with rh GM-CSF, the possible additive effect of rh IL-3 and rh G-CSF on the in vitro growth of haematopoietic progenitors. Methods. The in vitro growth of CFU-GEMM, BFU-E and CFU-GM was studied in 10 myelodysplastic (MDS) patients, before and after in vivo administration of rh GM-CSF. Results. After rh GM-CSF administration, the number of CFU-GM increased in all standard risk MDS patients. In 2 out of 5 cases, this effect was more pronounced and persisted up to 30 days after the end of rh GM-CSF treatment. On the other hand, the number of CFU-GEMM and BFU-E was substantially unchanged. When rh GM-CSF, rh G-CSF and rh IL-3 were added in vitro alone or in combination as the source of colony stimulating activity, no significant increase of the CFU-GM colony number was noticed. Conclusions. Rh GM-CSF therapy appears useful for increasing the number of peripheral blood granulocytes and of marrow CFU-GM in standard-risk MDS patients. High-risk MDS patients are far less responsive to rh GM-CSF treatment, probably reflecting a more aggressive and/or advanced disease.