RESPONSE OF MYELODYSPLASTIC SYNDROME MARROW PROGENITOR CELLS TO STIMULATION WITH CYTOKINE COMBINATIONS IN A STROMA-FREE LONG-TERM CULTURE SYSTEM

The effect of an ex vivo expansion culture system using multiple cytok ine combinations was evaluated in 38 cases of myelodysplastic syndrome (MDS) with the aim of overcoming the defective in vitro growth of hae mopoietic progenitor cells. ii combination of four growth factors (GF) including SCF, IL-3, IL-6 and GM-CSF was identified as the optimal co mbination for expanding clonogenic progenitor cells in MDS bone marrow liquid cultures. The cultures of 50% of the patients (19/38) responde d to GF stimulation (mean CFU-GM fold increase 15.65 +/- 48 at week 4) and showed morphological features of normal and/or dysplastic myeloid differentiation, In 12/38 cases (31%), complete unresponsiveness to m ultiple cytokine stimulation was observed: a small number of patients (7/38) showed progressive leukaemic growth along the cultures with the presence of 100% immature blasts at week 4. GM-CSF and c-kit receptor s, analysed by immuno-histochemistry in 10 patients, were over-express ed in responding patients and either lacking or down-regulated in non- responders. Fluorescence in situ hybridization (FISH) analysis of cult ured interphase cells of nine patients (trisomy 8 in eight patients) s howed a clear-cut increase in the percentage of cells with three signa ls in the two responding patients, thus indicating the expansion of a MDS clone. Multiple cytokine liquid cultures seem to be able to overri de the refractoriness of MDS progenitor cells to GF stimulation in man y cases, revealing a heterogeneity which map have prognostic implicati ons and should be considered in ex-vivo and in vivo clinical trials wi th cytokine combinations.