Heterogeneous colony forming ability in vitro of the abnormal clone-derived granulocyte-macrophage precursors in myelodysplastic syndromes.

The clonal origin of granulocyte-macrophage colony forming cells (CFU-GM) in the myelodysplastic syndrome (MDS) was cytogenetically studied. Chromosome analysis was carried out on single GM-colonies from six patients with MDS, whose bone marrow cells had chromosome abnormalities. Abnormal clone-derived CFU-GM were grown in four patients under the presence of human placental conditioned medium. In the remaining two, all analysed colonies revealed a normal karyotype, although the majority of metaphase cells showed an abnormal karyotype in bone marrow preparations. These results indicate that the abnormal clone-derived CFU-GM in MDS have a clone-by-clone variation in colony forming ability in vitro.