VARIABLE GROWTH IN-VITRO OF CHROMOSOMALLY DIFFERENT STEM-CELLS IN MYELODYSPLASTIC SYNDROMES

Ten patients with myelodysplastic syndromes were investigated using in vitro colony assay of bone marrow cells and chromosome analysis of si ngle colonies. The result was compared with conventional cytogenetic a nalysis of bone marrow cells. The chromosome abnormalities included we re 5q-, +8, -7, 11q-, -Y and one complex karyotype. Erythroid colony f ormation was reduced in eight patients, while the number of granulocyt e-macrophage colony-forming units was normal or increased. Cytogenetic examination of single colonies showed that both chromosomally normal and abnormal stem cells had colony forming ability. The proportion of cytogenetically abnormal colonies varied between 25 and 100% of analys ed colonies. No further clones than those found in direct cytogenetic analysis were revealed after in vitro growth. One patient with a 5q- a bnormality and one patient with a -7 abnormality showed a significantl y lower proportion of cytogenetically abnormal colonies than the propo rtion of abnormal cells in the direct bone marrow chromosome preparati on. One patient with a +8 abnormality showed a growth advantage of the +8 clone in comparison with the chromosomally normal clones, but this was not statistically significant. In two patients a chromosomally ch anged stem cell gave rise to both erythroid and myeloid colonies. The FAB-class did not seem to influence the growth of either chromosomally normal or abnormal colonies.