the molecular signature of mds stem cells supports a stemcell origin of 5q myelodysplastic syndromes global gene expression profiling of highly purified 5qdeleted cd34cd38thy1 cells in 5q myelodysplastic syndromes mdss supported that they might originate from and outcompete normal cd34cd38thy1 hematopoietic stem cells few but distinct differences in gene expression distinguished mds and normal stem cells expression of bmi1 encoding a critical regulator of selfrenewal was upregulated in 5q stem cells whereas multiple previous mds genetic screens failed to identify altered expression of the gene encoding the myeloid transcription factor cebpa stagespecific and extensive downregulation of cebpa was specifically observed in mds progenitors these studies establish the importance of molecular characterization of distinct stages of cancer stem and progenitor cells to enhance the resolution of stagespecific dysregulated gene expression