CD34 and myelodysplastic syndrome: We have also previously observed that long-term hematopoietic stem cells (HSCs, lineage−/CD34+/CD38-/CD90+) in MDS have abnormal DNA methylation compared with the same cell type from healthy control subjects and that treatment with 5-aza-CR does not influence the levels of mosaicism for cytogenetic abnormalities in these HSCs, indicating that the therapeutic response is through effects on the functional properties of these neoplastic cells rather than their eradication [10].