Expression of CD25 antigen on CD34+ cells is an independent predictor of outcome in late-stage MDS patients treated with azacitidine

The expression of CD25 antigen, the a-chain of the interleukin-2 receptor (IL-2Ra), has been repeatedly shown to be associated with poor outcome in adults with either acute myelogenous (AML) or lymphoblastic leukemia. To explain this finding mechanistically, it has been hypothesized that CD25þ AML blasts are enriched in chemoresistant leukemia stem cells (LSCs), as they bear an LSC-like molecular signature, are quiescent and can establish AML in xenograft models. Blasts from patients with myelodysplastic syndrome-related AML (AML-MDS) appear to express CD25 more frequently compared with de novo AML patients, but although late-stage MDS is typically chemoresistant, the prognostic relevance of CD25 has not been investigated yet. On the basis of the above, and as there is paucity of a serviceable biomarker of outcome in MDS patients treated with azacitidine, we addressed the prognostic impact of CD25 expression in a cohort of 61 patients with IPSS intermediate-2/high-risk MDS and chronic myelomonocytic leukemia-2 managed between June 2009 to September 2013 at eight Greek institutions in a non-clinical trial setting.