Abstract
SummaryEvidence of distinct disease propagating stem cells in myelodysplastic syndrome (MDS) has emerged in recent years. However, immunophenotypic characterization of these cancer stem cells remains sparse. In acute myeloid leukaemia (AML), we have previously described aberrant expression of the C‐type lectin domain family 12, member A (CLEC12A) as a stable and reliable marker of leukaemia blasts and as a tool for assessing minimal residual disease. Furthermore, CLEC12A has been proposed as a promising marker of leukaemic stem cells in AML. The role of CLEC12A in MDS, however, remains to be elucidated. In this study, we found CLEC12A aberrantly expressed on the CD34+ CD38− cell compartment in 71% (22/31) of MDS patients, distributed across all Revised International Prognostic Scoring System risk groups. We showed that the CD34+ CD38− CLEC12A+ cells were indeed malignant and possessed functional stem cell properties in the long‐term colony‐initiating cell assay. As opposed to reported findings in AML, we showed that cancer stem cells from MDS samples derived from both CLEC12A positive and negative CD34+ CD38− subpopulations. Due to the absence of CLEC12A on normal haematopoietic stem cells, CLEC12A stem cell immunophenotyping may contribute to diagnosing and monitoring MDS patients and could furthermore add knowledge about disease propagating cells in MDS.
Highlights
Consistent with previous findings, CLEC12A was completely absent on the CD34+CD38À cell compartment in all of the 19 normal BM (NBM) examined (0Á0%)
In CD34-positive acute myeloid leukaemia (AML) (n = 21), the percentage of CLEC12A-positive CD34+CD38À cells amounted a median of 13Á1%, which was significantly different from NBM (P < 0Á0001), but not from myelodysplastic syndrome (MDS) bone marrow (BM) (P = 0Á08) (Fig 1B)
When we examined and harvested the single colonies derived from long-term colony initiating cell (LTC-IC), we observed that CFCs from MDS patients were morphologically abnormal and smaller than those from normal controls and were almost exclusively of non-erythroid origin (Fig 2A and B)
Summary
Bone marrow samples were obtained as excess material taken as part of the diagnostic process from 31 MDS patients diagnosed at the Department of Haematology, Aarhus University Hospital. The study was conducted in accordance with the Declaration of Helsinki and was approved by the local ethics committee. All samples were collected before treatment with cytoreductive or demethylating agents. MDS diagnoses were confirmed by morphological examination according to the. In four selected MDS patient cases (MDS patients 8, 29, 30 and 31) fluorescence activated cell sorting (FACS) was performed on a BD FACSAriaTM III (BD Biosciences). Cells were sorted into two subsets, CD45lowSSClowCD34+CD38À CLEC12A+ and CD45lowSSClowCD34+CD38ÀCLEC12AÀ using the same gating strategy as described above. The CD45lowSSClowCD34+CD38ÀCLEC12AÀ subset from two NBMs was sorted as controls.
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