Increased Levels of Circulating Monocytic- and Early-Stage Myeloid-Derived Suppressor Cells (MDSC) in Acute Myeloid Leukemia.

Background: To investigate the levels of circulating myeloid-derived suppressor cells (MDSC) in patients with primary acute myeloid leukemia (AML), and to explore the relationship between the number of MDSC and AML.

Methods: Peripheral blood samples from 29 patients with primary AML and 30 healthy controls were collected. CD33, CD11b, HLA-DR, CD14, and CD15 were used to label cells, and flow cytometry was used to analyze the numbers of total MDSC and subgroups eMDSC (early-stage MDSC), M-MDSC (monocytic MDSCs), PMN-MDSC (polymorphonuclear-MDSCs) or G-MDSC (granulocytic-MDSC) via two gating strategies. Presence of MDSC in AML was determined after assessment of clinical data.

Results: Phenotypic analysis of MDSC by the two gating strategies was consistent. Compared with healthy controls, the numbers of total MDSC (CD33+CD11b+ HLA-DR-) and G-MDSC (CD33+CD11b+ HLA-DR-CD14¬-CD15+ or CD14¬-CD15+ CD11b+) in peripheral blood of AML patients were lower (p < 0.05), while numbers of M-MDSC (CD33+CD11b+ HLA-DR-CD14+CD15- or HLA-DR-/LOWCD14+) and eMDSC (CD33+CD11b+ HLA-DR-/LOWCD14-CD15-) were higher (p < 0.05). The levels of G-MDSC in peripheral blood of AML-M2 patients were higher than those in other subtypes, along with total MDSC, while the levels of eMDSC and M-MDSC in AML-M3 patients were higher than those in other subtypes.

Conclusions: The high frequency of HLA-DR-/LOWCD14+M-MDSC and CD33+CD11b+ HLA-DR-/LOWCD14-CD15- eMDSC in peripheral blood of AML patients indicates potential for MDSC as a diagnostic index in AML.