Distinct Reactive Oxygen Species, BCL2 and Cell-Cycle Profiles That Are Decoupled from Maturation in Acute Myeloid Leukemia

In acute myeloid leukemia (AML) quiescence and low oxidative state, linked to BCL2 mitochondrial regulation, endow leukemic stem cells (LSC) with treatment-resistance. LSC in CD34 and more mature CD34 AML have heterogeneous immunophenotypes overlapping with normal stem/progenitor cells (SPC) but may be differentiated by functional markers. We therefore investigated the oxidative/reactive oxygen species (ROS) profile, its relationship with cell-cycle/BCL2 for normal SPC, and whether altered in AML and myelodysplasia (MDS). In control BM (n = 24), ROS levels were highest in granulocyte-macrophage progenitors (GMP) and CD34 myeloid precursors but megakaryocyte-erythroid progenitors had equivalent levels to CD34CD38 immature-SPC although they were ki67. BCL2 upregulation was specific to GMPs. This profile was also observed for CD34SPC in MDS-without-excess-blasts (MDS-noEB, n = 12). Erythroid CD34 precursors were, however, abnormally ROS-high in MDS-noEB, potentially linking oxidative stress to cell loss. In pre-treatment AML (n = 93) and MDS-with-excess-blasts (MDSRAEB) (n = 14), immunophenotypic mature-SPC had similar ROS levels to co-existing immature-SPC. However ROS levels varied between AMLs; Flt3ITD/NPM1wild-type CD34SPC had higher ROS than NPM1mutated CD34 or CD34 SPC. An aberrant ki67BCL2 immunophenotype was observed in CD34AML (most prominent in Flt3ITD AMLs) but also in CD34 AMLs and MDS-RAEB, suggesting a shared redox/prosurvival adaptation. Some patients had BCL2 overexpression in CD34 ROS-high as well as ROS-low fractions which may be indicative of poor early response to standard chemotherapy. Thus normal SPC subsets have distinct ROS, cell-cycle, BCL2 profiles that in PLOS ONE | DOI:10.1371/journal.pone.0163291 September 26, 2016 1 / 19 a11111