ReseaRch aRticle Mass Cytometric Functional Profiling of Acute Myeloid Leukemia Defines Cell-Cycle and Immunophenotypic Properties That Correlate with Known Responses to Therapy

abstRact Acute myeloid leukemia (AML) is characterized by a high relapse rate that has been attributed to the quiescence of leukemia stem cells (LSC), which renders them resistant to chemotherapy. However, this hypothesis is largely supported by indirect evidence and fails to explain the large differences in relapse rates across AML subtypes. To address this, bone mar-row aspirates from 41 AML patients and five healthy donors were analyzed by high-dimensional mass cytometry. All patients displayed immunophenotypic and intracellular signaling abnormalities within CD34+CD38lo populations, and several karyotype- and genotype-specific surface marker patterns were identified. The immunophenotypic stem and early progenitor cell populations from patients with clinically favorable core-binding factor AML demonstrated a 5-fold higher fraction of cells in S-phase compared with other AML samples. Conversely, LSCs in less clinically favorable FLT3-ITD AML exhib-ited dramatic reductions in S-phase fraction. Mass cytometry also allowed direct observation of the in vivo effects of cytotoxic chemotherapy. SIGNIFICANCE: The mechanisms underlying differences in relapse rates across AML subtypes are poorly understood. This study suggests that known chemotherapy sensitivities of common AML sub-sets are mediated by cell-cycle differences among LSCs and provides a basis for using in vivo functiona