Multidimensional study of the heterogeneity of leukemia cells in t(8;21) acute myelogenous leukemia identifies the subtype with poor outcome.

Abstract

t(8;21)(q22;q22) acute myelogenous leukemia (AML) is morphologically characterized by a continuum of heterogeneous leukemia cells from myeloblasts to differentiated myeloid elements. Thus, t(8;21) AML is an excellent model for studying heterogeneous cell populations and cellular evolution during disease progression. Using integrative analyses of immunophenotype, RNA-sequencing (RNA-seq), and single-cell RNA-sequencing (scRNA-seq), we identified three distinct intrapatient leukemic cell populations that were arrested at different stages of myeloid differentiation: CD34⁺CD117^dim blasts, CD34⁺CD117^bri blasts, and abnormal myeloid cells with partial maturation (AM). CD117 is also known as c-KIT protein. CD34⁺CD117^dim cells were blocked in the G0/G1 phase at disease onset, presenting with the regular morphology of myeloblasts showing features of granulocyte-monocyte progenitors (GMP), and were drug-resistant to chemotherapy. Genes associated with cell migration and adhesion (<i>LGALS1</i>, <i>EMP3</i>, and <i>ANXA</i><i>2</i>) were highly expressed in the CD34⁺CD117^dim population. CD34⁺CD117^bri blasts were blocked a bit later than the CD34⁺CD117^dim population in the hematopoietic differentiation stage and displayed high proliferation ability. AM cells, which bear abnormal myelocyte morphology, especially overexpressed granule genes <i>AZU1</i>, <i>ELANE</i>, and <i>PRTN3</i> and were sensitive to chemotherapy. scRNA-seq at different time points identified CD34⁺CD117^dim blasts as an important leukemic cluster that expanded at postrelapse refractory stage after several cycles of chemotherapy. Patients with <i>t</i>(8;21) AML with a higher proportion of CD34⁺CD117^dim cells had significantly worse clinical outcomes than those with a lower CD34⁺CD117^dim proportion. Univariate and multivariate analyses identified CD34⁺CD117^dim proportion as an independent factor for poor disease outcome. Our study provides evidence for the multidimensional heterogeneity of t(8;21)AML and may offer new tools for future disease stratification.