High levels of CD34+CD38low/-CD123+ blasts are predictive of an adverse outcome in acute myeloid leukemia: a Groupe Ouest-Est des Leucemies Aigues et Maladies du Sang (GOELAMS) study

Abstract

Background: Acute myeloid leukemias arise from a rare population of leukemic cells, known as leukemic stem cells, which initiate the disease and contribute to frequent relapses. Although the phenotype of these cells remains unclear in most patients, these cells are enriched within the CD34(+)CD38(low/-) compartment expressing the interleukin-3 alpha chain receptor, CD123. The aim of this study was to determine the prognostic value of the percentage of blasts with the CD34(+)CD38(low/-)CD123(+) phenotype.

Design and methods: The percentage of CD34(+)CD38(low/-)CD123(+) cells in the blast population was determined at diagnosis using flow cytometry. One hundred and eleven patients under 65 years of age with de novo acute myeloid leukemia and treated with intensive chemotherapy were retrospectively included in the study. Correlations with complete response, disease-free survival and overall survival were evaluated with univariate and multivariate analyses.

Results: A proportion of CD34(+)CD38(low/-)CD123(+) cells greater than 15% at diagnosis and an unfavorable karyotype were significantly correlated with a lack of complete response. By logistic regression analysis, a percentage of CD34(+)CD38(low/-)CD123(+) higher than 15% retained significance with an odds ratio of 0.33 (0.1-0.97; P=0.044). A greater than 1% population of CD34(+)CD38(low/-)CD123(+) cells negatively affected disease-free survival (0.9 versus 4.7 years; P<0.0001) and overall survival (1.25 years versus median not reached; P<0.0001). A greater than 1% population of CD34(+)CD38(low/-)CD123(+) cells retained prognostic significance for both parameters after multivariate analysis.

Conclusions: The percentage of CD34(+)CD38(low/-)CD123(+) leukemic cells at diagnosis was significantly correlated with response to treatment and survival. This prognostic marker might be easily adopted in clinical practice to rapidly identify patients at risk of treatment failure.

Figure 1.

The percentage of CD34⁺CD38^low/−CD123⁺ leukemic cells is highly variable in AML patients. Blasts and mononuclear cells from 111 AML samples were analyzed by flow cytometry. First, bulk cells (blue and orange) and lymphocytes (purple) were gated according to CD45 intensity in a CD45/sidescatter dot plot: dot plot 1 in patient #24 (A) and patient #87 (B); CD45 intensity of AML blasts is low/dim whereas it is bright on lymphocytes. Blast expression of CD34 and CD38 was then assessed in a second dot plot (dot plot 2). Isotype controls were used as negative controls. Gate a focus on bulk cells with CD34⁺CD38^low/− phenotype. Finally, CD123 expression on CD34⁺CD38^low/−cells (in orange, gate a) was assessed in a third dot plot (dot plot 3 in patients #24 and #87) in order to exclude normal CD34⁺CD38^low/− hematopoietic stem cells that do not express CD123. Percentages of CD34⁺CD38^low/−CD123⁺ leukemic cells (gate b) for patients #24 and #87 are 0.78% and 10.81%, respectively. Isotype controls are shown in dot plots 4 and 5.

Figure 2.

Comparison of disease-free and overall survival of AML patients according to CD34⁺CD38^low/−CD123⁺ percentage. (A) All patients. (B) Intermediate cytogenetics group. (C) Favorable cytogenetics group.