A Leukemia-Associated CD34/CD123/CD25/CD99+ Immunophenotype Identifies FLT3-Mutated Clones in Acute Myeloid Leukemia.

Clin Cancer Res 2015 Sep 8;21(17):3977-85. Epub 2015 May 8.

Department of Biomedicine and Prevention, University of Tor Vergata, Rome, Italy. Laboratorio di Neuro-Oncoematologia, Fondazione Santa Lucia I.R.C.C.S, Rome, Italy.

Purpose: We evaluated leukemia-associated immunophenotypes (LAIP) and their correlation with fms-like tyrosine kinase 3 (FLT3) and nucleophosmin (NPM1) gene mutational status in order to contribute a better identification of patients at highest risk of relapse in acute myeloid leukemia (AML).

Experimental Design: Bone marrow samples from 132 patients with AML were analyzed by nine-color multiparametric flow cytometry. We confirmed the presence of the mutation in diagnostic samples and in sorted cells by conventional RT-PCR and by patient-specific RQ-PCR.

Results: Within the CD34(+) cell fraction, we identified a discrete population expressing high levels of the IL3 receptor α-chain (CD123) and MIC-2 (CD99) in combination with the IL2 receptor α-chain (CD25). The presence of this population positively correlated with the internal tandem duplications (ITD) mutation in the FLT3 gene (r = 0.71). Receiver operating characteristics showed that, within the CD34(+) cell fraction a percentage of CD123/CD99/CD25(+) cells ≥11.7% predicted FLT3-ITD mutations with a specificity and sensitivity of >90%. CD34/CD123/CD99/CD25(+) clones were also detectable at presentation in 3 patients with FLT3 wild-type/NPM1(+) AML who relapsed with FLT3-ITD/NPM1(+) AML. Quantitative real-time PCR designed at relapse for each FLT3-ITD in these three cases confirmed the presence of low copy numbers of the mutation in diagnostic samples.

Conclusions: Our results suggest that the CD34/CD25/CD123/CD99(+) LAIP is strictly associated with FLT3-ITD-positive cells.

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http://dx.doi.org/10.1158/1078-0432.CCR-14-3186DOI Listing
September 2015
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