Characterization of FLT3-ITD acute myeloid leukemia: molecular profiling of leukemic precursor cells.

Blood Cancer J 2020 08 25;10(8):85. Epub 2020 Aug 25.

Department of Biomedicine and Prevention, University of Tor Vergata, Rome, Italy.

Acute myeloid leukemia (AML) with FLT3-ITD mutations (FLT3-ITD) remains a therapeutic challenge, with a still high relapse rate, despite targeted treatment with tyrosine kinase inhibitors. In this disease, the CD34/CD123/CD25/CD99+ leukemic precursor cells (LPCs) phenotype predicts for FLT3-ITD-positivity. The aim of this study was to characterize the distribution of FLT3-ITD mutation in different progenitor cell subsets to shed light on the subclonal architecture of FLT3-ITD AML. Using high-speed cell sorting, we sequentially purified LPCs and CD34+ progenitors in samples from patients with FLT3-ITD AML (n = 12). A higher FLT3-ITD load was observed within CD34/CD123/CD25/CD99+ LPCs, as compared to CD34+ progenitors (CD123+/-,CD25-,CD99low/-) (p = 0.0005) and mononuclear cells (MNCs) (p < 0.0001). This was associated with significantly increased CD99 mean fluorescence intensity in LPCs. Significantly higher FLT3-ITD burden was also observed in LPCs of AML patients with a small FLT3-ITD clones at diagnosis. On the contrary, the mutation burden of other myeloid genes was similar in MNCs, highly purified LPCs and/or CD34+ progenitors. Treatment with an anti-CD99 mAb was cytotoxic on LPCs in two patients, whereas there was no effect on CD34+ cells from healthy donors. Our study shows that FLT3-ITD mutations occur early in LPCs, which represent the leukemic reservoir. CD99 may represent a new therapeutic target in FLT3-ITD AML.

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http://dx.doi.org/10.1038/s41408-020-00352-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7447750PMC
August 2020

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