Identifying phenotype of leukemic progenitor stem cells causing relapse in AML

Introduction:Acute Myeloid leukemia(AML) emerges from abnormal hematopoietic stem/progenitor cells(leukemic-HSPCs). Although most of the patients achieves complete remission, about 60% of them will experience disease relapse(Rx). AML is a heterogeneous disease composed of genetically variable cell subpopulations with different properties allowing chemoresistant leukemic-HSPCs to evade treatment and acquire new mutations promoting their survival.

Objective:Unraveling intra-patient leukemia heterogeneity and characterizing the genetic composition, chemoresistance and leukemogenic potential of leukemic-HSPCs at diagnosis(Dx) and Rx.

Methods:Segregating leukemic cells derived from AML patients into four subpopulation of HSPCs:HSC-MPP, MLP, CMP-MEP and GMP. Leukemic-HSPCs subpopulations were analyzed for leukemia-associated mutations and phylogenetic trees were generated for each patient at Dx and Rx. Additionally, HSPCs-single cell derived sub-clones were grown for phylogenetic reconstitutions and mutation profile, chemoresistance screening and functional assay to reveal leukemogenic potential in NSG-mice.

Results:Phylogenetic trees reconstitution revealed two main separated Dx and Rx clusters. In patient #230 two sub-populations of HSPCs(HSC-MPP and CMP-MEP)were detected at Dx suggesting they might have contributed to disease Rx. Moreover, in some cases Rx emerged from single cell derived MLP sub-population and generated leukemia in NSG mice. In addition, MLP cells found to be in-vitro chemoresistant to commonly used drugs used in leukemia compared to healthy HSPCs.

Conclusions:This new strategy based on single cell analysis enables advanced functional and genomic characterization of leukemic-HSPCs at Dx and Rx. The comparison between Dx and Rx stages enables to detect the Rx clone and characterize its phenotype at the time of Dx. Altogether, such a strategy may lead towards personalized therapy.