Summary
MLL-fusion proteins can induce acute myeloid leukemias (AML) from either hematopoietic stem cells (HSC) or granulocyte macrophage progenitors (GMP), but it remains unclear if the cell of origin influences the biology of the resultant leukemia. MLL-AF9 transduced single HSC or GMP could be continuously replated, but HSC-derived clones were more likely than GMP-derived clones to initiate AML in mice. Leukemia stem cells derived from either HSC or GMP had a similar immunophenotype consistent with a maturing myeloid cell (LGMP). Gene expression analyses demonstrated that LGMP inherited gene expression programs from the cell of origin including high-level Evi-1 expression in HSC derived LGMP. The gene expression signature of LGMP derived from HSC was enriched in poor prognosis human MLL-rearranged AML in three independent data sets. Moreover, global 5’-mC levels were elevated in HSC-derived leukemias as compared to GMP-derived leukemias. This mirrored a difference seen in 5-mC between MLL-rearranged human leukemias that are either EVI1-positive or EVI1-negative. Finally, HSC derived leukemias were more resistant to chemotherapy than GMP-derived leukemias. These data demonstrate that the cell of origin influences the gene expression profile, the epigenetic state, and the drug response in AML, and that these differences can account for clinical heterogeneity within a molecularly defined group of leukemias.
Significance
Human AMLs are heterogeneous even within subtype defined by a specific genetic lesion such as MLL-translocations and this leads to variable clinical outcomes. The developmental stage (or epigenetic state) of the cell in which leukemogenic transformation is initiated may contribute to the ultimate disease phenotype. We used a well established model of MLL-AF9 mediated AML and transformation of single cells to test the relevance of the leukemia cell of origin on AML development, gene expression profiles, DNA methylation and chemotherapy response. We show that HSC derived AML models human high-risk/poor outcome AML pool, and that we can recapitulate important clinical subtypes of human MLL-rearranged AML through the transformation of different cell types. These data demonstrate that the cell of origin can influence the phenotype of a resultant leukemia even if the initiating genetic lesion is the same.