Reconstruction of Human AML Using Functionally and Immunophenotypically Defined Human Haematopoietic Stem and Progenitor Cells as Targeted Populations

Acute myeloid leukaemia (AML) is a highly heterogenous blood cancer, in which the expansion of aberrant myeloid blood cells interferes with the generation and function of normal blood cells. Although key driver mutations and their associated inhibitors have been identified in the last decade, they have not been fully translated into better survival rates for AML patients, which remain dismal. In addition to DNA mutation, studies in mouse models strongly suggest that the cell of origin, where the driver mutation (such as MLL fusions) occurs, emerges as an additional factor that determines the treatment outcome in AML. To investigate its functional relevance in human disease, we have recently reported that AML driven by MLL fusions can transform immunophenotypically and functionally distinctive human hematopoietic stem cells (HSCs) or myeloid progenitors resulting in immunophenotypically indistinguishable human AML. Intriguingly, these cells display differential treatment sensitivities to current treatments, attesting the cell of origin as an important determinant governing treatment outcome for AML. To further facilitate this line of investigation, here we describe a comprehensive disease modelling protocol using human primary haematopoietic cells, which covers all the key steps, from the isolation of immunophenotypically defined human primary haematopoietic stem and progenitor populations, to oncogene transfer via viral transduction, the in vitro liquid culture assay, and finally the xenotransplantation into immunocompromised mice.

A Menin-MLL Inhibitor Induces Specific Chromatin Changes and Eradicates Disease in Models of MLL-Rearranged Leukemia

Inhibition of the Menin (MEN1) and MLL (MLL1, KMT2A) interaction is a potential therapeutic strategy for MLL-rearranged (MLL-r) leukemia. Structure-based design yielded the potent, highly selective, and orally bioavailable small-molecule inhibitor VTP50469. Cell lines carrying MLL rearrangements were selectively responsive to VTP50469. VTP50469 displaced Menin from protein complexes and inhibited chromatin occupancy of MLL at select genes. Loss of MLL binding led to changes in gene expression, differentiation, and apoptosis. Patient-derived xenograft (PDX) models derived from patients with either MLL-r acute myeloid leukemia or MLL-r acute lymphoblastic leukemia (ALL) showed dramatic reductions of leukemia burden when treated with VTP50469. Multiple mice engrafted with MLL-r ALL remained disease free for more than 1 year after treatment. These data support rapid translation of this approach to clinical trials.

In vivo Leukemogenesis Model Using Retrovirus Transduction

Various genetic alterations such as chromosomal translocation cause leukemia. For examples, gene rearrangements of the mixed-lineage leukemia (MLL) gene generate MLL fusion genes, whose products are potent oncogenic drivers in acute leukemia. To better understand the mechanism of disease onset, several murine leukemia models using retroviral gene transduction, xenograft, or Cre-mediated chromosomal translocation have been developed over the past twenty years. Particularly, a retroviral gene transduction-mediated murine leukemia model has been frequently used in the leukemia research field. Here, we describe the detailed protocol for this model.

Myeloid Progenitor Transformation Assay

Numerous oncogenes have been identified to cause leukemia. For example, chromosomal translocation generates various fusion genes of the mixed-lineage leukemia (MLL) gene and a partner gene in leukemia, whose gene products transform primary myeloid progenitors into an immortalized state. To characterize the transforming ability of leukemic oncogenes, researchers in the field have developed an ex vivo murine myeloid transformation assay using retroviral gene transduction and its protocol has been improved over the past 10 years. Here, we provide the detailed procedure for this assay.