ABSTRACT
The AML1/ETO fusion protein found in acute myeloid leukemias functions as a transcriptional regulator by recruiting co-repressor complexes to its DNA binding site. In order to extend the understanding of its role in preleukemia, we expressed AML1/ETO in a murine immortalized pluripotent hematopoietic stem/progenitor cell line, EML C1, and found that genes involved in functions such as cell-to-cell adhesion and cell motility were among the most significantly regulated as determined by RNA sequencing. In functional assays, AML1/ETO-expressing cells showed a decrease in adhesion to stromal cells, an increase of cell migration rate in vitro, and displayed an impairment in homing and engraftment in vivo upon transplantation into recipient mice. Our results suggest that AML1/ETO expression determines a more mobile and less adherent phenotype in preleukemic cells, therefore altering the interaction with the hematopoietic niche, potentially leading to the migration across the bone marrow barrier and to disease progression.
Subject(s)
Hematopoietic Stem Cells/physiology , Neoplastic Stem Cells/physiology , Oncogene Proteins, Fusion/physiology , Animals , Cell Adhesion/genetics , Cell Adhesion/physiology , Cell Line, Tumor , Cell Movement/genetics , Cell Movement/physiology , Core Binding Factor Alpha 2 Subunit/genetics , Core Binding Factor Alpha 2 Subunit/physiology , Female , Hematopoietic Stem Cells/pathology , Humans , Leukemia, Myeloid, Acute/genetics , Leukemia, Myeloid, Acute/pathology , Leukemia, Myeloid, Acute/physiopathology , Male , Mice , Mice, Inbred C57BL , Mice, Inbred NOD , Mice, SCID , Neoplastic Stem Cells/pathology , Oncogene Proteins, Fusion/genetics , RUNX1 Translocation Partner 1 Protein/genetics , RUNX1 Translocation Partner 1 Protein/physiology , Stem Cell Niche/genetics , Stem Cell Niche/physiology , Tumor Microenvironment/geneticsABSTRACT
Nucleophosmin (NPM1) is a ubiquitous multifunctional phosphoprotein with both oncogenic and tumor suppressor functions. Mutations of the NPM1 gene are the most frequent genetic alterations in acute myeloid leukemia (AML) and result in the expression of a mutant protein with aberrant cytoplasmic localization, NPMc+. Although NPMc+ causes myeloproliferation and AML in animal models, its mechanism of action remains largely unknown. Here we report that NPMc+ activates canonical Wnt signaling during the early phases of zebrafish development and determines a Wnt-dependent increase in the number of progenitor cells during primitive hematopoiesis. Coherently, the canonical Wnt pathway is active in AML blasts bearing NPMc+ and depletion of the mutant protein in the patient derived OCI-AML3 cell line leads to a decrease in the levels of active ß-catenin and of Wnt target genes. Our results reveal a novel function of NPMc+ and provide insight into the molecular pathogenesis of AML bearing NPM1 mutations.
