Runx1 deficiency permits granulocyte lineage commitment but impairs subsequent maturation

• Autores: Ng, K. P.; Hu, Z.; Ebrahem, Q.; Negrotto, Soledad; Lausen, J.; Saunthararajah, Y.
• Año de publicación: 2013
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: RUNX1; HEMATOPOIETIC STEM CELL; LEUKEMIA STEM CELL; GRANULOCYTE MATURATION; ACUTE MYELOID LEUKEMIA; MYELODYSPLASTIC SYNDROME; DIFFERENTIATION THERAPY; CEBPA; CEBPE
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

First-hits in the multi-hit process of leukemogenesis originate in germline or hematopoietic stem cells (HSCs), yet leukemia-initiating cells (LICs) usually have a lineage-committed phenotype. The molecular mechanisms underlying this compartment shift during leukemia evolution have not been a major focus of investigation and remain poorly understood. Here a mechanism underlying this shift was examined in the context of Runx1 deficiency, a frequent leukemia-initiating event. Lineage-negative cells isolated from the bone marrow of Runx1-haploinsufficient and wild-type control mice were cultured in granulocyte-colony-stimulating factor to force lineage commitment. Runx1-haploinsufficient cells demonstrated significantly greater and persistent exponential cell growth than wild-type controls. Not surprisingly, the Runx1-haploinsufficient cells were differentiation-impaired, by morphology and by flow-cytometric evaluation for granulocyte differentiation markers. Interestingly, however, this impaired differentiation was not because of decreased granulocyte lineage commitment, as RNA and protein upregulation of the master granulocyte lineage-commitment transcription factor Cebpa, and Hoxb4 repression, was similar in wild-type and Runx1-haploinsufficient cells. Instead, RNA and protein expression of Cebpe, a key driver of progressive maturation after lineage commitment, were significantly decreased in Runx1-haploinsufficient cells. Primary acute myeloid leukemia cells with normal cytogenetics and RUNX1 mutation also demonstrated this phenotype of very high CEBPA mRNA expression but paradoxically low expression of CEBPE, a CEBPA target gene. Chromatin-immunoprecipitation analyses suggested a molecular mechanism for this phenotype: in wild-type cells, Runx1 binding was substantially greater at the Cebpe than at the Cebpa enhancer. Furthermore, Runx1 deficiency substantially diminished high-level Runx1 binding at the Cebpe enhancer, but lower-level binding at the Cebpa enhancer was relatively preserved. Thus, Runx1-deficiency permits Cebpa upregulation and the exponential cell growth that accompanies lineage commitment, but by impairing activation of Cebpe, a key proliferation-terminating maturation gene, extends this exponential growth. These mechanisms facilitate germline cell or HSC of origin, yet evolution into LIC with lineage-committed phenotype.
Fil: Ng, K. P.. Cleveland Clinic. Translational Hematology and Oncology Research; Estados Unidos
Fil: Hu, Z.. Cleveland Clinic. Translational Hematology and Oncology Research; Estados Unidos
Fil: Ebrahem, Q.. Cleveland Clinic. Translational Hematology and Oncology Research; Estados Unidos
Fil: Negrotto, Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentina. Cleveland Clinic. Translational Hematology and Oncology Research; Estados Unidos
Fil: Lausen, J.. Georg-Speyer-Haus, Institute for Biomedical Research; Alemania
Fil: Saunthararajah, Y.. Cleveland Clinic; Estados Unidos