RESUMEN
Trib1 has been identified as a myeloid oncogene in a murine leukemia model. Here we identified a TRIB1 somatic mutation in a human case of Down syndrome-related acute megakaryocytic leukemia. The mutation was observed at well-conserved arginine 107 residue in the pseudokinase domain. This R107L mutation remained in leukocytes of the remission stage in which GATA1 mutation disappeared, suggesting the TRIB1 mutation is an earlier genetic event in leukemogenesis. The bone marrow transfer experiment showed that acute myeloid leukemia development was accelerated by transducing murine bone marrow cells with the R107L mutant in which enhancement of ERK phosphorylation and C/EBPα degradation by Trib1 expression was even greater than in those expressing wild-type. These results suggest that TRIB1 may be a novel important oncogene for Down syndrome-related acute megakaryocytic leukemia.
Asunto(s)
Síndrome de Down/genética , Péptidos y Proteínas de Señalización Intracelular/genética , Leucemia Megacarioblástica Aguda/etiología , Mutación/genética , Oncogenes/genética , Proteínas Serina-Treonina Quinasas/genética , Animales , Células de la Médula Ósea/citología , Células de la Médula Ósea/metabolismo , Proteína alfa Potenciadora de Unión a CCAAT/genética , Proteína alfa Potenciadora de Unión a CCAAT/metabolismo , Diferenciación Celular , Síndrome de Down/complicaciones , Quinasas MAP Reguladas por Señal Extracelular/genética , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Femenino , Humanos , Immunoblotting , Leucemia Megacarioblástica Aguda/patología , Ratones , Ratones Endogámicos C57BL , Fosforilación , ARN Mensajero/genética , Reacción en Cadena en Tiempo Real de la PolimerasaRESUMEN
Trib1 is a myeloid oncogene that cooperates with Hoxa9 and Meis1. Although the MAPK pathway and C/EBP transcription factors are known to interact with Trib proteins, the mechanisms by which Trib1 contributes to myeloid leukemogenesis remains to be clarified. Here we report that interaction between Trib1 and MEK1 is required for Trib1-induced leukemogenesis. The C-terminal ILLHPWF motif that is well conserved among Trib family proteins is required for MEK1 binding, enhancement of ERK phosphorylation, enhanced self-renewal activity of bone marrow cells and leukemogenic activity by Trib1. The motif is also important for Trib1-induced C/EBPα degradation though interaction between Trib1 and C/EBPα is not necessary. Inhibition of ERK phosphorylation suppressed Trib1-induced C/EBPα degradation, indicating an important role for Trib1/MEK1 interaction. These results suggest that Trib1 may be a key mediator between the RTK-MAPK pathway and the C/EBP transcription factor in myeloid leukemogenesis.
Asunto(s)
Péptidos y Proteínas de Señalización Intracelular/metabolismo , Leucemia Mieloide/etiología , MAP Quinasa Quinasa 1/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Animales , Células de la Médula Ósea/metabolismo , Células de la Médula Ósea/patología , Proteína alfa Potenciadora de Unión a CCAAT/metabolismo , Línea Celular Tumoral , Regulación hacia Abajo , Femenino , Células HeLa , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Humanos , Péptidos y Proteínas de Señalización Intracelular/química , Péptidos y Proteínas de Señalización Intracelular/genética , Leucemia Mieloide/genética , Leucemia Mieloide/metabolismo , Leucemia Mieloide/patología , MAP Quinasa Quinasa 1/química , MAP Quinasa Quinasa 1/genética , Sistema de Señalización de MAP Quinasas , Ratones , Ratones Endogámicos C57BL , Proteína 1 del Sitio de Integración Viral Ecotrópica Mieloide , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Oncogenes , Fosforilación , Dominios y Motivos de Interacción de Proteínas , Proteínas Serina-Treonina Quinasas/química , Proteínas Serina-Treonina Quinasas/genéticaRESUMEN
Chronic myelogenous leukemia (CML) is a hematopoietic disorder originating from p210BCR/ABL-transformed stem cells, which begins as indolent chronic phase (CP) but progresses into fatal blast crisis (BC). To investigate molecular mechanism(s) underlying disease evolution, CML-exhibiting p210BCR/ABL transgenic mice were crossed with BXH2 mice that transmit a replication-competent retrovirus. Whereas nontransgenic mice in the BXH2 background exclusively developed acute myeloid leukemia, p210BCR/ABL transgenic littermates developed nonmyeloid leukemias, in which inverse polymerase chain reaction detected 2 common viral integration sites (CISs). Interestingly, one CIS was transgene's own promoter, which up-regulated p210BCR/ABL expression. The other was the 5' noncoding region of a transcription factor, Zfp423, which induced aberrant Zfp423 expression. The cooperative activities of Zfp423 and p210BCR/ABL were demonstrated as follows: (1) introduction of Zfp423 in p210BCR/ABL transgenic bone marrow (BM) cells increased colony-forming ability, (2) suppression of ZNF423 (human homologue of Zfp423) in ZNF423-expressing, p210BCR/ABL-positive hematopoietic cells retarded cell growth, (3) mice that received a transplant of BM cells transduced with Zfp423 and p210BCR/ABL developed acute leukemia, and (4) expression of ZNF423 was found in human BCR/ABL-positive cell lines and CML BC samples. These results demonstrate that enhanced expression of p210BCR/ABL and deregulated expression of Zfp423/ZNF423 contribute to CML BC.
Asunto(s)
Linfocitos B/patología , Crisis Blástica/genética , Proteínas de Unión al ADN/fisiología , Proteínas de Fusión bcr-abl/fisiología , Regulación Leucémica de la Expresión Génica , Leucemia Mielógena Crónica BCR-ABL Positiva/genética , Factores de Transcripción/fisiología , Animales , Northern Blotting , Southern Blotting , Western Blotting , Trasplante de Médula Ósea , Proliferación Celular , Ensayo de Unidades Formadoras de Colonias , Proteínas de Unión al ADN/antagonistas & inhibidores , Femenino , Citometría de Flujo , Reordenamiento Génico , Humanos , Leucemia Mielógena Crónica BCR-ABL Positiva/metabolismo , Leucemia Mielógena Crónica BCR-ABL Positiva/patología , Masculino , Ratones , Ratones Noqueados , Fenotipo , ARN Mensajero/genética , ARN Mensajero/metabolismo , ARN Interferente Pequeño/farmacología , Retroviridae , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Tasa de Supervivencia , Factores de Transcripción/antagonistas & inhibidores , Dedos de ZincRESUMEN
Ewing's sarcoma is a highly malignant bone tumor found in children and adolescents, and the origin of this malignancy is not well understood. Here, we introduced a Ewing's sarcoma-associated genetic fusion of the genes encoding the RNA-binding protein EWS and the transcription factor ETS (EWS-ETS) into a fraction of cells enriched for osteochondrogenic progenitors derived from the embryonic superficial zone (eSZ) of long bones collected from late gestational murine embryos. EWS-ETS fusions efficiently induced Ewing's sarcoma-like small round cell sarcoma formation by these cells. Analysis of the eSZ revealed a fraction of a precursor cells that express growth/differentiation factor 5 (Gdf5), the transcription factor Erg, and parathyroid hormone-like hormone (Pthlh), and selection of the Pthlh-positive fraction alone further enhanced EWS-ETS-dependent tumor induction. Genes downstream of the EWS-ETS fusion protein were quite transcriptionally active in eSZ cells, especially in regions in which the chromatin structure of the ETS-responsive locus was open. Inhibition of ß-catenin, poly (ADP-ribose) polymerase 1 (PARP1), or enhancer of zeste homolog 2 (EZH2) suppressed cell growth in a murine model of Ewing's sarcoma, suggesting the utility of the current system as a preclinical model. These results indicate that eSZ cells are highly enriched in precursors to Ewing's sarcoma and provide clues to the histogenesis of Ewing's sarcoma in bone.