RESUMO
Chromosome translocations involving the MLL gene are common rearrangements in leukemia. Such translocations fuse the MLL 5'-region to partner genes in frame, producing MLL-fusions that cause MLL-related leukemia. MLL-fusions activate transcription of target genes such as HoxA cluster and Meis1, but the underlying mechanisms remain to be fully elucidated. In this study, we discovered that Tip60, a MYST-type histone acetyltransferase, was required for the expression of HoxA cluster and Meis1 genes and the development of MLL-fusion leukemia. Tip60 was recruited by MLL-AF10 and MLL-ENL fusions to the Hoxa9 locus, where it acetylated H2A.Z, thereby promoting Hoxa9 gene expression. Conditional deletion of Tip60 prevented the development of MLL-AF10 and MLL-ENL leukemia, indicating that Tip60 is indispensable for the leukemogenic activity of the MLL-AF10 and MLL-ENL-fusions. Our findings provide novel insight about epigenetic regulation in the development of MLL-AF10 and MLL-ENL-fusion leukemia.
Assuntos
Histonas/metabolismo , Proteínas de Homeodomínio/metabolismo , Leucemia Mieloide Aguda/patologia , Lisina Acetiltransferase 5/metabolismo , Proteína Meis1/metabolismo , Proteína de Leucina Linfoide-Mieloide/metabolismo , Proteínas de Fusão Oncogênica/metabolismo , Acetilação , Animais , Epigênese Genética , Regulação Leucêmica da Expressão Gênica , Rearranjo Gênico , Histonas/genética , Proteínas de Homeodomínio/genética , Humanos , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/metabolismo , Lisina Acetiltransferase 5/genética , Camundongos , Proteína Meis1/genética , Proteína de Leucina Linfoide-Mieloide/genética , Proteínas de Fusão Oncogênica/genética , Translocação GenéticaRESUMO
Eradication of chemotherapy-resistant leukemia stem cells is expected to improve treatment outcomes in patients with acute myelogenous leukemia (AML). In a mouse model of AML expressing the MOZ-TIF2 fusion, we found that Ring1A and Ring1B, components of Polycomb repressive complex 1, play crucial roles in maintaining AML stem cells. Deletion of Ring1A and Ring1B (Ring1A/B) from MOZ-TIF2 AML cells diminished self-renewal capacity and induced the expression of numerous genes, including Glis2 Overexpression of Glis2 caused MOZ-TIF2 AML cells to differentiate into mature cells, whereas Glis2 knockdown in Ring1A/B-deficient MOZ-TIF2 cells inhibited differentiation. Thus, Ring1A/B regulate and maintain AML stem cells in part by repressing Glis2 expression, which promotes their differentiation. These findings provide new insights into the mechanism of AML stem cell homeostasis and reveal novel targets for cancer stem cell therapy.
Assuntos
Regulação Leucêmica da Expressão Gênica , Histona Acetiltransferases/biossíntese , Fatores de Transcrição Kruppel-Like/biossíntese , Leucemia Mieloide Aguda/metabolismo , Proteínas do Tecido Nervoso/biossíntese , Coativador 2 de Receptor Nuclear/biossíntese , Proteínas de Fusão Oncogênica/biossíntese , Complexo Repressor Polycomb 1/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Animais , Diferenciação Celular , Histona Acetiltransferases/genética , Fatores de Transcrição Kruppel-Like/genética , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patologia , Camundongos , Camundongos Knockout , Proteínas do Tecido Nervoso/genética , Coativador 2 de Receptor Nuclear/genética , Proteínas de Fusão Oncogênica/genética , Complexo Repressor Polycomb 1/genética , Ubiquitina-Proteína Ligases/genéticaRESUMO
Acute myeloid leukemia is a clonal malignant disorder derived from a small number of leukemic stem cells (LSCs). Rearrangements of the mixed lineage leukemia (MLL) gene are found in acute myeloid leukemia associated with poor prognosis. The upregulation of Hox genes is critical for LSC induction and maintenance, but is unlikely to support malignancy and the high LSC frequency observed in MLL leukemias. The present study shows that MLL fusion proteins interact with the transcription factor PU.1 to activate the transcription of CSF-1R, which is critical for LSC activity. Acute myeloid leukemia is cured by either deletion of PU.1 or ablation of cells expressing CSF-1R. Kinase inhibitors specific for CSF-1R prolong survival time. These findings indicate that PU.1-mediated upregulation of CSF-1R is a critical effector of MLL leukemogenesis.
Assuntos
Carcinogênese/genética , Histona-Lisina N-Metiltransferase/genética , Leucemia Mieloide Aguda/genética , Proteína de Leucina Linfoide-Mieloide/genética , Proteínas Proto-Oncogênicas/genética , Receptor de Fator Estimulador de Colônias de Macrófagos/genética , Transativadores/genética , Animais , Regulação Leucêmica da Expressão Gênica , Genes Homeobox , Leucemia Mieloide Aguda/mortalidade , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Células-Tronco Neoplásicas , Compostos de Fenilureia/farmacologia , Prognóstico , Receptor de Fator Estimulador de Colônias de Macrófagos/biossíntese , Proteínas Recombinantes de Fusão/genética , Transdução de Sinais , Tacrolimo/análogos & derivados , Tacrolimo/farmacologia , Tiazóis/farmacologia , Transcrição Gênica , Ativação Transcricional , Regulação para CimaRESUMO
The CALM-AF10 fusion gene, which results from a t(10;11) translocation, is found in a variety of hematopoietic malignancies. Certain HOXA cluster genes and MEIS1 genes are upregulated in patients and mouse models that express CALM-AF10. Wild-type clathrin assembly lymphoid myeloid leukemia protein (CALM) primarily localizes in a diffuse pattern within the cytoplasm, whereas AF10 localizes in the nucleus; however, it is not clear where CALM-AF10 acts to induce leukemia. To investigate the influence of localization on leukemogenesis involving CALM-AF10, we determined the nuclear export signal (NES) within CALM that is necessary and sufficient for cytoplasmic localization of CALM-AF10. Mutations in the NES eliminated the capacity of CALM-AF10 to immortalize murine bone-marrow cells in vitro and to promote development of acute myeloid leukemia in mouse models. Furthermore, a fusion of AF10 with the minimal NES can immortalize bone-marrow cells and induce leukemia in mice. These results suggest that during leukemogenesis, CALM-AF10 plays its critical roles in the cytoplasm.
Assuntos
Leucemia/metabolismo , Proteínas Monoméricas de Montagem de Clatrina/fisiologia , Proteínas de Fusão Oncogênica/fisiologia , Fatores de Transcrição/fisiologia , Sequência de Aminoácidos , Animais , Células COS , Carcinogênese/genética , Carcinogênese/metabolismo , Chlorocebus aethiops , Feminino , Leucemia/genética , Leucemia/patologia , Camundongos , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Proteínas Monoméricas de Montagem de Clatrina/química , Transplante de Neoplasias , Sinais de Exportação Nuclear , Células Tumorais CultivadasRESUMO
Chromosomal translocations that involve the monocytic leukemia zinc finger (MOZ) gene are typically associated with human acute myeloid leukemia (AML) and often predict a poor prognosis. Overexpression of HOXA9, HOXA10, and MEIS1 was observed in AML patients with MOZ fusions. To assess the functional role of HOX upregulation in leukemogenesis by MOZ-TIF2, we focused on bromodomain-PHD finger protein 1 (BRPF1), a component of the MOZ complex that carries out histone acetylation for generating and maintaining proper epigenetic programs in hematopoietic cells. Immunoprecipitation analysis showed that MOZ-TIF2 forms a stable complex with BRPF1, and chromatin immunoprecipitation analysis showed that MOZ-TIF2 and BRPF1 interact with HOX genes in MOZ-TIF2-induced AML cells. Depletion of BRPF1 decreased the MOZ localization on HOX genes, resulting in loss of transformation ability induced by MOZ-TIF2. Furthermore, mutant MOZ-TIF2 engineered to lack histone acetyltransferase activity was incapable of deregulating HOX genes as well as initiating leukemia. These data indicate that MOZ-TIF2/BRPF1 complex upregulates HOX genes mediated by MOZ-dependent histone acetylation, leading to the development of leukemia. We suggest that activation of BRPF1/HOX pathway through MOZ HAT activity is critical for MOZ-TIF2 to induce AML.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Transformação Celular Neoplásica/genética , Leucemia/genética , Proteínas Nucleares/genética , Proteínas de Fusão Oncogênica/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Sequência de Aminoácidos , Animais , Linhagem Celular Tumoral , Transformação Celular Neoplásica/metabolismo , Proteínas de Ligação a DNA , Modelos Animais de Doenças , Expressão Gênica , Técnicas de Silenciamento de Genes , Histona Acetiltransferases/química , Histona Acetiltransferases/genética , Histona Acetiltransferases/metabolismo , Proteínas Homeobox A10 , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Humanos , Leucemia/metabolismo , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/metabolismo , Camundongos , Dados de Sequência Molecular , Proteínas Nucleares/metabolismo , Proteínas de Fusão Oncogênica/metabolismo , Ligação Proteica , Domínios e Motivos de Interação entre ProteínasRESUMO
Leukemias and other cancers possess self-renewing stem cells that help to maintain the cancer. Cancer stem cell eradication is thought to be crucial for successful anticancer therapy. Using an acute myeloid leukemia (AML) model induced by the leukemia-associated monocytic leukemia zinc finger (MOZ)-TIF2 fusion protein, we show here that AML can be cured by the ablation of leukemia stem cells. The MOZ fusion proteins MOZ-TIF2 and MOZ-CBP interacted with the transcription factor PU.1 to stimulate the expression of macrophage colony-stimulating factor receptor (CSF1R, also known as M-CSFR, c-FMS or CD115). Studies using PU.1-deficient mice showed that PU.1 is essential for the ability of MOZ-TIF2 to establish and maintain AML stem cells. Cells expressing high amounts of CSF1R (CSF1R(high) cells), but not those expressing low amounts of CSF1R (CSF1R(low) cells), showed potent leukemia-initiating activity. Using transgenic mice expressing a drug-inducible suicide gene controlled by the CSF1R promoter, we cured AML by ablation of CSF1R(high) cells. Moreover, induction of AML was suppressed in CSF1R-deficient mice and CSF1R inhibitors slowed the progression of MOZ-TIF2-induced leukemia. Thus, in this subtype of AML, leukemia stem cells are contained within the CSF1R(high) cell population, and we suggest that targeting of PU.1-mediated upregulation of CSF1R expression might be a useful therapeutic approach.
