RESUMO
The fusion oncoprotein CBFß-SMMHC, expressed in leukemia cases with chromosome 16 inversion, drives leukemia development and maintenance by altering the activity of the transcription factor RUNX1. Here, we demonstrate that CBFß-SMMHC maintains cell viability by neutralizing RUNX1-mediated repression of MYC expression. Upon pharmacologic inhibition of the CBFß-SMMHC/RUNX1 interaction, RUNX1 shows increased binding at three MYC distal enhancers, where it represses MYC expression by mediating the replacement of the SWI/SNF complex component BRG1 with the polycomb-repressive complex component RING1B, leading to apoptosis. Combining the CBFß-SMMHC inhibitor with the BET inhibitor JQ1 eliminates inv(16) leukemia in human cells and a mouse model. Enhancer-interaction analysis indicated that the three enhancers are physically connected with the MYC promoter, and genome-editing analysis demonstrated that they are functionally implicated in deregulation of MYC expression. This study reveals a mechanism whereby CBFß-SMMHC drives leukemia maintenance and suggests that inhibitors targeting chromatin activity may prove effective in inv(16) leukemia therapy.
Assuntos
Apoptose , Cromatina/metabolismo , Proteínas de Fusão Oncogênica/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-myc/metabolismo , Animais , Apoptose/efeitos dos fármacos , Azepinas/farmacologia , Azepinas/uso terapêutico , Benzimidazóis/farmacologia , Benzimidazóis/uso terapêutico , Linhagem Celular Tumoral , Proteínas Cromossômicas não Histona/química , Proteínas Cromossômicas não Histona/metabolismo , Inversão Cromossômica/efeitos dos fármacos , Subunidade alfa 2 de Fator de Ligação ao Core/química , Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , DNA/química , DNA/metabolismo , DNA Helicases/metabolismo , Modelos Animais de Doenças , Humanos , Estimativa de Kaplan-Meier , Leucemia Mieloide Aguda/tratamento farmacológico , Leucemia Mieloide Aguda/mortalidade , Leucemia Mieloide Aguda/patologia , Camundongos , Camundongos Endogâmicos C57BL , Proteínas Nucleares/metabolismo , Proteínas de Fusão Oncogênica/metabolismo , Complexo Repressor Polycomb 1/metabolismo , Regiões Promotoras Genéticas , Ligação Proteica , Proteínas Proto-Oncogênicas c-myc/genética , Fatores de Transcrição/química , Fatores de Transcrição/metabolismo , Triazóis/farmacologia , Triazóis/uso terapêuticoRESUMO
Oncogenic mutations in components of cytokine signaling pathways elicit ligand-independent activation of downstream signaling, enhancing proliferation and survival in acute myeloid leukemia (AML). The myeloproliferative leukemia virus oncogene, MPL, a homodimeric receptor activated by thrombopoietin (THPO), is mutated in myeloproliferative disorders but rarely in AML. Here we show that wild-type MPL expression is increased in a fraction of human AML samples expressing RUNX1-ETO, a fusion protein created by chromosome translocation t(8;21), and that up-regulation of Mpl expression in mice induces AML when coexpressed with RUNX1-ETO. The leukemic cells are sensitive to THPO, activating survival and proliferative responses. Mpl expression is not regulated by RUNX1-ETO in mouse hematopoietic progenitors or leukemic cells. Moreover, we find that activation of PI3K/AKT but not ERK/MEK pathway is a critical mediator of the MPL-directed antiapoptotic function in leukemic cells. Hence, this study provides evidence that up-regulation of wild-type MPL levels promotes leukemia development and maintenance through activation of the PI3K/AKT axis, and suggests that inhibitors of this axis could be effective for treatment of MPL-positive AML.
Assuntos
Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Leucemia Mieloide Aguda/metabolismo , Leucemia Mieloide Aguda/patologia , Proteínas de Fusão Oncogênica/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Receptores de Trombopoetina/metabolismo , Trombopoetina/metabolismo , Sequência de Aminoácidos , Animais , Western Blotting , Medula Óssea/metabolismo , Medula Óssea/patologia , Transplante de Medula Óssea , Ciclo Celular , Proliferação de Células , Cromossomos Humanos Par 21/genética , Cromossomos Humanos Par 8/genética , Subunidade alfa 2 de Fator de Ligação ao Core/genética , Humanos , Técnicas Imunoenzimáticas , Leucemia Mieloide Aguda/genética , Camundongos , Dados de Sequência Molecular , Proteínas de Fusão Oncogênica/genética , Fosfatidilinositol 3-Quinases/genética , Proteínas Proto-Oncogênicas c-akt/genética , RNA Mensageiro/genética , Proteína 1 Parceira de Translocação de RUNX1 , Reação em Cadeia da Polimerase em Tempo Real , Receptores de Trombopoetina/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais , Taxa de Sobrevida , Trombopoetina/genética , Translocação Genética , Células Tumorais CultivadasRESUMO
Acute myeloid leukemia (AML) is a collection of hematologic malignancies with specific driver mutations that direct the pathology of the disease. The understanding of the origin and function of these mutations at early stages of transformation is critical to understand the etiology of the disease and for the design of effective therapies. The chromosome inversion inv(16) is thought to arise as a founding mutation in a hematopoietic stem cell (HSC) to produce preleukemic HSCs (preL-HSCs) with myeloid bias and differentiation block, and predisposed to AML. Studies in mice and human AML cells have established that inv(16) AML follows a clonal evolution model, in which preL-HSCs expressing the fusion protein CBFß-SMMHC persist asymptomatic in the bone marrow. The emerging leukemia-initiating cells (LICs) are composed by the inv(16) and a heterogeneous set of mutations. In this review, we will discuss the current understanding of inv(16) preleukemia development, and the function of CBFß-SMMHC related to preleukemia progression and LIC activity. We also discuss important open mechanistic questions in the etiology of inv(16) AML.
RESUMO
Runx1 participation in epithelial mammary cells is still under review. Emerging data indicates that Runx1 could be relevant for breast tumor promotion. However, to date no studies have specifically evaluated the functional contribution of Runx1 to control gene expression in mammary epithelial tumor cells. It has been described that Runx1 activity is defined by protein context interaction. Interestingly, Foxp3 is a breast tumor suppressor gene. Here we show that endogenous Runx1 and Foxp3 physically interact in normal mammary cells and this interaction blocks Runx1 transcriptional activity. Furthermore we demonstrate that Runx1 is able to bind to R-spondin 3 (RSPO3) and Gap Junction protein Alpha 1 (GJA1) promoters. This binding upregulates Rspo3 oncogene expression and downregulates GJA1 tumor suppressor gene expression in a Foxp3-dependent manner. Moreover, reduced Runx1 transcriptional activity decreases tumor cell migration properties. Collectively, these data provide evidence of a new mechanism for breast tumor gene expression regulation, in which Runx1 and Foxp3 physically interact to control mammary epithelial cell gene expression fate. Our work suggests for the first time that Runx1 could be involved in breast tumor progression depending on Foxp3 availability.