RESUMO
Iroquois transcription factor gene IRX3 is highly expressed in 20-30% of acute myeloid leukemia (AML) and contributes to the pathognomonic differentiation block. Intron 8 FTO sequences â¼220kB downstream of IRX3 exhibit histone acetylation, DNA methylation, and contacts with the IRX3 promoter, which correlate with IRX3 expression. Deletion of these intronic elements confirms a role in positively regulating IRX3. RNAseq revealed long non-coding (lnc) transcripts arising from this locus. FTO-lncAML knockdown (KD) induced differentiation of AML cells, loss of clonogenic activity, and reduced FTO intron 8:IRX3 promoter contacts. While both FTO-lncAML KD and IRX3 KD induced differentiation, FTO-lncAML but not IRX3 KD led to HOXA downregulation suggesting transcript activity in trans. FTO-lncAMLhigh AML samples expressed higher levels of HOXA and lower levels of differentiation genes. Thus, a regulatory module in FTO intron 8 consisting of clustered enhancer elements and a long non-coding RNA is active in human AML, impeding myeloid differentiation.
RESUMO
Pharmacologic inhibition of LSD1 induces molecular and morphologic differentiation of blast cells in acute myeloid leukemia (AML) patients harboring MLL gene translocations. In addition to its demethylase activity, LSD1 has a critical scaffolding function at genomic sites occupied by the SNAG domain transcription repressor GFI1. Importantly, inhibitors block both enzymatic and scaffolding activities, in the latter case by disrupting the protein:protein interaction of GFI1 with LSD1. To explore the wider consequences of LSD1 inhibition on the LSD1 protein complex we applied mass spectrometry technologies. We discovered that the interaction of the HMG-box protein HMG20B with LSD1 was also disrupted by LSD1 inhibition. Downstream investigations revealed that HMG20B is co-located on chromatin with GFI1 and LSD1 genome-wide; the strongest HMG20B binding co-locates with the strongest GFI1 and LSD1 binding. Functional assays demonstrated that HMG20B depletion induces leukemia cell differentiation and further revealed that HMG20B is required for the transcription repressor activity of GFI1 through stabilizing LSD1 on chromatin at GFI1 binding sites. Interaction of HMG20B with LSD1 is through its coiled-coil domain. Thus, HMG20B is a critical component of the GFI1:LSD1 transcription repressor complex which contributes to leukemia cell differentiation block.
Assuntos
Histona Desmetilases , Leucemia Mieloide Aguda , Humanos , Diferenciação Celular/genética , Cromatina/genética , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Histona Desmetilases/metabolismo , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Despite absent expression in normal hematopoiesis, the Forkhead factor FOXC1, a critical mesenchymal differentiation regulator, is highly expressed in â¼30% of HOXAhigh acute myeloid leukemia (AML) cases to confer blocked monocyte/macrophage differentiation. Through integrated proteomics and bioinformatics, we find that FOXC1 and RUNX1 interact through Forkhead and Runt domains, respectively, and co-occupy primed and active enhancers distributed close to differentiation genes. FOXC1 stabilizes association of RUNX1, HDAC1, and Groucho repressor TLE3 to limit enhancer activity: FOXC1 knockdown induces loss of repressor proteins, gain of CEBPA binding, enhancer acetylation, and upregulation of nearby genes, including KLF2. Furthermore, it triggers genome-wide redistribution of RUNX1, TLE3, and HDAC1 from enhancers to promoters, leading to repression of self-renewal genes, including MYC and MYB. Our studies highlight RUNX1 and CEBPA transcription factor swapping as a feature of leukemia cell differentiation and reveal that FOXC1 prevents this by stabilizing enhancer binding of a RUNX1/HDAC1/TLE3 transcription repressor complex to oncogenic effect.
Assuntos
Diferenciação Celular , Proteínas Correpressoras/metabolismo , Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Proteínas Estimuladoras de Ligação a CCAAT/genética , Proteínas Estimuladoras de Ligação a CCAAT/metabolismo , Linhagem Celular Tumoral , Cromatina/metabolismo , Proteínas Correpressoras/genética , Subunidade alfa 2 de Fator de Ligação ao Core/química , Subunidade alfa 2 de Fator de Ligação ao Core/genética , Elementos Facilitadores Genéticos , Fatores de Transcrição Forkhead/antagonistas & inibidores , Fatores de Transcrição Forkhead/deficiência , Fatores de Transcrição Forkhead/genética , Histona Desacetilase 1/genética , Histona Desacetilase 1/metabolismo , Humanos , Fatores de Transcrição Kruppel-Like/genética , Fatores de Transcrição Kruppel-Like/metabolismo , Leucemia Mieloide Aguda/metabolismo , Leucemia Mieloide Aguda/patologia , Monócitos/citologia , Monócitos/metabolismo , Regiões Promotoras Genéticas , Ligação Proteica , Domínios Proteicos , Proteínas Proto-Oncogênicas c-myc/metabolismo , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Regulação para CimaRESUMO
Follicular lymphoma (FL) is incurable with conventional therapies and has a clinical course typified by multiple relapses after therapy. These tumors are genetically characterized by B-cell leukemia/lymphoma 2 (BCL2) translocation and mutation of genes involved in chromatin modification. By analyzing purified tumor cells, we identified additional novel recurrently mutated genes and confirmed mutations of one or more chromatin modifier genes within 96% of FL tumors and two or more in 76% of tumors. We defined the hierarchy of somatic mutations arising during tumor evolution by analyzing the phylogenetic relationship of somatic mutations across the coding genomes of 59 sequentially acquired biopsies from 22 patients. Among all somatically mutated genes, CREBBP mutations were most significantly enriched within the earliest inferable progenitor. These mutations were associated with a signature of decreased antigen presentation characterized by reduced transcript and protein abundance of MHC class II on tumor B cells, in line with the role of CREBBP in promoting class II transactivator (CIITA)-dependent transcriptional activation of these genes. CREBBP mutant B cells stimulated less proliferation of T cells in vitro compared with wild-type B cells from the same tumor. Transcriptional signatures of tumor-infiltrating T cells were indicative of reduced proliferation, and this corresponded to decreased frequencies of tumor-infiltrating CD4 helper T cells and CD8 memory cytotoxic T cells. These observations therefore implicate CREBBP mutation as an early event in FL evolution that contributes to immune evasion via decreased antigen presentation.
Assuntos
Células Apresentadoras de Antígenos/imunologia , Linfoma Folicular/genética , Mutação , Células-Tronco Neoplásicas/patologia , Proteína de Ligação a CREB/genética , Cromatina/metabolismo , Citometria de Fluxo , Antígenos de Histocompatibilidade Classe II/genética , Humanos , Linfoma Folicular/imunologia , Reação em Cadeia da PolimeraseRESUMO
Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma and can be separated into two subtypes based upon molecular features with similarities to germinal centre B-cells (GCB-like) or activated B-cells (ABC-like). Here we identify gain of 3q27.2 as being significantly associated with adverse outcome in DLBCL and linked with the ABC-like subtype. This lesion includes the BCL6 oncogene, but does not alter BCL6 transcript levels or target-gene repression. Separately, we identify expression of BCL6 in a subset of human haematopoietic stem/progenitor cells (HSPCs). We therefore hypothesize that BCL6 may act by 'hit-and-run' oncogenesis. We model this hit-and-run mechanism by transiently expressing Bcl6 within murine HSPCs, and find that it causes mature B-cell lymphomas that lack Bcl6 expression and target-gene repression, are transcriptionally similar to post-GCB cells, and show epigenetic changes that are conserved from HSPCs to mature B-cells. Together, these results suggest that BCL6 may function in a 'hit-and-run' role in lymphomagenesis.
Assuntos
Linfócitos B/metabolismo , Proteínas de Ligação a DNA/genética , Regulação Neoplásica da Expressão Gênica , Células-Tronco Hematopoéticas/metabolismo , Linfoma Difuso de Grandes Células B/genética , Animais , Anticorpos Monoclonais Murinos/uso terapêutico , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Ciclofosfamida/uso terapêutico , Variações do Número de Cópias de DNA , Metilação de DNA , Proteínas de Ligação a DNA/metabolismo , Doxorrubicina/uso terapêutico , Epigênese Genética , Feminino , Humanos , Linfoma Difuso de Grandes Células B/tratamento farmacológico , Linfoma Difuso de Grandes Células B/metabolismo , Masculino , Camundongos , Camundongos Transgênicos , Fenótipo , Prednisona/uso terapêutico , Prognóstico , Proteínas Proto-Oncogênicas c-bcl-6 , Rituximab , Vincristina/uso terapêuticoRESUMO
Tumour-associated oncogenes induce unscheduled proliferation as well as genomic and chromosomal instability. According to current models, therapeutic strategies that block oncogene activity are likely to selectively target tumour cells. However, recent evidences have revealed that oncogenes are only essential for the proliferation of some specific tumour cell types, but not all. Indeed, the latest studies of the interactions between the oncogene and its target cell have shown that oncogenes contribute to cancer development not only by inducing proliferation but also by developmental reprogramming of the epigenome. This provides the first evidence that tumorigenesis can be initiated by stem cell reprogramming, and uncovers a new role for oncogenes in the origin of cancer. Here we analyse these evidences and propose an updated model of oncogene function that can explain the full range of genotype-phenotype associations found in human cancer. Finally, we discuss how this vision opens new avenues for developing novel anti-cancer interventions.
Assuntos
Transformação Celular Neoplásica/genética , Estudos de Associação Genética , Neoplasias/genética , Oncogenes/fisiologia , Animais , Biologia Celular , Proliferação de Células , Transformação Celular Neoplásica/patologia , Instabilidade Cromossômica , Humanos , Camundongos , Modelos Biológicos , Mutação , Neoplasias/patologia , Neoplasias/terapia , Células-Tronco Neoplásicas , Oncogenes/genéticaRESUMO
The human germinal centre-associated lymphoma gene is specifically expressed in germinal centre B-lymphocytes and germinal centre-derived B-cell lymphomas, but its function is largely unknown. Here we demonstrate that human germinal centre-associated lymphoma directly binds to Syk in B cells, increases its kinase activity on B-cell receptor stimulation and leads to enhanced activation of Syk downstream effectors. To further investigate these findings in vivo, human germinal centre-associated lymphoma transgenic mice were generated. Starting from 12 months of age these mice developed polyclonal B-cell lymphoid hyperplasia, hypergammaglobulinemia and systemic reactive amyloid A (AA) amyloidosis, leading to shortened survival. The lymphoid hyperplasia in the human germinal centre-associated lymphoma transgenic mice are likely attributable to enhanced B-cell receptor signalling as shown by increased Syk phosphorylation, ex vivo B-cell proliferation and increased RhoA activation. Overall, our study shows for the first time that the germinal centre protein human germinal centre-associated lymphoma regulates B-cell receptor signalling in B-lymphocytes which, without appropriate control, may lead to B-cell lymphoproliferation.
Assuntos
Amiloidose/patologia , Centro Germinativo/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Linfoma de Células B/enzimologia , Linfoma de Células B/patologia , Proteínas de Neoplasias/metabolismo , Proteínas Tirosina Quinases/metabolismo , Receptores de Antígenos de Linfócitos B/metabolismo , Sequência de Aminoácidos , Amiloidose/complicações , Animais , Antígenos Ly/metabolismo , Extratos Celulares , Modelos Animais de Doenças , Ativação Enzimática , Centro Germinativo/patologia , Humanos , Hipergamaglobulinemia/patologia , Hiperplasia , Espaço Intracelular/metabolismo , Estimativa de Kaplan-Meier , Linfoma de Células B/complicações , Proteínas de Membrana/metabolismo , Camundongos , Proteínas dos Microfilamentos , Dados de Sequência Molecular , Ligação Proteica , RNA Interferente Pequeno/metabolismo , Proteína Amiloide A Sérica/química , Proteína Amiloide A Sérica/metabolismo , Transdução de Sinais , Baço/metabolismo , Baço/patologia , Quinase Syk , Transcriptoma/genética , Proteína rhoA de Ligação ao GTP/metabolismoAssuntos
Regulação Neoplásica da Expressão Gênica , Células-Tronco Hematopoéticas/patologia , Mieloma Múltiplo/genética , Mieloma Múltiplo/patologia , Plasmócitos/patologia , Animais , Heterogeneidade Genética , Células-Tronco Hematopoéticas/metabolismo , Humanos , Fator de Transcrição MafB/genética , Fator de Transcrição MafB/metabolismo , Camundongos , Mieloma Múltiplo/metabolismo , Plasmócitos/metabolismoRESUMO
Understanding the cellular origin of cancer can help to improve disease prevention and therapeutics. Human plasma cell neoplasias are thought to develop from either differentiated B cells or plasma cells. However, when the expression of Maf oncogenes (associated to human plasma cell neoplasias) is targeted to mouse B cells, the resulting animals fail to reproduce the human disease. Here, to explore early cellular changes that might take place in the development of plasma cell neoplasias, we engineered transgenic mice to express MafB in haematopoietic stem/progenitor cells (HS/PCs). Unexpectedly, we show that plasma cell neoplasias arise in the MafB-transgenic mice. Beyond their clinical resemblance to human disease, these neoplasias highly express genes that are known to be upregulated in human multiple myeloma. Moreover, gene expression profiling revealed that MafB-expressing HS/PCs were more similar to B cells and tumour plasma cells than to any other subset, including wild-type HS/PCs. Consistent with this, genome-scale DNA methylation profiling revealed that MafB imposes an epigenetic program in HS/PCs, and that this program is preserved in mature B cells of MafB-transgenic mice, demonstrating a novel molecular mechanism involved in tumour initiation. Our findings suggest that, mechanistically, the haematopoietic progenitor population can be the target for transformation in MafB-associated plasma cell neoplasias.
Assuntos
Regulação Neoplásica da Expressão Gênica , Fator de Transcrição MafB/metabolismo , Mieloma Múltiplo/metabolismo , Animais , Antígenos CD34/biossíntese , Antígenos Ly/metabolismo , Linfócitos B/metabolismo , Metilação de DNA , DNA Complementar/metabolismo , Epigênese Genética , Perfilação da Expressão Gênica , Biblioteca Gênica , Células-Tronco Hematopoéticas/citologia , Humanos , Hibridização in Situ Fluorescente , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Transgênicos , Mieloma Múltiplo/genética , Translocação GenéticaRESUMO
Chromosomal translocations involving the MALT1 gene are hallmarks of mucosa-associated lymphoid tissue (MALT) lymphoma. To date, targeting these translocations to mouse B cells has failed to reproduce human disease. Here, we induced MALT1 expression in mouse Sca1(+)Lin(-) hematopoietic stem/progenitor cells, which showed NF-κB activation and early lymphoid priming, being selectively skewed toward B-cell differentiation. These cells accumulated in extranodal tissues and gave rise to clonal tumors recapitulating the principal clinical, biological, and molecular genetic features of MALT lymphoma. Deletion of p53 gene accelerated tumor onset and induced transformation of MALT lymphoma to activated B-cell diffuse large-cell lymphoma (ABC-DLBCL). Treatment of MALT1-induced lymphomas with a specific inhibitor of MALT1 proteolytic activity decreased cell viability, indicating that endogenous Malt1 signaling was required for tumor cell survival. Our study shows that human-like lymphomas can be modeled in mice by targeting MALT1 expression to hematopoietic stem/progenitor cells, demonstrating the oncogenic role of MALT1 in lymphomagenesis. Furthermore, this work establishes a molecular link between MALT lymphoma and ABC-DLBCL, and provides mouse models to test MALT1 inhibitors. Finally, our results suggest that hematopoietic stem/progenitor cells may be involved in the pathogenesis of human mature B-cell lymphomas.
Assuntos
Caspases/genética , Células-Tronco Hematopoéticas/metabolismo , Linfoma/patologia , Proteínas de Neoplasias/genética , Oncogenes , Animais , Humanos , Camundongos , Camundongos Transgênicos , Proteína de Translocação 1 do Linfoma de Tecido Linfoide Associado à Mucosa , NF-kappa B/metabolismo , Transcrição GênicaAssuntos
Células-Tronco Neoplásicas/enzimologia , Telomerase/metabolismo , Animais , Antígenos Ly/genética , Transformação Celular Neoplásica , Modelos Animais de Doenças , Proteínas de Fusão bcr-abl/genética , Proteínas de Fusão bcr-abl/metabolismo , Humanos , Leucemia Mielogênica Crônica BCR-ABL Positiva/enzimologia , Leucemia Mielogênica Crônica BCR-ABL Positiva/metabolismo , Leucemia Mielogênica Crônica BCR-ABL Positiva/patologia , Proteínas de Membrana/genética , Camundongos , Regiões Promotoras GenéticasRESUMO
LMO2 regulates gene expression by facilitating the formation of multipartite DNA-binding complexes. In B cells, LMO2 is specifically up-regulated in the germinal center (GC) and is expressed in GC-derived non-Hodgkin lymphomas. LMO2 is one of the most powerful prognostic indicators in diffuse large B-cell (DLBCL) patients. However, its function in GC B cells and DLBCL is currently unknown. In this study, we characterized the LMO2 transcriptome and transcriptional complex in DLBCL cells. LMO2 regulates genes implicated in kinetochore function, chromosome assembly, and mitosis. Overexpression of LMO2 in DLBCL cell lines results in centrosome amplification. In DLBCL, the LMO2 complex contains some of the traditional partners, such as LDB1, E2A, HEB, Lyl1, ETO2, and SP1, but not TAL1 or GATA proteins. Furthermore, we identified novel LMO2 interacting partners: ELK1, nuclear factor of activated T-cells (NFATc1), and lymphoid enhancer-binding factor1 (LEF1) proteins. Reporter assays revealed that LMO2 increases transcriptional activity of NFATc1 and decreases transcriptional activity of LEF1 proteins. Overall, our studies identified a novel LMO2 transcriptome and interactome in DLBCL and provides a platform for future elucidation of LMO2 function in GC B cells and DLBCL pathogenesis.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Linfócitos B/metabolismo , Proteínas com Domínio LIM/genética , Linfoma Difuso de Grandes Células B/genética , Proteínas Proto-Oncogênicas/genética , Transcriptoma , Linfócitos B/patologia , Sequência de Bases , Linhagem Celular , Linhagem Celular Tumoral , Proliferação de Células , Centrossomo/ultraestrutura , Regulação Neoplásica da Expressão Gênica , Humanos , Linfoma Difuso de Grandes Células B/patologia , Dados de Sequência Molecular , Regiões Promotoras Genéticas , RNA Longo não Codificante , Transferases , Proteínas Supressoras de Tumor/genéticaRESUMO
The telomerase protein is constitutively activated in malignant cells from many patients with cancer, including the chronic myeloid leukemia (CML), but whether telomerase is essential for the pathogenesis of this disease is not known. Here, we used telomerase deficient mice to determine the requirement for telomerase in CML induced by BCR-ABL in mouse models of CML. Loss of one telomerase allele or complete deletion of telomerase prevented the development of leukemia induced by BCR-ABL. However, BCR-ABL was expressed and active in telomerase heterozygous and null leukemic hematopoietic stem cells. These results demonstrate that telomerase is essential for oncogene-induced reprogramming of hematopoietic stem cells in CML development and validate telomerase and the genes it regulates as targets for therapy in CML.
Assuntos
Transformação Celular Neoplásica/genética , Proteínas de Fusão bcr-abl/fisiologia , Leucemia Mielogênica Crônica BCR-ABL Positiva/genética , Telomerase/fisiologia , Animais , Antígenos Ly/genética , Proliferação de Células , Sobrevivência Celular , Transformação Celular Neoplásica/patologia , Modelos Animais de Doenças , Proteínas de Fusão bcr-abl/genética , Células-Tronco Hematopoéticas/metabolismo , Células-Tronco Hematopoéticas/patologia , Leucemia Mielogênica Crônica BCR-ABL Positiva/patologia , Proteínas de Membrana/genética , Camundongos , Camundongos Transgênicos , Células-Tronco Neoplásicas/metabolismo , Células-Tronco Neoplásicas/patologia , Células-Tronco Neoplásicas/fisiologia , Telomerase/genética , Telomerase/metabolismo , TransfecçãoRESUMO
Cancer is the subject of intense research around the world, but many questions about how the disease works remain unanswered. How exactly does cancer start and how do tumours grow? In fact, at present there are ten times more anticancer drugs being tested in clinical trials than there were 15 years ago. However, many of the new anticancer agents are predicted to show clinical benefit in only small subpopulations of patients. The cancer stem cell model could explain not only how some cancers work but also why patients suffer relapses, providing a good opportunity to gain insight into the reasons why agents work or, more commonly, don't work, before going into a clinical trial.
Assuntos
Antineoplásicos/uso terapêutico , Desenho de Fármacos , Neoplasias/tratamento farmacológico , Projetos de Pesquisa , Animais , Modelos Animais de Doenças , Sistemas de Liberação de Medicamentos/métodos , Humanos , CamundongosRESUMO
The latest scientific findings in the field of cancer research are redefining our understanding of the molecular and cellular basis of the disease, moving the emphasis toward the study of the mechanisms underlying the alteration of the normal processes of cellular differentiation. The concepts best exemplifying this new vision are those of cancer stem cells and tumoral reprogramming. The study of the biology of acute lymphoblastic leukemias (ALLs) has provided seminal experimental evidence supporting these new points of view. Furthermore, in the case of B cells, it has been shown that all the stages of their normal development show a tremendous degree of plasticity, allowing them to be reprogrammed to other cellular types, either normal or leukemic. Here we revise the most recent discoveries in the fields of B-cell developmental plasticity and B-ALL research and discuss their interrelationships and their implications for our understanding of the biology of the disease.