RESUMEN
MLL/KMT2A amplifications and translocations are prevalent in infant, adult, and therapy-induced leukemia. However, the molecular contributor(s) to these alterations are unclear. Here, we demonstrate that histone H3 lysine 9 mono- and di-methylation (H3K9me1/2) balance at the MLL/KMT2A locus regulates these amplifications and rearrangements. This balance is controlled by the crosstalk between lysine demethylase KDM3B and methyltransferase G9a/EHMT2. KDM3B depletion increases H3K9me1/2 levels and reduces CTCF occupancy at the MLL/KMT2A locus, in turn promoting amplification and rearrangements. Depleting CTCF is also sufficient to generate these focal alterations. Furthermore, the chemotherapy doxorubicin (Dox), which associates with therapy-induced leukemia and promotes MLL/KMT2A amplifications and rearrangements, suppresses KDM3B and CTCF protein levels. KDM3B and CTCF overexpression rescues Dox-induced MLL/KMT2A alterations. G9a inhibition in human cells or mice also suppresses MLL/KMT2A events accompanying Dox treatment. Therefore, MLL/KMT2A amplifications and rearrangements are controlled by epigenetic regulators that are tractable drug targets, which has clinical implications.
Asunto(s)
Epigénesis Genética , Proteína de la Leucemia Mieloide-Linfoide , Adulto , Animales , Humanos , Lactante , Ratones , Doxorrubicina/farmacología , Reordenamiento Génico , Antígenos de Histocompatibilidad , N-Metiltransferasa de Histona-Lisina/genética , N-Metiltransferasa de Histona-Lisina/metabolismo , Histona Demetilasas con Dominio de Jumonji/genética , Histona Demetilasas con Dominio de Jumonji/metabolismo , Leucemia/metabolismo , Lisina/metabolismo , Proteína de la Leucemia Mieloide-Linfoide/genética , Translocación GenéticaRESUMEN
Germinal center (GC) B cells feature repression of many gene enhancers to establish their characteristic transcriptome. Here we show that conditional deletion of Lsd1 in GCs significantly impaired GC formation, associated with failure to repress immune synapse genes linked to GC exit, which are also direct targets of the transcriptional repressor BCL6. We found that BCL6 directly binds LSD1 and recruits it primarily to intergenic and intronic enhancers. Conditional deletion of Lsd1 suppressed GC hyperplasia caused by constitutive expression of BCL6 and significantly delayed BCL6-driven lymphomagenesis. Administration of catalytic inhibitors of LSD1 had little effect on GC formation or GC-derived lymphoma cells. Using a CRISPR-Cas9 domain screen, we found instead that the LSD1 Tower domain was critical for dependence on LSD1 in GC-derived B cells. These results indicate an essential role for LSD1 in the humoral immune response, where it modulates enhancer function by forming repression complexes with BCL6.
Asunto(s)
Linfocitos B/fisiología , Centro Germinal/patología , Histona Demetilasas/metabolismo , Linfoma/metabolismo , Proteínas Proto-Oncogénicas c-bcl-6/metabolismo , Animales , Sistemas CRISPR-Cas , Carcinogénesis , ADN Intergénico/genética , Centro Germinal/inmunología , Histona Demetilasas/genética , Hiperplasia , Sinapsis Inmunológicas/genética , Intrones/genética , Linfoma/genética , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas Proto-Oncogénicas c-bcl-6/genéticaRESUMEN
At the pre-B cell receptor (BCR) checkpoint, developing pre-B cells are selected for successful rearrangement of V(H)-DJ(H) gene segments and expression of a pre-BCR. Reduced stringency at this checkpoint may obstruct the B cell repertoire with nonfunctional B cell clones. Earlier studies have described that activation of B cell lymphoma/leukemia (BCL)6 by a functional pre-BCR mediates positive selection of pre-B cells that have passed the checkpoint. This concept is now further elaborated by the recent finding that the BTB and CNC homology 1 basic leucine zipper transcription factor 2 (BACH2) induces negative selection and opposes BCL6 function prior to the pre-BCR checkpoint. Here, we discuss the antagonism between BCL6 and BACH2 during early B cell development, as well as its implications in both repertoire selection and counter-selection of premalignant clones for leukemia suppression.
Asunto(s)
Linfocitos B/citología , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/metabolismo , Proteínas de Unión al ADN/metabolismo , Receptores de Células Precursoras de Linfocitos B/metabolismo , Células Precursoras de Linfocitos B/citología , Animales , Linfocitos B/inmunología , Linfocitos B/metabolismo , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/inmunología , Transformación Celular Neoplásica/inmunología , Transformación Celular Neoplásica/metabolismo , Proteínas de Unión al ADN/inmunología , Humanos , Linfoma de Células B/metabolismo , Receptores de Células Precursoras de Linfocitos B/inmunología , Células Precursoras de Linfocitos B/inmunología , Células Precursoras de Linfocitos B/metabolismo , Proteínas Proto-Oncogénicas c-bcl-6RESUMEN
Tyrosine kinase inhibitors (TKIs) are widely used to treat patients with leukaemia driven by BCR-ABL1 (ref. 1) and other oncogenic tyrosine kinases. Recent efforts have focused on developing more potent TKIs that also inhibit mutant tyrosine kinases. However, even effective TKIs typically fail to eradicate leukaemia-initiating cells (LICs), which often cause recurrence of leukaemia after initially successful treatment. Here we report the discovery of a novel mechanism of drug resistance, which is based on protective feedback signalling of leukaemia cells in response to treatment with TKI. We identify BCL6 as a central component of this drug-resistance pathway and demonstrate that targeted inhibition of BCL6 leads to eradication of drug-resistant and leukaemia-initiating subclones.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Resistencia a Antineoplásicos , Proteínas de Fusión bcr-abl/antagonistas & inhibidores , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamiento farmacológico , Leucemia-Linfoma Linfoblástico de Células Precursoras/patología , Inhibidores de Proteínas Quinasas/farmacología , Factor 1 de Ribosilacion-ADP/metabolismo , Animales , Supervivencia Celular/efectos de los fármacos , Proteínas de Unión al ADN/biosíntesis , Proteínas de Unión al ADN/deficiencia , Proteínas de Unión al ADN/genética , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Ratones , Ratones Endogámicos NOD , Ratones SCID , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/metabolismo , Inhibidores de Proteínas Quinasas/uso terapéutico , Proteínas Proto-Oncogénicas c-bcl-6 , Transcripción Genética , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
The Philadelphia chromosome (Ph) encoding the oncogenic BCR-ABL1 kinase defines a subset of acute lymphoblastic leukemia (ALL) with a particularly unfavorable prognosis. ALL cells are derived from B cell precursors in most cases and typically carry rearranged immunoglobulin heavy chain (IGH) variable (V) region genes devoid of somatic mutations. Somatic hypermutation is restricted to mature germinal center B cells and depends on activation-induced cytidine deaminase (AID). Studying AID expression in 108 cases of ALL, we detected AID mRNA in 24 of 28 Ph(+) ALLs as compared with 6 of 80 Ph(-) ALLs. Forced expression of BCR-ABL1 in Ph(-) ALL cells and inhibition of the BCR-ABL1 kinase showed that aberrant expression of AID depends on BCR-ABL1 kinase activity. Consistent with aberrant AID expression in Ph(+) ALL, IGH V region genes and BCL6 were mutated in many Ph(+) but unmutated in most Ph(-) cases. In addition, AID introduced DNA single-strand breaks within the tumor suppressor gene CDKN2B in Ph(+) ALL cells, which was sensitive to BCR-ABL1 kinase inhibition and silencing of AID expression by RNA interference. These findings identify AID as a BCR-ABL1-induced mutator in Ph(+) ALL cells, which may be relevant with respect to the particularly unfavorable prognosis of this leukemia subset.
Asunto(s)
Linfocitos B/inmunología , Citidina Desaminasa/metabolismo , Regulación Neoplásica de la Expresión Génica/inmunología , Cromosoma Filadelfia , Leucemia-Linfoma Linfoblástico de Células Precursoras/inmunología , Proteínas Tirosina Quinasas/genética , Linfocitos B/metabolismo , Secuencia de Bases , Western Blotting , Análisis Mutacional de ADN , Proteínas de Unión al ADN/genética , Citometría de Flujo , Proteínas de Fusión bcr-abl , Genes myc/genética , Humanos , Región Variable de Inmunoglobulina/genética , Datos de Secuencia Molecular , Mutación/genética , Análisis de Secuencia por Matrices de Oligonucleótidos , Oligonucleótidos , Leucemia-Linfoma Linfoblástico de Células Precursoras/metabolismo , Proteínas Tirosina Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-bcl-6 , Interferencia de ARN , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Alineación de SecuenciaRESUMEN
Initial cell surface expression of the pre-B cell receptor induces proliferation. After 2 to 5 divisions, however, large pre-BII (Fraction C') cells exit cell cycle to become resting, small pre-BII cells (Fraction D). The mechanism by which pre-BII cells exit cell cycle, however, is currently unclear. The checkpoint at the Fraction C'-D transition is critical for immunoglobulin light chain gene recombination and to prevent malignant transformation into acute lymphoblastic leukemia. Here we demonstrate that inducible activation of pre-B cell receptor signaling induces cell-cycle exit through up-regulation of the transcriptional repressor BCL6. Inducible activation of BCL6 downstream of the pre-B cell receptor results in transcriptional repression of MYC and CCND2. Hence, pre-B cell receptor-mediated activation of BCL6 limits pre-B cell proliferation and induces cellular quiescence at the small pre-BII (Fraction D) stage.
Asunto(s)
Puntos de Control del Ciclo Celular/fisiología , División Celular/fisiología , Proteínas de Unión al ADN/biosíntesis , Receptores de Células Precursoras de Linfocitos B/metabolismo , Células Precursoras de Linfocitos B/metabolismo , Proteínas Proto-Oncogénicas c-myc/biosíntesis , Transcripción Genética/fisiología , Animales , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/metabolismo , Ciclina D2/genética , Ciclina D2/metabolismo , Proteínas de Unión al ADN/genética , Reordenamiento Génico de Cadena Ligera de Linfocito B/fisiología , Cadenas Ligeras de Inmunoglobulina/genética , Cadenas Ligeras de Inmunoglobulina/metabolismo , Ratones , Ratones Noqueados , Receptores de Células Precursoras de Linfocitos B/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/metabolismo , Células Precursoras de Linfocitos B/citología , Proteínas Proto-Oncogénicas c-bcl-6 , Proteínas Proto-Oncogénicas c-myc/genética , Transducción de Señal/fisiologíaRESUMEN
Oncogenic mutations in isocitrate dehydrogenase 1 (IDH1) and IDH2 occur in a wide range of cancers, including acute myeloid leukemia (AML) and glioma. Mutant IDH enzymes convert 2-oxoglutarate (2OG) to (R)-2-hydroxyglutarate [(R)-2HG], an oncometabolite that is hypothesized to promote cellular transformation by dysregulating 2OG-dependent enzymes. The only (R)-2HG target that has been convincingly shown to contribute to transformation by mutant IDH is the myeloid tumor suppressor TET2. However, there is ample evidence to suggest that (R)-2HG has other functionally relevant targets in IDH-mutant cancers. Here, we show that (R)-2HG inhibits KDM5 histone lysine demethylases and that this inhibition contributes to cellular transformation in IDH-mutant AML and IDH-mutant glioma. These studies provide the first evidence of a functional link between dysregulation of histone lysine methylation and transformation in IDH-mutant cancers. SIGNIFICANCE: Mutant IDH is known to induce histone hypermethylation. However, it is not known if this hypermethylation is functionally significant or is a bystander effect of (R)-2HG accumulation in IDH-mutant cells. Here, we provide evidence that KDM5 inhibition by (R)-2HG contributes to mutant IDH-mediated transformation in AML and glioma. This article is highlighted in the In This Issue feature, p. 1275.
Asunto(s)
Glioma , Leucemia Mieloide Aguda , Humanos , Histonas/metabolismo , Histona Demetilasas/genética , Mutación , Glutaratos , Transformación Celular Neoplásica/genética , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patología , Glioma/genética , Metilación de ADN , Isocitrato Deshidrogenasa/genética , Isocitrato Deshidrogenasa/metabolismoRESUMEN
Diffuse large B-cell lymphomas (DLBCL) are broadly dependent on anaplerotic metabolism regulated by mitochondrial SIRT3. Herein we find that translational upregulation of ATF4 is coupled with anaplerotic metabolism in DLBCLs due to nutrient deprivation caused by SIRT3 driving rapid flux of glutamine into the tricarboxylic acid (TCA) cycle. SIRT3 depletion led to ATF4 downregulation and cell death, which was rescued by ectopic ATF4 expression. Mechanistically, ATF4 translation is inhibited in SIRT3-deficient cells due to the increased pools of amino acids derived from compensatory autophagy and decreased glutamine consumption by the TCA cycle. Absence of ATF4 further aggravates this state through downregulation of its target genes, including genes for amino acid biosynthesis and import. Collectively, we identify a SIRT3-ATF4 axis required to maintain survival of DLBCL cells by enabling them to optimize amino acid uptake and utilization. Targeting ATF4 translation can potentiate the cytotoxic effect of SIRT3 inhibitor to DLBCL cells. SIGNIFICANCE: We discovered the link between SIRT3 and ATF4 in DLBCL cells, which connected lymphoma amino acid metabolism with ATF4 translation via metabolic stress signals. SIRT3-ATF4 axis is required in DLBCL cells regardless of subtype, which indicates a common metabolic vulnerability in DLBCLs and can serve as a therapeutic target.This article is highlighted in the In This Issue feature, p. 1.
Asunto(s)
Linfoma de Células B Grandes Difuso , Sirtuina 3 , Factor de Transcripción Activador 4/genética , Aminoácidos/metabolismo , Ciclo del Ácido Cítrico , Glutamina/metabolismo , Humanos , Linfoma de Células B Grandes Difuso/genética , Mitocondrias/metabolismo , Sirtuina 3/genéticaRESUMEN
A hallmark of acute myeloid leukemia (AML) is the inability of self-renewing malignant cells to mature into a non-dividing terminally differentiated state. This differentiation block has been linked to dysregulation of multiple cellular processes, including transcriptional, chromatin, and metabolic regulation. The transcription factor HOXA9 and the histone demethylase LSD1 are examples of such regulators that promote differentiation blockade in AML. To identify metabolic targets that interact with LSD1 inhibition to promote myeloid maturation, we screened a small molecule library to identify druggable substrates. We found that differentiation caused by LSD1 inhibition is enhanced by combined perturbation of purine nucleotide salvage and de novo lipogenesis pathways, and identified multiple lines of evidence to support the specificity of these pathways and suggest a potential basis of how perturbation of these pathways may interact synergistically to promote myeloid differentiation. In sum, these findings suggest potential drug combination strategies in the treatment of AML.
RESUMEN
Patients with acute myeloid leukemia (AML) frequently relapse after chemotherapy, yet the mechanism by which AML reemerges is not fully understood. Herein, we show that primary AML cells enter a senescence-like phenotype following chemotherapy in vitro and in vivo. This is accompanied by induction of senescence/inflammatory and embryonic diapause transcriptional programs, with downregulation of MYC and leukemia stem cell genes. Single-cell RNA sequencing suggested depletion of leukemia stem cells in vitro and in vivo, and enrichment for subpopulations with distinct senescence-like cells. This senescence effect was transient and conferred superior colony-forming and engraftment potential. Entry into this senescence-like phenotype was dependent on ATR, and persistence of AML cells was severely impaired by ATR inhibitors. Altogether, we propose that AML relapse is facilitated by a senescence-like resilience phenotype that occurs regardless of their stem cell status. Upon recovery, these post-senescence AML cells give rise to relapsed AMLs with increased stem cell potential. SIGNIFICANCE: Despite entering complete remission after chemotherapy, relapse occurs in many patients with AML. Thus, there is an urgent need to understand the relapse mechanism in AML and the development of targeted treatments to improve outcome. Here, we identified a senescence-like resilience phenotype through which AML cells can survive and repopulate leukemia.This article is highlighted in the In This Issue feature, p. 1307.
Asunto(s)
Leucemia Mieloide Aguda/tratamiento farmacológico , Recurrencia Local de Neoplasia/tratamiento farmacológico , Células Madre Neoplásicas/citología , Inducción de Remisión , Animales , Línea Celular Tumoral/citología , Humanos , Leucemia Mieloide Aguda/patología , Ratones , Ratones Endogámicos NOD , Recurrencia Local de Neoplasia/patología , FenotipoRESUMEN
Treatment-persistent residual tumors impede curative cancer therapy. To understand this cancer cell state we generated models of treatment persistence that simulate the residual tumors. We observe that treatment-persistent tumor cells in organoids, xenografts, and cancer patients adopt a distinct and reversible transcriptional program resembling that of embryonic diapause, a dormant stage of suspended development triggered by stress and associated with suppressed Myc activity and overall biosynthesis. In cancer cells, depleting Myc or inhibiting Brd4, a Myc transcriptional co-activator, attenuates drug cytotoxicity through a dormant diapause-like adaptation with reduced apoptotic priming. Conversely, inducible Myc upregulation enhances acute chemotherapeutic activity. Maintaining residual cells in dormancy after chemotherapy by inhibiting Myc activity or interfering with the diapause-like adaptation by inhibiting cyclin-dependent kinase 9 represent potential therapeutic strategies against chemotherapy-persistent tumor cells. Our study demonstrates that cancer co-opts a mechanism similar to diapause with adaptive inactivation of Myc to persist during treatment.
Asunto(s)
Adaptación Fisiológica/genética , Embrión de Mamíferos/fisiología , Proteínas Proto-Oncogénicas c-myc/genética , Adaptación Fisiológica/efectos de los fármacos , Animales , Antineoplásicos/farmacología , Apoptosis/genética , Línea Celular , Línea Celular Tumoral , Quinasa 9 Dependiente de la Ciclina/genética , Diapausa/efectos de los fármacos , Diapausa/genética , Embrión de Mamíferos/efectos de los fármacos , Femenino , Células HEK293 , Humanos , Células MCF-7 , Ratones , Factores de Transcripción/genética , Transcripción Genética/genética , Regulación hacia Arriba/efectos de los fármacos , Regulación hacia Arriba/genéticaRESUMEN
Although we are just beginning to understand the mechanisms that regulate the epigenome, aberrant epigenetic programming has already emerged as a hallmark of hematologic malignancies including acute myeloid leukemia (AML) and B-cell lymphomas. Although these diseases arise from the hematopoietic system, the epigenetic mechanisms that drive these malignancies are quite different. Yet, in all of these tumors, somatic mutations in transcription factors and epigenetic modifiers are the most commonly mutated set of genes and result in multilayered disruption of the epigenome. Myeloid and lymphoid neoplasms generally manifest epigenetic allele diversity, which contributes to tumor cell population fitness regardless of the underlying genetics. Epigenetic therapies are emerging as one of the most promising new approaches for these patients. However, effective targeting of the epigenome must consider the need to restore the various layers of epigenetic marks, appropriate biological end points, and specificity of therapeutic agents to truly realize the potential of this modality.
Asunto(s)
Leucemia Mieloide Aguda/genética , Linfoma de Células B/genética , Antineoplásicos/farmacología , Antineoplásicos/uso terapéutico , Epigénesis Genética , Regulación Neoplásica de la Expresión Génica/genética , Humanos , Leucemia Mieloide Aguda/tratamiento farmacológico , Linfoma de Células B/tratamiento farmacológico , Mutación MissenseRESUMEN
Diffuse large B cell lymphomas (DLBCLs) are genetically heterogeneous and highly proliferative neoplasms derived from germinal center (GC) B cells. Here, we show that DLBCLs are dependent on mitochondrial lysine deacetylase SIRT3 for proliferation, survival, self-renewal, and tumor growth in vivo regardless of disease subtype and genetics. SIRT3 knockout attenuated B cell lymphomagenesis in VavP-Bcl2 mice without affecting normal GC formation. Mechanistically, SIRT3 depletion impaired glutamine flux to the TCA cycle via glutamate dehydrogenase and reduction in acetyl-CoA pools, which in turn induce autophagy and cell death. We developed a mitochondrial-targeted class I sirtuin inhibitor, YC8-02, which phenocopied the effects of SIRT3 depletion and killed DLBCL cells. SIRT3 is thus a metabolic non-oncogene addiction and therapeutic target for DLBCLs.
Asunto(s)
Proliferación Celular/efectos de los fármacos , Metabolismo Energético/efectos de los fármacos , Linfoma de Células B Grandes Difuso/enzimología , Sirtuina 3/metabolismo , Acetilcoenzima A/metabolismo , Animales , Antineoplásicos/farmacología , Muerte Celular Autofágica/efectos de los fármacos , Ciclo del Ácido Cítrico/efectos de los fármacos , Femenino , Regulación Enzimológica de la Expresión Génica , Regulación Neoplásica de la Expresión Génica , Glutamina/metabolismo , Células HEK293 , Inhibidores de Histona Desacetilasas/farmacología , Humanos , Linfoma de Células B Grandes Difuso/tratamiento farmacológico , Linfoma de Células B Grandes Difuso/genética , Linfoma de Células B Grandes Difuso/patología , Células MCF-7 , Ratones Endogámicos C57BL , Ratones Endogámicos NOD , Ratones Noqueados , Ratones SCID , Terapia Molecular Dirigida , Transducción de Señal , Sirtuina 3/antagonistas & inhibidores , Sirtuina 3/deficiencia , Sirtuina 3/genética , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Disruption of epigenetic regulation is a hallmark of acute myeloid leukemia (AML), but epigenetic therapy is complicated by the complexity of the epigenome. Herein, we developed a long-term primary AML ex vivo platform to determine whether targeting different epigenetic layers with 5-azacytidine and LSD1 inhibitors would yield improved efficacy. This combination was most effective in TET2 mut AML, where it extinguished leukemia stem cells and particularly induced genes with both LSD1-bound enhancers and cytosine-methylated promoters. Functional studies indicated that derepression of genes such as GATA2 contributes to drug efficacy. Mechanistically, combination therapy increased enhancer-promoter looping and chromatin-activating marks at the GATA2 locus. CRISPRi of the LSD1-bound enhancer in patient-derived TET2 mut AML was associated with dampening of therapeutic GATA2 induction. TET2 knockdown in human hematopoietic stem/progenitor cells induced loss of enhancer 5-hydroxymethylation and facilitated LSD1-mediated enhancer inactivation. Our data provide a basis for rational targeting of cooperating aberrant promoter and enhancer epigenetic marks driven by mutant epigenetic modifiers. SIGNIFICANCE: Somatic mutations of genes encoding epigenetic modifiers are a hallmark of AML and potentially disrupt many components of the epigenome. Our study targets two different epigenetic layers at promoters and enhancers that cooperate to aberrant gene silencing, downstream of the actions of a mutant epigenetic regulator.This article is highlighted in the In This Issue feature, p. 813.
Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/farmacología , Histona Demetilasas/antagonistas & inhibidores , Histona Demetilasas/genética , Leucemia Mieloide Aguda/tratamiento farmacológico , Leucemia Mieloide Aguda/genética , Animales , Azacitidina/farmacología , ADN (Citosina-5-)-Metiltransferasa 1/antagonistas & inhibidores , Metilación de ADN/efectos de los fármacos , Proteínas de Unión al ADN/genética , Dioxigenasas , Elementos de Facilitación Genéticos , Epigenoma , Factor de Transcripción GATA2/genética , Factor de Transcripción GATA2/metabolismo , Genes Supresores de Tumor , Humanos , Leucemia Mieloide Aguda/metabolismo , Leucemia Mieloide Aguda/patología , Ratones , Ratones Endogámicos NOD , Ratones SCID , Células Madre Neoplásicas/metabolismo , Células Madre Neoplásicas/patología , Regiones Promotoras Genéticas/efectos de los fármacos , Proteínas Proto-Oncogénicas/genética , Distribución Aleatoria , Células Tumorales Cultivadas , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
In this issue, Maganti and colleagues described an epigenetic link between reduced abundance of Polycomb-related protein MTF2 and chemotherapy resistance in refractory acute myeloid leukemia. MTF2 deficiency impaired expression of the PRC2 complex and deposition of H3K27me3 at many genes, including the key target gene MDM2, leading to increased MDM2 expression that in turn depleted p53 and thereby conferred chemoresistance. Cancer Discov; 8(11); 1348-51. ©2018 AACR See related article by Maganti et al., p. 1376.
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Leucemia Mieloide Aguda , Complejo Represivo Polycomb 2 , Humanos , Proteínas del Grupo Polycomb , Proteínas Proto-Oncogénicas c-mdm2RESUMEN
The lysine-specific demethylase KDM1A is a key regulator of stem cell potential in acute myeloid leukemia (AML). ORY-1001 is a highly potent and selective KDM1A inhibitor that induces H3K4me2 accumulation on KDM1A target genes, blast differentiation, and reduction of leukemic stem cell capacity in AML. ORY-1001 exhibits potent synergy with standard-of-care drugs and selective epigenetic inhibitors, reduces growth of an AML xenograft model, and extends survival in a mouse PDX (patient-derived xenograft) model of T cell acute leukemia. Surrogate pharmacodynamic biomarkers developed based on expression changes in leukemia cell lines were translated to samples from patients treated with ORY-1001. ORY-1001 is a selective KDM1A inhibitor in clinical trials and is currently being evaluated in patients with leukemia and solid tumors.
Asunto(s)
Diferenciación Celular/efectos de los fármacos , Histona Demetilasas/efectos de los fármacos , Leucemia Mieloide Aguda/tratamiento farmacológico , Animales , Apoptosis/efectos de los fármacos , Línea Celular Tumoral/metabolismo , Modelos Animales de Enfermedad , Histona Demetilasas/antagonistas & inhibidores , Histona Demetilasas/genética , Humanos , Leucemia Mieloide Aguda/genética , Ratones , Células Madre/efectos de los fármacos , Células Madre/metabolismoRESUMEN
Hairy cell leukemia (HCL) is a chronic lymphoproliferative disorder characterized by somatic BRAFV600E mutations. The malignant cell in HCL has immunophenotypic features of a mature B cell, but no normal counterpart along the continuum of developing B lymphocytes has been delineated as the cell of origin. We find that the BRAFV600E mutation is present in hematopoietic stem cells (HSCs) in HCL patients, and that these patients exhibit marked alterations in hematopoietic stem/progenitor cell (HSPC) frequencies. Quantitative sequencing analysis revealed a mean BRAFV600E-mutant allele frequency of 4.97% in HSCs from HCL patients. Moreover, transplantation of BRAFV600E-mutant HSCs from an HCL patient into immunodeficient mice resulted in stable engraftment of BRAFV600E-mutant human hematopoietic cells, revealing the functional self-renewal capacity of HCL HSCs. Consistent with the human genetic data, expression of BRafV600E in murine HSPCs resulted in a lethal hematopoietic disorder characterized by splenomegaly, anemia, thrombocytopenia, increased circulating soluble CD25, and increased clonogenic capacity of B lineage cells-all classic features of human HCL. In contrast, restricting expression of BRafV600E to the mature B cell compartment did not result in disease. Treatment of HCL patients with vemurafenib, an inhibitor of mutated BRAF, resulted in normalization of HSPC frequencies and increased myeloid and erythroid output from HSPCs. These findings link the pathogenesis of HCL to somatic mutations that arise in HSPCs and further suggest that chronic lymphoid malignancies may be initiated by aberrant HSCs.
Asunto(s)
Células Madre Hematopoyéticas/patología , Leucemia de Células Pilosas/genética , Mutación , Proteínas Proto-Oncogénicas B-raf/genética , Animales , Humanos , Leucemia de Células Pilosas/patología , RatonesRESUMEN
BCL6 protects germinal center (GC) B cells against DNA damage-induced apoptosis during somatic hypermutation and class-switch recombination. Although expression of BCL6 was not found in early IL-7-dependent B cell precursors, we report that IL-7Ralpha-Stat5 signaling negatively regulates BCL6. Upon productive VH-DJH gene rearrangement and expression of a mu heavy chain, however, activation of pre-B cell receptor signaling strongly induces BCL6 expression, whereas IL-7Ralpha-Stat5 signaling is attenuated. At the transition from IL-7-dependent to -independent stages of B cell development, BCL6 is activated, reaches expression levels resembling those in GC B cells, and protects pre-B cells from DNA damage-induced apoptosis during immunoglobulin (Ig) light chain gene recombination. In the absence of BCL6, DNA breaks during Ig light chain gene rearrangement lead to excessive up-regulation of Arf and p53. As a consequence, the pool of new bone marrow immature B cells is markedly reduced in size and clonal diversity. We conclude that negative regulation of Arf by BCL6 is required for pre-B cell self-renewal and the formation of a diverse polyclonal B cell repertoire.
Asunto(s)
Linfocitos B/citología , Linfocitos B/inmunología , Proteínas de Unión al ADN/inmunología , Factores de Ribosilacion-ADP/metabolismo , Animales , Apoptosis , Secuencia de Bases , Proliferación Celular , Supervivencia Celular , Células Cultivadas , Citoprotección , Daño del ADN/genética , Regulación hacia Abajo/genética , Reordenamiento Génico de Cadena Ligera de Linfocito B/genética , Humanos , Interleucina-7/metabolismo , Linfopoyesis , Ratones , Datos de Secuencia Molecular , Receptores de Células Precursoras de Linfocitos B/metabolismo , Células Precursoras de Linfocitos B/citología , Células Precursoras de Linfocitos B/metabolismo , Proteínas Proto-Oncogénicas c-bcl-6 , Proteínas Proto-Oncogénicas c-myc/metabolismo , Recombinación Genética/genética , Transducción de Señal , Transcripción Genética , Regulación hacia Arriba/genéticaRESUMEN
Chronic myeloid leukemia (CML) is induced by BCR-ABL1 and can be effectively treated for many years with Imatinib until leukemia cells acquire drug resistance through BCR-ABL1 mutations and progress into fatal B lymphoid blast crisis (LBC). Despite its clinical significance, the mechanism of progression into LBC is unknown. Here, we show that LBC but not CML cells express the B cell-specific mutator enzyme AID. We demonstrate that AID expression in CML cells promotes overall genetic instability by hypermutation of tumor suppressor and DNA repair genes. Importantly, our data uncover a causative role of AID activity in the acquisition of BCR-ABL1 mutations leading to Imatinib resistance, thus providing a rationale for the rapid development of drug resistance and blast crisis progression.
Asunto(s)
Linfocitos B/efectos de los fármacos , Crisis Blástica/tratamiento farmacológico , Citidina Desaminasa/metabolismo , Resistencia a Antineoplásicos/genética , Leucemia Mielógena Crónica BCR-ABL Positiva/tratamiento farmacológico , Mutación , Piperazinas/uso terapéutico , Pirimidinas/uso terapéutico , Animales , Linfocitos B/patología , Benzamidas , Línea Celular Tumoral , Proteínas de Fusión bcr-abl/genética , Proteínas Fluorescentes Verdes/metabolismo , Humanos , Mesilato de Imatinib , Leucemia Mielógena Crónica BCR-ABL Positiva/genética , Leucemia Mielógena Crónica BCR-ABL Positiva/patología , Luciferasas de Renilla/metabolismo , Ratones , Ratones Endogámicos BALB C , Ratones Noqueados , Ratones SCID , Ratones Transgénicos , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
B cell lineage acute lymphoblastic leukemia (ALL) arises in virtually all cases from B cell precursors that are arrested at pre-B cell receptor-dependent stages. The Philadelphia chromosome-positive (Ph(+)) subtype of ALL accounts for 25-30% of cases of adult ALL, has the most unfavorable clinical outcome among all ALL subtypes and is defined by the oncogenic BCR-ABL1 kinase and deletions of the IKAROS gene in >80% of cases. Here, we demonstrate that the pre-B cell receptor functions as a tumor suppressor upstream of IKAROS through induction of cell cycle arrest in Ph(+) ALL cells. Pre-B cell receptor-mediated cell cycle arrest in Ph(+) ALL cells critically depends on IKAROS function, and is reversed by coexpression of the dominant-negative IKAROS splice variant IK6. IKAROS also promotes tumor suppression through cooperation with downstream molecules of the pre-B cell receptor signaling pathway, even if expression of the pre-B cell receptor itself is compromised. In this case, IKAROS redirects oncogenic BCR-ABL1 tyrosine kinase signaling from SRC kinase-activation to SLP65, which functions as a critical tumor suppressor downstream of the pre-B cell receptor. These findings provide a rationale for the surprisingly high frequency of IKAROS deletions in Ph(+) ALL and identify IKAROS-mediated cell cycle exit as the endpoint of an emerging pathway of pre-B cell receptor-mediated tumor suppression.