RESUMO
Leukaemia stem cells (LSCs) are the critical seed for the growth of haematological malignancies, driving the clonal expansion that enables disease initiation, relapse and often resistance. Specifically, they display inherent phenotypic and epigenetic plasticity resulting in complex heterogenic diseases. In this review, we discuss the key principles of deregulation of epigenetic processes that shape this disease evolution. We consider measures to define and quantify clonal heterogeneity, combining information from recent studies assessing mutational, transcriptional and epigenetic landscapes at single cell resolution in myeloid neoplasms (MN). We highlight the importance of integrating epigenetic and genetic information to better understand inter- and intra-patient heterogeneity and discuss how this understanding further informs evolution and progression trajectories and subsequent clinical response in MN. Under this topic, we also discuss efforts to identify mechanisms of resistance, by longitudinal analyses of patient samples. Finally, we highlight how we might target these aberrant epigenetic processes for better therapeutic outcomes and to potentially eradicate LSCs.
Assuntos
Leucemia Mieloide Aguda , Humanos , Leucemia Mieloide Aguda/genética , Epigênese Genética , Mutação , Células-Tronco , Células-Tronco Neoplásicas/patologiaRESUMO
HOXA9 is commonly upregulated in acute myeloid leukemia (AML), in which it confers a poor prognosis. Characterizing the protein interactome of endogenous HOXA9 in human AML, we identified a chromatin complex of HOXA9 with the nuclear matrix attachment protein SAFB. SAFB perturbation phenocopied HOXA9 knockout to decrease AML proliferation, increase differentiation and apoptosis in vitro, and prolong survival in vivo. Integrated genomic, transcriptomic, and proteomic analyses further demonstrated that the HOXA9-SAFB (H9SB)-chromatin complex associates with nucleosome remodeling and histone deacetylase (NuRD) and HP1γ to repress the expression of factors associated with differentiation and apoptosis, including NOTCH1, CEBPδ, S100A8, and CDKN1A. Chemical or genetic perturbation of NuRD and HP1γ-associated catalytic activity also triggered differentiation, apoptosis, and the induction of these tumor-suppressive genes. Importantly, this mechanism is operative in other HOXA9-dependent AML genotypes. This mechanistic insight demonstrates the active HOXA9-dependent differentiation block as a potent mechanism of disease maintenance in AML that may be amenable to therapeutic intervention by targeting the H9SB interface and/or NuRD and HP1γ activity.
Assuntos
Leucemia Mieloide Aguda , Proteínas de Ligação à Região de Interação com a Matriz , Humanos , Proteômica , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Leucemia Mieloide Aguda/tratamento farmacológico , Fatores de Transcrição/genética , Proteínas Associadas à Matriz Nuclear , Cromatina , Receptores de Estrogênio/genética , Receptores de Estrogênio/uso terapêutico , Proteínas de Ligação à Região de Interação com a Matriz/genéticaRESUMO
Altered transcription is a cardinal feature of acute myeloid leukemia (AML); however, exactly how mutations synergize to remodel the epigenetic landscape and rewire three-dimensional DNA topology is unknown. Here, we apply an integrated genomic approach to a murine allelic series that models the two most common mutations in AML: Flt3-ITD and Npm1c. We then deconvolute the contribution of each mutation to alterations of the epigenetic landscape and genome organization, and infer how mutations synergize in the induction of AML. Our studies demonstrate that Flt3-ITD signals to chromatin to alter the epigenetic environment and synergizes with mutations in Npm1c to alter gene expression and drive leukemia induction. These analyses also allow the identification of long-range cis-regulatory circuits, including a previously unknown superenhancer of Hoxa locus, as well as larger and more detailed gene-regulatory networks, driven by transcription factors including PU.1 and IRF8, whose importance we demonstrate through perturbation of network members.
Assuntos
Montagem e Desmontagem da Cromatina/genética , DNA de Neoplasias/química , Regulação Leucêmica da Expressão Gênica , Histonas/metabolismo , Leucemia Mieloide Aguda/genética , Mutação/genética , Processamento de Proteína Pós-Traducional , Animais , Sequência de Bases , Modelos Animais de Doenças , Elementos Facilitadores Genéticos/genética , Redes Reguladoras de Genes , Loci Gênicos , Humanos , Camundongos Endogâmicos C57BL , Proteínas Nucleares/metabolismo , Nucleofosmina , Análise de Componente Principal , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transcrição Gênica , Tirosina Quinase 3 Semelhante a fms/metabolismoRESUMO
Interferons (IFNs) represent an important host defense against viruses. Type I IFNs induce JAK-STAT signaling and expression of IFN-stimulated genes (ISGs), which mediate antiviral activity. Histone deacetylases (HDACs) perform multiple functions in regulating gene expression and some class I HDACs and the class IV HDAC, HDAC11, influence type I IFN signaling. Here, HDAC4, a class II HDAC, is shown to promote type I IFN signaling and coprecipitate with STAT2. Pharmacological inhibition of class II HDAC activity, or knockout of HDAC4 from HEK-293T and HeLa cells, caused a defective response to IFN-α. This defect in HDAC4-/- cells was rescued by reintroduction of HDAC4 or catalytically inactive HDAC4, but not HDAC1 or HDAC5. ChIP analysis showed HDAC4 was recruited to ISG promoters following IFN stimulation and was needed for binding of STAT2 to these promoters. The biological importance of HDAC4 as a virus restriction factor was illustrated by the observations that (i) the replication and spread of vaccinia virus (VACV) and herpes simplex virus type 1 (HSV-1) were enhanced in HDAC4-/- cells and inhibited by overexpression of HDAC4; and (ii) HDAC4 is targeted for proteasomal degradation during VACV infection by VACV protein C6, a multifunctional IFN antagonist that coprecipitates with HDAC4 and is necessary and sufficient for HDAC4 degradation.
Assuntos
Vírus de DNA/metabolismo , Histona Desacetilases/metabolismo , Interferon Tipo I/metabolismo , Proteínas Repressoras/metabolismo , Transdução de Sinais/fisiologia , Vaccinia virus/metabolismo , Vacínia/metabolismo , Proteínas Virais/metabolismo , Linhagem Celular , Linhagem Celular Tumoral , Células HEK293 , Células HeLa , Herpesvirus Humano 1/metabolismo , Humanos , Vacínia/virologia , Replicação Viral/fisiologiaRESUMO
The PLZF transcription factor is essential for osteogenic differentiation of hMSCs; however, its regulation and molecular function during this process is not fully understood. Here, we revealed that the ZBTB16 locus encoding PLZF, is repressed by Polycomb (PcG) and H3K27me3 in naive hMSCs. At the pre-osteoblast stage of differentiation, the locus lost PcG binding and H3K27me3, gained JMJD3 recruitment, and H3K27ac resulting in high expression of PLZF. Subsequently, PLZF was recruited to osteogenic enhancers, influencing H3K27 acetylation and expression of nearby genes important for osteogenic function. Furthermore, we identified a latent enhancer within the ZBTB16/PLZF locus itself that became active, gained PLZF, p300 and Mediator binding and looped to the promoter of the nicotinamide N-methyltransferase (NNMT) gene. The increased expression of NNMT correlated with a decline in SAM levels, which is dependent on PLZF and is required for osteogenic differentiation.
Assuntos
Diferenciação Celular/genética , Desenvolvimento Embrionário/genética , Elementos Facilitadores Genéticos/genética , Células-Tronco Mesenquimais/citologia , Células-Tronco Mesenquimais/metabolismo , Osteogênese/genética , Proteína com Dedos de Zinco da Leucemia Promielocítica/metabolismo , Acetilação , Linhagem da Célula/genética , Cromatina/metabolismo , Epigênese Genética , Loci Gênicos , Histonas/metabolismo , Humanos , Lisina/metabolismo , Nicotinamida N-Metiltransferase/genética , Nicotinamida N-Metiltransferase/metabolismo , Regiões Promotoras Genéticas , Proteína com Dedos de Zinco da Leucemia Promielocítica/genética , Ligação Proteica , RNA/genética , Transcriptoma/genéticaRESUMO
In acute myeloid leukemia (AML), therapy resistance frequently occurs, leading to high mortality among patients. However, the mechanisms that render leukemic cells drug resistant remain largely undefined. Here, we identified loss of the histone methyltransferase EZH2 and subsequent reduction of histone H3K27 trimethylation as a novel pathway of acquired resistance to tyrosine kinase inhibitors (TKIs) and cytotoxic drugs in AML. Low EZH2 protein levels correlated with poor prognosis in AML patients. Suppression of EZH2 protein expression induced chemoresistance of AML cell lines and primary cells in vitro and in vivo. Low EZH2 levels resulted in derepression of HOX genes, and knockdown of HOXB7 and HOXA9 in the resistant cells was sufficient to improve sensitivity to TKIs and cytotoxic drugs. The endogenous loss of EZH2 expression in resistant cells and primary blasts from a subset of relapsed AML patients resulted from enhanced CDK1-dependent phosphorylation of EZH2 at Thr487. This interaction was stabilized by heat shock protein 90 (HSP90) and followed by proteasomal degradation of EZH2 in drug-resistant cells. Accordingly, inhibitors of HSP90, CDK1 and the proteasome prevented EZH2 degradation, decreased HOX gene expression and restored drug sensitivity. Finally, patients with reduced EZH2 levels at progression to standard therapy responded to the combination of bortezomib and cytarabine, concomitant with the re-establishment of EZH2 expression and blast clearance. These data suggest restoration of EZH2 protein as a viable approach to overcome treatment resistance in this AML patient population.
Assuntos
Resistencia a Medicamentos Antineoplásicos/genética , Proteína Potenciadora do Homólogo 2 de Zeste/genética , Histonas/metabolismo , Leucemia Mieloide Aguda/tratamento farmacológico , Inibidores de Proteínas Quinases , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Antineoplásicos/farmacologia , Western Blotting , Bortezomib/farmacologia , Proteína Quinase CDC2 , Linhagem Celular Tumoral , Quinases Ciclina-Dependentes/metabolismo , Citarabina/farmacologia , Proteína Potenciadora do Homólogo 2 de Zeste/antagonistas & inibidores , Proteína Potenciadora do Homólogo 2 de Zeste/metabolismo , Feminino , Citometria de Fluxo , Regulação Neoplásica da Expressão Gênica , Técnicas de Silenciamento de Genes , Proteínas de Choque Térmico HSP90/metabolismo , Proteínas de Homeodomínio/genética , Humanos , Imuno-Histoquímica , Imunoprecipitação , Indóis/farmacologia , Leucemia Mieloide Aguda/genética , Masculino , Espectrometria de Massas , Camundongos , Pessoa de Meia-Idade , Transplante de Neoplasias , Complexo de Endopeptidases do Proteassoma/metabolismo , Processamento de Proteína Pós-Traducional , Proteômica , Piridonas/farmacologia , Adulto JovemRESUMO
Oncogene-induced senescence (OIS) can occur in response to oncogenic insults and is considered an important tumour suppressor mechanism. Here we identify the lncRNA MIR31HG as upregulated in OIS and find that knockdown of MIR31HG promotes a strong p16(INK4A)-dependent senescence phenotype. Under normal conditions, MIR31HG is found in both nucleus and cytoplasm, but following B-RAF expression MIR31HG is located mainly in the cytoplasm. We show that MIR31HG interacts with both INK4A and MIR31HG genomic regions and with Polycomb group (PcG) proteins, and that MIR31HG is required for PcG-mediated repression of the INK4A locus. We further identify a functional enhancer, located between MIR31HG and INK4A, which becomes activated during OIS and interacts with the MIR31HG promoter. Data from melanoma patients show a negative correlation between MIR31HG and p16(INK4A) expression levels, suggesting a role for this transcript in cancer. Hence, our data provide a new lncRNA-mediated regulatory mechanism for the tumour suppressor p16(INK4A).
Assuntos
Senescência Celular , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , Melanoma/metabolismo , Proteínas Proto-Oncogênicas B-raf/metabolismo , RNA Longo não Codificante/metabolismo , Animais , Elementos Facilitadores Genéticos , Regulação Neoplásica da Expressão Gênica , Técnicas de Silenciamento de Genes , Células HEK293 , Humanos , Camundongos , Oncogenes , Fenótipo , Proteínas do Grupo Polycomb/metabolismoRESUMO
The origin of aberrant DNA methylation in cancer remains largely unknown. In the present study, we elucidated the DNA methylome in primary acute promyelocytic leukemia (APL) and the role of promyelocytic leukemia-retinoic acid receptor α (PML-RARα) in establishing these patterns. Cells from APL patients showed increased genome-wide DNA methylation with higher variability than healthy CD34(+) cells, promyelocytes, and remission BM cells. A core set of differentially methylated regions in APL was identified. Age at diagnosis, Sanz score, and Flt3-mutation status characterized methylation subtypes. Transcription factor-binding sites (eg, the c-myc-binding sites) were associated with low methylation. However, SUZ12- and REST-binding sites identified in embryonic stem cells were preferentially DNA hypermethylated in APL cells. Unexpectedly, PML-RARα-binding sites were also protected from aberrant DNA methylation in APL cells. Consistent with this, myeloid cells from preleukemic PML-RARα knock-in mice did not show altered DNA methylation and the expression of PML-RARα in hematopoietic progenitor cells prevented differentiation without affecting DNA methylation. Treatment of APL blasts with all-trans retinoic acid also did not result in immediate DNA methylation changes. The results of the present study suggest that aberrant DNA methylation is associated with leukemia phenotype but is not required for PML-RARα-mediated initiation of leukemogenesis.
Assuntos
Metilação de DNA , DNA de Neoplasias/genética , Regulação Leucêmica da Expressão Gênica , Leucemia Promielocítica Aguda/genética , Fatores de Transcrição/metabolismo , Animais , Transformação Celular Neoplásica/genética , Cromossomos Humanos/ultraestrutura , Ilhas de CpG , DNA de Neoplasias/metabolismo , Progressão da Doença , Técnicas de Introdução de Genes , Células-Tronco Hematopoéticas/metabolismo , Humanos , Leucemia Promielocítica Aguda/tratamento farmacológico , Camundongos , Camundongos Endogâmicos C57BL , Proteínas de Neoplasias/fisiologia , Células-Tronco Neoplásicas/metabolismo , Proteínas de Fusão Oncogênica/fisiologia , Fenótipo , Complexo Repressor Polycomb 2/metabolismo , Pré-Leucemia/genética , Proteínas Recombinantes de Fusão/fisiologia , Proteínas Repressoras/metabolismo , Tretinoína/uso terapêuticoRESUMO
Polycomb Repressive Complex (PRC) 1 and PRC2 regulate genes involved in differentiation and development. However, the mechanism for how PRC1 and PRC2 are recruited to genes in mammalian cells is unclear. Here we present evidence for an interaction between the transcription factor REST, PRC1, and PRC2 and show that RNF2 and REST co-regulate a number of neuronal genes in human teratocarcinoma cells (NT2-D1). Using NT2-D1 cells as a model of neuronal differentiation, we furthermore showed that retinoic-acid stimulation led to displacement of PRC1 at REST binding sites, reduced H3K27Me3, and increased gene expression. Genome-wide analysis of Polycomb binding in Restâ»/â» and Eedâ»/â» mouse embryonic stem (mES) cells showed that Rest was required for PRC1 recruitment to a subset of Polycomb regulated neuronal genes. Furthermore, we found that PRC1 can be recruited to Rest binding sites independently of CpG islands and the H3K27Me3 mark. Surprisingly, PRC2 was frequently increased around Rest binding sites located in CpG-rich regions in the Restâ»/â» mES cells, indicating a more complex interplay where Rest also can limit PRC2 recruitment. Therefore, we propose that Rest has context-dependent functions for PRC1- and PRC2- recruitment, which allows this transcription factor to act both as a recruiter of Polycomb as well as a limiting factor for PRC2 recruitment at CpG islands.
Assuntos
Diferenciação Celular , Ilhas de CpG/genética , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Animais , Sítios de Ligação , Diferenciação Celular/efeitos dos fármacos , Células-Tronco Embrionárias/citologia , Células-Tronco Embrionárias/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Células HEK293 , Humanos , Histona Desmetilases com o Domínio Jumonji/metabolismo , Camundongos , Neurônios/metabolismo , Proteínas do Grupo Polycomb , Ligação Proteica , Teratoma/genética , Tretinoína/farmacologiaRESUMO
With the use of ChIP on microarray assays in primary leukemia samples, we report that acute myeloid leukemia (AML) blasts exhibit significant alterations in histone H3 acetylation (H3Ac) levels at > 1000 genomic loci compared with CD34(+) progenitor cells. Importantly, core promoter regions tended to have lower H3Ac levels in AML compared with progenitor cells, which suggested that a large number of genes are epigenetically silenced in AML. Intriguingly, we identified peroxiredoxin 2 (PRDX2) as a novel potential tumor suppressor gene in AML. H3Ac was decreased at the PRDX2 gene promoter in AML, which correlated with low mRNA and protein expression. We also observed DNA hypermethylation at the PRDX2 promoter in AML. Low protein expression of the antioxidant PRDX2 gene was clinically associated with poor prognosis in patients with AML. Functionally, PRDX2 acted as inhibitor of myeloid cell growth by reducing levels of reactive oxygen species (ROS) generated in response to cytokines. Forced PRDX2 expression inhibited c-Myc-induced leukemogenesis in vivo on BM transplantation in mice. Taken together, epigenome-wide analyses of H3Ac in AML led to the identification of PRDX2 as an epigenetically silenced growth suppressor, suggesting a possible role of ROS in the malignant phenotype in AML.
Assuntos
Metilação de DNA , Histonas/metabolismo , Peroxirredoxinas/genética , Proteínas Supressoras de Tumor/genética , Acetilação , Doença Aguda , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Proliferação de Células , Células Cultivadas , Epigênese Genética , Feminino , Perfilação da Expressão Gênica/métodos , Estudo de Associação Genômica Ampla , Células HL-60 , Humanos , Masculino , Pessoa de Meia-Idade , Análise de Sequência com Séries de Oligonucleotídeos/métodos , Peroxirredoxinas/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Células U937 , Adulto JovemRESUMO
The cell cycle is driven by the kinase activity of cyclin·cyclin-dependent kinase (CDK) complexes, which is negatively regulated by CDK inhibitor proteins. Recently, we identified INCA1 as an interaction partner and a substrate of cyclin A1 in complex with CDK2. On a functional level, we identified a novel cyclin-binding site in the INCA1 protein. INCA1 inhibited CDK2 activity and cell proliferation. The inhibitory effects depended on the cyclin-interacting domain. Mitogenic and oncogenic signals suppressed INCA1 expression, whereas it was induced by cell cycle arrest. We established a deletional mouse model that showed increased CDK2 activity in spleen with altered spleen architecture in Inca1(-/-) mice. Inca1(-/-) embryonic fibroblasts showed an increase in the fraction of S-phase cells. Furthermore, blasts from acute lymphoid leukemia and acute myeloid leukemia patients expressed significantly reduced INCA1 levels highlighting its relevance for growth control in vivo. Taken together, this study identifies a novel CDK inhibitor with reduced expression in acute myeloid and lymphoid leukemia. The molecular events that control the cell cycle occur in a sequential process to ensure a tight regulation, which is important for the survival of a cell and includes the detection and repair of genetic damage and the prevention of uncontrolled cell division.
Assuntos
Crise Blástica/metabolismo , Proteínas de Transporte/metabolismo , Leucemia Mieloide Aguda/metabolismo , Proteínas de Neoplasias/metabolismo , Fosfoproteínas/metabolismo , Leucemia-Linfoma Linfoblástico de Células Precursoras/metabolismo , Fase S , Transdução de Sinais , Animais , Crise Blástica/genética , Crise Blástica/patologia , Proteínas de Transporte/genética , Linhagem Celular , Sobrevivência Celular/genética , Quinase 2 Dependente de Ciclina/genética , Quinase 2 Dependente de Ciclina/metabolismo , Embrião de Mamíferos/metabolismo , Embrião de Mamíferos/patologia , Humanos , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patologia , Camundongos , Camundongos Knockout , Proteínas de Neoplasias/genética , Fosfoproteínas/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/patologiaRESUMO
Epigenetic regulation of chromatin structure is essential for the expression of genes determining cellular specification and function. The Polycomb repressive complex 2 (PRC2) di- and trimethylates histone H3 on lysine 27 (H3K27me2/me3) to establish repression of specific genes in embryonic stem cells and during differentiation. How the Polycomb group (PcG) target genes are regulated by environmental cues and signaling pathways is quite unexplored. Here, we show that the mitogen- and stress-activated kinases (MSK), through a mechanism that involves promoter recruitment, histone H3K27me3S28 phosphorylation, and displacement of PcG proteins, lead to gene activation. We present evidence that the H3K27me3S28 phosphorylation is functioning in response to stress signaling, mitogenic signaling, and retinoic acid (RA)-induced neuronal differentiation. We propose that MSK-mediated H3K27me3S28 phosphorylation serves as a mechanism to activate a subset of PcG target genes determined by the biological stimuli and thereby modulate the gene expression program determining cell fate.
Assuntos
Regulação da Expressão Gênica/fisiologia , Histonas/metabolismo , Transporte Proteico/fisiologia , Proteínas Repressoras/metabolismo , Proteínas Quinases S6 Ribossômicas 90-kDa/metabolismo , Fator 3 Ativador da Transcrição/genética , Anisomicina/farmacologia , Anticorpos/imunologia , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/genética , Linhagem Celular Tumoral , Cromatina/genética , Cromatina/metabolismo , Dano ao DNA/efeitos dos fármacos , Dano ao DNA/genética , Células-Tronco Embrionárias/metabolismo , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Expressão Gênica/efeitos dos fármacos , Expressão Gênica/genética , Células HeLa , Histonas/imunologia , Humanos , Lisina/metabolismo , Metilação , Mitose/fisiologia , Neurônios/citologia , Neurônios/metabolismo , Peptídeos/metabolismo , Fosforilação/fisiologia , Proteínas do Grupo Polycomb , Regiões Promotoras Genéticas/genética , Ligação Proteica/fisiologia , Proteínas Quinases S6 Ribossômicas 90-kDa/antagonistas & inibidores , Proteínas Quinases S6 Ribossômicas 90-kDa/genética , Serina/metabolismoRESUMO
Acute myeloid leukemia (AML) is commonly associated with alterations in transcription factors because of altered expression or gene mutations. These changes might induce leukemia-specific patterns of histone modifications. We used chromatin-immunoprecipitation on microarray to analyze histone 3 lysine 9 trimethylation (H3K9me3) patterns in primary AML (n = 108), acute lymphoid leukemia (n = 28), CD34(+) cells (n = 21) and white blood cells (n = 15) specimens. Hundreds of promoter regions in AML showed significant alterations in H3K9me3 levels. H3K9me3 deregulation in AML occurred preferentially as a decrease in H3K9me3 levels at core promoter regions. The altered genomic regions showed an overrepresentation of cis-binding sites for ETS and cyclic adenosine monophosphate response elements (CREs) for transcription factors of the CREB/CREM/ATF1 family. The decrease in H3K9me3 levels at CREs was associated with increased CRE-driven promoter activity in AML blasts in vivo. AML-specific H3K9me3 patterns were not associated with known cytogenetic abnormalities. But a signature derived from H3K9me3 patterns predicted event-free survival in AML patients. When the H3K9me3 signature was combined with established clinical prognostic markers, it outperformed prognosis prediction based on clinical parameters alone. These findings demonstrate widespread changes of H3K9me3 levels at gene promoters in AML. Signatures of histone modification patterns are associated with patient prognosis in AML.
Assuntos
Histonas/metabolismo , Leucemia Mieloide Aguda/diagnóstico , Leucemia Mieloide Aguda/metabolismo , Lisina/metabolismo , Adolescente , Antígenos CD34/imunologia , Criança , Pré-Escolar , Intervalo Livre de Doença , Feminino , Regulação Leucêmica da Expressão Gênica , Células-Tronco Hematopoéticas/imunologia , Histonas/genética , Humanos , Lactente , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/imunologia , Masculino , Metilação , Prognóstico , Regiões Promotoras Genéticas , Ligação Proteica , Fatores de Transcrição/metabolismo , Células Tumorais CultivadasRESUMO
Although the potential role of Pim2 as a cooperative oncogene has been well described in lymphoma, its role in leukemia has remained largely unexplored. Here we show that high expression of Pim2 is observed in patients with acute promyelocytic leukemia (APL). To further characterize the cooperative role of Pim2 with promyelocytic leukemia/retinoic acid receptor alpha (PML/RARalpha), we used a well-established PML-RARalpha (PRalpha) mouse model. Pim2 coexpression in PRalpha-positive hematopoietic progenitor cells (HPCs) induces leukemia in recipient mice after a short latency. Pim2-PRalpha cells were able to repopulate mice in serial transplantations and to induce disease in all recipients. Neither Pim2 nor PRalpha alone was sufficient to induce leukemia upon transplantation in this model. The disease induced by Pim2 overexpression in PRalpha cells contained a slightly higher fraction of immature myeloid cells, compared with the previously described APL disease induced by PRalpha. However, it also clearly resembled an APL-like phenotype and showed signs of differentiation upon all-trans retinoic acid (ATRA) treatment in vitro. These results support the hypothesis that Pim2, which is also a known target of Flt3-ITD (another gene that cooperates with PML-RARalpha), cooperates with PRalpha to induce APL-like disease.