RESUMO
Aberrant transcriptional programs in combination with abnormal proliferative signaling drive leukemic transformation. These programs operate in normal hematopoiesis where they are involved in hematopoietic stem cell (HSC) proliferation and maintenance. Ets Related Gene (ERG) is a component of normal and leukemic stem cell signatures and high ERG expression is a risk factor for poor prognosis in acute myeloid leukemia (AML). However, mechanisms that underlie ERG expression in AML and how its expression relates to leukemic stemness are unknown. We report that ERG expression in AML is associated with activity of the ERG promoters and +85 stem cell enhancer and a heptad of transcription factors that combinatorially regulate genes in HSCs. Gene expression signatures derived from ERG promoter-stem cell enhancer and heptad activity are associated with clinical outcome when ERG expression alone fails. We also show that the heptad signature is associated with AMLs that lack somatic mutations in NPM1 and confers an adverse prognosis when associated with FLT3 mutations. Taken together, these results suggest that transcriptional regulators cooperate to establish or maintain primitive stem cell-like signatures in leukemic cells and that the underlying pattern of somatic mutations contributes to the development of these signatures and modulate their influence on clinical outcome.
Assuntos
Células-Tronco Hematopoéticas/metabolismo , Leucemia Mieloide Aguda/diagnóstico , Leucemia Mieloide Aguda/genética , Células-Tronco Neoplásicas/metabolismo , Fatores de Transcrição/fisiologia , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/fisiologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/fisiologia , Células Cultivadas , Subunidade alfa 2 de Fator de Ligação ao Core/genética , Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Subunidade alfa 2 de Fator de Ligação ao Core/fisiologia , Elementos Facilitadores Genéticos/genética , Fator de Transcrição GATA2/genética , Fator de Transcrição GATA2/metabolismo , Fator de Transcrição GATA2/fisiologia , Regulação Leucêmica da Expressão Gênica , Células-Tronco Hematopoéticas/fisiologia , Humanos , Células K562 , Proteínas com Domínio LIM/genética , Proteínas com Domínio LIM/metabolismo , Proteínas com Domínio LIM/fisiologia , Leucemia Mieloide Aguda/metabolismo , Leucemia Mieloide Aguda/patologia , Camundongos , Camundongos Transgênicos , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Proteínas de Neoplasias/fisiologia , Células-Tronco Neoplásicas/fisiologia , Nucleofosmina , Prognóstico , Proteína Proto-Oncogênica c-fli-1/genética , Proteína Proto-Oncogênica c-fli-1/metabolismo , Proteína Proto-Oncogênica c-fli-1/fisiologia , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas/fisiologia , Proteína 1 de Leucemia Linfocítica Aguda de Células T , Transativadores/genética , Transativadores/metabolismo , Transativadores/fisiologia , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Ativação Transcricional/genética , Regulador Transcricional ERGRESUMO
Hypoxia is emerging as an important characteristic of the hematopoietic stem cell (HSC) niche, but the molecular mechanisms contributing to quiescence, self-renewal, and survival remain elusive. Vascular endothelial growth factor A (VEGFA) is a key regulator of angiogenesis and hematopoiesis. Its expression is commonly regulated by hypoxia-inducible factors (HIF) that are functionally induced in low-oxygen conditions and that activate transcription by binding to hypoxia-response elements (HRE). Vegfa is indispensable for HSC survival, mediated by a cell-intrinsic, autocrine mechanism. We hypothesized that a hypoxic HSC microenvironment is required for maintenance or up-regulation of Vegfa expression in HSCs and therefore crucial for HSC survival. We have tested this hypothesis in the mouse model Vegfa(δ/δ), where the HRE in the Vegfa promoter is mutated, preventing HIF binding. Vegfa expression was reduced in highly purified HSCs from Vegfa(δ/δ) mice, showing that HSCs reside in hypoxic areas. Loss of hypoxia-regulated Vegfa expression increases the numbers of phenotypically defined hematopoietic stem and progenitor cells. However, HSC function was clearly impaired when assessed in competitive transplantation assays. Our data provide further evidence that HSCs reside in a hypoxic microenvironment and demonstrate a novel way in which the hypoxic niche affects HSC fate, via the hypoxia-VEGFA axis.
Assuntos
Células-Tronco Hematopoéticas/metabolismo , Oxigênio/metabolismo , Nicho de Células-Tronco/metabolismo , Fator A de Crescimento do Endotélio Vascular/genética , Animais , Hipóxia Celular , Células Cultivadas , Feminino , Citometria de Fluxo , Expressão Gênica , Genótipo , Lâmina de Crescimento/irrigação sanguínea , Lâmina de Crescimento/crescimento & desenvolvimento , Hematopoese/genética , Transplante de Células-Tronco Hematopoéticas , Células-Tronco Hematopoéticas/citologia , Hexoquinase/genética , Hexoquinase/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Fígado/citologia , Fígado/embriologia , Fígado/metabolismo , Masculino , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fosfoglicerato Quinase/genética , Fosfoglicerato Quinase/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Nicho de Células-Tronco/citologia , Fator A de Crescimento do Endotélio Vascular/metabolismoRESUMO
Perturbation in the expression and signaling pathways of vascular endothelial growth factor (VEGF) has been linked to pathogenesis of hematologic malignancies. We investigated the expression and clinical importance of VEGF and two of its receptors, VEGFR-1 and VEGFR-2, in childhood precursor B-cell acute lymphoblastic leukemia (pre-B ALL) by using immunohistochemistry. These angiogenic proteins were expressed in the majority of leukemic bone marrow samples. Notably, pre-B ALL patients had significantly increased expression of VEGFR-1 compared with no expression in the nonmalignant group, indicating a link between VEGFR-1 protein expression and pre-B ALL. These novel findings suggest that VEGFR-1 may have clinical importance in childhood pre-B ALL.
Assuntos
Técnicas Imunoenzimáticas , Proteínas de Neoplasias/análise , Leucemia-Linfoma Linfoblástico de Células Precursoras B/metabolismo , Fator A de Crescimento do Endotélio Vascular/análise , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/análise , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/análise , Adolescente , Medula Óssea/metabolismo , Medula Óssea/patologia , Criança , Pré-Escolar , Feminino , Seguimentos , Regulação Leucêmica da Expressão Gênica , Humanos , Lactente , Masculino , Proteínas de Neoplasias/biossíntese , Proteínas de Neoplasias/genética , Neovascularização Patológica/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras B/genética , Prognóstico , Fator A de Crescimento do Endotélio Vascular/biossíntese , Fator A de Crescimento do Endotélio Vascular/genética , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/biossíntese , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/genética , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/biossíntese , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/genéticaRESUMO
PTEN and SHP1 are tumor suppressor genes involved in the regulation of cell cycle control and apoptosis. The authors investigated the protein expression of PTEN and SHP1, by immunohistochemistry in tissue microarrays from bone marrow samples in children, diagnosed with acute lymphoblastic leukaemia and nonmalignant controls. PTEN was overexpressed in diagnostic ALL samples, while SHP1 showed a low expression. Both proteins showed a significant difference in expression compared to nonmalignant controls. The roles of PTEN and SHP1 are not well investigated in pediatric leukemia and could in the future play a role as prognostic factors.
