RESUMO
Mutation or epigenetic silencing of the transcription factor C/EBPα is observed in â¼10% of patients with acute myeloid leukemia (AML). In both cases, a common global gene expression profile is observed, but downstream targets relevant for leukemogenesis are not known. Here, we identify Sox4 as a direct target of C/EBPα whereby its expression is inversely correlated with C/EBPα activity. Downregulation of Sox4 abrogated increased self-renewal of leukemic cells and restored their differentiation. Gene expression profiles of leukemia-initiating cells (LICs) from both Sox4 overexpression and murine C/EBPα mutant AML models clustered together but differed from other types of AML. Our data demonstrate that Sox4 overexpression resulting from C/EBPα inactivation contributes to the development of leukemia with a distinct LIC phenotype.
Assuntos
Proteínas Estimuladoras de Ligação a CCAAT/genética , Regulação Leucêmica da Expressão Gênica , Leucemia Mieloide Aguda/genética , Fatores de Transcrição SOXC/genética , Animais , Proteínas Estimuladoras de Ligação a CCAAT/metabolismo , Diferenciação Celular , Proliferação de Células , Células Cultivadas , Técnicas de Silenciamento de Genes , Células-Tronco Hematopoéticas/fisiologia , Humanos , Leucemia Mieloide Aguda/patologia , Camundongos , Camundongos Knockout , Mutação , Células Mieloides/metabolismo , Transplante de Neoplasias , Células-Tronco Neoplásicas/metabolismo , Oncogenes , Fatores de Transcrição SOXC/metabolismo , TranscriptomaRESUMO
C/EBPs are a family of transcription factors that regulate growth control and differentiation of various tissues. We found that C/EBPγ is highly upregulated in a subset of acute myeloid leukemia (AML) samples characterized by C/EBPα hypermethylation/silencing. Similarly, C/EBPγ was upregulated in murine hematopoietic stem/progenitor cells lacking C/EBPα, as C/EBPα mediates C/EBPγ suppression. Studies in myeloid cells demonstrated that CEBPG overexpression blocked neutrophilic differentiation. Further, downregulation of Cebpg in murine Cebpa-deficient stem/progenitor cells or in human CEBPA-silenced AML samples restored granulocytic differentiation. In addition, treatment of these leukemias with demethylating agents restored the C/EBPα-C/EBPγ balance and upregulated the expression of myeloid differentiation markers. Our results indicate that C/EBPγ mediates the myeloid differentiation arrest induced by C/EBPα deficiency and that targeting the C/EBPα-C/EBPγ axis rescues neutrophilic differentiation in this unique subset of AMLs.
Assuntos
Proteínas Estimuladoras de Ligação a CCAAT/genética , Diferenciação Celular , Regulação Leucêmica da Expressão Gênica , Leucemia Mieloide Aguda/metabolismo , Animais , Azacitidina/análogos & derivados , Azacitidina/farmacologia , Proteínas Estimuladoras de Ligação a CCAAT/metabolismo , Células Cultivadas , Imunoprecipitação da Cromatina , Metilação de DNA , Metilases de Modificação do DNA/antagonistas & inibidores , Decitabina , Epigênese Genética , Genes Reporter , Fator Estimulador de Colônias de Granulócitos/fisiologia , Granulócitos , Humanos , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patologia , Luciferases de Renilla/biossíntese , Luciferases de Renilla/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Células Mieloides/metabolismo , Neutrófilos/metabolismo , Neutrófilos/fisiologia , Análise de Sequência com Séries de Oligonucleotídeos , Regiões Promotoras Genéticas , Ligação Proteica , Células-Tronco/metabolismo , Células-Tronco/fisiologia , Regulação para CimaRESUMO
Coactivator-associated arginine methyltransferase I (CARM1; PRMT4) regulates gene expression by multiple mechanisms including methylation of histones and coactivation of steroid receptor transcription. Mice lacking CARM1 are small, fail to breathe and die shortly after birth, demonstrating the crucial role of CARM1 in development. In adults, CARM1 is overexpressed in human grade-III breast tumors and prostate adenocarcinomas, and knockdown of CARM1 inhibits proliferation of breast and prostate cancer cell lines. Based on these observations, we hypothesized that loss of CARM1 in mouse embryos would inhibit pulmonary cell proliferation, resulting in respiratory distress. By contrast, we report here that loss of CARM1 results in hyperproliferation of pulmonary epithelial cells during embryonic development. The lungs of newborn mice lacking CARM1 have substantially reduced airspace compared with their wild-type littermates. In the absence of CARM1, alveolar type II cells show increased proliferation. Electron microscopic analyses demonstrate that lungs from mice lacking CARM1 have immature alveolar type II cells and an absence of alveolar type I cells. Gene expression analysis reveals a dysregulation of cell cycle genes and markers of differentiation in the Carm1 knockout lung. Furthermore, there is an overlap in gene expression in the Carm1 knockout and the glucocorticoid receptor knockout lung, suggesting that hyperproliferation and lack of maturation of the alveolar cells are at least in part caused by attenuation of glucocorticoid-mediated signaling. These results demonstrate for the first time that CARM1 inhibits pulmonary cell proliferation and is required for proper differentiation of alveolar cells.
