Asunto(s)
Regulación Neoplásica de la Expresión Génica , Proteínas Hedgehog/metabolismo , Meduloblastoma/metabolismo , Factores de Transcripción/metabolismo , Encéfalo/embriología , Biología Evolutiva/métodos , Regulación del Desarrollo de la Expresión Génica , Mutación de Línea Germinal , Humanos , Modelos Biológicos , Mutación , Transducción de Señal , Proteína con Dedos de Zinc GLI1RESUMEN
Recent studies have established miR-34a as a key effector of the p53 signaling pathway and have implicated its role in multiple cancer types. Here, we establish that miR-34a induces apoptosis, G2 arrest, and senescence in medulloblastoma and renders these cells more sensitive to chemotherapeutic agents. These effects are mediated in part by the direct post-transcriptional repression of the oncogenic MAGE-A gene family. We demonstrate that miR-34a directly targets the 3' untranslated regions of MAGE-A genes and decreases MAGE-A protein levels. This decrease in MAGE-A results in a concomitant increase in p53 and its associated transcriptional targets, p21/WAF1/CIP1 and, importantly, miR-34a. This establishes a positive feedback mechanism where miR-34a is not only induced by p53 but increases p53 mRNA and protein levels through the modulation of MAGE-A genes. Additionally, the forced expression of miR-34a or the knockdown of MAGE-A genes by small interfering RNA similarly sensitizes medulloblastoma cells to several classes of chemotherapeutic agents, including mitomycin C and cisplatin. Finally, the analysis of mRNA and micro-RNA transcriptional profiles of a series of primary medulloblastomas identifies a subset of tumors with low miR-34a expression and correspondingly high MAGE-A expression, suggesting the coordinate regulation of these genes. Our work establishes a role for miR-34a in modulating responsiveness to chemotherapy in medulloblastoma and presents a novel positive feedback mechanism involving miR-34a and p53, via direct targeting of MAGE-A.
Asunto(s)
Antígenos de Neoplasias/metabolismo , Antineoplásicos/farmacología , Resistencia a Antineoplásicos/genética , Meduloblastoma/tratamiento farmacológico , Meduloblastoma/metabolismo , MicroARNs/fisiología , Proteínas de Neoplasias/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , Antígenos de Neoplasias/genética , Apoptosis/efectos de los fármacos , Biomarcadores de Tumor/genética , Biomarcadores de Tumor/metabolismo , Western Blotting , Ciclo Celular/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Neoplasias Cerebelosas/tratamiento farmacológico , Neoplasias Cerebelosas/metabolismo , Neoplasias Cerebelosas/patología , Cisplatino/farmacología , Perfilación de la Expresión Génica , Humanos , Técnicas para Inmunoenzimas , Luciferasas/metabolismo , Meduloblastoma/patología , Antígenos Específicos del Melanoma , Mitomicina/farmacología , Proteínas de Neoplasias/antagonistas & inhibidores , Proteínas de Neoplasias/genética , Análisis de Secuencia por Matrices de Oligonucleótidos , ARN Mensajero/genética , ARN Interferente Pequeño/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Proteína p53 Supresora de Tumor/genéticaRESUMEN
PIWI regulates the proliferation and maintenance of germline stem cells in diverse organisms. The full-length 3.26 kb ziwi cDNA, the zebrafish homologue of piwi of Drosophila, encodes a putative protein of 858 amino acids. ZIWI is 65% homologous with the mouse and human PIWI, but only 38 and 33% with Caenorhabditis elegans and Drosophila PIWI, respectively. In adult zebrafish, ziwi is expressed exclusively in the gonads. In embryos and fry, its expression is detectable initially during segmentation and persisted for at least 4 weeks post hatching. During neurogenesis and organogenesis, its expression was detected in the CNS and fin buds. Starting from 24 hpf and later on, ziwi transcripts were found in the genital ridge.
Asunto(s)
Drosophila , Pez Cebra , Animales , Caenorhabditis elegans/genética , Células Germinativas/metabolismo , Gónadas/metabolismo , Humanos , Pez Cebra/genéticaRESUMEN
PIWI regulates the proliferation and maintenance of germline stem cells in diverse organisms. The full-length 3.26 kb ziwi cDNA, the zebrafish homologue of piwi of Drosophila, encodes a putative protein of 858 amino acids. ZIWI is 65% homologous with the mouse and human PIWI, but only 38 and 33% with Caenorhabditis elegans and Drosophila PIWI, respectively. In adult zebrafish, ziwi is expressed exclusively in the gonads. In embryos and fry, its expression is detectable initially during segmentation and persisted for at least 4 weeks post hatching. During neurogenesis and organogenesis, its expression was detected in the CNS and fin buds. Starting from 24 hpf and later on, ziwi transcripts were found in the genital ridge.