RESUMEN
The Wnt pathway is abnormally activated in the majority of colorectal cancers, and significant knowledge has been gained in understanding its role in tumor initiation. However, the mechanisms of metastatic outgrowth in colorectal cancer remain a major challenge. We report that autophagy-dependent metabolic adaptation and survival of metastatic colorectal cancer cells is regulated by the target of oncogenic Wnt signaling, homeobox transcription factor PROX1, expressed by a subpopulation of colon cancer progenitor/stem cells. We identify direct PROX1 target genes and show that repression of a pro-apoptotic member of the BCL2 family, BCL2L15, is important for survival of PROX1(+) cells under metabolic stress. PROX1 inactivation after the establishment of metastases prevented further growth of lesions. Furthermore, autophagy inhibition efficiently targeted metastatic PROX1(+) cells, suggesting a potential therapeutic approach. These data identify PROX1 as a key regulator of the transcriptional network contributing to metastases outgrowth in colorectal cancer.
Asunto(s)
Neoplasias del Colon/patología , Proteínas de Homeodominio/metabolismo , Proteínas Supresoras de Tumor/metabolismo , Proteínas Wnt/metabolismo , Animales , Apoptosis/efectos de los fármacos , Técnicas de Cultivo de Célula , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Cloroquina/toxicidad , Neoplasias del Colon/metabolismo , Neoplasias del Colon/mortalidad , Proteínas de Homeodominio/antagonistas & inhibidores , Proteínas de Homeodominio/genética , Humanos , Neoplasias Hepáticas/patología , Neoplasias Hepáticas/secundario , Neoplasias Pulmonares/patología , Neoplasias Pulmonares/secundario , Ganglios Linfáticos/patología , Metástasis Linfática , Ratones , Ratones Endogámicos NOD , Células Madre Neoplásicas/metabolismo , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Interferencia de ARN , Estrés Fisiológico , Proteínas Supresoras de Tumor/antagonistas & inhibidores , Proteínas Supresoras de Tumor/genética , Vía de Señalización WntRESUMEN
HuR emerged as a posttranscriptional regulator of mRNAs involved in cellular control, stress, and immunity but its role in governing such responses remains elusive. In this study, we assessed HuR's role in the staged progression of thymic T cell differentiation by means of its genetic ablation. Mice with an early deletion of HuR in thymocytes possess enlarged thymi but display a substantial loss of peripheral T cells. We show that this discordant phenotype related to specific defects in thymic cellular processes, which demonstrated HuR's involvement in: 1) intrinsic checkpoint signals suppressing the cell cycle of immature thymocyte progenitors, 2) TCR and antigenic signals promoting the activation and positive selection of mature thymocytes, 3) antigenic and death-receptor signals promoting thymocyte deletion, and 4) chemokine signals driving the egress of postselection thymocytes to the periphery. The cellular consequences of HuR's dysfunction were underlined by the aberrant expression of selective cell cycle regulators, TCR, and death-receptor signaling components. Our studies reveal the signal-dependent context of HuR's cellular activities in thymocytes and its importance in the generation of a physiological T cell pool.
Asunto(s)
Antígenos de Superficie/fisiología , Proteínas de Unión al ARN/fisiología , Linfocitos T/citología , Timo/inmunología , Animales , Proteínas de Ciclo Celular , Diferenciación Celular , Quimiocinas , Proteínas ELAV , Proteína 1 Similar a ELAV , Ratones , Receptores de Muerte Celular , Células Madre/citología , Timo/citologíaRESUMEN
HuR is an RNA-binding protein implicated in a diverse array of pathophysiological processes due to its effects on the posttranscriptional regulation of AU- and U-rich mRNAs. Here we reveal HuR's requirement in embryonic development through its genetic ablation. Obligatory HuR-null embryos exhibited a stage retardation phenotype and failed to survive beyond midgestation. By means of conditional transgenesis, we restricted HuR's mutation in either embryonic or endothelial compartments to demonstrate that embryonic lethality is consequent to defects in extraembryonic placenta. HuR's absence impaired the invagination of allantoic capillaries into the chorionic trophoblast layer and the differentiation of syncytiotrophoblast cells that control the morphogenesis and vascularization of the placental labyrinth and fetal support. HuR-null embryos rescued from these placental defects proceeded to subsequent developmental stages but displayed defects in skeletal ossification, fusions in limb elements, and asplenia. By coupling gene expression measurements, data meta-analysis, and HuR-RNA association assays, we identified transcription and growth factor mRNAs controlled by HuR, primarily at the posttranscriptional level, to guide morphogenesis, specification, and patterning. Collectively, our data demonstrate the dominant role of HuR in organizing gene expression programs guiding placental labyrinth morphogenesis, skeletal specification patterns, and splenic ontogeny.
Asunto(s)
Antígenos de Superficie/metabolismo , Morfogénesis , Placenta , Proteínas de Unión al ARN/metabolismo , Animales , Antígenos de Superficie/genética , Células Cultivadas , Proteínas ELAV , Proteína 1 Similar a ELAV , Femenino , Regulación del Desarrollo de la Expresión Génica , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Anomalías Musculoesqueléticas/genética , Anomalías Musculoesqueléticas/patología , Fenotipo , Placenta/anatomía & histología , Placenta/embriología , Embarazo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Proteínas de Unión al ARN/genética , Bazo/anomalías , Bazo/embriologíaRESUMEN
The oncofetal CRD-BP/IMP1 RNA binding protein regulates posttranscriptionally a handful of RNA transcripts, implicated in cell adhesion and invadopodia formation and was recently identified as a target of the beta-catenin/Tcf transcription factor that is constitutively activated in colorectal carcinomas (CRCs). The expression of CRD-BP/IMP1 was studied in normal adult intestines and CRCs. In normal mucosa, CRD-BP/IMP1 immunoreactivity was observed in few scattered cells located predominantly at or near the bottom of the crypts, whereas in CRCs the protein was detectable in tumor cells of 50% of the specimens analyzed. CRD-BP/IMP1 mRNA expression was measured by qRT-PCR in 78 CRCs. Thirty-two (41%) of the specimens were negative or had negligible expression, whereas the remaining forty-six (59%) expressed a wide range of CRD-BP/IMP1 mRNA levels. CRD-BP/IMP1 mRNA expression correlated with that of the putative stem/progenitor cell marker Musashi-1 mRNA (p = 0. 035). CRD-BP/IMP1 positive tumors metastasized and/or recurred more frequently (p = 0.001) and its expression defined a group of patients with shorter survival (p = 0.014). Furthermore, in a multivariate analysis CRD-BP/IMP1 expression was found to be an independent predictor of survival (p = 0.015). For stage I & II patients, the differences in metastasis/recurrence and survival rates remained significant (p = 0.001 and 0.033, respectively). These findings indicate that CRD-BP/IMP1 positive tumors exhibit early disease dissemination and unfavorable prognosis.
Asunto(s)
Neoplasias del Colon/metabolismo , Proteínas de Unión al ARN/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Expresión Génica , Humanos , Inmunohistoquímica , Mucosa Intestinal/metabolismo , Masculino , Persona de Mediana Edad , Pronóstico , ARN Mensajero/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
HuR is an RNA binding protein with an alleged role in the posttranscriptional activation of inflammatory mRNAs bearing AU-rich elements (AREs). Here, we show that the inducible increase of HuR in murine innate compartments suppresses inflammatory responses in vivo. In macrophages, HuR overexpression induced the translational silencing of specific cytokine mRNAs despite positive or nominal effects on their corresponding turnover. By using a model system of ARE dysfunction, we demonstrate that HuR does not alter the accumulation of target mRNAs in the absence of the destabilizing functions of Tristetraprolin but synergizes with the translational silencer TIA-1 to reduce the translation of cytokine mRNAs. Our data suggest that HuR acts in a pleiotropic fashion in inflammation through its functional interactions with specific mRNA subsets and negative posttranscriptional modules.