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Most architectures and models of language processing have been built upon a restricted view of language, which is limited to sentence processing. These approaches fail to capture one primordial characteristic: efficiency. Many facilitation effects are known to be at play in natural situations such as conversation (shallow processing, no real access to the lexicon, etc.) without any impact on the comprehension. In this study, on the basis of a new model integrating into a unique architecture, we present these facilitation effects for accessing the meaning into the classical compositional architecture. This model relies on two mechanisms, prediction and unification, and provides a unique architecture for the description of language processing in its natural environment.
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This article presents a different experiment examining the impact of feedback timing on its perception. Dialog sequences, featuring a main speaker's utterance followed by a listener's feedback, were extracted from spontaneous conversations. The original feedback instances were manipulated to be produced earlier, up to 1.5 s in advance, or to be delayed, up to 2 s later. Participants evaluated the feedback acceptability and engagement level of the listener. The findings reveal that 76% of the time feedback remains acceptable regardless of the delay. However, engagement decreases after a 1-s delay while no consistent effect is observed for feedback anticipation.
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Comunicación , Humanos , Masculino , Femenino , Adulto , Adulto Joven , Retroalimentación , Factores de Tiempo , Percepción del Habla/fisiologíaRESUMEN
According to the parallel architecture, syntactic and semantic information processing are two separate streams that interact selectively during language comprehension. While considerable effort is put into psycho- and neurolinguistics to understand the interchange of processing mechanisms in human comprehension, the nature of this interaction in recent neural Large Language Models remains elusive. In this article, we revisit influential linguistic and behavioral experiments and evaluate the ability of a large language model, GPT-3, to perform these tasks. The model can solve semantic tasks autonomously from syntactic realization in a manner that resembles human behavior. However, the outcomes present a complex and variegated picture, leaving open the question of how Language Models could learn structured conceptual representations.
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Optimizing the biomarker combination to be analyzed in liquid biopsies should improve personalized medicine. We developed a method to purify circulating cell-free mRNAs from plasma samples and to quantify them by RT-qPCR. We selected three candidate colorectal cancer biomarkers (B2M, TIMP-1, and CLU). Their mRNA levels were significantly higher in plasma of patients with metastatic colorectal cancer patients (mCRC) (n = 107) than in healthy individuals (HI) (n = 53). To increase the discriminating performance of our method, we analyzed the sum of the three mRNA levels (BTC index). The area under the ROC curve (AUC) to estimate the BTC index capacity to discriminate between mCRC and HI plasma was 0.903. We also determined the optimal BTC index cut-off to distinguish between plasma samples, with 82% of sensitivity and 93% of specificity. By using mRNA as a novel liquid biopsy analytical parameter, our method has the potential to facilitate rapid screening of CRCm.
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Neoplasias Colorrectales , Humanos , ARN Mensajero/genética , Neoplasias Colorrectales/diagnóstico , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/patología , Biomarcadores de Tumor/genética , Curva ROCRESUMEN
The HMG-box transcription factor Sox9 is expressed in the intestinal epithelium, specifically, in stem/progenitor cells and in Paneth cells. Sox9 expression requires an active beta-catenin-Tcf complex, the transcriptional effector of the Wnt pathway. This pathway is critical for numerous aspects of the intestinal epithelium physiopathology, but processes that specify the cell response to such multipotential signals still remain to be identified. We inactivated the Sox9 gene in the intestinal epithelium to analyze its physiological function. Sox9 inactivation affected differentiation throughout the intestinal epithelium, with a disappearance of Paneth cells and a decrease of the goblet cell lineage. Additionally, the morphology of the colon epithelium was severely altered. We detected general hyperplasia and local crypt dysplasia in the intestine, and Wnt pathway target genes were up-regulated. These results highlight the central position of Sox9 as both a transcriptional target and a regulator of the Wnt pathway in the regulation of intestinal epithelium homeostasis.
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Colon/metabolismo , Proteínas del Grupo de Alta Movilidad/metabolismo , Células de Paneth/metabolismo , Factores de Transcripción/metabolismo , Animales , Diferenciación Celular , Línea Celular Tumoral , Proliferación Celular , Colon/citología , Proteínas del Grupo de Alta Movilidad/genética , Humanos , Ratones , Ratones Endogámicos C57BL , Células de Paneth/citología , Factor de Transcripción SOX9 , Factores de Transcripción/genéticaRESUMEN
To unequivocally address their unresolved intimate structures in blood, we scrutinized the size distribution of circulating cell-free DNA (cfDNA) using whole-genome sequencing (WGS) from both double- and single-strand DNA library preparations (DSP and SSP, n = 7) and using quantitative PCR (Q-PCR, n = 116). The size profile in healthy individuals was remarkably homogenous when using DSP sequencing or SSP sequencing. CfDNA size profile had a characteristic nucleosome fragmentation pattern. Overall, our data indicate that the proportion of cfDNA inserted in mono-nucleosomes, di-nucleosomes, and chromatin of higher molecular size (>1000 bp) can be estimated as 67.5% to 80%, 9.4% to 11.5%, and 8.5% to 21.0%, respectively. Although DNA on single chromatosomes or mono-nucleosomes is detectable, our data revealed that cfDNA is highly nicked (97%-98%) on those structures, which appear to be subjected to continuous nuclease activity in the bloodstream. Fragments analysis allows the distinction of cfDNA of different origins: first, cfDNA size profile analysis may be useful in cfDNA extract quality control; second, subtle but reliable differences between metastatic colorectal cancer patients and healthy individuals vary with the proportion of malignant cell-derived cfDNA in plasma extracts, pointing to a higher degree of cfDNA fragmentation and nuclease activity in samples with high malignant cell cfDNA content.
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Ácidos Nucleicos Libres de Células/sangre , Ácidos Nucleicos Libres de Células/genética , Neoplasias Colorrectales/sangre , Neoplasias Colorrectales/genética , Adulto , ADN Tumoral Circulante/sangre , ADN Tumoral Circulante/genética , Neoplasias Colorrectales/patología , ADN/sangre , ADN de Cadena Simple/sangre , Femenino , Humanos , Masculino , Persona de Mediana Edad , Reacción en Cadena de la Polimerasa/métodos , Secuenciación Completa del Genoma/métodosRESUMEN
RIP140 is a major transcriptional coregulator of gut homeostasis and tumorigenesis through the regulation of Wnt/APC signaling. Here, we investigated the effect of RIP140 on Paneth cell differentiation and its interplay with the transcription factor SOX9. Using loss of function mouse models, human colon cancer cells, and tumor microarray data sets we evaluated the role of RIP140 in SOX9 expression and activity using RT-qPCR, immunohistochemistry, luciferase reporter assays, and GST-pull down. We first evidence that RIP140 strongly represses the Paneth cell lineage in the intestinal epithelium cells by inhibiting Sox9 expression. We then demonstrate that RIP140 interacts with SOX9 and inhibits its transcriptional activity. Our results reveal that the Wnt signaling pathway exerts an opposite regulation on SOX9 and RIP140. Finally, the levels of expression of RIP140 and SOX9 exhibit a reverse response and prognosis value in human colorectal cancer biopsies. This work highlights an intimate transcriptional cross-talk between RIP140 and SOX9 in intestinal physiopathology.
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TCF and SOX proteins belong to the high mobility group box transcription factor family. Whereas TCFs, the transcriptional effectors of the Wnt pathway, have been widely implicated in the development, homeostasis and disease of the intestine epithelium, little is known about the function of the SOX proteins in this tissue. Here, we identified SOX9 in a SOX expression screening in the mouse fetal intestine. We report that the SOX9 protein is expressed in the intestinal epithelium in a pattern characteristic of Wnt targets. We provide in vitro and in vivo evidence that a bipartite beta-catenin/TCF4 transcription factor, the effector of the Wnt signaling pathway, is required for SOX9 expression in epithelial cells. Finally, in colon epithelium-derived cells, SOX9 transcriptionally represses the CDX2 and MUC2 genes, normally expressed in the mature villus cells of the intestinal epithelium, and may therefore contribute to the Wnt-dependent maintenance of a progenitor cell phenotype.
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Proteínas del Grupo de Alta Movilidad/metabolismo , Proteínas de Homeodominio/metabolismo , Mucinas/metabolismo , Factores de Transcripción/metabolismo , Animales , Northern Blotting , Western Blotting , Factor de Transcripción CDX2 , Carcinoma/metabolismo , Diferenciación Celular , Línea Celular Tumoral , Núcleo Celular/metabolismo , Neoplasias del Colon/metabolismo , Proteínas del Citoesqueleto/metabolismo , ADN/metabolismo , Epitelio/metabolismo , Regulación Neoplásica de la Expresión Génica , Humanos , Procesamiento de Imagen Asistido por Computador , Inmunohistoquímica , Mucosa Intestinal/metabolismo , Ratones , Microscopía Fluorescente , Mucina 2 , Trasplante de Neoplasias , Fenotipo , ARN/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factor de Transcripción SOX9 , Transducción de Señal , Células Madre/metabolismo , Transactivadores/metabolismo , Transcripción Genética , Transfección , beta CateninaRESUMEN
Differently from cytotoxic chemotherapies, targeted therapies do not necessarily drive cancer cells toward death, but reduce cell proliferation, angiogenesis, and/or prevent metastasis without affecting healthy cells. Oncogenic proteins that are hyperactivated and/or overexpressed in cancer cells are prime targets for such therapies. On the other hand, the activity of tumor suppressor proteins is more difficult to harness. Here, we identified a short SOX9 sequence (S9pep) located at the hinge between the HMG DNA-binding domain and the SOX-E central conserved domain that mimics SOX9 tumor-suppressive properties. Doxycycline-induced S9pep expression in DLD-1 colorectal cancer cells inhibited the growth potential of these cells, including colorectal cancer stem cells, restored cell-cell contact inhibition, and inhibited the activity of the oncogenic Wnt/ß-catenin signaling pathway. It also significantly decreased tumor growth in BALB/cAnNCrl mice grafted with mouse doxycycline-inducible CT26 colorectal cancer cells in which S9pep was induced by treating them with doxycycline. As the Wnt/ß-catenin signaling pathway is constitutively activated in 80% of colorectal cancer and SOX9-inactivating mutations are present in up to 11% of colorectal cancer, S9pep could be a promising starting point for the development of a peptide-based therapeutic approach to restore a SOX9-like tumor suppressor function in colorectal cancer.
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Mimetismo Biológico , Péptidos/farmacología , Factor de Transcripción SOX9/química , Factor de Transcripción SOX9/metabolismo , Secuencia de Aminoácidos , Animales , Antineoplásicos/química , Antineoplásicos/farmacología , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Neoplasias del Colon/metabolismo , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Humanos , Ratones , Péptidos/química , Proteínas Proto-Oncogénicas c-myc , Esferoides Celulares , Células Tumorales Cultivadas , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Inactivating mutations of the tumor suppressor Adenomatosis Polyposis Coli (APC), which are found in familial adenomatosis polyposis and in 80% of sporadic colorectal cancers (CRC), result in constitutive activation of the Wnt/ß-catenin pathway and tumor development in the intestine. These mutations disconnect the Wnt/ß-catenin pathway from its Wnt extracellular signal by inactivating the APC/GSK3-ß/axin destruction complex of ß-catenin. This results in sustained nuclear accumulation of ß-catenin, followed by ß-catenin-dependent co-transcriptional activation of Wnt/ß-catenin target genes. Thus, mechanisms acting downstream of APC, such as those controlling ß-catenin stability and/or co-transcriptional activity, are attractive targets for CRC treatment. Protein Kinase C-α (PKCα) phosphorylates the orphan receptor RORα that then inhibits ß-catenin co-transcriptional activity. PKCα also phosphorylates ß-catenin, leading to its degradation by the proteasome. Here, using both in vitro (DLD-1 cells) and in vivo (C57BL/6J mice) PKCα knock-in models, we investigated whether enhancing PKCα function could be beneficial in CRC treatment. We found that PKCα is infrequently mutated in CRC samples, and that inducing PKCα function is not deleterious for the normal intestinal epithelium. Conversely, di-terpene ester-induced PKCα activity triggers CRC cell death. Together, these data indicate that PKCα is a relevant drug target for CRC treatment.
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To our knowledge, this is the first comprehensive study on the influence of several pre-analytical and demographic parameters that could be a source of variability in the quantification of nuclear and mitochondrial circulating DNA (NcirDNA and McirDNA). We report data from a total of 222 subjects, 104 healthy individuals and 118 metastatic colorectal cancer (mCRC) patients. Approximately 50,000 and 3,000-fold more mitochondrial than nuclear genome copies were found in the plasma of healthy individuals and mCRC patients, respectively. In healthy individuals, NcirDNA concentration was statistically influenced by age (p = 0.009) and gender (p = 0.048). Multivariate analysis with logistic regression specified that age over 47 years-old was predictive to have higher NcirDNA concentration (OR = 2.41; p = 0.033). McirDNA concentration was independent of age and gender in healthy individuals. In mCRC patients, NcirDNA and McirDNA levels were independent of age, gender, delay between food intake and blood collection, and plasma aspect, either with univariate or multivariate analysis. Nonetheless, ad hoc study suggested that menopause and blood collection time might have tendency to influence cirDNA quantification. In addition, high significant statistical differences were found between mCRC patients and healthy individuals for NcirDNA (p < 0.0001), McirDNA (p < 0.0001) and McirDNA/NcirDNA ratio (p < 0.0001). NcirDNA and McirDNA levels do not vary in the same way with regards to cancer vs healthy status, pre-analytical and demographic factors.
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ADN Tumoral Circulante/sangre , Neoplasias Colorrectales/sangre , ADN Mitocondrial/sangre , Adulto , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
A constitutive activation of the Wnt/ß-catenin pathway is an initiating event in colon carcinogenesis. We developed colon cancer cells models that highlight the non-selectivity of previously described inhibitors of the Wnt pathway and we propose our model as a suitable screening system for inhibitors of the pathway.
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The human carcinoembryonic antigen (CEA) is overexpressed in many types of human cancers and is commonly used as a clinical marker. In colon cancer, this overexpression protects cells against apoptosis and contributes to carcinogenesis. Therefore, CEA-expressing cells as well as CEA expression itself constitute potential therapeutic targets. In this report, we show that the transcription factor SOX9 down-regulates CEA gene expression and, as a probable consequence, induces apoptosis in the human colon carcinoma cell line HT29Cl.16E.
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Antígeno Carcinoembrionario/genética , Neoplasias del Colon/genética , Regulación Neoplásica de la Expresión Génica/fisiología , Proteínas del Grupo de Alta Movilidad/fisiología , Factores de Transcripción/fisiología , Apoptosis/fisiología , Antígeno Carcinoembrionario/biosíntesis , Diferenciación Celular/fisiología , Neoplasias del Colon/inmunología , Neoplasias del Colon/patología , Regulación hacia Abajo/fisiología , Células HT29 , Proteínas del Grupo de Alta Movilidad/biosíntesis , Proteínas del Grupo de Alta Movilidad/genética , Humanos , Regiones Promotoras Genéticas , Factor de Transcripción SOX9 , Factores de Transcripción/biosíntesis , Factores de Transcripción/genéticaRESUMEN
A member of the Sry-related HMG-box family of transcription factors (SOX9) is a transcription factor that belongs to the superfamily of High Mobility Group (HMG) domain transcription factors. SOX9 is expressed in a variety of tissues, including as the intestinal epithelium, where it is now recognised as an important actor for homeostasis. Beside, a high level of SOX9 has recently been correlated with a good prognosis for stage II colorectal cancers. However, growing evidence indicates that deciphering the function of SOX9 in the intestine has to take into account a dose-dependent effect of SOX9. Given the recurrent controversies and the lack of a state of the art as to whether SOX9 behaves like a tumour suppressor or an oncogen in the intestine epithelium, it is time to provide an update of the accumulated knowledge about the biological function of SOX9 in the intestine and about the role of SOX9 in colorectal cancers.
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Biomarcadores de Tumor/metabolismo , Neoplasias Colorrectales/metabolismo , Células Epiteliales/metabolismo , Células Madre Neoplásicas/metabolismo , Factor de Transcripción SOX9/metabolismo , Proteínas Supresoras de Tumor/metabolismo , Animales , Biomarcadores de Tumor/genética , Proliferación Celular , Senescencia Celular , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/patología , Neoplasias Colorrectales/terapia , Células Epiteliales/patología , Regulación Neoplásica de la Expresión Génica , Heterocigoto , Humanos , Mutación , Recurrencia Local de Neoplasia , Estadificación de Neoplasias , Células Madre Neoplásicas/patología , Factores de Riesgo , Factor de Transcripción SOX9/genética , Transducción de Señal , Resultado del Tratamiento , Proteínas Supresoras de Tumor/genéticaRESUMEN
SOX9 inactivation is frequent in colorectal cancer (CRC) due to SOX9 gene mutations and/or to ectopic expression of MiniSOX9, a dominant negative inhibitor of SOX9. In the present study, we report a heterozygous L142P inactivating mutation of SOX9 in the DLD-1 CRC cell line and we demonstrate that the conditional expression of a wild type SOX9 in this cell line inhibits cell growth, clonal capacity and colonosphere formation while decreasing both the activity of the oncogenic Wnt/ß-catenin signaling pathway and the expression of the c-myc oncogene. This activity does not require SOX9 transcriptional function but, rather, involves an interaction of SOX9 with nuclear ß-catenin. Furthermore, we report that SOX9 inhibits tumor development when conditionally expressed in CRC cells injected either subcutaneous or intraperitoneous in BALB/c mice as an abdominal metastasis model. These observations argue in favor of a tumor suppressor activity for SOX9. As an siRNA targeting SOX9 paradoxically also inhibits DLD-1 and HCT116 CRC cell growth, we conclude that there is a critical level of endogenous active SOX9 needed to maintain CRC cell growth.
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Proliferación Celular , Neoplasias Colorrectales/metabolismo , Factor de Transcripción SOX9/metabolismo , Vía de Señalización Wnt , Animales , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/patología , Regulación Neoplásica de la Expresión Génica , Células HCT116 , Heterocigoto , Humanos , Ratones Endogámicos BALB C , Mutación , Neoplasias Peritoneales/metabolismo , Neoplasias Peritoneales/secundario , Proteínas Proto-Oncogénicas c-myc/genética , Proteínas Proto-Oncogénicas c-myc/metabolismo , Interferencia de ARN , Factor de Transcripción SOX9/genética , Factores de Tiempo , Transfección , Carga Tumoral , beta Catenina/genética , beta Catenina/metabolismoRESUMEN
Histone lysine acetylation is an epigenetic mark regulated by histone acetyltransferases and histone deacetylases (HDAC) which plays an important role in tumorigenesis. In this study, we observed a strong overexpression of class IIa HDAC9, at the mRNA and protein levels, in the most aggressive human breast cancer cell lines (i.e. in basal breast cancer cells vs luminal ones or in malignant vs begnin MCF10A breast epithelial cell lines). HDAC9 overexpression was associated with higher rates of gene transcription and increased epigenetic marks on the HDAC9 promoter. Ectopic expression of HDAC9 in MCF7 luminal breast cancer cells led to an increase in cell proliferation and to a decrease in apoptosis. These effects were associated with a deregulated expression of several genes controlled by HDAC inhibitors such as CDKN1A, BAX and TNFRSF10A. Inversely, knock-down of HDAC9 expression in MDA-MB436 basal breast cancer cells reduced cell proliferation. Moreover, high HDAC9 expression decreased the efficacy of HDAC inhibitors to reduce cell proliferation and to regulate CDKN1A gene expression. Interestingly, the gene encoding the transcription factor SOX9 was identified by a global transcriptomic approach as an HDAC9 target gene. In stably transfected MCF7 cells, SOX9 silencing significantly decreased HDAC9 mitogenic activity. Finally, in a large panel of breast cancer biopsies, HDAC9 expression was significantly increased in tumors of the basal subtype, correlated with SOX9 expression and associated with poor prognosis. Altogether, these results indicate that HDAC9 is a key factor involved in mammary carcinogenesis and in the response to HDAC inhibitors.
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Neoplasias de la Mama/enzimología , Proliferación Celular/efectos de los fármacos , Inhibidores de Histona Desacetilasas/farmacología , Proteínas Represoras/antagonistas & inhibidores , Apoptosis/efectos de los fármacos , Apoptosis/genética , Western Blotting , Neoplasias de la Mama/genética , Neoplasias de la Mama/patología , Línea Celular , Línea Celular Tumoral , Proliferación Celular/genética , Femenino , Perfilación de la Expresión Génica/métodos , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Histona Desacetilasas/genética , Histona Desacetilasas/metabolismo , Humanos , Células MCF-7 , Microscopía Fluorescente , Interferencia de ARN , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Factor de Transcripción SOX9/genética , Factor de Transcripción SOX9/metabolismoRESUMEN
1. The ATP-sensitive potassium channel (K(ATP)) of pancreatic beta-cells is composed of the sulphonylurea-binding protein, SUR1, and the inwardly rectifying K(+) channel subunit, Kir6.2. We have characterized two novel isoforms of rat SUR1 in the RINm5F insulin-secreting cell line. 2. SUR1A2 is an allelic variant with a single amino acid change in the first nucleotide-binding domain. Coinjection of SUR1A2 plus Kir6.2 into Xenopus oocytes or expression of a SUR1A2-Kir6.2 tandem in HEK-293 cells yielded large currents with characteristics similar to the wild-type K(ATP) channel. 3. SUR1BDelta31, detected in several human tissues, is a splice variant of the rat SUR1 gene that lacks exon 31 of the corresponding human SUR1 gene. SUR1BDelta31 lacks the TM16-TM17 transmembrane-spanning helices leading to a protein with a different transmembrane topology. Coinjection of SUR1BDelta31 plus Kir6.2 into Xenopus oocytes or expression of the Kir6.2/SUR1BDelta31 tandem construct in HEK-293 cells did not result in any current, and a surface expression assay indicated that this channel does not reach the plasma membrane. 4. SUR1A2 and SUR1A1 proteins expressed in HEK-293 cells display similar binding affinities for [(3)H]-glibenclamide, while SUR1BDelta31 shows a 500-fold lower affinity. 5. These findings confirm that TM16-TM17 of SUR1 are important for high-affinity glibenclamide binding and that their deletion impairs trafficking of the K(ATP) channel to the surface membrane.
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Transportadoras de Casetes de Unión a ATP , Canales de Potasio de Rectificación Interna/fisiología , Canales de Potasio/fisiología , Receptores de Droga/fisiología , Adenosina Trifosfato/metabolismo , Animales , Línea Celular , Gliburida/metabolismo , Humanos , Immunoblotting , Insulina/metabolismo , Secreción de Insulina , Oocitos , Especificidad de Órganos , Técnicas de Placa-Clamp , Reacción en Cadena de la Polimerasa , Canales de Potasio/genética , Canales de Potasio/metabolismo , Canales de Potasio de Rectificación Interna/efectos de los fármacos , Canales de Potasio de Rectificación Interna/metabolismo , Isoformas de Proteínas , Ensayo de Unión Radioligante , Ratas , Receptores de Droga/genética , Receptores de Droga/metabolismo , Receptores de Sulfonilureas , XenopusRESUMEN
Since the mid 1970s, cancer has been described as a process of Darwinian evolution, with somatic cellular selection and evolution being the fundamental processes leading to malignancy and its many manifestations (neoangiogenesis, evasion of the immune system, metastasis, and resistance to therapies). Historically, little attention has been placed on applications of evolutionary biology to understanding and controlling neoplastic progression and to prevent therapeutic failures. This is now beginning to change, and there is a growing international interest in the interface between cancer and evolutionary biology. The objective of this introduction is first to describe the basic ideas and concepts linking evolutionary biology to cancer. We then present four major fronts where the evolutionary perspective is most developed, namely laboratory and clinical models, mathematical models, databases, and techniques and assays. Finally, we discuss several of the most promising challenges and future prospects in this interdisciplinary research direction in the war against cancer.
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Variations of protein kinase C (PKC) expression greatly influence the proliferation-to-differentiation transition (PDT) of intestinal epithelial cells and might have an important impact on intestinal tumorigenesis. We demonstrate here that the expression of PKCalpha in proliferating intestinal epithelial cells is repressed both in vitro and in vivo by the SOX9 transcription factor. This repression does not require DNA binding of the SOX9 high-mobility group (HMG) domain but is mediated through a new mechanism of SOX9 action requiring the central and highly conserved region of SOXE members. Because SOX9 expression is itself upregulated by Wnt-APC signaling in intestinal epithelial cells, the present study points out this transcription factor as a molecular link between the Wnt-APC pathway and PKCalpha. These results provide a potential explanation for the decrease of PKCalpha expression in colorectal cancers with constitutive activation of the Wnt-APC pathway.
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Regulación Enzimológica de la Expresión Génica , Mucosa Intestinal/metabolismo , Proteína Quinasa C-alfa/metabolismo , Factor de Transcripción SOX9/metabolismo , Proteína de la Poliposis Adenomatosa del Colon/metabolismo , Animales , Línea Celular , Células Epiteliales/citología , Células Epiteliales/metabolismo , Humanos , Mucosa Intestinal/citología , Proteína Quinasa C-alfa/genética , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Factor de Transcripción SOX9/genética , Transducción de Señal/fisiología , Factor de Transcripción Sp1/genética , Factor de Transcripción Sp1/metabolismo , Transcripción Genética , Proteínas Wnt/metabolismoRESUMEN
Tight junctions have recently emerged as essential signaling regulators of proliferation and differentiation in epithelial tissues. Here, we aimed to identify the factors regulating claudin-7 expression in the colon, and analyzed the consequences of claudin-7 overexpression in colorectal carcinoma (CRC). In healthy human colonic crypts, claudin-7 expression was found to be low in the stem/progenitor cell compartment, where Tcf-4 activity is high, but strong in differentiated and postmitotic cells, where Tcf-4 is inactive. In contrast, claudin-7 was overexpressed in areas with high Tcf-4 target gene levels in CRC samples. In vitro, Tcf-4 was able to repress claudin-7 expression, and the high mobility group-box transcription factor Sox-9 was identified as an essential mediator of this effect. Claudin-7 was strongly expressed in the intestine of Sox-9-deficient mice and in CRC cells with low Sox transcriptional activity. Sox-9 overexpression in these cells reinstated claudin-7 repression, and residual claudin-7 was no longer localized along the basolateral membrane, but was instead restricted to tight junctions. Using HT-29Cl.16E CRC cell spheroids, we found that Sox-9-induced polarization was completely reversed after virus-mediated claudin-7 overexpression. Claudin-7 overexpression in this context increased Tcf-4 target gene expression, proliferation, and tumorigenicity after injection in nude mice. Our results indicate that Tcf-4 maintains low levels of claudin-7 at the bottom of colonic crypts, acting via Sox-9. This negative regulation seems to be defective in CRC, possibly due to decreased Sox-9 activity, and the resulting claudin-7 overexpression promotes a loss of tumor cell polarization and contributes to tumorigenesis.