389 research outputs found
p38α, the β-catenin chromatin associated kinase, as promising target in colorectal cancer stem cells for personalized therapy
No full textColorectal cancer (CRC) is the third most frequent malignancy, but the second cause of death for tumor in the western population. Only 14% of patients with advanced and metastatic disease survive five years from diagnosis. Recently, it has been shown that tumor relapse and chemoresistance depend on a small population of cells, called cancer stem cells (CSCs). Current evidence indicates that the Wnt cascade is the main driver in controlling CSC fate; the key player in this pathway is β-catenin, a cytoplasmic protein whose stability is regulated by the so-called “destruction complex”. During carcinogenesis, the increasing amount of β-catenin resulting from APC inactivation translocates into the nucleus, causing the transcriptional activation of several mitogenic genes, including c-Myc. c-Myc is one of the most important factors involved in CRC initiation and progression; indeed, it functions as a link connecting malignancy with stemness. During colorectal carcinogenesis, c-Myc is maintained upregulated through β-catenin-mediated transcriptional activation and ERK-mediated post-translational stabilization. Our data showed that p38α, a kinase involved in CRC metabolism and survival, contributes to both mechanisms. Previous reports in other tissues provided evidence that Wnt3a can activate p38, and the p38 pathway feeds into the canonical Wnt/β-catenin pathway at least at the level of GSK3β. Our findings also highlighted that CRC cells and colorectal cancer stem cells (CRC-SCs) have higher levels of activated p38 than their normal counterparts, and experiments using kinase-specific inhibitors revealed that these cells are “addicted” to p38 activity. Importantly, we found that p38α co-immunoprecipitates with β-catenin in both normal and cancer cells; however, these proteins are confined to the cytoplasm in colonocytes, while they significantly occupy discrete nuclear regions in CRC cells, CRC-SCs, and in vivo models. These data were further corroborated by the inhibitory effect of p38α blockade on several β-catenin-responsive genes (i.e. c-Myc, cyclin D1/2, survivin, and others). This functional interaction was further characterized by chromatin immunoprecipitation experiments, which demonstrated that p38α is a chromatin-associated β-catenin kinase required for the transcriptional induction of several Wnt target genes, including c-Myc. Additionally, we demonstrated that p38α, like ERK, stabilizes c-Myc protein levels by preventing its ubiquitination. The finding that the phenotypes arising after APC loss in the intestine are fully dependent on c-Myc target gene expression suggests that c-Myc inhibition may be a good target for chemoprevention in CRC. These considerations underline the relevance of molecular profiling and preclinical investigation in order to achieve more efficient and accurate therapies. Indeed, our study identifies p38α as a promising therapeutic target acting directly on c-Myc and CRC-SCs, which are thought to be responsible for tumor proliferation, metastatic dissemination, and chemoresistance
The MAPK/C-Myc Axis in CRC: new pathogenic mechanisms and therapeutic approaches
No full textIntroduction
c-Myc plays a central role in cellular proliferation, differentiation, and apoptosis. Therefore its deregulation represents a powerful trigger of tumorigenesis, particularly in colorectal cancer (CRC). It has been shown that the MEK/ERK pathway phosphorylates c-Myc on serine 62, which stabilizes c-Myc by preventing ubiquitin/proteasomal degradation. We recently reported that MEK/ERK inhibition is counteracted by over-activation of p38α MAPK. Here, we identified cellular mechanisms that lead to c-Myc deregulation, which is a crucial issue for improving CRC treatment and survival.
Materials and Methods
The cross-talk between p38α and ERK was assessed in CRC cell lines and in APCMin/+ mice, a murine model of familial adenomatous polyposis. To this aim, animals were treated with the p38α inhibitor 4-(4-Fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)-1H-imidazole (SB202190®) alone or in combination with the MEK1 inhibitor N-[(2R)-2,3-Dihydroxypropoxy]-3,4-difluoro-2-[(2-fluoro-4-iodophenyl)amino]-benzamide (PD0325901®). In order to evaluate the role of p38α and ERK in c-Myc regulation, we used pharmacological inhibitors of these two kinases alone or in combination with inhibitors of the transcriptional mechanism, translational process and proteasome in CRC cell lines. Moreover, the function of p38α and ERK in Myc stabilization was assessed by genetic ablation.
Results and Discussion
Here we show that concomitant inhibition of the p38α and MEK/ERK pathways significantly increases the survival of APCMin/+ mice in which tumorigenesis is driven by c-Myc deregulation.
Genetic ablation of p38α and ERK revealed that these two MAPKs do not regulate c-Myc expression, nor do they affect c-Myc protein translational process.
We found that p38α and ERK collaborate in c-Myc stabilization by inhibiting its proteasomal degradation in CRC cell lines. These results were also confirmed by using the p38α and ERK pharmacological inhibitors LY2228820 (Ralimetinib®) and GSK1120212 (Mekinist®), respectively, which are currently in clinical trials for inflammatory diseases and cancer.
Conclusion
Since c-MYC supports the processes required for normal growth and homeostasis, its ablation is less attractive than modulation of its expression or function. Our results confirmed the essential role of the MAPK/c-Myc axis in intestinal tumorigenesis regulation, suggesting MAPK manipulation as a potential therapeutic approach to counteract c-Myc dependent carcinogenesis
A fresh look at the nested soft-collinear subtraction scheme: NNLO QCD corrections to N-gluon final states in q q ¯ annihilation
No full textAbstract We describe how the nested soft-collinear subtraction scheme [1] can be used to compute the next-to-next-to-leading order (NNLO) QCD corrections to the production of an arbitrary number of gluonic jets in hadron collisions. We show that the infrared subtraction terms can be combined into recurring structures that in many cases are simple iterations of those terms known from next-to-leading order. The way that these recurring structures are identified and computed is fairly general, and can be applied to any partonic process. As an example, we explicitly demonstrate the cancellation of all singularities in the fully-differential cross section for the q q ¯ → X + Ng process at NNLO in QCD. The finite remainder of the NNLO QCD contribution, which arises upon cancellation of all ϵ-poles, is expressed via relatively simple formulas, which can be implemented in a numerical code in a straightforward way. Our approach can be extended to describe arbitrary processes at NNLO in QCD; the largest remaining challenge at this point is the combinatorics of quark and gluon collinear limits
Casein phosphopeptides influence calcium uptake by cultured human intestinal HT-29 tumor cells
No full textWe investigated the direct effects of casein phosphopeptides (CPP), which are formed by the proteolytic degradation of - and ß-caseins, on calcium uptake by human HT-29 intestinal tumor cells, which undergo an enterocytically oriented differentiation in culture. A commercial preparation containing a mixture of purified CPP and an individual CPP of 25 amino acids, both containing the characteristic Ca2+ binding motif, ser(P)-ser(P)-ser(P)-glu-glu, were employed. The study was performed at the single-cell level and on a cell population and measured the changes in cytosolic calcium concentration before and after CPP addition. In the presence of 2 mmol/L extracellular calcium, both CPP preparations induced a transient rise of free intracellular calcium ions, which did not influence ATP-induced release of calcium from intracellular stores, and which disappeared completely in the absence of extracellular calcium. Pretreatment of these cells with thapsigargin, which completely empties the intracellular calcium stores, did not abolish the cell responses to CPP. Repetitive stimulation of HT-29 cells with CPP always elicited a transient calcium rise, suggesting a lack of desensitization. The CPP-stimulated cytosolic calcium rise was dependent on CPP dose, in a seemingly nonsaturating mode, and on cell numbers. All of this is consistent with the hypothesis that CPP do not influence membrane-bound receptors or ion channels, but may act as calcium ionophores or calcium carriers across the membrane. The reported findings provide a new basis on which to assess the possibility that CPP enhance calcium absorption and bioavailability in animal
On the design of linear virtual sensors for low cost vehicle stability control
No full textThe design of linear direct virtual sensors (DVS) to estimate yaw rate for vehicle stability control systems is investigated. The obtained DVS is stable and it can be used in a large range of operating conditions. It is shown how the use of closed-loop collected data and a suitable choice of the measured variables in sensor design improves the estimation accuracy. The effectiveness of the proposed DVS design is demonstrated by its employment in an existing yaw rate feedback loop, based on an Active Front Steering actuator and designed using Internal Model Control techniques. Robust stability is guaranteed in the presence of model uncertainty and of the DVS. In particular, the presented study shows that the DVS technology can be conveniently taken into account to replace physical sensors to obtain low cost stability control solutions for application on A and B segment cars. © 2008 IEEE
Chasing the Foxo3: Insights into its new mitochondrial lair in colorectal cancer landscape
No full textColorectal cancer (CRC) poses a formidable challenge in terms of molecular heterogeneity, as it involves a variety of cancer-related pathways and molecular changes unique to an individual’s tumor. On the other hand, recent advances in DNA sequencing technologies provide an unprecedented capacity to comprehensively identify the genetic alterations resulting in tumorigenesis, raising the hope that new therapeutic approaches based on molecularly targeted drugs may prevent the occurrence of chemoresistance. Regulation of the transcription factor FOXO3a in response to extracellular cues plays a fundamental role in cellular homeostasis, being part of the molecular machinery that drives cells towards survival or death. Indeed, FOXO3a is controlled by a range of external stimuli, which not only influence its transcriptional activity, but also affect its subcellular localization. These regulation mechanisms are mediated by cancer-related signaling pathways that eventually drive changes in FOXO3a post-translational modifications (e.g., phosphorylation). Recent results showed that FOXO3a is imported into the mitochondria in tumor cells and tissues subjected to metabolic stress and cancer therapeutics, where it induces expression of the mitochondrial genome to support mitochondrial metabolism and cell survival. The current review discusses the potential clinical relevance of multidrug therapies that drive cancer cell fate by regulating critical pathways converging on FOXO3a
A study on the use of virtual sensors in vehicle control
No full textThe design of linear virtual sensors to estimate yaw rate for vehicle stability control systems is investigated. Standard model-based virtual sensor design techniques are compared to novel direct virtual sensor (DVS) design methodologies. The obtained DVS is stable and it can be used in a large range of operating conditions. It is shown how the use of virtual sensors derived directly from data and a suitable choice of the measured variables in sensor design improves the estimation and control accuracy. The effectiveness of the proposed DVS design is demonstrated by its employment in an existing yaw rate feedback loop, based on an Active Front Steering actuator and designed using Internal Model Control techniques. Robust stability is guaranteed in the presence of model uncertainty and of the DVS. In particular, the presented study shows that the DVS technology can be conveniently taken into account to replace physical sensors to obtain low cost stability control solutions for application on A and B segment cars. © 2008 IEEE
Vehicle stability control using direct virtual sensors
No full textThe paper investigates the use of a direct virtual sensor (DVS) to replace a physical sensor in a vehicle stability control system. A yaw control system is considered and the proposed solution can be particularly useful when a fault of the yaw rate physical sensor occurs. A DVS is a stable linear filter derived directly from input-output data, collected in a preliminary experiment. In this work, it is shown that, by using data collected in a closed-loop fashion, better DVS accuracy can be obtained with a reduced number of measured variables. Moreover, the robust stability of the closed-loop system employing a DVS is studied. The effectiveness of the presented results is shown through numerical simulations of harsh manoeuvres, performed using a detailed model of a vehicle equipped with an active front steering device. © 2012 Copyright Taylor and Francis Group, LLC
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