Interfacial engineered RDX/TATB energetic co-particles for enhanced safety performance and thermal stability.

1,3,5-Trinitro-1,3,5-triazinane (RDX) has attracted considerable attention in energy-related fields. However, the safety performance of RDX needs to be improved in terms of various external stimuli. Herein, such issues of RDX could be well balanced through hydrothermal assembly with the assistance of insensitive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) in a low content of 10 wt% (named RT co-particles). The TATB spread outside and were embedded inside of the resultant RT co-particles, which were examined via X-ray computed tomography and a three-dimensional laser scanning confocal microscope. As a result, the impact safety performance of RT co-particles could be drastically enhanced to 17.5 J by the TATB lubricant effect, demonstrating over twice the value of that of raw RDX (6 J) and mixtures (7 J). Moreover, an interfacial reconstruction between RDX and TATB was witnessed due to the strong interfacial interaction, as examined by theoretical simulation. Inspired by this, a delayed exothermic decomposition temperature of RT co-particles (244.4 °C) has been achieved when compared with that of RDX (241.4 °C). As demonstrated, an energetic co-particle strategy may provide an effective pathway toward remarkably improved mechanical and thermal safety performance, shedding light on other energetic materials.

Porous MoS2 nanosheets for the fast decomposition of energetic compounds.

The energy release performance of energetic compounds like 3-nitro-1,2,4-trizole-5-one (NTO) and 5,5'-bistetrazole-1,1'-diolate (TKX-50) are indispensable in propellent formulations. However, thermal decomposition behavior is impeded by unfavorable catalysts. Presently, ultrathin porous MoS2 nanosheets (pMoS2) are considered as high-performance catalysts for NTO and TKX-50 decomposition. The pMoS2 in 5 wt% content could decrease the decomposition temperature of NTO and TKX-50 by 13.5 °C and 37.1 °C, respectively. Furthermore, the exothermic heat-release for pMoS2@NTO and pMoS2@TKX-50 were increased almost by a factor of two. The porous structure combined with large specific area of pMoS2 could mostly trigger the catalytic effect towards energetic compound decomposition. Additionally, the as-obtained MoS2 endowed advances in safety performance of NTO and TKX-50, with remarkably reduced impact and friction sensitivity. The as-proposed strategy may stimulate a different perspective towards the fast decomposition of energetic materials in propellants.

Application of Artificial Intelligence Modeling Technology Based on Fluid Biopsy to Diagnose Alzheimer's Disease.

Background: There are no obvious clinical signs and symptoms in the early stages of Alzheimer's disease (AD), and most patients usually have mild cognitive impairment (MCI) before diagnosis. Therefore, early diagnosis of AD is very critical. This paper mainly discusses the blood biomarkers of AD patients and uses machine learning methods to study the changes of blood transcriptome during the development of AD and to search for potential blood biomarkers for AD. Methods: Individualized blood mRNA expression data of 711 patients were downloaded from the GEO database, including the control group (CON) (238 patients), MCI (189 patients), and AD (284 patients). Firstly, we analyzed the subcellular localization, protein types and enrichment pathways of the differentially expressed mRNAs in each group, and established an artificial intelligence individualized diagnostic model. Furthermore, the XCell tool was used to analyze the blood mRNA expression data and obtain blood cell composition and quantitative data. Ratio characteristics were established for mRNA and XCell data. Feature engineering operations such as collinearity and importance analysis were performed on all features to obtain the best feature solicitation. Finally, four machine learning algorithms, including linear support vector machine (SVM), Adaboost, random forest and artificial neural network, were used to model the optimal feature combinations and evaluate their classification performance in the test set. Results: Through feature engineering screening, the best feature collection was obtained. Moreover, the artificial intelligence individualized diagnosis model established based on this method achieved a classification accuracy of 91.59% in the test set. The area under curve (AUC) of CON, MCI, and AD were 0.9746, 0.9536, and 0.9807, respectively. Conclusion: The results of cell homeostasis analysis suggested that the homeostasis of Natural killer T cell (NKT) might be related to AD, and the homeostasis of Granulocyte macrophage progenitor (GMP) might be one of the reasons for AD.

Diagnostic AI Modeling and Pseudo Time Series Profiling of AD and PD Based on Individualized Serum Proteome Data.

Background: Parkinson's disease (PD), Alzheimer's disease (AD) are common neurodegenerative disease, while mild cognitive impairment (MCI) may be happened in the early stage of AD or PD. Blood biomarkers are considered to be less invasive, less cost and more convenient, and there is tremendous potential for the diagnosis and prediction of neurodegenerative diseases. As a recently mentioned field, artificial intelligence (AI) is often applied in biology and shows excellent results. In this article, we use AI to model PD, AD, MCI data and analyze the possible connections between them. Method: Human blood protein microarray profiles including 156 CT, 50 MCI, 132 PD, 50 AD samples are collected from Gene Expression Omnibus (GEO). First, we used bioinformatics methods and feature engineering in machine learning to screen important features, constructed artificial neural network (ANN) classifier models based on these features to distinguish samples, and evaluated the model's performance with classification accuracy and Area Under Curve (AUC). Second, we used Ingenuity Pathway Analysis (IPA) methods to analyse the pathways and functions in early stage and late stage samples of different diseases, and potential targets for drug intervention by predicting upstream regulators. Result: We used different classifier to construct the model and finally found that ANN model would outperform the traditional machine learning model. In summary, three different classifiers were constructed to be used in different application scenarios, First, we incorporated 6 indicators, including EPHA2, MRPL19, SGK2, to build a diagnostic model for AD with a test set accuracy of up to 98.07%. Secondly, incorporated 15 indicators such as ERO1LB, FAM73B, IL1RN to build a diagnostic model for PD, with a test set accuracy of 97.05%. Then, 15 indicators such as XG, FGFR3 and CDC37 were incorporated to establish a four-category diagnostic model for both AD and PD, with a test set accuracy of 98.71%. All classifier models have an auc value greater than 0.95. Then, we verified that the constructed feature engineering filtered out fewer important features but contained more information, which helped to build a better model. In addition, by classifying the disease types more carefully into early and late stages of AD, MCI, and PD, respectively, we found that early PD may occur earlier than early MCI. Finally, there are 24 proteins that are both differentially expressed proteins and upstream regulators in the disease group versus the normal group, and these proteins may serve as potential therapeutic targets and targets for subsequent studies. Conclusion: The feature engineering we build allows better extraction of information while reducing the number of features, which may help in subsequent applications. Building a classifier based on blood protein profiles using deep learning methods can achieve better classification performance, and it can help us to diagnose the disease early. Overall, it is important for us to study neurodegenerative diseases from both diagnostic and interventional aspects.

Targeting cyclin-dependent kinase 9 by a novel inhibitor enhances radiosensitization and identifies Axl as a novel downstream target in esophageal adenocarcinoma.

Cyclin-dependent kinase 9 (CDK9) transcriptionally regulates several proteins and cellular pathways central to radiation induced tissue injury. We investigated a role of BAY1143572, a new highly specific CDK9 inhibitor, as a sensitizer to radiation in esophageal adenocarcinoma. In vitro synergy between the CDK9 inhibitor and radiation was evaluated by clonogenic assay. In vivo synergy between the CDK9 inhibitor and radiation was assessed in multiple xenograft models including a patient's tumor derived xenograft (PDX). Reverse phase protein array (RPPA), western blotting, immunohistochemistry, and qPCR were utilized to identify and validate targets of the CDK9 inhibitor. The CDK9 inhibitor plus radiation significantly reduced growth of FLO-1, SKGT4, OE33, and radiation resistant OE33R xenografts and PDXs as compared to the cohorts treated with either single agent CDK9 inhibitor or radiation alone. RPPA identified Axl as a candidate target of CDK9 inhibition. Western blot and qPCR demonstrated reduced Axl mRNA (p = 0.02) and protein levels after treatment with CDK9 inhibitor with or without radiation in FLO-1 and SKGT4 cells. Axl protein expression in FLO-1 xenografts treated with combination of CDK9 inhibitor and radiation was significantly lower than the xenografts treated with radiation alone (p = 0.003). Clonogenic assay performed after overexpression of Axl in FLO-1 and SKGT4 cells enhanced radiosensitization by the CDK9 inhibitor, suggesting dependency of radiosensitization effects of the CDK9 inhibitor on Axl. In conclusion, these findings indicate that targeting CDK9 by BAY1143572 significantly enhances the effects of radiation and Axl is a novel downstream target of CDK9 in esophageal adenocarcinoma.

Enhanced Interfacial and Mechanical Properties of PBX Composites via Surface Modification on Energetic Crystals.

The mechanical properties of composites are highly dependent on the interfacial interaction. In the present work, inspired by marine mussel, the adhesion between energetic crystals of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) and polymer binders was improved. Three types of linear polymeric agents of glycidyl azide polymer (GAP), polyethylene glycol (PEG), and polytetramethylene ether glycol (PTMEG) were grafted onto TATB particles bridged through polydopamine (PDA) films. SEM images showed that 5% grafting contents could evidently form roughness shells on the surface. With a reinforcement at the interface produced by grafting shells, the mechanical properties of polymer-bonded explosives (PBXs) exhibited outstanding mechanical performance, especially for the PTMEG-grafting sample. Examined by the contact-angle test, the PTMEG-grafting sample possessed a value of polar component similar to that of fluoropolymer, leading to an excellent wettability of the two phases. Additionally, different contents of PTMEG were grafted to reveal that the mechanical properties could be improved even with content as little as 0.5 wt.% PTMEG. These results might highlight a correlation between interfacial interaction and macroscopic properties for mechanically energetic composites, while providing a versatile route of grafting on highly loaded composites.

Core@Double-Shell Structured Energetic Composites with Reduced Sensitivity and Enhanced Mechanical Properties.

A novel core@double-shell (CDS) 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) based energetic composite was constructed with an inner nano-1,3,5-triamino-2,4,6-trinitrobenzene (nano-TATB) shell and outer polydopamine (PDA) shell fabricated via a facile ultrasonic method and a simple immersion method, respectively. The inner nano-TATB shell was chosen to reduce the sensitivity of HMX while maintaining explosion performance; the outer PDA shell was adopted to enhance the interfacial interaction between explosive crystals and polymer binder. The uniform PDA coating resulted in the increased ß-δ phase transition temperature of HMX from 197.0 to 212.8 °C. Because of the perfect and compact nano-TATB coating on the surface of the HMX particles, the impact sensitivity  was significantly decreased for the HMX@TATB@PDA particles (10 J), in comparison with the physical mixture with an equivalent composition (5 J). Polymer-bonded explosives (PBXs) based on CDS structured particles were designed and characterized in comparison with their core@single-shell (CSS) counterparts or physical mixtures. Due to the strong chemical and physical interfacial interaction, PBXs based on CDS structured particles displayed improved mechanical strength and roughness, storage modulus, as well as creep resistance.

Hsp90 Inhibitor Ganetespib Sensitizes Non-Small Cell Lung Cancer to Radiation but Has Variable Effects with Chemoradiation.

PURPOSE: HSP90 inhibition is well known to sensitize cancer cells to radiation. However, it is currently unknown whether additional radiosensitization could occur in the more clinically relevant setting of chemoradiation (CRT). We used the potent HSP90 inhibitor ganetespib to determine whether it can enhance CRT effects in NSCLC. EXPERIMENTAL DESIGN: We first performed in vitro experiments in various NSCLC cell lines combining radiation with or without ganetespib. Some of these experiments included clonogenic survival assay, DNA damage repair, and cell-cycle analysis, and reverse-phase protein array. We then determined whether chemotherapy affected ganetespib radiosensitization by adding carboplatin-paclitaxel to some of the in vitro and in vivo xenograft experiments. RESULTS: Ganetespib significantly reduced radiation clonogenic survival in a number of lung cancer cell lines, and attenuated DNA damage repair with irradiation. Radiation caused G2-M arrest that was greatly accentuated by ganetespib. Ganetespib with radiation also dose-dependently upregulated p21 and downregulated pRb levels that were not apparent with either drug or radiation alone. However, when carboplatin-paclitaxel was added, ganetespib was only able to radiosensitize some cell lines but not others. This variable in vitro CRT effect was confirmed in vivo using xenograft models. CONCLUSIONS: Ganetespib was able to potently sensitize a number of NSCLC cell lines to radiation but has variable effects when added to platinum-based doublet CRT. For optimal clinical translation, our data emphasize the importance of preclinical testing of drugs in the context of clinically relevant therapy combinations. Clin Cancer Res; 22(23); 5876-86. ©2016 AACR.

Coronary microvascular pericytes are the cellular target of sunitinib malate-induced cardiotoxicity.

Sunitinib malate is a multitargeted receptor tyrosine kinase inhibitor used in the treatment of human malignancies. A substantial number of sunitinib-treated patients develop cardiac dysfunction, but the mechanism of sunitinib-induced cardiotoxicity is poorly understood. We show that mice treated with sunitinib develop cardiac and coronary microvascular dysfunction and exhibit an impaired cardiac response to stress. The physiological changes caused by treatment with sunitinib are accompanied by a substantial depletion of coronary microvascular pericytes. Pericytes are a cell type that is dependent on intact platelet-derived growth factor receptor (PDGFR) signaling but whose role in the heart is poorly defined. Sunitinib-induced pericyte depletion and coronary microvascular dysfunction are recapitulated by CP-673451, a structurally distinct PDGFR inhibitor, confirming the role of PDGFR in pericyte survival. Thalidomide, an anticancer agent that is known to exert beneficial effects on pericyte survival and function, prevents sunitinib-induced pericyte cell death in vitro and prevents sunitinib-induced cardiotoxicity in vivo in a mouse model. Our findings suggest that pericytes are the primary cellular target of sunitinib-induced cardiotoxicity and reveal the pericyte as a cell type of concern in the regulation of coronary microvascular function. Furthermore, our data provide preliminary evidence that thalidomide may prevent cardiotoxicity in sunitinib-treated cancer patients.

Endogenous R&D spillover and location choice in a mixed oligopoly.

We consider a three-stage game where a public firm and a private firm choose R&D, location, and price, under the assumption that R&D spillovers rely on their locations. We show that, in equilibrium, whether the public firm engages in innovation more aggressively than the private firm depends on the degree of spillovers. Moreover, firms' equilibrium locations exhibit neither maximal nor minimal differentiation. Finally, privatization could reduce social welfare because it may generate inefficient location and insufficient R&D investment. This suggests that a mixed duopoly could be socially preferable to a private duopoly in the presence of endogenous R&D spillovers.

Mesenchymal stem cells regulate blood-brain barrier integrity through TIMP3 release after traumatic brain injury.

Mesenchymal stem cells (MSCs) may be useful for treating a variety of disease states associated with vascular instability including traumatic brain injury (TBI). A soluble factor, tissue inhibitor of matrix metalloproteinase-3 (TIMP3), produced by MSCs is shown to recapitulate the beneficial effects of MSCs on endothelial function and to ameliorate the effects of a compromised blood-brain barrier (BBB) due to TBI. Intravenous administration of recombinant TIMP3 inhibited BBB permeability caused by TBI, whereas attenuation of TIMP3 expression in intravenously administered MSCs blocked the beneficial effects of the MSCs on BBB permeability and stability. MSCs increased circulating concentrations of soluble TIMP3, which blocked vascular endothelial growth factor-A-induced breakdown of endothelial cell adherens junctions in vitro and in vivo. These findings elucidate a potential molecular mechanism for the beneficial effects of MSCs on the BBB after TBI and demonstrate a role for TIMP3 in the regulation of BBB integrity.

MicroRNA-9 is an activation-induced regulator of PDGFR-beta expression in cardiomyocytes.

The platelet derived growth factor receptor (PDGFR) is an important target for novel anti-cancer therapeutics, but agents targeting PDGFR have been associated with cardiotoxicity. Cardiomyocyte PDGFR-ß signaling in pressure-overloaded hearts induces compensatory angiogenesis via a paracrine-signaling cascade. Tight regulation of receptor tyrosine kinases in response to ligand stimulation is a critical part of any such cascade. The objective of the present study was to characterize the early and late regulation of PDGFR-ß following ligand stimulation and define a potential role for microRNAs (miRNAs) predicted to interact with the 3'UTR of PDGFR-ß in feedback regulation. Using two in-vitro model systems (U87 glioblastoma cells and neonatal cardiomyocytes), we observed that in response to stimulation with PDGF-BB, levels of PDGFR-ß declined beginning at one hour, persisting for 48 h. PDGFR-ß mRNA levels declined beginning at 6h after receptor activation. Early, but not late activation-induced receptor downregulation was proteasome dependent. Levels of miRNA-9 (miR-9) were significantly increased in U87 cells and cardiomyocytes beginning 6h after addition of ligand. In response to pressure overload, miR-9 levels were significantly reduced in the hearts of cardiac-specific PDGFR-ß knockout mice. Luciferase reporter assays demonstrate that miR-9 directly interacts with its predicted seed in the 3'UTR of PDGFR-ß. Increasing miR-9 levels reduces levels of PDGFR-ß, resulting in a reduction in the paracrine angiogenic capacity of cardiomyocytes, consistent with the established function of cardiomyocyte PDGFR-ß. Importantly, increase of anti-miR-9 in cardiomyocytes attenuates ligand-induced PDGFR-ß downregulation. In conclusion, we have identified miR-9 as an activation-induced regulator of PDGFR-ß expression in cardiomyocytes that is part of a negative feedback loop which serves to modulate PDGFR-ß expression upon ligand-stimulation through direct interaction with the 3'UTR of PDFGR-ß. This article is part of a Special Issue entitled 'Possible Editorial'.

Cardiomyocyte PDGFR-beta signaling is an essential component of the mouse cardiac response to load-induced stress.

PDGFR is an important target for novel anticancer therapeutics because it is overexpressed in a wide variety of malignancies. Recently, however, several anticancer drugs that inhibit PDGFR signaling have been associated with clinical heart failure. Understanding this effect of PDGFR inhibitors has been difficult because the role of PDGFR signaling in the heart remains largely unexplored. As described herein, we have found that PDGFR-beta expression and activation increase dramatically in the hearts of mice exposed to load-induced cardiac stress. In mice in which Pdgfrb was knocked out in the heart in development or in adulthood, exposure to load-induced stress resulted in cardiac dysfunction and heart failure. Mechanistically, we showed that cardiomyocyte PDGFR-beta signaling plays a vital role in stress-induced cardiac angiogenesis. Specifically, we demonstrated that cardiomyocyte PDGFR-beta was an essential upstream regulator of the stress-induced paracrine angiogenic capacity (the angiogenic potential) of cardiomyocytes. These results demonstrate that cardiomyocyte PDGFR-beta is a regulator of the compensatory cardiac response to pressure overload-induced stress. Furthermore, our findings may provide insights into the mechanism of cardiotoxicity due to anticancer PDGFR inhibitors.

Rare incidence of congestive heart failure in gastrointestinal stromal tumor and other sarcoma patients receiving imatinib mesylate.

BACKGROUND: The authors sought to determine the incidence and severity of cardiovascular toxicity caused by imatinib mesylate in gastrointestinal stromal tumor (GIST) and other sarcoma patients, and to explore cardiotoxicity caused by imatinib mesylate using cell culture and in vitro models. METHODS: To determine the incidence and significance of serious cardiac adverse events in GIST and other sarcoma patients receiving imatinib mesylate, the authors performed a retrospective analysis of 219 consecutive patients treated with imatinib mesylate. In vitro studies of imatinib mesylate on cultured cardiomyocytes and biochemical studies of cardiac lysates from mice treated with imatinib mesylate were performed to define the potential cardiotoxic effects of imatinib mesylate. RESULTS: Grade 3 or 4 potentially cardiotoxic adverse events (mostly edema or effusions) occurred in 8.2% of patients, were manageable with medical therapy, and infrequently required dose reduction or discontinuation of imatinib mesylate. Arrhythmias, acute coronary syndromes, or heart failure were uncommon, occurring in <1% of treated patients. However, administration of imatinib in a mouse model system resulted in inhibition of activation of protein kinases that are known to be important in the cardiac stress response. CONCLUSIONS: The authors concluded that imatinib is an uncommon cause of cardiotoxicity, and that the cardiovascular adverse events that occur are manageable when recognized and treated. Nevertheless, our preclinical findings suggest that imatinib remains a potential cardiotoxin. Furthermore, the cardiac consequences of long-term imatinib therapy remain unknown. We therefore recommend treatment of risk factors for cardiovascular disease in imatinib-treated patients in accord with the American Heart Association guidelines for the prevention and treatment of heart failure.

Cytoskeletal signaling by way of alpha-actinin-1 mediates ERK1/2 activation by repetitive deformation in human Caco2 intestinal epithelial cells.

BACKGROUND: Repetitive deformation stimulates proliferation in human Caco2 intestinal epithelial cells by way of an ERK1/2-dependent pathway. We examined the effects of cytoskeletal perturbation on deformation-induced signaling in Caco2 cells. METHODS: The Caco2 cell cytoskeleton was disrupted with either cytochalasin D, phalloidin, colchicine, or paclitaxel. Levels of alpha-actinin-1 and -4 and paxillin were reduced by specific small interfering RNA. Cells on collagen I-precoated membranes were subjected to 10% repetitive deformation at 10 cycles/min. After 1 hour, cells were lysed for Western blot analysis. RESULTS: Strain-activated ERK1/2, focal adhesion kinase, and Src phosphorylation in dimethyl sulfoxide- and/or nontargeting small interfering RNA-treated control cell populations. Cytochalasin D and paclitaxel, but not phalloidin and colchicine, blocked ERK1/2 phosphorylation. A decrease in alpha-actinin-1, but not in alpha-actinin-4 or paxillin, inhibited ERK1/2 and focal adhesion kinase phosphorylation, whereas Src activation appears to be independent of these effects. CONCLUSIONS: The intestinal epithelial cell cytoskeleton may transduce mechanical signals by way of alpha-actinin-1 into the focal adhesion complex, culminating in ERK1/2 activation and proliferation.

The motogenic effects of cyclic mechanical strain on intestinal epithelial monolayer wound closure are matrix dependent.

BACKGROUND & AIMS: Complex deformation during normal digestion due to peristalsis or villous motility may be trophic for the intestinal mucosa. Because tissue fibronectin is increased in inflammatory states that may accompany mucosal injury, we evaluated the effects of cyclic mechanical strain and fibronectin on intestinal epithelial monolayer wound closure in Caco-2 and IEC-6 intestinal epithelial cells. METHODS: Wounds created in intestinal epithelial monolayers were subjected to cyclic deformation. Wound closure was assessed by morphometry using microscopic imaging. Cell signals were assessed by Western blot and confocal microscopy. RESULTS: Mechanical strain stimulated wound closure on fibronectin but inhibited closure on collagen in Caco-2 and IEC-6 cells. The effect was independent of proliferation or cell spreading. Myosin light chain (MLC) and extracellular signal-regulated kinase (ERK) were phosphorylated in response to strain in confluent monolayers on both collagen and fibronectin. Blocking MLC or ERK phosphorylation inhibited the motogenic effect of strain on fibronectin. Although phosphorylated MLC was redistributed to the leading edge of migrating cells following 6 hours of strain on collagen and fibronectin, phosphorylated ERK was redistributed to the lamellipodial edge only on fibronectin. CONCLUSIONS: Strain promotes intestinal epithelial wound closure by a pathway requiring ERK and MLC kinase. Fibronectin-dependent ERK redistribution in response to strain in confluent migrating cells may explain the matrix dependence of the motogenic effect. Repetitive deformation stimulates intestinal epithelial proliferation on a collagen substrate, but not fibronectin. Deformation may exert matrix-dependent effects on intestinal epithelial cells, promoting epithelial restitution in fibronectin-rich tissue and proliferation in fibronectin-poor mucosa.

Focal adhesion kinase protein levels in gut epithelial motility.

Mucosal healing requires migration and proliferation. Most studies of focal adhesion kinase (FAK), a protein that regulates motility, proliferation, and apoptosis, have focused on rapid phosphorylation. We reported lower FAK protein levels in motile Caco-2 colon cancer cells and postulated that this reduction in FAK available for activation might impact cell migration and mucosal healing. Therefore, total and active FAK (FAK(397)) immunoreactivity was assessed at the migrating fronts of human Caco-2 and rat IEC-6 intestinal epithelial cells. Caco-2 and IEC-6 motility, quantitated as migration into linear or circular wounds, was examined following FAK protein inhibition by small interfering RNA (siRNA). FAK protein stability and mRNA expression were ascertained by cycloheximide decay, RT-PCR, and in situ hybridization in static and migrating Caco-2 cells. Cells at the migrating front of Caco-2 and IEC-6 monolayers exhibited lower immunostaining for both total and activated FAK than cells immediately behind the front. Western blot analysis also demonstrated diminished FAK protein levels in motile cells by >/=30% in both the differential density seeding and multiple scrape models. siRNA FAK protein inhibition enhanced motility in both the linear scrape (20% in Caco-2) and circular wound (16% in Caco-2 and 19% in IEC-6 cells) models. FAK protein degradation did not differ in motile and static Caco-2 cells and was unaffected by FAK(397) phosphorylation, but FAK mRNA was lower in migrating Caco-2 cells. Thus FAK protein abundance appears regulated at the mRNA level during gut epithelial cell motility and may influence epithelial cell migration coordinately with signals that modify FAK phosphorylation.

Human mesenchymal stem cells exert potent antitumorigenic effects in a model of Kaposi's sarcoma.

Emerging evidence suggests that both human stem cells and mature stromal cells can play an important role in the development and growth of human malignancies. In contrast to these tumor-promoting properties, we observed that in an in vivo model of Kaposi's sarcoma (KS), intravenously (i.v.) injected human mesenchymal stem cells (MSCs) home to sites of tumorigenesis and potently inhibit tumor growth. We further show that human MSCs can inhibit the in vitro activation of the Akt protein kinase within some but not all tumor and primary cell lines. The inhibition of Akt activity requires the MSCs to make direct cell-cell contact and can be inhibited by a neutralizing antibody against E-cadherin. We further demonstrate that in vivo, Akt activation within KS cells is potently down-regulated in areas adjacent to MSC infiltration. Finally, the in vivo tumor-suppressive effects of MSCs correlates with their ability to inhibit target cell Akt activity, and KS tumors engineered to express a constitutively activated Akt construct are no longer sensitive to i.v. MSC administration. These results suggest that in contrast to other stem cells or normal stromal cells, MSCs possess intrinsic antineoplastic properties and that this stem cell population might be of particular utility for treating those human malignancies characterized by dysregulated Akt.

Fibronectin blocks p38 and jnk activation by cyclic strain in Caco-2 cells.

Diverse repetitive forces deform the intestinal epithelium and basement membrane. Such repetitive deformation induces intestinal epithelial proliferation, differentiation, and intracellular signaling. Although at least some deformation-induced signals probably involve integrins, the matrix-dependence of these signals is poorly understood. We compared rapid strain activation of p38 and jnk in human Caco-2 intestinal epithelial cells cultured on collagen I, collagen IV, laminin, and tissue fibronectin. These signals were inhibited in cells on a fibronectin substrate, but activated by strain on collagens and laminin. Furthermore, adding 300 microg/ml plasma fibronectin (approximately the concentration found in plasma) to the culture medium inhibited strain activation of p38 and jnk in cells cultured on collagen. Since tissue and plasma fibronectin levels vary in acute or chronic inflammatory or infectious conditions, these results suggest that tissue or plasma fibronectin may modulate the intestinal epithelial response to repetitive deformation.

Regulation of the intestinal epithelial response to cyclic strain by extracellular matrix proteins.

Repetitive mechanical deformation may stimulate intestinal epithelial proliferation. Because the extracellular matrix modulates static intestinal epithelial biology, we examined whether matrix proteins influence intestinal epithelial responses to deformation. Human Caco-2BBE cells and nontransformed human enterocytes (HIPEC) were subjected to 10% average cyclic strain at 10 cycles/min on flexible membranes precoated with matrix proteins without or with plasma fibronectin or functional anti-integrin antibodies in the medium. Strain stimulated proliferation, focal adhesion kinase, extracellular signal-regulated protein kinase (ERK), p38, and Jun N-terminal kinase similarly on collagen I or IV, and more weakly on laminin, but had no effect on fibronectin. MEK blockade (PD98059) prevented strain-stimulated proliferation on collagen but did not affect proliferation on fibronectin. Adding tissue fibronectin to a collagen substrate or plasma fibronectin to the media suppressed strain s mitogenic and signal effects, but not those of epidermal growth factor. Functional antibodies to the alpha5 or alpha(v) integrin subunit blocked strain's effects on Caco-2 proliferation and ERK activation, although ligation of the alpha2 or alpha6 subunit did not. Repetitive strain also stimulated, and fibronectin inhibited, human intestinal primary epithelial cell proliferation. Repetitive deformation stimulates transformed and nontransformed human intestinal epithelial proliferation in a matrix-dependent manner. Tissue or plasma fibronectin may regulate the intestinal epithelial response to strain via integrins containing alpha5 or alpha(v).