bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Science Study on the Stability of Various Catalyst Materials for DMFC
Authors: Schulze Mathias , Reissner Regine , Christenn Claudia
Published: May 2007

This contribution presents exemplary investigations by surface science methods for the investigation of electrodes and catalyst systems in fuel cells. The aim is to illustrate the information gain which is obtained with the combination of physical analysis even of complex system. Particularly, systems for DMFC application were selected. The examples range from commercially available catalysts and their electrodes to model systems with novel experimental composition. For platinum alloy catalysts on the anode side XPS analysis shows that the non-noble alloy metals are dissolved. On the cathode an agglomeration of the platinum can be observed by electron microscopies, whereby the agglomeration results in a loss of active surface area. The investigated RuSe catalysts are significantly changed due to electrochemical operation, whereby the non active species is dissolved. Investigations of model systems are presented that show that a core-shell catalyst structures help to stabilize non-noble components
Structurally Cross-Linked Composite Proton Exchange Membranes
Authors: Pern Fu-Jann (John) , Turner John A. , Dec Steve , Yan Yanfa , To Bobby , Lipfert Dana , Meng Fenqing , Herring Andrew M.
Published: May 2007

Composite proton exchange membranes (PEMs) with a thermally cross-linked polymer backbone for high-temperature fuel cell applications were fabricated by casting tetrahydrofuran solution mixtures of tetraethoxysilane, a functional silane, a proton conductor, a molecular cross-linker (MXL), and an ethylene-methylacrylate copolymer with glycidyl methacrylate groups (PMG). The proton conductors used were commercial Keggin-structured silicotungstic acid (H4SiW12O40-26H2O, W12- STA) and lacunary W10- and W11-STA. The 3D cross-linked membranes were dense with in-situ formed SiO2 nanoparticles and showed high thermal stability, high chemical resistance to the Fenton's reagent, and moderate mechanical strength and flexibility. The corresponding proton conductivity was affected by formulation, membrane quality, loading level of W12-STA, temperature, and relative humidity, and was in the 20- 25 mS/cm range at 80oC/100%RH with proton diffusion coefficients of 2.5-3.5 x 10-6 cm/s peaked in the ~90o-110oC range for PEMs having a loading level of W12-STA >150 wt% (ratio to the weight sum of PMG and MXL).
An Empirical Model for Proton Exchange Membrane Fuel Cell Diagnostics
Authors: Merida Walter
Published: May 2007

Individual cell voltage monitoring (CVM) has been the de facto technique to detect a general failure within a fuel cell stack. However, discerning between different types of failures is challenging because different failure modes can produce the same observed change in dc potential. This work discusses failure detection and isolation in proton exchange membrane fuel cells (PEMFCs). One specific approach based on electrochemical impedance spectroscopy (EIS) is used to illustrate these concepts. The relevant EIS measurements were made on fuel cell stack at different typical operating temperatures, covering the current density range 0.1 to 1.0 A cm-2, and the frequency range 0.1 to a few hundred kHz. The collected spectra were modelled with an equivalent circuit whose time constants corresponded to ideal and Warburg components. Despite the qualitative limitations of this model, the measurements can discern between two failure modes.
Pressure Drop in Micro Channel Flow with the Electrochemical Reactions in Fuel Cell
Authors: Cho Sona , Lee Pilhyong , Han Sangseok , Hwang Sangsoon
Published: May 2007

Narrow, long micro channels in flow plates of fuel cell are required for good reactant distribution, but also increase parasitic pumping power. Therefore, it is important to try to minimize the pressure drop in the flow channels. We investigated the pressure losses in micro channels of anodes and cathodes under cold flow conditions in straight, bend and serpentine channel designs. The results show that friction factors for cold flow could be used for the design of parallel and bend channels. However, cold flow conditions do not predict the pressure drop for serpentine channels. Compared with the other channels, serpentine channels had the lowest pressure drop under reaction conditions, but the highest, pressure drop under cold flow conditions. Under reaction conditions, part of the flow in the serpentine channels bypassed the gas diffusion layer. So the effect of bypass flow should be considered for the design of serpentine flow channels
The Effects of Contaminants of Fuel on the Direct Methanol Fuel Cell (DMFC) Performance
Authors: Yasuda Kazuhiro , Nakano Yoshihiko , Goto Yasuhiro
Published: May 2007

We chose metal ions and organic substances as contaminants in fuel in order to clarify influence of contaminants on the DMFC performance in life test. During the life test, the metal ions in the fuel accumulated in the electrolyte membrane and degraded the cell performance. The degradation was in proportion to the amount of metal ions in electrolyte. On the other hand, in the case of some kinds of organic substances degradations were observed. During the life test, the organic substance in the fuel might be oxidized in anode and that oxidized substance might have an adverse affect on the catalysis in the anode electrode.
Modular Testing and Simulation Environment for Analysis and Optimization of Fuel Cell Systems
Authors: Koenig Patrick , Ivers-Tiffee Ellen
Published: May 2007

Improvement of fuel cell systems with respect to reliability and efficiency is the main issue in preparing them for their commercialization. Stationary, automotive or portable systems are still at the development stage and a lot of tasks have to be solved as to increase the component and system efficiencies by facilitating the system construction or eliminating parasitic components. To accelerate the development and to determine the systems efficiencies as well as the inaccessible system values, effective standardized tests have to be established and linked with a flexible modeling and simulation environment. A modular model-aided system analysis and development environment is presented which has been evaluated and validated at the IWE. The tool has been applied to a complex prototype stationary PEMFC system, a commercial methanol based PEMFC auxiliary power unit and a fictive stationary SOFC system proving the tool flexibility, modularity and accuracy for a wide range of applications.
Effects of Oxide Thickness on Scale and Interface Stresses under Isothermal Cooling and Micro-Indentation for Ferritic Stainless Steel Interconnect
Authors: Sun Xin , Liu Wenning , Vetrano John , Yang Zhenguo Gary , Recknagle Kurtis P. , Khaleel Moe
Published: May 2007

Interconnects in solid oxide fuel cells (SOFCs) provide the electrical connection between the individual cells, as well as separate the anode fuel from the cathode air for each cell. In this paper, we study the thermal stresses in the oxide scale and at the oxide/substrate interface for Cr-Fe based interconnect (IC), e.g. Crofer 22 APU, during cooling. The ultimate goal is to predict the interconnect life under typical operating conditions and thermal cycles. In general, very high compressive in-plane stresses are predicted in the oxide layer during cooling. High shear stress is also predicted on the oxide scale/substrate interface. The predicted shear stress on the interface will be used to compare with the experimentally determined bond strength to predict delamination. Finite element analyses are also performed for indentation test: high shear stress is predicted on the oxide/substrate interface, and the interfacial crack growth is predicted to be mode II driven.
Concepts for Ultra-high Power Density Solid Oxide Fuel Cells
Authors: Virkar Anil , Williams Mark C. , Singhal Subhash
Published: May 2007

A parametric equation for describing polarization in solid oxide fuel cells (SOFC) is presented in terms of experimentally measurable parameters. The equation explicitly describes activation and concentration polarizations at the two electrodes, and the ohmic loss as a function of current density. Using the equation and known values of experimentally measured parameters, determined by in-cell and out-of-cell tests, various polarizations are estimated as functions of current density, and the maximum possible performance characteristics are assessed. The parameters used for the calculations of polarization curves include: (a) Charge transfer resistivity as a function of temperature and atmosphere measured using patterned electrodes deposited by micro photolithography. (b) Effective gas phase diffusivities measured using an electrochemical technique or from prior cell performance fitting. (c) Estimated ohmic loss using in-cell and out-of-cell measurements. Polarization curves are calculated for two different microstructures in the functional layers. Calculations are also made for various compositions of the fuel, which can be used to estimate performance as a function of fuel utilization, and various oxidant compositions. Then, using the model, prospects for ultra-high power density SOFC at intermediate temperatures (<800oC) are examined. The results show that even in thin electrolyte film, anode-supported cells, ohmic contribution can be substantial. The results also show that the electrode particle size has a substantial effect on activation polarization.
Development of Reinforced Matrix for Molten Carbonate Fuel Cells by Using Sintering Aids
Authors: Ham Hyung Chul , Yoon Sung Pil , Han Jonghee , Nam Suk Woo , Lim Tae-Hoon , Hong Senog-Ahn
Published: May 2007

In order to reinforce a matrix for molten carbonate fuel cell (MCFC), sintering additives having low melting points such as Al [660oC], B2O3 [450oC] and Al(OH)3 powders [320oC] have been included into conventional LiAlO2 green sheets by tape casting method. The mechanical strength was clearly increased by the addition of B2O3 into the LiAlO2 matrix. The enhancement of mechanical strength in the B2O3 -included matrix was mainly attributed to the Li2AlBO4 formation by the reaction between B2O3 and LiAlO2.
Experimental Study of Anode Gas Recycling on Efficiency of SOFC
Authors: Noponen Matti , Halinen Matias , Saarinen Jaakko , Kiviaho Jari
Published: May 2007

The effect of anode gas recycling on the efficiency of a solid oxide fuel cell has been studied with unit cell experiments. It has been found out that fuel utilization can be reduced down to 60 % without sacrificing the electrical efficiency. It has also been shown that the reformer used in the study could be treated as an equilibrium reactor also in the case where anode gas was recycled.
ISO Technical Specification for Hydrogen Fuel Quality: Status and Path Forward
Authors: Ohi James
Published: May 2007

Hydrogen fuel quality specifications must be quantified at the vehicle-station interface and must consider how the presence of small amounts of contaminants affect the performance and durability of fuel cells and balance of plant; material compatibility of on-board and stationary hydrogen storage systems; and the operation and maintenance of hydrogen production, purification, and delivery systems. Preliminary fuel quality guidelines based on available data and information have been prepared by ISO (1) and SAE (2). Before these guidelines can become international and national standards, respectively, a comprehensive, structured R&D and testing effort is needed to determine the effects, especially degradation mechanisms, of various contaminants on fuel cell electrodes and membranes. Implications of fuel quality on the complexity, performance, and durability of fuel cell systems and upstream infrastructure as well as on the cost of fuel must be understood so that critical trade-offs can be assessed.
Thermodynamic Properties of Hydrogen-Water Vapor and Air-Water Vapor Mixtures in Fuel Cells
Authors: Huang Peter H.
Published: May 2007

This paper provides calculated values of specific enthalpy, specific entropy and specific Gibbs energy associated with moist hydrogen and air. They cover the range of interest in humidity control and measurement methods for fuel cell applications from water vapor content of dew-point temperatures 60 {degree sign}C to 200 {degree sign}C with absolute pressures of 0.1 MPa, 0.5 MPa, 1 MPa and 2 MPa. Molar enthalpy, molar entropy and molar Gibbs free energy of moist hydrogen and air are expressed explicitly in terms of the associated water vapor density. The values of the molar quantities are the sum of three parts due to: 1. The mole fraction of water vapor in a gas mixture; 2. The mole fraction of dry hydrogen or dry air in a gas mixture ; and 3. The effects of interaction between water molecules and hydrogen as well as air molecules.
CO Preferential Oxidation Over Rh-supported Catalyst in H2-rich Gas for Fuel Cell Applications
Authors: Specchia Stefania , Galletti Camilla , Fiorot Sabina , Saracco Guido , Specchia Vito
Published: May 2007

The CO-PROX process can reduce CO concentration in hydrogen- rich gases down to 10 ppmv, to avoid poisoning of PEM fuel cells electrocatalysts. Rh-based catalysts on mixed alumina + 3A zeolite support were prepared and tested in temperature range compatible with that of PEMFCs (80-100{degree sign}C). In order to determine the catalyst highest oxygen selectivity toward CO oxidation with the lowest hydrogen loss, tests with decreasing feed oxygen concentration were carried out. The optimum O2 feed concentration was that corresponding to λ=O/CO=2 (selectivity equal to 0.5). At this λ value and heigher weight space velocity, an increase in the temperature range of complete CO conversion was obtained. Finally, to reduce the catalyst costs, tests at lower Rh load (from 1% to 0.5%) were carried out. No significant variations in activity resulted for 0.5% Rh-MIX catalyst, only the temperature range of complete CO conversion being slightly enhanced.
Development of the Variable Multi-ejector for a Mini-bus PEMFC System
Authors: Kim Minjin , Lee Won-Yong , Kim Chang-Soo
Published: May 2007

The ejector for the hydrogen recirculation system is necessary to improve the efficiency of the fuel cell mini-bus system. However, conventional ejector does not keep the good performance throughout the wide operating range though the mini-bus system requires the various power form the fuel cell. In this study, the variable multi-ejector acceptable in the whole power range required from the mini-bus is developed. Consequently, the entrainment ratio of the developed ejector is verified by the experiments based on the real operating conditions during the city tour mode.
The Renewable Energy System in the Building GlashusEtt - Stockholm
Authors: Rissanen Markku M. , Bark Gunnar , Lindman Eva-Katrin
Published: May 2007

This paper describes a renewable energy system, consisting of solar cells, an electrolyzer, hydrogen storage, a fuel cell system and a control system, which has been evaluated during 3 years. Results and experiences are described with focus on the two fuel cell systems that were operated.
Continuous inhalation of carbon monoxide induces right ventricle ischemia and dysfunction in rats with hypoxic pulmonary hypertension
Authors: Gautier Mathieu , Antier Daniel , Bonnet Pierre , Net Jean-Loic Le , Hanton Gilles , Eder Veronique
Published: May 2007

We aimed to investigate the toxicity of carbon monoxide (CO) in rats with right ventricle (RV) remodeling induced by hypoxic pulmonary hypertension (PHT). A group of Wistar rats was exposed to 3-wk hypobaric hypoxia (H). A second group was exposed to 50 ppm CO for 1 wk (CO). A third group was exposed to chronic hypoxia including 50 ppm CO during the third week (H+CO). These groups were compared with controls. RV and left ventricle (LV) functions were assessed by echocardiography and transparietal catheterization. Ventricular perfusion was estimated with the fluorescent microsphere method. Results were confirmed by histology. PHT induced RV hypertrophy and function enhancement. In the H group, RV shortening fraction (RVSF; 71 ± 12% vs. 41 ± 2%) and RV end-systolic pressure (RVESP; 54 ± 6 vs. 19 ± 2 mmHg) were increased compared with controls. Moreover, myocardial perfusion was increased in the RV (36 ± 2% vs. 22 ± 2%) and decreased in the LV (64 ± 3% vs. 78 ± 2%). In the H+CO group, RVSF (45 ± 3% vs. 71 ± 12%) and RVESP (38 ± 3 vs. 54 ± 6 mmHg) were decreased compared with the H group. RV perfusion was decreased in the H+CO group compared with the H group (21 ± 5% vs. 36 ± 2%), and LV perfusion was increased (79 ± 5% vs. 64 ± 3%). PHT and RV hypertrophy were still present in the H+CO group, and fibroses localized in the RV were detected. Similar lesions were observed in an additional group exposed simultaneously to hypoxia and 50 ppm CO over 3 wk. We demonstrated that rats with established PHT were more sensitive to CO, which dramatically alters the RV adaptive response to PHT, leading to ischemic lesions.
CM-MM and ACE genotypes and physiological prediction of the creatine kinase response to exercise
Authors: Heled Yuval , Bloom Michael S. , Wu T. John , Stephens Quiona , Deuster Patricia A.
Published: May 2007

Exertional rhabdomyolysis (ERB) is a syndrome of severe skeletal muscle breakdown. Blood levels of creatine kinase (CK) are widely used as a marker to reflect muscle breakdown. Some individuals exhibit extreme increases in blood CK after exercise and have been characterized as high responders (HR), but no clinical definition of HR exists and reasons for the HR phenomenon are not understood. This study investigated possible associations between the magnitude of the CK response to exercise and polymorphisms of two genes: muscle-specific creatine kinase (CK-MM) NcoI and angiotensin-converting enzyme (ACE) I/D. An exercise test for defining HR was also investigated. Participants ( n = 88) underwent an exercise test that included stepping up and down two stairs for 5 min followed by 15 squats while wearing a backpack weighted at 30% of their body weight. CK levels were measured before, immediately after, and 48 and 72 h after the test. Nine participants (10.2%) were defined as HR. Participants with the CK-MM NcoI AA genotype had a sixfold higher risk of being HR compared with GG and AG genotypes ( P = 0.031). No significant differences were found for the ACE I/D polymorphism. Percent body fat was an independent predictor of being a HR. We conclude that the CK-MM AA genotype and percent body fat may be part of the constellation of mechanisms that explain susceptibility to ERB. A physiological test that may assist in predicting ERB is also presented.
Chronic static magnetic field exposure alters microvessel enlargement resulting from surgical intervention
Authors: Morris Cassandra E. , Skalak Thomas C.
Published: May 2007

Magnetic field therapy has recently become a widely used complementary/alternative medicine for the treatment of vascular, as well as other musculoskeletal pathologies, including soft tissue injuries. Recent studies in our laboratory and others have suggested that acute static magnetic field (SMF) exposure can have a modulatory influence on the microvasculature, acting to normalize vascular function; however, the effect of chronic SMF exposure has not been investigated. This study aimed to measure, for the first time, the adaptive microvascular response to a chronic 7-day continuous magnetic field exposure. Murine dorsal skinfold chambers were applied on day 0, and neodymium static magnets (or size and weight-matched shams) were affixed to the chambers at day 0, where they remained until day 7. Separate analysis of arteriolar and venular diameters revealed that chronic SMF application significantly abrogated the luminal diameter expansion observed in sham-treated networks. Magnet-treated venular diameters were significantly reduced at day 4 and day 7 (34.3 and 54.4%, respectively) compared with sham-treated vessels. Arteriolar diameters were also significantly reduced by magnet treatment at day 7 (50%), but not significantly at day 4 (31.6%), although the same trend was evident. Venular functional length density was also significantly reduced (60%) by chronic field application. These results suggest that chronic SMF exposure can alter the adaptive microvascular remodeling response to mechanical injury, thus supporting the further study of chronic application of SMFs for the treatment of vascular pathologies involving the dysregulation of microvascular structure.
Inhibition of Angiogenesis and Tumor Metastasis by Targeting a Matrix Immobilized Cryptic Extracellular Matrix Epitope in Laminin
Authors: Akalu Abebe , Roth Jennifer M. , Caunt Maresa , Policarpio Desiree , Liebes Leonard , Brooks Peter C.
Published: May 2007

Angiogenesis and tumor metastasis depend on extracellular matrix (ECM) remodeling and subsequent cellular interactions with these modified proteins. An in-depth understanding of how both endothelial and tumor cells use matrix-immobilized cryptic ECM epitopes to regulate invasive cell behavior may lead to the development of novel strategies for the treatment of human tumors. However, little is known concerning the existence and the functional significance of cryptic laminin epitopes in regulating angiogenesis and tumor cell metastasis. Here, we report the isolation and characterization of a synthetic peptide that binds to a cryptic epitope in laminin. The STQ peptide selectively bound denatured and proteolyzed laminin but showed little interaction with native laminin. The cryptic laminin epitope recognized by this peptide was selectively exposed within malignant melanoma in vivo, whereas little if any was detected in normal mouse skin. Moreover, the STQ peptide selectively inhibited endothelial and tumor cell adhesion, migration, and proliferation in vitro and inhibited angiogenesis, tumor growth, and experimental metastasis in vivo. This inhibitory activity was associated with a selective up-regulation of the cyclin-dependent kinase inhibitor P27KIP1 and induction of cellular senescence. These novel findings suggest the existence of functionally relevant cryptic laminin epitopes in vivo and that selective targeting of these laminin epitopes may represent an effective new strategy for the treatment of malignant tumors by affecting both the endothelial and tumor cell compartments. [Cancer Res 2007;67(9):4353–63]
The Hinge Region Regulates DNA Binding, Nuclear Translocation, and Transactivation of the Androgen Receptor
Authors: Haelens Annemie , Tanner Tamzin , Denayer Sarah , Callewaert Leen , Claessens Frank
Published: May 2007

The androgen receptor (AR) encoding gene can undergo mutations during the development and treatment of prostate cancer. Even in hormone-independent stages, mutations in the receptor paradoxically seem to result in an increased AR function. Two such point mutations have been described in the part of the AR involved in DNA binding and nuclear translocation, namely the hinge region. Despite a decreased nuclear translocation, these mutant ARs display increased transactivating potencies. Through detailed analysis of the hinge region, we found that deletion of residues 629 to 636 resulted in a stronger androgen response on different reporters, although this mutant displays an extremely low in vitro affinity for androgen response elements. This superactivity is independent of nuclear localization and can be inhibited by antiandrogens. Surprisingly, the AR activation functions, AF1 and AF2, are not dramatically affected when the inhibitory region (629-RKLKKLGN-636) is deleted, although cotransfected p160 coactivator TIF2 had a stronger potentiating effect in the absence of this motif. The ligand-dependent interaction between the amino-terminal domain and the ligand-binding domain (N/C interaction) plays an important role in transactivation by the AR. We found that this interaction is strongly enhanced by deletion of the inhibitory region. In conclusion, the description of prostate cancer mutations has led to the discovery of a complex role of the hinge region in nuclear localization, DNA binding, coactivator recruitment, and N/C interaction of the AR. [Cancer Res 2007;67(9):4514–23]
ErbB-2 Induces the Cyclin D1 Gene in Prostate Epithelial Cells In vitro and In vivo
Authors: Casimiro Mathew , Rodriguez Olga , Pootrakul Llana , Aventian Maral , Lushina Nadia , Cromelin Caroline , Ferzli Georgina , Johnson Kevin , Fricke Stanley , Diba Fantahun , Kallakury Bhaskar , Ohanyerenwa Chioma , Chen Maxine , Ostrowski Michael , Hung Mien-Chie , Rabbani Shafaat A. , Datar Ram , Cote Richard , Pestell Richard , Albanese Chris
Published: May 2007

The receptor tyrosine kinase ErbB-2 plays an important role in the regulation of growth factor–induced signal transduction cascades in the epithelium, and ErbB-2 is frequently overexpressed in epithelial tumors. Our previous studies on clinical prostate cancer specimens indicated that ErbB-2 expression was increased in patients undergoing hormone ablation therapy. We had also shown that the critical cell cycle regulatory gene cyclin D1 and its promoter were targets of proliferative signaling in prostate cancer cell lines, and that cyclin D1 was required for ErbB-2–induced mammary tumorigenesis. In the current studies, we found that increased ErbB-2 membrane expression correlated with increased nuclear cyclin D1 staining in clinical prostate cancer specimens, and that expression of ErbB-2 was capable of inducing cell cycle progression in human prostate cancer cell lines. We further showed that ErbB-2 induced the cyclin D1 promoter in DU145 cells, and that small interfering RNA knockdown of cyclin D1 protein levels blocked a significant proportion of the heregulin-induced cell cycle progression in LNCaP cells. Probasin promoter–targeted expression of an activated ErbB-2 isoform induced cyclin D1 expression in the mouse prostate, commensurate with prostate intraepithelial neoplasia. Together, these in vitro and in vivo studies identify cyclin D1 as a critical downstream target of ErbB-2 in the prostate epithelium, both of which are possible therapeutic targets for cancer intervention. Furthermore, our novel mouse model provides a useful platform for ongoing in vivo investigations of ErbB-2 signaling in the prostate epithelium. [Cancer Res 2007;67(9):4364–72]
Hypoxia and Hypoxia-Inducible Factor-1 Expression Enhance Osteolytic Bone Metastases of Breast Cancer
Authors: Hiraga Toru , Kizaka-Kondoh Shinae , Hirota Kiichi , Hiraoka Masahiro , Yoneda Toshiyuki
Published: May 2007

Hypoxia is a common feature of solid tumors and is associated with their malignant phenotype. The transcription factor hypoxia-inducible factor-1 (HIF-1) is a major regulator of adaptation to hypoxia and is implicated in the malignant progression of cancers. Here, we studied whether hypoxia and HIF-1 expression contribute to the development of bone metastases using a well-characterized animal model of bone metastasis in MDA-MB-231 human breast cancer cells. To study the role of hypoxia in bone metastases, we tested the effects of the fusion protein (TOP3), the oxygen-dependent degradation domain of HIF-1α fused with HIV-TAT, and procaspase-3. TOP3 selectively induced apoptosis in hypoxic tumor cells in vitro and significantly reduced bone metastases in vivo. We next examined the role of HIF-1 in bone metastases by establishing MDA-MB-231 cells overexpressing constitutively active or dominant-negative HIF-1α (MDA/CA-HIF or MDA/DN-HIF, respectively). Bone metastases of MDA/CA-HIF were significantly increased with elevated number of CD31-positive blood vessels. In contrast, bone metastases were significantly reduced in MDA/DN-HIF. Because the progression of osteolytic bone metastases is due in part to the imbalance between bone formation and bone resorption, we examined the effects of hypoxia and HIF-1 on the differentiation of osteoblasts and osteoclasts. Hypoxia and CA-HIF overexpression markedly inhibited osteoblastic differentiation, whereas hypoxia increased osteoclast-like cell formation. In conclusion, these results suggest that tumor-associated hypoxia and HIF-1 expression promote the progression of bone metastases in breast cancer. Our results also suggest that hypoxia and HIF-1 lead to the development of osteolytic bone metastases by suppressing osteoblast differentiation and promoting osteoclastogenesis. [Cancer Res 2007;67(9):4157–63]
Monocarboxylate Transporter 4 Regulates Maturation and Trafficking of CD147 to the Plasma Membrane in the Metastatic Breast Cancer Cell Line MDA-MB-231
Authors: Gallagher Shannon M. , Castorino John J. , Wang Dian , Philp Nancy J.
Published: May 2007

Metastatic cancer cells increase glucose consumption and metabolism via glycolysis, producing large quantities of lactate. Recent work has shown that lactate efflux is mediated by monocarboxylate transporters (MCT), which are composed of a catalytic unit (MCT) and an accessory subunit (CD147), comprising the functional lactate transporter. CD147, an extracellular matrix metalloproteinase (MMP) inducer, is highly expressed in metastatic cancer cells. Because aerobic glycolysis is a hallmark of metastatic cancer, we examined whether increases in CD147 expression were linked to MCT expression in MDA-MB-231, a highly metastatic breast cancer cell line. MCT4 mRNA and protein expression were increased in MDA-MB-231 cells compared with cells derived from normal mammary tissue. MCT4 colocalized with CD147 in the plasma membrane and in membrane blebs shed from the cell surface. Small interfering RNA–mediated silencing of MCT4 impaired the maturation and trafficking of CD147 to the cell surface, resulting in accumulation of CD147 in the endoplasmic reticulum. Silencing MCT4 also resulted in fewer membrane blebs and decreased migration of MDA-MB-231 cells in vitro. Knockdown of CD147 resulted in loss of MCT4 in the plasma membrane and accumulation of the transporter in endolysosomes. These studies establish for the first time that increased expression of CD147 in metastatic cancer cells is coupled to the up-regulation of MCT4. The synergistic activities of the MCT/CD147 complex could facilitate migration of tumor cells by CD147-mediated MMP induction and lactate-stimulated angiogenesis and hyaluronan production. These data provide a molecular link between two hallmarks of metastatic cancer: the glycolytic switch and increased expression of CD147. [Cancer Res 2007;67(9):4182–9]
Kaposi's Sarcoma–Associated Herpesvirus-Encoded Interleukin-6 and G-Protein–Coupled Receptor Regulate Angiopoietin-2 Expression in Lymphatic Endothelial Cells
Authors: Vart Richard J. , Nikitenko Leonid L. , Lagos Dimitrios , Trotter Matthew W.B. , Cannon Mark , Bourboulia Dimitra , Gratrix Fiona , Takeuchi Yasuhiro , Boshoff Chris
Published: May 2007

Kaposi's sarcoma (KS) is caused by Kaposi's sarcoma–associated herpesvirus (KSHV) and consists of proliferating spindle cells, which are related to lymphatic endothelial cells (LEC). Angiopoietin-2 (Ang2) is a secreted proangiogenic and lymphangiogenic molecule. Here, we show the expression of Ang2 protein in KS and confirm that KSHV infection up-regulates Ang2 in LEC. We show that a paracrine mechanism contributes to this up-regulation. A lentiviral library of individual KSHV-encoding genes, comprising the majority of known latent genes and a selection of lytic viral genes, was constructed to investigate the underlying mechanism of this up-regulation. Two lytic genes, viral interleukin-6 (vIL6) and viral G-protein–coupled receptor (vGPCR), up-regulated Ang2 expression in LEC. Both vIL6 and vGPCR are expressed in KSHV-infected LEC and caused up-regulation of Ang2 in a paracrine manner. KSHV, vIL6, and vGPCR up-regulated Ang2 through the mitogen-activated protein kinase (MAPK) pathway. Gene expression microarray analysis identified several other angiogenic molecules affected by KSHV, including the vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) axis, which is also affected by vIL6 and vGPCR in LEC, and matrix metalloproteinases, which could act in concert with Ang2 to contribute to KS development. These findings support the paracrine and autocrine roles of the lytic KSHV-encoded proteins, vIL6 and vGPCR, in KS pathogenesis and identify Ang2 as a potential therapeutic target for this neoplasm. [Cancer Res 2007;67(9):4042–50]
The Novel Triterpenoid C-28 Methyl Ester of 2-Cyano-3, 12-Dioxoolen-1, 9-Dien-28-Oic Acid Inhibits Metastatic Murine Breast Tumor Growth through Inactivation of STAT3 Signaling
Authors: Ling Xiaoyang , Konopleva Marina , Zeng Zhihong , Ruvolo Vivian , Stephens L. Clifton , Schober Wendy , McQueen Teresa , Dietrich Martin , Madden Timothy L. , Andreeff Michael
Published: May 2007

We and others have reported that C-28 methyl ester of 2-cyano-3, 12-dioxoolen-1, 9-dien-28-oic acid (CDDO-Me) effectively inhibits the growth of multiple cancer cell types. Our previous studies indicated that prolonged CDDO-Me treatment inactivated extracellular signal-regulated kinase signaling in acute myelogenous leukemia cells. Whether treatment with CDDO-Me has an earlier effect on other proteins that are important for either signal transduction or oncogenesis is unknown. Constitutively activated signal transducer and activator of transcription 3 (STAT3) is frequently found in human breast cancer samples. Constitutively activated STAT3 was shown to up-regulate c-Myc in several types of cancer and has a feedback effect on Src and Akt. To examine the effects of CDDO-Me on STAT3 signaling in breast cancer, we used the murine 4T1 breast tumor model, which is largely resistant to chemotherapy. In vitro, after treatment of 4T1 cells with 500 nmol/L CDDO-Me for 2 h, we found (a) inactivation of STAT3, (b) inactivation of Src and Akt, (c) 4-fold reduction of c-Myc mRNA levels, (d) accumulation of cells in G2-M cell cycle phase, (e) abrogation of invasive growth of 4T1 cells, and (f) lack of apoptosis induction. In in vivo studies, CDDO-Me completely eliminated 4T1 breast cancer growth and lung metastases induced by 4T1 cells in mice when treatment started 1 day after tumor implantation and significantly inhibited tumor growth when started after 5 days. In vivo studies also indicated that splenic mature dendritic cells were restored after CDDO-Me treatment. In summary, these data suggest that CDDO-Me may have therapeutic potential in breast cancer therapy, in part, through inactivation of STAT3. [Cancer Res 2007;67(9):4210–17]
Reduced PDEF Expression Increases Invasion and Expression of Mesenchymal Genes in Prostate Cancer Cells
Authors: Gu Xuesong , Zerbini Luiz F. , Otu Hasan H. , Bhasin Manoj , Yang Quanli , Joseph Marie G. , Grall Franck , Onatunde Tomi , Correa Ricardo G. , Libermann Towia A.
Published: May 2007

The epithelium-specific Ets transcription factor, PDEF, plays a role in prostate and breast cancer, although its precise function has not been established. In prostate cancer, PDEF is involved in regulating prostate-specific antigen expression via interaction with the androgen receptor and NKX3.1, and down-regulation of PDEF by antiproliferative agents has been associated with reduced PDEF expression. We now report that reduced expression of PDEF leads to a morphologic change, increased migration and invasiveness in prostate cancer cells, reminiscent of transforming growth factor β (TGFβ) function and epithelial-to-mesenchymal transition. Indeed, inhibition of PDEF expression triggers a transcriptional program of genes involved in the TGFβ pathway, migration, invasion, adhesion, and epithelial dedifferentiation. Our results establish PDEF as a critical regulator of genes involved in cell motility, invasion, and adhesion of prostate cancer cells. [Cancer Res 2007;67(9):4219–26]
Cortactin Is an Essential Regulator of Matrix Metalloproteinase Secretion and Extracellular Matrix Degradation in Invadopodia
Authors: Clark Emily S. , Whigham Amy S. , Yarbrough Wendell G. , Weaver Alissa M.
Published: May 2007

Invadopodia are branched actin-rich structures associated with extracellular matrix (ECM) degradation that collectively form the invasive machinery of aggressive cancer cells. Cortactin is a prominent component and a specific marker of invadopodia. Amplification of cortactin is associated with poor prognosis in head and neck squamous cell carcinomas (HNSCC), possibly because of its activity in invadopodia. Although the role of cortactin in invadopodia has been attributed to signaling and actin assembly, it is incompletely understood. We made HNSCC cells deficient in cortactin by RNA interference knockdown methods. In these cortactin knockdown cells, invadopodia were reduced in number and lost their ability to degrade ECM. In the reverse experiment, overexpression of cortactin dramatically increased ECM degradation, far above and beyond the effect on formation of actin/Arp3–positive invadopodia puncta. Secretion of matrix metalloproteinases (MMP) MMP-2 and MMP-9, as well as plasma membrane delivery of MT1-MMP correlated closely with cortactin expression levels. MMP inhibitor treatment of control cells mimicked the cortactin knockdown phenotype, with abolished ECM degradation and fewer invadopodia, suggesting a positive feedback loop in which degradation products from MMP activity promote new invadopodia formation. Collectively, these data suggest that a major role of cortactin in invadopodia is to regulate the secretion of MMPs and point to a novel mechanism coupling dynamic actin assembly to the secretory machinery, producing enhanced ECM degradation and invasiveness. Furthermore, these data provide a possible explanation for the observed association between cortactin overexpression and enhanced invasiveness and poor prognosis in HNSCC patients. [Cancer Res 2007;67(9):4227–35]
Down-Regulation of Phosphoglucose Isomerase/Autocrine Motility Factor Results in Mesenchymal-to-Epithelial Transition of Human Lung Fibrosarcoma Cells
Authors: Funasaka Tatsuyoshi , Hu Huankai , Yanagawa Takashi , Hogan Victor , Raz Avraham
Published: May 2007

Phosphoglucose isomerase (PGI) is one of the glycolytic enzymes and is a multifunctional enzyme that functions in glucose metabolism inside the cell while acting as a cytokine outside the cell, with properties that include autocrine motility factor (AMF) regulating tumor cell motility. Although there are many studies indicating that PGI/AMF has been implicated in progression of metastasis, no direct studies of the significance of exogenous PGI/AMF on tumor progression have been reported. Here, we report on the mesenchymal-to-epithelial transition (MET), which is the reverse phenomenon of the epithelial-to-mesenchymal transition that is associated with loss of cell polarity, loss of epithelia markers, and enhancement of cell motility essential for tumor cell invasion and metastasis. Mesenchymal human fibrosarcoma HT1080 cells, which have naturally high levels of endogenous and exogenous PGI/AMF, were stably transfected with PGI/AMF small interfering RNA (siRNA). The siRNA targeting human PGI/AMF down-regulated the endogenous PGI/AMF expression and completely extinguished the secretion of PGI/AMF in a human fibrosarcoma HT1080, whereas the control siRNA showed no effects. The PGI/AMF siRNA caused cells to change shape dramatically and inhibited cell motility and invasion markedly. Suppression of PGI/AMF led to a contact-dependent inhibition of cell growth. Those PGI/AMF siRNA-transfected cells showed epithelial phenotype. Furthermore, tumor cells with PGI/AMF deficiency lost their abilities to form tumor mass. This study identifies that MET in HT1080 human lung fibrosarcoma cells was initiated by down-regulation of the housekeeping gene product/cytokine PGI/AMF, and the results depicted here suggest a novel therapeutic target/modality for mesenchymal cancers. [Cancer Res 2007;67(9):4236–8]
Cross-talk between Paracrine-Acting Cytokine and Chemokine Pathways Promotes Malignancy in Benign Human Prostatic Epithelium
Authors: Ao Mingfang , Franco Omar E. , Park Dean , Raman Dayanidhi , Williams Karin , Hayward Simon W.
Published: May 2007

The present study explores the mechanisms by which human prostatic carcinoma-associated fibroblasts (CAF) induce tumorigenesis in initiated but nonmalignant human prostatic epithelial cells (BPH-1). CAF express elevated levels of both transforming growth factor-β1 (TGF-β1) and stromal cell–derived factor-1 (SDF-1/CXCL12). TGF-β inhibits the growth of BPH-1 cells in vitro, but was found to be necessary for the tumorigenic response to CAF. This counterintuitive result suggested that the TGF-β signaling system was involved in other processes relating to tumorigenesis. The SDF-1 receptor, CXCR4, is expressed at low levels in benign prostate tissue and in BPH-1 cells in culture. However, CXCR4 levels increase during prostate cancer progression. CXCR4 was found to be induced and localized to the cell membrane in BPH1 cells by CAF-conditioned medium and by CAF cells in tissue recombinants. TGF-β was both necessary and sufficient to allow the detection of membrane-localized CXCR4 in BPH1 cells. Suppression of epithelial cell CXCR4 expression abrogated the tumorigenic response to CAF. SDF-1, secreted by CAF, acts via the TGF-β–regulated CXCR4 to activate Akt in the epithelial cells. This mechanism elicits tumorigenesis and obviates the growth-inhibitory effects of TGF-β. Thus, tumor stroma can contribute to carcinogenesis through synergism between TGF-β, SDF-1, and CXCR4. These experiments suggest mechanisms by which TGF-β can shift its role from an inhibitor to a promoter of proliferation during tumor progression. Both the TGF-β and SDF-1 pathways are targets of drug discovery efforts; these data suggest potential benefits in the cotargeting of these pathways. [Cancer Res 2007;67(9):4244–53]
Thrombin-Cleaved COOH-Terminal Osteopontin Peptide Binds with Cyclophilin C to CD147 in Murine Breast Cancer Cells
Authors: Mi Zhiyong , Oliver Tim , Guo Hongtao , Gao Chengjiang , Kuo Paul C.
Published: May 2007

Osteopontin is a glycoprotein that has been linked to metastatic function in breast, lung, and prostate cancers. However, the mechanism by which osteopontin acts to induce metastatic properties is largely unknown. One intriguing feature of osteopontin is the presence of a conserved thrombin cleavage site that is COOH-terminal from a well-characterized RGD domain. Although the COOH-terminal fragment may bind to cell surface CD44 receptors, little is known about the COOH-terminal osteopontin fragment. In the current study, we use the murine mammary epithelial tumor cell lines 4T1 and 4T07; these cells are thioguanine-resistant sublines derived from the parental population of 410.4 cells from Balb/cfC3H mice. Using flow cytometry and Forster resonance energy transfer, we show that the COOH-terminal fragment of osteopontin binds with another marker of metastatic function (cyclophilin C or rotamase) to the CD147 cell surface glycoprotein (also known as extracellular matrix metalloproteinase inducer), to activate Akt1/2 and matrix metalloproteinase-2. In in vitro assays, thrombin cleavage of osteopontin to generate short COOH-terminal osteopontin in the presence of cyclophilin C increases migration and invasion of both 4T07 and 4T1 cells. This interaction between osteopontin peptide and cyclophilin C has not been previously described but assigns a heretofore unknown function for the thrombin-cleaved osteopontin COOH-terminal fragment. [Cancer Res 2007;67(9):4088–97]
Listeria monocytogenes Promotes Tumor Growth via Tumor Cell Toll-Like Receptor 2 Signaling
Authors: Huang Bo , Zhao Jie , Shen Shiqian , Li Hongxing , He Kai-Li , Shen Guan-Xin , Mayer Lloyd , Unkeless Jay , Li Dong , Yuan Ye , Zhang Gui-Mei , Xiong Huabao , Feng Zuo-Hua
Published: May 2007

The contribution of bacterial infection to tumorigenesis is usually ascribed to infection-associated inflammation. An alternate view is that direct interaction of bacteria with tumor cells promotes tumor progression. Here, we show that the microenvironment of large tumors favors bacterial survival, which in turn directly accelerates tumor growth by activating tumor cell Toll-like receptors (TLR). Listeria monocytogenes (Lm) survives in the microenvironment of large but not small tumors, resulting in the promotion of tumor growth. Lm did not affect the percentage of regulatory T cells or myeloid suppressor cells in the tumor. Through TLR2 signaling, Lm activated mitogen-activated protein kinases and nuclear factor-κB in tumor cells, resulting in the increased production of nitric oxide and interleukin-6 and increased proliferation of tumor cells. All of these effects were abrogated by silencing expression of TLR2, but not TLR4. The interaction of Helicobacter pylori with tumor cells from gastric carcinoma patients resulted in similar effects. These findings provide a new insight into infection-associated tumorigenesis and illustrate the importance of antibiotic therapy to treat tumors with bacterial infiltration. [Cancer Res 2007;67(9):4346–52]
Angiopoietin-2 Stimulates Breast Cancer Metastasis through the α5β1 Integrin-Mediated Pathway
Authors: Imanishi Yorihisha , Hu Bo , Jarzynka Michael J. , Guo Ping , Elishaev Esther , Bar-Joseph Ifat , Cheng Shi-Yuan
Published: May 2007

Acquisition of a metastatic phenotype by breast cancer cells includes alternations of multigenic programs that permit tumor cells to metastasize to distant organs. Here, we report that angiopoietin-2 (Ang2), a known growth factor, is capable of promoting breast cancer cell invasion leading to metastasis. Analysis of 185 primary human breast cancer specimens that include 97 tumors showing lymph node and/or distant metastasis reveals a significant correlation between the expression of Ang2 and E-cadherin, Snail, metastatic potential, tumor grade, and lymph-vascular invasion during breast cancer progression. Using a xenograft model, we show that overexpression of Ang2 in poorly metastatic MCF-7 breast cancer cells suppresses expression of E-cadherin and induces Snail expression and phosphorylation of Akt and glycogen synthase kinase-3β (GSK-3β) promoting metastasis to the lymph nodes and lung. In cell culture, Ang2 promotes cell migration and invasion in Tie2-deficient breast cancer cells through the α5β1 integrin/integrin-linked kinase (ILK)/Akt, GSK-3β/Snail/E-cadherin signaling pathway. Inhibition of ILK and the α5β1 integrin abrogates Ang2 modulation of Akt, GSK-3β, Snail, and E-cadherin and Ang2-stimulated breast cancer cell migration and invasion. Together, these results underscore the significant contribution of Ang2 in cancer progression, not only by stimulating angiogenesis but also by promoting metastasis, and provide a mechanism by which breast cancer cells acquire an enhanced invasive phenotype contributing to metastasis. [Cancer Res 2007;67(9):4254–63]