bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel non-Pt PEM Fuel Cell Cathode Catalysts Based on Heteropoly Acid Materials
Authors: Stanis Ronald J. , Kuo Mei Chen , Turner John A. A. , Herring Andrew M.
Published: May 2008

Heteropoly acids were investigated to determine their activity as non-Pt oxygen reduction reaction (ORR) catalysts in polymer electrolyte membrane fuel cell cathodes (PEMFCs). Polarization curves, cyclic voltammetry, and impedance spectroscopy results determined that, of the HPAs tested, only Mo based HPAs are active for the ORR and that V substitutions can improve the activity. Power densities of 67mW at 0.2V were obtained using H5PMo10V2O40. The catalysts must first be reduced insitu before the HPA can reduce oxygen. The reduction potentials of the HPAs in the fuel cell environment were determined by cyclic voltammetry and provide an explanation for why no activity is seen above 0.55V. Impedance spectroscopy confirmed that V substitutions increase catalytic activity. The potential at which the HPA can be reduced by 4 electrons has been determined to be the limiting factor when using these catalysts for ORR in PEMFCs.
Direct Methane Proton Exchange Membrane Fuel Cell
Authors: Tyagi Sarika , Ganesh Anuradda , Aghalayam Preeti
Published: May 2008

The direct methane proton exchange membrane fuel cell was demonstrated for the first time. A Nafion membrane doped with phosphoric acid was used as the electrolyte. Pd/C, Pd-Ru/C and Pd-Au/C were studied as the anode catalysts with catalyst loading of 0.2mg/cm2. Selection of these catalysts for the studies was made based on the activation energy obtained by calculation using the UBI-QEP method. It was shown among these catalysts; Pd-Au/C anode exhibited a maximum open circuit voltage of 0.55V with current density of 30mA/cm2. It was also seen that by bleeding oxygen on anode side, open circuit voltage was 0.74V and current density was increased to 160mA/cm2.
Carbon Nanotube Electrode Materials for Li-air Cells
Authors: Dai Jinxiang , Kogut Thomas , Jin Lei , Reisner David
Published: May 2008

In this paper, carbon nanotubes (CNTs) have been investigated as oxygen cathode materials used for Li-oxygen/air cells and compared with carbon black (CB), graphite (G), and active carbon (AC). Both multi wall nanotube (MWNT) and single wall nanotube (SWNT) showed advantage when compared with other types of carbonaceous materials. The higher discharge capacity of CNTs than AC is explained by the exposed surface area surface area. SWNT is very promising as a cathode material in terms of higher capacity and energy density for Li-oxygen/air cells, while MWNT has low cost advantages. CNT based high energy density Li-oxygen/air cells have the potential to be developed into high next generation specific energy power sources.
Postconditioning for salvage of ischemic skeletal muscle from reperfusion injury: efficacy and mechanism
Authors: McAllister Sandra E. , Ashrafpour Homa , Cahoon Neil , Huang Ning , Moses Michael A. , Neligan Peter C. , Forrest Christopher R. , Lipa Joan E. , Pang Cho Y.
Published: May 2008

We tested our hypothesis that postischemic conditioning (PostC) is effective in salvage of ischemic skeletal muscle from reperfusion injury and the mechanism involves inhibition of opening of the mitochondrial permeability transition pore (mPTP). In bilateral 8 × 13 cm pig latissimus dorsi muscle flaps subjected to 4 h ischemia, muscle infarction increased from 22 ± 4 to 41 ± 1% between 2 and 24 h reperfusion and remained unchanged at 48 (38 ± 6%) and 72 (40 ± 1%) h reperfusion ( P < 0.05; n = 4 pigs). PostC induced by four cycles of 30-s reperfusion/reocclusion at the onset of reperfusion after 4 h ischemia reduced muscle infarction from 44 ± 2 to 22 ± 2% at 48 h reperfusion. This infarct protective effect of PostC was mimicked by intravenous injection of the mPTP opening inhibitor cyclosporin A or NIM-811 (10 mg/kg) at 5 min before the end of 4 h ischemia and was abolished by intravenous injection of the mPTP opener atractyloside (10 mg/kg) at 5 min before PostC ( P < 0.05; n = 4–5 pigs). PostC or intravenous cyclosporin A injection at 5 min before reperfusion caused a decrease in muscle myeloperoxidase activity and mitochondrial free Ca2+ concentration and an increase in muscle ATP content after 4 h ischemia and 2 h reperfusion compared with the time-matched controls. These effects of PostC were abolished by intravenous injection of atractyloside at 5 min before PostC ( P < 0.05; n = 6 pigs). These observations support our hypothesis that PostC is effective in salvage of ischemic skeletal muscle from reperfusion injury and the mechanism involves inhibition of opening of the mPTP.
Tonically Active Inhibition Selectively Controls Feedforward Circuits in Mouse Barrel Cortex
Authors: Krook-Magnuson Esther I. , Li Peijun , Paluszkiewicz Scott M. , Huntsman Molly M.
Published: May 2008

Tonic inhibition mediated by extrasynaptic γ-aminobutyric acid type A (GABAA) receptors is a powerful conductance that controls cell excitability. Throughout the CNS, tonic inhibition is expressed at varying degrees across different cell types. Despite a rich history of cortical interneuron diversity, little is known about tonic inhibition in the different classes of cells in the cerebral cortex. We therefore examined the cell-type specificity and functional significance of tonic inhibition in layer 4 of the mouse somatosensory barrel cortex. In situ hybridization and immunocytochemistry showed moderate δ-subunit expression across the barrel structures. Whole cell patch-clamp recordings additionally indicated that significant levels of tonic inhibition can be found across cell types, with differences in the magnitude of inhibition between cell types. To activate tonic currents, we used 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP, a superagonist at δ-subunit–containing GABAA receptors) at a concentration that did not affect synaptic decay kinetics. THIP produced greater shifts in baseline holding current in inhibitory cells (low-threshold spiking [LTS], 109 ± 17 pA; fast spiking [FS], 111 ± 15 pA) than in excitatory cells (39 ± 10 pA; P < 0.001). In addition to these differences across cell types, there was also variability within inhibitory cells. FS cells with faster action potentials had larger baseline shifts. Because FS cells are known mediators of feedforward inhibition, we tested whether THIP-induced tonic conductance selectively controls feedforward circuits. THIP application resulted in the abolishment of the inhibitory postsynaptic potential in thalamic-evoked disynaptic responses in a subset of excitatory neurons. These data suggest multiple feedforward circuits can be differentiated by the inhibitory control of the presynaptic inhibitory neuron.
High-temperature X-ray powder diffraction study of the tetragonal-cubic phase transition in nanocrystalline, compositionally homogeneous ZrO2–CeO2 solid solutions
Authors: Acuña L. M. , Fuentes R. O. , Lamas D. G. , Fábregas I. O. , Walsöe de Reca N. E. , Craievich A. F.
Published: May 2008

Crystal structure of compositionally homogeneous, nanocrystalline ZrO2–CeO2 solutions was investigated by X-ray powder diffraction as a function of temperature for compositions between 50 and 65 mol % CeO2. ZrO2-50 and 60 mol % CeO2 solid solutions, which exhibit the t′-form of the tetragonal phase at room temperature, transform into the cubic phase in two steps: t′-to-t″ followed by t″-to-cubic. But the ZrO2-65 mol % CeO2, which exhibits the t″-form, transforms directly to the cubic phase. The results suggest that t′-to-t″ transition is of first order, but t″-to-cubic seems to be of second order.
Pearlitic reaction in Cu-10wt%Al alloy with Ag additions
Authors: Adorno A. T. , Silva R. A. G. , Utuni V. H. S.
Published: May 2008

The pearlitic reaction in Cu-10wt%Al alloy with additions of 4, 6, 8, and 10wt%Ag was studied using scanning electron microscopy, energy dispersive X-ray microanalysis, in situ X-ray diffractometry, and microhardness measurements. The results indicated that the presence of Ag changes the pearlitic phase microstructure and its mechanical properties, because of the influence of Ag in the pearlitic phase growth mechanism.
Microstructure anisotropy in CuO powders
Authors: Bianchi A. E. , Montenegro L. , Viña R. , Punte G.
Published: May 2008

An anisotropic line broadening study of CuO is reported. X-ray powder diffraction line width modifications observed are modeled when comparing data coming from (1) commercial analytical grade CuO, (2) energetic ball milling sample for 1 h, and (3) samples prepared by thermally annealing the ball milled sample at various temperatures. X-ray powder diffraction data from commercial and produced samples were analyzed by the Rietveld method using a pseudo-Voigt function. Different assumptions including size and strain anisotropy were tried to improve pattern fitting. An anisotropic strain broadening, modeled using Stephens’ approximation, yielded the best fit, thus indicating that strain anisotropy is the main source of the departure from a smooth function of line broadening as a function of 2θ observed in all samples.
X-ray diffraction and photoluminescence studies of zinc oxide films grown on silicon substrates by dc reactive magnetron sputtering
Authors: Juárez-Díaz G. , Solache-Carranco H. , R. G. Romero-Paredes , Peña-Sierra R. , Martínez-Juárez J. , Galeazzi R. , Esparza-García A. , Briseño-García M. , Henao J. A.
Published: May 2008

Thin polycrystalline ZnO films were grown on silicon substrates by dc reactive magnetron sputtering using zinc oxide targets. The quality of the ZnO layers was assessed by X-ray diffraction (XRD), atomic force microscopy, Raman scattering, and photoluminescence measurements. The XRD studies and Raman studies revealed that the ZnO films crystallize in the wurtzite structure. Room temperature photoluminescence spectra consisted of a narrow near-band-edge ultraviolet band and a broad defect-related green band with peak positions at 380 and 516 nm, respectively. The main goal of the work was to define the growth conditions to prepare zinc oxide films with adequate properties to be used in electroluminescent devices. The films exhibited the best surface appearance with a 40:1 argon/oxygen flow rate, a total pressure of 1.5×10−3 mbar, and a substrate temperature of 230 °C. The structural and luminescence properties improved noticeably with the thermal annealing processes at 800 °C for 1 h.
Aspects of solid state formation and properties of Sn0.9Ti0.1O2system doped with CoO and Nb2O5
Authors: Leite Daniela Russo , de Sousa Góes Márcio , Bueno Paulo Roberto , Varela José Arana , de Oliveira Paiva-Santos Carlos , Cilense Mario
Published: May 2008

The effect of calcination temperature during the formation of the solid solution Sn0.9Ti0.1O2doped with 1.00 mol % CoO and 0.05 mol % Nb2O5is presented. The structural characteristics of this system were studied using X-ray diffraction, and the changes in phase formation were analyzed using the Rietveld method. With an increase in calcination temperature, there is increasing miscibility of Ti into the (Ti,Sn)O2phase and near 1000 °C, and the remaining TiO2(anatase) was transformed into the rutile phase. The sintering process, monitored using dilatometry, suggests two mass transport mechanisms, one activated close to 900 °C associated with the presence of TiO2(anatase) and the second mechanism, occurring between 1200 and 1300 °C, is attributed to a faster grain boundary diffusion caused by oxygen vacancies.
Rietveld analysis of mechanically activated BaCO3–TiO2system
Authors: Góes Márcio de Sousa , Varela José Arana , Paiva-Santos Carlos de Oliveira , Stojanovic Biljana D. , Chaves de Andrade André Vitor
Published: May 2008

BaTiO3powders were prepared through mechanical activation chemistry and analyzed by Rietveld refinement with X-ray diffraction data. Raw BaCO3and TiO2powders were dry milled for 5 and 20 h and then calcinated for 2 and 4 h at 800 °C. The milling process was found to have broken up the BaCO3and TiO2crystals into smaller crystals and formed only small amounts (<1.5 wt%) of BaTiO3. Subsequence calcinations for 2 and 4 h at 800 °C successfully produced large amounts (>97.7 wt%) of BaTiO3crystals. The calcination process also generated microstrains and crystallite-size anisotropy in BaTiO3. An increase in the calcination time from 2 to 4 h increased the BaTiO3weight percentage and the crystallite-shape anisotropy, but decreased the tetragonal distortion anisotropic microstrains in BaTiO3crystals.
Employing X-ray scattering to characterize materials with grain sizes in the nano-regime
Authors: Laitila E. A. , Mikkola D. E.
Published: May 2008

This study focuses on characterization of an (Al,Cr)3Ti alloy processed together with titanium powder by reactive mechanical milling (RMM) to produce an ultrafine grained intermetallic alloy matrix with in situ carbide and hydride phases formed during processing. Observations of X-ray scattering as RMM processing time increases show severe broadening of matrix diffraction peaks, accompanied by the appearance of diffraction peaks resulting from the formation of very small crystallites of TiC and TiH1.92 phases with increasing volume fractions, and finally, increasing background intensity as the crystallite size of the matrix phase decreases to ∼2 nm. Estimates of phase volume fractions were made by the direct comparison method, along with crystallite sizes by Warren–Averbach peak profile analysis. The general increase in background intensities has been attributed to random static displacements of the large fraction of atoms located within the grain boundary regions. Further, it has been concluded that the matrix material with a crystallite size of a few nanometers has about half the atoms in statically displaced positions defining the boundary regions. The results argue that background intensity changes should not be ignored and are useful in interpreting scattering from these nano-scale materials.
Dislocation model of strain anisotropy
Authors: Ungár Tamás
Published: May 2008

Dislocation model of strain anisotropy is presented. The dislocation theorem of strain broadening is suggested which means that strain broadening can only be caused by dislocation-type lattice defects. Based on this theorem strain anisotropy is modeled and accounted for by assuming that strain broadening is caused by dislocations or dislocation-type lattice defects. The effect of strain anisotropy is summarized in hkl dependent dislocation contrast factors, which can be either averaged over the permutations of hkl indices or are different for each different reflection. The dislocation model of strain anisotropy provides a powerful tool to analyze slip activity, Burgers vector populations, and plasticity on the basis of line profile analysis.
Artesunate Derived from Traditional Chinese Medicine Induces DNA Damage and Repair
Authors: Li Paul C.H. , Lam Elena , Roos Wynand P. , Zdzienicka Małgorzata Z. , Kaina Bernd , Efferth Thomas
Published: June 2008

Artesunate is a semisynthetic derivative from artemisinin, a natural product from the Chinese herb Artemisia annua L. It exerts antimalarial activity, and, additionally, artemisinin and its derivatives are active against cancer cells. The active moiety is an endoperoxide bridge. Its cleavage leads to the formation of reactive oxygen species and carbon-centered radicals. These highly reactive molecules target several proteins in Plasmodia, which is thought to result in killing of the microorganism. DNA damage induced by artemisinins has not yet been described. Here, we show that artesunate induces apoptosis and necrosis. It also induces DNA breakage in a dose-dependent manner as shown by single-cell gel electrophoresis. This genotoxic effect was confirmed by measuring the level of γ-H2AX, which is considered to be an indication of DNA double-strand breaks (DSB). Polymerase β–deficient cells were more sensitive than the wild-type to artesunate, indicating that the drug induces DNA damage that is repaired by base excision repair. irs1 and VC8 cells defective in homologous recombination (HR) due to inactivation of XRCC2 and BRCA2, respectively, were more sensitive to artesunate than the corresponding wild-type. This was also true for XR-V15B cells defective in nonhomologous end-joining (NHEJ) due to inactivation of Ku80. The data indicate that DSBs induced by artesunate are repaired by the HR and NHEJ pathways. They suggest that DNA damage induced by artesunate contributes to its therapeutic effect against cancer cells. [Cancer Res 2008;68(11):4347–51]
CCAAT/Enhancer Binding Protein δ Up-regulates Aromatase Promoters I.3/II in Breast Cancer Epithelial Cells
Authors: Kijima Ikuko , Ye Jingjing , Glackin Carlotta , Chen Shiuan
Published: June 2008

Aromatase is the enzyme responsible for the last step of estrogen synthesis. The female hormone, estrogen, is known to stimulate breast cancer cell growth. Because the expression of aromatase in breast cancer tissues is driven by unique promoters I.3 and II, a more complete understanding of the regulatory mechanism of aromatase expression through promoters I.3/II in breast tumors should be valuable in developing targeted therapies, which selectively suppress estrogen production in breast tumor tissue. Results from in vivo footprinting analyses revealed several protein binding sites, numbered 1 to 5. When site 2 (−124/−112 bp, exon I.3 start site as +1) was mutated, promoters I.3/II activity was dramatically reduced, suggesting that site 2 is a positive regulatory element. Yeast one-hybrid screening revealed that a potential protein binding to site 2 was CCAAT/enhancer binding protein δ (C/EBPδ). C/EBPδ was shown to bind to site 2 of aromatase promoters I.3/II in vitro and in vivo. C/EBPδ up-regulated promoters I.3/II activity through this site and, as a result, it also up-regulated aromatase transcription and enzymatic activity. p65, a subunit of nuclear factor-κB (NF-κB) transcription factor, inhibited C/EBPδ–up-regulated aromatase promoters I.3/II and enzymatic activity. This inhibitory effect of p65 was mediated, in part, through prevention of the C/EBPδ binding to site 2. This C/EBPδ binding site in aromatase promoters I.3/II seems to act as a positive regulatory element in non–p65-overexpressing breast cancer epithelial cells, whereas it is possibly inactive in p65 overexpressing cancer epithelial cells, such as estrogen receptor–negative breast cancer cells. [Cancer Res 2008;68(11):4455–64]
Long-term In vitro Expansion Alters the Biology of Adult Mesenchymal Stem Cells
Authors: Izadpanah Reza , Kaushal Deepak , Kriedt Christopher , Tsien Fern , Patel Bindiya , Dufour Jason , Bunnell Bruce A.
Published: June 2008

Mesenchymal stem cells (MSC) derived from bone marrow stem cells (BMSC) and adipose tissue stem cells (ASC) of humans and rhesus macaques were evaluated for their cell cycle properties during protracted culture in vitro. Human ASCs (hASC) and rhesus BMSCs (rBMSC) underwent significantly more total population doublings than human BMSCs (hBMSC) and rhesus ASCs (rASC). The cell cycle profile of all MSCs was altered as cultures aged. hMSCs underwent an increase in the frequency of cells in the S phase at P20 and P30. However, rhesus MSCs from both sources developed a distinct polyploid population of cells at P20, which progressed to aneuploidy by P30. Karyotype analysis of MSCs revealed the development of tetraploid or aneuploid karyotypes in the rhesus cells at P20 or P30. Analysis of the transcriptome of the MSCs from early and late passages revealed significant alterations in the patterns of gene expression (8.8% of the genes were differentially expressed in hBMSCs versus hASCs, and 5.5% in rBMSCs versus rASCs). Gene expression changes were much less evident within the same cell type as aging occurred (0.7% in hMSCs and 0.9% in rMSC). Gene ontology analysis showed that functions involved in protein catabolism and regulation of pol II transcription were overrepresented in rASCs, whereas the regulation of IκB/nuclear factor-κB cascade were overrepresented in hBMSCs. Functional analysis of genes that were differentially expressed in rASCs and hBMSCs revealed that pathways involved in cell cycle, cell cycle checkpoints, protein-ubiquitination, and apoptosis were altered. [Cancer Res 2008;68(11):4229–38]
Cells Silenced forSDHBExpression Display Characteristic Features of the Tumor Phenotype
Authors: Cervera Ana M. , Apostolova Nadezda , Crespo Francisco Luna , Mata Manuel , McCreath Kenneth J.
Published: June 2008

Recently, enzymes of the tricarboxylic acid (TCA) cycle have emerged as novel tumor suppressors. In particular, mutations in the nuclear-encoded subunits of succinate dehydrogenase (SDHB, SDHC, and SDHD) cause paragangliomas and pheochromocytomas. Although the mechanism(s) by which disruption of mitochondrial metabolism leads to neoplasia is largely unknown, increasing evidence points to an activation of pseudohypoxia. In this study, we have shown that silencing of SDHB using DNA-based small interfering RNA resulted in major impairments in cellular proliferation, respiration, and a corresponding shift to glycolysis. The levels of reactive oxygen species, however, were unchanged. As expected, hypoxia-inducible factor-1α (HIF-1α) and HIF-2α were up-regulated in chronically silenced cells, suggesting that a pseudohypoxic state was attained. In addition, the c-Jun amino-terminal kinase and p38 kinase stress signaling proteins were hyperphosphorylated in SDHB-silenced cells. Microarray analysis showed that >400 genes were influenced (6-fold or more up-regulation or down-regulation) by silencing of SDHB, confirming the importance of the TCA cycle in cellular metabolism. Examples of dysregulated genes included those involved in proliferation, adhesion, and the hypoxia pathway. Of interest, SDHB-silenced cells had a greater capacity to adhere to extracellular matrix components, including fibronectin and laminin, than control cells, thus suggesting a possible mechanism of tumor initiation. Although transient silencing of the HIF-1α transcription factor in SDHB-silenced cells had little effect on the expression of a subset of up-regulated genes, it partially reversed the adhesion phenotype to fibronectin, pointing to a potentially important role for HIF-1 in this process. [Cancer Res 2008;68(11):4058–67]
Transforming Growth Factor-β Activation Promotes Genetic Context–Dependent Invasion of Immortalized Melanocytes
Authors: Lo Roger S. , Witte Owen N.
Published: June 2008

Accumulation of distinct sets of genetic/epigenetic alterations is thought to contribute to stepwise progression of human cutaneous melanomas. We found evidence of frequent tumor cell autonomous transforming growth factor-β (TGF-β) signal activation in both premalignant and malignant stages of human cutaneous melanoma histogenesis and investigated its potential causative roles using human organotypic skin cultures. PTEN deficiency and Braf activation, two common coincident genetic alterations found in primary cutaneous melanomas, were first introduced into human melanocytes previously immortalized by the SV40 large T antigen and telomerase. These changes individually supported anchorage-independent growth and conferred benign, hyperplastic growth in a skin-like environment. In addition, PTEN deficiency combined with Braf activation together induced a melanoma in situ–like phenotype without dermal invasion. Further addition of cell autonomous TGF-β activation in the context of PTEN deficiency and Braf activation promoted dermal invasion in skin cultures without significantly promoting proliferation in vitro and in vivo. This proinvasive phenotype of cell autonomous TGF-β activation is genetic context–dependent, as hyperactivating the TGF-β type I receptor without PTEN deficiency and Braf activation failed to induce an invasive behavior. Evidence of genetic interactions among PTEN deficiency, Braf activation, and cell autonomous TGF-β activation shows that distinct stages of human melanoma are genetically tractable in the proper tissue architecture. [Cancer Res 2008;68(11):4248–57]
Phenotype-Specific CpG Island Methylation Events in a Murine Model of Prostate Cancer
Authors: Camoriano Marta , Morey Kinney Shannon R. , Moser Michael T. , Foster Barbara A. , Mohler James L. , Trump Donald L. , Karpf Adam R. , Smiraglia Dominic J.
Published: June 2008

Aberrant DNA methylation plays a significant role in nearly all human cancers and may contribute to disease progression to advanced phenotypes. Study of advanced prostate cancer phenotypes in the human disease is hampered by limited availability of tissues. We therefore took advantage of the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model to study whether three different phenotypes of TRAMP tumors (PRIM, late-stage primary tumors; AIP, androgen-independent primary tumors; and MET, metastases) displayed specific patterns of CpG island hypermethylation using Restriction Landmark Genomic Scanning. Each tumor phenotype displayed numerous hypermethylation events, with the most homogeneous methylation pattern in AIP and the most heterogeneous pattern in MET. Several loci displayed a phenotype-specific methylation pattern; the most striking pattern being loci methylated at high frequency in PRIM and AIP but rarely in MET. Examination of the mRNA expression of three genes, BC058385, Goosecoid, and Neurexin 2, which exhibited nonpromoter methylation, revealed increased expression associated with downstream methylation. Only methylated samples showed mRNA expression, in which tumor phenotype was a key factor determining the level of expression. The CpG island in the human orthologue of BC058385 was methylated in human AIP but not in primary androgen-stimulated prostate cancer or benign prostate. The clinical data show a proof-of-principle that the TRAMP model can be used to identify targets of aberrant CpG island methylation relevant to human disease. In conclusion, phenotype-specific hypermethylation events were associated with the overexpression of different genes and may provide new markers of prostate tumorigenesis. [Cancer Res 2008;68(11):4173–82]
Crucial Role of Interleukin-4 in the Survival of Colon Cancer Stem Cells
Authors: Francipane Maria Giovanna , Perez Alea Mileidys , Lombardo Ylenia , Todaro Matilde , Medema J.P. , Stassi Giorgio
Published: June 2008

Colon tumors may be maintained by a rare fraction of cancer stem-like cells (CSC) that express the cell surface marker CD133. Self-renewing CSCs exhibit relatively greater resistance to clinical cytotoxic therapies and recent work suggests that this resistance may be mediated in part by an autocrine response to the immune cytokine interleukin 4 (IL-4). Blocking IL-4 signaling can sensitize CSCs to apoptotic stimuli and increase the in vivo efficacy of cytotoxic therapy. These findings suggest that inhibitors of IL-4 signaling may offer a new therapeutic tool in colon carcinoma. [Cancer Res 2008;68(11):4022–5]
Involvement of Rac in Fenretinide-Induced Apoptosis
Authors: Kadara Humam , Tahara Eiji , Kim Hyun-Jung , Lotan Dafna , Myers Jeffrey , Lotan Reuben
Published: June 2008

The synthetic retinoid N-(4-hydroxyphenyl)retinamide (4HPR) has shown potential as a chemopreventive and therapeutic agent. The ability of 4HPR to enhance production of reactive oxygen species (ROS) leading to apoptosis has been suggested as a possible mechanism underlying these effects. We explored the possibility that ROS induction by 4HPR involves the small GTPase Ras-related C3 botulinum toxin substrate (Rac), a regulatory subunit of the NADPH oxidase complex. Rac was activated in human head and neck squamous cell carcinoma (HNSCC) cells as early as 5 minutes following 4HPR exposure. Moreover, inhibition of Rac activity or silencing of its expression by RNA interference decreased ROS generation in human head and neck, lung, and cervical cancer cells and murine melanoma cells. In HNSCC UMSCC-22B cells, this decrease correlated with reduction in apoptosis induction by 4HPR. Expression of a constitutive active mutant Rac increased basal and 4HPR-induced ROS generation and poly(ADP-ribose) polymerase cleavage. In addition, the metastatic DM14 cells exhibited higher Rac activation following 4HPR treatment compared with the primary Tu167-C2 cells. Furthermore, the metastatic cancer cells tested exhibited higher ROS generation and growth inhibition due to 4HPR exposure compared with their primary cancer cell counterparts. These findings show a preferential susceptibility of metastatic cells to the proapoptotic retinoid 4HPR through Rac activation and support the use of ROS-inducing agents such as 4HPR against metastatic cancer cells. [Cancer Res 2008;68(11):4416–23]
Histone Deacetylase Inhibitors Reverse SS18-SSX–Mediated Polycomb Silencing of the Tumor Suppressor Early Growth Response 1 in Synovial Sarcoma
Authors: Lubieniecka Joanna M. , de Bruijn Diederik R.H. , Su Le , van Dijk Anke H.A. , Subramanian Subbaya , van de Rijn Matt , Poulin Neal , van Kessel Ad Geurts , Nielsen Torsten O.
Published: June 2008

Synovial sarcoma is a soft tissue malignancy characterized by the fusion of SS18 to either SSX1, SSX2, or SSX4 genes. SS18 and SSX are transcriptional cofactors involved in activation and repression of gene transcription, respectively. SS18 interacts with SWI/SNF, whereas SSX associates with the polycomb chromatin remodeling complex. Thus, fusion of these two proteins brings together two opposing effects on gene expression and chromatin structure. Recent studies have shown that a significant number of genes are down-regulated by the SS18-SSX fusion protein and that the clinically applicable histone deacetylase (HDAC) inhibitor romidepsin inhibits synovial sarcoma growth. Therefore, we set out to identify direct targets of SS18-SSX among genes down-regulated in synovial sarcoma and investigated if romidepsin can specifically counteract SS18-SSX–mediated transcriptional dysregulation. Here, we report that the tumor suppressor early growth response 1 (EGR1) is repressed by the SS18-SSX protein through a direct association with the EGR1 promoter. This SS18-SSX binding correlates with trimethylation of Lys27 of histone H3 (H3K27-M3) and recruitment of polycomb group proteins to this promoter. In addition, we found that romidepsin treatment reverts these modifications and reactivates EGR1 expression in synovial sarcoma cell models. Our data implicate polycomb-mediated epigenetic gene repression as a mechanism of oncogenesis in synovial sarcoma. Furthermore, our work highlights a possible mechanism behind the efficacy of a clinically applicable HDAC inhibitor in synovial sarcoma treatment. [Cancer Res 2008;68(11):4303–10]
Carcinoma-Associated Fibroblast–Like Differentiation of Human Mesenchymal Stem Cells
Authors: Mishra Pravin J. , Mishra Prasun J. , Humeniuk Rita , Medina Daniel J. , Alexe Gabriela , Mesirov Jill P. , Ganesan Sridhar , Glod John W. , Banerjee Debabrata
Published: June 2008

Carcinoma-associated fibroblasts (CAF) have recently been implicated in important aspects of epithelial solid tumor biology, such as neoplastic progression, tumor growth, angiogenesis, and metastasis. However, neither the source of CAFs nor the differences between CAFs and fibroblasts from nonneoplastic tissue have been well defined. In this study, we show that human bone marrow–derived mesenchymal stem cells (hMSCs) exposed to tumor-conditioned medium (TCM) over a prolonged period of time assume a CAF-like myofibroblastic phenotype. More importantly, these cells exhibit functional properties of CAFs, including sustained expression of stromal-derived factor-1 (SDF-1) and the ability to promote tumor cell growth both in vitro and in an in vivo coimplantation model, and expression of myofibroblast markers, including α-smooth muscle actin and fibroblast surface protein. hMSCs induced to differentiate to a myofibroblast-like phenotype using 5-azacytidine do not promote tumor cell growth as efficiently as hMSCs cultured in TCM nor do they show increased SDF-1 expression. Furthermore, gene expression profiling revealed similarities between TCM-exposed hMSCs and CAFs. Taken together, these data suggest that hMSCs are a source of CAFs and can be used in the modeling of tumor-stroma interactions. To our knowledge, this is the first report showing that hMSCs become activated and resemble carcinoma-associated myofibroblasts on prolonged exposure to conditioned medium from MDAMB231 human breast cancer cells. [Cancer Res 2008;68(11):4331–9]
ECSA/DPPA2 is an Embryo-Cancer Antigen that Is Coexpressed with Cancer-Testis Antigens in Non–Small Cell Lung Cancer
Authors: John Thomas , Caballero Otavia L. , Svobodová Suzanne J. , Kong Alan , Chua Ramon , Browning Judy , Fortunato Sheila , Deb Siddhartha , Hsu Melinda , Gedye Craig A. , Davis Ian D. , Altorki Nasser , Simpson Andrew J. , Chen Yao-Tseng , Monk Marilyn , Cebon Jonathan S.
Published: June 2008

Purpose: Cancer cells recapitulate many behaviors of pluripotent embryonic cells such as unlimited proliferation, and the capacity to self-renew and to migrate. Embryo-cancer sequence A (ECSA), later named developmental pluripotency associated-2 (DPPA2), is an embryonic gene initially isolated from pluripotent human preimplantation embryos. We hypothesized that ECSA/DPPA2 would be quiescent in most normal tissues but expressed in cancers and may therefore be a useful target for immunotherapy.

Experimental Design: ECSA/DPPA2 expression was examined in a panel of normal and tumor tissue by reverse transcription PCR, quantitative real-time PCR, and immunohistochemistry. A panel of 110 non–small cell lung cancers (NSCLC) were further investigated for the presence of ECSA/DPPA2 transcripts and several cancer testis antigens (CTA). Sera from 104 patients were analyzed for spontaneous ECSA/DPPA2 antibody production by ELISA and Western blot.

Results: ECSA/DPPA2 transcripts were limited to normal testis, placenta, bone marrow, thymus, and kidney but expressed in a variety of tumors most notably in 30% of NSCLC. Enrichment for CTAs in ECSA/DPPA2-positive NSCLC was observed. Immunohistochemistry confirmed nuclear and cytoplasmic localization in subpopulations of cells with coexpression of the CTA MAGE-A3. Antibodies to recombinant ECSA/DPPA2 protein were detected in the sera of 4 of 104 patients with NSCLC but not in healthy controls.

Conclusions: The restricted expression in normal tissues, expression in tumors with coexpression of CTAs, and spontaneous immunogenicity indicate that ECSA/DPPA2 is a promising target for antigen-specific immunotherapy in NSCLC.
Prognostic Significance of Defective Mismatch Repair and BRAF V600E in Patients with Colon Cancer
Authors: French Amy J. , Sargent Daniel J. , Burgart Lawrence J. , Foster Nathan R. , Kabat Brian F. , Goldberg Richard , Shepherd Lois , Windschitl Harold E. , Thibodeau Stephen N.
Published: June 2008

Purpose: Colon tumors with defective DNA mismatch repair (dMMR) have a well-characterized phenotype and accounts for ∼15% to 20% of sporadic colon cancer as well as those colon cancer patients with Lynch syndrome. Although the presence of dMMR seems to be a favorable prognostic marker, data suggest that these patients do not respond as well to adjuvant chemotherapy.

Experimental Design: In this study, we examined the prognostic significance of tumor MMR deficiency and the presence of a specific mutation in BRAF (V600E) in a group of patients (n = 533) who participated in a randomized prospective clinical trial through the North Central Cancer Treatment Group.

Results: Tumors with dMMR were found to be associated with higher tumor grade (P = 0.001), proximal location (P < 0.0001), and improved overall and disease-free survival (P = 0.05 and 0.04, respectively). Among all cases examined, evaluation of the BRAF V600E mutation status revealed no statistically significant differences in either disease-free or overall survival. Patients were then grouped into four categories for further analysis: dMMR/BRAF(−), dMMR/BRAF(+), pMMR/BRAF(−), and pMMR/BRAF(+). The dMMR/BRAF(−) group had a significantly improved overall survival (5-year overall survival of 100% versus 73%, P = 0.002) compared with all others. The remaining three groups had very similar survival outcomes. An additional cohort of tumors previously classified as having dMMR were also tested for the BRAF V600E alteration. Results remained significant (P = 0.006) when the two groups were combined for analysis.

Conclusions: Overall, these data suggest that the underlying molecular etiology of those tumors having dMMR may influence the disease outcome in these patients.
Matrix metalloproteinase-9 Inhibition Down-Regulates Radiation-Induced Nuclear Factor-κB Activity Leading to Apoptosis in Breast Tumors
Authors: Kunigal Sateesh , Lakka Sajani S. , Joseph Pushpa , Estes Norman , Rao Jasti S.
Published: June 2008

Purpose: Novel strategies are needed to prevent the high mortality rates of several types of cancer. These high rates stem from tumor resistance to radiation therapy, which is thought to result from the induction of matrix metalloproteinases (MMP) and plasminogen activators. In the present study, we show that the modulation of MMP-9 expression, using adenoviral-mediated transfer of the antisense MMP-9 gene (MMP-9 adenoviral construct, Ad-MMP-9), affects breast cancer sensitivity to radiation.

Experimental Design: In the present study, we used antisense Ad-MMP-9 to down-regulate the expression of MMP-9 in MDA MB 231 breast cancer cell lines in vitro before irradiation and subsequently incubated cells in hypoxic condition. In vivo studies were done with orthotopic breast tumors, and radiosensitivity was evaluated both in vitro and in vivo.

Results: Ad-MMP-9 infection resulted in down-regulation of radiation-induced levels of hypoxia-inducible factor 1α and MMP-9 under hypoxic conditions in MDA MB 231 breast cancer cells. In addition, Ad-MMP-9, in combination with radiation, decreased levels of the transcription factors nuclear factor-κB and activator protein 1, both of which contribute to the radioresistance of breast tumors. Finally, the triggering of the Fas–Fas ligand apoptotic cascade, which resulted in the cleavage of PARP-1 and caspase-10, caspase-3, and caspase-7, signifies the efficiency of combined treatment of Ad-MMP-9 and radiation. Treatment with Ad-MMP-9 plus radiation completely regressed tumor growth in orthotopic breast cancer model.

Conclusions: In summary, integrating gene therapy (adenovirus-mediated inhibition of MMP-9) with radiotherapy could have a synergistic effect, thereby improving the survival of patients with breast cancer.
Mutant Epidermal Growth Factor Receptor in Benign, Borderline, and Malignant Ovarian Tumors
Authors: Steffensen Karina Dahl , Waldstrøm Marianne , Olsen Dorte Aalund , Corydon Thomas , Lorentzen Karen Axelgaard , Knudsen Hans Jørgen , Jeppesen Ulla , Brandslund Ivan , Jakobsen Anders
Published: June 2008

Purpose: Dysfunction of the epidermal growth factor (EGF) complex is essential to the growth and development of many human tumors. Overexpression of the EGF receptor (EGFR) is a characteristic finding in a considerable number of solid tumors and often signalizes poor prognosis. There is a major disagreement among researchers about both the frequency and possible clinical importance of EGFR overexpression in ovarian cancer. The type III variant of EGFR (EGFRvIII) is a mutant with a deletion. Contrary to the wild-type, it is constitutively active. EGFRvIII has not been found in normal tissue, and consequently, it is an attractive tumor-specific candidate for molecular targeted treatment. The literature dealing with this mutation in ovarian cancer has been very sparse.

Experimental Design: Tissue from 225 patients who underwent surgery for a pelvic mass was collected consecutively. The samples included 99 ovarian/peritoneal/tuba cancers, 17 ovarian borderline tumors, 66 benign ovarian tumors, 15 other cancer types, 24 normal ovarian biopsies, and 4 miscellaneous. The presence of EGFRvIII was investigated both by PCR analyses for EGFRvIII gene expression and with protein analysis by Western blots.

Results: None of the tissue samples was positive for the EGFRvIII mutation neither at the mRNA level nor at the protein level.

Conclusions: The EGFRvIII mutation seems to be very rare in ovarian tissue. Our data indicate that EGFRvIII is not a part of the malignant phenotype in ovarian cancer and should not be pursued as a therapeutic target for treatment of this disease.
Evaluation of the Pharmacodynamic Effects of MGCD0103 from Preclinical Models to Human Using a Novel HDAC Enzyme Assay
Authors: Bonfils Claire , Kalita Ann , Dubay Marja , Siu Lillian L. , Carducci Michael A. , Reid Gregory , Martell Robert E. , Besterman Jeffrey M. , Li Zuomei
Published: June 2008

Purpose: The pharmacodynamic properties of MGCD0103, an isotype-selective inhibitor of histone deacetylase (HDAC), were evaluated in preclinical models and patients with a novel whole-cell HDAC enzyme assay.

Experimental Design: Boc-Lys(ε-Ac)-AMC, a HDAC substrate with fluorescent readout, was found to be cell permeable and was used to monitor MGCD0103-mediated HDAC inhibition in cultured cancer cells in vitro, in peripheral WBC ex vivo, in mice in vivo, and in human patients.

Results: MGCD0103 inhibited HDAC activity in several human cancer cell lines in vitro and in human peripheral WBC ex vivo in a dose-dependent manner. Unlike suberoylanilide hydroxamic acid, the HDAC inhibitory activity of MGCD0103 was time dependent and sustained for at least 24 hours following drug removal in peripheral WBC ex vivo. Inhibitory activity of MGCD0103 was sustained for at least 8 hours in vivo in mice and 48 hours in patients with solid tumors. HDAC inhibitory activity of MGCD0103 in peripheral WBC correlated with induction of histone acetylation in blood and in implanted tumors in mice. In cancer patients, sustained pharmacodynamic effect of MGCD0103 was visualized only by dose-dependent enzyme inhibition in peripheral WBC but not by histone acetylation analysis.

Conclusions: This study shows that MGCD0103 has sustained pharmacodynamic effects that can be monitored both in vitro and in vivo with a cell-based HDAC enzyme assay.
AP1-Dependent Galectin-1 Expression Delineates Classical Hodgkin and Anaplastic Large Cell Lymphomas from Other Lymphoid Malignancies with Shared Molecular Features
Authors: Rodig Scott J. , Ouyang Jing , Juszczynski Przemyslaw , Currie Treeve , Law Kenneth , Neuberg Donna S. , Rabinovich Gabriel A. , Shipp Margaret A. , Kutok Jeffery L.
Published: June 2008

Purpose: Galectin-1 (Gal1) is an immunomodulatory glycan-binding protein regulated by an AP1-dependent enhancer in Hodgkin Reed-Sternberg cells. We recently found that Reed-Sternberg cell Gal1 promotes the immunosuppressive T-helper 2/T-regulatory cell–skewed microenvironment in classical Hodgkin lymphoma (cHL). We sought to investigate whether the coordinate expression of activated AP1 pathway components and Gal1 serves as a diagnostic signature of cHL. In addition, because there are common signaling and survival pathways in cHL and additional non–Hodgkin lymphomas, we also evaluated whether the AP1/Gal1 signature is shared by other molecularly or morphologically related lymphomas.

Experimental Design: We evaluated 225 cases of primary cHL and non–Hodgkin lymphoma for evidence of a functional AP1/Gal1 signature by immunohistochemical techniques.

Results: Gal1 is selectively expressed by malignant Reed-Sternberg cells in >90% of primary cHLs, and Gal1 expression is concordant with the activated AP1 component, c-Jun. In contrast, diffuse large B-cell lymphoma, primary mediastinal large B-cell lymphoma, and another Hodgkin-related entity, nodular lymphocyte–predominant Hodgkin lymphoma, do not express Gal1. However, anaplastic large cell lymphoma (ALCL), consistently expresses both Gal1 and its transcriptional regulator, c-Jun. The presence of activated c-Jun, indicative of functional AP1 activity, was confirmed by phospho-c-Jun immunostaining in cHL and ALCL.

Conclusions: These findings establish a functional AP1 signature that includes Gal1 expression in cHL and ALCL and suggests a common mechanism for tumor immunotolerance in these diseases. In addition, the combination of Gal1 and c-Jun serve as diagnostic biomarkers that delineate cHL and ALCL from other lymphomas with shared morphologic and/or molecular features.
Gly82Ser Polymorphism of the Receptor for Advanced Glycation End Products Is Associated with an Increased Risk of Gastric Cancer in a Chinese Population
Authors: Gu Haijuan , Yang Li , Sun Qingmin , Zhou Bo , Tang Naping , Cong Rihong , Zeng Ying , Wang Bin
Published: June 2008

Purpose: It has been shown that the expression of the receptor for advanced glycation end products (RAGE) is closely associated with invasion and metastasis in gastric cancer. A Gly82Ser polymorphism in exon 3 of RAGE gene was identified and thought to have an effect on the functions of its protein. Therefore, the goal of the present study was to investigate whether the polymorphism is involved in the development or progression of gastric cancer.

Experimental Design: In the hospital-based case-control study, the RAGE genotypes were determined using PCR-RFLP in 566 individuals (283 gastric cancer patients and 283 age- and sex-matched controls).

Results: The distribution of genotype was significantly different between cases and controls (P = 0.038). Compared with the wild-type 82Gly/Gly carriers, subjects with the variant genotypes (82Gly/Ser and 82Ser/Ser) had a significantly higher risk of gastric cancer (adjusted odds ratio, 1.47; 95% confidence interval, 1.05-2.06). Moreover, the elevated gastric cancer risk was especially evident in younger individuals (ages ≤58 years), nonsmokers, and rural subjects. Further analyses revealed that the variant genotypes were associated with adjacent organ invasion in the subanalysis of gastric cancer patients.

Conclusions: Our findings indicate that the RAGE Gly82Ser polymorphism may confer not only an increased risk of gastric cancer but also with invasion of gastric cancer in the Chinese population.
Genetic Polymorphism in EGF Is Associated with Prostate Cancer Aggressiveness and Progression-Free Interval in Androgen Blockade–Treated Patients
Authors: Teixeira Ana L. , Ribeiro Ricardo , Cardoso Diana , Pinto Daniela , Lobo Francisco , Fraga Avelino , Pina Francisco , Calais-da-Silva Fernando , Medeiros Rui
Published: June 2008

Purpose: Most prostate cancer patients develop resistance to androgen deprivation treatment, resulting in hormone resistance. Epidermal growth factor (EGF) activates several pro-oncogenic intracellular pathways inducing proliferation, differentiation, and tumorigenesis in epithelial cells. The EGF-EGF receptor pathway seems to be especially relevant in hormone-resistant prostate cancer stage. A single nucleotide polymorphism G>A in +61 locus of EGF gene has been described, in which A homozygous carriers express significantly less EGF protein compared with G allele carriers. Our purpose was to investigate the potential prognostic and predictive role of EGF functional genetic variant +61 G>A in prostate cancer patients submitted to androgen blockade therapy (ABT).

Experimental Design: We conducted a case-control study in prostate cancer patients treated with ABT (n = 123) and in healthy controls without evidence of cancer (n = 152). Cumulatively, a follow-up study (median follow-up, 37 months) was undertaken to evaluate response to ABT therapy in prostate cancer patients. EGF +61 G>A genotypes were detected by PCR-RFLP.

Results: We found increased risk in G carriers, after age-adjusted regression analysis, for being diagnosed with Gleason ≥7 and with metastatic disease compared with control group (CG; age-adjusted odds ratio, 3.37, P = 0.004 and age-adjusted odds ratio, 2.61, P = 0.043, respectively). Kaplan-Meier survival analysis and log-rank test showed an influence of EGF +61 G>A polymorphism in time to relapse during ABT (P = 0.018).

Conclusions: EGF functional polymorphism may contribute to earlier relapse in ABT patients, supporting the involvement of EGF as an alternative pathway in hormone-resistant prostatic tumors. Furthermore, our results lend support to EGF-EGF receptor pathway as an additional therapeutic target during hormonal treatment.