bluuebunny/crossref_metadata_2025 huggingface dataset:
Material Removal in WEDM of PCD Blanks
Authors: Kozak J. , Rajurkar K. P. , Wang S. Z.
Published: April 2008

Polycrystalline diamond (PCD) tools are now widely used in machining a large variety of advanced materials. However, the manufacture of PCD tool blanks is not an economical and efficient process. The shaping of PCD blanks with conventional machining methods (such as grinding), is a long, labor-intensive and costly process. Wire electric discharge machining (WEDM) promises to be an effective and economical technique for the production of tools from PCD blanks. However, a knowledge base for wire electrical discharge machining of PCD blanks needs comprehensive investigations into the proper parameter setting, metal removal mechanisms, and surface integrity of machined blanks. This paper presents the results of experimental and theoretical investigations of the influence of discharge frequency and discharge energy on the material removal rate of WEDM of PCD blanks. The mechanism of removing diamond grains from the matrix during electrical erosion is also discussed on the basis of thermal stresses between the diamond grain and cobalt phase.
A Contact Point Method for the Design of Form Cutters for Helical Gears
Authors: Xiao D. C. , Lee C.
Published: April 2008

This article introduces a method to calculate contours of form cutters for machining helical gears from given gear tooth profiles. It is essential to find a relationship between the cutter contour and the gear profile in order to carry out the calculation. The method introduced in this article uses contact points between the cutter rotary surface and the gear tooth surface to establish the relationship. A minimum distance principle is applied. Equations for the calculation are derived and an example is given.
Evaluation of the Effect of High Speed Machining on Tapping
Authors: Agapiou J. S.
Published: April 2008

This paper summarizes tapping characteristics at speeds as high as 9,000 rpm (180 m/min surface speed) as compared to traditional tapping done at speeds from 500 to 1,500 rpm (20–30 m/min). High speed tapping was achieved by synchronizing the spindle rotation and the feed motion of a specially built machine at extremely high speeds and acceleration/deceleration rates. This investigation analyzes the performance of roll and cut tap geometries in the high speed tapping of 319 aluminum. The torque required by the different tap geometries at several speeds and percent threads combination is evaluated. The relationship between pretapped hole diameter and minor diameter of the thread and the estimation of percent thread are analyzed. The thread quality generated at high speeds is also evaluated. It is shown that the cutting speed does not affect the steady state torque and the shear strength. The torque for roll forming taps is higher than that for cut taps. The shear strength of roll forming threads increased with percent thread.
Activities of Clindamycin, Daptomycin, Doxycycline, Linezolid, Trimethoprim-Sulfamethoxazole, and Vancomycin against Community-Associated Methicillin-Resistant
Staphylococcus aureus
with Inducible Clindamycin Resistance in Murine Thigh Infection and In Vitro Pharmacodynamic Models
Authors: LaPlante Kerry L. , Leonard Steven N. , Andes David R. , Craig William A. , Rybak Michael J.
Published: April 2008

Controversy exists about the most effective treatment options for community-associated methicillin-resistant
Staphylococcus aureus
(CA-MRSA) and about the ability of these strains to develop inducible resistance to clindamycin during therapy. Using both in vitro pharmacodynamic and murine thigh infection models, we evaluated and compared several antimicrobial compounds against CA-MRSA. Strains with inducible macrolide lincosamide-streptogramin type B (iMLS
B
) resistance and strains in which resistance was noninducible were evaluated. Two levels of inocula (10
5
and 10
7
) were evaluated for clindamycin activity in the in vivo model. In both models, the antimicrobial evaluation was performed in triplicate, and bacterial quantification occurred over 72 h, with drug doses that were designed to simulate the free drug area-under-the-concentration-time curve values (
f
AUCs) obtained from human samples. When the activity of clindamycin against the iMLS
B
strains was evaluated, constitutive resistance was noted at 24 h (MIC of >256), and failure was noted at an inoculum of ≥10
6
in the in vivo models. However, at a low inoculum (10
5
) in the murine thigh-infection model, clindamycin demonstrated modest activity, reducing the CFU/thigh count for clindamycin resistance-inducible strains at 72 h (0.45 to 1.3 logs). Overall, administration of daptomycin followed by vancomycin demonstrated the most significant kill against all strains in both models. Against the clindamycin noninducible strain, clindamycin and doxycycline demonstrated significant kill. Doxycycline, linezolid, and trimethoprim-sulfamethoxazide (not run in the murine model) demonstrated bacteriostatic activity against clindamycin resistance-inducible isolates. This study demonstrates that clindamycin's activity against the iMLS
B
strains tested is partially impacted by inoculum size. At present, there are several alternatives that appear promising for treating clindamycin resistance-inducible strains of CA-MRSA.
β-Hydroxybutyrate Abrogates Formation of Bovine Neutrophil Extracellular Traps and Bactericidal Activity against Mammary PathogenicEscherichia coli
Authors: Grinberg Navit , Elazar Sharon , Rosenshine Ilan , Shpigel Nahum Y.
Published: April 2008

Escherichia coliis an important bacterial species isolated from bovine mastitis. The rate of neutrophil recruitment into the mammary gland and their bactericidal activity largely affect the severity and outcome of the disease. Ketosis is a common metabolic disease, and affected dairy cows are known to have increased risk for mastitis and other infectious conditions. The disease is associated with high blood and milk levels of β-hydroxybutyrate (BHBA), previously shown to negatively affect neutrophil function by unknown mechanisms. We show here that the mammary pathogenicE. colistrain P4 activates normal bovine neutrophils to form neutrophil extracellular traps (NETs), which are highly bactericidal against this organism. Preincubation of these neutrophils with increasing concentrations (0.1 to 8 mmol/liter) of BHBA caused a fivefold decrease ofE. coliP4 phagocytosis, though intracellular killing was unaffected. Furthermore, BHBA caused a 10-fold decrease in the NETs formed byE. coliP4-activated neutrophils and a similar decrease in NET bactericidal activity against this organism. These negative effects of BHBA on bovine neutrophils might explain the increased susceptibility of ketotic cows to mastitis and other infectious conditions.
Initial Delay in the Immune Response to
Francisella tularensis
Is Followed by Hypercytokinemia Characteristic of Severe Sepsis and Correlating with Upregulation and Release of Damage-Associated Molecular Patterns
Authors: Mares Chris A. , Ojeda Sandra S. , Morris Elizabeth G. , Li Qun , Teale Judy M.
Published: April 2008

“
Francisella tularensis
subsp.
novicida
” intranasal infection causes a rapid pneumonia in mice with mortality at 4 to 6 days with a low dose of bacteria (10
2
bacteria). The short time to death suggests that there is a failure of the innate immune response. As the neutrophil is often the first cell type to infiltrate sites of infection, we focused on the emigration of neutrophils in this infection, as well as cytokines involved in their recruitment. The results indicated that there was a significant delay in the influx of neutrophils into the bronchoalveolar lavage fluid of
F. tularensis
subsp.
novicida
-infected mice. The delay in neutrophil recruitment in
F. tularensis
subsp.
novicida
-infected mice correlated with a delay in the upregulation of multiple proinflammatory cytokines and chemokines, as well as a delay in caspase-1 activation. Strikingly, the initial delay in the upregulation of cytokines through 1 day postinfection was followed by profound upregulation of multiple cytokines and chemokines to levels consistent with hypercytokinemia described for severe sepsis. This finding was further supported by a bacteremia and the cellular relocalization and release of high-mobility group box-1 and S100A9, both of which are damage-associated molecular pattern molecules and are known to be mediators of severe sepsis.
Fas/CD95-Mediated Apoptosis of Type II Cells Is Blocked byToxoplasma gondiiPrimarily via Interference with the Mitochondrial Amplification Loop
Authors: Hippe Diana , Lytovchenko Oleksandr , Schmitz Ingo , Lüder Carsten G. K.
Published: April 2008

The intracellular protozoanToxoplasma gondiiinduces persistent infections in various hosts and is an important opportunistic pathogen of humans with immature or deficient immune responses. The ability to survive intracellularly largely depends on the blocking of different proapoptotic signaling cascades of its host cell. Fas/CD95 triggers an apoptotic cascade that is crucial for immunity and the outcome of infectious diseases. We have determined the mechanism by whichT. gondiicounteracts death receptor-mediated cell death in type II cells that transduce Fas/CD95 ligation via caspase 8-mediated activation of the mitochondrial amplification loop. The results showed that infection withT. gondiisignificantly reduced Fas/CD95-triggered apoptosis in HeLa cells by inhibiting the activities of initiator caspases 8 and 9 and effector caspase 3/7. Parasitic infection dose dependently diminished cleavage of caspase 8, the BH3-only protein Bid, and the downstream caspases 9 and 3. Importantly, interference with Fas/CD95-triggered caspase 8 and caspase 3/7 activities after parasitic infection was largely dependent on the presence of caspase 9. Within the mitochondrial amplification loop,T. gondiisignificantly inhibited the Fas/CD95-triggered release of cytochromecinto the host cell cytosol. These results indicate thatT. gondiiinhibits Fas/CD95-mediated apoptosis in type II cells primarily by decreasing the apoptogenic function of mitochondria.
Leaf phenology as an optimal strategy for carbon gain in plants
Authors: Kikuzawa K.
Published: April 2008

Since leaves are essentially energy-gaining organs, the arrangement of leaves in time (leaf phenology) and in space (canopy architecture) in both seasonal and nonseasonal environments can be viewed as a central element in plant strategies for carbon gain. Interrelationships among leaf longevity, leaf habit, and leaf-emergence pattern together with shoot architecture affect plant productivity. Leaf longevity is shown to maximize carbon gain through three parameters: leaf photosynthetic rate, the decrease in photosynthetic rate with leaf age, and the initial construction costs of the leaf. This theoretical approach has been extended to seasonal environments and effectively simulated the geographical pattern of leaf habits. To avoid self-shading, plants adopt two alternative modes of leaf emergence. One is successive leaf emergence, in which plants expand one leaf at a time on a shoot; this unshaded leaf utilizes full sunlight and is only replaced by a second leaf when its photosynthetic ability declines. Plants with successive leaf emergence attain high production and have straight shoots with multilayered canopy architecture. The alternative is simultaneous leaf emergence on shoots inclined to minimize self-shading through a monolayered canopy architecture. By the inclination of the shoot, each leaf on the shoot can receive sufficient light. Plants with simultaneous leaf emergence utilize the entire growing period effectively. Taken together and in the context of shoot and canopy architecture these interrelationships among leaf longevity, habit, and emergence pattern provide the basis for a synthetic theory of leaf phenology. Key words: leaf phenology, leaf longevity, leaf emergence, evergreen, deciduous habit.
A light and electron microscopic study of mitosis in the clamp connection ofAuricularia auricula-judae
Authors: Lü Haisheng , McLaughlin David J.
Published: April 2008

Nuclear behavior and mitotic division in living and fixed somatic hyphae of Auricularia auricula-judae were studied with phase-contrast, fluorescence, and electron microscopy to clarify the process of mitosis in Auriculariales sensu stricto for cytological and phylogenetic analysis. Both conventional chemical fixation and freeze-substitution methods were employed for electron microscopic analysis. Mitotic division began when one of the two nuclei was moving into the clamp and lasted about 12 – 18 min. The spindle pole body had an electron-opaque central core surrounded by an electron-transparent zone from prometaphase to anaphase. The spindle changed the orientation of its long axis from a position parallel to the long axis of the clamp or hypha in prometaphase, to an oblique position in early metaphase, and finally to a parallel position again in midmetaphase. The nuclear envelope was disrupted in prometaphase to early metaphase and showed discontinuity at both polar and central regions in late anaphase; however, in metaphase it was intact with polar fenestrations. Nuclear division in the dikaryotic hypha was asynchronous. The data obtained from mitosis in A. auricula-judae support a close relationship of Auriculariales s.str. with homobasidiomycetes. The phylogenetic significance of the nuclear division characters is analyzed. Key words: Auricularia auricula-judae, electron microscopy, light microscopy, mitosis, phylogeny.
Quantitative Use of Stable Carbon Isotope Analysis to Determine the Trophic Base of Invertebrate Communities in a Boreal Forest Lotic System
Authors: Junger Michel , Planas Dolors
Published: April 2008

Stable carbon isotope mixing models were combined with inventories of macroinvertebrate biomass to quantitatively assess the trophic base of three contrasting lotic ecosystems in a boreal forest drainage system in spring/early summer. In a second-order partially shaded stream and in a fourth-order unshaded river, 13C/12C ratios of autochthonous and allochthonous food sources were distinct, allowing the use of isotopic mixing equations to calculate the relative contribution of both sources to consumer biomasses. In a small shaded lake outlet, isotopic compositions of autochthonous and allochthonous carbon were similar but distinct from that of lake seston which was relatively 13C depleted. The mixing model for the lake outlet thus discriminated between feeding on lake-derived food and on combined autochthonous and allochthonous food sources. Percent food utilization calculated for each invertebrate taxon by a site-specific mixing equation was weighted by biomass data to define the food bases of primary consumer communities. The food base was clearly dominated by lacustrine inputs (which represented >80% of the total food base) in the lake outlet, by allochthonous inputs (≈75%) in the second-order site, and by autochthonous production (≈60%) in the fourth-order site.
Turbidity and Temperature Effects on Oxygen Consumption in the Zebra Mussel (Dreissena polymorpha)
Authors: Alexander Jr. James E. , Thorp James H. , Fell Ronald D.
Published: April 2008

The effects of acute exposure to suspended inorganic sediment (bentonite clay) on oxygen consumption rates of the zebra mussel (Dreissena polymorpha) were examined to estimate their maintenance costs for colonizing the Ohio River. Adult D. polymorpha were acclimated to 10, 18, or 26 °C for 2 wk (10 replicate groups for each acclimation temperature) and respiration was measured in a closed recirculating system using oxygen electrode probes. Each replicate group of mussels was tested at their acclimation temperature under five turbidity levels: 0 (clear water), 5, 20, 80, and 160 NTU (nephelometric turbidity units). Respiration rates were significantly affected by acclimation temperature (direct relationship) and turbidity (inverse relationship, which leveled off with increasing turbidity). Warmer-acclimated animals showed a more dramatic drop in oxygen consumption with increasing turbidity, and all size-classes were equally affected by turbidity. Our results suggest that the normal ranges of temperatures and turbidity levels in the Ohio River may depress growth rates of adult D. polymorpha by increasing maintenance costs but probably will not by themselves prevent establishment of viable populations in this river.
Manganese Reduction in Oneida Lake, New York: Estimates of Spatial and Temporal Manganese Flux
Authors: Aguilar Carmen , Nealson Kenneth H.
Published: April 2008

Manganese is a very reactive redox metal, which exhibits a strong annual cycle in Oneida Lake, New York. Different methods were used to measure Mn(II) fluxes from the sediments throughout the year: (1) estimates based on changes in porewater profiles, (2) direct measurements with in situ flux chambers, (3) concentration gradients into the sediment–water interface in laboratory-incubated cores, and (4) changes in hypolimnetic manganese inventories during stratification. In deep basins of the lake, high rates of Mn(IV) reduction, up to 2.1 mmol∙m−2∙d−1, were observed during the summer and early fall, with little reduction taking place during the rest of the year. In the shallow areas of the lake, where ferromanganese nodules and crusts are commonly found, there was little or no reduction throughout the year. The manganese cycle is tightly coupled to the carbon cycle, based on our findings, and has a significant role in the oxidation of organic carbon in the lake, derived from the high photosynthetic production and the bio-mass that collapses and reaches the sediment–water interface. Preliminary experiments with poisoned controls suggest that Mn(IV) reduction is the result of a combination of biological and abiological processes.
Pattern and Process in Ecological Systems: A Step in the Development of a General Ecological Theory
Authors: Johnson Lionel
Published: April 2008

The dominant fish populations in undisturbed arctic lakes are characterized as being in a state of "least specific dissipation": the greatest biomass attainable for a given energy input. A survey of autonomous ecosystems in various parts of the world indicated that this pattern is widespread. It is concluded that ecosystems are formed at the point of intersection of two established physical principles: the "principle of most action" (≈least dissipation or conservation of free energy) and the "principle of least action". "Action" is defined as the product of energy times time (joule-seconds). The trend to "most action" necessitates deceleration of energy flow: "least action" accelerates energy flow. For an ecosystem to survive over ecological time, the principle of most action must override the principle of least action. In that different species of organism have different capacities to conserve free energy (increase action), a hierarchy is formed locally in which action increases at each hierarchical level. Over the long term, as a result of genetic instability, both principles induce change, but the principle of least action dominates system behaviour causing increasingly rapid energy dissipation. Evolution is the resultant of these two countervailing forces.
LOW REGULARITY WELL-POSEDNESS OF THE DIRAC–KLEIN–GORDON EQUATIONS IN ONE SPACE DIMENSION
Authors: SELBERG SIGMUND , TESFAHUN ACHENEF
Published: April 2008

We extend recent results of Machihara and Pecher on low regularity well-posedness of the Dirac–Klein–Gordon (DKG) system in one dimension. Our proof, like that of Pecher, relies on the null structure of DKG, recently completed by D'Ancona, Foschi and Selberg, but we show that in 1d the argument can be simplified by modifying the choice of projections for the Dirac operator. We also show that the result is best possible up to endpoint cases, if one iterates in Bourgain–Klainerman–Machedon spaces.
NONEXISTENCE RESULTS FOR BIHARMONIC BOUNDARY VALUE PROBLEMS WITH SUPERCRITICAL GROWTH
Authors: KHENISSY SAÏMA , YE DONG
Published: April 2008

We consider here the following biharmonic equations: [Formula: see text] We prove that for N ≥ 6 (resp. for N ≥ 10), there exist topologically nontrivial, smooth bounded domains Ω ⊂ ℝN and suitable supercritical nonlinearities f such that there does not exist any nontrivial solution. These results are similar to some of those proved by Passaseo (see [11, 12]) for the Laplacian case.
EXISTENCE RESULT FOR THE MEAN FIELD PROBLEM ON RIEMANN SURFACES OF ALL GENUSES
Authors: DJADLI ZINDINE
Published: April 2008

Given a compact surface (Σ,g), we prove the existence of a solution for the mean field equation on Σ. The problem consists of solving a second-order nonlinear elliptic equation with variational structure and exponential nonlinearity. Since the corresponding Euler functional is, in general, unbounded from above and from below, we employ topological methods and min-max schemes. Our result generalizes previous results by Lin [11], by Chen and Lin [6] and by Ding et al. [8]. The main point here is that, by taking values of the parameter greater than 8π, we make no assumption on the topology of the surface.
Program slicing under UML scenario models
Authors: Qian Ju , Xu Baowen
Published: April 2008

Slicing is an important decomposition technique for program understanding. However, traditional slicing methods tend to produce too large slices for human inspection as modern programs are often huge and static program analyses are hard to be precise enough. According to the state-of-the art research and our own experience, we believe a possible solution to such problem could be incorporating UML scenario models into program slicing. This paper presents a detail discussion on how scenarios can benefit slicing relevant program analyses and proposes a general scenario specified program slicing method. The analyses indicate that scenario specified program slicing may obtain smaller slices for program understanding.
Protecting critical infrastructure: implementing integration and expanding education
Authors: Martinez David A.
Published: April 2008

The tenuous network of interconnected data that supports our nation's critical infrastructure has been built up, computer by computer, over only the last few decades. From punch cards to the supercomputers constructed by pioneers in today's fields, computers have been controlling our nation's critical sectors nearly every step of the way. As designers of today's critical systems gravitate slowly towards systems that require less human oversight than ever before, the vulnerability of the networks that control our electricity systems, water supply, and banking services also continues to increase. In recent control system security reviews, the Departments of Energy and Homeland Security (DHS) hired experts from Idaho National Labs who found that not only do "all of the evaluated systems suffer from high-impact security vulnerabilities that could be exploited by a low-skill-level attacker," but "in currently deployed systems, enhanced security controls cannot easily be implemented while still assuring basic system functionality" (Turner). While the federal government has attempted on several occasions to outline its strategy to implement cybersecurity policies, its defining statement on the issue is in the form of the National Infrastructure Protection Plan (NIPP). Even then, these government documents mean little if neither government nor private agencies implement them in their respective fields.
Data and web management research at Politecnico di Milano
Authors: Ceri Stefano , Bolchini Cristiana , Braga Daniele , Brambilla Marco , Campi Alessandro , Comai Sara , Fraternali Piero , Lanzi Pier Luca , Masseroli Marco , Matera Maristella , Negri Mauro , Pelagatti Giuseppe , Pozzi Giuseppe , Quintarelli Elisa , Schreiber Fabio A. , Tanca Letizia
Published: April 2008

Research in data management at Politecnico di Milano has a long and solid tradition; forefront books on distributed databases, conceptual database design, logical databases, and active databases contributed to shape the foundations of this discipline in the last two decades. Historically, our work has addressed both all aspects of innovation in the technology of modern data management systems and the consequent support of design methods and tools.
Report on the Fourth International Workshop on Data Management for Sensor Networks (DMSN 2007)
Authors: Balazinska Magdalena , Deshpande Amol , Labrinidis Alexandros , Luo Qiong , Madden Samuel , Yang Jun
Published: April 2008

Sensor networks enable an unprecedented level of access to the physical world, and hold tremendous potential to revolutionize many application domains. Research on sensor networks spans many areas of computer science, and there are now major conferences, e.g.,
IPSN
and
SenSys
, devoted to sensor networks. However, there is no focused forum for discussion of early and innovative work on data management in sensor networks.
The International Workshop on Data Management for Sensor Networks (DMSN)
, inaugurated in 2004, aims to fill this significant gap in the database and sensor network communities.
Report on the First VLDB Workshop on Management of Uncertain Data (MUD)
Authors: de Keijzer Ander , van Keulen Maurice , Dekhtyar Alex
Published: April 2008

On Monday September 24

th

, we organized the first international VLDB workshop on Management of Uncertain Data [dKvKD07]. The idea of this workshop arose a year earlier at the Twente Data Management Workshop on Uncertainty in Databases [dKvK06]. The TDM is a bi-annual workshop organized by the Database group of the University of Twente, for which each time a different topic is chosen. The participants of TDM 2006 were enthusiastic about the topic "Uncertainty in Databases" and strongly expressed the wish for a follow-up co-located with an international conference. To fulfill this wish, we organized the MUD-workshop at VLDB.
Dimethyl amiloride improves glucose homeostasis in mouse models of type 2 diabetes
Authors: Gunawardana Subhadra C. , Head W. Steven , Piston David W.
Published: April 2008

Dimethyl amiloride (DMA) enhances insulin secretion in the pancreatic β-cell. DMA also enhances time-dependent potentiation (TDP) and enables TDP to occur in situations where it is normally absent. As we have demonstrated before, these effects are mediated in part through inhibition of neuronal nitric oxide synthase (nNOS), resulting in increased availability of arginine. Thus both DMA and arginine have the potential to correct the secretory defect in diabetes by enabling or enhancing TDP. In the current study we have demonstrated the ability of these agents to improve blood glucose homeostasis in three mouse models of type 2 diabetes. The pattern of TDP under different conditions indicates that inhibition of NOS is not the only mechanism through which DMA exerts its positive effects. Thus we also have explored another possible mechanism through which DMA enables/enhances TDP, via the activation of mitochondrial α-ketoglutarate dehydrogenase.
Effects of c-MYC activation on glucose stimulus-secretion coupling events in mouse pancreatic islets
Authors: Pascal Séverine M. A. , Guiot Yves , Pelengaris Stella , Khan Michael , Jonas Jean-Christophe
Published: April 2008

Alteration of pancreatic β-cell survival and Preproinsulin gene expression by prolonged hyperglycemia may result from increased c-MYC expression. However, it is unclear whether c-MYC effects on β-cell function are compatible with its proposed role in glucotoxicity. We therefore tested the effects of short-term c-MYC activation on key β-cell stimulus-secretion coupling events in islets isolated from mice expressing a tamoxifen-switchable form of c-MYC in β-cells (MycER) and their wild-type littermates. Tamoxifen treatment of wild-type islets did not affect their cell survival, Preproinsulin gene expression, and glucose stimulus-secretion coupling. In contrast, tamoxifen-mediated c-MYC activation for 2–3 days triggered cell apoptosis and decreased Preproinsulin gene expression in MycER islets. These effects were accompanied by mitochondrial membrane hyperpolarization at all glucose concentrations, a higher resting intracellular calcium concentration ([Ca2+]i), and lower glucose-induced [Ca2+]i rise and islet insulin content, leading to a strong reduction of glucose-induced insulin secretion. Compared with these effects, 1-wk culture in 30 mmol/l glucose increased the islet sensitivity to glucose stimulation without reducing the maximal glucose effectiveness or the insulin content. In contrast, overnight exposure to a low H2O2 concentration increased the islet resting [Ca2+]i and reduced the amplitude of the maximal glucose response as in tamoxifen-treated MycER islets. In conclusion, c-MYC activation rapidly stimulates apoptosis, reduces Preproinsulin gene expression and insulin content, and triggers functional alterations of β-cells that are better mimicked by overnight exposure to a low H2O2 concentration than by prolonged culture in high glucose.
Peroxisome Proliferator-Activated Receptor γ–Mediated Up-regulation of Syndecan-1 by n-3 Fatty Acids Promotes Apoptosis of Human Breast Cancer Cells
Authors: Sun Haiguo , Berquin Isabelle M. , Owens Rick T. , O'Flaherty Joseph T. , Edwards Iris J.
Published: April 2008

Diets enriched in n-3 polyunsaturated fatty acids (n-3 PUFA) may protect against breast cancer but biochemical mechanisms are unclear. Our studies showed that the n-3 fatty acid docosahexaenoic acid (DHA) up-regulated syndecan-1 (SDC-1) in human breast cancer cells, and we tested the hypothesis that DHA-mediated up-regulation of SDC-1 induces apoptosis. DHA was delivered to MCF-7 cells by n-3 PUFA–enriched low-density lipoproteins (LDL) or by albumin in the presence or absence of SDC-1 small interfering RNA. The n-3 PUFA induced apoptosis, which was blocked by SDC-1 silencing. We also confirmed that SDC-1 up-regulation and apoptosis promotion by n-3 PUFA was mediated by peroxisome proliferator-activated receptor γ (PPARγ). Using a luciferase gene driven by either a PPAR response element or a DR-1 site present in the SDC-1 promoter, reporter activities were enhanced by n-3 LDL, DHA, and PPARγ agonist, whereas activity of a luciferase gene placed downstream of a mutant DR-1 site was unresponsive. Cotransfection with dominant-negative PPARγ DNA eliminated the increase in luciferase activity. These data provide strong evidence that SDC-1 is a molecular target of n-3 PUFA in human breast cancer cells through activation of PPARγ and that n-3 PUFA–induced apoptosis is mediated by SDC-1. This provides a novel mechanism for the chemopreventive effects of n-3 PUFA in breast cancer. [Cancer Res 2008;68(8):2912–9]
BH3 Mimetic ABT-737 Potentiates TRAIL-Mediated Apoptotic Signaling by Unsequestering Bim and Bak in Human Pancreatic Cancer Cells
Authors: Huang Shengbing , Sinicrope Frank A.
Published: April 2008

Tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) has been shown to induce mitochondrial apoptotic signaling that can be negatively regulated by prosurvival Bcl-2 proteins. ABT-737 is a small-molecule BH3 mimetic that binds to and antagonizes Bcl-2/Bcl-xL but not Mcl-1. We show that ABT-737 can synergistically enhance TRAIL-mediated cytotoxicity in human pancreatic cancer cell lines. ABT-737 was shown to enhance TRAIL-induced apoptosis as shown by DNA fragmentation, activation of caspase-8 and Bid, and cleavage of caspase-3 and poly(ADP-ribose) polymerase. A Bax conformational change induced by TRAIL was enhanced by ABT-737. ABT-737 disrupted the interaction of Bak with Bcl-xL in both cell lines. Furthermore, ABT-737 untethered the proapoptotic BH3-only protein Bim from its sequestration by Bcl-xL or Bcl-2. Bim small hairpin RNA (shRNA) was shown to attenuate caspase-3 cleavage and to reduce the cytotoxic effects of TRAIL plus ABT-737 compared with shRNA control cells. Finally, Mcl-1 shRNA potentiated caspase-3 cleavage by ABT-737 and enhanced its cytotoxic effects. Taken together, ABT-737 augments TRAIL-induced cell killing by unsequestering Bim and Bak and enhancing a Bax conformational change induced by TRAIL. These findings suggest a novel strategy to enhance cross-talk between the extrinsic and intrinsic apoptotic pathways to improve therapeutic efficacy against pancreatic cancer. [Cancer Res 2008;68(8):2944–51]
The Promyelocytic Leukemia Zinc Finger–MicroRNA-221/-222 Pathway Controls Melanoma Progression through Multiple Oncogenic Mechanisms
Authors: Felicetti Federica , Errico M. Cristina , Bottero Lisabianca , Segnalini Patrizia , Stoppacciaro Antonella , Biffoni Mauro , Felli Nadia , Mattia Gianfranco , Petrini Marina , Colombo Mario P. , Peschle Cesare , Carè Alessandra
Published: April 2008

The incidence of cutaneous melanoma is steadily increasing. Although several molecular abnormalities have been associated with melanoma progression, the mechanisms underlying the differential gene expression are still largely unknown and targeted therapies are not yet available. Noncoding small RNAs, termed microRNAs (miR), have been recently reported to play important roles in major cellular processes, including those involved in cancer development and progression. We have identified the promyelocytic leukemia zinc finger (PLZF) transcription factor as a repressor of miR-221 and miR-222 by direct binding to their putative regulatory region. Specifically, PLZF silencing in melanomas unblocks miR-221 and miR-222, which in turn controls the progression of the neoplasia through down-modulation of p27Kip1/CDKN1B and c-KIT receptor, leading to enhanced proliferation and differentiation blockade of the melanoma cells, respectively. In vitro and in vivo functional studies, including the use of antisense “antagomir” oligonucleotides, confirmed the key role of miR-221/-222 in regulating the progression of human melanoma; this suggests that targeted therapies suppressing miR-221/-222 may prove beneficial in advanced melanoma. [Cancer Res 2008;68(8):2745–10]
A Role for TAZ in Migration, Invasion, and Tumorigenesis of Breast Cancer Cells
Authors: Chan Siew Wee , Lim Chun Jye , Guo Ke , Ng Chee Peng , Lee Ian , Hunziker Walter , Zeng Qi , Hong Wanjin
Published: April 2008

TAZ (WWTR1), identified as a 14-3-3 binding protein with a PDZ binding motif, modulates mesenchymal stem cell differentiation. We now show that TAZ plays a critical role in the migration, invasion, and tumorigenesis of breast cancer cells. TAZ is conspicuously expressed in human breast cancer cell lines in which its expression levels generally correlate with the invasiveness of cancer cells. Overexpression of TAZ in low-expressing MCF10A cells causes morphologic changes characteristic of cell transformation and promotes cell migration and invasion. Conversely, RNA interference–mediated knockdown of TAZ expression in MCF7 and Hs578T cells reduces cell migration and invasion. TAZ knockdown in MCF7 cells also retards anchorage-independent growth in soft agar and tumorigenesis in nude mice. Significantly, TAZ is overexpressed in ∼20% of breast cancer samples. These results indicate that TAZ plays a role in the migration, invasion, and tumorigenesis of breast cancer cells and thus presents a novel target for the detection and treatment of breast cancer. [Cancer Res 2008;68(8):2592–8]
Synthetic Lethality by Lentiviral Short Hairpin RNA Silencing of Thymidylate Kinase and Doxorubicin in Colon Cancer Cells Regardless of the p53 Status
Authors: Hu Chun-Mei , Chang Zee-Fen
Published: April 2008

Intracellular supply of dTTP is a highly regulated process and has been a key target for chemotherapeutic drug development. Thymidylate kinase (TMPK) is the key enzyme for dTTP formation in both de novo and salvage pathways. In this study, we used lentiviral-based small hairpin RNA to silence TMPK expression in p53(+/+) and p53(−/−) HCT-116 colon cancer cells. This approach was sufficient to decrease the dTTP pool gradually without affecting p53 expression and generating cytotoxicity. TMPK knockdown significantly increased doxorubicin sensitivity dramatically in p53-proficient, p53-null HCT-116, and LoVo colon cancer cells. The decrease in the dTTP pool using this approach augmented the DNA damage response and enhanced apoptotic induction after exposure to low-dose doxorubicin, leading to cell death. In contrast, silencing of thymidylate synthase which blocks the de novo pathway was incapable of sensitizing p53-null HCT-116 cells to doxorubicin-induced apoptosis because of the compensation by the salvage pathway. Our results suggest the lentiviral delivery of small hairpin RNA targeting TMPK in combination with a low dose of doxorubicin as a new approach to kill colon cancer cells regardless of p53 status. [Cancer Res 2008;68(8):2831–40]
Loss of CTL Function among High-Avidity Tumor-Specific CD8+ T Cells following Tumor Infiltration
Authors: Janicki Claire N. , Jenkinson S. Rhiannon , Williams Neil A. , Morgan David J.
Published: April 2008

A major problem in generating effective antitumor CTL responses is that most tumors express self-antigens to which the immune system is rendered unresponsive due to mechanisms of self-tolerance induction. CTL precursors (CTLp) expressing high-affinity T-cell receptors (TCR) are often functionally deleted from the repertoire, leaving a residual repertoire of CTLp having only low-affinity TCR. Furthermore, even when unique antigens are expressed, their presentation by dendritic cells (DC) may predispose to peripheral tolerance induction rather than the establishment of CTL responses that kill tumor cells. In this study, we examined both high-avidity (CL4) and low-avidity (CL1) CD8+ T-cell responses to a murine renal carcinoma expressing, as a neoantigen, high and low levels of the hemagglutinin (HA) protein from influenza virus A/PR/8 H1N1 (PR8; RencaHAhigh and RencaHAlow). Our data show that, following encounter with KdHA epitopes cross-presented by bone marrow–derived DC, low-avidity CL1 cells become tolerized within tumor-draining lymph nodes (TDLN), and in mice bearing either RencaHAhigh or RencaHAlow tumors, very few form tumor-infiltrating lymphocytes (TIL). In marked contrast, high-avidity CL4 cells differentiate into effector CTL within the TDLN of mice bearing either RencaHAhigh or RencaHAlow tumors, and although they form TIL in both tumors, they lose CTL effector function. Critically, these results show that anticancer therapies involving either adoptive transfer of high-avidity tumor-specific CTL populations or targeting of preexisting tumor antigen–specific memory CD8+ T cells could fail due to the fact that CTL effector function is lost following tumor infiltration. [Cancer Res 2008;68(8):2993–3000]
Coordinated Epidermal Growth Factor Receptor Pathway Gene Overexpression Predicts Epidermal Growth Factor Receptor Inhibitor Sensitivity in Pancreatic Cancer
Authors: Jimeno Antonio , Tan Aik Choon , Coffa Jordy , Rajeshkumar N.V. , Kulesza Peter , Rubio-Viqueira Belen , Wheelhouse Jenna , Diosdado Begoña , Messersmith Wells A. , Iacobuzio-Donahue Christine , Maitra Anirban , Varella-Garcia Marileila , Hirsch Fred R. , Meijer Gerrit A. , Hidalgo Manuel
Published: April 2008

The epidermal growth factor receptor (EGFR) inhibitor erlotinib is approved for treatment of pancreatic cancer but the overall activity is minimal, and known predictive factors for EGFR inhibitor efficacy are infrequent in this disease. We tested the hypothesis that global activation of the EGFR pathway is predictive of EGFR inhibitor efficacy. Pancreatic cancer tumors directly xenografted at surgery were treated with the EGFR inhibitors erlotinib and cetuximab and analyzed for biological features. Two of 10 tumors were sensitive, and by global gene expression profiling with gene set enrichment analysis, the EGFR pathway was highly expressed in sensitive compared with resistant tumors. The core gene components driving EGFR pathway overexpression were pathway ligands and positive effectors. In a prospective validation, the EGFR pathway-based signature correctly predicted anti-EGFR treatment response in eight additional tumors and was not predictive of response to gemcitabine and CI1040 (a MEK inhibitor). Analysis of EGFR, KRAS, and PIK3CA mutations and gene amplification by fluorescence in situ hybridization and multiplex ligation-dependent probe amplification showed that none of these genetic abnormalities were neither predictive nor responsible for the EGFR pathway activation. Coordinated overexpression of the EGFR pathway predicts susceptibility to EGFR inhibitors in pancreatic cancer. These results suggest a phenomenon of pathway addiction and support the value of unbiased system biology approaches in drug development. [Cancer Res 2008;68(8):2841–9]
Redirecting Specificity of T-Cell Populations For CD19 Using the Sleeping Beauty System
Authors: Singh Harjeet , Manuri Pallavi R. , Olivares Simon , Dara Navid , Dawson Margaret J. , Huls Helen , Hackett Perry B. , Kohn Donald B. , Shpall Elizabeth J. , Champlin Richard E. , Cooper Laurence J.N.
Published: April 2008

Genetic modification of clinical-grade T cells is undertaken to augment function, including redirecting specificity for desired antigen. We and others have introduced a chimeric antigen receptor (CAR) to enable T cells to recognize lineage-specific tumor antigen, such as CD19, and early-phase human trials are currently assessing safety and feasibility. However, a significant barrier to next-generation clinical studies is developing a suitable CAR expression vector capable of genetically modifying a broad population of T cells. Transduction of T cells is relatively efficient but it requires specialized manufacture of expensive clinical grade recombinant virus. Electrotransfer of naked DNA plasmid offers a cost-effective alternative approach, but the inefficiency of transgene integration mandates ex vivo selection under cytocidal concentrations of drug to enforce expression of selection genes to achieve clinically meaningful numbers of CAR+ T cells. We report a new approach to efficiently generating T cells with redirected specificity, introducing DNA plasmids from the Sleeping Beauty transposon/transposase system to directly express a CD19-specific CAR in memory and effector T cells without drug selection. When coupled with numerical expansion on CD19+ artificial antigen-presenting cells, this gene transfer method results in rapid outgrowth of CD4+ and CD8+ T cells expressing CAR to redirect specificity for CD19+ tumor cells. [Cancer Res 2008;68(8):2961–71]
Synthetic CD4+ T Cell–Targeted Antigen-Presenting Cells Elicit Protective Antitumor Responses
Authors: Caserta Stefano , Alessi Patrizia , Guarnerio Jlenia , Basso Veronica , Mondino Anna
Published: April 2008

CD4+ helper T cells are critical for protective immune responses and yet suboptimally primed in response to tumors. Cell-based vaccination strategies are under evaluation in clinical trials but limited by the need to derive antigen-presenting cells (APC) from patients or compatible healthy donors. To overcome these limitations, we developed CD4+ T cell–targeted synthetic microbead-based artificial APC (aAPC) and used them to activate CD4+ T lymphocytes specific for a tumor-associated model antigen (Ag) directly from the naive repertoire. In vitro, aAPC specifically primed Ag-specific CD4+ T cells that were activated to express high levels of CD44, produced mainly interleukin 2, and could differentiate into Th1-ike or Th2-like cells in combination with polarizing cytokines. I.v. administration of aAPC led to Ag-specific CD4+ T-cell activation and proliferation in secondary lymphoid organs, conferred partial protection against subcutaneous tumors, and prevented the establishment of lung metastasis. Taken together, our data support the use of cell-free, synthetic aAPC as a specific and versatile alternative to expand peptide-specific CD4+ T cells in adoptive and active immunotherapy. [Cancer Res 2008;68(8):3010–8]
Role of the Aggresome Pathway in Cancer: Targeting Histone Deacetylase 6–Dependent Protein Degradation
Authors: Rodriguez-Gonzalez Agustin , Lin Tara , Ikeda Alan K. , Simms-Waldrip Tiffany , Fu Cecilia , Sakamoto Kathleen M.
Published: April 2008

Misfolded or aggregated proteins have two fates: they are either refolded with the help of chaperones or degraded by the proteasome. Cells also have an alternative pathway that involves intracellular “storage bins” for misfolded intracellular proteins known as aggresomes. Aggresomes recruit motor proteins that transport misfolded or aggregated proteins to chaperones and proteasomes for subsequent destruction. There is emerging evidence that inhibiting the aggresome pathway leads to accumulation of misfolded proteins and apoptosis in tumor cells through autophagy. We discuss the role of aggresomes in cancer and the potential to target this pathway for therapy. [Cancer Res 2008;68(8):2557–60]
Targeted Deletion of Prkar1a Reveals a Role for Protein Kinase A in Mesenchymal-to-Epithelial Transition
Authors: Nadella Kiran S. , Jones Georgette N. , Trimboli Anthony , Stratakis Constantine A. , Leone Gustavo , Kirschner Lawrence S.
Published: April 2008

Dysregulation of protein kinase A (PKA) activity, caused by loss of function mutations in PRKAR1A, is known to induce tumor formation in the inherited tumor syndrome Carney complex (CNC) and is also associated with sporadic tumors of the thyroid and adrenal. We have previously shown that Prkar1a+/− mice develop schwannomas reminiscent of those seen in CNC and that similar tumors are observed in tissue-specific knockouts (KO) of Prkar1a targeted to the neural crest. Within these tumors, we have previously described the presence of epithelial islands, although the nature of these structures was unclear. In this article, we report that these epithelial structures are derived from KO cells originating in the neural crest. Analysis of the mesenchymal marker vimentin revealed that this protein was markedly down-regulated not only from the epithelial islands, but also from the tumor as a whole, consistent with mesenchymal-to-epithelial transition (MET). In vitro, Prkar1a null primary mouse embryonic fibroblasts, which display constitutive PKA signaling, also showed evidence for MET, with a loss of vimentin and up-regulation of the epithelial marker E-cadherin. Reduction of vimentin protein occurred at the posttranslational level and was rescued by proteasomal inhibition. Finally, this down-regulation of vimentin was recapitulated in the adrenal nodules of CNC patients, confirming an unexpected and previously unrecognized role for PKA in MET. [Cancer Res 2008;68(8):2671–7]
Interleukin 21 Enhances Antibody-Mediated Tumor Rejection
Authors: Smyth Mark J. , Teng Michele W.L. , Sharkey Janelle , Westwood Jennifer A. , Haynes Nicole M. , Yagita Hideo , Takeda Kazuyoshi , Sivakumar Pallavur V. , Kershaw Michael H.
Published: April 2008

Interleukin-21 (IL-21) is a cytokine with structural and sequence homology to IL-2 and IL-15 that has antitumor activity alone in mouse experimental tumor models and a tolerable safety profile in phase I trials in patients with metastatic melanoma and renal cell carcinoma. Several monoclonal antibodies (mAb) targeted at tumor-associated antigens also have improved antitumor activities in mice when used in combination with IL-21. Recently, we described a rational three antibody-based approach (triple mAb, TrimAb) to eradicating established mouse tumors that required the generation of tumor-reactive CD8+ T cells and IFN-γ. Herein, we show that sequentially combining TrimAb with recombinant IL-21 can significantly improve the antitumor activity of this combination against very advanced disease. These data further support the use of IL-21 in adjuvant settings where strong T cell–mediated immune responses to tumors can be generated. [Cancer Res 2008;68(8):3019–25]