bluuebunny/crossref_metadata_2025 huggingface dataset:
Duration-Sensitive Neurons in the Inferior Colliculus of Horseshoe Bats: Adaptations for Using CF-FM Echolocation Pulses
Authors: Luo Feng , Metzner Walter , Wu Feijian J. , Zhang Shuyi Y. , Chen Qicai C.
Published: November 2007

The present study examines duration-sensitive neurons in the inferior colliculus (IC) of the least horseshoe bat, Rhinolophus pusillus, from China. In contrast to other bat species tested for duration selectivity so far, echolocation pulses emitted by horseshoe bats are generally longer and composed of a long constant-frequency (CF) component followed by a short downward frequency-modulated (FM) sweep (CF-FM pulse). We used combined CF-FM pulses to analyze the differential effects that these two pulse components had on the duration tuning in neurons of the horseshoe bat's IC. Consistent with results from other mammals, duration-sensitive neurons found in the least horseshoe bat fall into three main classes: short-pass, band-pass, and long-pass. Using a CF stimulus alone, 54% (51/95) of all IC neurons showed at least one form of duration selectivity at one or more stimulus intensities. In 65 of the 95 IC neurons tested with CF pulses, we were also able to test their duration selectivity for a combined CF-FM pulse, which increased the ratio of duration-sensitive neurons to 66% (43/65). Seven to 15 neurons that failed to show duration tuning for CF bursts became duration sensitive for CF-FM pulses, with most of them exhibiting short-pass (depending on stimulus intensity, between 4 and 8 neurons) or band-pass tuning (1–3 neurons). Increasing stimulus intensities did not affect the duration tuning in 53% (23/43) of duration-sensitive neurons for CF bursts and in about 26% (7/27) for CF-FM stimuli. In the remaining neurons, increasing sound levels generally reduced the ratio of duration-sensitive neurons to 33% for CF and 37% for CF-FM stimulation. In those that remained duration sensitive, louder CF bursts shortened best durations in band-pass neurons and cutoff durations in short- and long-pass neurons, whereas louder CF-FM stimuli reduced the cutoff durations only in short-pass neurons. Bandwidths of band-pass neurons were not significantly affected by any stimulus configuration, with only a slight trend for increasing bandwidths for louder CF bursts (but not CF-FM stimuli). Best durations and cutoff durations reached higher values than those in the other bat species examined so far and roughly match the longer durations of echolocation pulses emitted by horseshoe bats. Therefore presentation of a CF-FM stimulus improved the duration sensitivity in IC neurons by increasing the ratio of duration-tuned neurons and making them less susceptible to changes in signal intensity.
α2-Adrenergic Receptors Modify Dendritic Spike Generation Via HCN Channels in the Prefrontal Cortex
Authors: Barth Albert M. I. , Vizi E. Sylvester , Zelles Tibor , Lendvai Balazs
Published: November 2007

Although dendritic spikes are generally thought to be restricted to the distal apical dendrite, we know very little about the possible modulatory mechanisms that set the spatial limits of dendritic spikes. Our experiments demonstrated that high-frequency trains of backpropagating action potentials avoided filtering in the apical dendrite and initiated all-or-none dendritic Ca2+ transients associated with dendritic spikes in layer 5 pyramidal neurons of the prefrontal cortex. The block of hyperpolarization-activated currents ( Ih) by ZD7288 could shift the frequency threshold and decreased the number of action potentials required to produce the all-or-none Ca2+ transient. Activation of α2-adrenergic receptors could also shift the frequency domain of spike induction to lower frequencies. Our data suggest that noradrenergic activity in the prefrontal cortex influences dendritic Ih and extends the zone of dendritic spikes in the apical dendrite via α2-adrenergic receptors. This mechanism might be one cellular correlate of the α2-receptor–mediated actions on working memory.
Mechanisms of Noise-Induced Improvement in Light-Intensity Encoding inHermissendaPhotoreceptor Network
Authors: Butson Christopher R. , Clark Gregory A.
Published: November 2007

In a companion paper we showed that random channel and synaptic noise improve the ability of a biologically realistic, GENESIS-based computational model of the Hermissenda eye to encode light intensity. In this paper we explore mechanisms for noise-induced improvement by examining contextual spike-timing relationships among neurons in the photoreceptor network. In other systems, synaptically connected pairs of spiking cells can develop phase-locked spike-timing relationships at particular, well-defined frequencies. Consequently, domains of stability (DOS) emerge in which an increase in the frequency of inhibitory postsynaptic potentials can paradoxically increase, rather than decrease, the firing rate of the postsynaptic cell. We have extended this analysis to examine DOS as a function of noise amplitude in the exclusively inhibitory Hermissenda photoreceptor network. In noise-free simulations, DOS emerge at particular firing frequencies of type B and type A photoreceptors, thus producing a nonmonotonic relationship between their firing rates and light intensity. By contrast, in the noise-added conditions, an increase in noise amplitude leads to an increase in the variance of the interspike interval distribution for a given cell; in turn, this blocks the emergence of phase locking and DOS. These noise-induced changes enable the eye to better perform one of its basic tasks: encoding light intensity. This effect is independent of stochastic resonance, which is often used to describe perithreshold stimuli. The constructive role of noise in biological signal processing has implications both for understanding the dynamics of the nervous system and for the design of neural interface devices.
Cannabinoids: A New Group of Agonists of PPARs
Authors: Sun Yan , Bennett Andy
Published: November 2007

Cannabinoids have been used medicinally and recreationally for thousands of years and their effects were proposed to occur mainly via activation of the G-protein-coupled receptorCB1/CB2(cannabinoid receptor 1/2). Discovery of potent synthetic analogs of the natural cannabinoids as clinically useful drugs is the sustained aim of cannabinoid research. This demands that these new compounds be free of the psychotropic effects that connected with the recreational use of cannabinoids. In preclinical studies cannabinoids displayed many of the characteristics of nonsteroidal anti-inflammatory drugs (NSAIDs) and it seems to be free of unwanted side effects. An increasing number of therapeutic actions of cannabinoid are being reported that do not appear to be mediated by eitherCB1orCB2, and recently nuclear receptor superfamily PPARs (peroxisome-proliferator-activated receptors) have been suggested as the target of certain cannabinoids. This review summarizes the evidence for cannabinoid activation on PPARs and possible associated remedial potentials.
A Comparison Performance Analysis of QoS WLANs: Approaches with Enhanced Features
Authors: Papapanagiotou Ioannis , Paschos Georgios S. , Devetsikiotis Michael
Published: November 2007

The main contribution of this work is to compare and enhance known methods for performance analysis of the IEEE 802.11e MAC layer, such as the use of Markov chains, queuing theory, and probabilistic analysis. It is the first paper that bases its outputs upon comparison of metrics such as complexity, flexibility, and accuracy, leading to the novel use of a metamodeling comparison. For the analysis, complexity theory and theL-square distance method for accuracy are used. In addition, the proposed analyses carry by themselves scientific interest, because they are extended enhancements with the latest EDCA parameters. A form of the PMF of the MAC delay and first-order moments are found using the PGF complex frequency domain function. The analyses incorporate a Gaussian erroneous channel in order to reflect the real conditions of the MAC layer.
On Bloch-Type Functions with Hadamard Gaps
Authors: Stevic Stevo
Published: November 2007

We give some sufficient and necessary conditions for an analytic functionfon the unit ballBwith Hadamard gaps, that is, forf(z)=∑k=1∞Pnk(z)(the homogeneous polynomial expansion off) satisfyingnk+1/nk≥λ>1for allk∈ℕ, to belong to the spaceℬpα(B)={f|sup0<r<1(1−r2)α\|ℛfr\|p<∞,f∈H(B)},p=1,2,∞as well as to the corresponding little space. A remark on analytic functions with Hadamard gaps on mixed norm space on the unit disk is also given.
Sobriety and Localic Compactness in Categories ofL-Bitopological Spaces
Authors: El-Saady Kamal , Bakier M. Y.
Published: November 2007

The notions ofL-sobriety andL-spatiality are introduced for the categoryL-BiTop ofL-bitopological spaces. Such notions are used to extend the known adjunction between the categoryL-Top ofL-topological spaces and the category Loc of locals to one between the categoryL-BiTop and BiLoc. Also, the concepts of localic regularity and localic compactness are introduced in the mentioned category.
Online Artifact Removal for Brain-Computer Interfaces Using Support Vector Machines and Blind Source Separation
Authors: Halder Sebastian , Bensch Michael , Mellinger Jürgen , Bogdan Martin , Kübler Andrea , Birbaumer Niels , Rosenstiel Wolfgang
Published: November 2007

We propose a combination of blind source separation (BSS) and independent component analysis (ICA) (signal decomposition into artifacts and nonartifacts) with support vector machines (SVMs) (automatic classification) that are designed for online usage. In order to select a suitable BSS/ICA method, three ICA algorithms (JADE, Infomax, and FastICA) and one BSS algorithm (AMUSE) are evaluated to determine their ability to isolate electromyographic (EMG) and electrooculographic (EOG) artifacts into individual components. An implementation of the selected BSS/ICA method with SVMs trained to classify EMG and EOG artifacts, which enables the usage of the method as a filter in measurements with online feedback, is described. This filter is evaluated on three BCI datasets as a proof-of-concept of the method.
Preparation and Characterization of Poly(D,L-Lactide-co-Glycolide) Nanoparticles Containing Ascorbic Acid
Authors: Stevanovic Magdalena M. , Jordovic Branka , Uskokovic Dragan P.
Published: November 2007

This paper is covering new, simplistic method of obtaining the system for controlled delivery of the ascorbic acid. Copolymer poly (D,L-lactide-co-glycolide) (DLPLG) nanoparticles are produced using physical method with solvent/nonsolvent systems where obtained solutions were centrifuged. The encapsulation of the ascorbic acid in the polymer matrix is performed by homogenization of water and organic phases. Particles of the DLPLG with the different content of ascorbic acid have different morphological characteristics, that is, variable degree of uniformity, agglomeration, sizes, and spherical shaping. Mean sizes of nanoparticles, which contain DLPLG/ascorbic acid in the ratio 85/150%, were between 130 to 200 nm depending on which stereological parameters are considered (maximal diameters Dmax, feret X, or feret Y). By introducing up to 15% of ascorbic acid, the spherical shape, size, and uniformity of DLPLG particles are preserved. The samples were characterized by infrared spectroscopy, scanning electron microscopy, stereological analysis, and ultraviolet spectroscopy.
Structure of Low-Lying Excited States of Guanine in DNA and Solution: Combined Molecular Mechanics and High-Level Coupled Cluster Studies
Authors: Kowalski Karol , Valiev Marat
Published: November 2007

High-level ab-initio equation-of-motion coupled-cluster methods with singles, doubles, and noniterative triples are used, in conjunction with the combined quantum mechanical molecular mechanics approach, to investigate the structure of low-lying
excited states of the guanine base in DNA and solvated environments. Our results indicate that while the excitation energy of the first excited state is barely changed compared to its gas-phase counterpart, the excitation energy of the second excited
state is blue-shifted by 0.24 eV.
The Geometry of Statistical Efficiency and Matrix Statistics
Authors: Gustafson K.
Published: November 2007

We will place certain parts of the theory of statistical efficiency into the author's
operator trigonometry (1967), thereby providing new geometrical understanding of statistical efficiency. Important
earlier results of Bloomfield and Watson, Durbin and Kendall, Rao and Rao, will be so interpreted. For
example, worse case relative least squares efficiency corresponds to and is achieved by the maximal turning
antieigenvectors of the covariance matrix. Some little-known historical perspectives will also be exposed.
The overall view will be emphasized.
Existence Principle for Advanced Integral Equations on Semiline
Authors: Chiş Adela
Published: November 2007

The continuation principle for generalized contractions in gauge spaces is used to discuss nonlinear integral equations with advanced argument.
Multiple Intraosseous Calvarial Hemangiomas Mimicking Metastasis from Renal Cell Carcinoma
Authors: Malde Rohit , Moss Tim , Malcolm George , Whittlestone Tim , Bahl Amit
Published: November 2007

Renal cell carcinomas are known to metastasise to the bones in the form of lytic lesions. However, not all osteolytic lesions in patients with renal cell carcinoma are metastatic in nature. The report describes the case of a 68-year old lady who was diagnosed with a renal cell carcinoma 3 and half years back and treated with radical nephrectomy along with excision of an inferior vena cava tumour thrombus. The tumour was completely excised and she remained disease free till date. Subsequently, multiple lytic lesions were detected incidentally on the cranial vault, which on biopsy demonstrated intraosseous hemangioma. Though it is well known that renal cell carcinomas can metastasise to the bones in the form lytic lesions, it is important for clinicians to remember a few other differentials, one of which would be an intraosseous hemangioma, which is a benign pathology. Many times patients would be treated as having metastatic disease merely on radiological findings. In this case report, there was a high index of radiological suspicion for metastases, however establishing diagnosis by biopsy prevented overtreatment in this instance.
Chemosensitization of B-Cell Lymphomas by Methylseleninic Acid Involves Nuclear Factor-κB Inhibition and the Rapid Generation of Other Selenium Species
Authors: Jüliger Simone , Goenaga-Infante Heidi , Lister T. Andrew , Fitzgibbon Jude , Joel Simon P.
Published: November 2007

Although recent reports suggest that selenium can modulate the activity of cytotoxic drugs, the mechanism underlying this activity remains unclear. This has been investigated using a panel of human B-cell lymphoma cell lines. The cytotoxic effects of chemotherapeutic agents (e.g., doxorubicin, etoposide, 4-hydroperoxycyclophosphamide, melphalan, and 1-β-d-arabinofuranosylcytosine) were increased by up to 2.5-fold when combined with minimally toxic concentrations (EC5-10) of the organic selenium compound, methylseleninic acid (MSA). DNA strand breaks were identified using comet assays, but the measured genotoxic activity of the combinations did not explain the observed synergistic effects in cell death. However, minimally toxic (EC10) concentrations of MSA induced a 50% decrease in nuclear factor-κB (NF-κB) activity after an exposure of 5 h, similar to that obtained with the specific NF-κB inhibitor, BAY 11-7082. Combinations of BAY 11-7082 with these cytotoxic drugs also resulted in synergism, suggesting that the chemosensitizing activity of MSA is mediated, at least in part, by its effects on NF-κB. Basal intracellular selenium concentration was higher in a MSA-sensitive cell line. After exposure to MSA, methylselenocysteine and selenomethionine were identified as the main intracellular species generated. Volatile selenium species, trapped using solid-phase microextraction fibers, were identified as dimethylselenide and dimethyldiselenide. These volatile species are thought to be the most biologically active forms of selenium. Taken together, these results show that the NF-κB pathway is one target for MSA underlying the interaction between MSA and chemotherapy. These data encourage the further clinical development of selenium as a potential modulator of cytotoxic drug activity in B-cell lymphomas. [Cancer Res 2007;67(22):10984–92]
High Expression of Lymphocyte-Associated Genes in Node-Negative HER2+ Breast Cancers Correlates with Lower Recurrence Rates
Authors: Alexe Gabriela , Dalgin Gul S. , Scanfeld Daniel , Tamayo Pablo , Mesirov Jill P. , DeLisi Charles , Harris Lyndsay , Barnard Nicola , Martel Maritza , Levine Arnold J. , Ganesan Shridar , Bhanot Gyan
Published: November 2007

Gene expression analysis has identified biologically relevant subclasses of breast cancer. However, most classification schemes do not robustly cluster all HER2+ breast cancers, in part due to limitations and bias of clustering techniques used. In this article, we propose an alternative approach that first separates the HER2+ tumors using a gene amplification signal for Her2/neu amplicon genes and then applies consensus ensemble clustering separately to the HER2+ and HER2− clusters to look for further substructure. We applied this procedure to a microarray data set of 286 early-stage breast cancers treated only with surgery and radiation and identified two basal and four luminal subtypes in the HER2− tumors, as well as two novel and robust HER2+ subtypes. HER2+ subtypes had median distant metastasis-free survival of 99 months [95% confidence interval (95% CI), 83–118 months] and 33 months (95% CI, 11–54 months), respectively, and recurrence rates of 11% and 58%, respectively. The low recurrence subtype had a strong relative overexpression of lymphocyte-associated genes and was also associated with a prominent lymphocytic infiltration on histologic analysis. These data suggest that early-stage HER2+ cancers associated with lymphocytic infiltration are a biologically distinct subtype with an improved natural history. [Cancer Res 2007;67(22):10669–76]
HIV-1 Protease Inhibitors Nelfinavir and Atazanavir Induce Malignant Glioma Death by Triggering Endoplasmic Reticulum Stress
Authors: Pyrko Peter , Kardosh Adel , Wang Weijun , Xiong Wenyong , Schönthal Axel H. , Chen Thomas C.
Published: November 2007

HIV type 1 (HIV-1) protease inhibitors (PI) have been shown to have anticancer activity in non–HIV-associated human cancer cells. The underlying mechanism of this effect is unclear. Here, we show that the PIs nelfinavir and atazanavir cause cell death in various malignant glioma cell lines in vitro. The underlying mechanism of this antitumor effect involves the potent stimulation of the endoplasmic reticulum (ER) stress response (ESR), as indicated by increased expression of two ESR markers, GRP78 and CHOP, and activation of ESR-associated caspase-4. Induction of ESR seems to play a central role in PI-induced cell death because small interfering RNA–mediated knockdown of the protective ER chaperone GRP78 sensitizes cells; whereas knockdown of proapoptotic caspase-4 protects cells from PI-induced cell death. Furthermore, the treatment of cells with PIs leads to aggresome formation and accumulation of polyubiquitinated proteins, implying proteasome inhibition. Thus, our results support a model whereby PIs cause tumor cell death via triggering of the ESR, inhibition of proteasome activity, and subsequent accumulation of misfolded proteins. Inhibition of glioma growth via ESR takes place in the in vivo setting as well, as nelfinavir inhibits the growth of xenografted human malignant glioma, with concomitant induction of the proapoptotic ER stress marker CHOP. Because ER stress has also been reported as the mechanism for insulin resistance and diabetes, our ER stress model of PI function may also explain why these drugs may induce insulin resistance as one of their most common side effects. [Cancer Res 2007;67(22):10920–8]
The Lysine 831 of Vascular Endothelial Growth Factor Receptor 1 Is a Novel Target of Methylation by SMYD3
Authors: Kunizaki Masaki , Hamamoto Ryuji , Silva Fabio Pittella , Yamaguchi Kiyoshi , Nagayasu Takeshi , Shibuya Masabumi , Nakamura Yusuke , Furukawa Yoichi
Published: November 2007

We previously identified SMYD3 as a histone methyltransferase and showed that its expression was elevated in colorectal, hepatocellular, and breast carcinomas. In the investigation of methyltransferase activity of SMYD3, we have found that vascular endothelial growth factor receptor 1 (VEGFR1) was also methylated by SMYD3. We further identified the methylated residue at VEGFR1 lysine 831, which is located in the kinase domain and is conserved among VEGFR1 orthologues. We also found that the lysine is followed by serine, which is conserved among some of the methylation targets of histone methyltransferases. Furthermore, methylation of VEGFR1 enhanced its kinase activity in cells. These data should be helpful for the profound understanding of the biological role of SMYD3 and regulatory mechanisms of VEGFR1. Additionally our finding may facilitate the development of strategies that may inhibit the progression of cancer cells. [Cancer Res 2007;67(22):10759–65]
ΔDNMT3B Variants Regulate DNA Methylation in a Promoter-Specific Manner
Authors: Wang Jie , Bhutani Manisha , Pathak Ashutosh K. , Lang Wenhua , Ren Hening , Jelinek Jaroslav , He Rong , Shen Lanlan , Issa Jean-Pierre , Mao Li
Published: November 2007

DNA methyltransferase 3B (DNMT3B) is critical in de novo DNA methylation during development and tumorigenesis. We recently reported the identification of a DNMT3B subfamily, ΔDNMT3B, which contains at least seven variants, resulting from alternative pre-mRNA splicing. ΔDNMT3Bs are the predominant expression forms of DNMT3B in human lung cancer. A strong correlation was observed between the promoter methylation of RASSF1A gene but not p16 gene (both frequently inactivated by promoter methylation in lung cancer) and expression of ΔDNMT3B4 in primary lung cancer, suggesting a role of ΔDNMT3B in regulating promoter-specific methylation of common tumor suppressor genes in tumorigenesis. In this report, we provide first experimental evidence showing a direct involvement of ΔDNMT3B4 in regulating RASSF1A promoter methylation in human lung cancer cells. Knockdown of ΔDNMT3B4 expression by small interfering RNA resulted in a rapid demethylation of RASSF1A promoter and reexpression of RASSF1A mRNA but had no effect on p16 promoter in the lung cancer cells. Conversely, normal bronchial epithelial cells with stably transfected ΔDNMT3B4 gained an increased DNA methylation in RASSF1A promoter but not p16 promoter. We conclude that promoter DNA methylation can be differentially regulated and ΔDNMT3Bs are involved in regulation of such promoter-specific de novo DNA methylation. [Cancer Res 2007;67(22):10647–52]
Prolonged Chronic Inflammation Progresses to Dysplasia in a Novel Rat Model of Colitis-Associated Colon Cancer
Authors: Santiago Cariluz , Pagán Beatriz , Isidro Angel A. , Appleyard Caroline B.
Published: November 2007

Inflammatory bowel disease (IBD) is a gastrointestinal disorder of unknown etiology or cure. One complication of IBD is an increased risk for development of colon cancer. The aims of this study were to use a previously established rat model of colitis to develop a new model of colitis-associated colon cancer and ascertain the involvement of three cancer-related genes: K-ras, adenomatous polyposis coli (APC), and p53. Four groups of rats were used: reactivated 1,2-dimethylhydrazine [DMH; trinitrobenzene sulfonic acid (TNBS) was used to induce colitis followed by a weekly s.c. dose of DMH], prolonged reactivation (inflammation was induced with TNBS, then maintained twice a week), saline-DMH (animals received saline instead of TNBS followed by a weekly dose of DMH), and normal (received no treatment). Animals were sacrificed at 5, 10, or 15 weeks, and colon samples were taken for pathologic analysis and gene mutation detection. No dysplasia was found in the normal group. The highest incidences of dysplasia were as follows: prolonged reactivation group at 5 weeks (60%), reactivated DMH group at 10 weeks (83%), and saline-DMH group at 15 weeks (67%). Carcinoma was found in both the prolonged reactivation and saline-DMH groups. No mutations were found in the K-ras oncogene; however 62% of the APC samples (exon 15 at nucleotide 2778) and 76% of p53 (exon 6 at nucleotide 1327) showed substitutions. The prolonged reactivation group may be considered a new model of colitis-associated colon cancer, offering the potential to study cancer prevention strategies for patients with IBD. [Cancer Res 2007;67(22):10766–73]
The Extra-domain A of Fibronectin Is a Vascular Marker of Solid Tumors and Metastases
Authors: Rybak Jascha-N. , Roesli Christoph , Kaspar Manuela , Villa Alessandra , Neri Dario
Published: November 2007

One of the most promising new avenues for the development of more selective and efficacious cancer therapies relies on the antibody-mediated targeted delivery of bioactive agents (e.g., cytokines) to the tumor environment. The identification of quantitative differences in the expression of accessible vascular proteins in metastatic lesions and host organs facilitate the development of antibody-based strategies, which should be highly efficient and selective, considering the fact that an over-exuberant neovasculature is a characteristic feature of aggressive cancers, and that tumor blood vessels are readily accessible for i.v. administered therapeutic agents. Metastasis is the main cause of death in cancer. The availability of metastasis-specific antigens accessible from the bloodstream will allow a selective delivery of therapeutic agents to metastatic lesions using antibodies as vehicles. Using a combination of vascular biotinylation of 129Sv mice bearing F9 liver metastases and mass spectrometry, we have identified 435 accessible proteins in metastasis and host organ specimens, of which 117 were exclusively detected in metastases. In particular, we found that the alternatively spliced extra-domain A (EDA) of fibronectin is strongly expressed in the neovasculature of liver metastases, while being undetectable in most normal organs. A human antibody to EDA was used to show EDA expression in the neovasculature of metastases and primary tumors of human cancer patients and to target mouse liver metastases and subcutaneous tumors in vivo. Human antibody fragments specific to the EDA domain of fibronectin promise to serve as general vehicles for the efficient and selective delivery of imaging agents or therapeutic molecules to metastatic sites. [Cancer Res 2007;67(22):10948–57]
Genome-Scale MicroRNA and Small Interfering RNA Screens Identify Small RNA Modulators of TRAIL-Induced Apoptosis Pathway
Authors: Ovcharenko Dmitriy , Kelnar Kevin , Johnson Charles , Leng Nan , Brown David
Published: November 2007

Tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) binds to death receptors 4/5 and selectively induces caspase-dependent apoptosis. The RNA interference screening approach has led to the discovery and characterization of several TRAIL pathway components in human cells. Here, libraries of synthetic small interfering RNA (siRNA) and microRNAs (miRNA) were used to probe the TRAIL pathway. In addition to known genes, siRNAs targeting CDK4, PTGS1, ALG2, CLCN3, IRAK4, and MAP3K8 altered TRAIL-induced caspase-3 activation responses. Introduction of the miRNAs let-7c, mir-10a, mir-144, mir-150, mir-155, and mir-193 also affected the activation of the caspase cascade. Putative targets of these endogenous miRNAs included genes encoding death receptors, caspases, and other apoptosis-related genes. Among the novel genes revealed in the screen, CDK4 was selected for further characterization. CDK4 was the only member of the cyclin-dependent kinase gene family that bore a unique function in apoptotic signal transduction. [Cancer Res 2007;67(22):10782–8]
Cyclooxygenase-2 Is a Target Gene of Rho GDP Dissociation Inhibitor β in Breast Cancer Cells
Authors: Schunke Dario , Span Paul , Ronneburg Henrike , Dittmer Angela , Vetter Martina , Holzhausen Hans-Jürgen , Kantelhardt Eva , Krenkel Sylke , Müller Volkmar , Sweep Fred C.G.J. , Thomssen Christoph , Dittmer Jürgen
Published: November 2007

Rho GDP dissociation inhibitor β (Rho-GDIβ), an inhibitor of Rho GTPases, is primarily expressed by hematopoietic cells but is also found in epithelial cancer cells. Recently, we have identified Rho-GDIβ as a target of the transcription factor Ets1. Here, we show that, in breast cancer cells, Ets1 regulates Rho-GDIβ expression and binds to the upstream region of the Rho-GDIβ gene. Furthermore, in primary breast cancer, Rho-GDIβ is coexpressed with Ets1. Studying the function of Rho-GDIβ in breast cancer, we found that a Rho-GDIβ–specific small interfering RNA increased cellular migration but also decreased the expression of cyclooxygenase-2 (Cox-2) oncogene as shown by microarray, quantitative reverse transcription-PCR, and Western blot analyses. Further studies revealed that Rho-GDIβ regulates Cox-2 gene at least partly on the transcriptional level, most likely by activating nuclear factor of activated T cells 1 (NFAT-1). Vav-1, an interaction partner of Rho-GDIβ, was also found to interfere with Cox-2 expression and NFAT-1 cellular distribution, suggesting a cooperative action of Rho-GDIβ and Vav-1 on Cox-2 expression. To explore the importance of Rho-GDIβ for the survival of breast cancer patients, two cohorts, including 263 and 117 patients, were analyzed for clinical outcome in relation to Rho-GDIβ RNA and protein levels, respectively. Expression of Rho-GDIβ was not associated with either disease-free or overall survival in the two patient population. Our data suggest that the expression of Rho-GDIβ in breast cancer is neither beneficial nor disadvantageous to the patient. This may be the net effect of two opposing activities of Rho-GDIβ, one that suppresses tumor progression by inhibiting migration and the other that stimulates it by enhancing Cox-2 expression. [Cancer Res 2007;67(22):10694–702]
Pirh2 Promotes Ubiquitin-Dependent Degradation of the Cyclin-Dependent Kinase Inhibitor p27Kip1
Authors: Hattori Takayuki , Isobe Tomoyasu , Abe Kenji , Kikuchi Hirotoshi , Kitagawa Kyoko , Oda Toshiaki , Uchida Chiharu , Kitagawa Masatoshi
Published: November 2007

The cyclin-dependent kinase inhibitor p27Kip1 is degraded in late G1 phase by the ubiquitin-proteasome pathway, allowing cells to enter S phase. Due to accelerated degradation of p27Kip1, various human cancers express low levels of p27Kip1 associated with poor prognosis. S-phase kinase–associated protein 2, the F-box protein component of an SCF ubiquitin ligase complex, is implicated in degradation of p27Kip1 during S-G2 phases. Recently, Kip1 ubiquitination–promoting complex has been reported as another ubiquitin ligase that targets cytoplasmic p27Kip1 exported from the nucleus in G0-G1 phases. Here, we identified a RING-H2–type ubiquitin ligase, Pirh2, as a p27Kip1-interacting protein. Endogenous Pirh2 physically interacted with endogenous p27Kip1 in mammalian cells. Pirh2 directly ubiquitinated p27Kip1 in an intact RING finger domain-dependent manner in vivo, as well as in vitro. Ablation of endogenous Pirh2 by small interfering RNA increased the steady-state level of p27Kip1 and decelerated p27Kip1 turnover. Depletion of Pirh2 induced accumulation of p27Kip1 in both the nucleus and cytoplasm. Pirh2 expression was induced from late G1-S phase, whereas p27Kip1 was decreased in synchronization with accumulation of Pirh2. Furthermore, reduction of Pirh2 resulted in an impairment of p27Kip1 degradation and an inhibition of cell cycle progression at G1-S transition in a p53-independent manner. Overall, the results indicate that Pirh2 acts as a negative regulator of p27Kip1 function by promoting ubiquitin-dependent proteasomal degradation. [Cancer Res 2007;67(22):10789–95]
Cathepsin E Prevents Tumor Growth and Metastasis by Catalyzing the Proteolytic Release of Soluble TRAIL from Tumor Cell Surface
Authors: Kawakubo Tomoyo , Okamoto Kuniaki , Iwata Jun-ichi , Shin Masashi , Okamoto Yoshiko , Yasukochi Atsushi , Nakayama Keiichi I. , Kadowaki Tomoko , Tsukuba Takayuki , Yamamoto Kenji
Published: November 2007

The aspartic proteinase cathepsin E is expressed predominantly in cells of the immune system and highly secreted by activated phagocytes, and deficiency of cathepsin E in mice results in a phenotype affecting immune responses. However, because physiologic substrates for cathepsin E have not yet been identified, the relevance of these observations to the physiologic functions of this protein remains speculative. Here, we show that cathepsin E specifically induces growth arrest and apoptosis in human prostate carcinoma tumor cell lines without affecting normal cells by catalyzing the proteolytic release of soluble tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) from the cell surface. The antitumor activity of cathepsin E was corroborated by in vivo studies with mice bearing human and mouse tumor transplants. Administration of purified cathepsin E into human tumor xenografts in nude mice dose-dependently induced apoptosis in the tumor cells to inhibit tumor growth. The growth, viability, and metastasis of mouse B16 melanoma cells were also more profound in cathepsin E–deficient mice compared with those in the syngeneic wild-type and transgenic mice overexpressing cathepsin E. Taken together, the number of apoptotic tumor cells, as well as tumor-infiltrating activated macrophages, was apparently reduced in cathepsin E–deficient mice compared with those in the other two groups, implying the positive correlation of endogenous cathepsin E levels with the extent of tumor suppression in vivo. These results thus indicate that cathepsin E plays a substantial role in host defense against tumor cells through TRAIL-dependent apoptosis and/or tumor-associated macrophage-mediated cytotoxicity. [Cancer Res 2007;67(22):10869–78]
Peptide-Mediated Targeting to Tumor Blood Vessels of Lung Cancer for Drug Delivery
Authors: Lee Tong-Young , Lin Chin-Tarng , Kuo Szu-Yao , Chang De-Kuan , Wu Han-Chung
Published: November 2007

Antiangiogenesis therapies for the treatment of cancers hold the promise of high efficacy and low toxicity. In vivo phage display was used to identify peptides specifically targeting tumor blood vessels. The peptide SP5-52 recognized tumor neovasculature but not normal blood vessels in severe combined immunodeficiency mice bearing human tumors. Synthetic peptide was shown to inhibit the binding of PC5-52 phage particles to the tumor mass in the competitive inhibition assay. Several selected phage clones displayed the consensus motif, proline-serine-proline, and this motif was crucial for peptide binding to the tumor neovasculature. SP5-52 peptides also bound vascular endothelial growth factor–stimulated human umbilical vein endothelial cells and blood vessels of human lung cancer surgical specimens. Furthermore, this targeting phage was shown to home to tumor tissues from eight different types of human tumor xenografts following in vivo phage display experiments. An SP5-52 peptide-linked liposome carrying doxorubicin enhanced the therapeutic efficacy of the drug, markedly decreased tumor blood vessels, and resulted in higher survival rates of human lung and oral cancer–bearing xenograft mice. The current study indicates that ligand-targeted therapy offers improved therapeutic effects over conventional anticancer drug therapy, and that the peptide SP5-52 specifically targets tumor neovasculature and is a good candidate for targeted drug delivery to solid tumors. [Cancer Res 2007;67(22):10958–65]
Chimeric NKG2D–Modified T Cells Inhibit Systemic T-Cell Lymphoma Growth in a Manner Involving Multiple Cytokines and Cytotoxic Pathways
Authors: Zhang Tong , Barber Amorette , Sentman Charles L.
Published: November 2007

In this study, the efficacy and mechanisms of chimeric NKG2D receptor (chNKG2D)–modified T cells in eliminating NKG2D ligand–positive RMA/Rae1 lymphoma cells were evaluated. Intravenous injection of RMA/Rae1 cells led to significant tumor formation in spleens and lymph nodes within 2 weeks. Adoptive transfer of chNKG2D-modified T cells after tumor injection significantly reduced tumor burdens in both spleens and lymph nodes, and prolonged the survival of tumor-bearing mice. Multiple treatments with chNKG2D T cells resulted in long-term tumor-free survival. Moreover, these long-term survivors were resistant to rechallenge with RMA tumor cells (NKG2D ligand–negative), and their spleen and lymph node cells produced IFN-γ in response to RMA but not to other tumors in vitro, indicating immunity against RMA tumor antigens. ChNKG2D T cell–derived IFN-γ and granulocyte-macrophage colony–stimulating factor, but not perforin (Pfp), tumor necrosis factor–related apoptosis-inducing ligand, or Fas ligand (FasL) alone were critical for in vivo efficacy. T cells deficient in both Pfp and FasL did not kill NKG2D ligand–positive RMA cells in vitro. Adoptive transfer of Pfp−/−FasL−/− chNKG2D T cells had reduced in vivo efficacy, indicating that chNKG2D T cells used both mechanisms to attack RMA/Rae1 cells. Taken together, these results indicate that chNKG2D T-cell–mediated therapeutic effects are mediated by both cytokine-dependent and cytotoxic mechanisms in vivo. [Cancer Res 2007;67(22):11029–36]
Metformin Inhibits Mammalian Target of Rapamycin–Dependent Translation Initiation in Breast Cancer Cells
Authors: Dowling Ryan J.O. , Zakikhani Mahvash , Fantus I. George , Pollak Michael , Sonenberg Nahum
Published: November 2007

Metformin is used for the treatment of type 2 diabetes because of its ability to lower blood glucose. The effects of metformin are explained by the activation of AMP-activated protein kinase (AMPK), which regulates cellular energy metabolism. Recently, we showed that metformin inhibits the growth of breast cancer cells through the activation of AMPK. Here, we show that metformin inhibits translation initiation. In MCF-7 breast cancer cells, metformin treatment led to a 30% decrease in global protein synthesis. Metformin caused a dose-dependent specific decrease in cap-dependent translation, with a maximal inhibition of 40%. Polysome profile analysis showed an inhibition of translation initiation as metformin treatment of MCF-7 cells led to a shift of mRNAs from heavy to light polysomes and a concomitant increase in the amount of 80S ribosomes. The decrease in translation caused by metformin was associated with mammalian target of rapamycin (mTOR) inhibition, and a decrease in the phosphorylation of S6 kinase, ribosomal protein S6, and eIF4E-binding protein 1. The effects of metformin on translation were mediated by AMPK, as treatment of cells with the AMPK inhibitor compound C prevented the inhibition of translation. Furthermore, translation in MDA-MB-231 cells, which lack the AMPK kinase LKB1, and in tuberous sclerosis complex 2 null (TSC2−/−) mouse embryonic fibroblasts was unaffected by metformin, indicating that LKB1 and TSC2 are involved in the mechanism of action of metformin. These results show that metformin-mediated AMPK activation leads to inhibition of mTOR and a reduction in translation initiation, thus providing a possible mechanism of action of metformin in the inhibition of cancer cell growth. [Cancer Res 2007;67(22):10804–12]
Characterization of a Novel Tumor-Suppressor Gene PLCδ1 at 3p22 in Esophageal Squamous Cell Carcinoma
Authors: Fu Li , Qin Yan-Ru , Xie Dan , Hu Liang , Kwong Dora L. , Srivastava Gopesh , Tsao Sai Wah , Guan Xin-Yuan
Published: November 2007

Deletion of 3p is one of the most frequent chromosomal alterations in many solid tumors, including esophageal squamous cell carcinoma (ESCC), suggesting the existence of one or more tumor-suppressor genes at 3p. Recently, our loss of heterozygosity study revealed that 3p22 was frequently deleted in ESCC and a candidate tumor-suppressor gene (TSG), phospholipase C-δ1 (PLCδ1), was identified within the 3p22 region. In this study, absent expression of PLCδ1 was detected in 26 of 50 (52%) primary ESCCs and 4 of 9 (44.4%) ESCC cell lines, which was significantly associated with DNA copy number loss and promoter hypermethylation (P < 0.05). Functional studies showed that PLCδ1 was able to suppress both in vitro and in vivo tumorigenic ability of ESCC cells, including foci formation, colony formation in soft agar, and tumor formation in nude mice. The tumor-suppressive mechanism of PLCδ1 was associated with its role in the cell cycle arrest at the G1-S checkpoint by up-regulation of p21 and down-regulation of phosphorylated Akt (Ser473). In addition, down-regulation of PLCδ1 protein was significantly correlated with ESCC metastasis (P = 0.014), which was associated with its function in increasing cell adhesion and inhibiting cell mobility. Taken together, our results suggest that PLCδ1 plays an important suppressive role in the development and progression of ESCC. [Cancer Res 2007;67(22):10720–5]
A Polycomb Repression Signature in Metastatic Prostate Cancer Predicts Cancer Outcome
Authors: Yu Jindan , Yu Jianjun , Rhodes Daniel R. , Tomlins Scott A. , Cao Xuhong , Chen Guoan , Mehra Rohit , Wang Xiaoju , Ghosh Debashis , Shah Rajal B. , Varambally Sooryanarayana , Pienta Kenneth J. , Chinnaiyan Arul M.
Published: November 2007

The Polycomb Group (PcG) protein EZH2 is a critical component of a multiprotein complex that methylates Lys27 of histone 3 (H3K27), which consequently leads to the repression of target gene expression. We have previously reported that EZH2 is overexpressed in metastatic prostate cancer and is a marker of aggressive diseases in clinically localized solid tumors. However, the global set of genes directly regulated by PcG in tumors is largely unknown, and thus how PcG mediates tumor progression remains unclear. Herein we mapped genome-wide H3K27 methylation in aggressive, disseminated human prostate cancer tissues. Integrative analysis revealed that a significant subset of these genes are also targets of PcG in embryonic stem cells, and their repression in tumors is associated with poor prognosis. By stepwise cross-validation, we developed a “Polycomb repression signature” composed of 14 direct targets of PcG in metastatic tumors. Notably, solid tumor subtypes in which this gene signature is repressed show poor clinical outcome in multiple microarray data sets of tumors including breast and prostate cancer. Taken together, our results show a fingerprint of PcG-mediated transcriptional repression in metastatic prostate cancer that is reminiscent of stem cells and associated with cancer progression. Therefore, PcG proteins play a central role in the epigenetic silencing of target genes and functionally link stem cells, metastasis, and cancer survival. [Cancer Res 2007;67(22):10657–63]
Deregulated Activity of Akt in Epithelial Basal Cells Induces Spontaneous Tumors and Heightened Sensitivity to Skin Carcinogenesis
Authors: Segrelles Carmen , Lu Jerry , Hammann Brian , Santos Mirentxu , Moral Marta , Cascallana José Luis , Lara M. Fernanda , Rho Okkyung , Carbajal Steve , Traag Jeanine , Beltrán Linda , Martínez-Cruz Ana Belén , García-Escudero Ramón , Lorz Corina , Ruiz Sergio , Bravo Ana , Paramio Jesús M. , DiGiovanni John
Published: November 2007

Aberrant activation of the phosphoinositide-3-kinase (PI3K)/PTEN/Akt pathway, leading to increased proliferation and decreased apoptosis, has been implicated in several human pathologies including cancer. Our previous data have shown that Akt-mediated signaling is an essential mediator in the mouse skin carcinogenesis system during both the tumor promotion and progression stages. In addition, overexpression of Akt is also able to transform keratinocytes through transcriptional and posttranscriptional processes. Here, we report the consequences of the increased expression of Akt1 (wtAkt) or constitutively active Akt1 (myrAkt) in the basal layer of stratified epithelia using the bovine keratin K5 promoter. These mice display alterations in epidermal proliferation and differentiation. In addition, transgenic mice with the highest levels of Akt expression developed spontaneous epithelial tumors in multiple organs with age. Furthermore, both wtAkt and myrAkt transgenic lines displayed heightened sensitivity to the epidermal proliferative effects of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) and heightened sensitivity to two-stage skin carcinogenesis. Finally, enhanced susceptibility to two-stage carcinogenesis correlated with a more sustained proliferative response following treatment with TPA as well as sustained alterations in Akt downstream signaling pathways and elevations in cell cycle regulatory proteins. Collectively, the data provide direct support for an important role for Akt signaling in epithelial carcinogenesis in vivo, especially during the tumor promotion stage. [Cancer Res 2007;67(22):10879–88]
Frequent Loss of Brm Expression in Gastric Cancer Correlates with Histologic Features and Differentiation State
Authors: Yamamichi Nobutake , Inada Ken-ichi , Ichinose Masao , Yamamichi-Nishina Mitsue , Mizutani Taketoshi , Watanabe Hirotaka , Shiogama Kazuya , Fujishiro Mitsuhiro , Okazaki Takuya , Yahagi Naohisa , Haraguchi Takeshi , Fujita Shuji , Tsutsumi Yutaka , Omata Masao , Iba Hideo
Published: November 2007

The mammalian SWI/SNF chromatin remodeling complex, an essential epigenetic regulator, contains either a single Brm or BRG1 molecule as its catalytic subunit. We observed frequent loss of Brm expression but not of BRG1 in human gastric cancer cell lines. Treatment with histone deacetylase inhibitor rescued Brm expression, indicating epigenetic regulation of this gene, and an RNA interference–based colony formation assay revealed antioncogenic properties of Brm. Brm immunostaining of 89 primary gastric cancers showed an obvious reduction in 60 cases (67%) and a severe decrease in 37 cases (42%). Loss of Brm is frequent in the major gastric cancer types (well- or moderately-differentiated tubular adenocarcinoma and poorly-differentiated adenocarcinoma) and positively correlates with the undifferentiated state. Among the minor gastric cancer types, Brm expression persists in signet-ring cell carcinoma and mucinous adenocarcinoma, but a marked decrease is observed in papillary adenocarcinoma. Intestinal metaplasia never shows decreased expression, indicating that Brm is a valid marker of gastric oncogenesis. In contrast, BRG1 is retained in most cases; a concomitant loss of BRG1 and Brm is rare in gastric cancer, contrary to other malignancies. We further show that Brm is required for villin expression, a definitive marker of intestinal metaplasia and differentiation. Via regulating such genes important for gut differentiation, Brm should play significant roles in determining the histologic features of gastric malignancy. [Cancer Res 2007;67(22):10727–35]