1,720,960 research outputs found
Abstract 4500: Inhibition of PERK by small molecule inhibitors enhances the response to ionizing radiation in vitro and animal tumor models
No full textAbstract
Endoplasmic reticulum (ER) is a well organized membranous network, responsible for synthesis and folding of secretory and membrane proteins, lipid and sterol biosynthesis and intracellular calcium storage. Perturbations in ER lumen caused by depletion of Ca2+ levels, hypoxia, nutrient deprivation, affect the ER homeostasis, a condition known as an ER stress. In order to cope with this stress, cells have developed an orchestrated biochemical response, termed Unfolded Protein Response (UPR). Hypoxia, an ER stress inducer, is an important and unique characteristic of the solid tumor microenvironment, promotes resistance to radiotherapy and contributes to poor patient prognosis. Cancer cells overcome these stress conditions through activation the PERK-eIF2α arm of the UPR, leading to inhibition of global protein synthesis and cell survival. We hypothesize that the use of small molecule PERK inhibitors will decrease the survival of hypoxic cells and eventually sensitize them to irradiation. In this study we used highly radioresistant melanoma and head and neck squamous cell carcinoma cell lines B16F10-ova and SQ20B, under nomroxia and hypoxia, respectively. We used two specific PERK inhibitors (PERKi) and tested for their efficacy both in vitro and in vivo. Induction of ER stress in both cell lines, either by treatment with the pharmacologic agents thapsigargin (TG) and tunicamycin (TN), or by exposure to hypoxic conditions (0.2%), was evaluated by activation of PERK and its downstream targets. Pre-treatment of stressed B16F10-ova and SQ20B cells for 2h with PERKi (1μM), caused complete inhibition of PERK-eIF2a-ATF4-CHOP arm of the UPR. Moreover, both cell lines pre-treated with PERKi presented a significant decrease in survival fraction under ER-stress induced by TG (0.5μM) as well as under hypoxia (0.2%) along with increasing doses of irradiation (IR). For the in vivo experiments, nude and C57BL/6 mice were treated with either 100mg/kg of PERKi by oral gavage, twice a day for 3weeks, or IR or a combination of PERKi and IR. Mice treated with PERKi showed a small but not significant delay of tumor growth in both backgrounds of mice. However, combined treatment with IR (12 and 15Gy) caused a significant reduction of tumor volume as well as a delayed tumor growth which was significantly more pronounced in the immunocompetent mice. Data from flow cytometry analysis of one of the the PERKi+IR treated tumors from C57BL/6 mice showed that there is a significant infiltration of CD3+ cells as well as significant higher number of CD3+CD8+ cells compared to the untreated mice or mice treated with either PERKi or IR alone. Collectively, our results show that PERKi effectively reduces the survival of hypoxic B16F10-ova and SQ20B cells and sensitize them to IR in vitro and in tumors. Further experiments will clarify whether PERKi have a dual role on reducing the hypoxic fraction and direct recruitment of the cytotoxic T-cells.
Citation Format: Ioannis Verginadis, Joel Encarnación, Souvik Dey, Constantinos Koumenis. Inhibition of PERK by small molecule inhibitors enhances the response to ionizing radiation in vitro and animal tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4500. doi:10.1158/1538-7445.AM2017-4500</jats:p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Abstract 5863: Identifying the radiosensitizing effects of PARP inhibitor in ovarian cancer
No full textAbstract
Ovarian cancer is the seventh-most common cancer with a high mortality rate among women. Radiation therapy (RT) is used in ovarian cancer for local relapse, but doses are limited due to concern for small bowel obstruction in patients who have had multiple surgeries and chemotherapeutic regimens. Therefore, it’s an ideal setting to improve the therapeutic window by combining RT and a radiosensitizer. Poly (ADP-ribose) polymerase-1 (PARP-1) is involved in the recognition of DNA damage and the facilitation of DNA repair by recognizing DNA single-strand breaks (SSB). Inhibition of PARP1, especially in tumors driven by BRCA1 or 2 mutations, has been shown to potentiate the DNA-damaging effects of radiation in vitro and in vivo and to increase tumor vasculature perfusion and oxygenation. Approximately half of ovarian cancers have germline or somatic BRCA gene mutation, epigenetic silencing or other mutations that affect homologous recombination (HR) competency resulting in DNA repair defects, making this tumor particularly susceptible to the radiation-sensitizing effects of PARP inhibitors. Here, we investigated the therapeutic effects of the PARP inhibitor olaparib in preclinical models of ovarian cancer. Basic BRCA1 and PARP1 protein and mRNA levels were characterized in a panel of ovarian cancer cell lines. The radiosensitizing effects of olaparib were tested on both HR-proficient and HR-deficient ovarian cancer cells by evaluating the colony formation, DNA damage, apoptosis, and PARP1 activity. Survival benefit of olaparib was also examined in xenograft models of ovarian cancer. Our results demonstrate that combination of olaparib with IR decreased colony formation, inhibited DNA damage (γH2AX) repair, and induced more apoptosis compared to olaparib or IR alone. In addition, HR-deficient cells were more sensitive to IR than HR-proficient cells in the presence of olaparib. Furthermore, olaparib inhibited PARP1 activity in vivo, significantly decreased tumor growth and increased overall survival when combined with IR in mice bearing subcutaneous xenografts of HR-deficient OVCAR8 cells while producing a relative modest effect on overall survival of mice bearing xenografts of HR-proficient SKOV3 cells. These results provide a preclinical rationale for improved treatment modalities using olaparib as an effective radiosensitizer in ovarian cancer, particularly in tumors with HR-deficiencies.
Citation Format: Yue Bi, Ioannis Verginadis, Souvik Dey, linlang Guo, Lilie Lin, Yanfang Zheng, Constantinos Koumenis. Identifying the radiosensitizing effects of PARP inhibitor in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5863. doi:10.1158/1538-7445.AM2017-5863</jats:p
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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