published_or_final_version / abstract / Surgery / Doctoral / Doctor of Philosophy

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Celecoxib is a COX-2 selective non-steroidal anti-inflammatory drug which has been shown to inhibit growth and induce apoptosis in various cancer cell lines. Using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and an apoptosis detection kit, we demonstrated that celecoxib was able to induce growth inhibition and apoptosis in a dose-dependent manner in 3 NPC cell lines: HK-1, Hone-1, and C666-1. Afterwards, a proteomic approach was used to study the underlying mechanisms involved in celecoxib-mediated effects on two COX-2 positive NPC cell lines (HK-1 and C666-1). Results showed that a total of 18 protein spots were differentially expressed in the HK-1 and C666-1 cells. On the other hand, we also compared the proteomic expression profile between an NPC cell line (C666-1) and a normal nasopharynx cell line (NP69) in order to study whether those differentially expressed proteins after celecoxib treatment were also involved in NPC carcinogenesis. Proteomics results with confirmation using Western blotting discovered that HSP27 phosphorylated of serine 82 (HSP27-pSer82) protein was up-regulated in C666-1 cells when compared with that in NP69 cells. After treatment with celecoxib, expression of HSP27-pSer82 protein was down-regulated in both HK-1 and C666-1 cells. These findings suggest that down-regulation of HSP27-pSer82 protein expression may have mediated the growth-inhibitory effects of celecoxib in HK-1 and C666-1 cells. Finally, other differential expressed proteins identified from proteomics with confirmation by immunocytochemical staining in the 2 NPC cell lines and 40 NPC patient specimens showed that down-regulation of annexin 2 and beta2-tubulin may be important in NPC formation. / COX-2 over-expression has been found in various cancers such as colorectal cancer, liver cancer and lung cancer. In vivo studies have shown that mice overexpressing COX-2 developed breast cancer whereas COX-2 knockout mice had reduced rates of cancer formation in the intestines and skin. In the present study, COX-2 expression in NPC patient biopsies was examined and correlated with the clinicopathological data of the patients. Immunocytochemical staining showed that COX-2 protein was over-expressed in 84.6% (66/78) of non-metastatic NPC patients and was associated with an advanced nodal stage (P<0.05). All these data support an important role for COX-2 in NPC pathogenesis. / In summary, this study is the first to identify HSP27-pSer82 protein as a potential target of celecoxib in NPC cells. Detailed investigations of the functional role of molecular targets identified in this study would improve our understanding of the chemotherapeutic effects of celecoxib and, in the long run, may lead to a more effective chemotherapeutic treatment to this common cancer. / Nasopharyngeal carcinoma (NPC) is prevalent in southern China. Although early stage patients have a high rate of cure with radiotherapy alone, the prognosis for those with stage III or IV disease remains poor due to subsequent development of distant metastases. Therefore there is an urgent need to develop novel biologic agents to improve treatment outcomes. / Chan, Ming Lok. / Adviser: Anthony T.C. Chan. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3418. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 141-171). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

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High output of prostaglandins (PGs) are the hallmark of inflammatory and immune reactions. A rate-limiting step in the production of PGs is the presence of the enzyme cyclooxygenase (COX). COX exists as two isoforms: COX-1 which is constitutively expressed in most cells and COX-2 which is inducible by LPS, proinflammatory cytokines and other stimuli in cells involved in inflammation. The objective of this study was to determine the effect of nonsteroidal antiinflammatory drugs and proinflammatory cytokines on COX-2 expression in human macrophages. COX-2 specific (NS-398) and non-specific (aspirin, indomethacin and naproxen) inhibitors showed no effect on COX mRNA and protein expression induced by LPS. In contrast, the drugs markedly inhibited COX activity as measured by the accumulation of PGE2. The induction of COX-2 mRNA expression by LPS was rapid and sustained. However, LPS only transiently stimulated the transcription of COX-2 gene and activation of the transcription factor NF-kappaB. LPS stimulated the release of IL-1beta and TNF-alpha but these cytokines had no autocrine effect on the transcriptional or post-transcriptional regulation of COX-2. The presence of LPS was essential for the maintenance of high levels of long-lived COX-2 mRNA. As IFN-gamma is a major macrophage activating factor, we determined the role of this cytokine on COX-2 expression induced by exogenous IL-1beta. IFN-gamma-primed macrophages showed significantly lower levels of COX-2 mRNA, protein and PGE2 production compared to non-primed cells. IFN-gamma specifically decreased the transcriptional activation of COX-2 gene by IL-1beta but not by LPS without affecting the rate of mRNA decay. These results demonstrate that sustained production of PGE2 by macrophages in an inflammatory milieu can occur through the stabilization of COX-2 mRNA and revealed a role for IFN-gamma as an anti-inflammatory cytokine counteracting the expression of COX-2. A better understanding of COX-2 regulation will

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly worldwide. Due to the inadequacy of current pharmacotherapies, novel molecular targets must be sought as potential therapeutic candidates. Furthermore, there is a need for more efficient and cost-effective animal models of this pathology in order to accelerate in vivo investigations. / Our laboratory is in possession of human choroidal neovascular membranes which we examined for expression of cyclooxygenase (COX)-2. This expression was characterized in retinal pigment epithelial, vascular endothelial, and fibroblast cells and correlated with patient age. We also looked at the feasibility of creating a rabbit laser-injury model to adequately mimic human neovascular AMD. / Our results suggest that anti-COX-2 therapies may be beneficial to some patients with neovascular AMD. Moreover, there is strong potential for the development of clinically relevant choroidal neovascularization in rabbits using the laser-injury technique. This approach may yield a novel, cost-effective AMD model.

We have previously shown that non-specific blockade of the cyclooxygenase (COX) enzymes in skeletal muscle eliminates the normal increase in muscle protein synthesis following resistance exercise. The current study tested the hypothesis that this COX-mediated increase in postexercise muscle protein synthesis is specifically regulated by the COX-2 isoform. Sixteen males (23 ± 1 yr, 177 ± 2 cm, 81.5 ± 3.4 kg) were randomly assigned to one of two groups that received three doses of either a specific COX-2 inhibitor (celecoxib; 200 mg per dose, 600 mg total) or a placebo during the 24 hours following a single bout of resistance exercise with the knee extensors. Skeletal muscle fractional synthesis rate (FSR) was measured at rest and 24 hours postexercise using a primed constant infusion of [2H5]phenylalanine coupled with muscle biopsies of the vastus lateralis. Mixed muscle FSR was increased following exercise to a greater extent (206%, P<0.05) in the COX-2 group (0.052 ± 0.014 %Ih) as compared with the placebo group (0.017 ± 0.007 %Ih). These results suggest that the specific inhibition of the COX-2 isoform in human skeletal muscle causes a compensatory response in muscle protein synthesis. These data also highlight the involvement of the cyclooxygenase pathways in the regulation of muscle protein synthesis following resistance exercise. / School of Physical Education, Sport, and Exercise Science

Diss. (sammanfattning) Göteborg : Univ. , 2007. / Härtill 4 uppsatser.

Thesis (M.Sc.). / Written for the Dept. of Epidemiology, Biostatistics and Occupational Health. Title from title page of PDF (viewed 2008/07/30). Includes bibliographical references.