A comprehensive immunohistochemical study was carried out to investigate the phenotypes and prevalence of intraepithelial lymphocytes in NPC samples semi-quantitatively. CD25+/FOXP3+ T-cells were highly prevalent in primary NPCs, suggesting the presence of the immunosuppressive Tregs in tumor microenvironments. The low abundance of CD4+ T-cells, and the positive correlation between FOXP3 and CD8 staining in NPC samples imply that CD8+FOXP3+ Tregs may be present and play role in the suppression of anti-tumor immune response in NPC patients. The involvement of chemokine in the migration of tumor-infiltrating lymphocytes was studied. Chemokine ligand 20 (CCL20) was overexpressed in all EBV-positive NPC cell lines and xenografts compared to EBV-negative NPC, and immortalized normal nasopharynx epithelial cell lines. The presence of CCL20 was also found in primary tumors but not in normal epithelium. Furthermore, the ability of LMP1 to upregulate CCL20 expression in epithelial cells indicates that EBV may induce the production of chemokine involved in lymphocyte migration. / Epstein-Barr virus (EBV) is invariably associated with the development of nasopharyngeal carcinoma (NPC). Although the association of EBV and cancer has been reported for about four decades, it is still not clear how EBV latent infection contributes to the transformation of nasopharyngeal epithelial cells. The aims of this study are to identify EBV-regulated cellular genes and pathways and to determine the potential role of EBV in the modulation of anti-tumor immune responses in NPC. / In summary, EBV plays critical roles in the development of NPC by regulation of multiple cellular genes and pathways such as the Notch signaling cascade, and modulation of anti-tumor immune responses through the induction of chemokine important in migration of immune cells. / Notch signaling pathway functions in diverse cellular processes such as proliferation, apoptosis, adhesion, and epithelial to mesenchymal transition. In the current study, aberrant expression of activated Notch1 receptor (NICD), Notch ligand (Jagged1), negative regulator of Notch ( NUMB) and Notch downstream effector (HEY1) was detected in NPC cell lines and xenografts. Overexpression of NICD, Jagged1 and HEY1 proteins was also commonly found in primary tumors of NPC. / Transfection of Jagged1 to normal nasopharynx epithelial cells resulted in increased cell proliferation. Moreover, EBERs, which is abundantly expressed in EBV-positive NPC tumors, was capable of inducing the expression of Jagged1 in epithelial cells. The current data shows that Notch signaling pathway is aberrantly activated by the deregulated expression of multiple Notch components in NPC. The induction of Jagged1 by EBERs also implies the potential role of EBV in the activation of Notch signaling cascade in NPC. / Using high-density oligonucleotide microarray, expression profiles of EBV-infected NPC cell lines, HK1+EBV and HONE1+EBV, and their uninfected counterparts, HK1 and HONE, were generated. From the microarray results, six EBV-upregulated (JDP2, IL8, ATP6V0E2L, PLAP, PIK3C2B and AKR1B10 ) and three EBV-downregulated genes (BACE2, PADI3 and MMP1) were identified in both HK1 and HONE1 cells upon EBV latent infection. One hundred and thirty-eight and seventy-six genes were also found to be differentially modulated by EBV in HK1 and HONE1 cells, respectively. This study shows that cellular genes involved in wide range of biological processes and cellular functions are differentially regulated by EBV, which suggest that EBV modulates multiple pathways and processes during NPC tumorigenesis. / Hui, Wai Ying. / Adviser: Kw Lo. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0806. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 166-204). / 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. / Abstract also in Chinese. / School code: 1307.

Cheung Mei-chun. / "January 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (p. 66-94). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

This thesis is the construct of a computational system for studying the nasopharyngeal carcinoma (NPC) using high-throughput sequencing data. The system involves several components, including discovery of gene fusion in NPC cell line, construction of Esptein-Barr virus (EBV) genome, and evaluation on contaminated sequencing data alignment approaches. We successfully discovered a gene fusion (UBR5-ZNF423) in a NPC cell line (C666-1) which was verified by lab experiments and found in 8.3% of primary tumors. It was discovered the regulation of this gene affect the growth of cancer cell. We constructed the EBV genome in C666-1. It serves as an important reference for studying this important NPC cell line, which was the only NPC cell line in the world for a long time. We also evaluated three mapping approaches. Two of them are designed to filter out potential mouse contamination reads on human sequencing data, which can originate from NPC human-in-mouse xenografts. We found that special care should always be applied to contaminated data. Although direct mapping can give acceptable results if in most cases, the combined-based approached is suggested. It can effectively reduce false positive variants and maintain good enough numbers of true positive variants. Filtering approach is an alternative to the combined-based approach that can also effectively reduce contamination when memory is not sufficient. / 本論文利用電腦有系統地研究鼻咽癌，當中的數據利用了高通量測序技術來定序。其中章節包括在鼻咽癌胞系中尋找融合基因、組建潛藏於人體可引致鼻咽癌的EB病毒基因組、還有評價幾種可處理受污染序列的序列排列方法。我們成功地在鼻咽癌胞系（C666-1）中發現出一個融合基因（UBR5-ZNF423），並在實驗中確定此成果，其中發現在原發腫瘤中有8.3%的樣本中找出此融合基因。此外，也發現這融合基因調控會影響到癌細胞的生長。C666-1鼻咽癌胞系在過往有一段很長的時間裡，都是全世界唯一的鼻咽癌胞系，因此它有非常重要的參考價值，在此研究，我們組建了在C666-1裡的EB病毒基因組，使它作為研究C666-1的參考樣本。另外，我們評價了三種處理排列的方法，其中兩種的設計能過濾部分人類序列數據當中老鼠基因組的污染，老鼠基因組的污染可以來自於異種移植，即把人類癌細腫瘤移植於老鼠身上種植，我們建議在情況許可下都使用特殊的處理方法而不是直接作序列排列。直接作序列排列數據雖然已有合理的表現，但相比之下組合基因組式序列排列方法能有效減少錯誤肯定的遺傳變異，並同時保留足夠多正確肯定的遺傳變異，所以組合基因組式序列排列方法應在情況許可下都使用它。過濾式序列排列方法也是一種特殊的處理方法，它也能有效減少錯誤肯定的遺傳變異，它對記憶體的需求比組合基因組式序列排列方法少，可在電腦的記憶體不足時使用它。 / Tso, Kai Yuen. / Thesis M.Phil. Chinese University of Hong Kong 2014. / Includes bibliographical references (leaves 112-120). / Abstracts also in Chinese. / Title from PDF title page (viewed on 24, October, 2016). / Detailed summary in vernacular field only.

Choi, Pui Ying. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 101-122). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.

Xu, Meng. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 112-129). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Wang, Yajun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 118-126). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.v / Table of Contents --- p.vi / List of Figures --- p.xi / List of Tables --- p.xii / Abbreviations and Symbols --- p.xiii / List of Publications and Sequence Submissions during the Study --- p.xv / Chapter Chapter One: --- General Introduction --- p.1 / Chapter Chapter Two: --- Literature Review --- p.8 / Chapter 2.1 --- DNA methylation --- p.8 / Chapter 2.1.1 --- Epigenetic changes --- p.8 / Chapter 2.1.2 --- Differential methylation pattern in normal and tumor cells --- p.10 / Chapter 2.2 --- TSGs --- p.13 / Chapter 2.2.1 --- "Cancer initiation, progression and cancer genes" --- p.13 / Chapter 2.2.2 --- TSGs could be inactivated through promoter hypermethylation --- p.14 / Chapter 2.3 --- NPC --- p.17 / Chapter 2.3.1 --- Epidemiology ofNPC --- p.18 / Chapter 2.3.2 --- Molecular genetic and epigenetic studies ofNPC --- p.19 / Chapter 2.3.3 --- NPC and chromosome 11q --- p.21 / Chapter 2.4 --- ESCC --- p.21 / Chapter 2.4.1 --- Epidemiology of ESCC --- p.22 / Chapter 2.4.2 --- Genetic and epigenetic studies of ESCC --- p.23 / Chapter 2.4.3 --- ESCC and chromosome 11q --- p.24 / Chapter 2.5 --- Chromosome 11q and other carcinomas --- p.24 / Chapter 2.5.1 --- Breast cancer --- p.24 / Chapter 2.5.2 --- Ovarian cancer --- p.25 / Chapter 2.5.3 --- Neuroblastoma --- p.26 / Chapter 2.5.4 --- Melanoma --- p.27 / Chapter 2.5.5 --- Multiple myeloma --- p.27 / Chapter 2.5.6 --- Lung Cancer --- p.27 / Chapter 2.6 --- Important candidate genes located at the project study 1 lq region --- p.28 / Chapter 2.6.1 --- ETS1 --- p.28 / Chapter 2.6.2 --- FLI1 --- p.29 / Chapter 2.6.3 --- P53AIP1 --- p.30 / Chapter 2.6.4 --- RICS --- p.30 / Chapter 2.6.5 --- BARX2 --- p.30 / Chapter 2.6.6 --- ST14 --- p.32 / Chapter 2.6.7 --- ADAMTS8 --- p.33 / Chapter 2.6.8 --- ADAMTS15 --- p.35 / Chapter 2.6.9 --- HNT --- p.36 / Chapter 2.6.10 --- OPCML --- p.36 / Chapter Chapter Three: --- Materials and Methods --- p.37 / Chapter 3.1 --- Cell lines and primary tumor samples --- p.37 / Chapter 3.2 --- Cell line demethylation treatment --- p.38 / Chapter 3.3 --- DNA and RNA extraction from cell lines and tissues --- p.39 / Chapter 3.4 --- Semiquantitative RT-PCR --- p.41 / Chapter 3.5 --- DNA bisulfite treatment --- p.42 / Chapter 3.6 --- Promoter analysis and identification of 5' CpG islands of target genes --- p.45 / Chapter 3.7 --- Methylation-Specific PCR (MSP) --- p.45 / Chapter 3.8 --- Bisulfite Genomic Sequencing (BGS) --- p.46 / Chapter 3.8.1 --- BGS PCR reaction --- p.46 / Chapter 3.8.2 --- TA cloning of the PCR products into the sequencing vector --- p.47 / Chapter 3.8.3 --- Plasmid mini-preparation on 96-well plate --- p.48 / Chapter 3.8.4 --- Plasmid sequencing --- p.49 / Chapter 3.9 --- Homozygous deletion detection --- p.50 / Chapter 3.10 --- Construction of expression plasmids --- p.51 / Chapter 3.10.1 --- The strategy of full length cDNA cloning --- p.51 / Chapter 3.10.2 --- Obtaining of full length covered cDNA by cloning PCR --- p.53 / Chapter 3.10.3 --- Ligation and transformation --- p.54 / Chapter 3.10.4 --- Mini preparation of plasmid in Eppendorf tubes --- p.54 / Chapter 3.10.5 --- Verification of correct inserts in the plasmid --- p.55 / Chapter 3.10.6 --- Subcloning --- p.55 / Chapter 3.10.7 --- Bacteria storage --- p.57 / Chapter 3.11 --- Colony formation assays (CFA) --- p.57 / Chapter 3.11.1 --- Midiprep of the transfection grade plasmid --- p.57 / Chapter 3.11.2 --- Transfection --- p.58 / Chapter 3.11.3 --- Selection of the transfected cells with G418 --- p.59 / Chapter 3.11.4 --- Colony staining --- p.60 / Chapter 3.12 --- Statistical analysis --- p.60 / Chapter Chapter Four: --- Results --- p.61 / Chapter 4.1 --- Narrow down the candidate genes for further study --- p.61 / Chapter 4.1.1 --- Define the study chromosome region --- p.61 / Chapter 4.1.2 --- Database search of all candidate genes --- p.61 / Chapter 4.1.3 --- Transcriptional expression analysis of the candidate genes --- p.63 / Chapter 4.1.4 --- Selection of the genes with tumor specific expression downregulation for further intensive study --- p.64 / Chapter 4.2 --- Further characterization of ADAMTS8 --- p.69 / Chapter 4.2.1 --- Tissue transcriptional expression panel --- p.69 / Chapter 4.2.2 --- Semiquantitative RT-PCR results in tumor cell lines --- p.70 / Chapter 4.2.3 --- Promoter CpG island identification and promoter methylation study --- p.70 / Chapter 4.2.4 --- Transcription reactivation by demethylation treatment --- p.72 / Chapter 4.2.5 --- High resolution promoter methylation analysis by BGS --- p.72 / Chapter 4.2.6 --- Detection of homozygous deletion --- p.73 / Chapter 4.2.7 --- Analysis of ADAMTS8 promoter methylation in clinical samples --- p.74 / Chapter 4.2.8 --- ADAMTS8 full length cDNA cloning --- p.74 / Chapter 4.2.9 --- Colony formation assay --- p.75 / Chapter 4.3 --- Further characterization of HNT --- p.80 / Chapter 4.3.1 --- Tissue transcriptional expression panel --- p.80 / Chapter 4.3.2 --- Semiquantitative RT-PCR results in tumor cell lines --- p.80 / Chapter 4.3.3 --- Promoter CpG island identification and promoter methylation study --- p.81 / Chapter 4.3.4 --- Transcription reactivation by demethylation treatment --- p.82 / Chapter 4.3.5 --- HNT full length cDNA cloning --- p.82 / Chapter 4.4 --- Further characterization of BARX2 --- p.87 / Chapter 4.4.1 --- Tissue transcriptional expression panel --- p.87 / Chapter 4.4.2 --- Semiquantitative RT-PCR results in tumor cell lines --- p.87 / Chapter 4.4.3 --- Promoter CpG island identification and promoter methylation study --- p.88 / Chapter 4.4.4 --- Transcription reactivation by demethylation treatment --- p.89 / Chapter 4.4.5 --- BARX2 full length cDNA cloning --- p.89 / Chapter 4.5 --- Further study of other downregulated genes --- p.92 / Chapter 4.5.1 --- FLII --- p.92 / Chapter 4.5.2 --- ADAMTS15 --- p.94 / Chapter 4.5.3 --- P53AIP1 --- p.97 / Chapter Chapter Five: --- Discussion --- p.100 / Reference List --- p.118 / Appendix I: Reagents Preparation Recipe --- p.127 / Appendix II: PCR Primers for cDNA Cloning --- p.129

Lou, Pak Kin. / Thesis (M.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 136-170). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.v / Table of Contents --- p.vi / List of Figures --- p.x / List of Tables --- p.xiii / List of Publications --- p.xv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1. --- Aims of Study --- p.1 / Chapter 1.2. --- Literature Review --- p.2 / Chapter 1.2.1. --- Nasopharyngeal Carcinoma --- p.2 / Chapter 1.2.1.1. --- Overview --- p.2 / Chapter 1.2.1.2. --- Histopathology --- p.2 / Chapter 1.2.1.3. --- Epidemiology --- p.3 / Chapter 1.2.1.4. --- Etiology --- p.5 / Chapter 1.2.1.4.1. --- Epstein-Barr Virus (EBV) Latent Infection --- p.5 / Chapter 1.2.1.4.2. --- Environmental Factors --- p.5 / Chapter 1.2.1.4.3. --- Genetic Factors --- p.6 / Chapter 1.2.1.5. --- Molecular Pathogenesis --- p.7 / Chapter 1.2.1.5.1. --- Chromosomal Alterations --- p.7 / Chapter 1.2.1.5.2. --- NPC-associated Tumour Suppressor Genes --- p.7 / Chapter 1.2.1.5.3. --- NPC-associated Oncogenes --- p.8 / Chapter 1.2.2. --- Epstein-Barr Virus --- p.9 / Chapter 1.2.2.1. --- Overview --- p.9 / Chapter 1.2.2.2. --- Lytic and Latent Infection of EBV --- p.9 / Chapter 1.2.2.3. --- EBV Latency Programs and Associated --- p.10 / Malignancies --- p.11 / Chapter 1.2.2.4. --- The Role of EBV in NPC --- p.12 / Chapter 1.2.3. --- NF-kB Signalling Pathways --- p.12 / Chapter 1.2.3.1. --- Overview --- p.12 / Chapter 1.2.3.2. --- Pathway Components --- p.12 / Chapter 1.2.3.2.1. --- NF-kB Subunits --- p.16 / Chapter 1.2.3.2.2. --- Inhibitors of kB (IkBs) --- p.16 / Chapter 1.2.3.2.3. --- IkB Kinases (IKKs) --- p.17 / Chapter 1.2.3.3. --- NF-kB Activation and Signalling --- p.17 / Chapter 1.2.3.3.1. --- The Canonical Pathway --- p.18 / Chapter 1.2.3.3.2. --- The Non-canonical Pathway --- p.18 / Chapter 1.2.3.3.3. --- Physiological Functions of NF-kB --- p.19 / Chapter 1.2.3.4. --- NF-kB Signalling and Tumourigenesis --- p.20 / Chapter 1.2.3.4.1. --- Oncogenic Activation of NF-kB in Hematological Malignancies --- p.20 / Chapter 1.2.3.4.2. --- Oncogenic Activation of NF-kB in Solid and Epithelial Tumours --- p.22 / Chapter Chapter 2 --- Material and Methods --- p.22 / Chapter 2.1. --- Tumour Specimens --- p.24 / Chapter 2.2. --- NPC Tumour Lines and Immortalized NP Cell Lines --- p.24 / Chapter 2.2.1. --- Cell Lines --- p.24 / Chapter 2.2.2. --- Xenografts --- p.27 / Chapter 2.3. --- DNA Sequence Analysis --- p.27 / Chapter 2.3.1. --- Genomic DNA Extraction --- p.27 / Chapter 2.3.2. --- Polymerase Chain Reaction (PCR) --- p.28 / Chapter 2.3.3. --- DNA Sequencing --- p.32 / Chapter 2.4. --- RNA Expression Analysis --- p.32 / Chapter 2.4.1. --- Total RNA Extraction and Reverse Transcription --- p.33 / Chapter 2.4.2. --- Quantitative Real-time Polymerase Chain Reaction (QRT-PCR) --- p.35 / Chapter 2.5. --- Protein Expression Analysis --- p.35 / Chapter 2.5.1. --- Total Protein Extraction --- p.35 / Chapter 2.5.2. --- Nuclear and Cytoplasmic Protein Isolation --- p.36 / Chapter 2.5.3. --- Western Blotting --- p.39 / Chapter 2.6. --- Immunohistochemical Staining --- p.41 / Chapter 2.7. --- Statistical Analysis --- p.41 / Chapter 2.8. --- Immunoprecipitation --- p.43 / Chapter 2.9. --- Electrophoretic Mobility Shift Assay (EMSA) and Supershift Assay --- p.44 / Chapter 2.10. --- Enzyme-Linked Immunosorbent Assay (ELISA) --- p.45 / Chapter 2.11. --- Plasmid Preparation --- p.45 / Chapter 2.11.1. --- Plasmids --- p.45 / Chapter 2.11.2. --- Bacterial Transformation and Plasmid DNA Extraction --- p.46 / Chapter 2.12. --- Transfections --- p.46 / Chapter 2.12.1. --- Transient Transfection --- p.46 / Chapter 2.12.2. --- Stable Transfection --- p.47 / Chapter 2.13. --- Immunofluorescence --- p.47 / Chapter 2.14. --- Cell Proliferation and Viability Analysis --- p.47 / Chapter 2.15. --- Small Interfering RNA (siRNA) Knockdown --- p.49 / Chapter 2.16. --- Expression Microarray --- p.49 / Chapter 2.16.1. --- Agilent Oligonucleotide Microarray --- p.50 / Chapter 2.16.2. --- Data Analysis --- p.51 / Chapter Chapter 3 --- Activation of NF-kB Signals in NPC --- p.51 / Chapter 3.1. --- Introduction --- p.52 / Chapter 3.2. --- Results --- p.52 / Chapter 3.2.1. --- Expression Pattern of NF-kB Subunits in NPC Tumour Lines --- p.55 / Chapter 3.2.2. --- Distinct NF-kB Complexes in NPC Tumour Lines --- p.60 / Chapter 3.2.3. --- Expression of NF-kB Subunits in NPC Primary Tumours --- p.67 / Chapter 3.3. --- Discussion / Chapter Chapter 4 --- Alterations of NF-kB Components in NPC --- p.71 / Chapter 4.1. --- Introduction --- p.72 / Chapter 4.2. --- Results --- p.72 / Chapter 4.2.1. --- Homozygous Deletion of IicBa and TRAF3 in NPC Tumour Lines --- p.76 / Chapter 4.2.2. --- Mutation of TRAF2 and A20 in NPC Tumour Lines / Chapter 4.2.3. --- Aberrant Expression of Multiple NF-kB Signalling Components in NPC Tumour Lines --- p.80 / Chapter 4.2.4. --- Expression of NF-kB Signalling Components in NPC --- p.85 / Primary Tumour --- p.92 / Chapter 4.3. --- Discussion --- p.99 / Chapter Chapter 5 --- Identification of Downstream Targets for NPC-associated NF-kB Signalling --- p.99 / Chapter 0.1. --- Introduction --- p.99 / Chapter 0.2. --- Results --- p.100 / Chapter 0.2.1. --- Target Genes Modulated by p50 --- p.100 / Chapter 0.2.2. --- Functional Annotation of p50 Target Genes --- p.105 / Chapter 0.2.3. --- Target Genes Modulated by RelB --- p.105 / Chapter 0.2.4. --- Functional Annotation of RelB Target Genes --- p.105 / Chapter 0.2.5. --- Functional Annotation of Genes Modulated by both p50 and RelB --- p.111 / Chapter 0.3. --- Discussion --- p.118 / Chapter Chapter 6 --- Functional Role of TRAF3 Inactivation in NPC --- p.118 / Chapter 0.1. --- Introduction --- p.118 / Chapter 0.2. --- Results --- p.118 / Chapter 0.2.1. --- Effect of TRAF3 Restoration on NF-kB Activity --- p.119 / Chapter 0.2.2. --- Effect of TRAF3 Expression on Cell Proliferation --- p.123 / Chapter 0.2.3. --- TRAF3 Expression Modulates Interferon Transcription in NPC Cells --- p.128 / Chapter 0.3. --- Discussion / Chapter Chapter 7 --- General Discussion --- p.132 / Chapter Chapter 8 --- Conclusion / Chapter Chapter 9 --- References / Appendix --- p.136

Tong Hung Man Joanna. / "June 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 137-149). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Based on matching analysis between different EBV strains, we found two nucleotide variations in miR-BART21 and four nucleotide changes in miR-BART22. Interestingly, two nucleotide variations upstream of mature miR-BART22 likely favor its biogenesis by Drosha/DGCR8 processing and we experimentally confirmed this augmentation by in-vitro Drosha digestion, and thus may underline the high and consistent expression of miR-BART22 in NPC tumors. / Infection with the Epstein-Barr virus (EBV) is a strong predisposing factor in the development of nasopharyngeal carcinoma (NPC). Many viral gene products including EBNA1, LMP1 and LMP2 have been implicated in NPC tumorigenesis, although the de novo control of these viral oncoproteins remain largely unclear. / MicroRNAs (miRNAs) are a class of small, non-coding RNAs with a size around 18--24 nucleotides with significant roles in regulating gene expression by either transcriptional silencing or translational suppression. As gene regulators, recent miRNA studies have emphasized the contribution of aberrant miRNA expression in cancer development. The recent discovery of EBV encoded viral miRNAs (ebv-miRNAs) in lymphoid malignancies has prompted us to examine the NPC-associated EBV miRNAs. In this study, we have systematically examined the NPC associated EBV genome for viral-encoded miRNA expression. By constructing small cDNA libraries from a native EBV positive NPC cell line (C666-1) and a xenograft (X2117), we screened about 3000 clones and detected several small EBV fragments, within which two novel ebv-miRNAs in the BARTs region were identified. These two newly identified miRNAs, now named miR-BART21 and miR-BART22, were proven to be abundantly expressed in most NPC samples by both Northern blot and QRT-PCR analysis. / Taken together, this thesis shows that two newly identified EBV-encoded miRNAs are highly expressed in latent EBV infection in NPC. Frequent expression of miR-BART22 can be explained partially by a specific EBV strain that is associated with NPC in our locality. Our findings emphasize the role of miR-BART22 in modulating LMP-2A expression. Because LMP-2A is a potent immunogenic viral antigen that is recognized by the cytotoxic T cells (CTLs), down-modulation of LMP-2A expression by mir-BART22 may permit escape of EBV-infected cells from host immune surveillance. / We attempted to predict the potential viral and cellular targets of miR-BART21 and miR-BART22 by public available computer programs, miRanda and RNAhybrid. A number of potential cellular mRNA targets were suggested, although many failed to be validated by luciferase reporter assay. However, we found a putative miR-BART22 binding site in the LMP2A-3'UTR. Although the LMP-2A transcript is consistently detected in NPC, only 6 out of 26 (23%) primary NPC tumors show weak LMP-2A expression by immunohistochemistry (IHC). The expression levels of miR-BART22 and LMP-2A mRNA have also been determined in eleven of these tumors. Interestingly, the LMP-2A mRNA expression level did not directly correlate with protein expression, and relatively low expression levels of miR-BART22 miRNA were observed in all 3 LMP-2A positive-primary tumors. The suppressive effect of miR-BART22 on LMP-2A was also experimentally validated by a series of dual luciferase reporter assays using reporter constructs containing the putative or mutated recognition site at the LMP-2A 3'UTR. By co-transfection of different amounts of miR-BART22 with the LMP-2A-3'UTR expression vector in reporter assay, we confirmed that miR-BART22 suppressed the LMP-2A protein level in a dose-dependent manner. Furthermore, transfection of miR-BART22 into HEK293 cells that had been stably transfected with pcDNA3.1-LMP-2A, which contains a complete LMP-2A ORF and 3'UTR, readily suppressed levels of the LMP-2A protein. / Lung, Wai Ming Raymond. / Adviser: To Ka Fai. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 197-226). / 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 Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.