published_or_final_version / Clinical Oncology / Doctoral / Doctor of Philosophy

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Surgery / Master / Master of Philosophy

Background: ICG-001, an antagonist of CBP (CREB-binding protein), has been demonstrated to exert anti-tumor activity via the modulation of the Wnt signalling pathway. It has previously been demonstrated that miRNAs play an important role in ICG-001-mediated tumor suppression. In the present study, the role of miRNA-134 and 1-integrin in ICG-001-mediated anti-tumor activity in nasopharyngeal carcinoma (NPC) was examined. Methods: NPC cell lines including C666-1, HONE-1 and HK-1 were used in this study. RT-PCR and Western blot were used to study the expression of miRNA-134 and the protein expression of the target proteins, respectively. Confocal microscopy was used to analyse the subcellular localization of 1-integrin. In the functional studies, in vitro endothelial adhesion assay and in vivo nude mice model were used to evaluate the adhesion and migration of ICG-001-treated NPC cells in animals, respectively. Results: ICG-001 was found to up-regulate the expression of miRNA-134 and down-regulate 1-integrin in NPC cells. The effect was accompanied with the inhibition of the adhesion of NPC cells to lung endothelial cells. In addition, over-expression of miRNA-134 would down-regulate the expression of 1-integrin. Results from 1-integrin 3'UTR Renilla luciferase reporter assay confirmed that 1-integrin is a target of miRNA-134 in NPC cells. In the animal study, the ability of ICG-001-pretreated NPC cells or stable miRNA-134 expressing NPC cells to migrate to the mouse lung was greatly reduced. Conclusion: The CBP antagonist ICG-001 may further be developed as an anti-tumor agent for the treatment of nasopharyngeal carcinoma

published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Biological Sciences / Master / Master of Philosophy

published_or_final_version / Chinese Medicine / Master / Master of Philosophy

published_or_final_version / Diagnostic Radiology / Master / Master of Philosophy

published_or_final_version / Clinical Oncology / Master / Master of Philosophy

Nasopharyngeal carcinoma (NPC) is squamous cell carcinoma derived from the epithelial layer of nasopharynx. The incidence is high in Southern China and South-east Asia. In Hong Kong, the prevalent of NPC subtype is undifferentiated NPC and is in close association with Epstein-Barr virus (EBV). MicroRNAs (miRNAs) are small non-coding RNAs. They play vital roles in regulating gene expression at post-transcriptional level. EBV also expresses viral miRNAs but the function remains unclear. In NPC diagnosis and monitoring, circulating EBV DNA level has been commonly used. However, in some cases, EBV DNA is below the detection threshold in the plasma of NPC patients making it impossible to be used in continuous monitoring of the patients. This study aimed to evaluate whether miRNAs (both NPC-derived and EBV-derived miRNAs) could be used as candidate circulating markers for disease monitoring. Candidate gene approach was used to select suitable circulating miRNA markers for NPC patients. Four candidate miRNAs including miR-21, miR-1301, miRBART7 and miR-BART22 were examined. The expression levels were first validated in paired NPC tissues and normal counterparts. Furthermore, circulating miRNA levels were evaluated in the plasma of NPC and normal individuals. To examine the changes of miRNA in response to radiotherapy, changes of circulating miRNA were monitored in 13 NPC patients before and after radiotherapy. In addition, functional assay in cell proliferation was performed to validate the potential role of the candidate miRNA in the pathogenesis of undifferentiated NPC. Of the 4 candidate miRNAs, miR-BART7 was consistently over-expressed in both tumor tissues and plasma samples of NPC. In addition, circulating miRBART7 was also detected in NPC patients in case of the plasma EBV DNA levels below the detection threshold. In response to radiotherapy, 10 of 13 (76.92%) patients had decreasing circulating miR-BART7 in the plasma samples collected at 3 month after radiotherapy. Furthermore, introducing miR-BART7 mimics into the undifferentiated NPC cell line HONE1 and normal nasopharyngeal-derived epithelial cell cultures NP69 and NP460 resulted in significant increases in cell proliferation rates of all the 3 cell lines. To summarize, miR-BART7 expression was significantly higher in NPC patients as a potential oncogenic miRNA. Evaluating the miR-BART7 levels is a possible screening approach in NPC diagnosis and post-treatment monitoring. The oncogenic role of miR-BART7 in the development of undifferentiated NPC deserves further investigation. / published_or_final_version / Surgery / Master / Master of Philosophy