published_or_final_version / abstract / Medicine / Master / Doctor of Medicine

published_or_final_version / abstract / Medicine / Master / Doctor of Medicine

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

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

Nasopharyngeal carcinoma (NPC), endemic in southern China and Southeast Asia, was ranked 7th as the most common new malignancy in Hong Kong. Metastatic and recurrent NPC have a poor prognosis despite recent advancement in medicine. Inactivation of tumor suppressor genes (TSGs) through the loss of chromosomal regions is frequently reported in NPC. With the recent discovery of cancer stem cells (CSCs), which are refractory to current therapies, a new paradigm shift in the perspective of cancer therapy development has emerged. For the first time, this study aims to unravel the complexity of NPC tumorigenicity for identifying more effective targets by studying the possible interplay between CSCs and TSGs. NPC cell lines had different expression profiles of CSC markers, confirming not all CSC markers are applicable to every tumor type. Although CD24/CD44 were expressed in NPC, however CD24+CD44+ NPC cells did not initiate tumor formation. By utilizing a cancer hybrid cell model with a transferred single copy of chromosome 3, physiological β-catenin up-regulated core stem cell markers through the activation of Wnt signaling pathway in NPC. Moreover, the down-regulation of β-catenin suppressed chemoresistance and inhibited cell proliferation, colony formation, angiogenesis, the epithelial-mesenchymal transition (EMT) process, and the tumor microenvironment factors. Amongst the tumor microenvironment factors, chemokine Rantes and matrix metalloproteinase were down-regulated when β-catenin was knocked down. Therefore, activation of Wnt signaling provide an alternative platform for identifying putative CSCs in NPC, leading to the identification of several prospective CSC markers in NPC. Down-regulation of IKBB, a NF-KB inhibitor, in the majority of NPC patients indicated that IKBB plays a prominent role as a TSG in NPC. In this study, IKBB was found to exert its tumor suppressive functions by abrogating tumor formation, cell migration, invasion and angiogenesis. Angiogenic factors, including Rantes, Upar, IL6 and IL8, were significantly down-regulated by IKBB. In addition, IKBB also suppressed the binding activity of NF-KB. The involvement of Akt/Gsk-3β pathways was also observed. Taken together, IKBB regulated NPC tumorigenesis through NF-KB/Akt/Gsk-3β and interaction with tumor microenvironment. Collectively, this study demonstrated that the progression of NPC is not simply initiated by a single signaling pathway, but a dynamic and complex interplay between multiple signaling networks and the tumor microenvironment. NPC tumorigenesis is hypothesized to be driven by orchestrated interaction between CSCs and TSGs through crosstalk with the tumor microenvironment. Amongst the major players in the tumor microenvironment, Rantes/CCL5, IL6, and the matrix metalloproteinase are envisaged to induce angiogenesis, EMT, and metastasis in NPC. This dynamic intercommunication between CSCs and tumor suppressor IKBB signaling networks may shed better insights on modulation of the major hallmarks of cancer in orchestrating NPC development. The modulation of the major hallmarks of cancer by CSCs and IKBB, a TSG, involves promotion of aberrant proliferation, enhancement of invasion and metastasis, induction of angiogenesis, circumvention of tumor suppressors, and prevention of cell death. Taken together, selective and synergistic co-targeting these signaling networks and the tumor microenvironment will provide a more effective new modality of treatments for NPC. / published_or_final_version / Clinical Oncology / Doctoral / Doctor of Philosophy

Hong Kong, situated in the Southern part of China, is an endemic area where the incidence of nasopharyngeal carcinoma (NPC) is among the highest in the world. The cancer, which is located at the deepest part of the human skull, represents one of the most difficult tumours to treat in the head and neck region. The management of tumour recurrence after radiotherapy is even more challenging. Epstein-Barr virus (EBV) is a human herpes virus and it is the first virus that is discovered to be associated with human malignancy. Over the past few decades, the role of EBV serology in the management of NPC has been extensively investigated. More recently, a series of EBV encoded microRNAs, which are short, non-coding RNAs, are found to be commonly expressed in NPC. In our studies, we have investigated the role of EBV DNA and EBV miRNA BART7 in the management of recurrent NPC. Plasma EBV DNA is accepted as a tumour marker for NPC. We found that in patients with recurrent NPC, the pre-operative level of plasma EBV DNA reflects the tumour load and correlates with the T-stage of the tumour. It also predicts the chance of resection margins that are histologically positive for malignancy. When measured serially after surgery, it is useful to detect tumour recurrence. However, we found that up to 15.5% of our patients, who had tumour recurrence in the nasopharynx, were seronegative for EBV DNA. In such circumstances, plasma EBV miRNA BART7, which is expressed independently of EBV DNA, may be used for such purpose. Moreover, using the in-vitro model, we demonstrated that the expression of EBV miRNA BART7 in the HONE1 cell line increases the rate of proliferation, migration and invasion of tumour cells. By using the same in-vitro model, we found that the EBV miRNA BART7 increases the sensitivity of the HONE1 cells to ionizing radiation in a dose-dependent manner. This is confirmed with the in-vivo experiments using the zebra fish model. In our previous study on the multivariate analysis of prognostic factors in salvage nasopharyngectomy for recurrent NPC, we found that the resection margin status is one of the most important independent factors influencing the local tumour control and overall survival. In order to improve the chance of obtaining clear margins after surgery, we have to depend on the intra-operative frozen section analysis and the post-operative histological examination of the resection margin specimen. In our current study, we showed that contrast MRI is accurate in assessing the local extent of recurrent nasopharyngeal carcinoma. During nasopharyngectomy, a radial resection margin of 15mm should be taken with the underlying medial pterygoid muscle. For tumours with parapharyngeal extension, the pharyngobasilar fascia should be resected enbloc with the specimen. The chance of local recurrence after salvage nasopharyngectomy in patients with histologically uninvolved margins was 20.0%. Tissue EBV miRNA BART7 is useful to identify a subgroup of patients with histologically close margins who are at increased risk of subsequent local tumour recurrence. Post-operative adjuvant treatment is warranted for these patients. / published_or_final_version / Surgery / Doctoral / Doctor of Philosophy

published_or_final_version / Community Medicine / Master / Master of Public Health

published_or_final_version / Medicine / Master / Doctor of Medicine

Ma, Buig Yue Brigette. / Thesis M.D. Chinese University of Hong Kong 2014. / Includes bibliographical references (leaves 232-270). / Title from PDF title page (viewed on 18, November, 2016).

Nasopharyngeal carcinoma (NPC) is a common cancer in Southeast Asia. While external radiotherapy is the mainstay of treatment, adjuvant chemotherapy is required in advanced disease. Current chemotherapy heavily relies on cisplatin and docetaxel. The disease relapse rate is relatively high with poor survival chance for recurrent or metastatic disease. Development of novel therapeutic strategies against the disease is clearly needed. Bortezomib and suberoylanilide hydroxamic acid are respectively classified as proteasome inhibitor and histone deacetylase inhibitor. Bortezomib and SAHA induce apoptosis in various cancers including renal cell carcinoma, hepatoma and mantle cell lymphoma. However, the effect of bortezomib and SAHA on NPC cells was not mentioned. We sought to study the molecular and cellular effects of the bortezomib and SAHA on NPC cells hoping to look for drug alternatives in NPC treatment. Since SAHA reactivates EBV in NPC cells, the combined effect of bortezomib and SAHA on EBV lytic cycle was also evaluated. NPC proliferation was assessed by MTT assay. 5 EBV-positive NPC cell lines authenticated by Short Tandem Repeats (STR) profiling were used as most NPC in Chinese contains EBV. Isobologram and combination index analysis confirmed that the anti-proliferative effect on NPC mediated by the drug combination was synergistic. 30 nM bortezomib and 5μM SAHA were chosen for further studies on apoptosis because the synergism of the drugs was maximal at these concentrations. NA and C666-1 were chosen for further studies because C666-1 was the only NPC cell line that consistently harboured native NPC and the combination index was lowest in NA among the rest of the NPC cell lines. Bortezomib led to apoptosis in NPC cells. The effect was more pronounced after the addition of SAHA as evidenced by greater TUNEL positive population and earlier cleavage of poly ADP ribose polymerase (PARP). In previous cancer studies, ROS induction was commonly suggested pathways of bortezomib and SAHA’s antiproliferative effects. Staining with dichlorofluorescein diacetate (DCFH-DA) revealed enhanced reactive oxygen species (ROS) level in cells treated with both drugs. At the same time, addition of N-acetyl cysteine, a ROS scavenger, markedly reduced their effect on cytotoxicity. SAHA is known for its effect on EBV lytic cycle induction. Yet, the addition of bortezomib diminished SAHA-induced viral load, lytic protein expression and EBV infectivity. The expression of Latent Membrane Protein 1 (LMP1) was much lower in NPC treated with both drugs than in NPC treated with SAHA alone, which would reduce NF-κB activation. This, together with reduced EBNA1 expression upon treatment with both drugs, would theoretically reduce oncogenic activity. In conclusion, bortezomib and SAHA induced ROS-driven apoptosis of NPC in a synergistic manner and bortezomib inhibited SAHA-induced EBV lytic cycle. It suggests that bortezomib and SAHA are potential drug candidates for the treatment of nasopharyngeal carcinoma. / published_or_final_version / Paediatrics and Adolescent Medicine / Master / Master of Research in Medicine