published_or_final_version / Clinical Oncology / Doctoral / Doctor of Philosophy

published_or_final_version / Surgery / Master / Master of Philosophy

published_or_final_version / Pathology / 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

Breast cancer comprises of 22.9% of all cancers worldwide in females. In the year 2008, it has caused 458,503 deaths worldwide. De-regulation of transcription factors has been shown to play an important role in the progression of breast cancers. Snail and TWIST genes have been found to promote epithelial-mesenchymal transition (EMT). It has been suggested that the level of expression of each of these genes correlates with poor prognosis in different types of solid tumors. For breast cancer, the up-regulation of Snail was associated with recurrence and higher tumor grade, while the up-regulation and up-regulation of TWIST was associated with shorter survival and metastatic development. However, in recent studies conflicting results have been observed. Our collaborator had analyzed mRNA expression data obtained from the Gene Expression Omnibus (GEO) database together with patient survival data from the breast cancer cohort datasets, and found that expression of Snail when stratified against TWIST expression levels or vice versa, gave more significant association with survival than when expression levels of Snail or TWIST was considered on their own. To investigate whether these findings could be demonstrated at a protein level, we performed imrnuno-histochemisty analysis on breast cancer samples in tissue microarray blocks. Nuclear and cytoplasmic scores of TWIST were successfully assessed separately in 114 invasive breast cancer patients. The Snail scores were obtained from previous studies. As Snail and TWIST are both transcription factors, nuclear expression of each was examined for correlation of Snail and TWIST with pathological features and patient survival. Our results showed that nuclear Snail expression did not correlate with survival (p=0.498) but when stratified with nuclear TWIST, high levels of nuclear Snail expression associated with poorer survival in patients with low nuclear TWIST expression (p=O.2l2), though not statistically significant which agreed with the mRNA results of our collaborator. For nuclear TWIST expression, association with survival was in reverse from that of the mRNA findings. Low expression levels of TWIST mRNA was associated with shorter survival, however immuno-histochemistry showed that high levels of nuclear TWIST expression marginally correlated with poorer survival (p=O.079). Low levels of cytoplasmic TWIST expression on the other hand, correlated with poorer survival in patients (p=O.024), and when stratified against high nuclear Snail, expression was associated with shorter survival (p=O.022), which is in keeping with mRNA findings. The results show that Snail and TWIST expression gave more prognostic value when considered together than when considered individually, which suggests that Snail and TWIST might be functionally similar in the promoting of EMT mediated breast. It also highlights the importance of nuclear and cytoplasmic localization by immuno-histochemistry in evaluating results and in assessing its role in promoting breast cancer progression. In conclusion Snail and TWIST should be considered together for prognostication of breast cancer as they may complement each other in predicting the progression of the disease. / published_or_final_version / Pathology / Master / Master of Medical Sciences

Breast cancer is the leading malignancy among Asian women, which often have a young disease onset pattern. Germline mutation in high-penetrance breast cancer susceptibility genes are known to play an important role in early disease onset, but only 5-10% cases are associated with mutations in BRCA1 or BRCA2 gene. By contrast, common variants might also have deleterious effect in breast cancer development. A BRCA2 coding SNP rs1799944 (N991D) was found to have no association with breast cancer risk among Hong Kong Chinese population, but significantly confers a better disease-free survival in the breast cancer patients. In this study, the relevance of this association was further verified by using an enlarged sample pool of Hong Kong Chinese breast cancer patients. A total of 483 Hong Kong Chinese breast cancer subjects were unselectively recruited between 1976 and 2011. SNP N991D genotype of patients was determined by Taqman allelic discrimination genotyping assay. Pearson’s Chi-Square and logistic regression were used to assess the association between the SNP genotypes and breast cancer disease characteristics. Kaplan-Meier survival and multivariate Cox proportional hazards regression analyses were used to examine the relationship between the SNP genotypes and overall survival as well as disease-specific survival of the patients. Of the 449 breast cancer patients successfully genotyped, 16.9% had heterozygous AG genotype and 0.4% had rare homozygotes GG genotype. The variant allele G had a MAF of 8.91% among Hong Kong Chinese breast cancer patients. Patients harboring the SNP N991D variant allele G had longer disease-free survival period compared to the non-carriers (HR = 0.28; 95% CI: 0.09 – 0.92; p=0.036), which was confounded by patients’ local and/or distant metastasis status at diagnosis stage (HR=3.00; 95% CI: 1.57 – 5.74; p=0.001). Although N991D carriers also had a better overall survival pattern than the non-carriers, the difference between them was not statistically significant. Moreover, the association of SNP N991D variant allele G carriers with a lower disease recurrence rate (OR= 0.27; 95% CI: 0.82 - 0.90; p=0.023) was owing to the association of the variant with fewer distant metastases (OR = 0.11; 95% CI: 0.02 – 0.83; p=0.010) but not the local relapse status (OR= 0.38; 95% CI: 0.85 – 1.67; p=0.182) of the clinical outcome when comparing to the non-carriers. In conclusion, the missense BRCA2 N991D SNP has indicated an association with better clinical outcome as well as disease-free survival in Hong Kong Chinese breast cancers. / published_or_final_version / Pathology / Master / Master of Medical Sciences

Nasopharyngeal carcinoma (NPC) is different from other head and neck squamous cell carcinomas and is closely related with Epstein-Barr virus infection. It is endemic in southern China and Southeast Asia, affecting between 20 and 30 per 100,000 populations. According to the World Health Organization (WHO) histological classification, there are three subtypes of NPC: WHO type 1 NPC is keratinizing squamous cell carcinoma; type 2 NPC is differentiated non-keratinizing carcinoma; type 3 NPC is undifferentiated non-keratinizing carcinoma. In southern China including Hong Kong, type 3 NPC (undifferentiated NPC) is dominant and constitutes over 90% of the total NPC. MicroRNA-138 (miR-138) is a small non-coding RNA which has been reported to be highly expressed in undifferentiated NPC. We hereby evaluated whether the miR-138 level could be used to differentiate NPC patients from the normal individuals and examine the potential oncogenic role in undifferentiated NPC cell line. To validate the hypothesis that miR-138 was an oncogenic microRNA, which is overexpressed in undifferentiated NPC patients, we first examined its expression level in nasopharyngeal tissues and peripheral blood. In our cohort, cancer tissues samples were collected from 42 primary NPC and 29 recurrent NPC patients. To evaluate the expression level in the cancer tissues, the miR-138 level was quantified by real-time quantitative polymerase chain reaction. For primary NPC, the expression level was compared with 29 normal nasopharyngeal epithelia. For recurrent NPC, the microRNA level was compared with the paired normal mucosa counterparts obtained from the same patients. In addition, plasma samples were also collected from 22 primary NPC, 21 recurrent NPC and 17 normal individuals. Our data suggested that there was no difference in the miR-138 expression level in primary NPC tissue and normal nasopharyngeal tissue from control. There was no difference in the circulating miR-138 levels in the primary NPC, recurrent NPC and normal control groups. The circulating miR-138 could not be used to differentiate NPC patients from the normal individuals. Further functional analysis on the undifferentiated NPC cell line HONE1 suggested that miR-138 overexpression could enhance NPC cell proliferation, migration and invasion in comparison with the mock control. With the use of high-throughput gene expression arrays, we observed that multiple cancer-related pathways were affected in miR-138 overexpressed NPC cells. Staining with Acridine orange (AO) and phosphorylated H2AX (γH2AX) showed that miR-138 overexpression is associated with an enhanced response to radiation. Our results are concordant with other similar studies suggested that miR-138 is an oncogenic microRNA which play an important part in the undifferentiated NPC tumorigenesis. Further studies, based on larger sample size, are warranted to explore the clinical use of this small RNA in diagnosis, prognosis and management of undifferentiated NPC. / published_or_final_version / Surgery / Master / Master of Philosophy

Hepatocellular carcinoma (HCC) is the most common tumors worldwide. In contrast to other cancers, the prognosis of HCC is extremely poor, with less that 5% of 5-year survival rate worldwide. From our previous studies, we isolated Chromodomain Helicases/ATPase DNA binding protein1-Like (CHD1L) gene from chromosome 1q21, and characterized it as a specific oncogene in HCC. By using 2D-PAGE and MALDI-TOF mass spectrometry approach, Translationally Controlled Tumor Protein (TCTP) was identified as a CHD1L target, which was preferentially expressed in CHD1L-transfected cells. TCTP is a highly conserved protein and expressed in almost all mammalian tissues. It has been reported that TCTP interacts with microtubules in a cell-cycle-dependent manner, and functions as a prosurvival factor and inhibiting apoptosis. To better understand the molecular mechanisms of HCC progression, the effect of TCTP overexpression in HCC and the mechanism by which TCTP regulated cell-cycle progression were elucidated in this study. CHD1L is a unique oncogene belongs to SNF2-like subfamily. Mechanistic studies found that CHD1L protein directly binds to the promoter region (nt -733 to -1,027) of TCTP and activated TCTP transcription. Investigation of clinical HCC specimens found that overexpression of TCTP was not only significantly associated with the advanced tumor stage (P = 0.037) and overall survival time of HCC patients (P = 0.034), but also an independent marker associated with poor prognostic outcomes. Functional studies demonstrated that TCTP has tumorigenic abilities and overexpression of TCTP contributed to the mitotic defects of tumor cells. Further mechanistic studies demonstrated that TCTP promoted the ubiquitin-proteasome degradation of Cdc25c during mitotic progression, which caused the failure in the dephosphorylation of Cdk1 on Tyr 15 and decreased Cdk1 activity. The consequence of chromosome missegregation and mitotic catastrophe results in aneuploidy, which is frequently observed in cancer. In addition, the correlation between TCTP overexpression and metastatic potential of HCC was elucidated by examined the expression levels of TCTP using a tissue microarray (TMA) containing 60 pairs of primary HCCs and their matched metastases. Further studies demonstrated that overexpression of TCTP shows high incidence of extrahepatic metastasis and positive correlation was found between TCTP and MMP-2 or MMP-9 (Spearmen correlation coefficient=0.466, and 0.352, respectively, P<0.001 for both). In vitro functional studies showed that TCTP protein associated with promoter regions of MMP-2 and MMP-9 and activates their transcriptions. Molecular analyses revealed that TCTP served as a JunD coactivator and formed complexes with JunD and bind with consensus AP-1 sites on MMP-2 and MMP-9 promoters to enhance their expression in HCC cells. More importantly, high co-expression of TCTP and MMP-2 or MMP-9 was significantly associated with poor disease-free survival (log rank= 8.146, and 11.677 respectively, P =0.017 and 0.003 respectively). In summary, two novel molecular mechanisms (CDH1L/TCTP/Cdc25C/Cdk1) and (TCTP/JunD/MMP-2, MMP-9) were revealed during HCC progression and metastasis. Also, the prognostic value of TCTP and MMP-2 or MMP-9 coexpression for HCC was highlight in this study. / published_or_final_version / Clinical Oncology / Doctoral / Doctor of Philosophy

Background: Esophageal squamous cell carcinoma (ESCC) has been increasing in incidence, but knowledge of the genetic basis of this disease remains limited. In general, esophageal carcinoma can be divided into two main types: Esophageal Squamous Cell Carcinoma (ESCC) and Esophageal Adenocarcinoma (EAC). The pathogenesis of esophageal carcinoma still remains unclear, although some risk factors like chronic irritation, or chronic inflammation which may be caused by diseases such as gastroesophageal reflux disease (GERD) or unhealthy lifestyles like smoking have been proved to be related to the carcinogenic process. Diagnosis and treatment for this kind of cancer have continue to develop and evolve, but the 5-year overall survival rate is still relatively low. Therefore, it is clinically important to identify any potential genetic changes which may help us to discover some useful biomarker targets for the further development of more direct and harmless targeted therapy for our esophageal cancer patients. Objectives: In this study, I aimed to identify some potential oncogenic microRNA (miRNA) and to study their clinical meaning in ESCC patients. Methods: Microarray was applied to identify differentially expressed miRNAs in ESCC tumour tissue, compared with corresponding adjacent non-tumour esophageal tissue. One candidate oncogenic miRNA, miR-665, was investigated in the present study. After testing the expression level of miR-665 in ESCC cell lines and patients’ samples with RT-PCR, miR-665 stably expressing cells was established using two ESCC cell lines (KYSE30 and KYSE510). Functional characterization was then conducted using in vitro and in vivo assays to examine the effect of miR-665 towards the development of ESCC. Bioinformatic software such as Target Scan was used to generate a list of predicted target genes that may be modulated by miR-665. Results: The high expression of miR-665 has been confirmed in ESCC tissues and cell lines, showing the potential carcinogenic function of miR-665. Ectopic expression of miR-665 also demonstrates its ability to enhance tumour growth and invasion in vitro and in vivo. Bioinformatic analysis of miR-665 predicted targets showed putative binding sites for miR-665 within the 3’UTR region of NLK. Conclusions: This study has identified a novel miRNA and a related gene which might play an important role in the pathogenesis of ESCC, affecting the cancer process and tumour growth. This may help to find potential new biomarker for the future improvement and development of new treatment of ESCC patients. / published_or_final_version / Clinical Oncology / Master / Master of Philosophy