運用miRNA微陣列手段，我們篩選到一批在結直腸腫瘤內高表達和低表達的miRNA。其中miR-133a是在腫瘤中最顯著降低的miRNA之一， 但其在腫瘤的發生發展過程中的作用尚未可知，因此我們選擇miR-133a最為研究目標，論證其的生物學功能，分子機理，及其在結直腸癌中的靶分子。 / 我們首先在較大規模樣本中驗證miR-133a的低表達。定量PCR結果顯示，對比正常的癌旁組織，miR-133a在94例結直腸癌組織中顯著低表達（p < 0.001）。我們進一步分析miR-133a在9種常用的腫瘤細胞系內的表達情況。對比正常的直腸組織，miR-133a在9種常用的結直腸細胞系內的表達均明顯下降。在腫瘤發生發展過程中，癌細胞趨向於降低具有抑癌功能的基因的表達。因此我們推測miR-133a是一個潛在的腫瘤抑制miRNA。 / 為了論證我們的假設，我們首先選取miR-133a低表達的結直腸癌細胞系HCT116和LoVo最為研究模型，將miR-133a在這兩種細胞系內過表達。升高的miR-133a可以抑制腫瘤細胞生長（p < 0.01和p < 0.05），抑制腫瘤克隆集落形成（p < 0.01）。我們進一步發現過表達miR-133a可以抑制裸鼠體內腫瘤的生長（p < 0.05）。細胞週期分析顯示miR-133a抑制細胞生長的能力表現為誘導腫瘤細胞週期阻滯於G0/G1期。細胞週期特異性CDK抑制蛋白p21和p27對於細胞週期調節十分關鍵。基於此項觀察，我們進一步分析了p21和p27的表達。Western-blot實驗證實過表達miR-133a可以促進HCT116和LoVo細胞內p21和p27的蛋白上調。但miR-133a在p53突變型的HT29過表達後並沒有引起p21的變化。通過對比p53野生型和突變性細胞系，我們發現p53對於miR-133a誘導p21是十分關鍵的。為了證明miR-133a可以引起p53的活性，我們通過啟動子螢光報告實驗證實，miR-133a不僅可以促進p53結合DNA 的能力，而且可以引起p21啟動子的活性。其次，我們發現在p53野生型細胞株HCT116中，轉染si-p53可以拮抗miR-133a誘導p21。我們通過蛋白降解實驗發現，miR-133a可以延長p53蛋白的半衰期。 / 基於以上實驗事實，我們推測miR-133a誘導p21是通過穩定p53蛋白來實現的。通過數個miRNA靶基因預測軟體，我們判斷RFFL可能是miR-133a發揮效力的直接靶基因。RFFL是E3連接酶，負責非磷酸化p53和磷酸化p53的降解。在RFFL的3側非翻譯區有一個進化保守的miR-133a識別序列。我們克隆此段序列到螢光素酶基因的3側非翻譯區，並進行雙螢光素酶報告基因檢測。測試發現miR-133a可以直接結合到RFFL的此段序列上，並抑制前段基因的翻譯。體外實驗證實，過表達miR-133a可以減少HCT116和HT29細胞內的RFFL蛋白，但並不影響其mRNA。過表達RFFL可以降低p53的表達，反之降低RFFL的蛋白表達，可以提高p53和p21蛋白。上述實驗均有助於證實miR-133a是通過抑制RFFL來提高p21的表達，進而抑制細胞週期。 / 我們也發現miR-133a具有增敏抗癌藥物的效力。單獨轉染miR-133a並不能顯著引發細胞凋亡，而聯合使用miR-133a及抗癌藥物doxorubicin，或者Oxaliplatin都可以顯著增強細胞的早期凋亡。 / 基於上述實驗結果，我們證實miR-133a是一個抑制腫瘤生長的miRNA，其機制可能是通過抑制RFFL蛋白的表達，並啟動p53/p21信號通路引起的。我們的實驗說明miR-133a可以對抗腫瘤藥物起到增敏的作用。 / We found that miR-133a was significantly down-regulated in colorectal cancer (CRC) tissues using miRNA array. However, the role of miR-133a in CRC is largely unknown. We sought to clarify its biologic function, molecular basis, and target gene in CRC. The down-regulation of miR-133a was verified in 94 primary CRC tumours compared with the matched adjacent normal tissues (p < 0.001) and in 9 human colon cancer cell lines. Ectopic expression of miR-133a in colon cancer cell lines (HCT116 and LoVo) significantly suppressed cell growth as evidenced by cell viability assay (p < 0.01 and p < 0.05), and colony formation assay (p < 0.01). Cell cycle analysis revealed that miR-133a caused an increased proportion of cells arrested at G0/G1 phase in HCT116 and LoVo, concomitant with the up-regulation of key G1 phase regulators CDK inhibitors p21 and p27. Promoter-luciferase activity assays indicated that miR-133a markedly increased p53 binding activity and induced p21 transcription. We further revealed that miR-133a decelerated p53 degradation, suggesting that miR-133a was an important positive modulator of the p53/p21 pathway. In silico search showed that the 3’UTR of ring finger and FYVE-like domain containing E3 ubiquitin protein ligase (RFFL), an E3 ubiquitin protein ligase targeting p53 for degradation, contains an evolutionarily conserved miR-133a binding site. Co-transfection with miR-133a repressed RFFL-3’UTR reporter activity for up to 53% (p < 0.01) and remarkably reduced RFFL protein level, indicating that miR-133a directly bound to RFFL mRNA and inhibited RFFL translation. Moreover, miR-133a sensitized colon cancer cells to chemotherapeutic agents (doxorubicin and oxaliplatin) by enhancing apoptosis (p < 0.01) and inhibiting cell proliferation (p < 0.001), adding further weight to the potential significance of miR-133a as a tumour suppressor in inhibiting CRC. In conclusion, miR-133a serves as a functional tumour suppressor in CRC through direct inhibition of the oncogenic RFFL and induction of the p53/p21 pathway. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Dong, Yujuan. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 139-152). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / ABSTRACT --- p.I / ACKNOWLEDGMENTS --- p.VI / LIST OF FIGURES --- p.VII / LIST OF TABLES --- p.IX / ABBREVIATIONS --- p.X / TABLES OF CONTENT --- p.XIII / Chapter CHAPTER ONE --- INTRODUCTION --- p.1 / Chapter 1.1 --- Colorectal cancer --- p.1 / Chapter 1.1.1 --- Epidemiology --- p.1 / Chapter 1.1.2 --- Etiology --- p.4 / Chapter 1.1.3 --- CRC prevention, screening and therapy --- p.7 / Chapter 1.2 --- microRNA (miRNA) --- p.13 / Chapter 1.2.1 --- Biogenesis of miRNA --- p.13 / Chapter 1.2.2 --- Diagnostic value of miRNAs in CRC --- p.16 / Chapter 1.2.3 --- Prognostic value of miRNAs in CRC --- p.25 / Chapter 1.2.4 --- Predictive value of miRNAs for treatment response in CRC --- p.28 / Chapter 1.2.5 --- miRNA-related single-nucleotide polymorphisms and CRC --- p.29 / Chapter 1.2.6 --- miRNAs and their function in CRC genesis --- p.33 / Chapter 1.2.7 --- Future perspective of miRNAs in CRC --- p.41 / Chapter 1.3 --- Hypothesis and objectives --- p.41 / Chapter CHAPER TWO --- METHODOLGY --- p.43 / Chapter 2.1 --- Cell cultures --- p.43 / Chapter 2.2 --- Patients and clinical specimens --- p.43 / Chapter 2.3 --- miRNA extraction from tissue and cell --- p.46 / Chapter 2.4 --- Micro-dissection and RNA extraction from paraffin sections --- p.47 / Chapter 2.5 --- Real-time quantitative PCR for miRNA microarray --- p.48 / Chapter 2.6 --- miRNA expression analysis --- p.48 / Chapter 2.7 --- mRNA expression analysis --- p.49 / Chapter 2.8 --- RNA interference --- p.52 / Chapter 2.9 --- Colony formation assay --- p.52 / Chapter 2.10 --- MTT cell viability assay --- p.53 / Chapter 2.11 --- Flow cytometry for cell cycle analysis --- p.53 / Chapter 2.12 --- Flow cytometry for cell apoptosis analysis --- p.54 / Chapter 2.13 --- Protein degradation assay --- p.54 / Chapter 2.14 --- Western blot analysis --- p.55 / Chapter 2.15 --- Immunofluorescence staining --- p.56 / Chapter 2.16 --- Plasmids construction --- p.58 / Chapter 2.16.1 --- pRFFL plasmid --- p.58 / Chapter 2.16.2 --- pMIR-RFFL-3’UTR and pMIR-RFFLmut-3’UTR --- p.58 / Chapter 2.17 --- Construction of stable cell lines --- p.59 / Chapter 2.18 --- Dual-luciferase reporter assay for p53 signaling pathway --- p.61 / Chapter 2.19 --- Dual-luciferase reporter assay for RFFL 3’UTR and miR-133a binding activity --- p.62 / Chapter 2.20 --- 5-Aza-2'-deoxycytidine (5-Aza-dC) treatment --- p.62 / Chapter 2.21 --- Tumour xenografts in nude mice model (miRNA intratumoural injection model) --- p.63 / Chapter 2.22 --- Tumour xenografts in nude mice model (miRNA stable cell line subcutaneous injection) --- p.64 / Chapter 2.23 --- Statistical analysis --- p.64 / Chapter CHAPTER THREE --- RESULTS --- p.66 / Chapter 3.1 --- Identification of differentially expressed miRNAs in CRC --- p.66 / Chapter 3.2 --- miR-133a is down-regulated in primary human CRC and colon cancer cell lines --- p.69 / Chapter 3.3 --- Ectopic expression of miR-133a inhibits tumourigenic properties of CRC cells --- p.75 / Chapter 3.3.1 --- miR-133a suppresses cell viability and colony formation --- p.75 / Chapter 3.3.2 --- miR-133a inhibits tumour growth in nude mice --- p.78 / Chapter 3.3.3 --- miR-133a suppresses cell cycle progression --- p.81 / Chapter 3.4 --- G0/G1 phase arrest by miR-133a is mediated through up-regulation of CDKN1A and CDKN1B --- p.83 / Chapter 3.5 --- miR-133a activates p53/p21 pathway through stabilization of p53 protein --- p.88 / Chapter 3.5.1 --- miR-133a induces p21 expression in a p53 wild-type cells --- p.88 / Chapter 3.5.2 --- miR-133a induces p21 promoter transcription activity and p53 binding activity --- p.90 / Chapter 3.5.3 --- Silence of p53 abolished miR-133a induced p21 --- p.92 / Chapter 3.5.4 --- miR-133a increases p53 activity through increase of p53 protein stability --- p.95 / Chapter 3.5.5 --- miR-133a has no effect on c-Myc level --- p.98 / Chapter 3.6 --- miR-133a increases p53 protein level by directly down-regulating RFFL --- p.100 / Chapter 3.7 --- Knock-down of RFFL inhibits cancer cell growth --- p.105 / Chapter 3.8 --- miR-133a sensitized CRC cells to chemotherapeutic drugs treatment --- p.110 / Chapter 3.9 --- Pharmacological demethylation restores miR-133a expression in CRC cells --- p.117 / Chapter 3.10 --- Association between miR-133a expression in tumour and clinicopathological characteristics of CRC patients --- p.119 / Chapter 3.11 --- Validation of other dysregulated miRNAs in CRC --- p.123 / Chapter CHAPTER FOUR --- DISCUSSION --- p.128 / Chapter 4.1 --- Biological role of miR-133a as a tumour suppressor --- p.128 / Chapter 4.2 --- p53/p21 pathway is a critical mediator of miR-133a in CRC --- p.129 / Chapter 4.3 --- Functional significance of RFFL in miR-133a induced p53/p21 signaling --- p.131 / Chapter 4.4 --- Clinical potential of miR-133a in CRC --- p.133 / Chapter 4.5 --- Other dysregulated miRNA --- p.136 / Chapter 4.6 --- Limitations and improvements of the study --- p.136 / Chapter 4.7 --- Conclusions --- p.137 / REFERENCE --- p.139 / PUBLICATIONS --- p.153

Eukaryotic translation elongation factor-2 (EEF2) is regulated through phosphorylation by a specific kinase known as eukaryotic elongation factor-2 kinase (EEF2K), leading to translational down regulation. Currently, it has been reported that EEF2K could promote the autophagic survival in breast and glioblastoma cell lines. However, the precise function of EEF2K in cancer as well as the related mechanism is still poorly understood. Colorectal cancer is the third common malignant disease worldwide and more than half of the patients with colorectal cancer require chemotherapy after surgery. However, de novo or acquired resistance to the agents is common. Discovery of novel targets for the chemotherapeutic intervention or treatment of colorectal cancer is highly warranted. In this study, the role of EEF2K as well as the underlying mechanism involved was evaluated in HT-29 and HCT-116 human colon cancer cells. Contrary to the reported autophagy-promoting activity of EEF2K in certain cancer cells, EEF2K is shown to negatively regulate autophagy in colon cancer cells as indicated by the increase of LC3-II levels, the accumulation of LC3 dots per cell, and the promotion of autophagic flux in EEF2K silenced cells. Moreover, the silencing of EEF2K promotes the cell viability, clonogenicity, cell proliferation and cell size in colon cancer cells. The silencing of BECN1 and ATG7 significantly reduce silencing of EEF2K induced LC3-II accumulation and cell survival. However, autophagy induced by EEF2K silencing does not potentiate the anticancer efficacy of the AKT inhibitor MK-2206. In addition, EEF2K overexpression decreases the cell survival and potentiates the antitumor efficacy of oxaliplatin. Autophagy induced by silencing of EEF2K is attributed to induction of protein synthesis, which results in ATP consumption and then actives AMPK-ULK1 pathway. This process appears independent of the suppression of MTOR activity and ROS generation. Silencing of AMPK or ULK1 significantly decreases EEF2K silencing-induced autophagy as well as cell survival in colon cancer cells. In conclusion, EEF2K negatively regulates autophagic survival through the AMPK-ULK1 pathway in colon cancer cells. This study provide useful information in understanding the role of EEF2K in colon cancer cells and suggests that upregulation of EEF2K activity may be developed a novel approach for the treatment of human colon cancer. / 真核延伸因子2激酶 (EEF2K) 通過磷酸化修飾真核延伸因子2 (EEF2) 來調控其活性，進而下調蛋白質翻譯延伸的速度。目前，有研究表明在乳腺癌和多形性膠質母細胞瘤中，EEF2K能夠誘導細胞自噬，並且這種類型的細胞自噬有助於細胞生存。然而，對於EEF2K在腫瘤中的精確作用以及它所涉及的分子機理仍然知之甚少，有待於進一步的研究。結直腸癌是全球第三大惡性腫瘤疾病，約有半數以上的患者需要手術後進行化學藥物治療。然而，患者對目前已有藥物的耐藥性十分普遍，因此，研發新的化學藥物靶點或者新的治療方法十分必要。在本課題研究中，EEF2K的功能及其所涉及的分子機理在人結腸癌細胞系HT-29和HCT-116上進行了闡釋。與在某些特定種類腫瘤細胞中EEF2K能夠誘導細胞自噬產生的現象相反，在EEF2K表達下調的人結腸癌細胞中，細胞自噬標記物LC3-II表達上升， 細胞中LC3斑點的聚集增多，並且細胞自噬流增強的現象，都表明EEF2K在這類腫瘤細胞中負調控細胞自噬。在結腸癌細胞中，EEF2K表達下調能夠增強細胞的活力，單細胞克隆的形成，細胞增殖以及細胞大小。此外，沈默BECN1和ATG7基因的表達都能夠減少EEF2K下調引發的LC3-II積累以及細胞增殖。然而，降低EEF2K表達所引發的細胞自噬並不能夠增強AKT抑制劑MK-2206抗腫瘤的效果。EEF2K的過表達能夠減少細胞增殖並且加強oxaliplatin的抗腫瘤藥效。沈默EEF2K引發的細胞自噬是通過誘導蛋白質的合成，導致ATP的消耗進而激活AMPK-ULK1細胞通路，與MTOR活性的抑制及ROS的產生無關。在結腸癌細胞中，降低AMPK或者ULK1的表達能夠消除EEF2K沈默所引起的LC3-II表達升高，細胞中LC3斑點聚集增多以及細胞增殖加強等現象。綜上所述，在人結腸癌細胞中，沈默EEF2K基因表達能夠通過激活AMPK-ULK1細胞通路，誘導有助於細胞存活的自噬現象產生。本課題研究對理解EEF2K在結腸癌細胞中的功能提供了有用的信息並且表明增強EEF2K的活性可以作為一種潛在的新的治療人結腸癌的方法。 / Liu, Xiaoyu. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 116-131). / Abstracts also in Chinese. / Title from PDF title page (viewed on 16, November, 2016). / Detailed summary in vernacular field only.

He, Jun. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 136-156). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

大腸癌是全世界最常見的癌症之一，亦是一個癌症死亡率的首要原因。大腸癌患者約50%在病程中會出現轉移病灶。近十年來，雖然多種被批准用於臨床治療的新化療藥顯著提高了大腸癌的治療效果，但是轉移性大腸癌病人的預後仍然很差。隨著各種分子生物技術的進步，新的治療標靶可能在大腸癌細胞株中被發現，並得以在病人標本中驗證。 / 在本研究中，我們採用即時定量多聚酶鏈反應(qPCR)陣列分析，比較大腸癌細胞株和正常大腸細胞株基因表達譜，試圖識別潛在的新的治療標靶。結果提示，與正常大腸細胞株 CCD-18Co 比較，Jagged 2 (JAG2) 和 Frizzled-3 (FZD3)基因 在大腸癌細胞株 SW480 和 SW620 中表達升高。病人大腸癌組織的免疫組織化學染色 (IS) 檢查進一步證實了上述結果，大腸癌組織較其癌旁正常組織表達3.1倍JAG2和6.6倍FZD3蛋白。因此， 我們假設JAG2和FZD3在大腸癌的發生中起重要作用。 / 為了檢驗該假設的真偽，我們運用RNA 干擾的方法進行功能缺失研究。通過該方法，大腸癌細胞株中JAG2 信使RNA和蛋白均能夠被下調，但是FZD3蛋白卻沒有顯示降低。為了弄清JAG2基因的功能，我們進行了單層細胞劃痕傷口癒合試驗和Matrigel 侵襲試驗。結果提示，JAG2 基因下調顯著抑制大腸癌細胞遷移和侵襲的能力。 / 為了調查參與上述功能的機制，我們利用腫瘤轉移相關基因的qPCR陣列分析，試圖檢測出JAG2基因敲除後上調或下調表達的轉移相關基因。結果顯示組織蛋白酶K (CTSK)，一種溶酶體半胱氨酸蛋白酶，在JAG2基因沉默的大腸癌細胞株中表達下調。為了闡明CTSK 活性在大腸癌細胞株侵襲能力中起到的作用，我們採用CTSK抑制劑處理大腸癌細胞株HCT116和DLD-1，發現這兩種細胞株的侵襲能力分別下降了36%和59%。總之, 這些發現表明CTSK可能是JAG2的下游靶基因，活性CTSK可能參與了JAG2介導的大腸癌細胞株侵襲能力。 / 以前的研究表明p38 MAPK通路參與癌細胞遷和侵襲能力的調控。通過Western blot方法，磷酸化的p38和磷酸化的STAT3被發現在JAG2基因沉默的大腸癌細胞中表達降低。p38抑制劑處理的 HCT116和DLD-1細胞降低了侵襲能力下降，同時遷移能力也由於p38抑制劑的處理而降低，支持p38可調控癌細胞遷移和侵襲能力的事實。 / 總之，我們的結果顯示JAG2高表達通過啟動CTSK和p38 MAPK通路，可能促進大腸癌轉移。因此，JAG2可能成為轉移性大腸癌治療的潛在標靶。 / Colorectal cancer (CRC) is one of the most frequent cancers worldwide and is a leading cause of cancer mortality. Around 50% of patients with CRC will experience metastases. Although significant progress has been made in CRC treatment within the last decade with the approval of multiple new chemotherapeutic agents, the prognosis for patients with metastatic CRC remains poor. With the advancement of molecular techniques, novel therapeutic targets are able to be discovered in CRC cell lines and validated in patient samples. / Therefore in this project, I aim to identify potential novel therapeutic targets by comparing the gene expression profile of colon cancer cell lines and a normal colon cell line using quantitative polymerase chain reaction (qPCR) arrays. Results showed that Jagged 2 (JAG2) and Frizzled-3 (FZD3) were up-regulated in the CRC cell lines SW480 and SW620 as compared to the normal colon cell line CCD-18Co. Those results were further validated by immunohistochemical staining (IS), which detected up-regulated JAG2 (3.1-fold) and FZD3 (6.6-fold) proteins expression in CRC tissues as compared to adjacent normal tissues. Thus I hypothesized that JAG2 and FZD3 may play an important role in CRC carcinogenesis. / In order to study the roles of FZD3 and JAG2 in CRC, loss-of-function studies by RNA interference (RNAi) were carried out. While the expression of FZD3 protein failed to be down-regulated by RNAi, JAG2 expression was successfully knocked down in CRC cell lines at both the mRNA and protein levels. Functional analyses using the monolayer scratch wound-healing assay and Matrigel invasion assay showed that JAG2 knockdown significantly inhibited migration and invasion in CRC cell lines. / To investigate the mechanisms involved, a tumour metastasis qPCR array was used to examine the changes in the expression level of metastasis-related genes after JAG2 gene knockdown. Results showed that the expression of Cathepsin K (CTSK), a lysosomal cystein protease, was found to be down-regulated in CRC cell lines following JAG2 silencing. To demonstrate the importance of CTSK activity in CRC cell invasion, HCT116 and DLD-1 CRC cell lines were treated with a CTSK inhibitor and its effect were assessed by the Matrigel invasion assay. Results showed that CTSK inhibition led to a 36% and 59% reduction in number of invaded cells in HCT116 and DLD-1 cell lines, respectively. Taken together, these findings show that CTSK may be a downstream target of JAG2 and that active CTSK may involve in JAG2 mediated invasion in CRC cell lines. / Previous works by others have shown that the p38 MAPK pathway is involved in the regulation of migration and invasive activity of cancer cell lines. Using Western blot analysis, the expression of phosphorylated p38 MAPK and phosphorylated STAT3 were found to be down-regulated following JAG2 depletion in CRC cell lines. In support of a role for p38 MAPK in the regulation of cancer cell migration and invasive capability, treatment with a p38 MAPK inhibitor was found to reduce the percentage of invasive cells and distance moved by migratory cells in HCT116 and DLD-1 cell lines. / In conclusion, my results show that JAG2 over-expression in CRC may promote cancer cell migration and invasion through activation of CTSK and the p38 MAPK pathway. Therefore, JAG2 may be a potential therapeutic target for treatment of metastatic CRC. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / He, Wan. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 164-207). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / Abstract in English --- p.i / Abstract in Chinese --- p.iv / Acknowledgements --- p.vi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Colorectal Cancer (CRC) --- p.1 / Chapter 1.1.1 --- Epidemiology and Incidence --- p.1 / Chapter 1.1.2 --- Histology --- p.2 / Chapter 1.1.3 --- Gender and Age --- p.4 / Chapter 1.1.4 --- Etiology of CRC --- p.4 / Chapter 1.1.4.1 --- Environment --- p.4 / Chapter 1.1.4.2 --- Hereditary Factors --- p.5 / Chapter 1.1.4.3 --- Dietary Factors --- p.6 / Chapter 1.1.4.4 --- Obesity --- p.6 / Chapter 1.1.4.5 --- Tobacco and alcoho --- p.7 / Chapter 1.1.4.6 --- Inflammatory bowel disease (IBC) --- p.7 / Chapter 1.1.5 --- Genetic Changes in CRC --- p.8 / Chapter 1.1.5.1 --- Chromosomal Aberration --- p.8 / Chapter 1.1.5.2 --- Tumor Suppressor Genes --- p.10 / Chapter 1.1.5.2.1 --- APC gene --- p.10 / Chapter 1.1.5.2.2 --- P53 gene --- p.11 / Chapter 1.1.5.2.3 --- SMAD4 gene --- p.11 / Chapter 1.1.5.3 --- Oncogenes --- p.12 / Chapter 1.1.5.3.1 --- Epidermal Growth Factor Receptor (EGFR) gene --- p.12 / Chapter 1.1.5.3.2 --- RAS gene and BRAF gene --- p.13 / Chapter 1.1.5.4 --- Proposed Two-hit Model for the Multistep Pathogenesis of CRC --- p.15 / Chapter 1.1.6 --- Clinical Presentation and Diagnosis --- p.16 / Chapter 1.1.7 --- Theatment --- p.16 / Chapter 1.1.7.1 --- Surgery --- p.16 / Chapter 1.1.7.2 --- Radiotherapy (RT) --- p.17 / Chapter 1.1.7.3 --- Concurrent Chemotherapy --- p.17 / Chapter 1.1.7.4 --- Target Therapy --- p.18 / Chapter 1.1.7.5 --- Colorectal Cancer Treatment by Stage --- p.19 / Chapter 1.1.7.6 --- Novel Strategies --- p.20 / Chapter 1.1.7.6.1 --- Epigenetic therapy --- p.20 / Chapter 1.1.7.6.2 --- Immunotherapy --- p.21 / Chapter 1.2 --- Pathways Involved in CRC Carcinogenesisand Progression --- p.22 / Chapter 1.2.1 --- Wnt Signaling Pathway --- p.22 / Chapter 1.2.2 --- Notch Signaling --- p.23 / Chapter 1.2.3 --- Nuclear Factor-kappa B (NF-κB) Signaling Pathway --- p.23 / Chapter 1.2.4 --- Phosphatidylinositol 3-kinase (PI3K) Signaling Pathway --- p.24 / Chapter 1.2.5 --- Crosstalk Among WNT, NOTCH, NF-κB and PI3K Signaling Pathway in CRC --- p.24 / Chapter 1.3 --- Hypothesis and Objectives of this Study --- p.28 / Chapter Chapter 2 --- Identification of Differentially Expressed Genes between Colorectal Cancer Cell Lines and A Normal Colon Cell Line --- p.29 / Chapter 2.1 --- Background --- p.29 / Chapter 2.2 --- Materials and Methods --- p.33 / Chapter 2.2.1 --- Cell Lines --- p.33 / Chapter 2.2.2 --- Identification of Differetially Expressed Genes by qPCR Arrays --- p.33 / Chapter 2.2.2.1 --- Total RNA Extraction --- p.33 / Chapter 2.2.2.2 --- RNA Quality Contol --- p.34 / Chapter 2.2.2.3 --- Reverse Transcription (RT) --- p.34 / Chapter 2.2.2.4 --- PCR Arrays --- p.34 / Chapter 2.3 --- Results --- p.36 / Chapter 2.3.1 --- Differentially Expressed Genes in WNT Signaling Pathway --- p.36 / Chapter 2.3.2 --- Differentially Expressed Genes in Notch Signaling Pathway --- p.40 / Chapter 2.3.3 --- Differentially Expressed Genes in NF-κB Signaling Pathway --- p.43 / Chapter 2.3.4 --- Differentially Expressed Genes in PI3K-AKT Signaling Pathway --- p.46 / Chapter 2.3.5 --- Choice of over-expressed genes for further validation and characterization --- p.49 / Chapter 2.4 --- Discussions --- p.53 / Chapter 2.4.1 --- WNT Signaling Pathway --- p.53 / Chapter 2.4.2 --- NOTCH Signaling Pathway --- p.54 / Chapter 2.4.3 --- NF-κB Signaling Pathway --- p.55 / Chapter 2.4.4 --- PI3K-AKT Signaling Pathway --- p.56 / Chapter 2.4.5 --- Choice of over-expressed genes for further validation and characterization --- p.56 / Chapter Chapter 3 --- JAG2, FZD3 and NOTCH4 Expression in Colorectal Cancer Cell Lines and Colorectal Cancer Tissues --- p.59 / Chapter 3.1 --- Background --- p.59 / Chapter 3.1.1 --- JAG2 Ligand --- p.59 / Chapter 3.1.2 --- FZD3 Receptor --- p.61 / Chapter 3.1.3 --- NOTCH4 Receptor --- p.62 / Chapter 3.2 --- Materials and Methods --- p.64 / Chapter 3.2.1 --- CRC Cell Lines --- p.65 / Chapter 3.2.2 --- CRC Tissues --- p.65 / Chapter 3.2.3 --- Quantitative RT-PCR --- p.66 / Chapter 3.2.4 --- Detection of JAG2, FZD3 and NOTCH4 Protein Expression in CRC Tissues by Immunohistochemical Staining (IS) --- p.67 / Chapter 3.2.5 --- Western Blot Assays --- p.68 / Chapter 3.2.5.1 --- Protein extraction --- p.68 / Chapter 3.2.5.2 --- SDS-PAGE gel electrophroresis --- p.68 / Chapter 3.2.5.3 --- Protein blotting --- p.68 / Chapter 3.2.6 --- Detection of JAG2 and FZD3 Protein Expression in CRC and Normal Colon Cell Lines by Western Blotting --- p.69 / Chapter 3.2.7 --- Statistical Analysis --- p.70 / Chapter 3.3 --- Results --- p.71 / Chapter 3.3.1 --- JAG2 and FZD3 but not NOTCH4 mRNA were Over -expressed in CRC Cell Lines --- p.71 / Chapter 3.3.2 --- Over-expression of JAG2 and FZD3 Proteins in CRC Tissues --- p.72 / Chapter 3.3.3 --- FZD3 Over-expression Correlated with Tumour-Node Metastasis (TNM) stages --- p.76 / Chapter 3.3.4 --- JAG2 and FZD3 Protein Expression in Colorectal Cancer and Normal Cell Lines --- p.77 / Chapter 3.4 --- Discussions --- p.78 / Chapter Chapter 4 --- Functional Analyses of JAG2 and FZD3 in CRC Cell Lines by RNA Interference --- p.81 / Chapter 4.1 --- Background --- p.81 / Chapter 4.2 --- Materials and Methods --- p.84 / Chapter 4.2.1 --- Transfection of siRNA into CRC Cell Lines --- p.84 / Chapter 4.2.2 --- Cell Proliferation Assay --- p.85 / Chapter 4.2.3 --- Monolayer Scratch Wound Healing Assay --- p.85 / Chapter 4.2.4 --- Matrigel Invasion Assay --- p.86 / Chapter 4.2.5 --- Statistical Analysis --- p.87 / Chapter 4.3 --- Results --- p.88 / Chapter 4.3.1 --- Knockdown of JAG2 and FZD3 Expression by RNA Interference --- p.88 / Chapter 4.3.2 --- Effect of JAG2 Knockdown on Migration of CRC Cell Lines --- p.91 / Chapter 4.3.3 --- JAG2 Knockdown by siRNA 2 Transfection Reduced Migratory Capability of HCT116, DLD-1and HT29 cell lines --- p.94 / Chapter 4.3.4 --- JAG2 Knockdown Impaired the Invasiveness of HCT116 and DLD-1 Cell Lines --- p.97 / Chapter 4.3.5 --- Decreased Migratory and Invasive Capabilities Induced by JAG2 Knockdown was not Due to Reduced Cell Proliferation --- p.100 / Chapter 4.4 --- Discussions --- p.102 / Chapter Chapter 5 --- NOTCH Pathway Inactivation by JAG2 Silencing Reduces Oncogenic Properties of HT29 but not HCT116 andDLD-1 CRC Cell Lines --- p.106 / Chapter 5.1 --- Background --- p.106 / Chapter 5.2 --- Materials and Methods --- p.109 / Chapter 5.2.1 --- CRC Cell lines --- p.109 / Chapter 5.2.2 --- Pharmacological Inhibition of NOTCH signaling by DAPT --- p.109 / Chapter 5.2.3 --- Combination of DAPT Treatment and JAG2 Silencing by siRNA --- p.109 / Chapter 5.2.4 --- Western Blotting --- p.109 / Chapter 5.2.5 --- Cell Proliferation Assay (MTS Assay) --- p.110 / Chapter 5.2.6 --- Monolayer Scratch Wound Healing Assay --- p.110 / Chapter 5.2.7 --- Matrigel Invasion Assay --- p.111 / Chapter 5.2.8 --- Statistical Analysis --- p.111 / Chapter 5.3 --- Results --- p.112 / Chapter 5.3.1 --- JAG2 Silencing Down-regulates Notch Pathway Signaling in CRC Cell Lines --- p.112 / Chapter 5.3.2 --- Inhibition of NOTCH Signaling by DAPT Treatment in CRC Cell Lines --- p.112 / Chapter 5.3.3 --- NOTCH Inhibition Does not Significantly Affect Cell Proliferation in CRC Cell Lines --- p.114 / Chapter 5.3.4 --- Suppression of NOTCH Signaling by DAPT Inhibits Migration in HT29 but not in HCT116 and DLD-1 CRC Cell Lines --- p.115 / Chapter 5.3.5 --- Suppression of NOTCH Signaling by DAPT does not Significantly Affect Invasiveness of HCT116 and DLD-1 CRC Cell Lines --- p.117 / Chapter 5.4 --- Discussions --- p.118 / Chapter Chapter 6 --- JAG2 Knockdown Inhibits Invasion in CRC Cell Lines through Inactivation of Cathepsin K --- p.121 / Chapter 6.1 --- Background --- p.121 / Chapter 6.2 --- Materials and Methods --- p.123 / Chapter 6.2.1 --- Human Tumour Metastasis RT2 Profiler[superscript TM] PCR Array --- p.123 / Chapter 6.2.2 --- Measurement of CTSK Gene expression level by Quantitative Real-Time PCR --- p.123 / Chapter 6.2.3 --- Immunohistochemical Staining (IS) of CTSK in CRC Tissues --- p.124 / Chapter 6.2.4 --- Pharmacological Inhibitior of CTSK in CRC Cell Lines --- p.124 / Chapter 6.2.5 --- Inhibition of CTSK in CRC Cell Lines for Migration Study --- p.124 / Chapter 6.2.6 --- Inhibition of CTSK in CRC Cell Lines for Invasion Study --- p.125 / Chapter 6.2.7 --- Western Blotting --- p.125 / Chapter 6.2.8 --- Statistical Analysis --- p.125 / Chapter 6.3 --- Results --- p.126 / Chapter 6.3.1 --- Identification of Metastasis Related Genes Which were Down-regulated by JAG2 Knockdown in HCT116 Cells --- p.126 / Chapter 6.3.2 --- Validation of Down-regulation of CTSK Gene by JAG2 Knockdown in HCT116 Cell Line by qRT-PCR --- p.126 / Chapter 6.3.3 --- JAG2 Knockdown Reduced Expression of Active CTSK Protein in CRC Cell Lines --- p.128 / Chapter 6.3.4 --- CTSK Protein Expression in CRC Tissue Samples --- p.130 / Chapter 6.3.5 --- Pharmacological Inhibition of CTSK Suppressed Invasiveness of CRC Cell Lines --- p.131 / Chapter 6.3.6 --- Pharmacological Inhibition of CTSK did not Affect Migration of CRC Cell Lines --- p.132 / Chapter 6.4 --- Discussions --- p.133 / Chapter Chapter 7 --- Depletion of JAG2 Inhibits Migration and Invasion in CRC Cell Lines through Inactivation of p38 MAPK/HSP27 Pathway --- p.137 / Chapter 7.1 --- Background --- p.137 / Chapter 7.2 --- Materials and Methods --- p.140 / Chapter 7.2.1 --- Pharmocological Inhibition of p38 MAPK Phosphorylation CRC Cell Lines --- p.140 / Chapter 7.2.2 --- Inhibition of p38 MAPK Phosphorylation for Migration Study in CRC Cell Lines --- p.140 / Chapter 7.2.3 --- Inhibition of p38 MAPK Phosphorylation for Invasion Study in CRC Cell Lines --- p.140 / Chapter 7.2.4 --- Knockdown of STAT3 by RNA interference --- p.141 / Chapter 7.2.5 --- Knockdown of STAT3 for Migration Study in CRC Cell Lines --- p.141 / Chapter 7.2.6 --- Knockdown of STAT3 for Invasion Study in CRC Cell Lines --- p.141 / Chapter 7.2.7 --- Western Blotting --- p.141 / Chapter 7.2.8 --- Statistical Analysis --- p.142 / Chapter 7.3 --- Results --- p.143 / Chapter 7.3.1 --- JAG2 Knockdown Inhibits p38 MAPK / HSP27 Pathway in CRC Cell Lines --- p.143 / Chapter 7.3.2 --- Inhibition of p38 MAPK / HSP27 Signaling Pathway Down-regulated Invasive Capability of CRC Cell Line --- p.145 / Chapter 7.3.3 --- Inhibition of p38 MAPK / HSP27 Signaling Pathway Down-regulated Migration of CRC Cell lines --- p.147 / Chapter 7.3.4 --- JAG2 Knockdown Inactivated p38 MAPK / HSP27 Pathway Independently of NOTCH Pathway in CRC Cell Lines --- p.149 / Chapter 7.3.5 --- JAG2 Knockdown Inhibits STAT3 Activation in CRC Cell Lines --- p.151 / Chapter 7.3.6 --- STAT3 Silencing Reduced Invasive Capability in CRC Cell Lines --- p.152 / Chapter 7.3.7 --- STAT3 Silencing Reduced Migratory Capability in CRC Cell Lines --- p.154 / Chapter 7.3.8 --- Inhibition of p38 MAPK Activity Suppressed STAT3 Activation in HCT116 Cells --- p.156 / Chapter 7.4 --- Discussions --- p.157 / Chapter Chapter 8 --- Conclusions and Future Works --- p.161 / Chapter 8.1 --- Conclusions --- p.161 / Chapter 8.2 --- Future work --- p.163 / References --- p.164 / Chapter Appendix 1 --- List of Figures and Tables --- p.208 / Chapter Appendix 2 --- Abbrevations used in this thesis --- p.212

Background & Aims: By whole genome sequencing, we identified for the first time that solute carrier family 12 member 5 (SLC12A5) gene located on chromosome 20q13.12 was amplified in colorectal cancer (CRC). We aimed to determine the amplification status of SLC12A5 and its clinical implication in CRC, and characterize the functional mechanisms of SLC12A5 in colorectal carcinogenesis. / Materials and Methods: Protein expression level of SLC12A5 was evaluated by immunohistochemistry. SLC12A5 amplification was verified by fluorescence in situ hybridization (FISH). The correlations between SLC12A5 expression and clinicopathologic parameters as well as the prognosis impact of SLC12A5 were analyzed in 195 CRC patients. The biological function of SLC12A5 in CRC cell lines were determined by cell viability, colony formation, invasion, migration, flow cytometry and in vivo tumorigenicity assays. Standard tail vein metastatic assay was performed to examine the effect of SLC12A5 in lung metastasis in nude mice. Western blot, luciferase reporter assays and human tumor metastasis PCR array were performed to evaluate SLC12A5 downstream effectors and related pathways. / Results: RT-PCR showed SLC12A5 was readily expressed in 7 of 9 CRC cell lines, but was absent in normal colorectal tissues. The mean protein expression level of SLC12A5 was significantly higher in primary CRCs as compared to their adjacent normal tissues. Amplification of SLC12A5 was detected in 40.8% (78/191) of primary CRCs by FISH, which was positively correlated with its protein overexpression (P < 0.001). Overexpression of SLC12A5 was positively associated with a more advanced TNM stage (P < 0.05). Multivariate Cox regression analysis showed that SLC12A5 overexpression was an independent predictor of poorer survival of CRC patients (P = 0.018). We further tested the biological function of SLC12A5 in human colon cancer cells. Ectopic expression of SLC12A5 in colon cancer cells SW480 and SW1116 increased proliferation and colony formation. Silencing SLC12A5 expression in HCT116 by siRNA had the opposite effects in vitro, and knockdown of SLC12A5 by shRNA significantly inhibited xenograft tumor growth in nude mice. We further revealed that SLC12A5 inhibited apoptosis of colon cancer cells by mediating apoptosis-inducing factor (AIF) and endonuclease G (EndoG) -dependent apoptotic signaling pathway. Moreover, gain-and loss-of-function experiments showed that SLC12A5 enhanced cell invasion and migration in vitro. Knockdown of SLC12A5 by shRNA significantly inhibited lung metastasis in nude mice. SLC12A5 promoted tumor metastasis through regulating key elements of the matrix architecture, such as matrix metallopeptidase and fibronectin. / Conclusion: We have identified a novel amplification gene SLC12A5 which is overexpressed in CRC. SLC12A5 may be an independent prognostic marker for CRC and may play a pivotal oncogenic role in colorectal carcinogenesis by inhibiting apoptosis and promoting metastasis. / 背景和目的：通過對結直腸癌進行全基因組測序，我們首次發現位於染色體20q13.12的SLC12A5基因在結直腸中擴增。本研究旨在探索SLC12A5在結直腸癌中的擴增情況和臨床意義，并進一步研究SLC12A5在結直腸癌發生發展中的作用機制。 / 材料和方法：採用免疫组化方法檢測SLC12A5的蛋白表达水平。應用熒光原位雜交方法驗證SLC12A5基因的擴增情況。在195例結直腸癌患者中对SLC12A5表达與临床病理關係及其對預後的影響其进行分析。通过檢測細胞活力、細胞集落形成實驗、侵襲實驗、遷移實驗、流式細胞術和體內成瘤實驗以研究SLC12A5在結直腸癌中的生物学功能。進而通過免疫印跡、熒光素酶報告實驗和人腫瘤轉移的PCR陣列，探索SLC12A5調控的基因和相关途径。 / 结果：我們採用RT-PCR方法檢測SLC12A5在9株結直腸癌細胞株的表達情況，SLC12A5在7株結直腸癌細胞株中穩定表達，但是在正常大腸組織中表達沉默。SLC12A5在結直腸中的平均蛋白表達水平顯著高於其鄰近的正常組織。通過熒光原位雜交方法，在40.8% （78/ 191）的結直腸癌中檢測到SLC12A5的擴增，該基因的擴增與其蛋白高表達水平呈正相關關係。SLC12A5高表達水平跟晚期TNM分期密切相關（P <0.05）。多因素Cox回歸分析表明，SLC12A5高表達是結直腸癌患者較差的生存的獨立預測因子（P = 0.018）。我們進一步在人結腸癌細胞株中檢測SLC12A5的生物功能。在結腸癌細胞SW480和SW1116中過度表達SLC12A5促進細胞增殖和集落形成。siRNA敲低HCT116 細胞SLC12A5的表達在體外實驗中有相反的效果。此外，shRNA敲低SLC12A5的表達顯著抑制裸鼠移植瘤的生長。我們進一步發現，SLC12A5通過介導凋亡誘導因子（AIF）和核酸內切酶G（EndoG）-依賴的細胞凋亡信號轉導通路抑制結腸癌細胞的凋亡。此外，功能獲得性和功能缺失性的體外實驗表明，SLC12A5促進腫瘤細胞的侵襲和遷移。尾靜脈注射實驗表明shRNA敲低SLC12A5的表達顯著抑制裸鼠肺轉移。SLC12A5通過調節基質結構的關鍵因子，如基質金屬蛋白酶和纖維連接蛋白，促進腫瘤轉移。 / 结论：我們發現了一個新的擴增基因SLC12A5，該基因在結直腸癌中高表達。SLC12A5是結直腸癌的一個獨立的預後標誌物。SLC12A5通過抑制細胞凋亡和促進腫瘤轉移，在結直腸癌的發生發展中起了舉足輕重的致癌作用。 / Xu, Lixia. / Thesis Ph.D. Chinese University of Hong Kong 2014. / Includes bibliographical references (leaves 107-120). / Abstracts also in Chinese. / Title from PDF title page (viewed on 05, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

The relationship between colorectal cancer (CRC) and folate metabolism is complex. Dietary folate, depending on the timing and dose, may either prevent or enhance tumour initiation and/or growth, and polymorphisms in the genes encoding folate-metabolising enzymes may also modulate risk. In this thesis, the Apcmin/+ mouse model of CRC was used to investigate the effect of nutritional and genetic disturbances in folate metabolism on tumourigenesis and to examine various mechanisms. / The reduced folate carrier I (RFC1) is responsible for the cellular uptake and intestinal absorption of folate, primarily the 5-methyltetrahydrofolate (5-methylTHF) derivative. Methionine synthase (MTR) uses 5-methylTHF to remethylate homocysteine to methionine, which may be activated and used to methylate substrates such as DNA. 5-MethylTHF is also the product of the methylenetetrahydrofolate reductase (MTHFR)-catalysed reduction of 5,10-methyleneTHF, which is also used to convert dUMP to dTMP. / Adenoma number and load were reduced in Rfc1+/-Apc min/+ mice, compared with Rfc1+/+Apc min/+ mice, but were similar in Mtr+/-Apc min/+ and Mtr+/+ Apcmin/+ mice. Neither Rfc1 nor Mtr genotype affected global DNA methylation, apoptosis or plasma homocysteine (tHcy) levels. In the experiments involving Mtr mice, dietary folate deficiency increased adenoma number, plasma tHcy, and apoptosis, and decreased global DNA methylation. Neither Mtr nor Rfc1 genotype affected the dUTP/dTTP ratio in the intestine of mice not predisposed to adenoma formation. / Adenoma number was decreased in Mthfr+/-Apc min/+ mice (compared with Mthfr+/+Apc min/+ mice) and in Mthfr+/+Apc min/+ offspring of Mthfr+/- mothers (compared with Mthfr+/+Apcmin/+ offspring of Mthfr+/+ mothers). A folate-deficient diet, when initiated prior to conception, significantly decreased adenoma number and decreased global DNA methylation. Overall, adenoma number was inversely correlated with plasma tHcy, dUTP/dTTP ratio and apoptosis. When initiated at three weeks of age, a folate-enriched diet significantly increased adenoma number in Apcmin/+ mice. In the intestines of mice not predisposed to adenoma formation, Mthfr deficiency decreased, and folic acid deficiency increased, the dUTP/dTTP ratio. / These results support the evidence that MTHFR polymorphisms are protective in CRC tumourigenesis and that depending on stage or predisposition, folate may inhibit or enhance tumour growth.

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Colorectal cancer (CRC), with an estimated 1.2 million new cases annually, is the third leading cause of cancer incidence and death worldwide. Generally, the majority of CRC patients are diagnosed at the advanced stages with poor prognosis and unfavorable response to multiple therapeutic drugs. In spite of increasing knowledge of the molecular mechanism for the tumorigenesis in CRC patients, the translation from basic science into clinical therapy has been limited for quite a long time. In order to develop novel treatment strategies against CRC, intensive and extensive attempts have been made in the past decades. / The epithelial to mesenchymal transition (EMT) is a multi-step process characterized by the loss of cell polarity, decreased cell-cell adhesion as well as enhanced migration and invasion capacity. It is well documented that EMT is essential for a variety of cellular biological events ranging from embryogenesis to tumor progression. The field of lncRNA is developing rapidly and currently it is one of the most intensively studied fields in the biomedical sciences. Emerging evidence indicates that the majority of human genome encodes thousands of non-protein-coding RNA transcripts, nevertheless, the function of long non-coding RNAs (lncRNAs) in orchestrating EMT progression remains elusive. Historically, the lncRNA H19 was the first identified imprinted non-coding RNA transcript in human, and the H19/IGF2 locus acted as an ideal paradigm for the investigation of genomic imprinting genes. In recent years, the expression profiling and functional characterization of the H19 gene in a variety of human diseases has been extensively studied. / In our studies, H19 was characterized as a novel regulator of EMT in colon cancer. We first observed significant mesenchymal characteristics in the methotrexate-resistant HT-29 cells. Interestingly, significant upregulation of H19 was observed in mesenchymal-like MTX resistant HT-29 cells. We subsequently demonstrated that after treatment of TGF-β1, one of the most widely used EMT inducers, H19 presented dramatic increase during the EMT progression. To further investigate the functional role of H19 in EMT, we generated the stable cell lines overexpressing H19 in colon cancer cells using retroviral infection. Stable overexpression of H19 significantly promoted EMT progression in two epithelial colon cancer cell lines HT-29 and HCT-116. However, overexpression of H19 did not affect cell proliferation as well as cell cycle progression. Further proteomics studies screened out that ectopic expression of H19 upregulated the protein level of Vimentin, a vital biomarker for mesenchymal cells. By using the bioinformatics study in combination with luciferase reporter assays, we demonstrated that H19 potentiated the expression of several core marker genes essential for mesenchymal cells by serving as a competing endogenous RNA(ceRNA), which builds up the missing link between the regulatory miRNA network and EMT progression. According to the results from xenograft tumor model and soft agar assay, stable expression of H19 reinforced the in vitro and in vivo tumor growth. Moreover, the investigation of clinical specimens verified that H19 RNA level was significantly increased in colon cancer tissues compared with corresponding adjacent normal tissues. Taken together, the above observations imply that the lncRNA H19, by acting as a competing endogenous RNA, is an important regulator which tightly modulated the expression of multiple important genes involved in EMT and it could probably serve as a novel therapeutic target against colon cancer. / 大腸癌每年有一百二十萬新增個案，是世界第三大癌症殺手。通常情況下，大部分大腸癌病人發現時已經處於晚期，該時期的癌症病人對多種臨床治療藥物已無法治愈。盡管關於大腸癌發病的分子生物學機制已經不斷完善，但如何從基礎研究轉化為臨床治療手段在很長一段時間內不可實現。為了進一步研究新的抗擊大腸癌治療手段，廣泛且深入的研究已經不斷開展。 / 上皮間充質轉化是一個多步驟的過程，該過程的典型特徵為失去細胞的極性，細胞間粘連減弱以及細胞爬行遷移能力的不斷加強。目前科學家已經知道上皮間充質轉化對於從胚胎發育到腫瘤發展都起著重要的作用。近年來，長非編碼RNA的研究不斷快速發展，已然成為醫學研究中最激烈的領域之一。眾多證據表明人體基因組編碼數以千計不編碼蛋白質的RNA轉錄體。然而，這些RNA轉錄體在上皮間充質轉化中的功能依然所知甚少。長非編碼RNA H19是人體內第一個被鑒別出來參與到基因印記的非編碼RNA。資料表明H19/IGF2位點是一個非常理想的研究基因印記的位點。近年來，H19在眾多癌症中的表達以及功能學研究已不斷湧現，同時也不斷取得令人鼓舞的研究成果。 / 在我們的研究中，H19被鑒定為大腸癌裏上皮間充質轉化過程中一個重要的參與者。通過研究甲氨蝶呤耐藥大腸癌HT-29細胞株，我們發現該HT-29耐藥細胞株有著顯著的間充質細胞特性。有趣的是，H19在該細胞株中有著顯著升高。我們隨後用經典的上皮間充質轉化誘導劑TGF-β1處理兩株大腸癌細胞，處理後H19亦有著顯著升高。為了進一步研究H19在上皮間充質轉化，通過使用逆轉錄病毒，我們建立H19的穩定表達細胞株。穩定表達H19顯著地促進了HT-29以及SW620大腸癌細胞株的上皮間充質轉化。然後，高水平表達(過表達)H19並不影響細胞的生長以及細胞周期的進程。進一步的蛋白質組學研究表明，過表達H19能促進間充質細胞一個重要標記基因Vimentin的表達。通過生物信息學以及熒光素酶報告基因實驗，我們證明了H19通過其競爭內源性RNA的作用，能夠促進間充質細胞所需的幾個重要基因的表達。該發現建立起了miRNA網絡以及上皮間充質轉化進程的交流網絡。通過異位移植以及軟瓊脂實驗，我們發現過表達H19能夠促進腫瘤細胞的生長。而在臨床大腸癌病人組織中，我們更發現H19在大腸癌病人組織中高表達。綜上所述，我們的結果證明H19這一長非編碼RNA，能夠通過其競爭內源性RNA的作用機制，從而調控上皮間充質轉化過程中的關鍵基因。同時H19亦有可能成為治療大腸癌的臨床新靶點。 / Liang, Weicheng. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 95-124). / Abstracts also in Chinese. / Title from PDF title page (viewed on 24, October, 2016). / Liang, Weicheng.

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Bai Hsing Chen. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 89-94). / Abstracts in English and Chinese. / Acknowledgments --- p.ii / Publication --- p.iii / List of Abbreviations --- p.iv / List of Tables --- p.v / List of Figures --- p.vi / Abstract --- p.vii / 摘要 --- p.x / Table of Contents --- p.xii / Chapter Chapter 1 --- INTRODUCTION / Chapter 1.1 --- Molecular Biology in Cancer Development --- p.2 / Chapter 1.1.1 --- Cell Cycle and Cancer --- p.2 / Chapter 1.1.2 --- Oncogenes and Tumor Suppressor Genes --- p.4 / Chapter 1.1.3 --- Epigenetic Alteration in Tumor Cells --- p.6 / Chapter 1.2 --- Colorectal Cancer Development --- p.9 / Chapter 1.2.1 --- Epidemiology of Colorectal Cancer --- p.9 / Chapter 1.2.2 --- Adenoma-Carcinoma Sequence --- p.11 / Chapter 1.2.2.1 --- Hyperplastic (metaplastic) Polyps --- p.11 / Chapter 1.2.2.2 --- Aberrant Crypt Foci (ACF) --- p.13 / Chapter 1.2.2.3 --- Adenomas --- p.13 / Chapter 1.2.2.4 --- Serrated adenomas --- p.15 / Chapter 1.2.2.5 --- Colorectal Carcinomas --- p.16 / Chapter 1.2.3 --- Genetic alterations in CRC --- p.18 / Chapter 1.2.4 --- Epigenetic alterations in CRC --- p.21 / Chapter 1.2.5 --- Staging of Colorectal Cancer --- p.23 / Chapter 1.3 --- Hypothesis --- p.25 / Chapter 1.4 --- Aim of Study --- p.26 / Chapter Chapter 2 --- MATERIALS and METHODES / Chapter 2.1 --- Patient Populations --- p.28 / Chapter 2.2 --- Microdissection and Immunohistochemistry --- p.29 / Chapter 2.3 --- DNA Isolation and Modification --- p.31 / Chapter 2.3.1 --- DNA Extraction from Microdissected Tissues --- p.31 / Chapter 2.3.2 --- DNA Extraction from Frozen Biopsy --- p.31 / Chapter 2.3.3 --- Bisulfite Modification of DNA --- p.32 / Chapter 2.4 --- Detection of K-ras Mutation --- p.33 / Chapter 2.5 --- Methylation-specific PCR (MSP) --- p.36 / Chapter 2.6 --- Bisulfite DNA Sequencing --- p.42 / Chapter 2.7 --- Statistical analysis --- p.44 / Chapter Chapter 3 --- RESULTS / Chapter 3.1 --- Promoter Hypermethylation of Tumor Related Genes in the Progression of Colorectal Neoplasia --- p.46 / Chapter 3.1.1 --- Clinico-Pathological parameters --- p.46 / Chapter 3.1.2 --- "Frequencies of Promoter Hypermethylation in Colorectal Cancers, Adenomas and Normal Colonic Tissues" --- p.47 / Chapter 3.1.3 --- Promoter Hypermethylation in Multiple Genes --- p.50 / Chapter 3.1.4 --- Promoter Hypermethylation in Advanced vs. Non-advanced Adenoma --- p.50 / Chapter 3.1.5 --- Methylation Patterns in Paired Adjacent Tissues from Cancer Patients --- p.53 / Chapter 3.1.6 --- Immunohistochemistry --- p.55 / Chapter 3.1.7 --- K-ras mutation --- p.61 / Chapter 3.1.8 --- Clinicopathological Correlations with Promoter Hypermethylation --- p.64 / Chapter 3.2 --- DNA Methylation Spread within HLTF CpG Island in Colorectal neoplasia --- p.67 / Chapter Chapter 4 --- DISCUSSION / Chapter 4.1 --- Methylation is an early event in Colorectal Carcinogenesis --- p.72 / Chapter 4.1.1 --- Methylation is frequently detected in both adenoma and carcinoma --- p.74 / Chapter 4.1.2 --- Concurrent methylation in multiple genes --- p.76 / Chapter 4.1.3 --- Methylation in advanced and non-advanced colorectal adenomas --- p.76 / Chapter 4.1.4 --- Relationship between K-ras mutation and methylation --- p.78 / Chapter 4.1.5 --- Methylation in adjacent tissues --- p.80 / Chapter 4.2 --- DNA Methylation Spread in HLTF gene --- p.81 / Chapter 4.2.1 --- HLTF is Frequently Methylated in Gastrointestinal Neoplasm --- p.82 / Chapter 4.2.2 --- Methylation Spread Patterns in Cancers and Adenomas --- p.83 / Chapter 4.2.3 --- Age Dependent Methylation Spread --- p.85 / Chapter Chapter 5 --- CONCLUSION --- p.87 / References --- p.89