全球人類健康的頭號殺手--腫瘤目前仍是難以攻克的醫學難題。腫瘤的發生是一個復雜的過程，主要由促癌基因的異常增多或激活及抑癌基因（TSG）的缺失或功能喪失的累積效果導致。近年來基於非基因序列改變所致基因表達水平變化的表觀遺傳學的研究進展表明，啟動子區CpG島甲基化所致的表觀遺傳沉默是抑癌基因轉錄失活的重要機制。Ras和Wnt信號轉導通路在癌病的發生和發展過程中均起到重要的作用，因此針對該兩種信號通路的拮抗因子的表觀遺傳調控及功能學研究將為我們提供有研究及應用前景的候選抑癌基因。 / 作為一種重要的原癌基因，Ras家族基因具有致癌活性的點突變及其導致的過度激活的Ras信號通路被發現廣泛存在於大約30%的人類腫瘤中。然而在一些缺乏Ras基因突變的腫瘤類型中，持續激活的Ras信號通路仍然普遍存在並具有重要作用，昭示著除了Ras基因點突變以外的信號轉導異常激活的機制。與GTP的結合可激活Ras，而RasGAP家族蛋白可通過水解GTP達到使Ras失活的作用。通過采用微陣列比較基因組雜交(aCGH)的實驗手段我們發現6p21.3染色體區具有半接合子缺失， 並於此區域發現了候選抑癌基因RASA5。在以往的研究報道中，RASA5被命名為SynGAP且其功能研究僅限於神經系統。我們的研究發現不同於RasGAP家族的其它基因RASA2-4，RASA5廣泛表達於人類正常器官組織中，並特異性地在腫瘤細胞，特別是鼻咽癌(NPC)，食管鱗狀上皮細胞癌(ESCC)和乳腺癌這些具有野生型Ras基因但Ras信號通路仍被過度激活的細胞中被表觀遺傳沉默。RASA5的異位表達可有效促進腫瘤細胞的雕亡，抑制腫瘤細胞的生長、遷移及“幹性（stemness）“。同時，使用siRNA敲除內源性RASA5可以激發細胞的克隆形成及上皮-間質(EMT)轉化。RASA5的抑癌功能是通過調低Ras-GTP水平並進而抑制其下遊信號通路的活性實現的。過量表達具有致癌活性的點突變的Ras或RasGAP結構域缺失均可部分逆轉這種抑癌作用。此項研究首次證明了RASA5的抑癌功能。 / Wnt/Dvl/β-catenin信號轉導通路在人類腫瘤中存在廣泛的異常激活。我們發現DACT (Dpr/Frodo)家族成員TUSC-T2的表觀遺傳沉默是一種普遍存在於人類腫瘤中的現象。TUSC-T2編碼一種胞質蛋白，外源性表達TUSC-T2可促進腫瘤細胞雕亡並導致腫瘤細胞的克隆形成能力下降。TUSC-T2可與Dvl蛋白結合並下調其活化水平，從而保護GSK-3β蛋白不被Dvl蛋白抑制。GSK-3β可與Axin及APC蛋白形成蛋白質復合物，該復合物可捕捉並降解細胞內信號分子β-catenin。TUSC-T2的過量表達可以抑制β-catenin的激活及其向細胞核內的富集，並進一步阻止β-catenin在細胞核內與Lef/Tcf轉錄因子家族的作用及下遊特定原癌基因，例如c-Myc, CCND1及Fibronectin的表達。因此TUSC-T2具有抑制腫瘤細胞增殖、遷移及上皮-間質(EMT)轉化的作用。 / 綜上所述，我們的研究結果表明RASA5及TUSC-T2是具有抑癌功能的Ras或Wnt/Dvl/β-catenin信號轉導通路抑制因子，其表觀遺傳沉默導致的轉錄失活對於腫瘤的發生發展具有重要意義。同時，針對這兩種抑癌基因的進一步研究將為我們提供富有應用前景的腫瘤標記物。值得註意的是，RASA5課題的研究開創性地闡明了Ras信號通路的拮抗因子的表觀遺傳沉默是一種Ras信號轉導通路於腫瘤細胞中異常激活的新機制。 / Cancer is the top killer of the world, as well as the medical problem difficult to overcome. The conversion of a normal cell to a cancer cell is usually caused by upregulation of oncogenes and downregulation of tumor suppressor genes (TSGs). Epigenetic silencing has been proved to be important in TSGs inactivation, often through methylation of CpG-rich promoter regions. Ras and Wnt signaling pathways are both important for the tumorigenesis, epigenetic and functional studies of antagonists to Ras and Wnt signaling would provide us with candidate TSGs. / Ras is a well-known oncogene. Aberrant mutations of Ras genes occur in approximately 30% of human tumors, causing constitutively activated Ras signaling. However, in certain types of tumors with wild type Ras genes, abnormally activated Ras signaling is still a common and critical event, suggesting alternative mechanisms for Ras signaling hyperactivation. Ras is active when it is bound to GTP, while the hydrolysis of bound GTP and inactivation of Ras is catalyzed by Ras GTPase activating proteins (RasGAPs). Using 1-Mb array CGH (aCGH), we refined a small hemizygous deletion at the 6p21.3 chromosome region that contains a RasGAP family member gene RASA5, which used to be named as SynGAP and studied only in the neuron systems. We demonstrated that RASA5, rather than other RasGAP family members RASA2-4, is broadly expressed in human normal tissues while frequently epigenetically silenced in multiple tumors, especially in certain tumor types such as nasopharyngeal (NPC), esophageal (ESCC) and breast carcinomas (BrCa) with wild-type Ras while Ras cascade is still constitutively active. Ectopic expression of RASA5 led to apoptosis, growth and migration inhibition, as well as ‘stemness’ repression of tumor cells. Meanwhile, knockdown of RASA5 by siRNA promoted the tumor cell colony formation as well as epithelial-mesenchymal transition (EMT). The tumor-suppressive function of RASA5 was exerted through downregulating Ras-GTP level and further inactivating Ras signaling. Such an inhibitory effect could be partially abrogated in the presence of mutated, activated Ras or by deletion of the RasGAP domain. For the first time, our study refined the role of RASA5 as a tumor suppressor. / Wnt/DVL/β-catenin signaling pathway is aberrantly activated in a wide range of human cancers. We identified a DACT (Dpr/Frodo) family member TUSC-T2 as an epigenetically downregulated gene in human tumors. TUSC-T2 encodes a punctate cytoplasmic protein. Ectopic expression of TUSC-T2 dramatically inhibited tumor cell colony formation in silenced tumor cell lines, mainly through inducing apoptosis. TUSC-T2 interacts and downregulates Dishevelled (Dvl) protein, thus protecting glycogen synthase kinase 3β (GSK-3β) from inactivation by Wnt/Dvl and allowing GSK-3β to form a complex with Axin and APC to promote the phosphorylation and proteasomal degradation of β-catenin. Overexpression of TUSC-T2 disrupted β-catenin activation and accumulation in nuclei, thus preventing its binding to transcription factors of the Lef/Tcf family. This caused the downregulation of β-catenin target oncogenes such as c-Myc, CCND1 and Fibronectin as well as the inhibition of tumor cell proliferation and migration. We also observed that TUSC-T2 could inhibit tumor cell EMT. / Taken together, our data demonstrate that RASA5 and TUSC-T2 are functional tumor suppressors epigenetically silenced in multiple tumors through acting as negative regulators of the Ras or Wnt/Dvl/β-catenin cancer pathways, and could be developed as promising biomarkers for human tumors. Of note, our study reveals that epigenetic silencing of the Ras antagonist represents a new mechanism responsible for Ras aberrant activation in cancers with wild-type Ras. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Fan, Yichao. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 184-216). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Acknowledgements --- p.i / List of abbreviations --- p.ii-iii / List of tables --- p.iv / List of Figures --- p.v-vii / List of Publications --- p.viii-ix / Abstract in English --- p.x-xii / Abstract in Chinese --- p.xiii-xiv / Table of Contents --- p.xv / Chapter Chapter 1 --- Introduction and Literature Review --- p.1 / Chapter 1.1 --- Cancer epigenetics --- p.4 / Chapter 1.1.1 --- Epigenetic modifications --- p.5 / Chapter 1.1.1.1 --- DNA Methylation --- p.5 / Chapter 1.1.1.2 --- Histone modifications --- p.10 / Chapter 1.1.1.3 --- RNA interference --- p.14 / Chapter 1.1.1.4 --- Nucleosome positioning --- p.15 / Chapter 1.1.2 --- Epigenetic alteration induced Tumor suppressor genes (TSGs) silencing during carcinogenesis --- p.17 / Chapter 1.2 --- Epigenetic alterations in cancer pathways --- p.23 / Chapter 1.2.1 --- Brief introduction of cancer pathways --- p.23 / Chapter 1.2.2 --- Ras pathway --- p.25 / Chapter 1.2.2.1 --- Ras pathway and carcinogenesis --- p.25 / Chapter 1.2.2.2 --- Epigenetic regulation of RasGAP proteins in carcinogenesis --- p.28 / Chapter 1.2.2.3 --- Epigenetic silencing of other negative regulators of Ras signaling --- p.30 / RAS association domain family (RASSF) proteins --- p.30 / PTEN --- p.32 / Sprouty (SPRY) proteins --- p.33 / Chapter 1.2.2.4 --- Hypomethylation induced Ras oncogenes activation --- p.35 / Chapter 1.2.2.5 --- Ras mediates epigenetic regulation through feedback loop --- p.36 / Chapter 1.2.3 --- Wnt pathway --- p.43 / Chapter 1.2.3.1 --- Wnt signaling pathway and carcinogenesis --- p.43 / Chapter 1.2.3.2 --- Epigenetic silencing of negative regulators of Wnt signaling --- p.45 / Chapter 1.2.3.3 --- DACT family proteins and carcinogenesis --- p.48 / Chapter 1.3 --- Application of tumor specific epigenetic alterations as tumor biomarkers and therapeutic targets --- p.49 / Chapter 1.3.1 --- The potential and advantage of tumor specific epigenetic alterations used as tumor biomarkers and therapeutic targets --- p.49 / Chapter 1.3.2 --- Epigenetic-disrupted regulators of Ras signaling as tumor biomarkers and therapeutic targets --- p.50 / Chapter 1.3.3 --- Epigenetic-disrupted regulators of Wnt signaling as tumor biomarkers and therapeutic targets --- p.52 / Chapter Chapter 2 --- Aims of this study --- p.54 / Chapter 2.1 --- To identify epigenetically silenced candidate TSGs as antagonists to Ras or Wnt signaling --- p.55 / Chapter 2.2 --- To elucidate the functional of candidate TSGs --- p.56 / Chapter Chapter 3 --- Materials and Methods --- p.57 / Chapter 3.1 --- Cell lines, tumor samples and routine cell line maintenance --- p.57 / Chapter 3.2 --- Drug and stress treatments --- p.59 / Chapter 3.3 --- DNA and RNA extraction --- p.59 / Chapter 3.4 --- Semi-quantitative RT-PCR and Real time PCR --- p.60 / Chapter 3.5 --- Direct sequencing of PCR products --- p.67 / Chapter 3.6 --- CpG island analysis --- p.67 / Chapter 3.7 --- Bisulfite treatment --- p.67 / Chapter 3.8 --- Methylation-specific PCR (MSP) and bisulfite genomic sequencing --- p.68 / Chapter 3.9 --- Plasmid extraction --- p.69 / Chapter 3.9.1 --- Bacteria culture --- p.69 / Chapter 3.9.2 --- Mini-scale preparation of plasmid DNA --- p.70 / Chapter 3.9.3 --- Large-scale endotoxin-free plasmids extraction --- p.71 / Chapter 3.10 --- Construction of expression plasmids --- p.71 / Chapter 3.10.1 --- Gene cloning and plasmids construction of RASA5 --- p.71 / Chapter 3.10.2 --- Gene cloning and plasmids construction of TUSC-T2 --- p.74 / Chapter 3.11 --- Immunofluorescence Staining --- p.74 / Chapter 3.12 --- Colony formation assay --- p.76 / Chapter 3.13 --- Apoptosis assay --- p.77 / Chapter 3.14 --- Luciferase reporter assay --- p.78 / Chapter 3.15 --- Protein preparation and Western blot --- p.79 / Chapter 3.16 --- Ras Activity Assay --- p.80 / Chapter 3.17 --- Wound healing assay --- p.81 / Chapter 3.18 --- Matrigel invasion assay --- p.81 / Chapter 3.19 --- RNA Interference --- p.81 / Chapter 3.20 --- Statistical analysis --- p.82 / Chapter Chapter 4: --- Epigenetic disruption of Ras signaling through silencing of a Ras GTPase-activating protein RASA5 in human cancers --- p.83 / Chapter 4.1 --- Identification of RASA5 as a downregulated gene residing in the 6p21.3 deletion region --- p.86 / Chapter 4.2 --- RASA5 is widely expressed in human normal tissues but downregulated in tumor cell lines --- p.91 / Chapter 4.3 --- The tumor-specific downregulation pattern of RASA5 is unique in the RASA family genes --- p.95 / Chapter 4.4 --- RASA5 promoter CpG methylation resulted in its transcription inactivation --- p.96 / Chapter 4.5 --- Frequent methylation of RASA5 promoter in multiple primary tumors --- p.101 / Chapter 4.6 --- Cloning and characterization of human RASA5 --- p.104 / Chapter 4.7 --- RASA5 inhibits tumor cell clonogenicity through inducing apoptosis --- p.108 / Chapter 4.8 --- RasGAP domain is required for the tumor suppressive function of RASA5 --- p.111 / Chapter 4.9 --- Certain cancer types harbor wild type Ras but active Ras signaling, with RASA5 epigenetically silenced --- p.114 / Chapter 4.10 --- RASA5 antagonizes Ras signaling pathway --- p.117 / Chapter 4.10.1 --- RASA5 represses Ras signaling through downregulating Ras-GTP level --- p.117 / Chapter 4.10.2 --- Oncogenic mutant form of Ras abrogated colony formation inhibitory effect of RASA5 on tumor cells --- p.120 / Chapter 4.10.3 --- Knockdown of RASA5 promoted the tumor cell colony formation and Ras signaling activation --- p.122 / Chapter 4.10.4 --- RASA5 inhibits ERK1/2 nuclei translocation and activation --- p.123 / Chapter 4.10.5 --- RASA5 negatively regulates Ras target gene expression --- p.125 / Chapter 4.11 --- RASA5 inhibits tumor cell migration and invasion through the Ras/Rac/cofilin signaling --- p.127 / Chapter 4.12 --- RASA5 suppresses tumor cell epithelial-mesenchymal transition (EMT) and stemness --- p.133 / Chapter 4.13 --- RASA5 appears in the cellcell interaction region nanotubes --- p.139 / Chapter 4.14 --- Discussion --- p.141 / Chapter Chapter 5: --- The Wnt/Dvl signaling antagonist TUSC-T2 is a pro-apoptotic tumor suppressor epigenetically silenced in tumors and inhibits tumor cell proliferation and migration --- p.150 / Chapter 5.1 --- Expression of TUSC-T2 is downregulated in human tumors --- p.150 / Chapter 5.2 --- TUSC-T2 promoter methylation results in its transcriptional inactivation --- p.151 / Chapter 5.3 --- Cloning and characterization of TUSC-T2 --- p.155 / Chapter 5.4 --- TUSC-T2 inhibits tumor cell clonogenicity through inducing apoptosis --- p.157 / Chapter 5.5 --- TUSC-T2 inhibits Wnt/Dvl/β-catenin pathway --- p.161 / Chapter 5.6 --- TUSC-T2 suppresses cell migration and EMT through upregulating E-cadherin --- p.165 / Chapter 5.7 --- Discussion --- p.171 / Chapter Chapter 6: --- Conclusions --- p.176 / Chapter 6.1. --- RasGAP family member RASA5 is epigenetically silenced in human cancers, acting as a tumor suppressor through negatively regulating Ras signaling --- p.177 / Chapter 6.2. --- DACT family member TUSC-T2 functions as a candidate TSG silenced by promoter methylation and inhibits Wnt/Dvl/β-catenin pathway --- p.178 / Chapter Chapter 7: --- Future Studies --- p.181 / Chapter 7.1. --- Further functional study of RASA5 and TUSC-T2 --- p.181 / Chapter 7.2. --- Clinical application of epigenetic silenced candidate TSGs --- p.182 / Chapter 7.3. --- Further screening of candidate TSGs as antagonists to cancer pathways --- p.183 / Reference list --- p.184

Dab2是一個細胞內接頭蛋白和腫瘤抑制因子。在小鼠胚胎中，應用免疫熒光染色技術，從E8.5-E11.0 Dab2發現表達於肌節的生皮肌節中。從E8.5 E9.5，Dab2表達於生皮肌節的中部。在E10.5，Dab2表達於生皮肌節的腹外側唇部，與肌肉發育的早期標誌基因Pax3和 Myf5共定位。從E11.5-E14.5，Dab2表達於四肢與軀體的肌肉中,Dab2在出生後小鼠肌肉中的表達逐漸減弱。此外，因為肌肉正常發育需要很多細胞信號的調節並且Dab2已經發現調節MAPK, TGF-β和 Wnt信號轉導通路。這些發現預示了Dab2在肌肉發育和分化中可能具有重要作用。 / 為了進一步研究它在肌肉發育中的作用，非洲爪蟾的胚胎和C2C12 肌原細胞在此研究中分別被用作體內和體外的研究模型。原位雜交結果揭示非洲爪蟾的Dab2基因表達於其胚胎的肌節中，並與肌肉發育的標誌基因XPax3, XMyoD, XMef2c和 XMyos共定位於此。用morpholino敲低XDab2 在非洲爪蟾胚胎中的表達，下調了許多肌肉發育標誌基因的表達，例如：XPax3, XMyf5, XMef2c, XMyoS 和XAC100。與此同時，免疫熒光技術也檢測到MHC(MF20)和12/101在肌節中的表達下調。 / 來源於小鼠肌肉衛星細胞的C2C12肌原細胞系被用作體外模型來檢測Dab2基因在骨骼肌發育和分化中的作用。在C2C12肌原細胞被誘導分化形成肌管的過程中，Dab2基因在RNA和蛋白水平的表達被誘導性的升高。Dab2基因超表達能夠加速肌原細胞的融合，從而增加肌小管的形成。利用miRNA敲低Dab2基因的表達能夠減緩肌原細胞的融合，從而減少肌小管的形成。利用慢病毒shRNA技術我們得到了2個Dab2穩定敲低細胞系，命名為克隆5-2和克隆5-7。這兩個克隆具有減少或抑制減少或抑制肌小管形成的特點。蛋白免疫印跡實驗表明，磷酸化p38 MAPK的表達在這兩個克隆中被抑制。在克隆5-2中超表達Dab2基因能夠恢復肌小管的形成。這個研究表明Dab2基因在肌小管的形成過程中具有至關重要的作用。 / 利用Affymetrix微陣列技術，我們檢測並分析了在克隆5-2和對照細胞中差異表達的基因。235個探針（155個基因）的顯示出超過2倍的差異表達。在這155個基因中，127個基因下調表達，28個基因上調表達。熒光定量PCR結果顯示出與微陣列結果相一致的結果。這些差異表達基因的功能發現與肌肉系統的發育和功能具有顯著地聯系。它影響了與肌肉收縮，橫紋肌的收縮，肌前體細胞的分化和肌肉發育相關功能的基因。基因網絡分析結果揭示，在克隆5-2中Mef2c基因的下調表達可能是一個導致肌細胞分化抑制的原因。 Mef2c基因在克隆5-2中超表達能夠拯救肌細胞的分化。 / 總括來說，體內和體外實驗共同表明Dab2基因是一個肌肉發育和分化的正調控基因。 / Dab2 is an intracellular adaptor protein and a tumor suppressor. In mouse embryos, Dab2 was found to be expressed in the dermomyotome of somites from E8.5 to E11.0 using immunofluorescence staining, with expression first detected in the medial aspect of the dermomyotome at E8.5 and then co-localized with the early muscle markers Pax3 and Myf5 at the ventrolateral lip of the dermomyotome at E10.5. From E11.5 to E14.5, Dab2 was expressed in muscle masses of limb buds and the trunk. Dab2 expression in skeletal muscles was gradually decreased after birth. These observations suggested potential roles of Dab2 in the skeletal muscle myogenesis. In addition, since the normal development of skeletal muscles requires proper signal transduction, and Dab2 has been known to be involved in the MAPK, TGF-β and Wnt signaling pathways, Dab2 may therefore be important for the muscle development. / To determine the role of Dab2 in the skeletal muscle development, Xenopus laevis embryos and C2C12 myoblasts were employed as in vivo and in vitro models, respectively. In situ hybridization results showed that XDab2 was expressed in somites of Xenopus embryos and co-localized with the muscle markers XPax3, XMyoD, XMef2c and XMyos. Knockdown of XDab2 expression with antisense morpholinos down regulated the expression of several muscle markers in somites including XPax3, XMyf5, XMef2c, XMyoS and XAC100. Down-regulation of MHC and 12/101 were also observed in whole mount preparations and transverse sections of XDab2 morpholino-injected embryos after immunohistochemical staining. / The C2C12 cell line derived from mouse muscle satellite cells was then employed as an in vitro model to determine the role of Dab2 during early muscle development. When C2C12 myoblasts were induced to differentiate into myotubes, Dab2 expression was simultaneously increased at RNA and protein levels. Dab2 over-expression after transfection with Dab2 plasmids resulted in enhanced myoblast fusion and increased numbers of myotubes. Conversely, suppression of Dab2 expression with miRNAs resulted in reduced myoblast fusion and decreased numbers of myotubes. Lentiviral shRNA-mediated Dab2 stable knockdown reduced myotube formation in 2 representative stable clones, clone 5-2 and clone 5-7. Western blot analysis showed that expression of phospho-p38 MAPK was down-regulated in clone 5-2 and 5-7. Dab2 re-expression through plasmid-mediated transient transfection in clone 5-2 could partially restore the myotube formation. These observations therefore suggested that Dab2 plays essential roles in the formation of myotubes. / Comprehensive profiling of differentially expressed genes was performed with the Affymetrix microarray analysis between the Dab2-knockdown clone 5-2 and the C2C12 parental cell line. As compared to the parental cells, the clone 5-2 showed significant changes in the expression of 235 probe sets representing 155 genes (p<0.05) with 2 folds or greater changes. Among the 155 genes, 127 were down-regulated, while 28 up-regulated. qRT-PCR results were found to be consistent with the microarray results. Functions of the differentially expressed genes were found to be significantly associated with the development and functions of the muscular system. Knockdown of Dab2 affected the genes involved in muscle contraction, the contraction of striated muscle, differentiation of muscle precursor cells, and the development of skeletal muscle fibers. A network analysis and a gene expression study revealed that Mef2c down-regulation was related to the inhibition of myogenic differentiation in the clone 5-2. Furthermore, forced expression of Mef2c in the clone 5-2 could rescue the myogenic differentiation. / In conclusion, these results indicated that Dab2 is positive regulator of the skeletal muscle development and differentiation both in vivo and in vitro. / 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. / Shang, Na. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 211-227). / 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 / 摘要 --- p.iv / Acknowledgements --- p.vi / Table of contents --- p.vii / Abbreviation --- p.xiii / Chapter Chapter 1 --- General Introduction --- p.1 / Chapter 1.1 --- Characterizations of the Dab2 gene --- p.1 / Chapter 1.2 --- The role of Dab2 in Wnt/ beta-catenin signaling --- p.2 / Chapter 1.3 --- The role of Dab2 in TGF beta signaling --- p.3 / Chapter 1.4 --- The role of Dab2 in Ras-MAPK signaling --- p.4 / Chapter 1.5 --- The role of Dab2 in protein trafficking and endocytosis --- p.5 / Chapter 1.6 --- Dab2 expression and its functions. --- p.7 / Chapter 1.7 --- Somite and skeletal muscle development --- p.8 / Chapter 1.8 --- The formation of the somite and its structure --- p.9 / Chapter 1.9 --- The formation of dermomyotome and its function --- p.10 / Chapter 1.10 --- The formation of myotome and its function --- p.11 / Chapter 1.11 --- The formation of muscle fibers and musculatures --- p.12 / Chapter 1.12 --- The formation of satellite cells and its function in skeletal muscle differentiation --- p.12 / Chapter 1.13 --- The gene expression during skeletal muscle development and differentiation --- p.13 / Chapter 1.14 --- Dab2 genetically modified mice --- p.16 / Chapter 1.15 --- Objectives of this research --- p.17 / Chapter Figures and legends --- p.21 / Chapter Chapter 2 --- Expression of Dab2 in the mouse somites and skeletal muscles --- p.32 / Chapter 2.1 --- Introduction --- p.32 / Chapter 2.2 --- Materials and Methods --- p.34 / Chapter 2.2.1 --- Mouse embryos and tissue isolation --- p.34 / Chapter 2.2.2 --- Histological preparation of embryos and tissues --- p.34 / Chapter 2.2.3 --- Immunostaining using Tyramide signal amplification kits --- p.35 / Chapter 2.3 --- Results --- p.36 / Chapter 2.3.1 --- Dab2 expression in somites of the mouse embryos --- p.36 / Chapter 2.3.2 --- Dab2 expression in skeletal muscles of embryonic and postnatal mice --- p.36 / Chapter 2.3.3 --- Co-localization of Dab2 and Pax3 immunoreactivities with double immunofluorescence staining --- p.37 / Chapter 2.3.4 --- Co-localization of Dab2 and Myf5 immunoreactivities with double immunofluorescence staining --- p.38 / Chapter 2.3.5 --- Co-localization of Dab2 and Myogenin immunoreactivities with double immunofluorescence staining --- p.38 / Chapter 2.4 --- Discussion --- p.40 / Chapter 2.5 --- Summary --- p.42 / Chapter Table 2.1 --- p.44 / Chapter Figures and Legends --- p.45 / Chapter Chapter 3 --- Dab2 is a positive regulator of skeletal muscle development in Xenopus embryos --- p.58 / Chapter 3.1 --- Introduction --- p.58 / Chapter 3.2 --- Materials and Methods --- p.61 / Chapter 3.2.1 --- RNA extraction --- p.61 / Chapter 3.2.2 --- Reverse-transcription polymerase chain reaction (RT-PCR) --- p.61 / Chapter 3.2.3 --- Gene cloning and sequencing analysis --- p.61 / Chapter 3.2.4 --- Transformation --- p.62 / Chapter 3.2.5 --- Plasmid mini and midi-preparation --- p.62 / Chapter 3.2.6 --- Frogs and embryos handling --- p.63 / Chapter 3.2.7 --- Synthesis of mRNA for microinjection --- p.64 / Chapter 3.2.8 --- Microinjection --- p.64 / Chapter 3.2.9 --- Synthesis of DIG-labeled anti-sense RNA probe --- p.65 / Chapter 3.2.10 --- Whole mount in situ hybridization (WMISH) and whole mount immunohistochemical localization --- p.65 / Chapter 3.3 --- Results --- p.67 / Chapter 3.3.1 --- Cloning of Xenopus Dab2 long isoform and the sequence analysis --- p.67 / Chapter 3.3.2 --- Phylogenetic analysis --- p.67 / Chapter 3.3.3 --- RT-PCR analysis of Xenopus Dab2 (XDab2) expression --- p.68 / Chapter 3.3.4 --- Xenopus Dab2 spatial and temporal expression examined by WMISH analysis --- p.68 / Chapter 3.3.5 --- Dab2 expression in somites and its colocalization with myogenic transcription factors --- p.69 / Chapter 3.3.6 --- XDab2 knockdown led to down-regulation of myogenic transcription factors and muscle markers at the RNA level --- p.70 / Chapter 3.3.7 --- XDab2 knockdown led to down-regulation of muscle markers at the protein level --- p.70 / Chapter 3.3.8 --- XDab2 overexpression led to up-regulation of XPax3, XMyf5 and XMyoS --- p.71 / Chapter 3.4 --- Discussion --- p.72 / Chapter 3.5 --- Summary --- p.77 / Chapter Table 3.1 --- p.78 / Chapter Figures and Legends --- p.79 / Chapter Chapter 4 --- Potential roles of Dab2 in C2C12 myoblast differentiation --- p.99 / Chapter 4.1 --- Introduction --- p.99 / Chapter 4.2 --- Materials and Methods --- p.101 / Chapter 4.2.1 --- Cell culture and differentiation in vitro --- p.101 / Chapter 4.2.2 --- Cell sample preparation --- p.102 / Chapter 4.2.3 --- Real-time PCR --- p.102 / Chapter 4.2.4 --- SDS-PAGE --- p.103 / Chapter 4.2.5 --- Western blotting and immunodetection --- p.104 / Chapter 4.2.6 --- Plasmids used for transient over-expression --- p.105 / Chapter 4.2.7 --- Generation of miRNAs targeting at Dab2 --- p.105 / Chapter 4.2.8 --- C2C12 differentiation after transfection --- p.106 / Chapter 4.2.9 --- Immunohistochemical staining for myotubes --- p.106 / Chapter 4.2.10 --- Lentiviral shRNA mediated Dab2 stable knockdown --- p.107 / Chapter 4.2.10.1 --- shRNA Lentiviral Transduction Particles and sequence information --- p.107 / Chapter 4.2.10.2 --- Optimization of puromycin treatment on C2C12 myoblasts --- p.107 / Chapter 4.2.10.3 --- Determination of the optimal MOI for C2C12 --- p.108 / Chapter 4.2.10.4 --- Lentivirus transduction method --- p.109 / Chapter 4.2.10.5 --- Stable cell line generation --- p.109 / Chapter 4.2.11 --- Rescue experiments --- p.109 / Chapter 4.2.12 --- Serum starvation and FGF treatment --- p.110 / Chapter 4.2.13 --- Microarray and data analysis --- p.110 / Chapter 4.3 --- Results --- p.113 / Chapter 4.3.1 --- Expression of Dab2 during myogenesis --- p.113 / Chapter 4.3.2 --- Generation of miRNAs targeting at Dab2 --- p.113 / Chapter 4.3.3 --- Improvement of the transfection efficiency --- p.114 / Chapter 4.3.4 --- Knockdown efficiencies of the 4 miRNAs --- p.114 / Chapter 4.3.5 --- Down-regulation of Dab2 expression by transient transfection inhibited C2C12 differentiation --- p.115 / Chapter 4.3.6 --- Up-regulation of Dab2 expression by transient transfection enhanced myogenic differentiation --- p.116 / Chapter 4.3.7 --- Lentivirus-mediated Dab2 stable knockdown inhibited myotube formation --- p.117 / Chapter 4.3.8 --- Re-expression of Dab2 partially restored myogenic differentiation in the clone 5-2 --- p.120 / Chapter 4.3.9 --- Dab2 knockdown affected the MAPK signaling pathway --- p.122 / Chapter 4.3.10 --- Transcriptome and network analysis revealed changes of gene expression patterns in the C2C12 cell line after Dab2 knockdown --- p.123 / Chapter 4.3.11 --- Mef2c down-regulation was related to the inhibition of the myotube formation in the clone 5-2 --- p.126 / Chapter 4.4 --- Discussion --- p.128 / Chapter 4.4.1 --- Dab2 expression was found to be induced upon differentiation and down-regulated after myotube formation --- p.128 / Chapter 4.4.2 --- Dab2 was found to be a positive regulator of C2C12 differentiation --- p.129 / Chapter 4.4.3 --- Dab2 knockdown affected the MAPK signaling pathway --- p.131 / Chapter 4.4.4 --- Potential roles of Dab2 in myogenic differentiation revealed by transcriptome and network analysis --- p.133 / Chapter 4.4.5 --- Mef2c down-regulation may be involved in the inhibition of myogenic differentiation after Dab2 knockdown --- p.135 / Chapter 4.5 --- Summary --- p.138 / Chapter Table 4.1 --- p.141 / Chapter Table 4.2 --- p.142 / Chapter Table 4.3 --- p.143 / Chapter Table 4.4 --- p.144 / Chapter Table 4.5 --- p.147 / Chapter Table 4.6 --- p.148 / Chapter Table 4.7 --- p.149 / Chapter Figures and Legends --- p.150 / Chapter Chapter 5 --- Conclusions and discussion --- p.192 / Chapter 5.1 --- Dab2 expression in somites and skeletal muscles of mouse embryos --- p.192 / Chapter 5.1 --- Dab2 as a positive regulator for skeletal muscle development in Xenopus embryos in vivo --- p.194 / Chapter 5.3 --- Dab2 as a positive regulator of skeletal muscle development in vitro --- p.196 / Chapter 5.3.1 --- Dab2 was found to be a positive regulator of C2C12 differentiation --- p.196 / Chapter 5.3.2 --- Dab2 knockdown affected the MAPK signaling pathway --- p.198 / Chapter 5.3.3 --- Potential functions of Dab2 revealed by transcriptomeand network analysis --- p.200 / Chapter 5.3.4 --- Mef2c down-regulation was closely related to the inhibition of myogenic differentiation upon Dab2 knockdown --- p.202 / Appendix I --- p.204 / Appendix II --- p.205 / References --- p.211

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

by Xin-xia Tian. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (p. 195-212). / 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.

by Nellie Yuk Fei Chung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 111-120). / Abstract also in Chinese. / Abstract --- p.i / List of Abbreviations --- p.iii / Acknowledgements --- p.iv / Publication of this study --- p.vi / Table of Contents --- p.vii / Chapter Chapter1: --- Introduction --- p.1 / Chapter 1.1 --- Multiple Myeloma --- p.2 / Chapter 1.2 --- The Problem --- p.2 / Chapter Chapter2: --- Literature Review --- p.5 / Chapter 2.1 --- Molecular Genetics of Multiple Myeloma --- p.6 / Chapter 2.1.1 --- Cytogenetics --- p.6 / Chapter 2.2 --- Alterations of Proto-Oncogenes --- p.9 / Chapter 2.2.1 --- c-myc --- p.9 / Chapter 2.2.2 --- Ras --- p.10 / Chapter 2.2.3 --- Bcl-2 and Related Protein --- p.10 / Chapter 2.3 --- Alteration of Tumor-Suppressor genes --- p.11 / Chapter 2.3.1 --- p53 Gene Mutations --- p.11 / Chapter 2.3.2 --- Retinoblastoma (Rb) Gene --- p.11 / Chapter 2.3.3 --- p16 and p15 Genes --- p.13 / Chapter Chapter3: --- DNA Methylation and Cancers --- p.14 / Chapter 3.1 --- Role of DNA Methylation --- p.15 / Chapter 3.2 --- CpG Islands --- p.15 / Chapter 3.3 --- Abnormalities of DNA Methylation in Neoplasia --- p.16 / Chapter 3.3.1 --- DNA Hypomethylation in Cancer --- p.16 / Chapter 3.3.2 --- DNA Methyltransferase Activity in Cancer --- p.17 / Chapter 3.4 --- Regional DNA Hypermethylation in Cancer --- p.17 / Chapter 3.4.1 --- p16 and p15 Genes in Solid Tumors --- p.18 / Chapter 3.4.2 --- The p16 and p15 Genes in Leukemia and other Hematopoietic Malignancies --- p.19 / Chapter 3.4.3 --- Retinoblastoma Gene --- p.20 / Chapter 3.5 --- Mechanism Underlying the DNA Methylation Changes --- p.21 / Chapter Chapter4: --- Background of Study --- p.23 / Chapter 4.1 --- Background of Study --- p.24 / Chapter 4.2 --- Project Objectives --- p.27 / Chapter Chapter5: --- Materials and Methods --- p.29 / Chapter 5.1 --- Patients Samples --- p.30 / Chapter 5.2 --- Normal Controls --- p.30 / Chapter 5.3 --- Storage of the Samples --- p.32 / Chapter 5.4 --- Materials --- p.32 / Chapter 5.4.1 --- Chemicals --- p.32 / Chapter 5.4.2 --- Primers --- p.33 / Chapter 5.4.3 --- Enzymes --- p.35 / Chapter 5.5 --- Methods --- p.35 / Chapter 5.5.1 --- Cloning of p16 and p15 Exon 1 Probes for Southern Analysis --- p.35 / Chapter 5.5.1.1 --- PCR Amplification of p16 and p15 exon1 Probes from Normal Blood DNA --- p.35 / Chapter 5.5.1.2 --- Recovery and Purification of p16 and p15 Exon 1 DNA Fragment --- p.36 / Chapter 5.5.1.3 --- Ligation --- p.37 / Chapter 5.5.1.4 --- Transformation --- p.37 / Chapter 5.5.1.5 --- Plating --- p.38 / Chapter 5.5.1.6 --- Screening of Recombinant Plasmid --- p.38 / Chapter 5.5.1.7 --- Confirmation of Cloned DNA by Sequencing --- p.42 / Chapter 5.5.2 --- DNA Extraction and Purification --- p.45 / Chapter 5.5.2.1 --- DNA Extraction from Bone Marrow Aspirate and Peripheral Blood --- p.45 / Chapter 5.5.2.2 --- Isolation of Plasmid DNA from Transformant Cutures --- p.46 / Chapter 5.5.2.3 --- Qualification and Quantification of DNA --- p.49 / Chapter 5.5.3 --- Detection of Hypermethylation by Southern Analysis --- p.50 / Chapter 5.5.3.1 --- Restriction Enzyme Digestion --- p.50 / Chapter 5.5.3.2 --- Agarose Gel Electrophoresis --- p.51 / Chapter 5.5.3.3 --- Southern Transfer --- p.51 / Chapter 5.5.3.4 --- Membrane Fixation --- p.51 / Chapter 5.5.3.5 --- Recovery and Purification of p16 and p15 Exon 1 Probes from Plasmid --- p.52 / Chapter 5.5.3.6 --- Probe Labeling --- p.54 / Chapter 5.5.3.7 --- Purification of Radioactive labeled DNA --- p.54 / Chapter 5.5.3.8 --- Southern Hybridization --- p.55 / Chapter 5.5.3.9 --- Post Hybridization --- p.55 / Chapter 5.5.3.10 --- Autoradiography --- p.56 / Chapter 5.5.4 --- Polymerase Chain Reaction-Single Strand Conformational Polymorphism Analysis (PCR-SSCP) --- p.56 / Chapter 5.5.4.1 --- 5'- end Radioactive Labeling of Primer --- p.56 / Chapter 5.5.4.2 --- Amplification of Target Sequence by PCR --- p.57 / Chapter 5.5.4.3 --- Non-denaturing Polyacrylamide Gel Electrophresis --- p.57 / Chapter 5.5.4.4 --- Direct DNA Sequence of PCR Products --- p.58 / Chapter 5.5.5 --- Prevention of Overall Contamination in PCR --- p.60 / Chapter 5.5.6 --- "Sensitivity, Specificity Controls" --- p.62 / Chapter Chapter6: --- Results --- p.64 / Chapter 6.1 --- Patient Characteristics --- p.65 / Chapter 6.1.1 --- General Patient Characteristics --- p.65 / Chapter 6.1.2 --- Clinical and Laboratory Features --- p.65 / Chapter 6.2 --- Southern Blot Analysis of p16/p15 and Rb --- p.79 / Chapter 6.2.1 --- Absence of Deletions or hypermethylationin Normal Controls --- p.79 / Chapter 6.2.2 --- Absence of Homozygous Deletions or Mutationsin p16/15 and Rb among all MM Patients --- p.79 / Chapter 6.2.3 --- Hypermethylation of p16 --- p.89 / Chapter 6.2.4 --- Hypermethylation of p15 --- p.92 / Chapter 6.3 --- Hypermethylation of p16/p15 and Clinico-pathologic Correlation --- p.94 / Chapter Chapter7: --- Discussion --- p.97 / Chapter 7.1 --- "Absence of Homozygous Deletions, Gene Rearrangements and Mutations in p16/p15 and Rb" --- p.98 / Chapter 7.2 --- Hypermethylation of p16/p15-An Alternative Way for Gene Inactivation --- p.100 / Chapter 7.2.1 --- Methylation of p15 Gene --- p.101 / Chapter 7.2.2 --- Methylation of 5'-CpG Island of p16/p15 and Lack of Gene Expression --- p.102 / Chapter 7.2.3 --- Comparison of Methylation Status of Primary Samples and Cell Lines in MM --- p.103 / Chapter 7.2.4 --- Progressive Gene Inactivation by Random Methylation Errors --- p.104 / Chapter 7.2.5 --- The Lack of Correlation of Tumor Contents Revealed by the Southern Analysis and Morphologic Assessment --- p.105 / Chapter 7.3 --- Knudson's Two-hit Model of Tumorigenesis --- p.106 / Chapter 7.4 --- Inverse Relationship of p16 and Rb --- p.107 / Chapter 7.5 --- Implications of Our Findings --- p.109 / Chapter 7.6 --- Future Studies --- p.109 / References --- p.111

Xiong, Lei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 79-97). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.

BRCA1 preserves genome integrity through both homology-directed repair (HDR) and stalled fork protection (SFP). In vivo, BRCA1 exists as a heterodimer with the BARD1 tumor suppressor, and both proteins harbor a C-terminal BRCT domain with a phospho-recognition surface. Most pathogenic lesions of BRCA1 and BARD1 disrupt their respective BRCT domains, and BRCA1 BRCT phospho-recognition is required for its tumor suppression activity. Here we evaluate mice with mutations (Bard1S563F and Bard1K607A) that ablate Bard1 BRCT phospho-recognition. Although not affecting HDR, these mutations impair BRCA1/BARD1 recruitment to stalled replication forks, resulting in stalled fork degradation, chromosomal instability, and sensitivity to PARP inhibitors. However, Bard1S563F/S563F and Bard1K607A/K607A mice are not tumor-prone, indicating that ablation of SFP activity alone is insufficient for spontaneous tumor susceptibility. Nevertheless, since SFP, unlike HDR, is also impaired in Brca1/Bard1 heterozygous-mutant cells, SFP and HDR may contribute to distinct stages of tumor development in BRCA1/BARD1 mutation carriers.

Leung Chin-lung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 133-164). / Abstracts in English and Chinese. / Abstract --- p.iv / 摘要 --- p.vi / List of abbreviation --- p.viii / Chapter Chapter 1 --- Hepatocellular Carcinoma --- p.1 / Chapter 1.1 --- A Health Burden --- p.1 / Chapter 1.2 --- Pathology --- p.3 / Chapter 1.3 --- Epidemiology --- p.7 / Chapter 1.3.1 --- Global HCC distribution --- p.7 / Chapter 1.3.2 --- Age and Gender --- p.10 / Chapter 1.4 --- Risk Factors of HCC --- p.12 / Chapter 1.4.1 --- Hepatitis B virus (HBV) --- p.13 / Chapter 1.4.1.1 --- Chronic HBV infection --- p.13 / Chapter 1.4.1.2 --- Role of HBV in hepatocarcinogenesis --- p.16 / Chapter 1.4.1.2 a) --- Direct Oncogenesis --- p.16 / Chapter 1.4.1.2 b) --- Indirect Oncogenesis --- p.17 / Chapter 1.4.2 --- Hepatitis C virus (HCV) --- p.23 / Chapter 1.4.2.1 --- Chronic HCV infection --- p.23 / Chapter 1.4.2.2 --- Role of HCV in hepatocarcinogenesis --- p.23 / Chapter 1.4.3 --- Chemicals as liver carcinogens --- p.27 / Chapter 1.4.3.1 --- Aflatoxin Bi (AFB1) --- p.28 / Chapter 1.4.3.2 --- Vinyl chloride --- p.29 / Chapter 1.4.3.3 --- Alcoholic beverages --- p.29 / Chapter 1.4.4 --- Inborn Errors in Metabolisms --- p.30 / Chapter 1.4.4.1 --- Hereditary tyrosinemia --- p.30 / Chapter 1.4.4.2 --- Hereditary haemochromatosis --- p.30 / Chapter 1.4.4.3 --- α1-antitrypsin deficiency --- p.31 / Chapter 1.4.5 --- Liver lesions --- p.32 / Chapter 1.5 --- Genetic alterations in HCC --- p.33 / Chapter Chapter 2 --- Rationale of the study --- p.39 / Chapter Chapter 3 --- LOH study on 8p in HCC --- p.48 / Chapter 3.1 --- Introduction --- p.48 / Chapter 3.1.1 --- "Knudson's ""two-hit"" model and LOH" --- p.48 / Chapter 3.1.2 --- Microsatellite DNA and LOH study --- p.49 / Chapter 3.2 --- Materials and Methods --- p.51 / Chapter 3.2.1 --- Patients and Specimens --- p.51 / Chapter 3.2.1.1 --- Genomic DNA extraction from liver tissues --- p.53 / Chapter 3.2.1.2 --- Genomic DNA extraction from buffy coat --- p.55 / Chapter 3.3 --- LOH study on 8p in HCC --- p.57 / Chapter 3.3.1 --- Microsatellite markers --- p.57 / Chapter 3.3.2 --- 5-end labeling --- p.60 / Chapter 3.3.3 --- Amplification of microsatellite DNA --- p.60 / Chapter 3.3.4 --- Denaturing polyacrylamide gel electrophoresis --- p.61 / Chapter 3.3.5 --- Detection of LOH --- p.62 / Chapter 3.4 --- Results --- p.63 / Chapter 3.4.1 --- LOH status of 52 HCC cases --- p.63 / Chapter 3.4.2 --- Clinicopathological correlation --- p.67 / Chapter 3.4.3 --- Delineation of common deletion region (CDR) --- p.67 / Chapter 3.4.4 --- Common deletion region of interest --- p.77 / Chapter Chapter 4 --- Study on LZTS1 --- p.83 / Chapter 4.1 --- Introduction 一 LZTS1 --- p.83 / Chapter 4.2 --- Mutation analysis of LZTS1 in HCC --- p.87 / Chapter 4.2.1 --- Materials and Methods --- p.87 / Chapter 4.2.1.1 --- Patients and HCC cell lines --- p.87 / Chapter 4.2.1.2 --- Genomic DNA extraction from HCC cell lines --- p.87 / Chapter 4.2.1.3 --- Amplification of exons of LZTS1 --- p.89 / Chapter 4.2.1.3a) --- Primer pairs --- p.89 / Chapter 4.2.1.3b) --- PCR conditions --- p.90 / Chapter 4.2.1.4 --- Purification of PCR products --- p.93 / Chapter 4.2.1.5 --- Cycle sequencing reaction --- p.94 / Chapter 4.2.1.6 --- Purification of cycle sequencing reaction product --- p.94 / Chapter 4.2.1.7 --- Sequence analysis by automated sequencer --- p.95 / Chapter 4.2.1.8 --- Search for sequence variants of LZTS1 --- p.96 / Chapter 4.2.2 --- Results --- p.97 / Chapter 4.3 --- Expression analysis of LZTS1 in HCC with preliminary results --- p.103 / Chapter 4.3.1 --- Materials and Methods --- p.103 / Chapter 4.3.1.1 --- Patients and Specimens --- p.103 / Chapter 4.3.1.2 --- Total RNA extraction --- p.103 / Chapter 4.3.1.3 --- Reverse transcription --- p.104 / Chapter 4.3.1.4 --- Semi-quantitative PCR --- p.105 / Chapter 4.3.1.4a) --- Primer pairs --- p.105 / Chapter 4.3.1.4b) --- PCR conditions --- p.106 / Chapter 4.3.2 --- Results --- p.109 / Chapter Chapter 5 --- Discussion --- p.111 / Chapter 5.1 --- LOH study on 8p in HCC --- p.111 / Chapter 5.2 --- Study on LZTS1 in HCC --- p.125 / Chapter 5.2.1 --- Mutation analysis of LZTS1 --- p.125 / Chapter 5.2.2 --- Expression analysis of LZTS1 --- p.129 / Chapter 5.3 --- Future Study --- p.132 / References --- p.133

抑制腫瘤的基因（又稱抑癌基因）之表達失活，是導致癌變的重要機制之一。除了基因突變之外，越來越多研究證明抑癌基因的關閉轉錄，是由於抑癌基因啟動子區的CpG島甲基化所致。本論文的研究確定了兩個候選抑癌基因ADAMTS8和TUSC14，在多種腫瘤細胞株中經常因動子區的CpG島甲基化而下調或停止表達，這有別於它們在正常組織中廣泛表達的情況。沉默細胞株在脫氧核糖核酸甲基轉移酶的抑製劑5-氮-2'-脫氧胞苷(5-aza-2′-deoxycytidine; Aza) 或與組蛋白去乙酰化酶抑製劑曲古抑菌素A (trichostatin A, TSA)的去甲基化作用下，能恢復這兩個抑癌基因的表達，因而證明了啟動子甲基化是直接導致其表達下調及沉默的機制。 / 論文的第一部分，主要調查ADAMTS8啟動子區在原發腫瘤樣本被甲基化的比率，並研究其腫瘤抑制功能。含血小板凝血酶敏感蛋白基序的解整聯蛋白金屬蛋白酶 (ADAMTSs) ，在各種癌症中的表達異常已有報導。然而，它們在腫瘤的職能作用仍然模糊不清。本研究發現，異位表達ADAMTS8誘導細胞凋亡，因而顯著抑制腫瘤細胞克隆形成的能力,。這些都突顯其抑制腫瘤的功能。此外，作為分泌蛋白酶的ADAMTS8，能夠透過減少表皮生長因子受體(EGFR) 蛋白的磷酸化，抑制EGFR / MEK / ERK信號通路，並進一步破壞肌動蛋白應力纖維的組織，抑制腫瘤細胞的遷移性。 / 論文的第二部分，集中於研究一個未知功能的基因TUSC14，這基因的蛋白質編碼具有氨基末端蛋白質相互作用域 (BTB/POZ domain)及C₂H₂乙炔鋅指結構。TUSC14的異位表達能抑制腫瘤細胞克隆的形成，但這種抑制作用會在删除蛋白中的BTB/POZ或C₂H₂乙炔鋅指結構功能域後消失。因此證實了TUSC14蛋白同時需要BTB / POZ和C₂H₂乙炔鋅指結構兩個功能域來抑制腫瘤生長。此外，TUSC14具有抑制NF-kB轉錄的功能，其功能不但依賴於组蛋白去乙酰基酶(HDAC)，並且與c-MYC和cIAP-2等NF-κB靶基因下調表達相關。TUSC14的抑癌功能，包括抑制腫瘤生長與增加細胞凋亡，與其減少c-MYC及抗凋亡基因cIAP-2的表達，效果一致。進一步的分析發現，TUSC14與HDAC1和P65於蛋白質複雜免疫共沉澱實驗中，有物理相互作用。此外，染色質免疫沉澱實驗顯示TUSC14透過與c-MYC和cIAP-2的相互作用，抑制其基因啟動子區的轉錄功能。結果表明，TUSC14是通過招募HDAC至NF-κB靶基因的啟動子區這機制，來抑制NF-kB靶基因的轉錄，以達至抑制癌細胞生長和誘導癌細胞凋亡的效果。因此，TUSC14的沉默是破壞癌細胞中NF-kB信號通路負調控(negative regulation)的重要因素。 / 綜上所述，本研究鑒定了兩個在多種腫瘤細胞因表觀遺傳沉默效應而表達下調或沉默的抑癌基因ADAMTS8和TUSC14，並證實它們具有抑癌功能。 / Inactivation of tumor suppressor genes (TSGs) is one of the critical mechanisms leading to carcinogenesis. Apart from genetic mutations, a growing number of TSG has been shown to be silenced through promoter CpG methylation. In this thesis, we identified two candidate TSGs: ADAMTS8 and TUSC14 that are frequently downregulated or silenced in multiple carcinoma cell lines by promoter methylation while broadly expressed in normal tissues. Expression of these two genes was restored after treatment with DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (Aza) or in combination with a histone deacetylase inhibitor trichostatin A (TSA), suggesting promoter-methylation directly contributes to their silencing. / In the first part of the thesis, prevalence silencing of ADAMTS8 was detected in primary tumor samples. Expression of many disintegrins and metalloproteinases with thrombospondin motifs (ADAMTSs) was reported to be dysregulated in various cancers. However, their functional roles in tumorigenesis remain obscure. This study revealed that ectopic expression of ADAMTS8 markedly inhibits tumor cell clonogenicity by inducing apoptosis, underscoring its function as a tumor suppressor. Furthermore, ADAMTS8, as a secreted protease, inhibits EGFR/MEK/ERK signaling pathway by reducing their phosphorylation, further resulting in the disruption of actin stress fiber organization and suppression of tumor cell motility. / The second part of the thesis focused on a novel gene TUSC14 which encodes a protein with BTB/POZ domain and C₂H₂zinc-fingers. Ectopic expression of TUSC14 suppresses colony formation of cancer cells but this inhibitory effect is abolished with the deletion of BTB/POZ domain or C₂H₂ zinc-fingers. This suggested that both BTB/POZ domain and C₂H₂ zinc-fingers are required for inhibiting tumor cell clonogenecity. In addition, TUSC14 functions as a transcriptional repressor of NF-kB pathway that is dependent on HDAC. Suppression of NF-κB transcriptional activity by TUSC14 expression correlates with the downregulation of NF-κB target genes including c-MYC and cIAP-2. Reduction of c-MYC and anti-apoptotic cIAP-2 agrees well with the consequent growth suppression and enhanced apoptosis following the ectopic expression of TUSC14. Further analyses showed TUSC14 physically interacts with HDAC1 and p65 via co-immunoprecipitation assay. Preliminary ChIP assay showed that TUSC14 associates with gene promoters of c-MYC and cIAP-2 for their transcription repressions. These results revealed that TUSC14 represses NF-kB activity through recruiting HDAC to the NF-kB target genes; and transcription repression of NF-kB represents a mechanism for TUSC14 to mediate its growth inhibitory and apoptosis-inducing effects in cancer. Hence, silencing of TUSC14 contributes to the lost of negative regulation on NF-kB signaling in cancer. / In summary, this study demonstrated that ADAMTS8 and TUSC14 are functional tumor suppressors that are epigenetically silenced in multiple tumors. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Choi, Ching Gee. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 140-153). / Abstract also in Chinese. / Abstract --- p.i / Chinese abstract --- p.iv / AcknowledgEments --- p.vii / List of Figures --- p.ix / List of Tables --- p.xi / LIST OF ABBREVIATIONS --- p.xii / List of PUBLICATIONs --- p.xiv / Chapter CHAPTER 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview of cancer epigenetics --- p.1 / Chapter 1.2 --- Epigenetic events --- p.2 / Chapter 1.2.1 --- DNA methylation --- p.2 / Chapter 1.2.2 --- Histone modifications --- p.5 / Chapter 1.2.3 --- The interdependence of DNA methylation and histone modifications --- p.8 / Chapter 1.3 --- Epigenetic alterations in cancer --- p.9 / Chapter 1.3.1 --- Genome-wide DNA hypomethylation --- p.9 / Chapter 1.3.2 --- CpG island promoter hypermethylation silencing of tumour suppressor genes in tumorigenesis --- p.10 / Chapter 1.3.3 --- Aberrations of histone modifications --- p.11 / Chapter 1.4 --- Causes for epigenetic deregulation in cancer --- p.14 / Chapter 1.5 --- The interplay of genetic and epigenetic aberration in cancer progression --- p.21 / Chapter 1.6 --- Epigenetic inactivation of tumor suppressor genes in cancer --- p.23 / Chapter 1.7 --- Clinical implications of epigenetic research --- p.27 / Chapter 1.7.1 --- Epigenetic modifications as biomarker for cancer diagnosis --- p.27 / Chapter 1.7.2 --- Targeting epigenetic modifications as therapeutics towards cancers --- p.29 / Chapter 1.8 --- Roles of ADAMTS proteins in cancer --- p.32 / Chapter 1.8.1 --- Introduction on ADAMTS metalloproteases --- p.32 / Chapter 1.8.2 --- Deregulation of ADAMTS protein in cancer --- p.34 / Chapter 1.9 --- Roles of BTB/POZ-ZF family of transcription factors in cancer --- p.36 / Chapter 1.9.1 --- Introduction on BTB/POZ-ZF Family --- p.36 / Chapter 1.9.2 --- BTB/POZ-ZF functions as transcription repressors --- p.37 / Chapter 1.9.3 --- Many BTB/POZ-ZF proteins are important players in tumorigenesis --- p.39 / Chapter 1.9.4 --- The role of BTB/POZ-ZF in tumor initiation and progression --- p.40 / Chapter CHAPTER 2 --- Aims of this study --- p.44 / Chapter CHAPTER 3 --- General Methodology --- p.46 / Chapter 3.1 --- Cell Culture --- p.46 / Chapter 3.1.1 --- Growth and maintenance of cells --- p.46 / Chapter 3.1.2 --- Mammalian cell transfection --- p.46 / Chapter 3.1.3 --- Drug and stress treatments --- p.47 / Chapter 3.2 --- DNA and RNA extraction --- p.47 / Chapter 3.3 --- Semi-quantitative RT-PCR and Real-time PCR --- p.48 / Chapter 3.4 --- CpG island and Transcription factor binding sites analysis --- p.49 / Chapter 3.5 --- Methylation-specific PCR (MSP) and Bisulfite genomic sequencing (BGS) --- p.49 / Chapter 3.6 --- Bacterial transformation and Plasmid extraction --- p.50 / Chapter 3.6.1 --- Heat-shock transformation --- p.50 / Chapter 3.6.2 --- Mini-scale preparation of plasmid DNA --- p.51 / Chapter 3.6.3 --- Preparation of endotoxin-free plasmids --- p.52 / Chapter 3.7 --- DNA cycle sequencing --- p.52 / Chapter 3.8 --- Indirect immunofluorescence for subcellular localization study --- p.54 / Chapter 3.9 --- Colony formation assay --- p.54 / Chapter 3.10 --- Cell cycle analysis --- p.55 / Chapter 3.11 --- Apoptosis assay --- p.56 / Chapter 3.12 --- Co-immunoprecipitation and Western blot --- p.56 / Chapter 3.13 --- Chromatin immunoprecipitation (ChIP) --- p.58 / Chapter 3.14 --- Dual Firefly and Renilla luciferase reporter gene assay --- p.59 / Chapter 3.15 --- Statistical analysis --- p.60 / Chapter CHAPTER 4: --- Characterization of the Tumor Suppressive Functions of ADAMTS8 --- p.61 / Chapter 4.1 --- Introduction --- p.61 / Chapter 4.2 --- Materials and Methods --- p.64 / Chapter 4.2.1 --- Tumor samples --- p.64 / Chapter 4.2.2 --- Expression of ADAMTS8 --- p.64 / Chapter 4.2.3 --- Immunofluorescence staining of ADAMTS8 --- p.64 / Chapter 4.2.4 --- Detection of secreted ADAMTS8 in culture medium --- p.65 / Chapter 4.2.5 --- Collection of conditioned medium and Western Blotting --- p.66 / Chapter 4.2.6 --- Wound healing assay --- p.66 / Chapter 4.3 --- Result and Discussion --- p.69 / Chapter 4.3.1 --- Frequent ADAMTS8 methylation in primary carcinomas --- p.69 / Chapter 4.3.2 --- ADAMTS8 is a secreted protease --- p.70 / Chapter 4.3.3 --- ADAMTS8 inhibits phosphorylation of pEGFR --- p.73 / Chapter 4.3.4 --- ADAMTS8 suppresses cell migration --- p.77 / Chapter 4.4 --- Summary --- p.81 / Chapter CHAPTER 5: --- Epigenetic Alterations of TUSC14 Gene in multiple carcinomas --- p.83 / Chapter 5.1 --- Introduction --- p.83 / Chapter 5.2 --- Materials and Methods --- p.84 / Chapter 5.2.1 --- Cell lines --- p.84 / Chapter 5.2.2 --- Normal and primary tumor tissues --- p.85 / Chapter 5.3 --- Results and Discussion --- p.86 / Chapter 5.3.1 --- Expression profiling of TUSC14 in normal tissues and tumor cell lines --- p.86 / Chapter 5.3.2 --- Frequent inactivation of TUSC14 by promoter CpG methylation --- p.90 / Chapter 5.3.3 --- Pharmacologic and genetic demethylation restores TUSC14 expression --- p.94 / Chapter 5.3.4 --- Frequent TUSC14 methylation in primary tumors --- p.96 / Chapter 5.4 --- Summary --- p.98 / Chapter CHAPTER 6 --- Characterization of the Tumor Suppressive Functions of TUSC14 --- p.99 / Chapter 6.1 --- Introduction --- p.91 / Chapter 6.2 --- Materials and Methods --- p.100 / Chapter 6.2.1 --- Gene cloning and plasmids construction of TUSC14 --- p.100 / Chapter 6.2.2 --- Drug and stress treatments of cells --- p.100 / Chapter 6.3 --- Results and Discussion --- p.102 / Chapter 6.3.1 --- TUSC14 localizes to nuclear speckles --- p.102 / Chapter 6.3.2 --- TUSC14 inhibits clonogenicity --- p.107 / Chapter 6.3.3 --- Expression of TUSC14 induces apoptosis in tumor cells --- p.110 / Chapter 6.3.4 --- TUSC14 alters cell cycle progression --- p.112 / Chapter 6.3.5 --- TUSC14 acts as a transcriptional repressor of multiple genes --- p.114 / Chapter 6.3.6 --- TUSC14 represses NF-кB activity through an HDAC-dependent mechanism --- p.118 / Chapter 6.3.7 --- The effect of TUSC14 on the expression of downstream targets of NF-κB Signaling --- p.120 / Chapter 6.3.8 --- TUSC14 co-immunoprecipitates with HDAC1 and p65 --- p.124 / Chapter 6.3.9 --- ChIP analysis of promoters of TUSC14-regulated genes --- p.127 / Chapter 6.4 --- Summary --- p.130 / Chapter CHAPTER 7 --- General Discussion --- p.133 / Chapter CHAPTER 8 --- Conclusions --- p.138 / References --- p.140

Zheng Ping-pin. / Thesis submitted in: December 2001. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 118-159). / Abstracts in English and Chinese. / ACKNOWLEDGEMENTS --- p.i / ABSTRACT(ENGLISH/CHINESE) --- p.iii / CONTENTS --- p.viii / LIST OF TABLES --- p.xi / LIST OF FIGURES --- p.xii / PUBLICATION --- p.xiii / Chapter CHAPTER I --- INTRODUCTION / Chapter I.1. --- Preface --- p.1 / Chapter I.2. --- Overview of Carcinogenesis --- p.2 / Chapter I.3. --- Oncogene --- p.5 / Chapter I.4. --- Tumor Suppressor Genes (TSGs) --- p.6 / Chapter I.5 --- Detection of Oncogene and Tumor Suppressor Genes --- p.9 / Chapter I.5.1 --- Detaction of Oncogene --- p.9 / Chapter I.5.2. --- Detection of Tumor Suppressor Genes --- p.11 / Chapter I.6. --- Profiles of Oncogenes/TSGs and Molecular Subtype about Astrocytic Tumors --- p.17 / Chapter I.7. --- Intratumoral Heterogeneity and Microsatellite Instability --- p.20 / Chapter I.8. --- Outline of Ependymoma --- p.20 / Chapter I.9. --- Clinicopathological Factors and Prognosis --- p.22 / Chapter I.9.1. --- Histology and Grading (2000) --- p.22 / Chapter I.9.2. --- Prognosis Factors --- p.23 / Chapter I.9.2.1. --- Age/Sex/Location --- p.23 / Chapter I.9.2.2. --- Extent of Resection --- p.25 / Chapter I.9.2.3. --- Radiotherapy and Chemotherapy --- p.25 / Chapter I.9.2.4. --- Histology --- p.26 / Chapter I.10. --- "Cytogenetic, Molecular Genetic and Molecular Studies" --- p.27 / Chapter I.11. --- Advantages and Disadvantages of The Research Methods --- p.34 / Chapter CHAPTER II --- AIM OF STUDY --- p.36 / Chapter CHAPTER III --- MATERIALS AND METHODS --- p.37 / Chapter III.1. --- Tumor Samples and DNA Preparations --- p.37 / Chapter III.1.1. --- Tumor Samples --- p.38 / Chapter III.1.2. --- DNA Preparation --- p.38 / Chapter III.2. --- Comparative Genomic Hybridization --- p.42 / Chapter III.2.1. --- Metaphase Preparation --- p.42 / Chapter III.2.2. --- "DNA Labeling, Hybridization, and Detection" --- p.43 / Chapter III.2.3. --- Digital Image Analysis --- p.45 / Chapter III.3 --- High-Resolution Allelotying (Microsatellite Analysis) --- p.46 / Chapter III.3.1 --- General Outline --- p.46 / Chapter III.3.2 --- Multiplex PCR --- p.47 / Chapter III.3.3 --- Pooling of PCR Products --- p.49 / Chapter III.3.4 --- Electrophoresis --- p.50 / Chapter III.3.5. --- Assessment of Allelic Imbalance by Calculating Allelic Ratio --- p.52 / Chapter III.3.6 --- Standards of Evalution --- p.53 / Chapter III.3.7 --- Separating Allelic Loss from Allelic Duplication --- p.54 / Chapter III.3.8 --- Statistical Analyses --- p.54 / Chapter CHAPTER IV --- RESULTS --- p.54 / Chapter IV.1. --- CGH Study --- p.54 / Chapter IV.1.1 --- Overview --- p.54 / Chapter IV.1.2 --- Common Deletion Regions --- p.58 / Chapter IV.1.3 --- Common duplication Regions --- p.60 / Chapter IV.2. --- High-Resolution Allelotyping (Microsatellite Analysis) --- p.60 / Chapter IV.2.1. --- Overview of Results --- p.60 / Chapter IV.2.2. --- LOH profile of Individual Chromosome --- p.93 / Chapter IV.2.3. --- Overlapping Small Deletion Regions --- p.95 / Chapter CHAPTER V --- DISCUSSION --- p.97 / Chapter V.1. --- . General Outline --- p.98 / Chapter V.2. --- Chromosome 22 --- p.99 / Chapter V.3. --- Chromosome 17 --- p.102 / Chapter V.4. --- Chromosome 6 --- p.104 / Chapter V.5. --- Chromosome 16 --- p.105 / Chapter V.6. --- Chromosome 19 --- p.107 / Chapter V.7. --- Chromosome 20 --- p.108 / Chapter V.8. --- Chromosome 7 --- p.109 / Chapter V.9. --- Chromosome 12 --- p.110 / Chapter V.10. --- Chromosome 9 --- p.111 / Chapter V.11. --- Chromosome 5 --- p.112 / Chapter V.12. --- Chromosome 4 --- p.112 / Chapter V.13. --- Correlation of CGH with Allelotyping in the Study --- p.112 / Chapter V.14. --- Conclusion --- p.114 / Chapter CHAPTER VI --- LIMITATIONS OF THE STUDY --- p.115 / Chapter CHAPTER VII --- FUTURE STUDY --- p.116 / REFERENCES --- p.118