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published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

白血病由血液或骨髓中的癌細胞所形成，基於其造血幹細胞（HSC）的增殖和分化出現偶聯或不平衡的情況而產生的結果。白血病是香港最常見的兒童癌症，報告指出，於2005年至2009年期間，平均每年約有270名患者死於該病。傳統治療白血病的方法包括化療，放射性治療，骨髓或外周血幹細胞移植，至於採用哪種療法，則要視乎白血病的類型和階段。然而，這些療法會為患者帶來各種副作用，因此，在過去十年間，研發新型治療白血病的藥物引起了越來越多人的關注。 / 共軛脂肪酸（CFA），是指一群位置及幾何異構體的多元不飽和脂肪酸（PUFA），於它們的化學結構中，最少有一組共軛雙鍵。天然的共軛脂肪酸包括，存在於反芻動物的肌肉及乳製品中的共軛雙烯酸（CLA），存在於植物種子油中的共軛三烯酸（CLN），以及存在於海藻中的共軛四烯酸，共軛五烯酸（CEPA）和共軛六烯酸（CDHA）。過往的研究證實了共軛雙烯酸擁有各種生理及醫藥功效，包括抗脂肪分化，抗動脈硬化，抗糖尿病，免疫調節和抗腫瘤作用。根據體外實驗報告指出，共軛三烯酸和共軛四烯酸對多種腫瘤細胞株皆具有生長抑制作用，然而，它們對小鼠巨噬細胞樣的白血病細胞之調節作用和機制仍有待研究。因此，在這篇論文中，共軛三烯酸和共軛四烯酸對小鼠巨噬細胞樣的白血病細胞的抗增殖作用，以及它們引起的相關機制將會被探討。 / 本實驗計劃研究了九個不同的多元不飽和脂肪酸異構體對小鼠巨噬細胞樣的白血病細胞PU5-1.8細胞的抗增殖能力，當中包括三烯酸、四烯酸、共軛雙烯酸、共軛三烯酸和共軛四烯酸的異構體。結果清楚地表明，共軛三烯酸和共軛四烯酸異構體皆能對白血病細胞表現出劑量依賴性的生長抑制作用。於十個異構體當中，順式-8，反式-10，順式-12共軛三烯酸(蘭花酸)和順式-9，反式-11，反式-13，順式-15共軛四烯酸(杷茬酸)較其他共軛脂肪酸異構體更有效抑制白血病細胞的生長，因此，他們被選定為主要的研究對象，以便對它們所引起的相關機制作進一步了解。此外，蘭花酸和杷茬酸對其他小鼠巨噬細胞樣的白血病細胞，包括J774 A.1細胞和P388D1細胞，也具備抗增殖作用，表現其生長抑制作用並不是純粹針對單一種腫瘤細胞株的。有趣的是，蘭花酸和杷茬酸對PU5-1.8細胞的生長抑制作用是可以局部逆轉的，但只限以低濃度的共軛脂肪酸培養白血病細胞以及培養的時間不多於24小時，否則，隨著培養的時間增加或共軛脂肪酸的濃度增加時，該生長抑制作用幾乎是不可逆轉的。另一方面，結果也表明蘭花酸和杷茬酸在其抑制白血病細胞增殖率為五十百分比之濃度下，它們對腫瘤細胞以及小鼠正常細胞的毒性作用是很少的。除了在體外研究，預先以蘭花酸處理的PU5-1.8細胞於BALB/c小鼠內導致白血病細胞生長的能力也以劑量依賴方式被抑制。 / 幾種不同的機制也能解釋蘭花酸和杷茬酸對PU5-1.8細胞的生長抑制能力，當中包括阻礙腫瘤細胞週期的前進，增加腫瘤細胞內活性氧（ROS）的生產或誘導腫瘤細胞的凋亡。研究結果指出，蘭花酸和杷茬酸可以抑制PU5-1.8細胞週期的進程並將其停留在G₀/G₁時相，換來的是減少處於S時相的細胞的比例。此外，透過西方蛋白質印跡分析，細胞週期蛋白E的表達有所下調，同時，幾個細胞週期調控蛋白的表達，包括p21，p27及p53蛋白則被上調，跟上述的實驗結果吻合。此外，經蘭花酸和杷茬酸處理後，PU5-1.8細胞內的ROS濃度和線粒體質量也有所增加，而它們對白血病細胞的生長抑制作用則會被抗氧化劑所減弱，這一點說明了蘭花酸和杷茬酸對PU5-1.8細胞的抗增殖作用可能與細胞內的脂質過氧化物濃度和線粒體質量有關。最後，通過各種測試細胞凋亡的實驗，包括利用細胞死亡檢測的ELISA{U+1D3E}{U+1D38}{U+1D41}{U+1D40}試劑盒，Annexin-V和JC-1染色等方法，清楚地表明了蘭花酸和杷茬酸能誘導PU5-1.8細胞的凋亡。加上西方蛋白質印跡分析，PU5-1.8細胞內Bcl-2和Bcl-XL的蛋白的表達水平有所下降，而相反Bax蛋白的表達水平則有所提升，足以證明蘭花酸和杷茬酸能引發PU5-1.8細胞的凋亡。 / 總括來說，蘭花酸和杷茬酸對PU5-1.8細胞的抗增殖作用呈現時間和劑量依賴性，該作用可能基於阻礙腫瘤細胞週期的前進，增加腫瘤細胞內ROS的生產或誘導腫瘤細胞的凋亡。由於蘭花酸和杷茬酸分別在植物種子油和海藻的含量相當高，再加上它們對正常細胞無直接毒性，若果能夠對它們的抗腫瘤作用以及其分子機制有更透徹的理解，它們有望發展成為未來治療白血病的藥物。 / Leukemia is a cancer of the blood or bone marrow which is the result of uncoupling or imbalance of the proliferation and differentiation of hematopoietic stem cells (HSC). It is the most common childhood cancer in Hong Kong and it claims the lives of around 270 patients per year from 2005 to 2009 in average. Conventional approaches to leukemia therapy include chemotherapy, radiotherapy and bone marrow or peripheral blood stem cell transplantation, depending on the types and stages of leukemia. Nevertheless, these therapies are accompanied by a number of undesirable effects to the patients, hence, the development and research in novel treatments of leukemia are attracting increasing attention in the past decades. / Conjugated fatty acids (CFA) refer to the positional and geometric isomers of polyunsaturated fatty acids (PUFA) with conjugated double bonds. Naturally-occurring CFA include conjugated linoleic acids (CLA) from meat and dairy products of ruminant animals, conjugated linolenic acids (CLN) from plant seed oils, conjugated tetraenoic acids, conjugated eicosapentaenoic acids (CEPA) and conjugated docosahexaenoic acids (CDHA) from seaweeds. CLA have been shown to possess various biological and pharmacological activities, including anti-adipogenic, anti-atherogenic, anti-diabetogenic, immunomodulatory and anti-tumor effects. Furthermore, previous researches have demonstrated the growth-inhibitory effects of CLN and conjugated tetraenoic acids on a wide variety of cancer cell lines in vitro, however, their modulatory effects and action mechanisms on murine macrophage-like leukemia cells remain poorly understood. In this thesis project, the anti-proliferative effects of CLN and conjugated tetraenoic acids on the murine macrophage-like leukemia cells, as well as their action mechanisms will be elucidated. / Nine different PUFA isomers, including linolenic acid, tetraenoic acid, CLA, CLN and conjugated tetraenoic acids were examined for their anti-proliferative effects on the murine macrophage-like leukemia PU5-1.8 cells. The results clearly showed that all CLN isomers and cis-parinaric acid could exhibit growth-inhibitory effects on the leukemia cells in a dose-dependent manner. It was found that jacaric acid and cis-parinaric acid were relatively more potent than the other isomers used in the present study, hence, they were chosen to be the specific targets for more in-depth mechanistic studies. In addition, the anti-proliferative effects of jacaric acid and cis-parinaric acid were observed in other murine macrophage-like leukemia cell lines, including J774 A.1 cells and P388D1 cells, suggesting that the effects were not cell-line specific. Interestingly, the growth-inhibitory effects were partially reversible at lower concentrations of CFA used within 24 hours of incubation, but the effects were almost irreversible when either the incubation time or the concentration of CFA used was increased. Furthermore, the results showed that both jacaric acid and cis-parinaric acid at their IC₅₀ growth-inhibitory concentrations on PU5-1.8 cells exerted minimal, if any, direct cytotoxic effects on the tumor cells as well as the murine normal cells. Apart from the in vitro studies, it was also demonstrated that pre-treatment of PU5-1.8 cells with jacaric acid could significantly decrease the leukemic cell growth in syngeneic BALB/c mice in a dose-dependent manner. / Several mechanisms were proposed for the anti-proliferative effects of jacaric acid and cis-parinaric acid on PU5-1.8 cells, including the triggering of cell cycle arrest, increasing the production of intracellular reactive oxygen species (ROS) or induction of apoptosis in the tumor cells. The results showed that jacaric acid and cis-parinaric acid could inhibit the cell cycle progression since an accumulation of PU5-1.8 cells at the G₀/G₁ phase was observed, together with a decrease in the cell population at the S phase. This finding was supported by the down-regulation of cyclin E protein and up-regulation of several cell cycle regulatory proteins, including the p21, p27 and p53 proteins. Apart from that, the intracellular ROS concentration and the mitochondrial mass were found to be increased in jacaric acid- or cis-parinaric acid-treated PU5-1.8 cells, and their growth-inhibitory effects were alleviated after the addition of antioxidants. Therefore, the anti-proliferative effects of jacaric acid and cis-parinaric acid on PU5-1.8 cells might be correlated with the intracellular concentration of lipid peroxides and the mitochondrial mass. Furthermore, the results clearly demonstrated that both jacaric acid and cis-parinaric acid exhibited dose-dependent apoptosis-inducing effects on PU5-1.8 cells, as revealed by the Cell Death Detection ELISA{U+1D3E}{U+1D38}{U+1D41}{U+1D40} kit, annexin V assay and JC-1 dye staining method. In addition, it was found that the expression levels of Bcl-2 and Bcl-xL proteins were decreased, whereas the expression level of Bax protein was increased in PU5-1.8 cells, further confirming that apoptosis occurred in PU5-1.8 cells after treatment with jacaric acid and cis-parinaric acid. / Collectively, the results showed that jacaric acid and cis-parinaric acid could exhibit their anti-proliferative effects on PU5-1.8 cells in a time- and dose-dependent manner, through the triggering of cell cycle arrest, increasing the production of intracellular ROS or induction of apoptosis in the tumor cells. Owing to their high abundance in plant seed oils and seaweeds, and being relatively non-cytotoxic, they might be potential candidates for the treatment of leukemia. Further investigations are required in order to develop a better understanding on the molecular action mechanisms underlying the anti-tumor effects of jacaric acid and cis-parinaric acid on leukemia cells before they could be developed as the therapeutic drugs for leukemia. / 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. / Liu, Wai Nam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 169-182). / Abstracts also in Chinese. / Abstract --- p.i / 摘要 --- p.v / Acknowledgements --- p.viii / List of Abbreviations --- p.ix / List of Figures and Tables --- p.xiii / Publications --- p.xvii / Chapter Chapter 1 --- General introduction / Chapter 1.1 --- Introduction to hematopoiesis and leukemia --- p.1 / Chapter 1.1.1 --- Introduction to hematopoiesis --- p.1 / Chapter 1.1.2 --- Introduction to leukemia --- p.7 / Chapter 1.1.2.1 --- Classification of leukemia --- p.7 / Chapter 1.1.2.2 --- Epidemiology of leukemia --- p.10 / Chapter 1.1.2.3 --- Conventional approaches to leukemia therapy --- p.12 / Chapter 1.1.2.4 --- Alternative approaches to leukemia therapy --- p.17 / Chapter 1.2 --- Introduction to conjugated fatty acids --- p.19 / Chapter 1.2.1 --- An overview of polyunsaturated fatty acids and conjugated fatty acids --- p.19 / Chapter 1.2.2 --- Chemical structures and physical properties of CLN and conjugated tetraenoic acids --- p.21 / Chapter 1.2.3 --- Natural occurrence of CLN and conjugated tetraenoic acids --- p.26 / Chapter 1.2.4 --- Synthesis of CLN and conjugated tetraenoic acids --- p.28 / Chapter 1.2.5 --- Metabolism of CLN --- p.30 / Chapter 1.2.6 --- Major biological and pharmacological activities of CLN and conjugated tetraenoic acids --- p.30 / Chapter 1.2.6.1 --- Anti-obese and hypolipidemic property --- p.31 / Chapter 1.2.6.2 --- Anti-carcinogenic property --- p.32 / Chapter 1.2.6.2.1 --- Anti-proliferative effect --- p.32 / Chapter 1.2.6.2.2 --- Apoptosis-inducing effect --- p.33 / Chapter 1.3 --- Aims and scopes of this thesis --- p.36 / Chapter Chapter 2 --- Materials and methods / Chapter 2.1 --- Materials --- p.39 / Chapter 2.1.1 --- Animals --- p.39 / Chapter 2.1.2 --- Cell lines --- p.39 / Chapter 2.1.3 --- Cell culture media and reagents --- p.40 / Chapter 2.1.4 --- Fatty acids --- p.44 / Chapter 2.1.5 --- Reagents and buffers for flow cytometry --- p.48 / Chapter 2.1.6 --- Reagents and buffers for Western blotting --- p.51 / Chapter 2.1.7 --- Cell Death Detection ELISA{U+1D3E}{U+1D38}{U+1D41}{U+1D40} kit --- p.60 / Chapter 2.2. --- Methods --- p.62 / Chapter 2.2.1 --- Culture of tumor cell lines --- p.62 / Chapter 2.2.2 --- Isolation and culture of murine normal cells --- p.63 / Chapter 2.2.3 --- Determination of cell proliferation by CyQUANT® NF cell proliferation assay --- p.65 / Chapter 2.2.4 --- Determination of cell viability --- p.66 / Chapter 2.2.5 --- Cytotoxicity test of CFA on normal cells --- p.67 / Chapter 2.2.6 --- In vivo tumorigenicity assay --- p.68 / Chapter 2.2.7 --- Analysis of cell cycle profile --- p.69 / Chapter 2.2.8 --- Measurement of DNA fragmentation by Cell Death Detection ELISA{U+1D3E}{U+1D38}{U+1D41}{U+1D40} kit --- p.70 / Chapter 2.2.9 --- Analysis of Annexin V-GFP/PI dual staining profile --- p.71 / Chapter 2.2.10 --- Determination of mitochondrial membrane potential by JC-1 staining --- p.72 / Chapter 2.2.11 --- Determination of intracellular reactive oxygen species generation --- p.72 / Chapter 2.2.12 --- Determination of mitochondrial mass --- p.73 / Chapter 2.2.13 --- Protein expression study --- p.74 / Chapter 2.2.14 --- Statistical analysis --- p.78 / Chapter Chapter 3 --- Studies on the anti-proliferative effects of jacaric acid and cis-parinaric acid on murine macrophage-like leukemia cells / Chapter 3.1 --- Introduction --- p.79 / Chapter 3.2 --- Results --- p.82 / Chapter 3.2.1 --- Anti-proliferative effects of CFA isomers on murine macrophage-like leukemia PU5-1.8 cells in vitro --- p.82 / Chapter 3.2.2 --- Kinetic and reversibility studies of the anti-proliferative effects of jacaric acid and cis-parinaric acid on PU5-1.8 cells --- p.92 / Chapter 3.2.3 --- Cytotoxic effects of jacaric acid and cis-parinaric acid on PU5-1.8 cells --- p.97 / Chapter 3.2.4 --- Cytotoxic effects of jacaric acid and cis-parinaric acid on murine normal cells in vitro --- p.99 / Chapter 3.2.5 --- Effect of jacaric acid on the in vivo tumorigenicity of PU5-1.8 cells --- p.102 / Chapter 3.3 --- Discussion --- p.104 / Chapter Chapter 4 --- Mechanistic studies on the anti-tumor effects of jacaric acid and cis-parinaric acid on murine macrophage-like leukemia cells / Chapter 4.1 --- Introduction --- p.111 / Chapter 4.2 --- Results --- p.117 / Chapter 4.2.1 --- Effects of jacaric acid and cis-parinaric acid on the cell cycle profile of murine macrophage-like leukemia PU5-1.8 cells --- p.117 / Chapter 4.2.2 --- Effects of jacaric acid and cis-parinaric acid on the expression of cell cycle regulatory proteins in murine macrophage-like leukemia PU5-1.8 cells --- p.121 / Chapter 4.2.3 --- Effects of jacaric acid and cis-parinaric acid on the generation of reactive oxygen species in murine macrophage-like leukemia PU5-1.8 cells --- p.124 / Chapter 4.2.4 --- Effects of antioxidants on the anti-proliferative effects of jacaric acid and cis-parinaric acid on the murine macrophage-like leukemia PU5-1.8 cells --- p.128 / Chapter 4.2.5 --- Effects of jacaric acid and cis-parinaric acid on the mitochondrial mass in murine macrophage-like leukemia PU5-1.8 cells --- p.131 / Chapter 4.2.6 --- Effects of jacaric acid and cis-parinaric acid on the induction of apoptosis in murine macrophage-like leukemia PU5-1.8 cells --- p.135 / Chapter 4.2.7 --- Effects of jacaric acid and cis-parinaric acid on the induction of phosphatidylserine externalization in murine macrophage-like leukemia PU5-1.8 cells --- p.139 / Chapter 4.2.8 --- Effects of jacaric acid and cis-parinaric acid on the mitochondrial membrane potential in murine macrophage-like leukemia PU5-1.8 cells --- p.144 / Chapter 4.2.9 --- Effects of jacaric acid and cis-parinaric acid on the expression of apoptosis-regulatory proteins in murine macrophage-like leukemia PU5-1.8 cells --- p.149 / Chapter 4.3 --- Discussion --- p.152 / Chapter Chapter 5 --- Conclusions and future perspectives / Chapter 5.1 --- Conclusions --- p.161 / Chapter 5.2 --- Future perspectives --- p.164 / References --- p.169

在世界範圍內，肝細胞癌(HCC)是其中一種惡性程度很高並且預後很差的疾病。和其他的癌症一樣，肝癌是一种基因疾病，基因異常的積累在肝癌的生成中扮演著重要的角色。近年來，第二代測序技術（NGS）的迅速發展顯現了前所未見的能力揭示癌癥基因組中分子的複雜性，這為癌癥的生物學，診斷和药物治療提供了一個嶄新的思路。 / 非酒精脂肪性肝炎（NASH）是一種與代謝有關的疾病，在發達國家地區例如美國，歐洲，日本和加拿大，這是其中一種越來越常見的HCC 的病因。在本論文的第一部份，三個NASH 相關的HCC 以及其配對的血DNA 進行了全基因組測序（WGS）。另外還有一個來源于這三個NASH 相關的HCC其中之一的細胞株也進行了全基因組測序。在全部樣品中，測序深度範圍介乎29.1X 到102.2X，序列覆蓋度均大於99%。結果顯示發現的新的單核苷酸變異（SNVs）數量介乎于6,898 至17,129，平均值是11,133。根據這些找到的SNV，隨機選出56 個體細胞SNV 進行Sanger 測序，其中92.9%可以被確認。基因突變譜顯示有頻繁的A:T>G:C 和C：G>A:T 體細胞突變，而C：G>T:A 則在CpG 位點頻繁出現。在眾多的非同義體細胞突變基因中，我們選擇了CTNNB1，PNLIP 和MLL2 這三個基因進行進一步研究，此三個基因都在多於一個病例中發現有突變。在額外的一組44 對NASH 相關HCC及50 對HBV 相關的HCC 的癌變組織和其臨近非腫瘤組織中，我們進一步對這三個基因和TP53 的編碼區域進行了測序，而TP53 是在HBV 相關HCC中被報導有高頻率突變的。在NASH 相關的HCC 中，這些基因都只在腫瘤組織中發現重複出現的錯義突變，在臨近的非腫瘤肝組織沒有發現有突變。在NASH 相關的HCC 中，CTNNB1 的突變率（36.4%）明顯高於在HBV相關的HCC 中的突變率（12.0%，P=0.007）。PNLIP 和MLL2 的突變只在NASH相關的HCC 中發現，其突變率分別為12.1%和7.1%，而在HBV 相關的HCC中，則沒有發現突變。然而，TP53 的突變率在NASH 相關的HCC 及HBV相關的HCC 中差別不明顯（P>0.1）。在功能性研究的實驗中，我们发现在HKCI-10（有PNLIP 突變D396N）細胞株中，PNILP 的活性比在正常肝細胞L02 細胞株（野生型PNLIP）中要低。在永生性肝細胞L02 細胞株中，CTNNB1的突變引起了TOPFLASH 活性的提高以及增加了細胞群落形成的能力。HKCI-10 是一條我們實驗室建立的NASH 相關的肝細胞癌細胞株，在HKCI-10細胞株中，抑制CTNNB1 表達引起了細胞生長和增殖的減少。另外，在DEN誘導肝癌的有代謝失衡的db/db 轉基因鼠中，發現了一個CTNNB1 的突變T41A。據報導，CTNNB1 發生的致癌突變會引起蛋白的穩定並且因此激活經典的Wnt/β-catenin 信號通路，從而引致特定基因的轉錄。對於CTNNB1中最常見的突變S45P(在發現的CTNNB1 突變中占31.3%)，我們做了ChIP-array 實驗，結果顯示，在HKCI-10（CTNNB1 有S45P 突變）中，CTNNB1比在Hep3B 中（野生型CTNNB1）有著更緊密的啟動子結合能力（P<0.001）。Gene ontology 分析結果表明，被S45P 富集的生物過程涉及有RNA 代謝調節，轉錄因子活性和凋亡。MYC，E2F1 和ZFX 被ChIP-PCR 證實是與CTNNB1突變子S45P 有著更緊密結合能力的轉錄因子。 / 在本論文的第二部份，爲了進一步闡明致癌性的CTNNB1 突變S45P在HCC 中的角色，我們研究了一個此前未在HCC 報導過的基因ZFX。ZFX是一個在脊椎動物中高度保守，屬於Zfy 家族的zinc finger 蛋白。有報導指出ZFX 對於胚胎和造血幹細胞的自我更新有著重要的作用。另外亦有文獻報導ZFX 在一系列人類癌癥病例中有過度表達，例如食道癌，胃癌，前列腺癌和神經膠質瘤，並且顯現出致癌基因的特性。在本研究中，qRT-PCR結果提示ZFX 在HCC 腫瘤中的表達明顯高於正常肝組織。ZFX 的表達在51.8%的HCC 腫瘤中明顯高於其配對的鄰近非腫瘤肝組織。功能性研究表明，在MTT 實驗中，細胞的生存力在ZFX 缺失的穩定克隆中明顯減弱（P<0.0001）。在細胞群落形成實驗中，ZFX 缺失的穩定克隆顯示出明顯減弱的群落生長能力（P<0.0001）。在單細胞克隆生成實驗中，ZFX 缺失的HCC穩定克隆展示出數量更少，體積更小的細胞群落。另外，ZFX 基因抑制或者cisplatin 單獨處理均顯示細胞生存力的抑制，其抑制效率分別是24.0%和30.9%。當ZFX 基因抑制合併cisplatin 處理時，細胞生存力的抑制效率顯著地提高至65.2%，這個結果提示ZFX 基因抑制和cisplatin 處理兩者有協同增效作用（P<0.0001）。ZFX 基因的缺失會引起兩個為人熟知的胚胎幹細胞（ESCs）標誌物SOX-2 和NANOG 表達的明顯降低。 / 綜上所述，通過進行全基因測序，本論文的研究結果為NASH 相關的HCC 分子層面上的異常提供了一個高解析度的視覺角度。在NASH 相關的HCC 中，一些可能對於肝細胞癌變有重要作用並且重複出現突變的基因被確定，例如CTNNB1 和PNLIP。CTNNB1 的突變體S45P 的其中一個下游目標基因ZFX，在HCC 中被證實有幹細胞和腫瘤啟動細胞特性。闡明在HCC發展過程中的分子改變以及機制，對於為肝癌病人探索新的治療手段有著重要意義。 / Hepatocellular Carcinoma (HCC) is one of the most malignant diseases worldwide with poor prognosis. Like other human cancers, HCC is a genetic disease, where accumulation of genetic aberration plays important role in the liver carcinogenesis. The rapid advances in Next Generation Sequencing (NGS) technology in recent years have allowed unprecedented ability to unravel the molecular complexity of the cancer genome, providing new insights into the cancer biology, diagnosis and therapeutic drug development. / Non-alcoholic steatohepatitis (NASH), which is related to metabolic disorder, is an increasing common etiological factor of HCC, especially in developed countries such as United States, Europe, Japan and Canada. In first part of this thesis, Whole Genome Sequencing (WGS) was performed on three NASH-associated HCCs and their matched lymphocytic DNA. A cell line developed from one of the three NASH-associated HCCs was also subjected to WGS. The sequencing depth ranged from 29.1X to 102.2X with the coverage >99% shown in all samples. Novel SNVs identified ranged from 6,898 to 17,129 with an average of 11,133. Based on the SNVs found, the validation rate was 92.9% in 56 randomly selected somatic SNVs by Sanger sequencing. Mutational spectrum showed frequent somatic substitution of A:T>G:C and C:G>A:T while C:G>T:A transition exhibited a predominant somatic mutation rate in CpG sites. Among the non-synonymous somatic mutated genes, we selected CTNNB1, PNLIP and MLL2 which were mutated in more than one tumor for further study. In additional cohort of 44 NASH-associated and 50 HBV-associated HCC tumors and adjacent non-tumoral tissues, further sequencing all the coding regions of these three genes and TP53, which has been reported to be highly mutated in HBV-associated HCCs, were carried out. In NASH-associated HCCs, all genes harboured recurrent missense mutations exclusive in tumor but none in adjacent ,non-tumoral liver. The prevalence of CTNNB1 mutations was significantly higher in NASH-associated HCCs (36.4%) when compared to HBV-associated HCCs (12.0%, P=0.007). Mutations of PNLIP and MLL2 were detected only in NASH-associated HCCs with rates of 12.1% and 7.1%, respectively, but none in HBV-associated HCCs. The mutation rate of TP53, however, did not differ much between NASH-associated and HBV-associated HCCs (P>0.1). In functional study, for PNLIP, a loss-of-function in PNLIP activity was found in HKCI-10 harbouring D396N mutation as compared to normal liver cell, L02 with wild-type PNLIP. We demonstrated that CTNNB1 mutants conferred elevated TOPFLASH activity and enhanced colony growth in an immortalized hepatocyte cell line L02. Knockdown of CTNNB1 in HKCI-10, which is a NASH-associated HCC in-house cell line, resulted in inhibition of cell growth and proliferation. Also, a CTNNB1 mutation (T41A) was found in DEN-induced liver cancer of db/db transgenic mouse with metabolic disorder. Since oncogenic mutations of CTNNB1 were reported to be contributed to the stabilization of the protein and hence activate the canonical Wnt/β-catenin signaling pathway, inducing transcription of specific gene sets. We performed ChIP-array focusing on the most common CTNNB1 S45P mutation (accounted for 31.3% of all detected CTNNB1 mutants) in NASH-associated HCCs, the result showed more intense promoter binding affinities in HKCI-10 with CTNNB1 S45P mutation than Hep3B with wild-type CTNNB1 (P<0.001). Gene ontology analysis revealed that S45P mutant enriched the process including RNA metabolic regulation, transcription factor activities and apoptosis. Furthermore, we found that CTNNB1 S45P mutant showed more profound binding affinity to the promoter regions of transcription factors MYC, E2F1 and ZFX by ChIP-PCR. / In the second part of the thesis, we aimed to further understand the role of oncogenic CTNNB1 S45P mutant in HCC. Zinc finger protein X-linked (ZFX) gene which is previously undescribed in HCC was studied. ZFX is a zinc finger protein of Zfy family that is highly conserved among vertebrates. It has been reported that ZFX is required for self-renewal of embryonic and hematopoietic stem cells. Also, ZFX is suggested to be overexpressed in a number of human cancers such as esophageal carcinoma, gastric cancer, prostate cancer and glioma, conferring oncogenic characteristics. In this study, qRT-PCR analysis showed a significant higher ZFX expression in HCC tumors compared to normal livers. 51.8% of HCC tumors showed significant up-regulations of ZFX when compared to paired adjacent non-tumoral livers. Functional studies showed significant reduction in in-vitro cell proliferation in HCC by MTT assay (P<0.0001) and colony formation ability by colony formation assay (P<0.0001) in ZFX-deficient stable clones. In single-cell clonogenic assay, ZFX-depleted HCC exhibited fewer and smaller colonies. In addition, while ZFX knockdown or cisplatin treatment alone showed an inhibitory effect on cell viability by 24.0% and 30.9%, respectively, the reduction efficiency of cell viability increased dramatically to 65.2% when combine ZFX-knockdown and cisplatin treatment, indicating a synergistic effect between them (P<0.0001). Also, significant reduced expressions of SOX-2 and NANOG, both well-known embryonic stem cells (ESCs) markers, were observed as a result of ZFX depletion. / In summary, findings from this thesis provided high-resolution insight into the molecular aberrations in NASH-associated HCCs by performing WGS. Recurrent mutated genes which may be of great importance in hepatocellular carcinogenesis induced by NASH were identified, such as CTNNB1 and PNLIP. One of the S45P CTNNB1 downstream targets ZFX was demonstrated to confer stemness and tumor-initiating cells (TICs) characteristics in HCC. The understanding of molecular changes and mechanisms underlying HCC development will thus facilitate the exploration of new therapeutic options in patients with this deadly disease. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chen, Jiawei. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 166-190). / Abstracts also in Chinese.

Omega-3 fatty acids are increasingly recognised as playing an important role in human brain development and mental health. The polyunsaturated fatty acids (PUFAs) include omega-3 and omega-6 fats which are essential fatty acids (EFAs), consumed via the diet. Omega-3 fatty acids are particularly abundant in fish oils. The omega-3 fatty acids are being focused on for their role in depression, the main types being docosahexaenoic acid (DHA), which is abundant in neural tissue, and also eicosapentaenoic acid (EPA) which is biologically very active. There is an emerging literature in relation to omega-3 fatty acid blood levels in depression and the effects of treatment with omega-3. Strong epidemiological evidence has also been published indicating an association between a population's fish intake and depression rates. A specific research focus on omega-3 as a treatment for depression in the perinatal period is also starting to emerge. The importance of this particular area is enhanced by the knowledge that omega-3 depletion occurs during the perinatal period due to fetal diversion for neurodevelopment. In view of the lay public promotion of omega-3 and its appeal to women as a 'natural therapy', there is a need to scientifically evaluate its effectiveness to treat depression in the perinatal period. It is also important to investigate omega-3 as an alternative to antidepressants given the ongoing uncertainties regarding their safety in pregnancy. In this thesis a literature review presents current research relating to this field. This is followed by a description of the methodology and results for the two trials conducted. The results of the double-blind randomised placebo controlled trial of omega-3 as a treatment for depression in the perinatal period were essentially negative. However this result is limited by the small sample size in the study and therefore it may be unwise to interpret the result as conclusive. The case-control study confirmed the hypothesis that omega-3 levels were more depleted in depressed women compared to non-depressed women. A discussion of the results and trial limitations then follows in the thesis. It is concluded that further larger studies are warranted in this area.

Cholesterol and fatty acyl-coenzymeA thioesters are signalling molecules with role in regulation of genes involved in lipid and glucose transport and metabolism. The studies described herein focused on three proteins that bind lipids and have different cellular functions: steroidogenic acute regulatory protein (StAR), hepatocyte nuclear factor-4a (HNF-4a) and acyl-CoA binding protein (ACBP). First, StAR mediates delivery of cholesterol to inner mitochondrial membrane in steroidogenesis by a poorly understood mechanism. In our studies, fluorescent NBD-cholesterol binding assays demonstrate that StAR binds cholesterol at two binding sites with 32 nM Kds and circular dichroism spectra show that cholesterol binding results in changes of StAR secondary structure. Fluorescent sterol exchange assays between donor and acceptor mitochondrial membranes indicate that StAR significantly increased the formation of rapidly transferable cholesterol domains. Second, HNF-4a, a nuclear receptor, had been shown to bind fatty acyl-CoAs as natural ligands with apparent low affinities obtained with radiolabeled ligand binding assays. Our fluorescence spectroscopy studies demonstrate that HNF-4a ligand binding domain (HNF-4aLBD) binds acyl-CoAs at a single binding site with Kds of 1.6-4 nM. Fluorescence resonance energy transfer (FRET) between HNF-4aLBD tryptophan residues and cis-parinaroyl-CoA yielded an intermolecular distance of 42 Â thus pointing to direct molecular interaction. Third, although ACBP has been detected in the nucleus, it is not known whether ACBP may directly and/or functionally interact with a nuclear acyl-CoA binding protein such as HNF-4a to regulate transcription. Our present studies in vitro and in intact cultured cells, including circular dichroism of HNF-4a in the presence of ACBP, coimmunoprecipitation of HNF-4a/ACBP complexes, ACBP and HNF-4a colocalization in nuclei of cells by confocal microscopy demonstrate a physical association of ACBP and HNF-4a. FRET microscopy data indicated an intermolecular distance of 53 Â between ACBP and HNF-4a in rat hepatoma cells. Functional assays (transactivation of an HNF4a-dependent reporter gene) showed significant increase in the presence of ACBP in two different cell lines. Expression of ACBP anti-sense RNA decreased HNF-4a-mediated transactivation, pointing to a role of ACBP in co-regulating HNF-4a-dependent transcription.

Fatty acids are important regulators in the control of mammalian energy homeostasis. They are ingested in the diet but a significant amount are also endogenously produced by de novo lipogenesis. Fatty acid elongation beyond 16 carbons (palmitic acid) can occur to generate very long chain fatty acids (VLCFA), a process that is initiated by the rate-limiting condensation reaction. To date, six mammalian enzymes responsible for this reaction, ELOVL1-6 (Elongation of very long chain fatty acid), have been characterized. All of them exert substrate specificity and tissue-specific gene expression. In this thesis, factors that regulate fatty acid metabolism and, in particular, fatty acid synthesis and elongation will be presented. The enclosed papers discuss issues as to how Elovl3 is regulated in liver and in different adipose depots and what effects ablation of this enzyme causes to lipid homeostasis. Hepatic Elovl3 gene expression followed a circadian rhythm, present exclusively in sexually mature male mice. In contrast to the expression of several other lipogenic genes, Elovl3 gene expression was not affected by fasting or refeeding. Instead, the gene expression was influenced by steroid hormones such as glucocorticoids and sex hormones. Interestingly, despite reduced levels of leptin, Elovl3-ablated mice were shown to be resistant to diet induced weight gain, which seemed to be due to a decreased ratio between energy intake and energy expenditure. This phenotype was more pronounced in female mice. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript.