Thesis (PhD (Pathology. Medical Virology))--Stellenbosch University, 2006. / Host susceptibility to human immunodeficiency virus-1 (HIV-1) infection and disease progression to acquired immunodeficiency syndrome (AIDS) varies widely amongst individuals. This observation led to the identification of host genetic factors playing a vital role in HIV-1 pathogenesis. Previous studies mainly focusing on Caucasian-based populations have indicated possible associations between genetic variants and host susceptibility to HIV-1/AIDS. The limited studies performed on African-based populations have emphasised the need for extensive investigation of both previously reported and particularly novel genetic variants within the older and genetically diverse Sub-Saharan African populations. In this study, the case-control samples were represented by African individuals of Xhosa descent, all residing in the Western Cape Province of South Africa. This included 257 HIV-1 seropositive patients and 110 population-matched HIV-1 seronegative controls. Mutational screening was performed in a subset of individuals for the entire coding regions of the CC chemokine receptor 5 (CCR5) and CC chemokine receptor 2 (CCR2) genes, and the 3’ untranslated region of the CXC chemokine ligand (CXCL12) gene, as previously reported (Petersen, 2002). Further analysis of these genes in a larger study sample involved the genotyping of previously identified mutations and single nucleotide polymorphisms (SNPs), which forms part of the present study. In addition, mutational screening was performed for the entire coding region of the CXC chemokine receptor 4 (CXCR4) gene, partial coding region of the mannose binding lectin (MBL) gene, and the promoter regions of interleukin 4 (IL4), interleukin 10 (IL10) and the solute carrier 11A1 (SLC11A1) genes. This was followed by genotyping of SNPs occurring in CCR5, CCR2, CXCL12, MBL, IL4, IL10, CX3C chemokine receptor 1 (CX3CR1), CC chemokine ligand 5 (CCL5) and tumour necrosis factor alpha (TNFα) genes. Significant associations were observed with HIV-1 susceptibility in the Xhosa population of South Africa. These included the CCR5-2733A>G, CX3CR1V249I, IL10-819C>T and IL10-592C>A SNPs being associated with a reduced risk for HIV-1 infection, while the CCR5-2135C>T and SDF1-3’G>A (CXCL12-3’G>A) SNPs were associated with increased susceptibility to HIV-1 infection. Furthermore, certain haplotypes for IL4 and IL10 showed association with reduced risk for HIV-1 infection. This included the identification of a novel IL4 haplotype restricted to the HIV-1 seronegative control group. This study emphasises the importance of considering genetic diversity across all populations, as certain HIV-1/AIDS associations appear to be restricted to specific ethnic groups. These findings have also provided an understanding for further elucidating the functional roles of genetic variants in determining HIV-1/AIDS susceptibility. Ultimately, such genetic association studies will contribute to establishing HIV-1/AIDS risk profiles for African-based populations from pandemic-stricken Sub-Saharan Africa.

published_or_final_version / Pathology / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Pathology / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Pathology / Doctoral / Doctor of Philosophy

published_or_final_version / Surgery / Master / Master of Philosophy

published_or_final_version / Pathology / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Pathology / Master / Master of Philosophy

published_or_final_version / Surgery / Doctoral / Doctor of Philosophy

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.