Lau Yee Lam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 147-157). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.iv / Abbreviations --- p.v / List of Figures --- p.viii / List of Tables --- p.xi / Contents --- p.xii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Hepatocellular carcinoma (HCC) --- p.1 / Chapter 1.1.1 --- Background of hepatocellular carcinoma (HCC) --- p.1 / Chapter 1.1.2 --- Etiology of HCC --- p.2 / Chapter 1.1.3 --- Relationship between HCC and HBV --- p.3 / Chapter 1.1.4 --- Differential gene expression under induction of HBx protein by microarray analysis --- p.5 / Chapter 1.1.5 --- Confirmation of candidate genes --- p.6 / Chapter 1.2 --- Ras-Oncogene --- p.8 / Chapter 1.2.1 --- Ras superfamily --- p.8 / Chapter 1.2.1.1 --- Rho family --- p.9 / Chapter 1.2.1.2 --- Rab family --- p.10 / Chapter 1.2.2 --- Functional mechanism of small GTPase --- p.11 / Chapter 1.2.3 --- Possible functions of Rho and Rab family members --- p.14 / Chapter 1.3 --- RhoC --- p.16 / Chapter 1.3.1 --- The genomic and protein structures of RhoC --- p.16 / Chapter 1.3.2 --- Relationship between RhoC and tumours --- p.19 / Chapter 1.4 --- Rabl4 --- p.20 / Chapter 1.4.1 --- The genomic and protein structures of Rabl4 --- p.20 / Chapter 1.4.2 --- Relationship between Rabl4 and tumours --- p.23 / Chapter 1.5 --- Aims of study --- p.23 / Chapter Chapter 2 --- Materials and Methods / Chapter 2.1 --- Materials --- p.25 / Chapter 2.1.1 --- Cell lines --- p.25 / Chapter 2.1.2 --- Cell culture reagents --- p.26 / Chapter 2.1.3 --- Reagents for total RNA isolation --- p.29 / Chapter 2.1.4 --- Reagents for reverse transcription polymerase chain reaction (RT-PCR) --- p.30 / Chapter 2.1.5 --- Reagents and buffers for Western blot analysis --- p.31 / Chapter 2.1.6 --- Vectors for cloning --- p.39 / Chapter 2.1.7 --- Reagents for polymerase chain reaction (PCR) --- p.39 / Chapter 2.1.8 --- Restriction digestion reagents --- p.42 / Chapter 2.1.9 --- Reagents for agarose gel electrophoresis --- p.42 / Chapter 2.1.10 --- Ligation reagents --- p.44 / Chapter 2.1.11 --- Bacterial culture medium --- p.44 / Chapter 2.1.12 --- Dyes and reagents for fluorescent microscope --- p.46 / Chapter 2.1.13 --- Reagents for flow cytometry --- p.48 / Chapter 2.1.14 --- Detection of apoptosis --- p.48 / Chapter 2.2 --- Methods --- p.50 / Chapter 2.2.1 --- Identification of gene expression of candidate genes in HCC --- p.50 / Chapter 2.2.1.1 --- cDNA preparation --- p.50 / Chapter (1) --- Cell culture of HepG2 and WRL-68 cell lines --- p.50 / Chapter (2) --- Total RNA isolation --- p.50 / Chapter (3) --- First-strand cDNA synthesis --- p.51 / Chapter 2.2.1.2 --- RT-PCR of candidate genes --- p.52 / Chapter 2.2.1.3 --- Western blotting --- p.53 / Chapter (1) --- Cell culture --- p.53 / Chapter (2) --- Protein extraction --- p.53 / Chapter (3) --- Quantification of proteins --- p.53 / Chapter (4) --- Detection of RhoC and Rabl4 protein by western blot analysis --- p.54 / Chapter (5) --- Western blotting luminol detection --- p.56 / Chapter 2.2.2 --- Cloning protocol --- p.57 / Chapter 2.2.2.1 --- Amplification of RhoC and Rabl4 genes --- p.57 / Chapter 2.2.2.2 --- Purification of PCR product --- p.58 / Chapter 2.2.2.3 --- Restriction enzymes digestion --- p.53 / Chapter 2.2.2.4 --- Insert/vector ligation --- p.59 / Chapter 2.2.2.5 --- Preparation of chemically competent bacterial cells (E. coli strain DH5a) --- p.60 / Chapter 2.2.2.6 --- Transformation of ligation product into chemically competent bacterial cells --- p.61 / Chapter 2.2.2.7 --- Small-scale preparation of bacterial plasmid DNA --- p.61 / Chapter 2.2.2.8 --- Screening for recombinant clones --- p.62 / Chapter 2.2.2.9 --- DNA sequencing of cloned plasmid DNA --- p.63 / Chapter 2.2.2.10 --- Midi-scale preparation of recombinant plasmid DNA --- p.64 / Chapter 2.2.3 --- Visualization of the subcellular localization patterns --- p.66 / Chapter 2.2.3.1 --- Cell culture of AML12 and HepG2 cell lines --- p.66 / Chapter 2.2.3.2 --- Transfection of GFP fusion constructs into cells --- p.66 / Chapter 2.2.3.3 --- DAPI staining --- p.67 / Chapter 2.2.3.4 --- ER-Tracker´ёØ Blue-White DPX staining --- p.68 / Chapter 2.2.3.5 --- Subcellular localization study using Epi-fluorescence microscopy --- p.68 / Chapter 2.2.4 --- Analysis of cell cycle --- p.69 / Chapter 2.2.4.1 --- Transfection of GFP vectors / GFP-tagged proteins into cells --- p.69 / Chapter 2.2.4.2 --- Analysis of cell cycle by flow cytometry --- p.69 / Chapter 2.2.5 --- Detection of apoptosis --- p.70 / Chapter 2.2.5.1 --- Transfection --- p.70 / Chapter 2.2.5.2 --- Detection of DNA fragmentation --- p.70 / Chapter 2.2.6 --- Reorganization of Actin cytoskeleton by RhoC --- p.71 / Chapter 2.2.6.1 --- Transfection of GFP vectors/GFP-tagged proteins into cells --- p.71 / Chapter 2.2.6.2 --- Rhodamine phalloidin (RP) staining --- p.71 / Chapter 2.2.6.3 --- Epi-fluorescence microscopy --- p.72 / Chapter 2.2.7 --- Analysis of cell invasion under induction of RhoC --- p.72 / Chapter 2.2.7.1 --- "Sub-cloning of human RhoC gene into a mammalian expression vector, pHM6" --- p.72 / Chapter 2.2.7.2 --- Transfection of pHM6-RhoC --- p.73 / Chapter 2.2.7.3 --- Cell invasion assay --- p.73 / Chapter 2.2.8 --- Analysis of downstream effectors in RhoC-mediated pathway --- p.75 / Chapter 2.2.8.1 --- RT-PCR --- p.75 / Chapter 2.2.8.2 --- Western blotting --- p.75 / Chapter 2.2.9 --- Analysis of role of Rabl4 in membrane trafficking --- p.76 / Chapter 2.2.9.1 --- Cloning and transfection --- p.76 / Chapter 2.2.9.2 --- Alexa 594 transferrin conjugate staining --- p.76 / Chapter 2.2.9.3 --- Epi-fluorescence microscopy --- p.77 / Chapter 2.2.10 --- Statistics --- p.77 / Chapter Chapter 3 --- Results / Chapter 3.1 --- Expression of RhoC and Rabl4 in hepatoma cells --- p.78 / Chapter 3.1.1 --- RT-PCR --- p.78 / Chapter 3.1.2 --- Western blotting --- p.81 / Chapter 3.2 --- Subcellular localization of RhoC and Rab 14 --- p.85 / Chapter 3.3 --- Characterization of RhoC --- p.93 / Chapter 3.3.1 --- Cell cycle analysis --- p.93 / Chapter 3.3.2 --- Apoptosis --- p.95 / Chapter 3.3.3 --- Actin cytoskeleton reorganization --- p.97 / Chapter 3.3.4 --- Cell invasion ability --- p.99 / Chapter 3.3.5 --- Downstream effectors of RhoC in cytoskeletal reorganization --- p.102 / Chapter 3.4 --- Characterization of Rabl4 --- p.107 / Chapter 3.4.1 --- Cell cycle analysis --- p.107 / Chapter 3.4.2 --- Apoptosis --- p.109 / Chapter 3.4.3 --- Roles in intracellular transportation --- p.111 / Chapter Chapter 4 --- Discussion / Chapter 4.1 --- Strong expression of RhoC and Rabl4 in hepatoma cells --- p.117 / Chapter 4.2 --- Subcellular localization of RhoC and Rabl4 --- p.119 / Chapter 4.3 --- The effects of RhoC in normal liver cells --- p.122 / Chapter 4.3.1 --- Cell cycle progression by RhoC through regulating of G1 to S phase transition --- p.122 / Chapter 4.3.2 --- RhoC shows no apoptotic effect in normal liver cell systems --- p.123 / Chapter 4.3.3 --- Formation of actin filaments and stress fibers --- p.124 / Chapter 4.3.4 --- Induction of cell invasion in RhoC-expressing cells --- p.125 / Chapter 4.3.5 --- Downstream effectors in signaling pathway of RhoC in actin filment reorganization and cell invasion --- p.126 / Chapter 4.4 --- The effects of Rabl4 in normal liver cells --- p.132 / Chapter 4.4.1 --- Cell proliferation effects of Rabl4 by increasing percentage of cells in S phase for DNA synthesis --- p.132 / Chapter 4.4.2 --- Rabl4 has no apoptotic effects --- p.133 / Chapter 4.4.3 --- Roles of Rabl4 in vesicular transport --- p.134 / Chapter 4.5 --- Conclusion --- p.138 / Chapter 4.6 --- Future prospects --- p.140 / Appendix --- p.143 / References --- p.147

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Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

For ras gene mutation analysis in the rainbow trout (Oncorhynchus mykiss) model system, a partial trout ras sequence was identified using the polymerase chain reaction (PCR). Two synthetic oligonucleotides based on rat K-ras gene sequence were used as primers for the PCR procedure. A 90 base pair (bp) sequence, referred to as the trout K-ras, was amplified from trout genomic DNA and cDNA. Cloned 90 by PCR products from several normal liver tissues were sequenced resulting in the same sequence. Large-sized PCR products, 111 and 237 bp, were also cloned and sequenced indicating that these fragments included the 90 by sequence information expressed in mRNA. This 5'-terminal partial trout K-ras nucleotide sequence was 88% homologous to that of the goldfish ras gene, and less homologous to those of mammalian ras genes. Based on the partial sequence information of two trout ras genes, K-ras and H-ras, DNA from trout tumors induced by chemical carcinogens, aflatoxin B1 (AFB1) and N-methyl-N'-nitro-N-nitrosoguanidene (MNNG), were analyzed for the presence of point mutations. Using the PCR and oligonucleotide hybridization methods, a high proportion (10/14) of the AFB1-initiated liver tumor DNA indicated evidence for ras point mutations. Of the 10 mutant ras genotypes, seven were probed as G to T transversions at the second position of codon 12, two were G to T transversions at the second position of codon 13, and one was a G to A transition at the first position of codon 12. Nucleotide sequence analysis of cloned PCR products from four of these tumor DNAs provided definitive mutation evidence in each case, which seemed to occur in only a fraction of the neoplastic cells. However, no mutations were detected in exon 1 of the trout K-ras gene, nor in DNA from trout normal livers. Results indicated that the hepatocarcinogen AFB1 induced similar ras gene mutations in trout as in rat liver tumors. By comparison, the mutation specificity of MNNG in trout liver tumors was for G to A transitions, but no ras mutations were detected in trout kidney tumors. This investigation was the initial study of experimentally induced ras gene point mutations in a lower vertebrate fish model. / Graduation date: 1991

Competition among cells has long been recognized as an important part of the evolutionary process of tissue leading up to the development of cancer. However, the role of cellular cooperation in cancer has been largely ignored. In this work, we investigated the role of cooperation in early tumor progression using a mathematical and agent-based modeling approach. We hoped to learn whether cooperation between cells in spatially organized tissue has a significant role in hastening tumor development, and to uncover general principles governing such cooperation. We focused on the early stages of tumor development given the critical importance of this time period and since we hypothesized that cooperation will have its greatest influence during these early phases. In our model, stem cells were placed into an array of 50 x 20 cell patches, with each patch carrying a maximum of 64 cells. The stem cells' potential to replicate or leave the stem cell compartment through apoptosis or differentiation were governed by modified versions of the Lotka-Volterra equation of ecology. The cells could also acquire mutations in two oncogenes and three tumor suppressor genes. We explored two different cooperation strategies, one in which a cell could acquire the ability to send a cooperative signal that improved the fitness of its immediate neighbors, and one in which a cell could acquire the ability to take advantage of a cooperative signal already in the environment. Cooperation could be acquired through mutation or assigned in advance. We ran simulations of the model in MATLAB. We found that cooperation is a very robust property. Once a small number of cooperative cells is introduced into a cell population, they rapidly proliferate to the point of being the major constituent of the cell population. Cooperation leads to an increased growth rate of the aggregate cell population, with the growth rate rising in parallel with the cooperative cell fraction. Interestingly, cooperation does not seem to have an effect on cell heterogeneity, counter to what we initially suspected. We also found that cooperative cells have a wider spatial influence than non-cooperating cells. The cooperative cells or their descendant are, on average, present in more patches than corresponding non-cooperative cells at each point in time. Further analysis showed that cooperation is particularly important in the very early pre-tumor stage, when tissue is morphologically and histologically normal, and during times of extensive cell death, such as when tissue experiences necrosis, repeated bouts of inflammation, or cancer treatment. In conclusion, we found that cooperation may play an important role in early tumor progression that is complementary to the competitive interactions among cells that are driven by mutations in tumor suppressors and oncogenes. Cooperation may also be a critical force during later stages of tumor progression when there is significant cell turnover. Our results have implications for cancer prevention and tumor therapeutic strategies.

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 103-114). Also available in print.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 112-132).

Precancerous lesions from a variety of human tissues display markers of DNA damage suggesting that genetic instability occurs early during the process of carcinogenesis. Consistent with this, several oncogenes can activate ATM and other components of the DNA damage response pathway when expressed in cultured cells. Here we demonstrate that preneoplastic epithelial tissues from four different transgenic mouse models expressing the oncogenes c-myc, SV40 T antigen, human papilloma virus (HPV) E7, or E2F3a display [gamma]-H2AX foci and other markers of DNA damage. Moreover, transgenic expression of these oncogenes leads to increased levels of damaged DNA as measured by the comet assay. In at least the Myc transgenic model, the formation of [gamma]-H2AX foci is dependent on functional ATM. Inactivation of Atm also impairs p53 activation and reduces the level of apoptosis observed in transgenic tissue overexpressing Myc. This correlates with accelerated tumor development in Myc transgenic mice lacking ATM. To understand the mechanism by which oncogenes induce DNA damage, we employed an adenoviral overexpression system. Under conditions in which Myc or E2F3a induced replication is inhibited, we see a reduction in the DNA damage induced by these oncogenes both by comet assay and levels of [gamma]-H2AX. Moreover, Myc and E2F3a induced increased levels of the Cdt1 protein, a replication origin- licensing factor implicated in aberrant DNA replication. Taken together, these findings suggest that deregulated oncogenes induce unscheduled DNA replication leading to DNA damage and activation of the ATM DNA damage response pathway, which is important for the activation of p53, induction of apoptosis and the suppression of tumorigenesis. / text

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences