Lee, Kwan Yeung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 103-113). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.v / Table of Content --- p.vi / List of Figures --- p.xi / List of Tables --- p.xiii / List of Abbreviations --- p.xiv / List of papers published during the study --- p.xvi / Chapter Chapter 1 --- Introduction and Aim of Study --- p.1 / Chapter 1.1 --- General Introduction --- p.1 / Chapter 1.2 --- Project objective and potential significances --- p.5 / Chapter Chapter 2 --- Literatures Review --- p.6 / Chapter 2.1 --- Cancer genetics and Tumor suppressor genes --- p.6 / Chapter 2.2 --- Epigenetic --- p.7 / Chapter 2.2.1 --- DNA methylation and promoter CpG island --- p.8 / Chapter 2.2.2 --- Establishment and maintenance of DNA methylation --- p.9 / Chapter 2.2.3 --- Transcriptional silencing by DNA hypermethylation --- p.9 / Chapter 2.3 --- Cancer epigenetic --- p.11 / Chapter 2.3.1 --- Hypomethylation of the cancer genome --- p.12 / Chapter 2.3.2 --- Hypermethylation in cancers --- p.12 / Chapter 2.3.3 --- Clinical relevance of cancer epigenetic --- p.13 / Chapter 2.4 --- Nasopharyngeal carcinoma --- p.14 / Chapter 2.4.1 --- NPC genetic and epigenetic --- p.15 / Chapter 2.5 --- 12p as a putative tumor suppressor locus --- p.16 / Chapter 2.5.1 --- Hematological malignancies associated with 12p loss --- p.17 / Chapter 2.5.2 --- Prostate cancer associated with 12p loss --- p.20 / Chapter 2.5.3 --- Lung cancer associated with 12p loss --- p.22 / Chapter 2.5.4 --- 12p deletion in other cancers --- p.23 / Chapter 2.6 --- 16q as a tumor suppressor locus --- p.24 / Chapter 2.6.1 --- Breast cancer and 16q --- p.25 / Chapter 2.6.2 --- Loss of 16q and prostate cancer --- p.26 / Chapter 2.6.3 --- Loss of 16q and hepatocellular carcinoma --- p.28 / Chapter 2.6.4 --- 16q deletion associated with other cancers --- p.29 / Chapter Chapter 3 --- Materials and Methods --- p.30 / Chapter 3.1 --- Cell lines and tissue samples --- p.30 / Chapter 3.1.1 --- Cell lines --- p.30 / Chapter 3.1.2 --- Maintenance of cell lines --- p.31 / Chapter 3.1.3 --- Drugs treatment of cell lines --- p.31 / Chapter 3.1.4 --- Normal tissues --- p.32 / Chapter 3.1.5 --- Total RNA extraction --- p.32 / Chapter 3.1.6 --- Genomic DNA extraction --- p.32 / Chapter 3.2 --- General techniques --- p.33 / Chapter 3.2.2 --- TA cloning and blunt end cloning of PCR product --- p.33 / Chapter 3.2.3 --- Transformation of cloning products to E. coli competent cells --- p.34 / Chapter 3.2.4 --- Preparation of plasmid DNA --- p.34 / Chapter 3.2.4.1 --- Mini-prep plasmid DNA extraction --- p.34 / Chapter 3.2.4.2 --- Midi-prep of plasmid DNA --- p.35 / Chapter 3.2.5 --- Measurement of DNA or RNA concentrations --- p.36 / Chapter 3.2.6 --- DNA sequencing of plasmid DNA and PCR products --- p.36 / Chapter 3.3 --- Preparation of reagents and medium --- p.37 / Chapter 3.4 --- Semi-quantitative Reverse-Transcription (RT) PCR expression analysis --- p.38 / Chapter 3.4.1 --- Reverse transcription reaction --- p.38 / Chapter 3.4.2 --- Semi-quantitative RT-PCR --- p.39 / Chapter 3.4.2.1 --- Primers design --- p.39 / Chapter 3.4.2.2 --- PCR reaction --- p.39 / Chapter 3.5 --- Methylation analysis of candidate genes --- p.40 / Chapter 3.5.1 --- Bisulfite treatment of genomic DNA --- p.41 / Chapter 3.5.2 --- Methylation-specific PCR (MSP) --- p.42 / Chapter 3.5.2.1 --- Bioinformatics prediction of CpG island --- p.42 / Chapter 3.5.2.2 --- Primers design --- p.42 / Chapter 3.5.2.3 --- PCR reaction --- p.42 / Chapter 3.5.3 --- Bisulfite Genomic Sequencing (BGS) --- p.43 / Chapter 3.5.3.1 --- Primers design --- p.43 / Chapter 3.5.3.2 --- PCR reaction --- p.44 / Chapter 3.6 --- Construction of expression vectors of candidate genes --- p.44 / Chapter 3.6.1 --- Construction of IRF8 expression vector --- p.44 / Chapter 3.6.2 --- Construction of PTPRO expression vector --- p.44 / Chapter 3.6.2.1 --- Experimental design --- p.44 / Chapter 3.6.2.2 --- PCR and cloning of PCR products --- p.46 / Chapter 3.6.2.3 --- Restriction digestion of cloning vectors and expression vector --- p.48 / Chapter 3.6.2.4 --- Ligation of cloning fragments --- p.48 / Chapter 3.7 --- Colony formation assay on monolayer culture --- p.48 / Chapter 3.8 --- Statistical analysis --- p.49 / Chapter Chapter 4 --- Identification of candidate TSGs in deleted regions --- p.50 / Chapter 4.1 --- Research plan --- p.50 / Chapter 4.2 --- Results --- p.50 / Chapter 4.2.1 --- Mapping of the deleted B AC clones on their chromosomal locations --- p.50 / Chapter 4.2.2 --- Identification of down-regulated genes in NPC by semi-quantitative RT-PCR analysis --- p.51 / Chapter 4.3 --- Discussion --- p.55 / Chapter Chapter 5 --- Tumor suppressor function studies of candidate TSGs --- p.60 / Chapter 5.1 --- Research plan --- p.60 / Chapter 5.2. --- IRF8 is the 16q candidate TSG --- p.60 / Chapter 5.2.1 --- Frequent silencing of IRF8 mRNA expression in multiple carcinomas --- p.60 / Chapter 5.2.2 --- Methylation status of IRF8 promoter region correlated with its transcriptional silencing --- p.62 / Chapter 5.2.3 --- Restoration of IRF8 expression by pharmacological and genetic demethylation --- p.65 / Chapter 5.2.4 --- IRF8 inhibited the anchorage dependent growth of tumor cells on monolayer culture --- p.67 / Chapter 5.2.5 --- Discussion --- p.68 / Chapter 5.3 --- PTPRO is the down-regulated target at 12pl3.2-12.3 tumor suppressor locus --- p.73 / Chapter 5.3.1 --- Frequent silencing of PTPRO in multiple carcinoma cell lines --- p.73 / Chapter 5.3.2 --- Frequent methylation of PTPRO promoter CpG island in multiple carcinoma cell lines correlated with its reduced expression --- p.74 / Chapter 5.3.3 --- Re-expression of PTPRO by pharmacological and genetic demethylation --- p.77 / Chapter 5.3.4 --- PTPRO inhibited the growth of tumor cells in vitro --- p.79 / Chapter 5.3.5 --- Discussion --- p.81 / Chapter 5.4 --- RERG is another candidate TSG in 12pl3.2 - 12.3 region --- p.87 / Chapter 5.4.1 --- Down-regulation of RERG mRNA expression in carcinoma cell line --- p.87 / Chapter 5.4.2 --- Hypermethylation of RERG promoter is a frequent event in multiple carcinomas --- p.88 / Chapter 5.4.3 --- Re-expression of RERG mRNA following pharmacological and genetic demethylation --- p.90 / Chapter 5.4.4 --- Discussion --- p.92 / Chapter Chapter 6 --- General discussion --- p.96 / Chapter Chapter 7 --- Summary --- p.101 / Reference --- p.103

Ng, Ka Man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 103-113). / Abstracts in English and Chinese. / Acknowledgements --- p.i / List of abbreviations --- p.ii / List of Tables --- p.iv / List of Figures --- p.v / List of Publications --- p.viii / Abstract in English --- p.ix / Abstract in Chinese --- p.xi / Table of Contents --- p.xiii / Chapter Chapter 1 --- Literature Review --- p.1 / Chapter 1.1 --- Tumor suppressor genes (TSGs) and the modes of TSG inactivation during carcinogenesis --- p.1 / Chapter 1.2 --- Epigenetic modifications --- p.3 / Chapter 1.2.1 --- DNA methylation --- p.4 / Chapter 1.2.1a --- Establishment of DNA methylation patterns and DNA methyltransferases --- p.5 / Chapter 1.2.1b --- DNA hypermethylation and carcinogenesis --- p.6 / Chapter 1.2.1c --- Mechanism for gene silencing by CpG methylation --- p.6 / Chapter 1.2.1d --- DNA hypomethylation and carcinogenesis --- p.10 / Chapter 1.2.1e --- Loss of imprinting and carcinogenesis --- p.11 / Chapter 1.2.1f --- Potential factors leading to aberrant methylation patterns in cancers --- p.12 / Chapter 1.2.2 --- Deregulation of histone modifications and carcinogenesis --- p.14 / Chapter 1.2.3 --- Interplay between chromatin modifications and DNA methylation --- p.15 / Chapter 1.3 --- Identification of tumor suppressor genes (TSGs) --- p.17 / Chapter 1.4 --- Nasopharyngeal carcinoma as a cancer model of the current project --- p.18 / Chapter 1.5 --- Genetic and epigenetic changes in NPC --- p.19 / Chapter 1.6 --- Involvement of 5qll-ql2 and 14q32 in carcinogenesis --- p.22 / Chapter 1.6.1 --- Chromosome 5ql l-ql2 and carcinogenesis --- p.22 / Chapter 1.6.2 --- Chromosome 14q32 and carcinogenesis --- p.24 / Chapter 1.7 --- Clinical implications of epigenetics in cancers --- p.27 / Chapter Chapter 2 --- Aims of study and Research plan --- p.31 / Chapter Chapter 3 --- Materials and Methods --- p.34 / Chapter 3.1 --- Cell lines and Normal Tissues --- p.35 / Chapter 3.2 --- Routine cell line maintenance --- p.35 / Chapter 3.3 --- Drug treatments --- p.35 / Chapter 3.4 --- Total RNA extraction --- p.35 / Chapter 3.5 --- Genomic DNA extraction --- p.36 / Chapter 3.6 --- General techniques --- p.37 / Chapter 3.6.1 --- Gel electrophoresis --- p.37 / Chapter 3.6.2 --- DNA and RNA quantification --- p.37 / Chapter 3.6.3 --- LB medium and LB plate preparation --- p.38 / Chapter 3.6.4 --- Plasmid extraction --- p.38 / Chapter 3.6.4a --- Mini-scale preparation of plasmid DNA --- p.38 / Chapter 3.6.4b --- Large-scale preparation of endotoxin-free plasmid DNA --- p.39 / Chapter 3.6.5 --- DNA sequencing --- p.39 / Chapter 3.7 --- Reverse transcription-PCR (RT-PCR) --- p.40 / Chapter 3.7.1 --- Reverse transcription (RT) --- p.40 / Chapter 3.7.2 --- Semi-quantitative RT-PCR --- p.41 / Chapter 3.8 --- Methylation analysis --- p.42 / Chapter 3.8.1 --- Sodium bisulfite modification of DNA --- p.42 / Chapter 3.8.2 --- CpG island analysis --- p.42 / Chapter 3.8.3 --- Methylation-specific PCR (MSP) --- p.43 / Chapter 3.8.4 --- Bisulfite genomic sequencing (BGS) --- p.44 / Chapter 3.9 --- Construction of expression plasmids --- p.45 / Chapter 3.9.1 --- Construction of the MGC80-expressing vector --- p.45 / Chapter 3.9.2 --- Construction of the TUSC14-expressing vector --- p.46 / Chapter 3.10 --- Functional analyses --- p.47 / Chapter 3.10.1 --- Monolayer colony formation assay --- p.47 / Chapter 3.10.2 --- Soft agar assay --- p.48 / Chapter 3.11 --- Statistical analysis --- p.49 / Chapter Chapter 4 --- Results --- p.50 / Chapter 4.1 --- Identification of 5qll-ql2 and 14q32.2-q32.32 as frequently deleted regions in NPC by aCGH --- p.50 / Chapter 4.2 --- Identification of novel candidate TSGs at chromosome 5qll-ql2 through integrative genomics and epigenetics --- p.51 / Chapter 4.2.1 --- Expression profiling of the candidate genes at 5ql l-ql2 in NPC cell lines --- p.51 / Chapter 4.2.2 --- MGC80 as a target of study at 5ql2 --- p.54 / Chapter 4.2.2a --- Ubiquitous expression in normal human tissues and frequent down-regulation of MGC80 in multiple tumor cell lines --- p.54 / Chapter 4.2.2b --- Methylation analysis of MGC80 --- p.56 / Chapter 4.2.2c --- Restoration of MGC80 expression after pharmacologic and genetic demethylation --- p.59 / Chapter 4.2.2d --- Functional study of MGC80 in multiple carcinomas --- p.61 / Chapter 4.2.2e --- Discussion --- p.63 / Chapter 4.2.3 --- TUSC14 as a target of study at 5ql2 --- p.67 / Chapter 4.2.3a --- TUSC14 was broadly expressed in normal human tissues and frequently down-regulated in multiple tumor cell lines --- p.67 / Chapter 4.2.3b --- Methylation analysis of TUSCI4 --- p.69 / Chapter 4.2.3c --- Pharmacologic and genetic demethylation reactivated TUSC14 expression --- p.72 / Chapter 4.2.3d --- Functional study ofTUSC14 in multiple carcinomas --- p.74 / Chapter 4.2.3e --- Discussion --- p.76 / Chapter 4.3 --- Identification of candidate TSGs at chromosome 14q32 through integrative genomics and epigenetics --- p.80 / Chapter 4.3.1 --- Expression profiling of the candidate genes at 14q32 in NPC cell lines --- p.80 / Chapter 4.3.2 --- DLK1 as a target of study at 14q32 --- p.82 / Chapter 4.3.2a --- Expression analysis of DLK1 in normal tissues and NPC cell lines --- p.82 / Chapter 4.3.2b --- Methylation analysis ofDLKl in NPC --- p.83 / Chapter 4.3.2c --- Restoration of DLK1 expression after pharmacologic demethylation --- p.84 / Chapter 4.3.2d --- Functional study ofDLKl in NPC --- p.85 / Chapter 4.3.2e --- Discussion --- p.87 / Chapter Chapter 5 --- General discussion --- p.92 / Chapter Chapter 6 --- Summary --- p.99 / Chapter Chapter 7 --- Future study --- p.101 / Reference list --- p.103

The retinoblastoma tumor suppressor protein, Rb, is a key regulator of the mammalian cell cycle and its inactivation facilitates S-phase entry. Rb is inactivated through multiple waves of phosphorylation, mediated mainly by kinases associated with D and E type cyclins in the G1 phase of the cell cycle. Our earlier studies had shown that the signaling kinase Raf-1 (c-Raf) physically interacts with Rb upon growth factor stimulation and initiates the phosphorylation cascade. We had shown that an 8 amino acid peptide derived from Raf-1 could disrupt the Rb-Raf-1 interaction leading to an inhibition of Rb phosphorylation, cell proliferation and tumor growth in nude mice. Here, we describe a newly identified orally-active small molecule, RRD-251 (Rb - Raf-1 Disruptor 251), that disrupts potently and selectively the binding of Raf-1 to Rb; it had no effect on Rb-HDAC1, Rb-Prohibitin, Rb-Ask1, Rb-cyclin E, or Raf-1-Mek interactions. RRD-251 inhibited anchorage-dependent and -independent growth of human cancer cells; it could also potently inhibit angiogenesis both in vitro and in vivo. Oral or intra-peritoneal administration of RRD-251 resulted in a significant suppression of growth of tumors xenotransplanted into athymic nude mice; the tumor suppressive effects were restricted to tumors carrying a wild-type Rb gene. Thus, selective targeting of Rb-Raf-1 interaction appears to be a promising approach for developing novel anti-cancer agents. In addition to mitogens, tobacco components like NNK and nicotine can induce cell proliferation and angiogenesis, contributing to lung cancer. Induction of cell proliferation by tobacco components required the binding of Raf-1 to Rb and RRD-251 could prevent nicotine induced cell proliferation. Our studies also show how nicotine not only promotes tumor growth in vivo, it also increases chance of tumor recurrence and metastasis. In addition to growth factors and tobacco components, cytokines like TNFα could induce Rb-Raf-1 interaction in vascular smooth muscle cells. Since TNFα-induced proliferation of vascular smooth muscle cells contributes to growth of atherosclerotic plaques, RRD-251 could be beneficial in controlling atherosclerosis as well. Thus, it appears that drugs that can disrupt the Rb-Raf-1 interaction might have beneficial effects in a wide spectrum of human diseases.

Prostate Apoptosis Response-4 (Par-4) is a conserved and ubiquitous tumor-suppressor factor which can selectively induce apoptosis in tumor cells, while leaving normal cells unaffected. While Par-4 is well established as a tumor-suppressor, there have yet been no formal investigations as to whether it has a physiologic role in normal tissues. Early observations of Par-4 knockout mouse lines yielded that the adult mice displayed significant weight gain and fat accumulation compared to their wild-type counterparts while on a conventional chow diet. Interestingly, obese mouse and human subjects were found to exhibit reduced expression of Par-4 in adipose tissue as well as lower levels of secreted Par-4 in their plasma, compared to samples collected from lean human subjects. Subsequent in vitro experiments would show that loss of Par-4 has significant impact upon adipogenesis. Mechanistically, Par-4 loss during adipogenesis in cell culture correlated inversely with expression of the adipogenic transcription factor PPARγ. Subsequent experiments would demonstrate that Par-4 transcriptionally represses PPARγ at the promoter level. Thereby, we conclude that Par-4 regulates adipogenesis and lipid accumulation through transcriptional repression of the PPARγ promoter. This research utilizes novel models and may be used as the basis for Par-4-mediated therapies for obesity and metabolic disease.

Single minded 2 (Sim2) is a member of the basic helix-loop-helix Per-ARNT-Sim (Period-Arylhydrocarbon Nuclear Translocator-Single minded) family. Human SIM2 is involved in the etiology of the Down’s phenotype. In addition to the physical and mental deficiencies associated with DS, it has become apparent that women with DS are 10-25 times less likely to develop breast cancer in comparison to age-matched normal populations. Such significant effects on breast cancer susceptibility are thought to result from gene dosage effects of one or more tumor suppressor genes on chromosome 21. Here we report the identification and transcriptional characterization of mouse Sim2s, a splice variant of Sim2, which is missing the carboxyl Pro/Ala-rich repressive domain. Similar to full-length Sim2, Sim2s interacts with ARNT and to a lesser extent, ARNT2. The effects of Sim2s on transcriptional regulation through hypoxia-, dioxin- and central midline response elements are different than that of full length Sim2. Specifically, Sim2s exerts a less repressive effect on hypoxia-induced gene expression than full length Sim2, but is just as effective as Sim2 at repressing TCDD-induced gene expression from a dioxin response element. Interestingly, Sim2s binds to and activates expression from a central midline response element-controlled reporter through an ARNT transactivation domain-dependent mechanism. Forced expression of SIM2s in MDA-MB-435 breast cancer cells significantly inhibited proliferation, reduced anchorage-independent growth, and decreased invasive potential. SIM2s directly decreased expression of matrix metalloprotease-3, a known mediator of breast cancer metastasis. In addition, loss of Sim2 in the mouse mammary gland increased ductal branching, accelerated lobuloalveolar-like precocious hyperplasia, and decreased cell apoptosis, suggesting that SIM2s is a mammary tumor suppressor. Sim2-/- mammary glands lose E-cadherin expression, suggesting that Sim2s plays a role in regulating E-cadherin/beta-catenin signaling. Loss of Sim2 in the mammary glands also resulted in dramatically increased MMP3 expression. The mechanism of SIM2smediated repression of MMP3 was found to be due to its ability to inhibit AP-1 binding to the MMP3 promoter. These results suggest that SIM2s contributes to the breast cancer protective effects observed in DS individuals.

Bladder cancer is a common malignancy affecting the genitourinary system. Although a large number of studies have been carried out on these areas for a long time, little is know about the molecular events which may involve in tumorigenesis. Until now, no profound immunohistological or molecular markers have been identified to define clinically relevant subsets of bladder cancer. The purpose of this thesis is to identify a novel bladder cancer carcinogenesis related genes. Chapter 1 attempts to illustrate the background, molecular markers, chromosomal abnormalities and genetic instability related to bladder cancer. In Chapter 2, various bioinformatics methodologies were used to annotate and identify candidate genes. Twenty-one genes were identified 1.5-fold up- or down-regulated in mRNA expression from RT4, TSGH8301 and J82, three different stages of bladder cancer cell lines by microarray chips (Dr. Liu, personal communications). Another eight candidate tumor suppressor genes were preliminarily identified from suppression subtractive hybridization (SSH) cDNA library of RT4 cell line based on an isoflavones-treated minus non-treated and further subjected to quantitative RT-PCR analyses to confirm the mRNA expression level in different stages of bladder cancer cell lines. Chapter 3 studies on the ANXA10 gene with special emphasis on its cloning, protein expression, subcellular localization and the preparation of polyclonal antibody. The result suggests that ANXA10 is a cytoplasmic protein in N18 cells. Chapter 4 analyzes the CDK2AP1 gene in mRNA and protein level at different bladder cancer cell lines and various specimens. In our preliminary observations, there are lost of CDK2AP1 expressions at invasive TCCs specimens when compared to noninvasive TCCs specimens. The mechanism of the tumor-associated loss of the CDK2AP1 expression is currently not clear. In Chapter 5, bladder cancer cell lines TSGH8301, UB37, TCCSUP and J82 in SCID mice xenograft model were established for further in vivo studies.

ABSTRACT Chibby (or PIGEA-14) is a novel antagonist of the Beta-catenin pathway in nucleus. However, the tumor-suppressing function of Chibby and the importance of nuclear targeting to the cellular functions of Chibby have not been validated. By fusion of Chibby cDNA with green fluorescent protein (GFP) or Flag-tag, it was found that exogenous Chibby expression was detected in the nucleus as well as cytoplasm of transfected HeLa cells, but with a preferential nuclear localization (more than 50% cells with nuclear Chibby expression). Chibby overexpression significantly abrogated the cellular Beta¡Vcatenin activities and induced apoptosis in HeLa cells. Moreover, Chibby gene delivery attenuated the proliferation, migration, and anchorage-independent growth of HeLa cells, supporting the tumor suppressor function of Chibby. Mutation or deletion of the predicted nuclear localization sequence (NLS), at residues 123-126, significantly promoted the cytoplasmic localization of Chibby, indicating residues 123-126 is the NLS domain of Chibby. Interestingly, ecotopic expression of Chibby NLS mutants remained capable of inducing apoptosis and inhibiting Beta¡Vcatenin activities in HeLa cells. Besides, overexpression Chibby NLS mutants effectively attenuated the viability, motility and colonies formation of HeLa cells. Expression analysis revealed that Chibby NLS mutants retained Beta-catenin in the cytoplasm and prevented its nuclear entry, thereby inhibiting the Beta-catenin transcriptional activities. In summary, Chibby shuttles between nucleus and cytoplasm, and possesses the functions of tumor suppressor and Beta-catenin antagonist.

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 (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 338-340). Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 338-340). Also available online.