published_or_final_version / Pathology / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Pathology / Master / Master 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.

Background & Aims: By whole genome sequencing, we identified for the first time that solute carrier family 12 member 5 (SLC12A5) gene located on chromosome 20q13.12 was amplified in colorectal cancer (CRC). We aimed to determine the amplification status of SLC12A5 and its clinical implication in CRC, and characterize the functional mechanisms of SLC12A5 in colorectal carcinogenesis. / Materials and Methods: Protein expression level of SLC12A5 was evaluated by immunohistochemistry. SLC12A5 amplification was verified by fluorescence in situ hybridization (FISH). The correlations between SLC12A5 expression and clinicopathologic parameters as well as the prognosis impact of SLC12A5 were analyzed in 195 CRC patients. The biological function of SLC12A5 in CRC cell lines were determined by cell viability, colony formation, invasion, migration, flow cytometry and in vivo tumorigenicity assays. Standard tail vein metastatic assay was performed to examine the effect of SLC12A5 in lung metastasis in nude mice. Western blot, luciferase reporter assays and human tumor metastasis PCR array were performed to evaluate SLC12A5 downstream effectors and related pathways. / Results: RT-PCR showed SLC12A5 was readily expressed in 7 of 9 CRC cell lines, but was absent in normal colorectal tissues. The mean protein expression level of SLC12A5 was significantly higher in primary CRCs as compared to their adjacent normal tissues. Amplification of SLC12A5 was detected in 40.8% (78/191) of primary CRCs by FISH, which was positively correlated with its protein overexpression (P < 0.001). Overexpression of SLC12A5 was positively associated with a more advanced TNM stage (P < 0.05). Multivariate Cox regression analysis showed that SLC12A5 overexpression was an independent predictor of poorer survival of CRC patients (P = 0.018). We further tested the biological function of SLC12A5 in human colon cancer cells. Ectopic expression of SLC12A5 in colon cancer cells SW480 and SW1116 increased proliferation and colony formation. Silencing SLC12A5 expression in HCT116 by siRNA had the opposite effects in vitro, and knockdown of SLC12A5 by shRNA significantly inhibited xenograft tumor growth in nude mice. We further revealed that SLC12A5 inhibited apoptosis of colon cancer cells by mediating apoptosis-inducing factor (AIF) and endonuclease G (EndoG) -dependent apoptotic signaling pathway. Moreover, gain-and loss-of-function experiments showed that SLC12A5 enhanced cell invasion and migration in vitro. Knockdown of SLC12A5 by shRNA significantly inhibited lung metastasis in nude mice. SLC12A5 promoted tumor metastasis through regulating key elements of the matrix architecture, such as matrix metallopeptidase and fibronectin. / Conclusion: We have identified a novel amplification gene SLC12A5 which is overexpressed in CRC. SLC12A5 may be an independent prognostic marker for CRC and may play a pivotal oncogenic role in colorectal carcinogenesis by inhibiting apoptosis and promoting metastasis. / 背景和目的：通過對結直腸癌進行全基因組測序，我們首次發現位於染色體20q13.12的SLC12A5基因在結直腸中擴增。本研究旨在探索SLC12A5在結直腸癌中的擴增情況和臨床意義，并進一步研究SLC12A5在結直腸癌發生發展中的作用機制。 / 材料和方法：採用免疫组化方法檢測SLC12A5的蛋白表达水平。應用熒光原位雜交方法驗證SLC12A5基因的擴增情況。在195例結直腸癌患者中对SLC12A5表达與临床病理關係及其對預後的影響其进行分析。通过檢測細胞活力、細胞集落形成實驗、侵襲實驗、遷移實驗、流式細胞術和體內成瘤實驗以研究SLC12A5在結直腸癌中的生物学功能。進而通過免疫印跡、熒光素酶報告實驗和人腫瘤轉移的PCR陣列，探索SLC12A5調控的基因和相关途径。 / 结果：我們採用RT-PCR方法檢測SLC12A5在9株結直腸癌細胞株的表達情況，SLC12A5在7株結直腸癌細胞株中穩定表達，但是在正常大腸組織中表達沉默。SLC12A5在結直腸中的平均蛋白表達水平顯著高於其鄰近的正常組織。通過熒光原位雜交方法，在40.8% （78/ 191）的結直腸癌中檢測到SLC12A5的擴增，該基因的擴增與其蛋白高表達水平呈正相關關係。SLC12A5高表達水平跟晚期TNM分期密切相關（P <0.05）。多因素Cox回歸分析表明，SLC12A5高表達是結直腸癌患者較差的生存的獨立預測因子（P = 0.018）。我們進一步在人結腸癌細胞株中檢測SLC12A5的生物功能。在結腸癌細胞SW480和SW1116中過度表達SLC12A5促進細胞增殖和集落形成。siRNA敲低HCT116 細胞SLC12A5的表達在體外實驗中有相反的效果。此外，shRNA敲低SLC12A5的表達顯著抑制裸鼠移植瘤的生長。我們進一步發現，SLC12A5通過介導凋亡誘導因子（AIF）和核酸內切酶G（EndoG）-依賴的細胞凋亡信號轉導通路抑制結腸癌細胞的凋亡。此外，功能獲得性和功能缺失性的體外實驗表明，SLC12A5促進腫瘤細胞的侵襲和遷移。尾靜脈注射實驗表明shRNA敲低SLC12A5的表達顯著抑制裸鼠肺轉移。SLC12A5通過調節基質結構的關鍵因子，如基質金屬蛋白酶和纖維連接蛋白，促進腫瘤轉移。 / 结论：我們發現了一個新的擴增基因SLC12A5，該基因在結直腸癌中高表達。SLC12A5是結直腸癌的一個獨立的預後標誌物。SLC12A5通過抑制細胞凋亡和促進腫瘤轉移，在結直腸癌的發生發展中起了舉足輕重的致癌作用。 / Xu, Lixia. / Thesis Ph.D. Chinese University of Hong Kong 2014. / Includes bibliographical references (leaves 107-120). / Abstracts also in Chinese. / Title from PDF title page (viewed on 05, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

Colorectal cancer (CRC) is a major problem in affluent countries worldwide. In Australia it is the second most commonly diagnosed malignancy with approximately 13,000 new cases diagnosed each year. This disease is also the leading cause of cancer related death in Australia with approximately 4,500 fatalities each year. Epidemiological studies have shown geographical variation in the incidence of disease, with diet considered to be a key contributing factor to CRC risk. In particular, diets high in fibre and low in fat have been demonstrated to reduce the risk of developing CRC. Fibre is heterogeneous in nature and can be categorised into different subtypes. Resistant starch is a component of fibre which remains largely intact throughout the gastrointestinal tract until it reaches the colon. Here it undergoes bacterial fermentation to produce the short chain fatty acids (SCFAs) acetate, propionate and butyrate (BuA). Each of the SCFAs are bioactive in the colon, with the most active being BuA. The beneficial effects of fibre have been linked to BuA’s ability to induce colon cancer cell differentiation, reduce proliferation and initiate apoptosis. Interestingly, in normal cells BuA is utilised as the preferential energy source and has been shown to promote proliferation. With an apparent “paradoxical effect” on normal and cancerous cells BuA has been the subject of much investigation as a potential anticancer agent. Despite numerous studies investigating BuA actions, the exact biological mechanisms remain largely undefined. This thesis explored a possible mechanism for BuA-induced apoptosis and inhibition of proliferation. In 2003, two publications provided evidence that SCFAs, including BuA, were ligands to two members of a previously orphan family of G-protein coupled receptors (GPCRs); GPCR41 and 43. Of the two receptors BuA had the strongest effect on GPCR43. Consequently this thesis investigated the possibility that BuA acts to decrease CRC proliferation and induce apoptosis by binding to and activating GPCR43 on CRC cells. It was hypothesised that GPCR43 acted as a “BuA sensor” on the surface of the cell to mediate the effects of BuA. This experimental work utilised PCR, Q-PCR, measures of apoptosis, proliferation and differentiation and RNAi knockdown. The key areas of investigation included: (1) Determining if GPCR43 was present on a range of CRC cell lines with a cell line to represent adenocarcinoma, carcinoma and metastatic stage of disease. (2) Investigating the expression of GPCR43 with manipulated nutrient media and different levels of cell confluence. (3) Exploring GPCR43 expression in normal and malignant human patient biopsies. (4) Determining if the inhibition of G-protein function using inhibitors influenced BuAinduced changes to apoptosis and proliferation. (5) Using RNAi, investigating the effect that GPCR43 knockdown would have on BuA-induced changes to proliferation and apoptosis. The key findings from this work included: (1) Presence of GPCR43 on some but not all CRC cell lines. (2) Modulation of GPCR43 expression with exposure to BuA and altered glucose concentrations in the media. (3) An influence of G-protein inhibition on BuA-induced apoptosis but not proliferation in some cell lines. (4) GPCR43 knockdown using RNAi indicated that GPCR43 is not exclusively required for BuA to regulate apoptosis and proliferation. The results from this work indicate that GPCR43 is not likely to exclusively mediate BuA’s effects, but opens up new areas of research into the exact role of GPCR43 on CRC cells. / Thesis (Ph.D.) - University of Adelaide, School of Molecular and Biomedical Science, 2008

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

Colorectal cancer (CRC) is the second most common cancer in Hong Kong. While high-penetrance germline mutations account for up to 6% of cases, much of the variation in genetic risk may be attributable to multiple low-penetrance variants. Previous genome wide association studies (GWAS) have identified a number of CRC susceptibility alleles in Caucasian populations. Our GWAS investigated the association between genetic variants with CRC risk in the Han Chinese population in Hong Kong. In Stage I, genomic DNA samples from 455 female Chinese CRC subjects were genotyped using the Illumina 610 Quad SNP chip. Association analysis was performed on 439 cases and 771 general population female controls recruited for a study on bone mineral density. Population stratification was examined through principal components analysis using EIGENSTRAT version 2.0. From the association results, 46 SNPs (Group 1) were selected for follow-up replication (Stage II), together with 10 SNPs (Group 2) from previous GWAS studies. Genomic DNA samples from 3,571 Chinese subjects were genotyped using Sequenom MassARRAY system. Association analysis was performed on 1,505 cases and 1,452 controls. 5 SNPs (rs835378, rs2652007, rs2139273, rs2139273 and rs9286410) exceeded the genome-wide significance level in stage I, although none replicated in Stage 2, suggesting genotyping error. Results from stage II showed that the three most significant SNP were among those selected from the previous studies, yet their significance levels in Stage I were very weak . None of the SNPs selected from Stage I was significant at p<0.01 in Stage 2. Two composite scores of genetic susceptibility, one for each group of SNPs, were calculated in stage II genotype data, as the total number of high-risk alleles (according to the direction of effect in Stage I results or previous GWAS) present in an individual. Both composite scores were significantly associated with CRC risk in Stage 2 (Group 1, p=2.38 x 10-5, beta=0.046, SE=0.012; Group 2 p=1.06 x 10-7, beta=0.10, SE=0.019), suggesting that while we had insufficient power to confirm individual SNPs identified in our GWAS and the previous GWAS, these findings indicate that the SNP sets selected from Stage I results, as well as those selected from previous GWAS, contain SNPs with genuine effects on CRC risk. One SNP, rs10795668 (OR = 0.79 [CI] 95%:0.71 – 0.87 p=3.78 x 10-6), was significantly associated with CRC risk in Stage II after adjustment for multiple testing. Two further SNPs, rs6983267 and rs4939827, also achieved suggestive p-values in Stage II. All these SNPs were selected from previous GWAS in the Caucasian population, demonstrating that shared genetic factors operate for CRC in diverse populations. / published_or_final_version / Psychiatry / Master / Master of Philosophy

Polycomb group (PcG) proteins governs the regulation of diverse cellular functions, such as cell fate decision, cell cycle progression, maintenance of embryonic stem cell pluripotency, and DNA damage repair. Although aberrant expression of PcG proteins has been frequently reported in different cancer types, CBX8 is one of the least studied PcG family members in cancer. Recently, a study showed that forced expression of CBX8 in normal human and mouse fibroblasts demonstrated that cells could bypass senescence via INK4a-ARF repression; while another report demonstrated that CBX8 was involved in MLL-AF9-linked leukemogenesis. Despite accumulating evidence on CBX8-related carcinogenic functions, the role of CBX8 in solid cancers has not been investigated thus far. This study is therefore initiated to investigate and establish the functional role of CBX8 in colorectal cancer. In this study, expression of CBX8 in 121 pairs of human CRC samples was analyzed by immunohistochemistry; and data were correlated with different clinicopathological parameters. To evaluate the functional effects of CBX8, CBX8 overexpressed and downregulated clones were established from three CRC cell lines. The in vitro effects of CBX8 on cell proliferation, cell cycle progression and apoptosis profiles were investigated; and the effects of CBX8 on tumorigenicity in vivo were further demonstrated in mice xenograft models. The results showed that CBX8 expression was downregulated or loss in approximately 48.8% of human colorectal tumors, and downregulated or loss of CBX8 expression were mainly observed in tumors with intermediate to later stages (stage II to IV). Moreover, expression of CBX8 showed a significant inverse correlation with colorectal tumor sizes (P < 0.0001). Ectopic expression of CBX8 in CRC cell lines resulted in inhibition of cell proliferation, clonogenic ability and anchorage-independent growth, which are hallmarks of tumorigenesis. Conversely, downregulation of CBX8 promoted proliferation and clonogenic ability. Moreover, it was found that restoring CBX8 expression could induce G0/G1 arrest of cell cycle. The tumor suppressive role of CBX8 in colorectal cells was further demonstrated in vivo through subcutaneous and orthotropic mice tumor models; followed by immuno-staining of the proliferation marker Ki-67. To unveil the possible mechanisms behind the tumor suppressing effects of CBX8, two signalling pathways commonly engaged in CRC were evaluated. At least part of the effects could be attributed to the mediation of MAPK signaling pathway; whereas the Wnt signalling was not affected by CBX8. This study demonstrated for the first time the loss of CBX8 expression in intermediate and late stage tumors, and was the first to report the tumor suppressing ability of CBX8 in solid cancers. The effects of CBX8 in this study were different to the functional implications reported in the current literature. This functional divergence in distinct cell types suggested a dynamic role of CBX8 depending on specific cellular context. / published_or_final_version / Surgery / Master / Master of Philosophy

Colorectal cancer has been a major health issue worldwide. Not only it affects the patients but it also carries physical and psychological influences to their caregivers. Despite the concerns of the psychological needs of caregivers of colorectal cancer patients, there has been a lack of a good understanding of their needs, and how to intervene in order to alleviate their psychological problems and burdens. Therefore, this thesis aimed at designing and evaluating a nurse-led telephone based psychosocial education program for improving the psychological conditions and quality of life among Chinese caregivers of patients with colorectal cancer. The nurse-led telephone based psycho-educational program was designed based on the transactional model of stress and copying. It was piloted on 6 caregivers and refined. Its efficacy over the patients discharged under the ‘usual routine hospital standard discharge care procedure’ was assessed in a randomized controlled trial on 140 Chinese caregivers of colorectal cancer patients. Caregivers in the intervention group received three telephone calls from an experienced Nurse Interventionist at 1, 3 and 5 weeks after the patients’ discharge. Each call addressed any unmet needs of the caregivers with the provision of education and psychological support. At baseline, 2 weeks, 4 weeks and 8 weeks, all caregivers were assessed for the primary outcome of depression measured by the Depression Anxiety Stress Scale (DASS), and for the secondary outcomes of anxiety, stress, burden of care and quality of life. The mixed effects model, which takes into account the extra-covariance among repeated measurements, and which is consistent with the intention-to-treat principle, was used in the efficacy analysis. Of the 140 caregivers recruited in the randomized controlled study, 5 dropped out before the end of the study. However, all the caregivers were included in the analysis. There was no significant baseline difference between the intervention and ‘usual care’ groups. The psycho-education program reduced depression more than the ‘usual care’ group by2.7 (95% CI = 0.6 to 4.8, p=0.013) units in DASS at 2 weeks, and even more by 3.5 (95% CI = 1.7 to 5.24, p<0.001) at 4 weeks. However, the ‘usual care’ group caught up at 8 weeks, and no significant effect of the psycho-education program was found (p=0.144). Moreover, the program also reduced anxiety and stress more than the ‘usual care’ group by1.83 (95% CI = 0.61 to 3.50, p=0.004) and 3.50 (95% CI = 1.74 to 5.25, p<0.001) respectively at follow-up. In addition, the burden of care and quality of life were also generally improved more in the psycho-education program group. Furthermore, strong positive associations among depression, stress, anxiety, and burden of care were found. Caregivers perceived to have a high burden of care would be associated with more depression, stress or anxiety(r = 0.53, p<0.001). Moreover, depression, anxiety, and stress had a strong negative association with the physical, psychological, social relationship and environmental well-being but not with social relationships(r = -0.16, p = 0.550). In conclusion, this thesis has developed the first nurse-led telephone based psycho-education program for caregivers of colorectal cancer patients. The program can effectively help caregivers in reducing their feelings of stress from depression, anxiety, stress and the burden of care, as well as improving their quality of life. It paves the way for a new direction for a comprehensive colorectal cancer care service in addressing the caregivers’ needs. / published_or_final_version / Nursing Studies / Doctoral / Doctor of Nursing

The IGF system is a crucial regulator of normal growth and development, however dysregulation of the system on multiple levels is associated with the incidence of a wide variety of malignancies including the breast, thyroid, lung, and colon, making the IGF system an important anti-cancer therapeutic target. Due to its role in mediating cellular proliferation, protection from apoptosis, and metastasis, traditional focus has been set on examining the role of the type 1 IGF receptor [IGF1R] in cancer. However there is mounting evidence to suggest the insulin receptor [IR] may also be involved in the potentiation and pathogenesis of cancers. The observation that IGF-II is overexpressed, compared to normal tissues, by cancers suggests signaling via target receptors by this ligand has important implications on cancer pathogenesis. Indeed, both the IGF1R and IR have been demonstrated to be up-regulated in a variety of malignancies. In regards to IR isoform, the IGF-II binding IR-A is preferentially expressed by a number of cancer cell types. Together with the observation that an autocrine proliferative loop exists between IGF-II and the IR-A in malignant thyrocytes and cultured breast cancer cells, suggests signaling via the IR-A may play a role in cancer cell growth and survival. However, very few studies on the IR-A have been conducted in cells co-expressing the IGF1R. This is mainly due to the difficulties associated with discrimination between signaling arising from IGF1R homodimers, IR-A homodimers, and IGF1R/IR-A hybrid receptors. It is not known how the IR-A interacts, and functions in conjunction with the other receptors of the IGF system to signal biologically relevant outcomes, especially in terms of anti-cancer therapeutics that aim to block and down-regulate the IGF1R. Current anti-cancer therapies targeting the IGF system have concentrated on blocking IGF signaling via the IGF1R, due mostly to the functional properties of the receptor, but also in part due to the metabolic consequences associated with blockade and inhibition of the IR. This individual targeting of the IGF1R potentially leaves a pathway by which IGF-II secreted by the tumour can circumvent current IGF1R based therapies. Consequently, this thesis investigated whether the IR-A could compensate for the targeted loss of the IGF1R and how the IR-A interacts with the IGF1R in cells co-expressing these two receptors. In addition, the individual ability of the IR isoforms to signal biological outcomes in response to IGF stimulation was assessed. The main experimental techniques used throughout this body of work included; assessment of protein expression and activation by Western blot, siRNA mediated gene silencing, and measures of cell proliferation, survival, and migration. The key areas of investigation included: 1. Investigation of the individual ability of the IR isoforms to signal biological outcomes in response to IGF stimulation 2. Identification of an appropriate cell line model in which to investigate the interactions between the IR-A and IGF1R 3. Optimisation of siRNA mediated knock-down of the IR-A and IGF1R in SW480 colorectal adenocarcinoma cells 4. Determination of the biological role of the IR-A in SW480 cells co-expressing the IGF1R The key findings from this work included: 1. The IR-A could not compensate for IGF1R depletion in SW480 cells 2. Dual silencing of the IR-A and IGF1R indicated signaling via the IGF1R was dominant to signaling via the IR-A in SW480 cells 3. Signaling via IR-A/IGF1R hybrid receptors may not be as potent as signaling via IGF1R homodimers 4. IGF-I at physiological concentrations can stimulate biological responses via both isoforms of the IR. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1337339 / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2008