Sir Peter MacCallum Department of Oncology - Theses
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ItemImproving Ovarian Cancer Care Along The Disease Trajectory: From Prevention to Disease Management( 2019)The overarching objective of this thesis was to investigate key clinical care questions along the ovarian cancer disease trajectory and formulate strategies to improve care provision. This thesis focused on three time points on the trajectory: i) cancer prevention; ii) tolerability of experimental treatment at disease recurrence; and iii) development of malignant bowel obstruction. For women at high risk of developing ovarian cancer, such as those with a germline BRCA1 or BRCA2 mutation (gBRCA1/2mut), risk-reducing salpingo-oophorectomy (RRSO) is the most effective preventative method and recommended by peak bodies. RRSO involves complete resection of the ovaries and fallopian tubes up to the insertion into the cornua of the uterus. The resection of the fallopian tubes is necessary as it is known that BRCA1- and BRCA2-associated gynaecologic cancers appear to originate in the fimbrial end of the fallopian tubes rather than the ovaries, even though they have been typically labelled as “serous ovarian cancer”. Previous research had raised concerns that the quality of RRSO surgery and associated pathology evaluation performed in Australasian women had been suboptimal prior to 2008. I therefore undertook an investigation of the quality of contemporary RRSO and compared it with data from the historical research, examining the clinical predictors of RRSO quality. Across 78 institutions in Australia and New Zealand, a total of 164 study participants had RRSO performed and the quality of RRSO, in particularly the related pathology examination, had improved significantly compared to the previous report. The proportions of women who received adequate surgery and pathology evaluation were 99% and 66% respectively, compared to 91% and 23%, respectively (P<0.001) in the previous study. Implementable clinical strategies to potentially further improve quality were identified and included i) to direct RRSO referral to a gynaecologic oncologist (rather than general gynaecologist or general surgeon) and ii) to ensure the reporting pathologist is aware that the intent of surgery is risk-reduction in a high-risk woman, in order to prompt adequate processing and review of the RRSO specimens for occult cancer and pre-malignant lesions. In women with gBRCA1/2mut who undergo RRSO, whether hysterectomy should be performed at the time of RRSO to prevent uterine cancer was controversial. I therefore investigated the incidence of uterine cancer for Australasian gBRCA1/2mut carriers. Of the 828 eligible women identified from a prospective multi-institutional follow up study (kConFab), there were five cases of uterine cancer. Compared to the expected incidence in the Australian population, the standardised incidence ratio (SIR) was 2.45 (95%CI: 0.80-5.72; P=0.11). All five cases were of endometrioid adenocarcinoma histology and importantly, none had serous histology. Of those cases, three had a history of breast cancer and exposure to tamoxifen, a known risk factor for uterine cancer. Therefore, this finding did not justify the need for routine hysterectomy at the time of RRSO to reduce uterine cancer incidence in Australasian gBRCA1/2mut carriers. Disease progression in women with advanced ovarian cancer typically involves the omentum and peritoneum which causes abdominal symptoms. The goal of systemic treatment is to improve symptoms and delay further disease progression. Therefore, it is crucial that we consider the burden of treatment-related toxicities particularly in evaluation of novel drugs. Phase I clinical trials typically would include patients with different solid tumour types and are primarily intended to assess the safety and tolerability of investigational agents. Using the National Cancer Institute Phase I database, I performed a retrospective analysis of the adverse events (AEs) reported in women with gynaecological cancers compared to patients with other cancer types. Patients enrolled in the 150 phase I trials identified were divided into three groups to allow comparison; i) females with gynaecological cancers (n=685); ii) females with non-gynaecological cancers (n=1698); and iii) males with cancers (n=1886). Of those females with gynaecological cancers, the majority had ovarian cancer (n=527, 77%) followed by cervical cancer (n=76, 11%) and uterine cancer (n=72, 11%). Overall, females with gynaecological cancers were reported to have a significantly greater number of AEs during treatment (mean, 17.1 vs 14.7 vs 13.5, P<0.001), despite being similar at baseline (mean 7.0 vs 7.4 vs 7.0, P=0.09). In terms of AE severity, the main difference was a higher prevalence of grade 2 AEs reported in women with gynaecological cancers (mean 4.6 vs 3.9 vs 3.5). The five most prevalent AEs in women with gynaecological cancers were nausea (n=617, 90%), fatigue (n=587, 86%), anaemia (n=381, 56%), anorexia (n=357, 52%) and vomiting (n=355, 52%). These findings highlighted the need to improve the management for low-grade AEs in particular abdominal-related AEs for women with gynaecological cancers being treated on clinical trials. The inclusion of specific supportive care protocols/strategies into clinical trial protocols will better address symptom burden and improve quality of life. Malignant bowel obstruction (MBO) is a common complication for women with recurrent ovarian cancer that causes protracted and debilitating symptoms. Recognising variation in clinical practice and the unmet need for evidence-based treatment, I conducted a literature review to summarise current treatment strategies for MBO in women with advanced gynaecological cancers from a multidisciplinary perspective. A pilot interprofessional MBO program was developed by the MBO working group (which I co-led with Dr Stephanie Lheureux) and implemented in June 2016 at Princess Margaret Cancer Centre to support women who had, or were at risk, of developing MBO. The integrated model of care consisted of: i) standardised MBO symptom triage tools; ii) establishment of MBO multidisciplinary case conferences; iii) consensus on MBO care algorithms for in-patients and out-patients; iv) development of patient education materials for MBO; and v) prompt access to allied health professionals and supported advanced care planning. To assess the impact of the interprofessional MBO program, I reviewed all consecutive patients presenting with MBO from April 2014 to March 2018 (i.e. before and after the implementation of the program) and compared their outcomes. Of the 169 patients included, the majority (n=124, 73%) had recurrent ovarian cancer. There were 106 patients admitted prior to implementation of the MBO program (baseline group) whilst 63 patients were managed under the MBO program (MBO program group). Overall, the MBO program group had a significantly shorter average accumulated hospital length of stay (LOSsum) by 9 days (13 vs 22 days, adjusted P=0.006). Furthermore, their median overall survival post MBO diagnosis was approximately 5 months longer compared to the baseline group (243 vs 99 days, P=0.002). This retrospective, single institution study suggests a beneficial impact towards improving the complex care of women with advanced gynaecological cancers who developed MBO. Following on from this retrospective study, I developed a prospective MBO study incorporating patient reported outcomes to validate these findings, which is currently recruiting (MAMBO study, N=61/150 NCT03260647). In conclusion, the body of academic work carried out in this thesis has addressed known clinical gaps in ovarian cancer care throughout the disease trajectory and generated specific care recommendations to guide risk-reducing surgery management, to improve symptom burden whilst undergoing cancer treatment, and to improve management of malignant bowel obstruction. Broadly, this research will help clinicians, peak bodies and health funders implement evidence based care and institutional and national policies to facilitate better care provision for patients with ovarian cancer.
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ItemThe control of melanoma by the Hippo pathway( 2018)Melanoma is an aggressive cancer with extremely unfavourable prognosis. Two main types of melanoma include cutaneous melanoma (CM) accounting for around 95% and uveal melanoma (UM) around 5%. In Australia, melanoma is in the top five most commonly diagnosed cancers, estimated to contribute to over 10% of all new cancer diagnoses in 2017 (Cancer Australia, 2018.). While the overall death rate caused by all cancer is decreasing, the mortality of melanoma has increased in recent years (Howlader et al., 2012; AIHW, 2017). Patients diagnosed only with primary melanoma have relatively high survival rates, whereas when patients are diagnosed with metastatic melanoma, the survival rate is very low (Gershenwald et al., 2017). Currently, the mechanisms that drive melanoma progression and metastasis remain poorly understood; but better therapies are definitely required. BRAF mutations are most common in melanoma, occurring in around 50% of this disease (Akbani et al., 2015), which provides a possibility for targeted therapy. Indeed, the United States Food and Drug Administration (USFDA) has approved BRAF inhibitors (BRAFi) and MEK inhibitors (MEKi) as the standard treatment for metastatic melanoma patients harbouring BRAF mutations. However, drug resistance occurs in the majority of these patients within two years of treatment (Long et al., 2016). Therefore there is an urgent need to understand the mechanism of BRAFi and MEKi resistance, and find new therapeutic strategies for melanoma. One gene that has been linked to BRAFi resistance is the YAP, which is the key downstream effector of a pathway called the Hippo pathway. The Hippo pathway is an important regulator of organ growth in development. Deregulation of the Hippo pathway stimulates the activity of the YAP oncoprotein, which can cause several human cancers (Zanconato, Cordenonsi and Piccolo, 2016). However, the impacts of YAP deregulation in melanoma are not thoroughly understood. In this project, the roles of YAP in melanoma were examined. Firstly, the impacts of knockdown, overexpression, and activation of YAP on anchorage-independent growth of melanoma cells were assessed using soft agar assays. The results showed that either YAP activation or overexpression promotes colony formation, whilst YAP knockdown reduces this, suggesting potential influences of YAP on melanoma tumorigenesis. Secondly, the effects of YAP in melanoma invasion and metastasis were investigated. Melanoma cells stably expressing an active YAP mutant (YAP-5SA) have a greater invasive ability, as determined with transwell invasion assays. A spontaneous murine metastasis model was used to investigate the impact of YAP on metastasis. The results demonstrated that YAP-5SA promotes metastasis to multiple organs such as the lung and the liver; YAP-5SA enhances vascularity and necrosis of primary melanoma. Thirdly, mechanisms responsible for YAP-induced invasion were explored. Four potential target genes of YAP, derived from RNA-sequencing data, were found crucial, as well as the key YAP transcription factor partners, TEAD1-4. Finally, a lipid-lowering drug called simvastatin was found to kill melanoma cells and inhibits YAP activity in vitro. A post-translational modification, geranylgeranylation, was found to be essential in the statin-induced melanoma cell death and YAP inactivation; RhoA and other geranylgeranylated proteins might be important in these phenotypes. To conclude, this study explored the role of YAP in melanoma metastatic progression, and identified crucial transcription factors and target genes that mediate YAP-induced impacts on melanoma invasion. Additionally, inhibition of YAP and its mechanism in melanoma cells was preliminarily assessed using simvastatin. Understanding the molecular mechanism of melanoma metastasis and inhibition may help us establish more effective therapies for this disease.
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ItemInvestigating the requirements of pro-inflammatory signaling in skin and head and neck SCC( 2018)Head and neck squamous cell carcinoma (HNSCC) is a genetically heterogeneous cancer with poor prognosis. Current treatments for HNSCC are ineffective, and the resistance to therapies is often associated with a prominent inflammatory response highlighting the importance of devising ways to overcome it. Our laboratory has identified the Grainyhead-like 3 (GRHL3) gene as a potent tumor suppressor against HNSCC of both mice and humans. Loss of Grhl3 in mice induced HNSCC that appeared to be promoted by inflammation. In humans, we have introduced a paradigm shift in HNSCC pathogenesis through the identification of a miRNA-21-oncogenic network in patients, stratifying them into three subsets with distinct molecular signatures. This raised the hypotheses that inflammation may cooperate with the miR-21 oncogenic network to trigger human HNSCC and that different pro-inflammatory signaling might occur specifically in each HNSCC subset. In this study, we profiled pro-inflammatory cytokines/chemokines and their associated signaling pathways in 12 cell lines and xenografts by qPCR, Western Blot and immunohistochemistry, and correlated findings in cell lines with those in HNSCC mouse models as well as HNSCC patients. Our data determined that the expression of multiple cytokines and inflammatory proteins is dysregulated leading to the involvement of pivotal signaling such as the IL-1/NF-κB, the IL-6R/STAT3 and the TGF-β/SMAD pathways. We then modulated the pro-inflammatory signaling through different inhibitors, gene silencing and overexpression. The cell lines showed various sensitivities to the inhibitors of these inflammatory signaling, confirming the presence of distinct inflammatory profile in subsets of HNSCC. Interestingly, the antimicrobial peptides S100A8 and S100A9, which are involved in inflammation, were lost in all HNSCC cell lines in consistence with clinical data implicating them in the suppression of HNSCC. Thus, S100A8/A9 may function as tumor suppressors in HNSCC, and are currently being investigated to uncover the mechanisms that lead to their loss and to assess the downstream signaling of their epithelial RANGE and TRL4 receptors. Moreover, hotspot mutations were identified in common genes among the HNSCC cell lines, which showed different expression profiles of these mutant genes. Based on the pro-inflammatory signatures we have identified in human HNSCC lines, we are now able to stratify them into subsets with specific inflammatory pathways. Components of these pathways could serve as potential targets to overcome resistance in heterogeneous HNSCC. Inhibition of the miR-21 oncogenic network in combination with inhibitors of the inflammatory signaling while considering the mutational profiles may provide a better strategy to design new therapeutic applications in subtypes of HNSCC.
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ItemPrediction and assessment of pathological complete response following neoadjuvant chemoradiotherapy for locally advanced rectal cancer( 2017)Introduction The management of patients with rectal cancer who develop a pathological complete response (pCR) following neoadjuvant chemoradiotherapy (nCRT) presents an ongoing challenge to clinicians. Some authors have suggested that the presence of a clinical complete response may allow patients to be spared the morbidity and potential risks of surgery through adoption of a ‘watch and wait’ policy with surgery only in the setting of clinical failure. However clinical response and pathological response are not always wellcorrelated and widespread adoption of this regimen is limited by accurate methods to assess and confirm the presence of a pCR without a surgical specimen. Method A systematic review of the literature has been performed to identify methods to predict and assess a pathological complete response to nCRT. The first part of the literature review focuses on factors predictive of a pCR, specifically clinical features, radiological features and histological and molecular markers. The second part of the literature review aims to determine methods to accurately assess the presence of a pCR following neoadjuvant treatment. Following this an institutional database was interrogated to determine clinical and radiological features associated with prediction and assessment of a pCR and a multimodal predictive model has been developed. Molecular analysis has been performed to identify genetic influences on pCR. The role of radiological imaging in the assessment of pCR will be explored and the prognostic and clinical significance of metabolic response assessment by 18F FDG PET CT has been investigated in detail. Results Assessment Histology and clinical assessment remain the most effective methods of assessment of pCR with histology considered the gold standard. Clinical assessment is limited to low rectal tumours and is open to significant inter-rater variability while histological examination requires a surgical specimen for accurate assessment. Radiological assessment of pCR demonstrates the greatest potential for assessment of pCR without the need for surgery with diffusion weighted MRI and 18F FDG PET CT providing the greatest accuracy. It is likely that improved accuracy will be achieved with multimodal assessment of response combining the benefits of clinical, serological, endoscopic and radiological methods of response assessment. Prediction Clear methods to predict pCR prior to the commencement of therapy have not been defined. Clinical and radiological features of the primary cancer have limited ability to predict response. Molecular signatures hold the greatest potential to predict response however adoption of this technology is limited by poor concordance of biomarkers between cohorts. Conclusion Accurate prediction and determination of a complete pathological response is paramount if a non-operative approach is to be undertaken with confidence in oncological outcomes. A variety of methods are available but currently they lack sufficient sensitivity and specificity to define management. Despite a large volume of research the ability to predict which patients are likely to sustain a pCR and accurately assess those patient who have a pCR remains elusive. Further research into models incorporating both prediction and assessment into decision-making is required.
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ItemInvestigating the role of polarity protein, SCRIB, in haematopoiesis( 2017)The evolutionarily conserved scaffolding protein, Scribble (SCRIB), acts as a tumour suppressor in multiple epithelial cancers. However, SCRIB’s role in haematopoiesis and haematopoietic malignancies is largely unknown. As SCRIB knockout mice are embryonically lethal, we utilised conditional knockout mouse models driven by the Mx1 or hScl promoter in conjunction with extensive phenotypic analyses to elucidate SCRIB’s role in haematopoiesis. Our comprehensive analyses revealed loss of SCRIB produced subtle but significant defects in lymphoid and myeloid progenitor fractions although the specific fraction affected varied between the conditional knockout mouse models. As these two models have different kinetics we utilised a reverse transplant assay, with similar kinetics to the Mx1-Cre model, to examine the cell intrinsic effect of SCRIB loss in haematopoiesis. Similar to our previous results, this assay revealed a significant role for SCRIB in early lymphoid and myeloid development. The subtlety of phenotype produced by deletion of SCRIB is most likely due to compensatory mechanisms so we induced stress haematopoiesis through irradiation to mitigate the effect of compensatory mechanisms. Lethally irradiated recipients receiving SCRIB knockout bone marrow revealed a more severe phenotype compared to previous assays with defects in erythropoiesis, myelopoiesis and lymphopoiesis. Taken together, our data reveals a role for SCRIB in multiple haematopoietic lineages during steady-state haematopoiesis thereby suggesting SCRIB may be important during leukemogenesis. Studies are currently underway to investigate how SCRIB impacts on the onset and severity of acute myeloid leukaemia and acute lymphocytic leukaemia.
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ItemInvestigating prognostic and predictive tissue biomarkers in head and neck squamous cell carcinoma( 2017)Head and neck squamous cell carcinoma (HNSCC) comprises a diverse group of cancers that arise from a number of subsites of the upper aerodigestive tract, including the oropharynx, oral cavity, larynx and hypopharynx. These cancers have traditionally been linked to tobacco and alcohol use (Gillison et al 2008; Goon et al 2009) and despite improvements in treatment, the outcome for patients with locally advanced HNSCC remains poor. Current treatments are associated with significant acute and late toxicity which can have a significant long term negative impact on function and quality of life. Current tumor staging methods and biomarkers are limited in their capacity to consistently distinguish groups with different outcomes, and to permit tailoring of therapy based on prognosis and biological features. Furthermore, it is recognised that there are significant clinical differences between the different subsites of head and neck cancer, warranting molecular studies focused on individual sites. Thus, to improve patient outcomes, it is becoming increasing important to identify novel biomarkers of prognosis and response to therapy which will empower clinicians with better patient selection strategies for risk-adapted treatments and emerging molecular therapies. It is now accepted that a significant proportion of oropharyngeal cancers, are caused by infection with human papilloma virus (HPV) (Fakhry et al 2008; Ang et al 2010). HPV positive oropharyngeal cancer is known to differ from HPV negative epidemiologically, clinically and molecularly and most importantly, HPV positive status is associated with a greatly improved prognosis (Fakhry et al 2008; Ang et al 2010). The involvement and importance of HPV in non-oropharyngeal HNSCC sites however remains unclear. Other than HPV, which is often determined diagnostically via p16INK4A immunohistochemical staining (an accepted surrogate biomarker in oropharyngeal cancer), there are no clinically useful prognostic or predictive biomarkers in HNSCC. The identification of relevant biomarkers, which can be easily assayed in a diagnostic setting, utilising readily accessible formalin-fixed, paraffin-embedded (FFPE) tissue blocks, is critical to improving patient outcomes. Such assays include immunohistochemistry (IHC) to look at protein expression and fluorescence in situ hybridisation (FISH) for the study of gene copy number. This thesis comprises five published peer reviewed journal articles containing research investigating the role of HPV/p16INK4A in head and neck cancer; both establishing the role of HPV/p16INK4A in oropharyngeal cancer, as well as work demonstrating that the role of HPV in non-oropharyngeal HNSCC subsites including the oral tongue and larynx is not as clear or important as oropharyngeal cancer. Further, I present work investigating several putative predictive biomarkers and their potential roles in providing clinically useful information for potential patient stratification. All of these studies utilised several large unique HNSCC patient cohorts comprising FFPE tissue blocks and comprehensively annotated clinicopathological and outcome data.
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ItemThe role of Pim-1 in breast cancer metastasis( 2017)Breast cancer is the most common cancer in women. Despite advances in treatment options, the spread of breast cancer to distant organs (metastasis) remains the major cause of morbidity and mortality in breast cancer patients. This is attributed primarily to the impairment of function in affected organs. Thus, there remains a vital need for better-targeted treatments that more effectively inhibit the development or progression of metastases. Pim-1 is a serine/threonine survival kinase that has been implicated in the development of metastasis in several haematological and solid cancers. However, little is known about its role in breast cancer. In our laboratory, we previously identified Pim-1 as upregulated in brain metastatic 4T1Br4 syngeneic mouse cells and tumours compared to parental 4T1 cells. This led us to propose that Pim-1 may play a role in mediating breast cancer brain metastasis. Therefore, the overall objective of this project was to examine the expression and functional role of Pim-1 in breast cancer metastasis, with a focus on organ-specific metastasis. We interrogated public databases to show that Pim-1 expression is low to absent in normal breast tissue and increased in breast tumour tissue. Furthermore we show that the murine (4T1Br4) and human (MDA-MB-231Br) brain metastatic breast cancer cell lines and tumours demonstrate the highest expression of Pim-1 mRNA and protein. To investigate the function of Pim-1 in breast cancer metastasis we tested the impact of inhibiting Pim-1, either by gene knock down using short hairpin RNAs or the pharmacological inhibitor SGI-1776, on the ability of 4T1Br4 and MDA-MB-231Br cells to migrate and invade in vitro. 4T1Br4 cells displayed increased migration and invasion propensity after Pim-1 knock down and this was coupled with a decrease in β4 integrin expression. Conversely, MDA-MB-231Br cells showed a decreased ability to migrate and invade after Pim-1 KD, as well as decreased cell surface expression of β1 and β3 integrins. Treatment with SGI-1776 dose-dependently decreased the ability of both 4T1Br4 and MDA-MB-231Br cells to migrate and invade, decreased cell surface expression of β3 integrin in 4T1Br4 cells, and both β1 and β3 integrins in MDA-MB-231Br cells. To examine the effect of Pim-1 inhibition in vivo, we assessed the metastatic spread of Pim-1 knock down MDA-MB-231Br cells in an experimental metastasis assay. After intracardiac injection of Pim-1 knock down cells, we observed a reduction in the number of circulating tumour cells and decreased bone metastasis, indicating a functional role for Pim-1 in breast cancer metastasis to the bone. Data from brain metastasis in this model were inconclusive. In summary, results from this project highlight the importance of Pim-1 in breast cancer metastasis and provide evidence that Pim-1 contributes to the migration and invasion of breast cancer cells both in vitro and in vivo, possibly via regulation of integrin expression, and indicate that Pim-1 is a relevant therapeutic target for the treatment of metastatic breast cancer.
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ItemNo Preview AvailableBioimaging in colorectal cancer - prediction of response to neoadjuvant treatment( 2015)Over the last decade the management of colorectal cancer has changed significantly with the benefits of neoadjuvant therapies and new adjuvant treatments becoming apparent. Surgical strategies have also evolved with initial evidence that some patients can be successfully managed with local excision or omission of any surgery at all, resulting in a shift towards the individualisation of cancer management. The management of rectal cancer is based on primary staging assessment which relies on imaging techniques such as CT, MRI and ERUS. Recent advances in technology have improved the accuracy and widened the applications of these techniques. With the progress in medical and surgical treatments for rectal cancer, the optimal management of rectal cancer has become more complex. The evolving ability to tailor optimal treatment to the individual has created new roles for imaging such as prediction of response to treatment, restaging with assessment of response to treatment and prediction of prognosis. Consequently, prediction of response will become an important component of modern pre-operative assessment of rectal cancer to optimise individualisation of medical and surgical treatment. Beyond the established role of primary staging of malignancies, the role of conventional imaging techniques in re-staging following neoadjuvant treatment may be of increasing importance. Novel functional imaging techniques such as FDG-PET, DW (diffusion weighted) MRI are also emerging, the roles of which are yet to be determined. This thesis will examine the current status of bio-imaging and explore new imaging techniques in rectal cancer. At the Peter MacCallum Cancer Centre, we have been routinely performing staging and restaging imaging with CT, MRI and PET for the last 5 years which has resulted in a cohort of patients in whom these imaging techniques can be evaluated. This thesis also aims to evaluate a recent and evolving functional imaging technique- DW-MRI, in the prediction of response of rectal cancer to chemo-radiation.
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ItemInvestigating mechanisms of metastasis in melanoma( 2016)Metastasis is a complex process that is responsible for most human cancer deaths. Autopsy findings across multiple cancers suggest that metastatic dissemination from the primary site of disease to distant organs is not a random process; cancers can have different predilections to metastasize to particular organs. These observations raise the general question of whether determinants of metastasis, including organ-specificity, are driven by cancer cell-intrinsic or cell-extrinsic factors, or a combination of both. A fundamental question in cancer biology is whether metastasis capability in human tumours is acquired in a heritable manner. Work pertaining to this thesis tested whether organ-specificity during melanoma metastasis is a biologically heritable trait, using PDX modelling. Collectively, these studies suggest that while metastatic potential per se is a biologically heritable trait, organ-specificity of metastasis is not. To examine a candidate cell-intrinsic regulator of melanoma metastasis, desmoglein 2 (DSG2), expression and correlative studies were also performed on patient melanomas. DSG2, a member of the cadherin class of proteins that mediate cell-cell contacts, has been previously but inconsistently detected in human melanoma, however its role and function remain poorly defined. Herein, DSG2 expression was investigated as a potential prognostic factor in melanoma linked to the development of vasculogenic mimicry and poor patient outcomes. These studies confirm that DSG2 is expressed in primary and metastatic melanomas, but not in normal cutaneous melanocytes, and is associated with poor survival in melanoma. Although DSG2-positive melanomas consistently contained more features of VM than DSG2-negative, the differences were not statistically significant.
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ItemCooperative tumourigenesis : analysis of novel tumour suppressors in ras oncogene driven epithelial tumours( 2015)Cancer is a cooperative process, involving mutations in multiple genes. Activation of a cancer-driving gene, the Ras small GTPase, via a mutation that locks Ras in the GTP-bound active form (RasV12), occurs in ~30% of human cancers. However, alone it is not sufficient for tumour formation. A loss of function screen previously performed in the vinegar fly, Drosophila melanogaster, identified 947 genes that potentiate RasV12-mediated tumourigenesis and metastasis (Zoranovic, et al. in prep.). This list has been narrowed down to 234 genes that 1) show increased tumourigenicity with RasV12 in vivo, 2) are in the top 100 genes down-regulated in human cancer, and 3) are known to regulate the cytoskeleton, polarity, adhesion or cell motility. This study has successfully confirmed involvement of autophagy-related genes Atg8a, Atg7 in regulating RasV12-mediated proliferation in the Drosophila eye epithelial tissue using the UAS/GAL4 system. The study identified the autophagy-related genes Atg1, Atg3, Atg4, Atg5, Atg6, Atg7, Atg8a, Atg12 and Atg101 that when knocked down cooperate with RasV12 and lead to increased tissue overgrowth in the Drosophila eye epithelium. Atg8a was chosen as the representative target gene to investigate this cooperation. It was observed that Atg8a cooperates with RasV12 through the Raf pathway. The role of p62 in this Ras-mediated cooperation with Atg8a was also examined and it was found that p62 levels increase in RasV12+ Atg8aRNAi expressing tissue in comparison with control. Investigations were also carried out to ascertain if knockdown of Atg genes cooperate with Ras through the JNK pathway. It was discovered that in the presence of oncogenic Ras, knock down of Atg8a increases the expression of the JNK target MMP1. The finding of this work could lead to use of this autophagy related genes as prognostic markers in Ras-driven oncogenesis and might reveal effective therapeutic targets to combat this deadly disease.