Introduction: Little is known about the aetiology of cancer in teenagers and young adults (TYA) aged 15-24 years, although in England, cancer is the most common cause of disease-related mortality in this age group. The most common cancers at this age are lymphomas, central nervous system (CNS) tumours and germ cell tumours (GCT). The commonest carcinomas seen at older ages including lung, breast, large bowel and prostate account for only 3-4% of TYA cancers. In this thesis I describe the incidence patterns of selected cancers in TYA and the variation seen with geography, time and in population subgroups. The focus is on CNS tumours, GCT and bone tumours as they either peak in incidence in TYA and/or contribute disproportionately to cancer related mortality in TYA. This will allow formulation of hypotheses regarding aetiology of cancer in this age group which can then be tested by further research. Methods: For the majority of the analysis, anonymised national cancer registration data from England on individual patients of all ages with newly diagnosed cancer between 1979 and 2003 were used. To contrast the incidence patterns in England with that of India, data from five Indian urban population based cancer registries were used for part of the analysis. Age, sex, site and histology specific incidence rates were calculated and expressed per million person years. All rates, where appropriate, were adjusted to the world standard population using direct methods. To explore the link of growth with development of osteosarcoma and Ewing sarcoma, a random-effects meta-analysis was undertaken on studies which investigated an association of these tumours with height at diagnosis. Results: The incidence of cancer in TYA overall in England exceeded that of India. This was also true for most individual sites including epithelial cancers of lung, colon/rectum, breast, ovary and cervix, and non-epithelial cancers including melanoma, Hodgkin lymphoma and testicular cancer. Notable exceptions to this pattern were cancers of the mouth, gall bladder and stomach (females only) where incidence was higher in India. In England, CNS tumours in TYA were a composite of pilocytic astrocytomas and embryonal tumours (representing tail end of childhood CNS tumours), pituitary tumours, nerve sheath tumours, high grade astrocytomas and meningiomas (representing early-onset of CNS tumours that peak in incidence in the 6th and 7th decade of life), and of CNS GCTs, pleomorphic xanthoastrocytomas and neurocytomas which show a peak incidence in TYA. Irrespective of site or histology, GCT in England showed a peak in incidence between ages of 10 to 39 years which was more marked in males. This however varied by site and the peak incidence was seen at 10 to 14 years in the CNS, 15 to 19 years in ovary, 25 to 29 in mediastinum & thorax and abdomen & pelvis, and 30 to 34 years in testicular tumours. Osteosarcoma and Ewing sarcoma were the predominant bone tumours in TYA in England and showed a distinct peak of incidence at 10 to 14 years age in females and a larger peak at 15 to 19 years age in males. The peak incidence of osteosarcoma of long bones of the lower limb was six times more than that at any other site while the peak incidence of Ewing sarcomas located in the bones of the central axis exceeded those in long bones of the lower limb. The average height of patients with osteosarcoma at diagnosis was found to be significantly above the average height of the reference population, at the 95% level. The association of greater height at diagnosis with Ewing sarcoma was also significant at the 95% level but much weaker. Conclusion: In this thesis I have explored the epidemiology of cancer in TYA using some of the established methodologies which have previously been used in advancing our knowledge of childhood and older adult cancers. These studies provide some clues to aetiology. Variation in environmental exposures and lifestyle factors between England and India can explain the majority of the differences in incidence patterns observed. Genetic predisposition to cancer along with carcinogen exposure could lead to early onset of some cancers generally seen in older adults. Regardless of site, the similarity in age-incidence patterns of GCT, suggests a common initiation of these tumours in embryonic/foetal life with variable rates of tumour progression as a result of local factors or events during postnatal and pubertal period. The incidence patterns of osteosarcoma along with the strong and consistent association with a greater height at diagnosis indicate that bone growth is important in the development of this tumour while different biological pathways which may be unrelated to growth could also be relevant for Ewing sarcoma.

No description available.

The effectiveness of radiotherapy treatment could be significantly improved if tumour cells could be rendered more sensitive to ionising radiation without altering the sensitivity of normal tissues. However, many of the key mechanisms that determine intrinsic tumour radiosensitivity are largely unknown. This thesis is concerned with the identification of novel determinants of tumour radiosensitivity. A siRNA screen of 200 genes involved in DNA damage repair was conducted using γH2AX foci post-irradiation as a marker of cell damage. This screen identified POLQ as a potential tumour-specific contributor to radioresistance. Subsequent investigations demonstrated that POLQ knockdown resulted in radiosensitisation of a panel of tumour cell lines, whilst having little or no effect on normal tissue cell lines. It was subsequently shown that POLQ depletion rendered tumour cells significantly more sensitive to several classes of cytotoxic agents. Following exposure to etoposide, it was found that tumour cells depleted of POLQ had reduced RAD51 foci formation, suggesting that POLQ is involved in homologous recombination. A homologous recombination assay was used to confirm that POLQ depletion does indeed result in reduced homologous recombination efficiency. These findings led to the investigation of the clinical significance of tumour overexpression of POLQ. The clinical outcomes of patients with early breast cancer were correlated with tumour expression levels of POLQ. It was found that POLQ overexpression was correlated with ER negative disease and high tumour grade, both of which are associated with poor clinical outcomes. POLQ overexpression was associated with extremely poor relapse free survival rates, independently of any other clinical or pathological feature. The mechanism that causes this adverse outcome may in part arise from resistance to adjuvant chemotherapy and radiotherapy treatment. These findings, combined with the limited normal tissue expression of POLQ, make it an appealing target for possible clinical exploitation.

This thesis considers aspects of modelling solid tumours. We begin by considering the common assumption that nutrient or drug concentrations in avascular tumour spheroids are radially symmetric. We derive a simple Poisson equation for biomolecular diffusion into an avascular tumour, but with highly oscillatory boundary conditions due to the surrounding capillary network. We find that the assumption of radial symmetry is legitimate for biomolecules that are taken up in sufficient quantities by proliferating cancer cells; however radially symmetric profiles need not be observed otherwise. We then investigate how the gap between an avascular tumour and the neighbouring vasculature varies as the tumour grows. This is explored by (i) using scaling arguments based on ordinary differential equations, (ii) coupling the rate of oxygen flux from the vasculature to oxygen evolution within the tumour, and (iii) deriving a system of six coupled non-linear partial differential equations modelling the tumour evolution. It is found that as the tumour grows any initial gap between the tumour and neighbouring vasculature closes since there is no mechanism which would sufficiently up-regulate non-cancerous cell proliferation. This is in contrast to the intra-cornea implantation observations, upon which several mathematical models are based. Finally, we study the growth and treatment of a vascular tumour subjected to chemotherapies, particularly when the therapies can exhibit an anti-angiogenic effect and resistance to the therapy is incorporated. A multi-compartment model is derived for the evolution of a tumour undergoing treatment and parameters are estimated, with extensions to incorporate numerous different therapy protocols in the literature. We find that anti-angiogens can be effective, though the appropriate scheduling is counter-intuative and contradicts many standard therapy rules. We conclude that chemotherapy protocol design is very sensitive to the mode of action of the drug and simple general strategies will, in many cases, not be the most effective.

The adaptive immune response forms an essential part of the cancer immuno-editing process, whereby nascent malignant cells are detected and destroyed prior to forming tumours. The process is tightly controlled to minimise collateral damage to healthy tissue. One of the mechanisms evolved for this purpose and frequently co-opted by malignant cells is the creation of a microenvironment scarce in essential amino-acids through the use of catabolic enzymes such as Indoleamine 2,3-dioxygenase (IDO) , responsible for the rate-limiting step in tryptophan catabolism. The evolutionary conserved GCN2 and mTORC1 pathways respond to amino-acid starvation by triggering emergency homeostatic response programmes that aim to conserve nutrients by shutting down biosynthetic pathways, slowing cell cycle progression and facilitating autophagy. This research project focuses on elucidating the interaction between IDO activity and these pathways and its implications for the immune-editing process. The role of the mTOR kinase as a regulator of T cell fate following exposure to cognate antigen has recently become apparent. Experiments described herein confirm that in murine and human models of T cell activation exposure to tryptophan starvation results in significant mTORC1 inhibition and a modified phenotype with reduced Tbet expression, altered cytokine secretion profile, greatly impaired proliferative capability and expanded CD4⁺ FoxP3⁺ CD25^high subpopulations. Additional results confirmed that the action of IDO is sufficient to deplete tryptophan from the microenvironment to levels sufficient to depress the mTORC1 axis and trigger GCN2 activity even in tumour cell lines. Lower extracellular tryptophan levels were necessary to perturb these pathways In IDO expressing cell lines, suggesting that compensatory mechanisms allow continued proliferation of malignant cells in the face of conditions that severely impede an anti-cancer immune response. In conclusion, manipulation of the mTORC1 axis via IDO-induced tryptophan depletion is an important tumour immune-escape mechanism that can be a target for cancer immunotherapies.

Os tumores odontogênicos são um grupo heterogéneo de lesões formadas a partir de tecidos que dão origem ao dente. A metilação do ADN, uma adição covalente de um grupo metilo na posição 5 de carbono de um nucleótideo de citosina, é considerado um importante regulador da expressão génica. A adição do radical metil é catalisada por ADN metiltransferases (DNMTs). Embora alguns estudos epigenéticos tenham sido realizados em tumores odontogênicos, um estudo com os três tipos de DNMTs em vários membros desse grupo está em falta. Este estudo analisa a expressão de DNMTs em tumores odontogênicos. Amostras de vinte ameloblastomas, dez Calcificante tumores odontogênicos císticos, dez calcificados tumores epiteliais, dez tumor odontogênico adenomatóide, dez tumores odontogênicos queratocísticos, quatro fibromas ameloblásticos, dois fibro-odontoma ameloblástico, quatro fibroma centrais odontogênicos, sete tecidos de fibromas odontogênicos periféricos e dez mixomas odontogênicos foram incluídos. DNMT1, 3A e 3B foram expressas no núcleo e / ou citoplasma de todos os tumores odontogênicos. A alta expressão de DNMTs em células de tumor odontogênico sugere metilação como um mecanismo importante para este grupo de tumores. / Odontogenic tumours are a heterogeneous group of lesions formed from tissues that give rise to the tooth. DNA methylation, a covalent addition of a methyl group to the 5-carbon position of a cytosine nucleotide, is considered an important regulator of gene expression. The addition of the methyl radical is catalyzed by DNA methyltransferases (DNMTs). Although some epigenetic studies have been conducted in odontogenic tumours, a study with the three types of DNMTs in several different members of this group is missing. This study analyzes the expression of DNMTs in odontogenic tumours. Formalin-fixed and paraffin-embedded tissue samples of twenty ameloblastomas, ten calcifying cystic odontogenic tumors, ten calcifying epithelial tumors, ten adenomatoid odontogenic tumors, ten keratocystic odontogenic tumors, five ameloblastic fibromas, two ameloblastic fibro-odontoma, four central odontogenic fibroma, seven peripheral odontogenic fibroma and ten odontogenic mixoma were included. DNMT1, 3A and 3B were expressed in the nucleus and/or cytoplasm of all odontogenic tumours. The high expression of DNMTs in odontogenic tumour cells suggests methylation as an important mechanism for this group of tumours.

Os tumores odontogênicos são um grupo heterogéneo de lesões formadas a partir de tecidos que dão origem ao dente. A metilação do ADN, uma adição covalente de um grupo metilo na posição 5 de carbono de um nucleótideo de citosina, é considerado um importante regulador da expressão génica. A adição do radical metil é catalisada por ADN metiltransferases (DNMTs). Embora alguns estudos epigenéticos tenham sido realizados em tumores odontogênicos, um estudo com os três tipos de DNMTs em vários membros desse grupo está em falta. Este estudo analisa a expressão de DNMTs em tumores odontogênicos. Amostras de vinte ameloblastomas, dez Calcificante tumores odontogênicos císticos, dez calcificados tumores epiteliais, dez tumor odontogênico adenomatóide, dez tumores odontogênicos queratocísticos, quatro fibromas ameloblásticos, dois fibro-odontoma ameloblástico, quatro fibroma centrais odontogênicos, sete tecidos de fibromas odontogênicos periféricos e dez mixomas odontogênicos foram incluídos. DNMT1, 3A e 3B foram expressas no núcleo e / ou citoplasma de todos os tumores odontogênicos. A alta expressão de DNMTs em células de tumor odontogênico sugere metilação como um mecanismo importante para este grupo de tumores. / Odontogenic tumours are a heterogeneous group of lesions formed from tissues that give rise to the tooth. DNA methylation, a covalent addition of a methyl group to the 5-carbon position of a cytosine nucleotide, is considered an important regulator of gene expression. The addition of the methyl radical is catalyzed by DNA methyltransferases (DNMTs). Although some epigenetic studies have been conducted in odontogenic tumours, a study with the three types of DNMTs in several different members of this group is missing. This study analyzes the expression of DNMTs in odontogenic tumours. Formalin-fixed and paraffin-embedded tissue samples of twenty ameloblastomas, ten calcifying cystic odontogenic tumors, ten calcifying epithelial tumors, ten adenomatoid odontogenic tumors, ten keratocystic odontogenic tumors, five ameloblastic fibromas, two ameloblastic fibro-odontoma, four central odontogenic fibroma, seven peripheral odontogenic fibroma and ten odontogenic mixoma were included. DNMT1, 3A and 3B were expressed in the nucleus and/or cytoplasm of all odontogenic tumours. The high expression of DNMTs in odontogenic tumour cells suggests methylation as an important mechanism for this group of tumours.

Migration Stimulating Factor (MSF) is an oncofoetal protein which is constitutively produced by both epithelial and stromal cells during foetal development, not expressed by the majority of their normal adult counterparts, but re-expressed during pathological processes such as cancer and wound healing. Scotland has the highest occurrence of oral cancers in the UK; the incidence is still increasing, but patient survival remains very poor. The expression of MSF in oral tumours has not been previously reported. The aims of this study were: • To determine the effects of MSF on the migration of oral tumour cell lines and normal stromal cells in culture (chapter 3), • To ascertain the possible presence, diagnostic and prognostic value of MSF in oral squamous cell carcinoma (OSCC; chapter 4), and salivary gland tumours (SGT; chapter 5). • To identify the putative MSF receptors in oral tumour cell lines (chapter 6). For tissue culture studies, the effects of rhMSF (wild type and mutant proteins) were examined on human cell lines TYS, HSG, Endo 742 and FSF44. These cells were derived from OSCC, SGT, microvascular endothelial cells and skin fibroblasts, respectively. For ex-vivo studies, paraffin embedded archival specimens of OSCC and SGT were stained with specific MSF antibodies and the level of staining was assessed by consensus of 2-4 independent observers. The association between MSF expression and patient survival was determined by Kaplan-Meier and log-rank tests. Results presented in this thesis indicate that TYS and HSG cells secrete bioactive MSF in culture. rhMSF stimulated the migration of these tumour cells. The use of mutant proteins demonstrated marked differences among the cells examined: Five bioactive motifs (4x IGD and 1x HEEGH) were required for MSF bioactivity on TYS and HSG cells, whereas only one of these motifs was required for Endo 742 and two for FSF44. MSF+aa and MSF-aa showed the same migration-stimulating activity, but differ in their interaction with the MSF-inhibitor Neutrophil Gelatinase-Asscciated Lipocalin (NGAL). NGAL was shown to bind to and inhibit MSF+aa, but not MSF-aa. The bioactivity of MSF+aa and MSF-aa was inhibited by Insulin-like Growth Factor Binding Protein-7 (IGFBP7), MSF-function-neutralising antibody and antibody to the integrin avß3. This integrin was identified in the cell membrane material bound to MSF, suggesting that avß3 is a receptor for MSF.

Purpose: To examine the social competence of childhood brain tumour survivors in the context of a group social skills intervention program developed to address documented social deficits among this population and to expand outcomes obtained from a feasibility study, by: conceptualizing social competence as three separate but interrelated constructs including social adjustment, social performance, and social skills; incorporating a control group; eliciting teacher responses; and examining sense of self. Methods: Participants were 23 survivors (10 males; 13 females) aged 7 to 15 years and comprised an intervention (n=15) and control group (n=8). The intervention consisted of 8 2-hour weekly sessions focused on social skills including friendship making. At the level of social adjustment, intervention participants, controls, parents, and teachers (n=6) completed standardized measures of social adjustment including: social skills (SSRS, Gresham & Elliott, 1990); social functioning (Varni, 1999); and social problems (Achenbach, 2001). At the level of social performance, behavioural observations were conducted on intervention participants. At the level of social skills, intervention participants responded to the Social Problem-Solving Measure (SPSM; Vannatta, 1993). Survivors also completed standardized sense of self measures. Results: Outcomes related to social adjustment showed a significant increase from Time 1 to Time 2 for parent reported SSRS within and between groups. Significant improvements were also found for parent reported social problems between groups. Child reported social problems decreased within groups and a borderline effect was found between groups. Teachers reported improved SSRS scores form Time 1 to Time 2. For social performance, significant increases in frequency were found for maintaining facial attention and social conversations with peers over the course of the intervention. At the level of social skills, a borderline significant increase was found for quantity of strategies offered from Time 1 to Time 2. No significant findings were found for sense of self data. Conclusions: Improvements after intervention were noted at each level of social competence, but primarily at the level of social adjustment. Control group and teacher outcomes strengthen findings. This is the first study to explore varying levels of social competence and provides important insight into the source of survivors’ social deficits.

Purpose: To examine the social competence of childhood brain tumour survivors in the context of a group social skills intervention program developed to address documented social deficits among this population and to expand outcomes obtained from a feasibility study, by: conceptualizing social competence as three separate but interrelated constructs including social adjustment, social performance, and social skills; incorporating a control group; eliciting teacher responses; and examining sense of self. Methods: Participants were 23 survivors (10 males; 13 females) aged 7 to 15 years and comprised an intervention (n=15) and control group (n=8). The intervention consisted of 8 2-hour weekly sessions focused on social skills including friendship making. At the level of social adjustment, intervention participants, controls, parents, and teachers (n=6) completed standardized measures of social adjustment including: social skills (SSRS, Gresham & Elliott, 1990); social functioning (Varni, 1999); and social problems (Achenbach, 2001). At the level of social performance, behavioural observations were conducted on intervention participants. At the level of social skills, intervention participants responded to the Social Problem-Solving Measure (SPSM; Vannatta, 1993). Survivors also completed standardized sense of self measures. Results: Outcomes related to social adjustment showed a significant increase from Time 1 to Time 2 for parent reported SSRS within and between groups. Significant improvements were also found for parent reported social problems between groups. Child reported social problems decreased within groups and a borderline effect was found between groups. Teachers reported improved SSRS scores form Time 1 to Time 2. For social performance, significant increases in frequency were found for maintaining facial attention and social conversations with peers over the course of the intervention. At the level of social skills, a borderline significant increase was found for quantity of strategies offered from Time 1 to Time 2. No significant findings were found for sense of self data. Conclusions: Improvements after intervention were noted at each level of social competence, but primarily at the level of social adjustment. Control group and teacher outcomes strengthen findings. This is the first study to explore varying levels of social competence and provides important insight into the source of survivors’ social deficits.