published_or_final_version / Anatomy / Master / Master of Philosophy

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

Expression of A6 integrin, a laminin receptor, on tumor cell surfaces is associated with reduced patient survival and increased metastasis in a variety of tumors. In prostate cancer, tumor extra capsular escape occurs in part via laminin coated nerves and vascular dissemination, resulting in clinically significant bone metastases. Our group previously identified a novel form of A6 integrin, called A6p, generated by urokinase (uPA) dependent cleavage of the laminin binding domain from the tumor cell surface. Although functional consequences of cleavage have been characterized, little is known about how this process is regulated.Regulation of uPA mediated cleavage was identified by a laterally interacting protein expressed on the cellular surface. A direct interaction between the urokinase receptor (uPAR) and A6 integrin was characterized. This direct interaction was responsible for the extracellular cleavage of A6. Transient knockout of A3 integrin, a known interacting partner of uPAR, increased uPAR association with A6 integrin and enhanced production of A6p. Analysis of tissue obtained from human prostate tumors confirmed uPAR and A6 integrin expression in invasive disease. Taken together the results demonstrate a novel and dynamic role for uPAR regulation of integrin dependent adhesion through lateral interaction.Using the known conformation sensitivity of integrin function to I determined if engagement of the extracellular domain by antibodies inhibited integrin cleavage and the extravasation step of metastasis. Both endogenous and inducible levels of A6p were inhibited by engaging the extracellular domain of A6 with monoclonal antibody J8H. J8H inhibited tumor cell invasion through Matrigel. A SCID mouse model of extravasation and bone metastasis produced detectable, progressive osteolytic lesions within three weeks of intracardiac injections. Injection of tumor cells, pre-treated with J8H, delayed the appearance of metastases. Validation of the A6 cleavage effect on extravasation was confirmed through a genetic approach using tumor cells transfected with uncleavable A6 integrin. Uncleavable A6 integrin significantly delayed the onset and progression of osseous metastases out to 6 weeks post injection. The results suggest that A6 integrin cleavage permits extravasation of human prostate cancer cells from circulation to bone and can be manipulated to prevent metastasis.

Introduction: This dissertation seeks to identify novel, potentially modifiable risk factors that could be used to reduce the risk of prostate cancer (PCa) progression. Aim 1 investigates the effects of obesity and smoking on PCa progression, aim 2 studies the effects of specific medication use on PCa progression, and aim 3 identifies factors associated with faster PCa progression.Methods: Data from 140 subjects from the Watchful Waiting study followed every 3 months for up to 5 years were used. Multiple linear regressions were used to determine associations with baseline PSA. PSA velocity (rate of change of PSA over time) was used as a surrogate marker for PCa progression. Mixed effect models were used to assess the effect of obesity, smoking and medication use on PSA velocity(aim1 and 2). For aim 3, subjects were categorized as slow, intermediate and fast progressors based on tertiles of PSA velocity. In addition to the above variables, age, Gleason score, chromogranin-A, family history, selenium and free PSA were investigated as determinants of faster PCa progression using multiple logistic regressions. Analyses were run using two models, comparing slow progressors to fast progressors (model1) and slow progressors to a combination of fast and intermediate progressors (model2).Results: Aspirin use was negatively associated with baseline PSA (coefficient = -0.39 and 95% confidence interval (CI):-0.612, -0.158). Aspirin effect was statistically significant in never smokers (coefficient = -0.54, 95% CI: -0.916, -0.170) but not in ever smokers (coefficient = -0.22, 95% CI: -0.505, 0.065). Ever smoking was statistically significantly associated with higher PSA velocity compared to never smoking (coefficient = -0.001, 95% CI: 0.0002, 0.002). In aim 3, pack-years of smoking were positively associated whereas aspirin use was negatively associated with high PSA velocity in both models. Odds Ratio and 95% CI for smoking and aspirin use for model1 and 2 respectively; 1.03 (0.92, 1.13), 1.02 (1.00, 1.03), 0.24(0.06, 0.94) and 0.26(0.10, 0.68).Conclusions: Although more studies are needed before recommendations can be made, if these results are borne to be true in other studies these modifiable risk factors can be potentially be used in prevention of PCa progression.

Using the computer code Monte Carlo N-Particle (MCNP), doses were calculated for organs of interest such as the large intestine, urinary bladder, testes, and kidneys while patients were undergoing prostate brachytherapy. This research is important because the doses delivered to the prostate are extremely high and the organs near the prostate are potentially at risk for receiving high doses of radiation, leading to increased probabilities of adverse health effects such as cancer. In this research, two MCNP version 4C codes were used to calculate the imparted energies to the organs of interest delivered by 125I and 103Pd. As expected, the organs nearest to the prostate received the highest energy depositions and the organs farthest from the prostate received the lowest energy depositions. Once the energy depositions were calculated, the doses to the organs were calculated using the known volumes and densities of the organs. Finally, the doses to the organs over an infinite time period were calculated.

Prior research has suggested that life style factors, such as diet and physical activity, influence prostate cancer (PCa) progression. Metformin intake has been shown to be associated with decreased cancer risk in type II diabetic patients. We hypothesize that a low carbohydrate diet, prolonged aerobic exercise and metformin treatment can all independently slow prostate tumor development and a combination regimen will have an additive benefit. We used LNCaP xenografts to test this hypothesis. Results revealed that a diet low in carbohydrate reduced food consumption and a combination with exercise significantly reduced animal body weights. Ten weeks of metformin did not significantly alter tumor growth rate compared to control animals. Ten weeks of exercise significantly inhibited tumor growth. Out results suggest that dietary carbohydrate alteration or the administration of metformin alone cannot significantly influence prostate tumor progression. A suitable sustained exercise regimen may offer a more protective effect against PCa progression.

Introduction Prostate cancer (PCa) is the most commonly diagnosed male malignancy and the second leading cause of male cancer death in the Western world. In the United States of America (USA), African American men (AAM) have among the highest rates of PCa in the world. They develop the disease 1.5 times more frequently than European American men (EAM) of the same age .The mortality rate is approximately two to three times higher for AAM compared to EAM. There is a dearth of literature exploring the incidence and treatment outcomes of this disease based on racial profiling in a South African population. This study aims to evaluate racial disparities with a focus on patients with PCa managed in the public health care sector in the province of Kwazulu Natal (KZN). Patients and methods The study was a retrospective analysis of patients with PCa treated at Inkosi Albert Luthuli Central Hospital and Addington Hospital, which are both based in the Durban Metropolitan area in the province of KZN. Data extracted from the folders of patients with PCa who presented between March 2003 and December 2007 were collated onto a data capture form and analysed. Patient data were analysed according to the following categories: „h Patient demographics; „h Patient follow-up period; „h Disease risk profile; „h Response to treatment; „h Compliance on treatment. SPSS version 15.0 was used to analyse the data. Within each disease category, the response variables were analysed by race group using non-parametric Kruskal-Wallis tests. Multiple comparisons were made using pairwise Mann-Whitney tests and Bonferroni adjusted significance levels according to the number of multiple comparisons made. In order to control for other confounding factors such as age, serum PSA levels and compliance, Cox proportional hazards models were used. Hazard ratios and 95% confidence intervals were also reported. Results In KZN, the majority of the population is classified as blacks (82.9%). The Indian population group makes up 9.0% of the provincial population while white and coloured people make up 6.1% and 2.0% of the provincial population respectively. In this study population, Blacks made up 57.7% and whites made up 27.5%, followed by 11.4% of Indians and 3.4% of coloureds. The racial frequency distribution of the study population demonstrated that whites had a higher incidence of PCa when analysing their demographic profile in the province. Blacks had the highest median total serum prostate specific antigen (PSA) levels on presentation. When compared to that of the white study population, this was found to be statistically significant (p < 0.001). There was a significant association between stage of disease and race (p = 0.001). In the black group, a greater proportion had metastatic rather than localised or locally advanced disease, and in the white group the converse was seen, whereas in the Indian and coloured groups an almost equal proportion had localised or locally advanced disease versus metastatic disease. A crude analysis of progression free survival (PFS) data in patients with metastatic disease demonstrated that PFS was significantly (p = 0.003) longer for whites compared to blacks. Cox regression analysis did not confirm the influence of race on disease progression but this was confounded by incomplete data. Discussion The high incidence of whites in our study population relative to their racial distribution in the province may be explained by better educational and awareness levels of PCa and better access to healthcare facilities in this race group as compared to blacks. The data demonstrating a more advanced stage of disease presentation and higher median PSA levels in the black population may be reflective of an informational void on screening and awareness of PCa and/or a more aggressive disease course in this population group. The hypothesis that the black population may have a more aggressive disease course is given further credence by the crude analysis data suggesting a longer PFS for whites when compared to blacks. Conclusions This study invites further exploration of racial trends in PCa incidence, risk profile and outcomes amongst the diverse population groups of SA. / Thesis (M.Med.)-University of KwaZulu-Natal, Durban, 2009.

Prior research has suggested that life style factors, such as diet and physical activity, influence prostate cancer (PCa) progression. Metformin intake has been shown to be associated with decreased cancer risk in type II diabetic patients. We hypothesize that a low carbohydrate diet, prolonged aerobic exercise and metformin treatment can all independently slow prostate tumor development and a combination regimen will have an additive benefit. We used LNCaP xenografts to test this hypothesis. Results revealed that a diet low in carbohydrate reduced food consumption and a combination with exercise significantly reduced animal body weights. Ten weeks of metformin did not significantly alter tumor growth rate compared to control animals. Ten weeks of exercise significantly inhibited tumor growth. Out results suggest that dietary carbohydrate alteration or the administration of metformin alone cannot significantly influence prostate tumor progression. A suitable sustained exercise regimen may offer a more protective effect against PCa progression.

Enhanced resistance to radiation could be caused by both chronic hypoxia and acute hypoxic which has been reported in prostate cancer in various studies. Therefore currently used dose prescriptions (70Gy in 35 fractions) for external beam radiation therapy (EBRT) of prostate cancer has been suggested insufficient to provide optimum clinical outcome. In this study, we propose a Biologically Guided Radiation Therapy approach to boost dose in hypoxic prostate tumor regions while sparing the urethra. A previously proposed hypoxia model was modified for prostate cancer and incorporated into treatment plan optimization. The concept of equivalent uniform dose (EUD) was used in the optimization and evaluation of results. CT data from 25 prostate cancer patients who recently received EBRT at the British Columbia Cancer Agency (BCCA) and hypothetical hypoxic regions manually drawn on these CT scans were selected for this study. The results show that our methods could boost dose in target volume to substantially higher levels. EUD of planning target volume increased to more than 80Gy, despite accounting for effects of hypoxia. This increase was achieved with only minor changes in dose in normal tissues, typically less than 5Gy. Notably, urethra sparing was excellent with a EUD around 64Gy. Robustness of the proposed approach is verified against various hypoxic settings. EUD comparison between RT plans in biological guided and conventional approaches using the same RT technique (Volumetric Modulated Arc Therapy) also suggests that biologically guided radiation therapy (BGRT) approach is more suitable for dose painting purposes with the advantage of delivering sufficient dose to hypoxia region in different scenarios and sparing normal tissue better. Furthermore, we also investigated the impact of inter-fraction patient set-up error and intra-fraction organ motion on the high dose gradients achieved with this proposed dose painting method and explored the feasibility of adapting geometrical uncertainties (represented as systematic error and random error) into treatment planning. Image error obtained from EPID images are used to derive systematic uncertainty and random uncertainty. During the geometrical uncertainty adapted optimization, dose matrix in PTV is shifted based on systematic error and convolved with a Gaussian kernel which is pre-calculated using random error. CT sets and organ contours from five patients who enrolled in the previous dose painting i study are selected. For each of them, seven plans are generated using cumulated uncertainty data which was collected after every five fractions. We also present the outcome in terms of equivalent uniform dose (EUD). For four of the patients, EUD history of all seven plans suggests using the proposed optimization method with uncertainty data from the first five fractions, it is possible to achieve the same target coverage of static treatment plans (difference in EUD less than 1Gy). Meanwhile, the elimination of PTV margin also leads to a significant dose reduction (more than 15Gy) in rectum.

The evolution of prostate cancer from normal epithelium via the preneoplastic lesion of high-grade prostatic intraepithelial neoplasia to invasive carcinoma is characterised by a number of particular genomic abnormalities that are predominantly generated in the preneoplastic phase. Whilst there are numerous candidates for the cause of these alterations, telomere dysfunction is thought to be a major contributor. Telomeres are the terminal ends of human chromosomes, and when dysfunctional can lead to break-fusion-bridge cycles and multi-polar mitoses that generate numerical and structural chromosomal instability. The results presented reinforce the association of telomere dysfunction with the generation of certain markers of genomic instability such as abnormalities of the arms of chromosome 8. Furthermore, this work clarifies that the TMPRSSS2-ERG aberrations are not telomere related phenomena and are associated with a genomic deletion in a proportion of cases. Similarly, the PTEN microdeletions did not appear to have an association with telomere attrition. A previously unrecognised association between the telomere length in various types of prostatic epithelia and adjacent stroma is defined, suggesting evidence of a micro-environmental field effect in the generation of prostatic neoplasia. Finally, when examined retrospectively, it appears that telomere attrition, both in the HPIN epithelium and the stroma has independent prognostic value in the diagnosis of prostate cancer after a previous diagnosis of HPIN. Taken together, the research presented suggests important avenues for further research to determine the nature of barriers to the evolution of prostatic carcinogenesis such as oncogene- and telomere-induced senescence that may be exploited for therapeutic gain. These understandings may also help tailor management for prostate cancer such as risk stratification for men with HPIN and the use of targeted agents such as AKT inhibitors and telomerase inhibitors. In more advanced disease, translational application of this work has enabled a clinical trial of cytarabine in the treatment of metastatic hormone refractory prostate cancer.