Glioblastoma, grade IV glioma, is the one of the deadliest cancers, with a median survival of only 12-15 months despite aggressive treatment including surgery, chemotherapy and radiation. One hallmark of glioblastoma is the morphological and functional abnormalization of tumor blood vessels. The molecular mechanisms involved in this process and their functional and pathological implications are not yet fully understood. Indentification of molecular mechanisms that underlie vascular abnormalization in GBM is necessary to develop efficient treatment regimens for normalizing vascular function. By analyzing the RNA-content of laser microdissected vessels from human biobank specimens using affymetrix microarray analysis, we found that the abnormal glioblastoma vessels have a distinct gene expression signature. We found 95 genes which were differentially expressed in grade IV glioma vessels as compared to vessels in low grade tumors and control brain. 78 of which were up-regulated while 17 were down-regulated. Many of these genes are regulated by VEGFA or TGFβ signaling. In addition, we show a significant increase in Smad signaling complexes in the vasculature of human glioblastoma in situ, suggesting that TGFβ signaling may play important role in vessel abnormalization. CD93 is a single-pass transmembrane glycoprotein, which we found to be up-regulated in high grade glioma. Vascular expression of CD93 correlates to tumor grade in human glioma. Moreover, high grade glioma patients with high CD93 expression in the vasculature are associate with poor prognosis. We found that knocking down CD93 in endothelial cells with siRNA clearly impaired endothelial cell adhesion, migration and tube formation due to defects in cytoskeletal rearrangement. In addition, tumor growth was severely delayed in the CD93-/- mice. Pleiotrophin, a multi-functional heparin-binding growth factor, promotes glioma growth in several ways. Here, we identify pleiotrophin as a driver of vascular abnormalization in glioma. We found that high pleiotrophin expression correlates with poor survival of patients with astrocytomas. Pleiotrophin overexpression in orthotopic GL261 gliomas increases microvessel density, enhances tumour growth and decreases survival. Vessels in pleiotrophin-expressing gliomas are poorly perfused and display a high degree of abnormality, coinciding with elevated levels of vascular endothelial growth factor (VEGF) deposited in direct proximity to the vasculature. In addition to its role in vessel abnormalization, pleiotrophin enhanced PDGF-B-induced gliomagenesis. Taken together, our results indicate that PTN has an important role in glioma initiation and establishment of the characteristic abnormal tumor vasculature in glioblastoma, identifying PTN as a potential target for therapy.

The Myc transcription factor activates expression of genes that promote cellular functions such as proliferation and cell growth. The deregulated Myc expression, characteristic for the tumor cell, also activates apoptosis, which selects for additional genetic changes deactivating the induced cell death. However, the continuous overexpression of Myc can also be a liability for a tumor, which can be taken advantage of in cancer treatment.  In Paper I, we describe a new way of using the DNA methyltransferase inhibitor Decitabine, in treating Myc overexpressing tumors. We show that Decitabine treatment activates cell death by reactivating silenced tumor suppressors such as Puma, but also by inducing DNA damage. Decitabine treatment of Myc driven lymphomas is also shown to prolong disease free survival in mouse models. Myc driven transformation requires a collaborative deregulation of genes. The family of Pim kinases has been shown to collaborate with Myc in tumorigenesis. In Paper II, we show that the Pim-3 kinase protein is highly expressed in many Myc overexpressing lymphomas from Myc transgenic mice as well as human Burkitt Lymphoma samples. The Pim-3 locus is shown to interact with the Myc protein and be a direct target for Myc activated transcription. Additionally, we demonstrate that the Pim kinase inhibitor, Pimi, targeting the Pim kinase family (Pim-1, Pim-2 and Pim-3), induce a cell death that is mediated by, but not dependent on caspase activity. The Pimi induced cell death was potentiated when combined with RNAi knockdown of the casein kinase II (CK2) protein.  In paper III, we describe the development of a somatic mouse model for lymphomagenesis, utilizing the RCAS-tva technology. We show that primary B cells from these mice are transducible and transformed when infected with a combination of RCAS- HA tagged Myc, KRasV12D and human Bcl-XL virus. In conclusion, we show that the labile milieu created by the deregulated expression of Myc facilitates new approaches in treatment of Myc overexpressing tumors. Also, our new tva mouse model show promise in modeling lymphomagenesis.

Concerns about declines in marine biodiversity led to the creation of marine protected areas and spatial fishery closures as tools for recovery. Yet many marine conservation areas suffer low levels of compliance from diverse fishing populations, including recreational fishers. Little research quantifies levels of recreational fisher compliance and its drivers, especially in temperate marine environments, despite the prevalence of this kind of fishing in some regions. This thesis addresses this knowledge gap through a study of recreational fisher compliance in Rockfish Conservation Areas (RCAs) in British Columbia, Canada. One hundred and sixty four RCAs were implemented between 2003 and 2007 and now cover 4847.2 km2. These conservation areas were created in response to widespread concern from fishers and non-governmental organizations about inshore rockfish population declines. However, recent research suggested that recreational fisher compliance might be low. This thesis had two goals: 1) contribute to knowledge about, and develop methods of assessing, non-compliance within marine conservation areas, and 2) address the immediate problem of suspected recreational non-compliance in RCAs. I had the following objectives: 1) Assess ecological and social RCA effectiveness to date, using a framework for improving governance from the literature on common pool resources; 2) Assess recreational fisher knowledge and perceptions of RCAs, and 3) Quantify non-compliance and social and ecological compliance drivers in RCAs. Methods included a literature review, structured surveys with 325 recreational fishers at 16 locations in the Salish Sea (Southern Gulf Islands and Victoria area), and trail camera monitoring in 42 coastal locations (both RCAs and unprotected sites). Results show that recreational fisher knowledge and compliance to RCA regulations is low. The assessment of social and ecological effectiveness shows much room for management improvement for recreational fisheries. This finding is supported by my survey and trail camera data. I found that 25.5% of recreational fishers had never heard of RCAs and ~60% were unsure of RCA locations. The total non-compliance rate was 23% in RCAs. Seventy nine percent of trail camera monitored RCA sites showed confirmed or probable fishing activity, with no significant difference between fishing effort inside and outside RCAs. However, 77% of fishers surveyed believed that rockfish conservation is necessary with advertising, fisher education, and increased monitoring offered as solutions to non-compliance. I recommend managers implement a public outreach and education campaign to address low levels of compliance. This study suggests that positive perceptions of marine conservation areas and conservation initiatives are not enough to create high compliance. Educating stakeholders and creating high levels of awareness should be an essential first step when creating marine conservation areas. My research offers important insights into the study of non-compliance, and the immediate problem of recreational non-compliance in BC’s RCAs. My successful use of a simple and cost/time efficient multiple methods approach to assessing compliance provides robust tools for future compliance analyses, and hence provides a valuable contribution to the compliance literature. The study also suggests that trail camera monitoring could be a promising new method for monitoring coastal conservation areas. / Graduate / 0768 / 0792 / 0306

Abstract Addressing the formidable challenges presented by diffuse midline glioma (DMG), a notably aggressive pediatric brain tumor with limited therapeutic options, this study investigates the oncogenic roles of MYC and PDGFB and evaluates SOX9's contribution to therapeutic resistance. Utilizing advanced transgenic mouse models and the RCAS virus system, our research effectively simulates the progression and treatment responses characteristic of DMG.   In our approach, we established a DMG tumor model by manipulating Tumor Virus A receptor (TVA)-expressing embryonic neural stem cells sourced from the E12.5 hindbrain in vitro. Validation of this model and its genetic perturbations was achieved through detailed Western blot analyses. Results indicate that DMG cells overexpressing MYC tended to be significantly more sensitive to chemotherapy compared to PDGFB cells that do not overexpress MYC, positioning MYC as a crucial therapeutic target. On the other hand, increased expression of SOX9 was linked to a slight increase in resistance to conventional treatment modalities, highlighting its role in promoting adaptive resistance mechanisms within the tumor microenvironment.   This research emphasizes the critical importance of merging molecular biology techniques with comprehensive in vivo modeling to elucidate DMG's pathophysiology and identify actionable therapeutic targets. Our findings offer significant insights into the molecular dynamics of DMG and suggest novel targets for therapeutic intervention that could substantially improve clinical outcomes in this challenging pediatric malignancy. Future research should aim to broaden the genetic profiling of DMG, and tailor therapeutic approaches based on specific molecular profiles to optimize treatment efficacy and precision.

Gliomas are the most common primary tumors of the central nervous system believed to arise from glial cells. Invasive growth and inherent propensity for malignant progression make gliomas incurable despite extensive treatment. I have developed a life-like orthotopic glioma model and used this and other in vivo models to study basic mechanisms of glioma development and treatment. Previous studies had indicated that experimental gliomas could arise from glial stem cells and astrocytes. The present thesis describes the making and characterization of a novel mouse model, Ctv-a, where gliomas are induced from oligodendrocyte progenitor cells (OPCs). Our study shows that OPCs have the capacity to give rise to gliomas and suggests in light of previous data that the differentiation state of the cell of origin affects tumor malignancy. CDKN2A encodes p16INK4a and p14ARF (p19Arf in mouse) commonly inactivated in malignant glioma. Their roles in experimental glioma have been extensively studied and both proteins have tumor suppressor functions in glial stem cells and astrocytes. Here, we demonstrate that p19Arf only could suppress gliomagenesis in OPCs while p16Ink4a had no tumor suppressive effect. Functional DNA repair is pivotal for maintaining genome integrity, eliminating unsalvageable cells and inhibiting tumorigenesis. We have studied how RAD51, a central protein of homology-directed repair, affected experimental glioma development and have found that expression of RAD51 may protect against genomic instability and tumor development. Angiogenesis, the formation of new blood vessels from pre-existing ones, is a central feature of malignant progression in glioma. Antiangiogenic treatment by inhibition of vascular endothelial growth factor receptor signaling is used in the clinic for treatment of some cancers. We have investigated the effect of an alternative antiangiogenic protein, histidine-rich glycoprotein (HRG), on glioma development and found that HRG could inhibit the formation of malignant gliomas and completely prevent the formation of glioblastoma.

Most viruses can infect only a reduced range of organisms and an effective replication is possible only in selected hosts. These hosts are called permissive for the virus. Molecular principles of a nonpermissiveness and viral mechanisms of overcoming replication obstacles are still not clearly elucidated. This thesis discusses the molecular causes of the cellular nonpermissiveness against a model retrovirus - Rous sarcoma virus. The research is conducted on duck cells which are semipermis- sive to the subgroup C of Rous sarcoma virus. The virus can enter those cells, but it is not able to produce enough infectious viral progeny. Two blocks of the viral replication cycle in the duck cells are described in the thesis. The first one is the probably not optimal cellular receptor recognition. The second one is in the late phase of the replication cycle when the viral proteins are synthesized. The amount of the envelope glyco- protein coding mRNA is reduced due to the altered splicing ratios, and the virions produced from the duck cells are less infectious. This block is recessive and can be partially omitted by cell fusions with permissive chicken cells; therefore, the block is not caused by specific restriction fac- tors in sensu stricto. Additionally, the influence of mutations in duck adapted Rous...