Medicine (St Vincent's) - Theses
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ItemInvestigating novel therapies for osteosarcoma using advanced medical imaging( 2012)Osteosarcoma is the most common primary cancer of bone. Current best treatment consists of chemotherapy and surgery, however many tumours are chemoresistant. Spread of osteosarcoma to the lungs is frequent and is the most common cause of death. This thesis examines the role of pigment epithelium-derived factor (PEDF) in the processes of osteosarcoma growth, invasion and metastasis. In order to evaluate this potential role, both in vitro and in vivo studies have been performed. In vitro studies have examined the biological effects and mechanisms of PEDF. PEDF exhibits a multifaceted ability to inhibit osteosarcoma tumorigenicity. PEDF inhibits proliferation, induces apoptosis and reduces cell cycling of osteosarcoma cells in vitro. Additionally, the metastatic capacity of osteosarcoma cell lines is diminished by PEDF. Osteosarcoma cells treated with PEDF demonstrate an enhanced capacity for adhesion and a reduced ability for invasion through collagen I, the most abundant protein in bone. An established murine model of orthotopic osteosarcoma has been optimised for the evaluation of novel therapeutic agents in vivo. This model allowed for an evaluation of systemically delivered PEDF and PEDF-derived peptides, both as sole treatments and in combination with doxorubicin. Systemic administration of PEDF causes a reduction in both primary tumour volume and pulmonary metastatic disease. PEDF-derived peptides, StVOrth-2 (residues 78-102) and StVOrth-3 (residues 90-114) were also delivered systemically. StVOrth-2 primarily restricts growth of primary osteosarcoma while StVOrth-3 restricts pulmonary metastatic disease. Finally, advanced medical imaging techniques have been applied to this murine model of orthotopic osteosarcoma for the study of tumour growth, invasion and metastasis; in vivo bioluminescent imaging, [18F]-Fluoride-PET, [18F]-FDG-PET and micro-computed tomography provide novel information about this model. Use of these imaging modalities has improved osteosarcoma modelling and allowed closer monitoring of disease progression. This is the first time that in vivo imaging has been used in the assessment of PEDF’s anti-osteosarcoma properties and is a major advance from previously published studies demonstrating direct effects on osteosarcoma growth and metastasis.