Clinical Pathology - Theses
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ItemA Proteomic Exploration of Chemotherapeutic Resistance Mechanisms in Metastatic Colorectal Cancer( 2022)There is a substantial global burden of colorectal cancer with many patients developing or presenting with distant metastases, most commonly within the liver. Though curative surgery can be attempted, modern clinical management of metastatic colorectal cancer is heavily reliant on systemic chemotherapy. The most administered chemotherapeutic regimen in Australia is FOLFOX, whose constituent drugs are the pyrimidine antimetabolite 5-Fluorouracil and the platinum based alkylating agent Oxaliplatin. Despite being highly cytotoxic, their clinical efficacy is limited by mechanisms of chemotherapeutic resistance within cancer cells, which contributes to poor patient outcome. Protein level research of these mechanisms has traditionally been limited in scope and often restricted to two-dimensional cell experimental models. Hence, there is an unmet need for proteomic analyses of chemotherapeutic response in models with greater physiological relevance, like three-dimensionally cultured organoids. In this thesis, we optimised a mass spectrometry sample preparation method to permit the proteomic analysis of metastatic colorectal cancer patient derived tumour organoids and their supernatants. We then analysed the proteomes of organoids with differential responses to 5-Fluorouracil and Oxaliplatin treatment using mass spectrometry, finding proteins associated with a mitotic cell cycle theme to be of greater abundance in relatively 5-FU/Oxal resistant samples compared to sensitive ones. Using western blotting,CDK1 expression was shown to be significantly increased in relatively resistant organoid samples during 5-FU/Oxal exposure compared to sensitive ones, though its inhibition did not re-sensitise them to chemotherapy. A proteomic analysis of organoid supernatants also revealed significantly greater levels of GSTP1 within the supernatants of sensitive organoids, when compared to relatively resistant ones. These discoveries help describe mechanisms by which metastatic colorectal cancer cells can evade the cytotoxic effects of chemotherapeutic drugs.