<p>Renal cell carcinoma (RCC) is the most frequently lethal of urological cancers. It arises in the lining of the proximal convoluted tubule of the kidney and is most common in men ages 50–70. Often, partial or radical nephrectomy is needed to effectively treat the disease, leaving patients with reduced kidney function. RCC frequently displays significant radiation resistance, limiting the usefulness of traditional radiation therapy which might spare patients’ normal tissue. The enzyme carbonic anhydrase 9 (CA9), a product of the hypoxia pathway, is found upregulated in the majority of RCC, particularly the clear cell type. It catalyses the dissolution of carbon dioxide into water as bicarbonate and has been linked to increased invasion and migration in RCC tumour cells. The radiation resistance of two RCC cell lines 786-O (human CCRCC) and RAG (murine renal adenocarcinoma) was investigated by the clonogenic assay in the presence of a CA9 inhibitor or silencing RNA. The interference with CA9 by either of these methods significantly sensitizes 786-O cells to the effects of ionizing radiation <em>in vitro</em>. Moreover, fractionation of the dose delivered can increase this sensitization effect. It is hoped that current targeting of CA9 can make radiation therapy a more feasible option in the treatment of RCC.</p> / Master of Science (MSc)