Exploration and validation of novel liquid biomarkers in ovarian cancer of diagnostic and prognostic value

Abstract

Ovarian cancer (OC) is a lethal malignancy that severely impacts female health within the UK and across the world. It is the 6th most common cause of gynaecological cancer affecting women in the UK and affects approximately 7,500 per annum. Majority of women receive a confirmed diagnosis after they have progressed to an advanced stage (stage III/IV) of the disease, usually due to presentation of vague abdominal or gastrointestinal symptoms which is often mistaken for more benign conditions, like Irritable Bowel Syndrome (IBS). Serum CA125 is considered to be the current gold standard for diagnosing ovarian cancer in patients, however, it is found to be elevated in other malignancies as well as in non-cancerous conditions such as liver cirrhosis and pregnancy. CA125 levels are also not elevated in a significant amount of early-stage OC cases, which may lead to further delay in referral and treatment. Once diagnosed, patients respond well to treatment initially, but soon develop chemoresistance, leaving patients with limited treatment options. Liquid biopsies have been gaining significant attention within the scientific community as a promising alternative to tissue samples, providing non-invasive diagnostic approaches or serial monitoring of disease evolution. In this study, we explore novel biomarkers and show that their presence in patient blood samples can be detected and utilised for serial monitoring of treatment efficacy. Furthermore, this study dives beyond cancer detection and looks into the possibility of developing novel therapeutic targets for OC. Using high-definition image flow cytometry, we demonstrate the ability to detect circulating cancer-related cells (CCs) from blood samples of patients with advanced epithelial OC (aEOC). We report that the presence of AE1/AE3+ and WT1+ cells is significantly higher in-patient samples compared to controls (mean = 2914 and 547 CCs/ml, respectively). We also report the presence of CD34+ circulating endothelial cells in patients’ peripheral blood. We then investigated the mechanistic aspects of certain biomarkers and how informing on their functionality and involvement in OC could help discover new therapeutic targets; providing evidence for a novel role of surfactant protein D (SP-D) in ovarian cancer, as a biomarker and a therapeutic molecule. This thesis, completed with a pilot study investigating the shuttling effect of WT1, is important to understand the functional role of WT1 beyond just a biomarker used to confirm serous OC. On the whole, information obtained from liquid biopsies can cater to a wide array of functions from diagnosis/prognosis, minimally invasive serial monitoring to identification of new targets for therapeutic purposes.