The identification and evaluation of novel biomarkers for epithelial ovarian cancer

Abstract

Ovarian cancer (OvCa) is the 6th most common cancer in the UK and is the leading cause of death for patients with gynaecological cancers, accounting for 184,779 deaths worldwide. Unfortunately, lack of effective screening and vague symptoms account for 70% of patients being diagnosed at the later stages, resulting in poorer prognoses. As well as this, there is a lack of consensus for the occurrence of relapse and for determining treatment response, leading to delayed treatment and, again, a poorer prognosis. The main culprit for this delay is the current clinical marker, CA-125, which has poor sensitivity and specificity. Approximately 20% of patients are non-secretors of the CA-125 marker, and it is elevated in other diseases and malignancies. Due to all of this, it is clear that more efficacious markers need to be discovered. In this thesis, we have used online databases, RNA sequencing and Immunohistochemistry to determine the potential use of CIP2A and RAD51AP1 as biomarkers for OvCa prognosis and treatment response. We find that both of these biomarkers have increased expression in OvCa and that this increased expression is correlated to decreased PFS and OS. We also determine CIP2A expression in different ages, stages, grades and types of OvCa patients, as well as mutation frequency, altered pathways, and protein structure. Following this, utilising in vitro models, we inhibited both RAD51AP1 and CIP2A through different means (siRNA and inhibitor, respectively) and determined the changes through RNA sequencing in differentially expressed genes and molecular landscape. We further determine any connection with diseases and malignancies and investigated their potential clinical utility as biomarkers. Liquid biopsies offer an alternative to conventional invasive tissue biopsies and are advantageous due to their ease of availability and less invasive nature. Unlike traditional biopsies, liquid biopsies offer the opportunity for serial monitoring of patients undergoing treatment, possibly providing early warning of treatment resistance and relapse. To further our data above we decided to use a type of liquid biopsy, this being patient blood, to evaluate the efficacy of six different biomarkers for use in predicting treatment response, resistance, and relapse. Out of these, ccfDNA, CIP2A, RAD51AP1, and telomere length appear to have a promising use as prognostic biomarkers, as they outperform or mirror CA-125, especially in the case of the non-secretors. Collectively, the data shows promise in using ccfDNA, CIP2A, RAD51AP1, and telomere length as clinical biomarkers for OvCa. Future work would include the expansion of the datasets and investigation of the use of these markers to diagnose OvCa.