Techniques Associated with Exosome Isolation for Biomarker Development: Liquid Biopsies for Ovarian Cancer Detection

Ovarian cancer is the leading gynecological malignancy worldwide. This is attributed to the fact that the disease is often diagnosed at an advanced stage, where the survival rates drop from approximately 90% (detection at an early stage) to 20%. Furthermore, ovarian cancer is not associated with overt physical symptoms. Thus, there is an urgent need for a highly sensitive and minimally invasive biomarker for the early detection of ovarian cancer. However, this continues to remain an unmet clinical need, as several proposed techniques have shown low sensitivity and specificity, with poor positive and negative predictive values. The quest for an ideal biomarker has bought exosomes to the forefront. Exosomes are small extracellular vesicles of an endocytic origin, which can encapsulate genetic information, in the form of proteins and miRNAs. They are released by multiple cell types and are involved in intercellular communication, through the transfer of their cargo. The process of exosome biogenesis allows for the packaging of molecules from both membranous and cytosolic origins. Therefore, exosomes are representations of the releasing cell, and thus provide an insight into the cellular environment. Furthermore, exosomal encapsulation of molecules such as proteins and miRNAs can prevent degradation, making exosomes an ideal biomarker source. Thus, this chapter provides an overview of ovarian cancer, the potential of exosomes as an early detection biomarker, and the different methods associated with the isolation of different vesicle subpopulations, and exosome enrichment.