Abstract 725: Feasibility and evaluation of exosomal RNAs as novel diagnostic biomarkers for high grade serous epithelial ovarian cancer

Abstract

Abstract Introduction: High-grade serous ovarian cancer (HGSOC) survival has been essentially unchanged over the last ten years despite new therapeutic strategies. In order to make a large-scale impact on overall survival, early detection strategies are imperative. Exosomes are cell-derived vesicles derived from multivesicular bodies or the plasma membrane that carry a variety of biomolecules, including protein, DNA, and RNA. Exosomal contents represent a novel and underexplored source of tumor biomarkers, in particular for HGSOC. This study aimed to first evaluate approaches to exosomal RNA purification and to then compare the exosomal RNA profiles from serum of patients with benign ovarian disease and HGSOC to determine if unique profiles exist, and to identify biomarkers useful for early detection. Methods: Cell free serum was obtained from patients in each of the following categories: HGSOC with early (n=24) or late stage (n=24) disease, benign ovarian masses (n=24) and healthy age-matched controls (n=24). We compared ultracentrifugation and a commercial precipitation solution to enrich and isolate exosomes. Exosomal enrichment was confirmed by both transmission electron microscopy (TEM) and western blot using anti-CD63 antibodies. RNA was extracted for each and deep sequencing analysis was performed for 12 candidates within each group. A second cohort of 48 samples will be used for validation of the best performing candidate biomarkers from the discovery cohort via RT-qPCR. Results: Enrichment of exosomes was confirmed via qualitative assessment using TEM and Western blot analysis. RNA quality was superior when RNA isolations were performed using the QIAgen RNeasy kit compared to the AllPrep kit. Mean RNA yield for each group ranged from 10.3-28.6ng/µl and RNA yield and quality was independent of sample age. RNAseq analyses are ongoing to identify biomarkers specific to HGSOC that can be detected at the earliest stages. The top differentially RNAs for the ovarian cancer groups will be validated in an independent cohort of specimens. A panel will then be generated in combination with CA125 to determine the clinical utility of an integrated -omics approach in early stage detection of HGSOC. Conclusions: Efficient isolation of exosomes and RNA can be achieved from archived specimens >10 years old. Evaluation of exosomal RNA in HGSOC provides a novel method for biomarker discovery. Citation Format: Emily N. Prendergast, Xianzhi Lin, Rosario I. Corona, Dennis J. Hazelett, Beth Y. Karlan, Kate Lawrenson. Feasibility and evaluation of exosomal RNAs as novel diagnostic biomarkers for high grade serous epithelial ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 725. doi:10.1158/1538-7445.AM2017-725