Abstract 3190: Capture and molecular characterization of ovarian cancer-derived exosomes

Abstract

Exosomes are secreted, membrane-bound vesicles of 50-100 nm known to carry cellular messenger RNAs (mRNA) and microRNAs (miRNA). Several reports have indicated that tumor-derived exosomes are released into the circulation of patients with a variety of cancer types, including epithelial ovarian cancer. The goals of this study are (i) to develop methods for specific capture and molecular profiling of ovarian cancer tumor-derived exosomes from blood plasma and (ii) determine whether information carried in tumor-derived exosomes can serve as a reliable surrogate for tumor tissue for measurement of key miRNA and mRNA biomarkers. In our work to date, we have used exosomes derived from conditioned media of ovarian cancer cell lines to develop and optimize methods for the isolation and physical characterization of exosomes. Using Nanoparticle Tracking Analysis (NTA) technology (NanoSight, Inc.) to directly count and accurately size exosome populations, our initial data indicates that traditional ultracentrifugation protocols may fail to recover a major fraction of exosomes present in conditioned media. The basis for this finding is currently under investigation and the latest results will be presented. In parallel, we are developing affinity capture approaches to isolate specific subpopulations of exosomes using antibodies directed against epithelial cell adhesion molecule (EpCAM) and other exosomal surface proteins. Initial results indicate that a subpopulation of ovarian cancer-derived exosomes can be purified in this manner; molecular characterization of exosomal contents is in progress. Finally, we are analyzing clinical plasma specimens from patients and controls to: (i) test whether bulk properties of exosomes (e.g., size and number) differ between cases and controls, and (ii) perform specific capture of tumor-derived plasma exosomes and compare exosomal mRNA/miRNA profiles to matched tumor tissue to determine the degree of concordance between exosomal and tissue RNA profiles. Latest results from these studies will be presented. Ultimately, we anticipate that this work will lead to methods for molecular phenotyping of epithelial ovarian cancers in individual patients using a blood-based approach. This work was supported in part by a Stand Up To Cancer/AACR Innovative Research Grant to M. Tewari. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3190. doi:1538-7445.AM2012-3190