Adaptive Dynamic Artificial Polyligand Targeting (Adapt): A Method To Identify Exosomal Proteins From A Prostate Cancer Cell Line

In the recent years it was demonstrated that a multitude of body fluids contains substantial amounts of exosomes, extracellular vesicles with sizes ranging between 40 and 100 nm. Those vesicles have protein profiles characteristic of their cells of origin. It was shown that exosomes play a role in cell-to-cell communication making them attractive targets to identify early disease stage biomarkers. Cancer heterogeneity is known for a long time to be an important clinical determinant of patient outcome. We developed the highly multiplexed ADAPT platform to capture systems-based biological signatures that may reflect the molecular heterogeneity of various cancer types and help to improve diagnosis of the disease. Exosomes from two prostate cancer cell lines, VCaP and LNCaP, were used to train ssDNA libraries to discriminate them. A highly diverse library of 1012 oligonucleotides (ODNs) was subjected to five rounds of positive and negative selection against exosomes from VCaP and LNCaP prostate cancer cell lines. Individual ODNs that bound preferably to exosomes from VCaP cells were identified by NGS, resynthesized and binding of co-precipitated ODNs to VCaP exosomes was verified by qPCR. LC-MS/MS was used to identify binding partners of ODNs bound to VCaP exosomes. Several of those binding partners (CHMP1b/2a/4b, VPS28, Syntenin-1) were found to be part of the ESCRT machinery, which participates in exosomes biogenesis. It was found that those proteins are overexpressed in human cancers. In addition, we identified the chemokine I-TAC, which is overexpressed in blood and tissue of men with advanced prostate adenocarcinomas. Finally, we found hnRNP-1, a cancer associated splicing factor, and the cold shock proteins RNPL and A18 hnRNP. Knock-down of these cold shock proteins has been shown to enhance chemotherapeutic cell killing of prostate cells. ADAPT is an unbiased profiling platform that identifies cancer associated proteins expressed on exosomes. This platform can be deployed against multiple cancer types and offers broad potential applications in biomarker discovery. Citation Format: Tassilo Hornung, Stephen Logie, Aniket S. Bondre, Varun Maher, Melissa N. Richards, Jelena Zarkovic, Teresa T. Tinder, Heather A. O9Neill, Mark R. Miglarese, David B. Spetzler. Adaptive dynamic artificial polyligand targeting (ADAPT): a method to identify exosomal proteins from a prostate cancer cell line [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 2214. doi:10.1158/1538-7445.AM2017-2214