Abstract 5663: Proteomic analysis of exosomes isolated from ccRCC cell lines

Purposes of the study: Clear renal cell carcinoma (ccRCC) is one of the most lethal malignant tumors. Molecular targeted therapies have been used to improve outcomes for metastatic or advanced ccRCC. However, currently approved therapies have limited success and a cure remains elusive. Since ccRCC could be curable if diagnosed at the early stage, novel diagnostic approach is needed to identify circulating markers that may help diagnose early and evaluate prognosis. Exosomes are membrane vesicles with a diameter of 40-150 nm that are secreted by various types of cells including cancer cells. Exosomes contain a variety of molecular constituents of their origin such as proteins and nucleic acids. Over the years, exosome has been suggested to be a novel diagnostic marker. The purpose of this study is to find candidates of ccRCC markers in exosomes. Experimental procedures: Exosomes were collected from cell culture supernatant of RPTEC human renal proximal tubule epithelial cells and ccRCC cell lines (Caki-1, KMRC-1, and OS-RC-2) by ultracentrifugation. Isolation of exosome was confirmed by western blot analysis for CD9. Exosome fraction was analyzed by iTRAQ-based quantitative proteomics. Results: A total of 52 proteins were detected and 3 proteins were found to be upregulated by more than 1.2 fold in exosomes isolated from ccRCC cells compared with those from RPTEC cells. Twelve proteins were found to be downregulated by less than 0.8 fold in exosomes from ccRCC cells compared with those from RPTEC cells. The expression profiles of several proteins were verified by western blot analysis. Conclusions: While major challenges still remain, exosome studies in ccRCC could provide a wealth of information to find novel diagnostic and prognostic markers. Citation Format: Kosuke Mizutani, Kyojiro Kawakami, Yasunori Fujita, Kengo Horie, Masafumi Ito, Takashi Deguchi. Proteomic analysis of exosomes isolated from ccRCC cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5663.