Abstract 5697: Proteomic analysis of prostate cancer-related exosomes isolated by anti-PSMA antibody beads

Purposes of the study: Exosome has been demonstrated to be a useful non-invasive biomarker for several cancers including prostate cancer. For better understanding cancer-derived exosome, their proteomic analysis is necessary. The aim of this study is to establish the method for isolation and analysis of prostate cancer-related exosomes. Experimental procedures: Total exosomes were isolated from the conditioned media of LNCaP cells by ultracentrifugation. Then, exosomes positive for CD9 or prostate specific membrane antigen (PSMA) were isolated by magnetic beads conjugated with anti-CD9 or -PSMA antibody, respectively. Isolated exosomes were subjected to proteomic analysis. The PSMA positive fraction was also collected by anti-PSMA beads from diluted serum of 3 prostate cancer patients and analyzed by proteomics. Results: A total of 126, 139 and 13 proteins were detected in the LNCaP exosome fractions that were isolated by ultracentrifugation, anti-CD9 beads and anti-PSMA beads, respectively. Out of 126 proteins identified in ultracentrifuge isolated exosome, 56 and 6 protein were found in exosomes that were isolated by anti-CD9 beads and anti-PSMA beads, respectively. Seven proteins were commonly detected in exosomes that were isolated by both beads. Fifty, 54 and 48 proteins were identified in the PSMA positive fraction from serum of 3 prostate cancer patients (P1: localized prostate cancer, P2: advanced prostate cancer and P3: castration resistant prostate cancer). Thirty-three proteins were detected in one patient, 22 in two patients and 25 in three patients. Most proteins detected in all patients were serum- or immunoglobulin-related proteins. The numbers of proteins that were detected only in P2 and P3 were 16 and 8, respectively. Six proteins were found in both P2 and P3 patients. Conclusion: In the present study, we analyzed prostate cancer-related exosomes that were isolated by immunoaffinity-based method. Although most proteins were serum- or immunoglobulin-related proteins, proteins that had been reported as a cancer marker were also detected, which could be candidates for exosomal marker of prostate cancer. Citation Format: Kosuke Mizutani, Kyojiro Kawakami, Yasunori Fujita, Kengo Horie, Koji Kameyama, Masafumi Ito, Takashi Deguchi. Proteomic analysis of prostate cancer-related exosomes isolated by anti-PSMA antibody beads [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 5697. doi:10.1158/1538-7445.AM2017-5697