Characterization and proteomic analysis of ovarian cancer-derived exosomes Bing Liang a , Peng Peng a , She Chen b , Lin Li b , Meijun Zhang b , Dongyan Cao a , Jiaxin Yang a , Haixia Li a , Ting Gui a , Xialu Li b, ⁎ , Keng Shen a, ⁎ a Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, China b National Institute of Biological Sciences, Beijing 102206, China ARTICLE INFO ABSTRACT Article history: Received 18 April 2012 Accepted 26 December 2012 Ovarian cancer is the most lethal type of cancer among all frequent gynecologic malignancies, because most patients present with advanced disease at diagnosis. Exosomes are important intercellular communication vehicles, released by various cell types. Here we presented firstly the protein profile of highly purified exosomes derived from two ovarian cancer cell lines, OVCAR-3 and IGROV1. The exosomes derived from ovarian cancer cell lines were round and mostly 30–100 nm in diameter when viewed under an electron microscope. The exosomal marker proteins TSG101 and Alix were detected in exosome preparations. The range of density was between 1.09 g/ml and 1.15 g/ml. A total of 2230 proteins were identified from two ovarian cell-derived exosomes. Among them, 1017 proteins were identified in both exosomes including all of the major exosomal protein markers. There were 380 proteins that are not reported in the ExoCarta database. In addition to common proteins from exosomes of various origins, our results showed that ovarian cancer-derived exosomes also carried tissue specific proteins associated with tumorigenesis and metastasis, especially in ovarian carcinoma. Based on the known roles of exosomes in cellular communication, these data indicate that exosomes released by ovarian cancer cells may play important roles in ovarian cancer progression and provide a potential source of blood-based protein biomarkers. © 2013 Elsevier B.V. All rights reserved. Keywords: Exosomes Proteomics Ovarian cancer 1. Introduction Ovarian cancer is the most lethal type of cancer among all frequent gynecologic malignancies all over the world [1,2]. Most patients are diagnosed with epithelial ovarian cancer in advanced stages and with subsequent platinum/taxane chemoresistance appearance, which are the two most impor- tant reasons for the high mortality associated with this cancer type [2,3]. Although serum CA-125 level evaluation and ultrasonography are clinically accepted methods for the diagnosis of ovarian cancer, they are not satisfactory methods for the early detection of ovarian cancer because of false positive and false negative results [2]. Cytoreductive surgery and subsequent platinum/taxane-based postoperative adju- vant chemotherapy have made some progress in improving the survival rate of patients with ovarian cancer, but the final recurrence and chemoresistance of the disease are still unsolved. So it is very urgent to find more sensitive diagnostic biomarkers and establish novel therapeutic strategies. Exosomes are spherical and bilayered proteolipids with a diameter of 30–100 nm. They are enriched in various bioac- tive materials, including proteins, lipids, miRNAs and mRNAs [4,5]. Exosomes are released from various cell types, includ- ing reticulocytes [6], immune cells (dendritic cells/T cells/B JOURNAL OF PROTEOMICS 80 (2013) 171 – 182 ⁎ Corresponding authors. Tel.: +86 10 65212507. E-mail addresses: lixialu@nibs.ac.cn (X. Li), shenkeng@vip.sina.com (K. Shen). 1874-3919/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jprot.2012.12.029 Available online at www.sciencedirect.com www.elsevier.com/locate/jprot