Yasuaki Kabe1,2, Makoto Suematsu3, Satoshi Sakamoto4, Miwa Hirai3, Ikko Koike3, Takako Hishiki3, Atsushi Matsuda3, Yuichi Hasegawa5, Koji Tsujita5, Masayuki Ono5, Naoko Minegishi6, Atsushi Hozawa7, Yoshinori Murakami8, Michiaki Kubo9, Makoto Itonaga1,5, Hiroshi Handa10. 1. Department of Biochemistry, Keio University School of Medicine, Tokyo, Japan; ykabe@z3.keio.jp itonaga.makoto@jvckenwood.com hhanda@tokyo-med.ac.jp. 2. Japan Agency for Medical Research and Development (AMED), Core Research for Evolutional Science and Technology (CREST), Tokyo, Japan. 3. Department of Biochemistry, Keio University School of Medicine, Tokyo, Japan. 4. School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan. 5. Healthcare Business Division, JVCKENWOOD Corporation, Yokosuka, Japan. 6. Tohoku Medical Megabank Organization, Tohoku University, Sendai, Miyagi, Japan. 7. Department of Preventive Medicine and Epidemiology, Tohoku Medical Megabank Organization, Tohoku University, Miyagi, Japan. 8. Division of Molecular Pathology, Institute of Medical Science, The University of Tokyo, Tokyo, Japan. 9. RIKEN Center for Integrative Medical Sciences, Yokohama, Kanagawa, Japan. 10. Department of Nanoparticle Translational Research, Tokyo Medical University, Tokyo, Japan. ykabe@z3.keio.jp itonaga.makoto@jvckenwood.com hhanda@tokyo-med.ac.jp.
Abstract
BACKGROUND: Although circulating exosomes in blood play crucial roles in cancer development and progression, difficulties in quantifying exosomes hamper their application for reliable clinical testing. By combining the properties of nanobeads with optical disc technology, we have developed a novel device named the ExoCounter to determine the exact number of exosomes in the sera of patients with various types of cancer. METHOD: In this system, individual exosomes were captured in the groove of an optical disc coated with antibodies against exosome surface antigens. The captured exosomes were labeled with antibody-conjugated magnetic nanobeads, and the number of the labeled exosomes was counted with an optical disc drive. RESULTS: We showed that the ExoCounter could detect specific exosomes derived from cells or human serum without any enrichment procedures. The detection sensitivity and linearity with this system were higher than those with conventional detection methods such as ELISA or flow cytometry. In addition to the ubiquitous exosome markers CD9 and CD63, the cancer-related antigens CD147, carcinoembryonic antigen, and human epidermal growth factor receptor 2 (HER2) were also used to quantify cancer cell line-derived exosomes. Furthermore, analyses of a cross-sectional cohort of sera samples revealed that HER2-positive exosomes were significantly increased in patients with breast cancer or ovarian cancer compared with healthy individuals and those with noncancer diseases. CONCLUSIONS: The ExoCounter system exhibits high performance in the direct detection of exosomes in cell culture and human sera. This method may enable reliable analysis of liquid biopsies.
BACKGROUND: Although circulating exosomes in blood play crucial roles in cancer development and progression, difficulties in quantifying exosomes hamper their application for reliable clinical testing. By combining the properties of nanobeads with optical disc technology, we have developed a novel device named the ExoCounter to determine the exact number of exosomes in the sera of patients with various types of cancer. METHOD: In this system, individual exosomes were captured in the groove of an optical disc coated with antibodies against exosome surface antigens. The captured exosomes were labeled with antibody-conjugated magnetic nanobeads, and the number of the labeled exosomes was counted with an optical disc drive. RESULTS: We showed that the ExoCounter could detect specific exosomes derived from cells or human serum without any enrichment procedures. The detection sensitivity and linearity with this system were higher than those with conventional detection methods such as ELISA or flow cytometry. In addition to the ubiquitous exosome markers CD9 and CD63, the cancer-related antigens CD147, carcinoembryonic antigen, and human epidermal growth factor receptor 2 (HER2) were also used to quantify cancer cell line-derived exosomes. Furthermore, analyses of a cross-sectional cohort of sera samples revealed that HER2-positive exosomes were significantly increased in patients with breast cancer or ovarian cancer compared with healthy individuals and those with noncancer diseases. CONCLUSIONS: The ExoCounter system exhibits high performance in the direct detection of exosomes in cell culture and human sera. This method may enable reliable analysis of liquid biopsies.