Abstract 3955: Expression of cancer stem cell-associated proteins in exosomes derived from ascites of patients with advanced pancreatic cancer

Abstract

Abstract Background: The number of patients with pancreatic cancer is rapidly growing, and the disease is the fifth leading cause of cancer-related death in Japan. At end stage of the disease, the patients are prone to suffer peritonitis carcinomatosa with chemorefractory ascites. It is known that cancer cells surviving in ascites show cancer stem cell (CSC)-like features (PLoS One 2012). The CSC-like cells robustly secrete extracellular vesicle called exosome, which plays important roles in tumorigenesis, tumor growth, metastasis, angiogenesis, pre-metastatic niche formation, immunosuppression, drug resistance, and epithelial-mesenchymal transition. The AIM of this prospective study was to assess whether exosomes taken from malignant ascites of patients with advanced pancreatic cancer included the CSC-associated proteins, that might be predictive markers for chemoresistance and prognosis. Methods: The malignant ascites was collected from the cancer patients who underwent abdominocentesis and/or cell-free and concentrated ascites reinfusion therapy (CART) in Kurume University Hospital. Ascites derived from patients with benign diseases, including decompensated liver cirrhosis (d-LC), was used as control. Informed consent was obtained from all of the patients. Exosomes in ascites were purified by using ExoQuick Exosome Precipitation Solution (System Biosciences) according to the manufacturer's protocol. Western blot analysis was performed to detect CSC-associated proteins, including CD133, CD44, CD44v9, xCT, CD24, and Dclk1. Results: Successful purification of exosomes from both the malignant ascites and the benign one was confirmed by monitoring exosome-specific proteins such as CD68, CD9, CD81, and HSP70. Among the CSC-associated proteins examined, CD133 was predominantly expressed in exosomes obtained from ascites of the pancreatic cancer patients compared with those obtained from ascites of the d-LC patients. Other molecules were faintly expressed or absent even in the malignant ascites. Conclusions: We first demonstrated abundant expression of CD133, a human pancreatic CSC marker, in exosomes derived from ascites of patients with the disease. The finding suggests that exosomal CD133 might be a potential biomarker for chemoresistance and prognosis of the patients. Citation Format: Takahiko Sakaue, Hironori Koga, Masaru Fukahori, Yasuko Imamura, Toru Nakamura, Yoshinobu Okabe, Yu Ikezono, Fumitaka Wada, Hideki Iwamoto, Atsutaka Masuda, Tomoyuki Ushijima, Keisuke Miwa, Tatsuyuki Kakuma, Osamu Tsuruta, Takuji Torimura. Expression of cancer stem cell-associated proteins in exosomes derived from ascites of patients with advanced pancreatic cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3955.