Extracellular miR-224 as a prognostic marker for clear cell renal cell carcinoma

Abstract

// Nakanori Fujii 1 , Hiroshi Hirata 1, 2 , Koji Ueno 3 , Junichi Mori 1 , Shintaro Oka 1 , Kosuke Shimizu 1 , Yoshihisa Kawai 1 , Ryo Inoue 1 , Yoshiaki Yamamoto 1 , Hiroaki Matsumoto 1 , Tomoyuki Shimabukuro 1, 4 , Koichi Udoh 5 , Yoshinobu Hoshii 6 , Rajvir Dahiya 7 and Hideyasu Matsuyama 1 1 Department of Urology, Graduate School of Medicine, Yamaguchi University, Ube, Yamaguchi 755-8505, Japan 2 Department of Urology, Ube Memorial Hospital, Ube, Yamaguchi 755-0051, Japan 3 Center for Regenerative Medicine, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi 755-8505, Japan 4 Department of Urology, Ube Kosan Central Hospital, Ube, Yamaguchi 755-0151, Japan 5 Institute for Biomedical Research and Education, Yamaguchi University Science Research Center, Ube, Yamaguchi 755-8505, Japan 6 Department of Diagnostic Pathology, Yamaguchi University Hospital, Ube, Yamaguchi, 755-8505, Japan 7 Department of Urology, San Francisco Veterans Affairs Medical Center and University of California, San Francisco, California 94121, USA Correspondence to: Hideyasu Matsuyama, email: hidde@yamaguchi-u.ac.jp Keywords: microRNA; miR-224; exosome; clear cell renal cell carcinoma Received: July 19, 2017      Accepted: October 27, 2017      Published: November 15, 2017 ABSTRACT Exosome-miRNAs (exo-miR) have recently been identified as modulators of cancer progression and distant metastasis. We previously found that intracellular miR-224 is up-regulated and significantly related to cancer invasion and metastasis in clear cell renal cell carcinoma (ccRCC). We therefore investigated the role of exosome miR-224 in ccRCC and explored the interaction between intra- and extracellular miR-224 in renal cell carcinoma. To validate the method for isolating exosomes from blood samples or cell culture media, we examined exosome morphology using transmission electron microscope (TEM). We investigated the relationship between exo-miR-224 expression and patient prognosis in 108 ccRCC patients. We isolated exosomes from a metastatic renal cancer cell line and tested their effects on a primary renal cancer cell line with several functional analyses. We found that the high expression level exo-miR-224 group has significantly shorter progression-free survival, cancer-specific survival, and overall survival compared with the low expression group. In multivariate analysis, a high level of exo-miR-224 was a significant risk factor related to all prognoses investigated. After adding exosomes from a metastatic RCC cell line to a primary RCC cell line, cell proliferation and invasion were increased while the percentage of apoptotic cells was significantly decreased. Intracellular levels of miR-224 were significantly up-regulated in the primary renal cancer cell line. Extracellular miR-224 in exosomes impacts on patient prognosis and is a potential prognostic biomarker for ccRCC patients.