Circulating Exosomal microRNAs as Biomarkers of Colon Cancer

Hiroko Ogata-Kawata,Hikaru Sonoda,Naoto Tsuchiya,Jun Yokota,Hiroyuki Okamoto,Koh Furuta,Masatoshi Watanabe,Hideki Ohta,Daisuke Kurioka,Yasuhide Yamada,Yoshitaka Honma,Takashi Kohno,Masashi Izumiya,Toshiaki Gunji,Hitoshi Nakagama,Tadayuki Akagi

doi:10.1371/journal.pone.0092921

Abstract

PurposeExosomal microRNAs (miRNAs) have been attracting major interest as potential diagnostic biomarkers of cancer. The aim of this study was to characterize the miRNA profiles of serum exosomes and to identify those that are altered in colorectal cancer (CRC). To evaluate their use as diagnostic biomarkers, the relationship between specific exosomal miRNA levels and pathological changes of patients, including disease stage and tumor resection, was examined.Experimental DesignMicroarray analyses of miRNAs in exosome-enriched fractions of serum samples from 88 primary CRC patients and 11 healthy controls were performed. The expression levels of miRNAs in the culture medium of five colon cancer cell lines were also compared with those in the culture medium of a normal colon-derived cell line. The expression profiles of miRNAs that were differentially expressed between CRC and control sample sets were verified using 29 paired samples from post-tumor resection patients. The sensitivities of selected miRNAs as biomarkers of CRC were evaluated and compared with those of known tumor markers (CA19-9 and CEA) using a receiver operating characteristic analysis. The expression levels of selected miRNAs were also validated by quantitative real-time RT-PCR analyses of an independent set of 13 CRC patients.ResultsThe serum exosomal levels of seven miRNAs (let-7a, miR-1229, miR-1246, miR-150, miR-21, miR-223, and miR-23a) were significantly higher in primary CRC patients, even those with early stage disease, than in healthy controls, and were significantly down-regulated after surgical resection of tumors. These miRNAs were also secreted at significantly higher levels by colon cancer cell lines than by a normal colon-derived cell line. The high sensitivities of the seven selected exosomal miRNAs were confirmed by a receiver operating characteristic analysis.ConclusionExosomal miRNA signatures appear to mirror pathological changes of CRC patients and several miRNAs are promising biomarkers for non-invasive diagnosis of the disease.

Highlights

Colorectal cancer (CRC) is one of the major causes of cancerrelated deaths worldwide [1]
The high sensitivities of the seven selected exosomal miRNAs were confirmed by a receiver operating characteristic analysis
The results presented here demonstrate that exosomal miRNA signatures reflect pathological changes in CRC patients and are applicable for the development of diagnostic strategies for detection of primary CRCs

Summary

Introduction

Colorectal cancer (CRC) is one of the major causes of cancerrelated deaths worldwide [1]. Systematic methods for diagnosing pathological conditions might contribute to a high detection rate of patients at early stages of CRC, leading to a reduction in mortality rates. Implementation of the fecal occult blood test and flexible sigmoidoscopy as screening methods has reduced CRC mortality [2,3]. These techniques have inherent limitations; the sensitivity of detection of the fecal occult blood test is fairly low and flexible sigmoidoscopy is invasive and uncomfortable for patients. The sensitivity of these markers for the detection of CRC is low, especially in the early stages of the disease [4]. There is a need for the development of CRC-specific diagnostic markers for rapid, noninvasive, and highly sensitive screening of patients

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