The clinical application value of human serum exosomal CEA in the diagnosis of colorectal cancer

Objective To isolate and identify exosomes from human serum, explore the feasibility of exosomal CEA for the diagnosis of colorectal cancer. Methods Retrospective study.64 cases with colorectal cancer patients(41 cases with normal CEA results and 23cases with high CEA results), 20 cases with benign colorectal diseases patients and 40 cases with healthy people of department of physical examination from October 2015 to December 2016 in Tongji Hospital of Tongji University. Exosomes were isolated from these serum using ExoQuick, and then identified by using transmission electron microscopy, and Western Blot for morphology and molecular phenotype.The serum level of CEA and exosomal CEA was measureed by enzyme linked immunosorbent assay (ELISA). The diagnostic efficacy of serum Exosomal CEA concentration in the colorectal cancer by using U test and the subject work characteristic curve (ROC). Results Exosomes in human serum was successfully extracted with ExoQuick kit.Exosomal CEA concentration in 64 cases with colorectal cancer patients (1 056.36-28 637.78)pg/ml was significantly higher than in cases with benign colorectal diseases patients (394.61-2 437.83)pg/ml and healthy controls(610.89-2 076.70)pg/ml(U=124.000, U=119.000, P<0.01). Exosomal CEA concentration in 41 colorectal cancer patients with normal serum CEA concentration(1 056.36-5 832.07)pg/ml was significantly higher than in benign colorectal diseases patients and healthy controls(U=113.000, U=119.000; P<0.01). ROC analysis of exosomal CEA yielded an AUC(area under the ROC curve)of 0.954(95% CI=0.919-0.988), which was higher than the serum CEA.The area under the ROC curve of serum Exosomal CEA concentration for colorectal cancer diagnosis is 0.954(95% CI=0.919-0.988), which is superior to the serum CEA concentration[0.636 (95% CI=0.531-0.742)]. Conclusions Isolation and detection of serum Exosomal CEA concentrations have a good diagnostic efficacy in colorectal cancer. It′s possible to be a marker for early diagnosis of colorectal cancer.(Chin J Lab Med, 2018, 41: 503-508) Key words: Colorectal neoplasms; Exosomes; Carcinoembryonic antigen; Biomarkers, Tumor