Abstract: Objective To investigate the expression level of miR-590-3p in plasma exosomes of patients with colorectal cancer (CRC) and its clinical prognostic value. Methods The plasma samples of 97 CRC patients, hospitalized and received surgical treatment in Lichuan People's Hospital or Zhongnan Hospital of Wuhan University from January 2015 to December 2015, and 20 healthy controls were collected. Exosome were extracted from the plasma by ExoQuick Exosome Precipitation Solution kit, its morphology and particle size were identified by transmission electron microscopy and NanoSight nanoparticle analyzer, and the expression of exosome specific marker proteins CD63 and TSG101 were detected by Western blot. RT-qPCR was used to detect the expression of miR-590-3p in plasma exosome, and its relationship with clinicopathological features of CRC patients was analyzed. The prognostic factors of CRC patients were analyzed by multivariable Cox regression model, and the overall survival of patients in the miR-590-3p high expression group and the low expression group was analyzed by Kaplan-Meier method. Results The particle size of exosome isolated from plasma of 97 CRC patients and 20 healthy controls was about 100 nm. The expression of CD63 and TSG101 could be detected by Western blot, and the content of exosomes in the plasma of CRC patients was higher than that of healthy controls. RT-qPCR showed that the expression level of miR-590-3p in the plasma exosomes of CRC patients was higher than that of healthy controls (7.163±0.147 vs 1.339±0.161, P<0.001), and its expression level was related to tumor differentiation, lymph node metastasis, lymph vascular invasion and TNM stage of CRC patients(all P<0.05). Survival analysis showed that the overall survival of patients with high miR-590-3p expression in plasma exosomes was shorter than those with low expression (P=0.003). Furthermore, the multivariable Cox regression model analysis showed that high expression of miR-590-3p in plasma exosomes was an independent risk factor for prognosis in patients with CRC (HR=1.954, 95%CI: 1.271-3.524, P=0.032). Conclusions The expression of miR-590-3p is up-regulated in the plasma exosomes of patients with CRC, and closely related to tumor progression and poor prognosis, which may be an independent biomarker for CRC prognosis assessment.

Key words:  Colorectal cancer, Exosomes, miR-590-3p, Prognosis