Abstract: Objective To investigate the prognostic value of mesenchymal circulating tumor cells ( ^M CTCs) in colon cancer (CC). Methods A total of 115 CC patients hospitalized in the Department of Gastrointestinal Surgery, Zhongnan Hospital of Wuhan University from January 2015 to June 2016 were selected as the research objects. Within the 24 h after admission, 2. 5 mL of peripheral venous blood was administered through peripheral veins into EDTA-containing tube. The number of ^M CTCs in blood sample was detected by using CTCBIOPSY ^® which was previously developed by our team combined with the immunofluorescence ( IF) staining, and the correlation between the number of ^M CTCs and clinicopathologic factors was analyzed. Furthermore, Kaplan-Meier survival curve and COX regression analysis were used to explore the relationship between ^M CTCs and patients’ prognosis. Results There was no significant difference in the number of ^M CTCs in peripheral blood of patients with different tumor locations, but the number of ^M CTCs in patients with low and middle tumor differentiation was significantly higher than that of patients with high tumor differentiation. Moreover, the number of ^M CTCs in peripheral blood of patients with stage Ⅲ was significantly higher than that of patients with stage Ⅱ and stage Ⅰ. Further analysis showed that ^M CTCs positive were correlated with tumor differentiation grade ( P = 0. 013 ), depth of tumor invasion (P = 0. 010), lymph node metastasis (P = 0. 043), TNM stage (P < 0. 001), vascular infiltration (P< 0. 001), nerve invasion ( P = 0. 004) and CEA level ( P < 0. 001). Survival analysis showed that the overall survival time of patients with ^M CTCs positive was significantly lower than that of patients with ^M CTCs negative (χ² = 9. 726, P = 0. 002), and ^M CTCs positive was an independent risk factor for overall survival of patients with CC (HR = 1. 752, 95 % CI: 1. 104 ~ 3. 871, P = 0. 015). Conclusion Mesenchymal CTCs in the peripheral blood of patients with CC are closely related to the malignant progression of tumors and poor prognosis of patients, which is expected to be a novel biomarker for the clinical prognosis evaluation. 

Key words: colon cancer, circulating tumor cells, epithelial-mesenchymal transition, prognosis