Predicting distant metastasis and chemoresistance using plasma miRNAs

In the clinic, predicting metastasis and chemoresistance takes high priority, but has not been well established. This study seeks to investigate whether dynamically monitoring serum microRNAs (miRNAs) can help predict metastasis, chemoresistance, and prognosis of colorectal cancer. Serum miR-155, miR-200c, and miR-210 levels in 15 patients with colon cancer were measured by real-time PCR at different time points post surgery and chemotherapy for 3 years. Significant increases in miR-155, miR-200c, and miR-210 levels were observed in the serum and tumor tissues of colon cancer patients compared to that of healthy subjects. After surgery and chemotherapy, the serum levels of these miRNAs in patients with good prognosis returned to normal levels found in healthy controls during the 3-year follow-up. In patients with recurrence and distant metastasis, serum miR-155, miR-200c, and miR-210 levels remained at an elevated level or became elevated again after a short period of decline. In patients with good response to chemotherapy for metastatic tumors, re-elevation of miR-155 was not significant compared to miR-200c and miR-210. In contrast, miR-155 re-elevated more significantly in patients not sensitized to chemotherapy than miR-200c and miR-210. Our study suggests that re-elevation or sustained elevation of serum miR-155 level after surgery and chemotherapy is a sign of chemoresistance in colon cancer, while high and/or re-elevated miR-155, miR-200c, and miR-210 levels implicate local recurrence and distant metastasis as well as poor prognosis.