Clinicopathological and Prognostic Value of MicroRNA-21 and MicroRNA-155 in Colorectal Cancer

Objective: The clinical significance of microRNA-21 (miR-21) and miR-155 in colorectal cancer (CRC) patients remains elusive. In this study, we established the prognostic value of miR-21 and miR-155 using clinical samples from CRC patients. Furthermore, relationships between these microRNAs and target genes (PDCD4 and TP53INP1 mRNAs) were examined. Methods: miR-21 and miR-155 expression was assessed in tumor tissue and in adjacent normal tissue of 156 CRC patients by TaqMan MicroRNA assays, and PDCD4 and TP53INP1 mRNA levels were measured by quantitative real-time reverse transcriptase PCR (RT-PCR). Results: High miR-21 expression was significantly associated with venous invasion, liver metastasis and tumor stage, and high miR-155 expression was significantly correlated with lymph node metastases. The overall (OS) and disease-free survival (DFS) rates of patients with high miR-21 expression were significantly worse than those of patients with low miR-21 expression. The OS and DFS of patients with high miR-155 expression were also significantly worse than those in patients with low miR-155 expression. miR-21 and miR-155 expression levels in CRC tissue were independent prognostic factors for OS and DFS. Significant inverse correlations were demonstrated between miR-21 and PDCD4 mRNA, and miR-155 and TP53INP1 mRNA. Conclusion: Increases in miR-21 and miR-155 expression may represent effective biomarkers for the prediction of a poor prognosis.