Clinicopathological and prognostic significance of the microRNA processing enzyme DICER1 mRNA expression in colorectal cancer patients.

The cytoplasmic ribonuclease DICER1 is one of the key enzymes in microRNA (miRNA) processing, essential for the production of mature miRNA. The effect of DICER1 expression in tumor cells on the prognosis of patients with several cancers has been examined with controversial results in various cancer types. In particular, the clinical significance of DICER1 expression in colorectal cancer (CRC) patients has yet to be determined. The aim of this study was to evaluate the correlation between the DICER1 mRNA levels and the clinicopathological characteristics and prognostic significance in CRC patients. Tumor and normal adjacent tumor tissues from 260 patients with CRC (Dukes' stage A: 40 cases, Dukes' B: 68 cases, Dukes' C: 88 cases and Dukes' D: 64 cases) were examined. The DICER1 mRNA levels were measured using the TaqMan real-time reverse transcription polymerase chain reaction (RT-PCR) method. The expression levels of DICER1 mRNAs showed a significant decrease in CRC tissues as compared to normal ones (P=0.039). A statistically significant association was observed between DICER1 mRNA expression and tumor size, depth of invasion, lymph node metastasis, lymphatic invasion and Dukes' stage. In Kaplan-Meier survival curve analysis, overall survival (OS) and disease-free survival (DFS) rates of patients with a low DICER1 mRNA expression were significantly worse compared to patients with a high DICER1 mRNA expression (OS P<0.001; DFS P<0.001). In the Cox multivariate analysis, DICER1 mRNA expression in CRC tissues was identified as an independent prognostic factor for OS [hazard ratio (HR), 0.30; 95% confidence interval (CI), 0.13-0.64; P=0.001] and DFS (HR, 0.23; 95% CI, 0.10-0.48; P=0.001). This study demonstrated that a reduced DICER1 mRNA expression is associated with poor prognosis in CRC patients.