Enhanced miR-182 transcription is a predictor of poor overall survival in colorectal adenocarcinoma patients

Background: Colorectal cancer is the second most frequent cause of cancer-related death in the developed world. Recent studies have tried to associate colorectal cancer with the aberrant expression of several microRNAs. The aim of the present study was the development of a highly sensitive quantitative real-time PCR which can be used to evaluate the miR-182 expression levels in colorectal adenocarcinoma and adjacent non-cancerous tissue specimens and associate them with several clinicopathological characteristics, aiming to examine the prognostic potential of miR-182. Methods: Total RNA was isolated from 116 malignant colorectal adenocarcinoma specimens and 60 paired non-cancerous tissues. Then, polyadenylation of 2 g total RNA by poly(A) polymerase and reverse transcription with suitable oligo-dT-adapter followed. miR-182 levels were quantified by real-time PCR based on SYBR Green chemistry. The results were analyzed by the comparative quantification cycle method and by extensive biostatistical analysis. Results: miR-182 was found to be significantly upregulated in colorectal adenocarcinoma specimens compared to their non-cancerous counterparts (p<0.001). miR-182 expression increases as the histological grade increases (p=0.013). miR-182 overexpression is associated with high depth of tumor invasion, positive regional lymph node status, and advanced TNM stage of patients. Therefore, miR-182 is an unfavorable prognostic marker in colorectal adenocarcinoma, predicting poor overall survival (p=0.007). Most importantly, miR-182 expression retained its unfavorable prognostic significance among patients with well-or moderately differentiated colorectal adenocarcinoma (p=0.006) and among metastasis-free patients (p=0.025). Conclusions: The increased levels of the oncogene-like miR-182 increase the risk for disease progression and predict poor overall survival for colorectal adenocarcinoma patients.