Upregulated miR-16 expression is an independent indicator of relapse and poor overall survival of colorectal adenocarcinoma patients

Background: Colorectal adenocarcinoma is one of the most common malignant tumors of the gastrointestinal tract and the second leading cause of cancer-related deaths among adults in Western countries. miR-16 is heavily involved in cancer progression. In this study, we examined the potential diagnostic and prognostic utility of miR-16 expression in colorectal adenocarcinoma. Methods: Total RNA was extracted from 182 colorectal adenocarcinoma specimens and 86 non-cancerous colorectal mucosae. After polyadenylation of 2 mu g total RNA by poly(A) polymerase and subsequent reverse transcription with an oligo-dT adapter primer, miR-16 expression was determined using an in-house developed reverse transcription quantitative real-time PCR method, based on SYBR Green chemistry. SNORD43 (RNU43) and SNORD48 (RNU48) were used as reference genes. Next, we performed extensive biostatistical analysis. Results: miR-16 was shown to be significantly upregulated in colorectal adenocarcinoma specimens compared to non-cancerous colorectal mucosae, suggesting its potential exploitation for diagnostic purposes. Moreover, high miR-16 expression predicts poor disease-free survival (DFS) and overall survival (OS) of colorectal adenocarcinoma patients. Multivariate Cox regression analysis confirmed that miR-16 overexpression is a significant unfavorable prognosticator in colorectal adenocarcinoma, independent of other established prognostic factors, radiotherapy, and chemotherapy. Interestingly, miR-16 overexpression retains its unfavorable prognostic value in patients with advanced yet locally restricted colorectal adenocarcinoma that has not grown through the wall of the colon or rectum (T3) and in those without distant metastasis (M0). Conclusions: Overexpression of the cancer-associated miR-16 predicts poor DFS and OS of colorectal adenocarcinoma patients, independently of clinicopathological factors that are currently used for prognostic purposes.