MiR-486-5p Downregulation Marks an Early Event in Colorectal Carcinogenesis.

BACKGROUND: MicroRNAs are dysregulated in colorectal cancer and subsets correlated with advanced tumor stage and metastasis. Data are lacking on microRNA dysregulation from early to late-stage disease. OBJECTIVE: The purpose of this study was to identify a microRNA signature associated with the primary tumor and metastatic site in stage IV disease and to examine whether the signature is evident in earlier stages. DESIGN: A microRNA profile was generated and then explored in normal colon tissue (n = 5), early stage (stage I and II; n = 10), and late-stage (stage III and IV; n = 14) colorectal primary tumors via polymerase chain reaction to delineate molecular events that may promote colorectal carcinogenesis. SETTING: Genome-wide microRNA expression profiling was performed. PATIENTS: A total of 14 patient-matched stage IV primary colorectal cancer tumors and corresponding liver metastases were included. MAIN OUTCOME MEASURES: MicroRNA array technology was used to identify microRNA expression-predictive metastatic potential in the primary tumor. RESULTS: A distinct 9-member signature group of microRNAs was concurrent in stage IV primary colorectal cancer and their corresponding liver metastases, when compared with surrounding unaffected colon and liver tissue (microRNA-18b, microRNA-93, microRNA-182, microRNA-183, microRNA21, microRNA-486-5p, microRNA-500a, microRNA-552, and microRNA-941). Of the microRNA panel, only microRNA486-5p was differentially expressed in early stage colorectal cancer samples compared with normal tissue (p = 0.001) and additionally differentially expressed between late-stage colorectal cancer samples and normal tissue (p < 0.01). LIMITATIONS: Our microRNA profile was generated in a small subset of patients and will require validation in more samples. CONCLUSIONS: We identified a distinct microRNA signature in primary colon and matched metastatic disease. On additional investigation, 1 microRNA was differentially expressed in both early and late-stage cancer patient samples, and it may herald an early event in colorectal carcinogenesis. This study warrants additional investigation with a larger patient cohort to better understand the effect of microRNAs in carcinogenesis. See Video Abstract at http://links.lww.com/DCR/A723.