MicroRNAs are novel biomarkers for the detection of colorectal neoplasia and high risk Dukes’ B cancers

Aims: This study aimed to identify which circulating miRNAs can be used for the early detection of colorectal cancers (CRCs) and to assess the utility of tissue miRNAs combined with common gene mutations, to predict the development of metastasis in patients with Dukes’ B CRCs. Methods: microRNA (miRNA) expression profiling was performed for total RNA extracted from plasma samples (colonoscopy negative controls=11, adenomas=9, carcinomas=12) and formalin-fixed paraffin embedded (FFPE) matched paired cancerous with adjacent normal tissue (n=20, 5 cases from each group of Dukes’ A, Dukes’ B with metastasis during 5 year follow up, Dukes’ B without metastasis during 5 year follow up, and Dukes’ C) using Taqman® MicroRNA Array, Megaplex™ RT and pre-amplification primers Human Pool A v.2.1 and Pool B v.2.0. Discriminatory miRNAs identified from plasma and tissue expression profiles were validated further on cohorts of plasma (n=190) and FFPE tissues (n=72). Three common gene mutations (KRAS, BRAF and PIK3CA) were analysed in DNA extracted from FFPE cancer tissue. miRNA expression analysis was applied to circulating exosomes to quantify CRC-related exosomal miRNAs. Results: Receiver operating characteristics analysis showed miR-135b was associated with an area under the curve value of 0.82 (95% CI: 0.71-0.92), with 80% sensitivity and 84% specificity for the detection of adenomas and carcinomas. miR-135b was also detectable in immunoaffinity-isolated plasma exosomes from patients with CRC. No significant differences were noted for mutation status and the development of metastasis. Expression levels of miR-135b and miR-15b were significantly associated with Dukes’ B cancers tissue and the development of metastasis. Conclusions: miR-135b is a novel diagnostic and prognostic marker. Its expression levels in blood and tissue can be used for the early detection of CRCs and to predict the development of metastasis in Dukes’ B cancers.