MicroRNA Biomarkers in IBD-Differential Diagnosis and Prediction of Colitis-Associated Cancer

Inflammatory bowel disease (IBD) includes Crohn's disease (CD) and ulcerative colitis (UC). These are chronic autoimmune diseases of unknown etiology affecting the gastrointestinal tract. The IBD population includes a heterogeneous group of patients with varying disease courses requiring personalized treatment protocols. The complexity of the disease often delays the diagnosis and the initiation of appropriate treatments. In a subset of patients, IBD leads to colitis-associated cancer (CAC). MicroRNAs are single-stranded regulatory noncoding RNAs of 18 to 22 nucleotides with putative roles in the pathogenesis of IBD and colorectal cancer. They have been explored as biomarkers and therapeutic targets. Both tissue-derived and circulating microRNAs have emerged as promising biomarkers in the differential diagnosis and in the prognosis of disease severity of IBD as well as predictive biomarkers in drug resistance. In addition, knowledge of the cellular localization of differentially expressed microRNAs is a prerequisite for deciphering the biological role of these important epigenetic regulators and the cellular localization may even contribute to an alternative repertoire of biomarkers. In this review, we discuss findings based on RT-qPCR, microarray profiling, next generation sequencing and in situ hybridization of microRNA biomarkers identified in the circulation and in tissue biopsies.