Abstract

Colorectal cancer (CRC) is known as the third common cancer worldwide and an important public health problem in different populations. Several genetics and environmental risk factors are involved in the development and progression of CRC including chromosomal abnormalities, epigenetic alterations, and unhealthy lifestyle. Identification of risk factors and biomarkers could lead to a better understanding of molecular pathways involved in CRC pathogenesis. MicroRNAs (miRNAs) are important regulatory molecules which could affect a variety of cellular and molecular targets in CRC. A large number of studies have indicated deregulations of some known tissue-specific miRNAs, for example, miR-21, miR-9, miR-155, miR-17, miR-19, let-7, and miR-24 as well as circulating miRNAs, for example, miR-181b, miR-21, miR-183, let-7g, miR-17, and miR-126, in patients with CRC. In the current review, we focus on the findings of preclinical and clinical studies performed on tissue-specific and circulating miRNAs as diagnostic biomarkers and therapeutic targets for the detection of patients at various stages of CRC. CRC is ranked among the most common types of cancer and a leading cause of cancer-related death worldwide. Early diagnosis of CRC is a pre-requisite for proper management of the patient and increasing survival. Several lines of evidence have indicated that patients with CRC have a poor prognosis due to the lack of simple, reliable, and non-invasive diagnostic tools for the early stage of the disease. Currently, colonoscopy is the gold standard for early diagnosis of CRC but its invasiveness is a big limitation. MicroRNAs have emerged as non-coding RNAs which have the potential to be used as promising candidates for the diagnosis of CRC patients. Moreover, exosomal biomarkers including miRNAs, proteins and mRNAs could open new horizons for the diagnosis of CRC.