The Role of MicroRNA-21 in Colorectal Cancer and Its Potential Value as a Predictive, Diagnostic and Prognostic Biomarker: A Review Article

Colorectal cancer (CRC) is one of the most common types of cancers worldwide. Despite the improved therapeutic and diagnostic strategies and screening programs, morbidity and mortality of CRC is still considerable. Currently, most common approaches for diagnosis of CRC are colonoscopy and fecal occult blood test (FOBT). Because of the invasive nature of colonoscopy and low sensitivity of FOBT, it is essential to find precise and noninvasive methods for early diagnosis, monitoring, and control of colorectal cancer. In recent years, there has been growing interest in finding sensitive and non-invasive molecular biomarkers by evaluating expression profiles of miRNAs in patients with colorectal cancer. Many studies have shown the important role of microRNAs in regulating the expression of genes involved in tumorigenesis, which has led researchers to evaluate their ability in diagnosis and treatment of various cancers such as colorectal cancer. In this regard, miR-21 was studied in many researches. miR-21 is one of the earliest identified cancer-promoting ‘oncomiRs’, targeting numerous tumor suppressor genes associated with prolifera tion, apoptosis, and invasion. Overexpression of miR-21 is observed in colorectal cancer and some other cancers. Recent studies have focused on the diagnostic and prognostic value of miR-21 and its implication in drug resis tance of human cancers. The present study is a review of recent findings on the role of miR-21 in the regulation of target genes involved in colorectal carcinogenesis and its potential as a diagnostic and prognosis biomarker in this cancer.