MicroRNAs in colorectal cancer: A new and promising early diagnostic option

In spite of advances in diagnostic techniques, surgery, chemotherapy and radiotherapy, colorectal cancers remain undefeated. In the absence of screening, colorectal cancers are diagnosed in an advanced stage when regional and distant metastasis is present. Hence, the hope for control is primary prevention or early diagnosis. Western lifestyle and diet have been implicated in the causation of colon cancers. However, it is still a controversy whether this is due to excess calories, high fat content, genotoxic agents, or lack of protective agents present in vegetables and fruits. Therefore, recommending a specific cancer prevention diet can have fallacies. In this context reduction in cancer mortality can be achieved by screening population at high risk. The colorectal cancers require investigative modalities like colonoscopy, sigmoidoscopy or fecal occult blood testing (FOBT) for screening. Colonoscopy is the most sensitive and specific of all the available colorectal screening tests, whereas the sensitivity and specificity for FOBT and sigmoidoscopy are much lower. Although performance of FOBT is relatively inexpensive, sigmoidoscopy and colonoscopy must be performed by trained endoscopists and are more expensive. Moreover, lack of awareness that colorectal cancer is a prevalent and serious disease, concerns about the potential discomforts of colorectal cancer procedures or of the preparations for screening appear to be potential barriers for colorectal cancer screening. MicroRNAs (miRNAs) have roles in colon carcinogenesis; therefore, may be useful biomarkers for colorectal carcinoma (CRC). They are short ribonucleic acid (RNA) molecules having very few nucleotides compared with other RNAs. miRNAs have been studied intensively in the field of oncological research, and emerging evidence suggests that altered miRNA regulation is involved in the pathogenesis of cancers. This review summarizes the use of miRNA in the early diagnosis of colorectal cancers.