Serum MicroRNAs as Diagnostic Biomarkers of Colorectal Cancer

Colorectal cancer (CRC) is the second commonest cause of cancer deaths and the third most common cancer worldwide. Five year survival of patients with stage 1 CRC is 92%, and decreases to 10% at stage 4 CRC. So, CRC diagnosing at an early stage is the most important factor influencing disease prognosis. Most CRC patients are diagnosed after being symptomatic, but studies show that once the symptoms are present it mostly signifies late-stage disease. colonoscopic screening of asymptomatic patients has been shown to pick up early-stage CRC. However, this is limited by cost issues and patient attitudes. Therefore, more efforts could be done to view to early diagnosis of CRC in asymptomatic patient. Biomarkers are molecules that can serve as signals of disease activity and pathological processes. CRC biomarkers can help in early diagnosis. MicroRNAs (miRNAs) are non-coding molecules that impact the expression of target genes in cell. Also, they exist in highly stable, cell free form in peripheral blood. They are detected by quantitative real time polymerase chain reaction (qRT-PCR). Data also shows that certain miRNAs are elevated in the plasma and tissues of CRC patients and decrease in plasma levels after operative treatment. There are over 2000 different miRNAs and they are estimated to regulate 30% of the human genome. miRNA dysregulation is also associated with multiple cancers. miRNAs seem to show significant promise with high sensitivity and specificity for CRC, but with limiting factors of limited data for high risk polyps and significant heterogeneity in test media and non-standardisation of test panels. Further research would be required to bridge these knowledge gaps. Interestingly, miR-15b and miR-21 appears to be the best diagnostic accuracy values for CRC.