Detection of Microsatellite Instability by High-Resolution Melting Analysis in Colorectal Cancer

Colorectal cancer is the third most common cancer worldwide. Microsatellite instability (MSI) is a molecular marker of a deficient mismatch repair (MMR) system and happens in almost 15% of colorectal cancers. Because of The wide frequency of MSI+ colorectal cancer in Iran compared to other parts of the world, the importance of screening for this type of cancer is highlighted. The most common MSI detection techniques is a fluorescent PCR-based in which fragments are analyzed by capillary electrophoresis (CE). This technique is very time-consuming, difficult, and expensive. Here, we sought to develop and evaluate a proper method with high accuracy, specificity and sensitivity to screen the MSI+ colorectal cancer. A high-resolution melting (HRM) analysis procedure is relying on the analysis of the melting curve attributes. Low cost, feasibility, high specificity and sensitivity are outstanding attributes of HRM analysis.  To this end five mononucleotide microsatellite markers including, BAT-26, BAT-25, NR-24, NR-21, and NR-27 in 25 archival CRC tumor tissue samples were compared with normal tissue adjacent using high resolution melting (HRM) method. The specificity and sensitivity of BAT25 with HRM method were 100 % in comparison with CE while other markers lower sensitivity. However, when all the markers were considered together, the sensitivity and specificity became 100%. The number of MSI+ samples was 56%, which shows a higher ratio than previous Iranian studies. The highest microsatellite instability was related to BAT26, (52%). The HRM method is much simpler and more cost-effective than current MSI techniques, and its sensitivity and accuracy are comparable, and can be replaced in cases where capillary electrophoresis is not available.