Significance of Microsatellite Instability in Colorectal Carcinoma- A Complete Review

Abstract

The microsatellite instability (MSI-H) or mismatch repair deficient (dMMR) colorectal tumors recently have been reported that can benefit from immunotherapy, and MSI can be used as a genetic instability of a tumor detection index. Many studies have shown that there are many heterogeneous phenomena in patients with MSI tumors in terms of immunotherapy, prognosis and chemotherapy sensitivity. Here we mainly review the research results of MSI detection methods, its mechanisms, occurrence and its relationship with related tumors, aiming in such a way for brief analysis of the micro satellite instability. Microsatellites (MS) are the repeated sequences of DNA that play an important role in maintaining the tissue morphology. Any mutation of the DNA or chromosomes, lead to the instability of the microsatellites, thereby causing the microsatellite instability. There are three types of microsatellite instability (MSI). High microsatellite instability (MSI-H), low microsatellite instability (MSI-L) and microsatellite stability (MSS). Recent clinical research tends to classify MSS-L and MSS as similar. Microstaellite instability plays an important role in colorectal carcinoma. Based on different molecular mechanisms, MSI in colorectal cancer can be divided into colorectal cancer (CRC) with no obvious family genetic history and Lynch syndrome with non-polyposis with family genetic history. Lynch syndrome is an autosomal dominant disorder and syndrome caused by mutations in MMR strains, and it can also cause tumors in other parts of the colon and rectum. With the recent development of MSI detection technology and immunosuppressant in tumor therapy, researchers found that MSI-H tumors respond well to immunotherapy. There are several methods to detect the microsatellite instability. 1. Next Generation sequencing (NGS), 2. Fluoresence multiplex PCR and capillary electrophoresis. 3. Immunohistochemistry. 4. Single molecule- molecular inversion probes (SmMIP). The main mechanism of MSI includes, Slipped strand mispairing, MMR deficient.