Clinical MSI Testing IVD

MSI status is a biomarker that is used to identify candidates for further diagnostic testing for Lynch Syndrome. Lynch syndrome is a genetic predisposition to cancer caused by autosomal dominant mutations to the major mismatch repair genes MLH1, MSH2, MSH6 or PMS2 as well as the EPCAM gene that inactivates MSH2. Most often associated with colorectal cancer, Lynch syndrome also increases the lifetime risk of several other cancers including endometrial, ovarian and stomach cancer.

MSI screening can be used to characterize tumors and guide therapeutic choices for MSI-High cancer types. Tumors with MSI-High status have been shown to respond to immune checkpoint inhibitor (ICI) therapies. Tumors with defects in the expression of functional MMR (dMMR) proteins often have somatic mutations that produce “foreign” proteins that can be detected by the immune system. As a result, these tumors are effective at priming an immune response and subsequently susceptible to immunotherapies. Because MSI can be the first evidence of an MMR deficiency, MSI-High status is predictive of a positive response to immunotherapies such as immune checkpoint blockade inhibitors.

Learn more about MSI testing in the Microsatellite Instability Resource Center.