Microsatellite Instability Analysis (MSI)

Microsatellite instability has become an increasingly relevant tool in genetic and immuno-oncology research. Deficiencies in DNA mismatch repair (MMR) can be caused by hereditary, germline mutations or hypermethylation. Either mechanism disrupts expression of functional MMR proteins, allowing transcription errors to accumulate across the genome. Global genomic mutations disrupt normal cellular function, which leads to unchecked growth and cancers but also produces novel proteins. These “foreign” proteins can be immunogenic, recruiting immune effector cells to that tissue. Instability, or mutations, of mononucleotide repeat microsatellite sequences are particularly sensitive to transcription errors and can be the first evidence of an MMR deficiency.