microsatelliteinstabiliteettiin

Microsatellite instability, often abbreviated as MSI, refers to a condition where the normal DNA repair mechanism for short, repetitive DNA sequences called microsatellites is faulty. Microsatellites are short stretches of DNA, typically 1-6 base pairs long, that are repeated many times. They are found throughout the genome and are important for various cellular functions.

In healthy cells, enzymes called mismatch repair (MMR) proteins are responsible for identifying and correcting errors that occur during DNA replication in these microsatellite regions. When these MMR proteins are not functioning correctly, errors in microsatellite length can accumulate. This accumulation of changes in microsatellite length is known as microsatellite instability.

MSI can occur sporadically due to acquired mutations in MMR genes or can be inherited in certain genetic conditions, such as Lynch syndrome. The presence of MSI is particularly significant in cancer research. A high degree of MSI, or MSI-high (MSI-H), is found in a subset of various cancers, including colorectal, endometrial, and gastric cancers.

The detection of MSI in tumors is clinically relevant. It can indicate a predisposition to developing cancer and can also influence treatment decisions. For example, tumors with MSI-H may respond differently to certain chemotherapies and immunotherapies. Therefore, MSI testing is a diagnostic tool used in the management of some cancer types.