mikrosatellitinstabilitet

Mikrosatellitinstabilitet, also known as microsatellite instability (MSI), is a genetic phenomenon characterized by the presence of short, repetitive DNA sequences, known as microsatellites, that are unstable and prone to mutations. These mutations occur due to a deficiency in the DNA mismatch repair (MMR) system, which is responsible for detecting and correcting errors in the DNA sequence. MSI is commonly associated with certain types of cancer, particularly colorectal cancer, and is used as a diagnostic marker in clinical settings.

The MMR system consists of several proteins, including MLH1, MSH2, MSH6, and PMS2. Mutations or epigenetic silencing of these proteins can lead to MSI. The most common type of MSI is MSI-H (high-level microsatellite instability), which is characterized by the instability of at least 30% of microsatellites in a tumor. MSI-L (low-level microsatellite instability) refers to the instability of 1-30% of microsatellites.

MSI is a significant biomarker in oncology, as it can predict the response to certain treatments, such as immunotherapy. Tumors with MSI-H are often more sensitive to immune checkpoint inhibitors, which can enhance the body's immune response against cancer cells. Additionally, MSI can provide insights into the molecular mechanisms underlying cancer development and progression.

The diagnosis of MSI typically involves the analysis of microsatellite markers in tumor DNA using techniques such as polymerase chain reaction (PCR) or next-generation sequencing (NGS). The interpretation of MSI results requires careful consideration of the specific microsatellite markers analyzed and the clinical context of the patient.