dMMR, which stands for deficient mismatch repair, refers to a condition where the body's system for correcting errors that occur during DNA replication is not functioning properly. This malfunction is a critical factor in the development of certain cancers.
Understanding Mismatch Repair (MMR)
Normally, our cells have a sophisticated system called mismatch repair (MMR) that acts like a spell-checker for our DNA. When DNA is copied, errors called mismatches can occur. The MMR system detects and corrects these mismatches, ensuring the integrity of our genetic code.
What Happens When MMR is Deficient (dMMR)?
When the MMR system is deficient (dMMR), these errors are not corrected efficiently. As a result:
- Microsatellite Instability (MSI): One of the main consequences of dMMR is the development of microsatellite instability (MSI). Microsatellites are repetitive sequences of DNA. With a malfunctioning MMR, the number of these repeats can fluctuate, leading to high levels of MSI, specifically termed MSI-H (MSI-High).
- Cancer Development: The accumulation of these uncorrected errors and MSI-H can significantly increase the risk of cancer. This is because genetic errors can lead to uncontrolled cell growth and tumor formation.
Key Features of dMMR:
| Feature | Description |
|---|---|
| Definition | Deficient mismatch repair, a dysfunction in DNA error correction. |
| Genetic Signature | Leads to high levels of microsatellite instability (MSI-H). |
| Significance | A characteristic of specific cancers and important for targeted treatments. |
| Consequence | Accumulation of DNA errors, increasing cancer risk. |
Clinical Implications of dMMR
- Diagnostic Marker: dMMR and MSI-H serve as important markers for identifying specific cancer types.
- Targeted Therapy: Certain cancer treatments, such as immunotherapies, may be more effective in cancers with dMMR.
- Prognostic Indicator: dMMR status can help predict a patient’s response to treatment and long-term outcomes.
In summary, dMMR is a genetic characteristic linked to impaired DNA repair mechanisms and is marked by MSI-H, significantly influencing the development and treatment of certain cancers.
