pMMR stands for proficient mismatch repair. It describes the normal state of a cell's DNA repair system. This system, called the mismatch repair (MMR) pathway, is responsible for identifying and correcting errors that occur during DNA replication. A pMMR status indicates that this crucial repair mechanism is functioning correctly. This contrasts with dMMR (deficient mismatch repair), where the MMR pathway is faulty, leading to an accumulation of DNA errors.
Understanding Mismatch Repair (MMR)
The mismatch repair pathway is vital for maintaining the integrity of our DNA. During DNA replication, mistakes can happen—incorrect base pairing, insertions, or deletions. MMR proteins detect these errors and initiate a repair process, ensuring accurate replication.
- pMMR: The MMR pathway is fully functional; errors are efficiently corrected.
- dMMR: The MMR pathway is defective; errors accumulate, potentially leading to genomic instability and increased cancer risk.
pMMR in Cancer
The MMR status of a tumor is an important factor in cancer diagnosis and treatment. In colorectal cancer, for example, pMMR/MSS (microsatellite stable) tumors are typically associated with a different prognosis and treatment response compared to dMMR/MSI-H (microsatellite instability-high) tumors. Studies have shown that immune checkpoint inhibitors are generally less effective in pMMR colorectal cancers. [^1][^2][^3] However, there are exceptions, with some cases showing positive responses to immunotherapy. [^4]
pMMR vs. Other Acronyms
It's crucial to note that "pMMR" can be confused with other acronyms, particularly in medical contexts. For example, "PMMR" can also refer to the Personnel Movement for Medical Reasons in the military. [^5] Therefore, understanding the context is essential for accurate interpretation.
[^1]: Immune Checkpoint Inhibitors in pMMR/MSS Colorectal Cancer. PubMed.
[^2]: Microsatellite instability in mismatch repair proficient colorectal cancer. The Lancet.
[^3]: Tumor Budding Versus Mismatch Repair Status in Colorectal Cancer. IIAR Journals.
[^4]: pMMR CRC patients treating with immune checkpoint inhibitors. Dovepress.
[^5]: Operational Forces Medical Liason (OFML) & Medical Evacuation (MEDEVAC). Tricare.
