Understanding MSI-H: A Key Factor in Cancer Treatment

Microsatellite Instability (MSI) is a genetic abnormality caused by defects in DNA repair genes known as Mismatch Repair (MMR) genes, including MLH1, MSH2, MSH6, and PMS2. These defects lead to the accumulation of DNA errors, causing abnormal cell division and increasing the risk of various cancers.

Types of MSI

1. MSI-High (MSI-H):

   • There is a high degree of abnormality in microsatellites.
   • It is often found in colorectal cancer, endometrial cancer, and stomach cancer.
   • Often associated with genetic diseases such as Lynch Syndrome.
   • responds well to immunotherapy (Immunotherapy)

2. MSI-Low (MSI-L):

   • There were few microsatellite abnormalities.
   • It is less associated with MMR gene abnormalities than MSI-H.

3. Microsatellite Stable (MSS):

   • There were no microsatellite abnormalities.
   • It is often found in common cancers that are not related to MMR gene mutations.

Cancers Associated with MSI-H

1. Colorectal Cancer
   • Frequently found in patients with Lynch Syndrome
   • MSI-H tumors respond well to immunotherapy.
2. Endometrial Cancer
   • It is a cancer that has a high prevalence of MSI abnormalities, especially in women with Lynch Syndrome.
   • MSI-H guides treatment planning and prognosis.
3. Gastric Cancer
   • MSI-H cases show promising responses to immunotherapy.
4. Ovarian Cancer
   • Especially in Endometrioid Type, often linked to Lynch Syndrome.
5. Urothelial Cancer
   • MSI-H tumors in the bladder or kidneys may respond to immunotherapy.
6. Pancreatic Cancer
   • Although rare, MSI-H can influence treatment choices.
7. Cholangiocarcinoma
   • Studies suggest MSI-H may contribute to cancer progression.
8. Glioblastoma Multiforme (GBM)
   • MSI-H may impact long-term treatment strategies.