Microsatellite instability in colorectal cancer

Area of Science:

• Genomics
• Molecular Biology
• Cancer Research

Background:

• Microsatellites are repetitive DNA sequences prone to replication errors.
• The Mismatch Repair (MMR) system corrects these errors, involving proteins like MLH1 and MSH2.
• Deficient MMR (dMMR) leads to microsatellite instability (MSI), a mutator phenotype.

Purpose of the Study:

• To highlight the role of microsatellite instability (MSI) in colorectal cancer (CRC).
• To explain the link between deficient mismatch repair (dMMR) and MSI.
• To underscore the clinical significance of identifying MSI in CRC patients.

Main Methods:

• Review of molecular mechanisms underlying microsatellite stability and instability.
• Analysis of the role of MMR proteins in DNA repair.
• Examination of MSI as a hallmark of hereditary and sporadic colorectal cancers.

Main Results:

• MSI arises from errors in DNA replication and repair, particularly affecting microsatellite sequences.
• dMMR is a primary cause of MSI, observed in Lynch syndrome and sporadic CRC (often via MLH1 inactivation).
• MSI is prevalent in 15% of sporadic CRC cases.

Conclusions:

• MSI is a significant pathway in colorectal cancer pathogenesis.
• Identifying MSI CRC is crucial for diagnosing Lynch syndrome (LS).
• MSI serves as a prognostic and predictive biomarker for CRC patient outcomes and treatment efficacy, including immunotherapy.