Clinical Significance
MSI is a key factor in several cancers including colorectal, endometrial, ovarian and gastric cancers. Colorectal cancer studies have demonstrated two mechanisms for MSI occurrence.
- The first is in hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch Syndrome, where an inherited mutation in a mismatch-repair gene causes a microsatellite repeat replication error to go unfixed. Most cases result in changes in the lengths of dinucleotide repeats of the nucleobases cytosine and adenine (sequence: CACACACACA...). The change in nucleotide repeats is an indicator of a faulty DNA repair system, which can ultimately lead to cancer.
- The second mechanism whereby MSI is a marker for colorectal cancer is an epigenetic change that silences an essential mismatch-repair gene.
In both cases, microsatellite insertions and deletions indicate inappropriate DNA repair, resulting in uncontrolled cell division and tumor growth.
Read more about this topic: Microsatellite Instability
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“Of what significance the light of day, if it is not the reflection of an inward dawn?—to what purpose is the veil of night withdrawn, if the morning reveals nothing to the soul? It is merely garish and glaring.”
—Henry David Thoreau (1817–1862)