Instabilotyping: comprehensive identification of frameshift mutations caused by coding region microsatellite...

Area of Science:

• Genomics
• Cancer Biology
• Molecular Oncology

Background:

• Microsatellite instability (MSI) is a hallmark of certain cancers, leading to frameshift mutations.
• Transforming growth factor beta receptor type 2 (TGFBR2) mutations exemplify MSI-driven tumorigenesis.
• Identifying additional MSI targets is crucial for understanding cancer development.

Purpose of the Study:

• To conduct a large-scale genomic screen for novel coding region microsatellite mutations in MSI-high colorectal tumors.
• To identify genes and pathways previously unlinked to colorectal tumorigenesis via MSI.

Main Methods:

• Bioinformatic identification of 1115 coding homopolymeric microsatellite loci (≥6 nucleotides).
• Mutational screening of 152 loci in 46 high-frequency MSI colorectal tumors.
• Analysis of mutation frequency across identified loci.

Main Results:

• Nine novel loci mutated in ≥20% of tumors, including activin type II receptor gene (58.1%), SEC63 (48.8%), and AIM 2 (47.6%).
• Additional frequently mutated genes include NADH-ubiquinone oxidoreductase subunit, mouse cordon-bleu homologue, and EBP1/PA2G4.
• 66 of 152 screened loci showed no mutations in the analyzed tumor set.

Conclusions:

• Genome-wide screening effectively identifies novel coding region MSI targets in colorectal cancer.
• Discovered mutations implicate new genes and pathways in MSI-related tumorigenesis.
• These findings warrant further functional studies to elucidate their role in cancer development.