Combined Microsatellite Instability and Elevated Microsatellite Alterations at Selected Tetranucleotide Repeats (EMAST) Might Be a More Promising Immune Biomarker in Colorectal Cancer

Abstract

Elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) is a unique molecular subtype of colorectal cancer (CRC). The current study demonstrated that the EMAST-positive and MSI-high (MSI-H) group was associated with female predominance, higher prevalence of proximal colon tumors, early stage tumors, poorly differentiated tumors, mucinous histology, and higher incidence of mutations in <i>PI3KCA</i>, <i>BRAF</i>, <i>TGFBR</i>, <i>PTEN</i>, and <i>AKT1</i> compared with other groups. Most importantly, high mutations in DNA repair genes and MSI-related genes in EMAST-positive and MSI-H tumors suggest that this subtype of CRC might be more suitable for treatment with immune therapy compared with MSI-H tumors alone.