Improved Microsatellite Instability Detection and Identification by Nuclease-Assisted Microsatellite Instability Enrichment Using HSP110 T17

Abstract

To the Editor: Microsatellite instability (MSI)1 is characterized by the accumulation of mutations (insertions or deletions of several nucleotides) in microsatellites, caused by DNA mismatch repair system deficiency. Approximately 15% to 20% of colorectal cancers (CRCs) present with MSI, the origin of which can be sporadic or owing to genetic predisposition to Lynch syndrome/hereditary nonpolyposis CRC or constitutional mismatch repair deficiency syndrome. The MSI phenotype is associated with a better survival rate for patients with stage II/III CRC and is also a major predictive biomarker for the efficacy of immune checkpoint blockade therapy in metastatic CRC. The gold standard method for MSI detection includes standard PCR followed by fragment analysis using the Bethesda or the Pentaplex panel, each composed of 5 microsatellite markers. However, this approach can lack analytical sensitivity, thus limiting potential clinical applications. Recent attempts to improve the analytical sensitivity of MSI detection include a method based on mutation enrichment during E- ice -COLD-PCR. This method uses HSP110 T17 (HT17), which, compared with the Pentaplex panel, is an improved microsatellite biomarker for the diagnosis of MSI/MSI-High in CRC and also bears prognostic and predictive information …