BAT25, ACVR2, and TGFBR2 mononucleotide STR markers: A triplex panel for microsatellite instability testing in colorectal tumors

Abstract

Background: Microsatellite instability (MSI) in colorectal cancer (CRC) patients is considered as a diagnostic and prognostic marker. MSI is a consequence of mismatch repair deficiency which is evaluated using the different microsatellite markers on the whole genome. In this pilot study, the diagnostic value of a novel triplex panel including three mononucleotide markers has been evaluated in comparison to the standard Promega kit for MSI testing in CRC patients with Amsterdam II criteria. Materials and Methods: DNA extracted from tumors and normal Formalin-Fixed Paraffin-Embedded (FFPE) tissues of index cases from 37 HNPCC (Hereditary non-polyposis colorectal cancer) families were evaluated for MSI state. Primer design for three markers, including BAT25, ACVR2, and TGFBR2, was performed using 19 nucleotides of the M-13 phage. The instability of each marker was assessed through fragment analysis in comparison with Promega kit markers for all patients. The sensitivity and specificity of each marker have been calculated. Results: The comparative evaluation of MSI in both tumors and normal adjacent FFPE tissues demonstrated a separate sensitivity as 100%, 83.3%, and 76.9% for BAT25, ACVR2, and TGFBR2, respectively, and 100% sensitivity in the form of a triplex. Moreover, the specificity for each of these three markers in MSI testing was estimated as 100%, separately and in the form of the triplex in comparison with the Promega pentaplex standard Kit. Conclusions: A high sensitivity and specificity for the novel triplex panel in MSI-testing were estimated among Iranian patients. More studies are recommended to confirm this panel as a diagnostic kit for MSI testing.

Keywords

• dna mismatch repair
• lynch syndrome
• microsatellite instability
• microsatellite markers