MSI-H colorectal tumors display frameshift mutations in the T
-microsatellite of the WTX -gene. (A) Genomic DNA from 632 patients with metastatic CRC (UICCIV) was analyzed for the presence of MSI-H with the help of the two monomorphic microsatellite markers BAT25 and BAT26. Shown are representative results from two CRCs with MSI-H (ID #1, #2) and one CRC with MSS (ID #42). (B) Two tumors of the 41 MSI-H cases of CRCs harbored frameshift mutations in the coding sequence of the T6-repeat of the WTX-gene resulting in the occurrence of a T5-repeat (ID #1 and #2) compared to only wild type T6-repeats in tumors with MSS CRCs (ID #3). Left: shown by FCE, right: shown by direct sequencing.