Tumors from CDX2P9.5-G19Cre;Apcflox/flox mice showed a hypermutable phenotype (arrowhead and black bar) for two (D7Mit91 and GA29) of four markers investigated, suggesting that tumor development occurs via MSI. The 600 LIZ size standard (Eurofins GeneScan, Frieburg, Germany) was used as a marker for sizing DNA fragments.