We also pursued studies of SOX2 protein expression in colon tumors arising in an independent mouse CRC model based on mutations in 3 CRC-associated genes — heterozygous mutations in the Apc gene and the Kras oncogene together with biallelic defects in the Trp53 tumor suppressor genes (previously described as AKP270/fl mice and abbreviated here as AKP mice) (27). The gene discussed is KRAS; the disease is colorectal carcinoma.