APC and colorectal cancer: Genetically modified pigs targeting cancer-specific genes have been established as porcine cancer models, which are expected to replicate human cancers (e.g., GLI2 gene for basal cell carcinoma [10], adenomatous polyposis coli (APC) gene for colorectal cancer [11, 12], and breast cancer associated gene 1 (BRCA1) for breast cancer [13, 14]).