APC and colorectal cancer: Adenomatous polyposis coli (APC) gene is a tumor suppressor gene and encodes a cytoplasmic protein which binds to β-catenin and it is widely accepted that the APC tumor suppressor gene inactivation is the earliest and key event for mutation initiation in more than 80% of early colorectal cancers, and consequently it is named as “Gate Keeper” for adenoma development [2, 7, 14].