GUCY2C and colorectal cancer: Many antigens for colorectal cancer have been identified, such as carcinoembryonic antigen (CEA), MUC1, and guanosine cyclooxygenase C (GUCY2C, GCC) [206], but they fail to demonstrate sufficient clinical efficacy because of immune escape phenomena which indicates for the combination with inhibitors of Wnt/β-catenin.