CEACAM5 and colorectal cancer: In a clinical phase I/II study, patients with carcinoembryonic antigen (CEA)-positive tumors (in most cases colorectal cancer) were repetitively treated with a pDNA vaccine that encoded for a MHCI-restricted CEA-derived peptide fused to an immunostimulatory domain derived from tetanus toxin fragment C as an adjuvant by intramuscular injection for three months [58].