Cell-bound CEA has served as a target for tumor imaging and anti-cancer therapies. Clinical studies have demonstrated that radiolabeled anti-CEA antibodies and antibody fragments, such as the Food and Drug Administration-approved, Tc-99m-labeled, anti-CEA Fab arcitumomab (CEA-ScanH), can be successfully used as imaging reagents to specifically localize CEA-expressing solid cancers [10, 11, 12] . Anti-CEA radio-immunoconjugate anti-bodies have also been shown to be potentially efficacious for the treatment of patients with metastatic colorectal cancer [13] . In addition, CEA-specific antibody-directed enzyme prodrug therapy and CEA-based vaccine approaches have been developed to treat cancers [14, 15] .