ERBB2 and colorectal cancer: While not unique to cancer, they are often overexpressed ontumor cells, making them a target for immune attack.25 Examples of TAAs include the following: MART-1, found inmelanocytes and melanomas; HER2/neu, overexpressed in some types ofbreast cancer; AFP (α-fetoprotein) in liver tumors; CEA (carcinoembryonicantigen) in colorectal cancer.26−28 However, TAAs can sometimes leadto immune tolerance, where the body fails to recognize them as a threat,or trigger a response against healthy cells.