Glycoprotein A33 (GPA33) is a transmembrane protein that belongs to the Ig superfamily. It contains V-type Ig-like domains at the N-terminus. It is associated with proteins that play a role in inhibiting T cell activation, such as CD276 (B7-H3) and VSIG4, as well as various cell adhesion molecules. GPA33 is expressed in over 95% of human colon cancers, making it a suitable target for colon cancer tumors.