TROP-2, also named tumor-associated calcium signal transducer 2 (TACSTD2), GA733 tumor associated antigen, and epithelial glycoprotein-1 (EGP-1), is a type I transmembrane protein highly expressed in carcinomas. It was originally identified as an antigen present on human gastrointestinal tumors and is the second of two members of this family. The other family member is GA7332, also called EpCAM, TROP1, 171A, gp40 and KSA. TROP2 can transduce an intracellular calcium signal and may play a role in tumor growth. It also has adhesive functions.