TROP1, also known as EpCAM (Epithelial Cellular Adhesion Molecule) or CD326, is a 40 kDa type I transmembrane glycoprotein that plays crucial roles in various cellular processes. It consists of an extracellular domain with two epidermal-growth-factor-like (EGF-like) repeats, a transmembrane segment, and a cytoplasmic domain. EpCAM is highly conserved between species, with 82% amino acid sequence identity between humans and mice. It is expressed in various tissues during embryonic development and in adult simple, pseudo-stratified, and transitional epithelia, but not in normal squamous epithelia or mesenchymal tissues. EpCAM is upregulated in proliferating epithelial tissues, during liver regeneration, and in many carcinomas, making it a potential target for cancer therapy. Functionally, EpCAM acts as a homophilic Ca虏鈦?independent adhesion molecule, forming dimers and tetramers that interact with the actin cytoskeleton and regulate cell adhesion, proliferation, and epithelial-to-mesenchymal transition.