CD82 (KAI1) belongs to the tetraspanin family, which is characterized by four transmembrane domains, one short extracellular domain (ECL1), and one long extracellular domain (ECL2). CD82 does not have enzymatic activity and appears to function by regulating the trafficking of other proteins and organization of the cell membrane. CD82 was originally described as a costimulator for T cells that directly associates with CD4 and CD8, and was subsequently identified during a screen as a metastasis suppressor in prostate cancer. CD82 has since been found to act as a metastasis suppressor in a variety of cancers, and its downregulation is associated with poor prognosis in research studies. CD82 suppresses metastasis through multiple mechanisms including inhibition of cell motility and invasion by modulating c-Met and the urokinase plasminogen activator surface receptor (uPAR), as well as promotion of homotypic cell-cell adhesion by stabilizing interactions between E-cadherin and β-catenin.
