MUC16, well known as CA125 (carbohydrate antigen 125 or cancer antigen 125), is a member of the mucin family glycoprotein ranked as the largest membrane-associated mucin with about 22,000 amino acids, which is initially detected by the murine monoclonal antibody designated OC125 (the 125th Ab produced against the ovarian cancer cell line) and named " cancer antigen 125". It consists of a cytoplasmic tail for the interaction with cytoskeleton, a transmembrane domain and several extracellular domains including a highly O-glycosylated N-terminal domain, a tandem repeat (high in serine, threonine and proline) and multiple SEA (sea urchin sperm protein, enterokinase and agrin) modules, which contain a proteolytic cleavage site for release of extracellular region from the cell surface. Learn more: anti-MUC16 CAR-T in vivo assay.