CA-125

null CA-125, the antigen defined by the OC125 antibody, is a high-molecular-mass epitope carried on the mucin MUC16, a huge transmembrane glycoprotein with numerous tandem repeats and sea urchin sperm protein domains. It is normally expressed by mesothelial cells of the pleura, pericardium, and peritoneum and by epithelia of the female reproductive tract, and its soluble ectodomain circulates in serum. Serum CA-125 measurement is the standard biomarker for monitoring epithelial ovarian cancer response and recurrence. CA-125/MUC16 also binds mesothelin, and its tumor expression continues to motivate antibody and CAR-T targeting strategies.