Illustration of mesothelin (dark blue and orange) bound to a monoclonal antibody (light blue). Mesothelin (MSLN) is a membrane glycoprotein found on mesothelial cells, which line some body cavities including the peural (lungs) cavity and the pericardial (heart) sac. Mesothelin is over expressed in several human tumours, including mesothelioma and ovarian cancer. Monoclonal antibodies are proteins made in a laboratory that bind to specific antigens such as proteins on cancer cells. The binding of antibodies to mesothelin kills the cancer cells through antibody-dependent cell-mediated cytotoxicity (ADCC). ADCC is part of the body's humoral immune response and signals effector cells to break down targeted cancer cells. Mesothelin is being researched as a target for cancer immunotherapy.