MSLN is a protein that in humans is encoded by MSLN gene. It is a 40 kDa protein that is expressed in mesothelial cells. It is over expressed in several human tumors, including mesothelioma, ovarian cancer, pancreatic adenocarcinoma and cholangiocarcinoma. The interaction between mesothelin and MUC16 (also known as CA125) may facilitate the implantation and peritoneal spread of tumors by cell adhesion. the region of MSLN has 64 amino acids at the N-terminus of cell surface mesothelin.