MSLN and mesothelioma: Mesothelin (MSLN), a plasma membrane differentiation antigen, is expressed at significantly high levels in several human cancers, including nearly all mesotheliomas [1] and pancreatic adenocarcinomas [2], [3] as wells as about 70% of ovarian cancers [4], [5] and 50% of lung adenocarcinomas [6], [7].