Mesothelin: a new target for immunotherapy.

Mesothelin is a differentiation antigen present on normal mesothelial cells and overexpressed in several human tumors, including mesothelioma and ovarian and pancreatic adenocarcinoma. The mesothelin gene encodes a precursor protein that is processed to yield the 40-kDa protein, mesothelin, attached to the cell membrane by a glycosylphosphatidyl inositol linkage and a 31-kDa shed fragment named megakaryocyte-potentiating factor. The biological function of mesothelin is not known. Mesothelin is a promising candidate for tumor-specific therapy, given its limited expression in normal tissues and high expression in several cancers. SS1(dsFv)PE38 is a recombinant anti-mesothelin immunotoxin that is undergoing clinical evaluation in patients with mesothelin-expressing tumors. There is evidence that mesothelin is an immunogenic protein and could be exploited as a therapeutic cancer vaccine. A soluble mesothelin variant has been identified and could be a useful tumor marker for malignant mesotheliomas.