MOLECULAR-CLONING OF A CELL-SURFACE GLYCOPROTEIN THAT CAN POTENTIALLYDISCRIMINATE MESOTHELIUM FROM EPITHELIUM - ITS IDENTIFICATION AS VASCULAR CELL-ADHESION MOLECULE-1

It has long been a practical problem for surgical pathologists to dist inguish mesothelium from epithelium in order to make a positive diagno sis of mesothelioma. In this study, we developed a new monoclonal anti body, designated MS-2761 (IgG1, k), against cultured non-neoplastic me sothelial cells. Immunohistochemistry and slot-blot analysis revealed that this monoclonal antibody reacted with 100% (12/12) of benign and malignant mesothelioma tissues and a mesothelioma cell line, but not w ith 99% (77/78) of epithelial tumour tissues and 97% (33/34) of epithe lial tumour cell lines. A gene encoding the cell-surface antigen defin ed by this monoclonal antibody was isolated from a mesothelial cell cD NA library constructed with a mammalian cell expression vector through transfection of Cos-7 cells and immunoselection by panning. DNA seque ncing and a database search revealed that the gene was identical to va scular cell adhesion molecule 1 (VCAM1, also referred to as INCAM110). The prominent VCAM1 transcript in mesothelium was 3.2 kb in size with seven Ig-like domains, in addition to a minor transcript with six Ig- like domains. This monoclonal antibody potentially discriminates mesot helium from epithelium and may become a tool for differential diagnosi s of mesothelioma.