PLEURAL MESOTHELIOMAS HAVE AN INTEGRIN PROFILE DISTINCT FROM VISCERALCARCINOMAS

Cryosections of epithelial, sarcomatoid, and biphasic malignant mesoth eliomas (EMM, n = 11; SMM, n = 5; BMM, n = 6) of the pleura were immun ostained with monoclonal antibodies to integrin subunits alpha(1-5 and v), and beta(1-4). Localization patterns were compared with those kno wn to occur in pulmonary and other adenocarcinomas (PADC, ADC). EMM an d the epithelial component of BMM (ecBMM) expressed alpha(1,3,5,6 and v) and beta(1 and 4). SMM and the sarcomatoid elements of BMM (scBMM) reacted variably for alpha(1,3,5,6 and v), and beta 1. Reactions for a lpha(3), found in all tumors, were strongest in EMM, ecBMM, and PADC. Our findings indicate that EMM and ecBMM parallel PADC and most ADC in their expression of alpha(6) beta(4), underscoring that this laminin integrin receptor is intimately associated with these neoplastic epith elial phenotypes. Also, our observations on alpha(3) beta(1) suggest t hat this cell-cell adhesion-mediating integrin is related to the epith elial phenotype. Notably, all malignant mesotheliomas (MM), including those with distinct glandular structures, expressed the alpha(5) beta( 1) fibronectin receptor, thus paralleling most sarcomas and differing from PADC and most other ADC, We conclude that irrespective of archite ctural and cytologic variants, transformed mesothelial cells possess a n integrin repertory that differs significantly from that of most ADC, including those of the lung. These findings set mesothelium apart fro m epithelia and may prove helpful as adjunct tools far the differentia l diagnosis between EMM and AD. Copyright (C) 1997 by W.B. Saunders Co mpany.