PLEURAL MESOTHELIOMA MIMICS THE INTEGRIN PROFILE OF ACTIVATED, SESSILE RATHER THAN DETACHED MESOTHELIAL CELLS

Mesothelial cells (MC) form a polarized monolayer lining serosal cavit ies. During serositis, the MC lining undergoes hyperplasia, and MC are shed into effusions. During these processes, contact with basement me mbrane and, ultimately, neighboring cells is at least temporarily lost , suggesting regulated alterations in cell/matrix and cell/cell adhesi on. Such interactions are primarily mediated by integrins. Malignant m esothelioma has a growth pattern characterized by lateral, limited inv asive but contiguous spread. During serositis, activated MC, both sess ile and detached, expressed an extended spectrum of beta(1), beta(3) a nd beta(4) integrins compared with resting MC, as shown by immunohisto logy. Malignant mesothelioma had an integrin repertoire and a subcellu lar distribution resembling that of activated sessile rather than floa ting MC. In vitro, MC exposed a more comprehensive pattern of integrin s than that of the newly established mesothelioma cell lines ME-HD-1 a nd ME-HD-2, as shown by flow cytometry. MC consistently adhered better than mesothelioma cells to laminin, tenascin, fibronectin and collage n type IV. Adhesion of MC and mesothelioma cells to these matrix prote ins was, at least in part, mediated via beta(1) integrins. The differe nt integrin profiles and adhesion properties of cultured MC and mesoth elioma cells may reflect a limited functional differentiation of the l atter. (C) 1997 Wiley-Liss, Inc.