Expression of integrins in human cultured mesothelial cells: the roles in cell-to-extracellular matrix adhesion and inhibition by RGD-containing peptide

Integrins play key roles in cell-to-cell and cell-to-extracellular matrix ( ECM) adhesion. We investigated integrin expression on pleural mesothelial c ells (PMCs) and the inhibitory effect of arginine-glycine-asparate (RGD)-co ntaining peptide on the adhesion of PMCs to fibronectin and collagen. Using flow cytometry and immunostaining. PMCs freshly isolated from pleural effusions and one mesothelial cell line were screened for different integr ins. Intact pleural tissue was evaluated by immunohistochemistry. The adhes ion of Met-5A cells to fibronectin and collagen types I. III and IV was ass ayed with prior treatment of various concentrations of glycine-arginine-gly cine-aspartate-serine (GRGDS). On primary PMCs, alpha2, alpha3, alpha5, beta1, beta3 and alphav beta3 were highly expressed (> 70%); alpha1 expression was intermediate (30-70%); and alpha4 and alpha6 expressions were low (<30%). On Met-5A cells, <alpha>3, alpha5, alpha6 and beta1 were highly expressed (>70%); alpha1 was intermedi ate (30-70%); and alpha2, alpha4, beta3 and alphav beta3 were low (<30%). T he patterns of immunostaining on pleural tissues were similar to the result s of flow cytometry for primary PMCs except for <beta>3. There was no stati stically different expression in various disease states (transudate vs. exu date, benign vs. malignant). The inhibitory effect of GRGDS peptide on Met- 5A cell adhesion to all four matrix proteins was dose-dependent.