Quantitative analysis of integrin expression in effusions using flow cytometric immunophenotyping

We have previously shown that flow cytometric (FCM) immunophenotyping is a useful adjunct to morphology, in the diagnosis of serous effusions. The objective of the present study was to evaluate the possible application of FCM to quantitative analysis of adhesion molecule expression in this clinical setting. Fresh frozen cells from 67 effusions underwent quantitative analysis of αV, α6, β1, and β3 integrin subunit expression, using FCM. Specimens were diagnosed as carcinoma (n = 48), reactive (n = 12), or malignant mesothelioma (MM; n = 7) using morphology and, in selected cases, immunocytochemistry prior to FCM analysis. Antibodies against established epithelial, lymphoid, and mesothelial cell epitopes (Ber‐EP4, anti‐epithelial membrane antigen; (EMA), anti‐CD45, anti‐CD14, and anti‐CD15) completed the panel. Results (percentage of cells expressing the antigen) were analyzed for relationship with the morphologic diagnosis. Frequent expression of the αV, α6, and β1 subunits was seen in all diagnostic groups, with significantly higher expression of the α6 subunit in MM (P = 0.029, Kruskal‐Wallis H test). The β3 integrin subunit was not detected in any of the specimens. Ber‐EP4 and CD15 expression was significantly higher in carcinomas compared with reactive effusions and MM (P < 0.001 and P = 0.001, Kruskal‐Wallis H test), and EMA expression was higher in carcinomas and MM, compared with reactive specimens (P < 0.001, Kruskal‐Wallis H test). In conclusion, FCM is an efficient tool for quantitative analysis of adhesion molecules in effusions. The high α6 integrin subunit expression in MM suggests involvement of this receptor in tumor attachment to laminin. The frequent expression of the αV and β1 subunits support attachment to fibronectin and vitronectin as the major ECM ligands in body cavities. Diagn. Cytopathol. 2005;33:325–331. © 2005 Wiley‐Liss, Inc.