Expression of β1 and β4 integrins in normal arachnoid membrane and meningiomas

BACKGROUND. The aim of this work was to study the expression of α, β1, and β4 integrin subunits in meningiomas. METHODS. Seventeen atypical or anaplastic meningiomas were retrieved from the files of Hopital de Bellevue, Saint-Etienne, France. They were compared with 17 benign meningiomas consecutively examined in 1997 and 6 schwannomas. The tumors were classified according to standard histologic criteria. Frozen sections were immunostained for α1, α2, α3, α4, α5, α6, β1, and β4 integrin subunits; collagen; laminin and fibronectin; cytokeratin; vimentin; neural cell adhesion molecule (NCAM); and MIB-1. RESULTS. The study included 7 fibrous meningiomas, 6 transitional meningiomas, 19 syncytial meningiomas, and 2 secretory meningiomas. The expression of α1, α3, α5, α6, and β1 was constant. The expression of α1 was higher in fibrous meningiomas than in syncytial meningiomas. Only in transitional, syncytial, and secretory meningiomas was the expression of α2 detected. The expression of α2 and β4 was associated with the expression of cytokeratin in the glandular structures of secretory meningiomas, whereas it was associated with NCAM expression in the whorls of meningothelial meningiomas. The expression of integrin receptors by tumor cells was strongly correlated with that of their respective ligands in the extracellular matrix. In invasive meningiomas, the expression of α3 and α6 by tumor cells was significantly lower. The higher the MIB-1 proliferation index, the lower the expression of α3. The 6 schwannomas expressed only α2, α3, α6, β1, and β4 integrins. CONCLUSIONS. Each histologic subtype of meningioma has a specific spectrum of integrin expression. The study of α3 and α6 may have prognostic value in the assessment of meningiomas. The study of the integrin profile is valuable for the differential diagnosis of fibrous meningiomas and schwannomas.