αvβ3 and αvβ5 integrin expression in meningiomas

OBJECTIVE: Integrins are emerging as alternative receptors capable of mediating several biological functions, such as cell-matrix and cell-cell adhesion, cell migration, signal transduction, and angiogenesis. Two alphav integrins, i.e., alphav beta3 and alphav beta5, play critical roles in mediating these activities, particularly in tumors. No data are available on the expression of these integrins in meningiomas. METHODS: Using Western blot and immunohistochemical analyses with LM609 and PG32, two monoclonal antibodies capable of recognizing the functional integrin heterodimer, we evaluated the expression of alphav beta3 and alphav beta5 integrins in a series of 34 meningiomas of different histological subtypes and grades. We studied their expression in tumor cells and vasculature, as well as the expression of their related angiogenic factors (fibroblast growth factor 2 and vascular endothelial growth factor) and the alphav beta3 ligand vitronectin. RESULTS: alphav beta3 and alphav beta5 integrins were expressed by neoplastic vasculature and cells. alphav beta3 and alphav beta5 expression was associated and correlated with that of their respective growth factors (fibroblast growth factor 2 and vascular endothelial growth factor) and microvessel counts and densities. alphav beta3 was more strongly expressed than alphav beta5 in two cases of histologically benign meningiomas with aggressive clinical behavior. alphav beta3 expression was associated with that of its related ligand vitronectin and was also evident in small vessels of brain tissue closely surrounding meningiomas. CONCLUSION: Our data demonstrate the expression of alphav beta3 and alphav beta5 integrins in meningioma cells and vasculature. Our findings suggest a role for both of these integrins, and particularly alphav beta3, in meningioma angiogenesis.