MMP-9 expression in meningiomas: a prognostic marker for recurrence risk?

Despite total macroscopic resection of meningiomas relapses do occur in these tumours, possibly because of microscopic clusters of neoplastic cells left in the dura mater or in the arachnoid membrane. The invasiveness of the neoplastic cells of human meningiomas has been related to expression of matrix-metalloproteinase-9 (MMP-9), a peptidase actively implicated in the degradation of the extracellular matrix; nonetheless, the prognostic value of MMP-9 in the risk of recurrence of meningiomas has not been sufficiently investigated. Herein, we analysed MMP-9 expression in a series of meningiomas of different histotype and histological grade and assessed its correlation with various clinico-pathological indicators and with the clinical outcome of these tumours. We also tested the eventual pro-angiogenic role of MMP-9 expression in meningiomas through its correlation with vascular endothelial growth factor (VEGF) and microvessel density (MVD) revealed in the same cases. MMP-9 expression was observed in 64% of cases; high expression of this protein was significantly associated with high histological grade and proliferation index, but not with high MVD, of the tumours. A trend towards correlation between MMP-9 and VEGF expression was found, although statistical significance was not reached. In addition, high MMP-9 expression was a negative independent prognostic factor associated with higher recurrence risk in totally resected meningiomas. In conclusion, we demonstrated for the first time the potential prognostic value of MMP-9 expression in meningiomas. Inhibition of MMP-9 may be a new therapeutic strategy to prevent recurrences of meningiomas, particularly the high-grade type.