Tissue and RNA Microarray Analysis of Invasive and Noninvasive Meningiomas

Introduction: The pathogenesis of meningioma bone invasion remains unknown. Osteopontin (OPN), matrix metalloproteinases, and integrins have been implicated in bone invasion in several neoplasms including breast and prostate carcinomas. We investigated immunohistochemical expression of these proteins in bone invasive meningiomas (IMs) and noninvasive meningiomas (NIMs) using the high throughput tissue microarray (TMA) method. Expression of RNA was also profiled in a subset of sphenoid wing IMs and NIMs.

Methods: Fifty-seven patients with IMs and NIMs were included in our study, and clinicopathological data were collected. Tissue microarray was generated, and immunohistochemical analysis for OPN, integrin-beta-1 (ITG-b1), and matrix metalloproteinase-2 (MMP-2) was performed. An RNA microarray was performed on sphenoid wing meningiomas using the DASL platform.

Results: The results of these analyses were: ITG-b1: ITG-b1 expression exhibited a striking concentric perivascular pattern in some meningiomas. Tumor cell immunoreactivity was significantly higher in invasive transbasal meningiomas than in NIMs (P = 0.0356). MMP-2: Noninvasive transbasal meningiomas exhibited higher MMP-2 immunoexpression in vascular endothelial cells compared with invasive meningiomas (P = 0.0079). OPN: Immunoexpression was significantly higher in invasive transbasal meningiomas than in NIMs (P = 0.05). RNA Microarray: 92 genes were found to be upregulated, and 130 genes were downregulated (minimum 1.5-fold change) in invasive sphenoid-wing meningiomas. The highest level of upregulation was seen in MATN4 (26.4-fold), with its receptor ADAMTS4 being upregulated by 3.5-fold. Increased expression of the RNAs for MMP-12, MMP-16, and PDGFR-A was noted in invasive meningiomas. The RNA data were verified using real-time PCR for selected genes. Pathway analysis revealed genes differentially expressed in post-translational modification, cell cycle regulation, gene expression, and cell compromise, as well as cell assembly and organization pathways.

Conclusions: Bone IMs and NIMs show differential protein immunoexpression and RNA expression. ITG-b1 and OPN immunoexpression and RNA expression of MATN4 and ADAMTS4—genes involved in development and homeostasis of cartilage and bone—are higher in bone IMs, highlighting the potential for existence of a pathway promoting bone infiltration in select meningiomas. Characterization of two invasive and two noninvasive meningioma cell lines were performed for future functional studies to examine the role of MATLN4 in meningioma behavior.