Altered expression of β-catenin/E-cadherin in meningiomas

Aims: Meningiomas are generally slow-growing benign tumours representing approximately 20% of all primary intracranial tumours. The hallmark of tumorigenesis of meningiomas is the loss of chromosome 22, including loss of heterozygosity of the neurofibromatosis type 2 (NF2) gene. The NF2 encoded protein merlin appears to function as a tumour suppressor gene by controlling cadherin-mediated cell-cell adhesion. The E-cadherin cell adhesion system includes beta-catenin that indirectly connects cadherin to actin filaments. The aim of this study was to analyse the expression and the subcellular location of E-cadherin and beta-catenin in human meningiomas, including meningiomas of different histomorphological subtypes and different World Health Organization (WHO) grades. Methods and results: Immunohistochemical analysis revealed lack of E-cadherin expression at the cell membrane in 34% of meningiomas independent of their WHO grade. Loss of membranous beta-catenin occurred in 79% of meningiomas. An intense perinuclear granular immunoreactivity of beta-catenin without nuclear location was detected in the majority of meningiomas. Both immunofluorescence and Western blot analysis of fractionated meningioma cells located beta-catenin mostly on the Golgi apparatus and ER/Golgi intermediate compartment (ERGIC). Cytogenetic analysis of meningiomas showed no correlation between NF2 loss and the loss of the proper location of beta-catenin. Conclusions: The lack of membranous beta-catenin and/or membranous E-cadherin in meningiomas may indicate an altered interaction between meningioma cells independent of loss of NF2 and independent of the tumour grade.