Lack of neurofibromatosis type 2 gene promoter methylation in sporadic vestibular schwannomas.

BACKGROUND: Vestibular schwannomas (VS) are benign tumors of the nervous system that are usually sporadic but also occur in the inherited disorder neurofibromatosis type 2 (NF2). In VS, losses of chromosomal material and mutations of the NF2 gene have been established to be causative. For a subset of VS without detectable gene alterations, promoter inactivation by hypermethylation has been suggested. However, published data are very limited and contradictory.
METHODS: We analyzed NF2 gene promoter methylation in 35 sporadic VS by methylation-specific PCR.
RESULTS: Twenty-three of the tumors were informative, showing no promoter methylation. In the remaining 12 tumors, promoter methylation could neither be verified nor excluded.
CONCLUSIONS: Our study suggests that NF2 gene inactivation by promoter hypermethylation is a rare or very uncommon mechanism of NF2 gene inactivation in sporadic VS. Other mechanisms destabilizing the NF2 gene product, yet to be identified, might play a role in the genesis of VS apart from the loss or mutation of the NF2 gene.