Vestibular schwannoma (VS) is a benign tumor with associated morbidities and reduced quality of life. Except for mutations in NF2, the genetic landscape of VS remains to be elucidated. Little is known about the effect of Gamma Knife radiosurgery (GKRS) on the VS genome. The aim of this study was to characterize mutations occurring in this tumor to identify new genes and signaling pathways important for the development of VS. In addition, the authors sought to evaluate whether GKRS resulted in an increase in the number of mutations.
Forty-six sporadic VSs, including 8 GKRS-treated tumors and corresponding blood samples, were subjected to whole-exome sequencing and tumor-specific DNA variants were called. Pathway analysis was performed using the Ingenuity Pathway Analysis software. In addition, multiplex ligation-dependent probe amplification was performed to characterize copy number variations in the NF2 gene, and microsatellite instability testing was done to investigate for DNA replication error.
With the exception of a single sample with an aggressive phenotype that harbored a large number of mutations, most samples showed a relatively low number of mutations. A median of 14 tumor-specific mutations in each sample were identified. The GKRS-treated tumors harbored no more mutations than the rest of the group. A clustering of mutations in the cancer-related axonal guidance pathway was identified (25 patients), as well as mutations in the CDC27 (5 patients) and USP8 (3 patients) genes. Thirty-five tumors harbored mutations in NF2 and 16 tumors had 2 mutational hits. The samples without detectable NF2 mutations harbored mutations in genes that could be linked to NF2 or to NF2-related functions. None of the tumors showed microsatellite instability.
The genetic landscape of VS seems to be quite heterogeneous; however, most samples had mutations in NF2 or in genes that could be linked to NF2. The results of this study do not link GKRS to an increased number of mutations.