Vestibular schwannoma (VS) is a debilitating intracranial tumor and an important cause of genetic human sensorineural hearing loss (SNHL). VSs arise from neoplastic Schwann cells of the vestibular nerves and typically cause progressive SNHL, tinnitus, and dizziness. Though VS-associated SNHL is progressive and post-lingual, making the possibility of pharmacologic intervention to stabilize hearing practical, there are currently no FDA-approved drug therapies for NF2 or VS. Bilateral VSs develop as the hallmark of neurofibromatosis type 2 (NF2), an autosomal dominant disorder characterized by NF2 gene mutation. Limited access to primary human tissue has slowed the generation of an accurate cellular model of human NF2- associated VS; the only available human cell line was recently shown to express a functional isoform of the NF2 protein product, making it an imprecise model by which to simulate the full phenotypic spectrum of NF2. We hypothesize that the generation of expandable, representative, and biologically diverse human cell lines from NF2-associated VSs will enable us to utilize high-throughput drug screening technology to identify and validate a compound that will most effectively slow VS growth or induce VS cell death at clinically reasonable concentrations. To motivate a high-throughput drug screen, we first conducted an in silico drug screen comparing gene expression patterns in 80 human VSs with 16 healthy control nerves. Our algorithm screened genes differentially expressed in VS against all known gene-drug interactions of 1155 FDA-approved drugs, identifying eight drugs with potential for clinical repurposing. Validation experiments on primary human VS and Schwann cells showed that one drug, mifepristone, successfully reduced the morphology, metabolic viability, and proliferation of primary human VS cells without harming Schwann cells (Sagers et al., accepted). However, this drug is most effective at physiologically unreasonable concentrations, and restricting our investigation to FDA-approved drugs limits our ability to identify a maximally potent inhibitor. Therefore, to test our hypothesis, we will (1) generate novel human VS cell lines from NF2-associated tumors. As preliminary data, we have already generated one novel cell line which has been propagated in our laboratory for three months and for which comprehensive characterization experiments are underway. We will (2) conduct a high-throughput small molecule screen using immortalized NF2-associated VS cells in order to identify compounds that halt or slow VS growth; and (3) validate resulting candidate drugs in vitro using primary VS and Schwann cells. Effective drugs related to mifepristone and anti-inflammatory medications that successfully inhibit the growth or promote the death of VS cells at nanomolar concentrations in vitro while leaving healthy Schwann cells unaffected will be prioritized for in vivo validation. Generating diverse and representative cellular models of NF2-associated VS will fill a critical gap in the field, and targeted screening of clinically relevant bioactive compounds will expedite the translation of a successful drug to human clinical trials.
The proposed research aims to discover an effective drug therapy for a tumor called vestibular schwannoma, associated with the disease neurofibromatosis type 2. We will do this by creating new human cellular models of the disease, testing large libraries of existing drugs on those cellular models, and verifying the most promising candidates by testing them on cells grown from patient tumors. There is currently no drug therapy for vestibular schwannoma, so discovering an effective and safe drug could transform patient care.
