BRAF inhibition protects against hearing loss in mice

Abstract

Hearing loss caused by noise, aging, antibiotics, and chemotherapy affects 10% of the world population, yet there are no Food and Drug Administration (FDA)-approved drugs to prevent it. Here, we screened 162 small-molecule kinase-specific inhibitors for reduction of cisplatin toxicity in an inner ear cell line and identified dabrafenib (TAFINLAR), a BRAF kinase inhibitor FDA-approved for cancer treatment. Dabrafenib and six additional kinase inhibitors in the BRAF/MEK/ERK cellular pathway mitigated cisplatin-induced hair cell death in the cell line and mouse cochlear explants. In adult mice, oral delivery of dabrafenib repressed ERK phosphorylation in cochlear cells, and protected from cisplatin- and noise-induced hearing loss. Full protection was achieved in mice with co-treatment with oral AZD5438, a CDK2 kinase inhibitor. Our study explores a previously unidentified cellular pathway and molecular target BRAF kinase for otoprotection and may advance dabrafenib into clinics to benefit patients with cisplatin- and noise-induced ototoxicity.

In silico transcriptomics identifies FDA-approved drugs and biological pathways for protection against cisplatin-induced hearing loss

“…The extensive overlap between the molecular signatures associated with cisplatin resistance in cancer cells and cisplatin ototoxicity in HEI-OC1 cells ( Figure 2-figure supplement 2 ) provides validation for our screening approach. Furthermore, many pathways we identified have been previously implicated in otoprotection (i.e., B-Raf, CDK2, STAT3 and others) (5, 43). Iterative ranking of drug candidates based on overlap of target genes in enriched molecular pathways of cisplatin resistance allowed for unbiased selection of compounds for further testing.…”

“…Among the 30 drug candidates we identified and validated in our in silico screens, 15 are FDA-approved for indications other than otoprotection. Recently, focused preclinical studies testing of specific FDA-approved drugs for hearing protection (e.g., statins) have yielded satisfactory results (5, 43–45), thus making these 15 new FDA-approved drugs attractive for repurposing as otoprotectants.…”

“…The apoptosis assay was performed as previously described (43). Briefly, HEI-OC1 cells were pretreated with each of the 30 drug candidates at concentrations ranging from 2 nM to 40 μM one hour before co-incubation with cisplatin, 50µM for an additional 19 hours.…”

“…FVB/NJ mice (6 to 7-weeks old) were used for the cisplatin and noise experiments and hearing function (ABRs and DPOAEs) tested as described before (5, 43). Briefly, ABR tests were performed 2-3 days before cisplatin exposure, and 5 days post-cisplatin exposure.…”

“…After the different treatments the inner ear was microdissected and stained for CtBP2 (ribbon synapses marker) or myosin-VI (HC marker) as previously described (5, 43, 51). The organ of Corti was imaged using a confocal microscope (Zeiss LSM 700) with an oil immersion objective (40x, numerical aperture 1.3) and a digital zoom of 1X.…”