The inhibitory effect of honokiol, a natural plant product, on vestibular schwannoma cells

Objectives/Hypothesis: As the molecular biology of vestibular schwannoma (VS) is better understood, new means of targeting the pathways involved for intervention in schwannoma cells are being developed. Honokiol, a bioactive constituent of Magnolia officinalis, has attracted attention due to its diverse biological effects. This study was conducted to determine the inhibitory effect of honokiol on schwannoma cell proliferation. Methods: HEI 193 cells were used to investigate the growth-inhibitory effects of honokiol. Cell proliferation was assessed by MTT assays. Apoptosis was measured by flow cytometry analysis and immunofluorescence staining including Hoechst 33342 and TUNEL. Western blot analysis was used to assess the potential inhibition of extracellular signal-regulated kinase (ERK) and AKT signaling by honokiol. Results: Honokiol exhibited significant antiproliferative activity in a dose-dependent manner on HEI 193 cells. Significant apoptosis was detected on schwannoma cells with 7 mg/mL(IC ₅₀) honokiol. Western blot analysis showed significant inhibition of ERK phosphorylation. Conclusions: Honokiol, a low molecular weight natural product, inhibits cell proliferation and promotes apoptosis in schwannoma cells by targeting the ERK pathway. Our data suggest that honokiol can be evaluated as a chemotherapeutic agent for VS.