Minocycline Attenuates Ototoxicity and Enhances Antitumor Activity of Cisplatin Treatment In Vitro

Objective. Some agents have been shown to prevent cisplatin-induced ototoxicity. The objective is to show that the agent minocycline protects the cochlea against cisplatin damage and enhances the cytotoxicity of anticancer therapies. Study Design. In vitro chemotherapeutic assessments of minocycline. Setting. Research laboratory. Subjects and Methods. Hep-2 cells were cultured with and without 100 mu M cisplatin, and cell growth inhibition was assessed. Autophagy in the samples was visually evaluated by electron microscopy and by beclin-1 expression using Western blotting. In another experiment, cochlear basilar membranes of 3-day-old rats were isolated and cultured. The cultures were treated with the same concentration of cisplatin or cisplatin combined with minocycline. Immunofluorescence staining was used to identify changes in spiral ganglions. Results. Cell growth was inhibited in a dose-dependent manner following minocycline treatment. Furthermore, the combination of cisplatin and minocycline effectively increased tumor cell death (P < .01). Autophagosomes were also evident in cells treated with minocycline. Beclin-l protein expression was increased after minocycline treatment in Hep-2 cells. In an experiment evaluating cochlear spiral ganglion neuron survival, it was found that the number of surviving cochlear neurons significantly increased in the minocycline pretreatment group compared with the group treated with cisplatin alone (P < .01). Conclusion. This study shows that minocycline alone, or in combination with chemotherapeutic drugs, inhibits the growth of tumor cells and attenuates ototoxicity. It is also shown that minocycline activates cell autophagy via the beclin-1 signaling pathway, which may be an additional underlying cause of Hep-2 cell death.