Induction of Mitotic Catastrophe via Inhibition of Aurora Bby Ionizing Radiation With Additive of Mulberry Water Extract in HumanBladder Cancer Cells

摘要

Mulberry fruit water extract (MWE) has been reported to synergisticallyenhance the cytotoxic effect of paclitaxel by promoting mitoticcatastrophe to induce apoptosis in bladder cancer cells in ourprevious work. The aim of this study was to evaluate and tomechanistically explore the effects of MWE on bladder cancer responsesto ionizing radiation (IR) by treating TSGH 8301 bladder carcinomacells with MWE after exposing to IR. The results of MTT assay showed asynergistic cytotoxicity of IR with the co-treatment of MWE (IR/MWE)by inducing G2/M phase arrest as demonstrated by flow cytometryanalysis in TSGH 8301, HT1367 and HT1197 bladder carcinoma cellslines. The IR/MWE-treated cells expressed increased levels of the G2/Mphase arrest-related proteins cdc2/cyclin B1 and displayed giantmultinucleated morphology, a typical characteristic of mitoticcatastrophe. Immunofluorescent confocal microscopy revealed that thecombined strategy inhibited Aurora B phosphorylation throughRas/Raf/MEK/ERK signaling cascade as demonstrated by Western blottinganalysis. IR/MWE also caused an inhibitory effect on Plk1 and thesubsequent downstream regulator RhoA repression and Cep55 induction,which would influence cell cycle progression in the early steps ofcytokinesis. A profound tumor growth suppression and inactivation ofAurora B activity in the tumor tissues by IR/MWE treatment wereconfirmed in the TSGH 8301 xenograft model in vivo. These datademonstrated that MWE could be an effective auxiliary to synergizewith radiation on the anticancer efficacy by promoting mitoticcatastrophe through inhibition of Aurora B, providing a novel andeffective therapeutic option for bladder cancer management.