CB-5083 and luteolin synergistically induce apoptosis of bladder cancer cells via multiple mechanisms

Abstract

Abstract Purpose Bladder cancer (BC) is a common urological malignancy that still lacks of effective treatments. In recent years, valosin-containing protein (VCP) was emerging as potential target for the treatment of cancers. CB-5083 was a VCP inhibitor that has been evaluated in phase I clinical trials. However, drug-resistance and severe side effects hamper the application of CB-5083. Amounting evidence suggest that combined treatment is a useful strategy to improve the anticancer efficiency with lower toxicity. The aim of this study is to evaluate the combined effects of CB-5083 and luteolin (Lut), a natural flavonoid, on BC cells. Methods Cellular viabilities were measured by the MTT assays. Cell cycle distribution, cellular death and mitochondrial membrane potential were assayed by the flow cytometry. mRNA levels were assayed by the qRT-PCR. Protein levels were measured by western blots. RNA interference was applied to knockdown genes. Xenografts experiments were conducted to evaluate the toxicity in vivo. Results It was found that co-treatment of CB-5083 and luteolin synergistically reduced the viabilities of BC cells. In addition, co-treatment of CB-5083 and Lut also synergistically induced cell cycle arrest at G1 phase and apoptosis in BC cells. Mechanically, CB-5083/Lut cooperatively reduced the expression of Bcl-xl and Mcl-1 in BC cells. Moreover, CB-5083 and Lut synergistically induced endoplasmic reticulum (ER) stress in BC cells. Genetical or pharmacological inhibition of ER stress markedly reduced the apoptosis induced by CB-5083, Lut or their combination in BC cells. In addition, combined treatment of CB-5083 and Lut also synergistically repressed the growth of BC cells in vivo. Conclusion Our data suggest that combined treatment of CB-5083 and Lut might be applied to treat BC.