Abstract 2525: MLN4924 synergistically enhances cisplatin-induced cytotoxicity via JNK and Bcl-xL pathways in human urothelial carcinoma - In vitro and in vivo study

Abstract

Abstract Introduction Cisplatin-based chemotherapy is the main treatment for metastatic bladder urothelial carcinoma; however, the response rate is only approximately 40-65%. Many patients will encounter drug resistance to chemotherapy eventually. Therefore, combination therapies to enhance the efficacy of cisplatin and to overcome drug resistance are imperative for the treatment of urothelial carcinoma. The aim of this study was to investigate the antitumor effect and underlying mechanisms for the combination of cisplatin and MLN4924, a NEDD8-activating enzyme inhibitor, in human bladder urothelial carcinoma. Materials & Methods We used MTT assays and CalcuSyn software to calculate the combination index of cisplatin and MLN4924. The expression levels of DNA damage response regulators, apoptotic-related molecules, MAPK and Bcl-xL were revealed by western blot. c-Jun N-terminal kinase (JNK) inhibitor (SP600125) and overexpression of Bcl-xL were used to investigate the relationship between JNK and Bcl-xL. The in vitro findings were further confirmed in vivo via xenograft mouse model. Results The combination of cisplatin and MLN4924 exerted synergistic cytotoxicity on two high-grade bladder urothelial carcinoma cell lines, NTUB1 and T24 (combination index <1). In addition, MLN4924 potentiated cisplatin-induced apoptosis and activation of caspase-3, 7, phospho-histone H2A.X and PARP. We also observed c-Jun N-terminal kinase (JNK) activation with down-regulation of Bcl-xL during cisplatin and MLN4924 treatment. The inhibition of JNK activation partially restored cell viability as well as the expression of B-cell lymphoma-extra large (Bcl-xL); moreover, the overexpression of Bcl-xL rescued cell viability. In the in vivo study, MLN4924 significantly potentiated cisplatin-induced tumor suppression in urothelial carcinoma xenograft mice. Conclusion In summary, MLN4924 synergistically enhanced the antitumor effect of cisplatin through increasing DNA damage, JNK activation and down-regulating Bcl-xL in urothelial carcinoma cells. These findings provide a new therapeutiuc strategy for bladder cancer. Citation Format: I-Lin Ho, Kuan-Lin Kuo, Chien-Tso Chou, Chen-Hsun Hsu, Yeong-Shiau Pu, Ju-Ton Hsieh, Kuo-How Huang. MLN4924 synergistically enhances cisplatin-induced cytotoxicity via JNK and Bcl-xL pathways in human urothelial carcinoma - In vitro and in vivo study. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2525. doi:10.1158/1538-7445.AM2015-2525