Abstract 3517: Honokiol inhibits bladder tumor growth by suppressing EZH2/miR-143 axis

EZH2, a histone H3K27 methyltransferase, plays an essential role in regulation of cell proliferation, survival, invasiveness and cancer stem cell (CSC) maintenance. The upregulation of the histone methyltransferase EZH2 is frequently detected in various cancer types, including urinary bladder cancer (UBC). However, the mechanisms underlying its role in cancer cell are not yet fully understood. Honokiol, a biologically active biphenolic compound isolated from the Magnolia spp, has been linked with anticancer activities; however, its mechanisms is poorly understood. In this study, we investigated the in vitro and in vivo effects of honokiol on UBC cells and whether honokiol can modulate EZH2 mediated network. By employing MTT, colony formation, wound healing, transwell invasion, Western blot, and Aldofluor stem cell detection assays, honokiol was shown to inhibit human UBC cell proliferation, survival, CSC maintenance, migration and invasion. Immunoblotting assay showed that the reduction of EZH2 expression level by honokiol was correlated with the decreases of MMP9, CD44, Sox2, Notch1. Forced expression of EZH2 reversed honokiol induced cell growth arrest and low clonogenicity, indicating that EZH2 is a major downstream target for honokiol in UBC cells. Since EZH2 is essential for gene expression repression, we screened 24 cancer related miRNAs and found that tumor suppressor miR-143 was the most induced miRNA by honokiol treatment. Further quantitative RT-PCR, chromatin immunoprecipitation (ChIP) and functional analysis revealed that EZH2 directly inhibited the expression of miR-143, whereas the inhibition of miR-143 partially rescued the EZH2 knockdown-induced cell growth arrest and reduced clonogenicity. Moreover, in vivo investigation using xenograft analysis in athymic nude mice indicated that honokiol treatment inhibited tumor progression, which was associated with reduced EZH2, CD44, Sox2, Notch1 and MMP9, and increased expression of miR-143. Altogether, our data indicated that honokiol inhibited human UBC tumor growth and aggressiveness through suppression of EZH2 function and induction of its target, miR-143, and that honokiol is promising candidate for chemoprevention and/or therapeutic treatment for bladder cancer. Citation Format: Jun Yan, Qing Zhang, Wei Zhao, Changxiao Ye, Cunjie Chang, Xiaojing Huang, Junlong Zhuang, Jiannan Song, Yangyan Cui, Isaac Eliaz, Bing Shen, Ruimin Huang, Hao Ying, Hongqian Guo. Honokiol inhibits bladder tumor growth by suppressing EZH2/miR-143 axis. [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 3517. doi:10.1158/1538-7445.AM2015-3517