TGF-b–Induced Upregulation of malat1 Promotes Bladder Cancer Metastasis by Associating with suz12

Purpose: TGF-b promotes tumor invasion and metastasis by inducing an epithelial–mesenchymal transition (EMT). However, the underlyingmechanisms causing this are not entirely clear. Long noncoding RNAs (lncRNA) have been shown to play important regulatory roles in cancer progression. The lncRNA malat1 (metastasis associated lung adenocarcinoma transcript 1) is a critical regulator of the metastasis phenotype of lung cancer cells. ExperimentalDesign:We, therefore, investigatedwhether TGF-b regulatesmalat1 expression topromote tumor metastasis of bladder cancer. The expression levels of malat1 and EMT markers were assayed in specimens of bladder cancer. The role ofmalat1 in regulating bladder cancermetastasis was evaluated in cell and animal models. Results: TGF-b induces malat1 expression and EMT in bladder cancer cells. malat1 overexpression is significantly correlatedwith poor survival in patients with bladder cancer.malat1 and E-cadherin expression is negatively correlated in vitro and in vivo. malat1 knockdown inhibits TGF-b–induced EMT. malat1 is associated with suppressor of zeste 12 (suz12), and this association results in decrease of E-cadherin expression and increase of N-cadherin and fibronectin expression. Furthermore, targeted inhibition of malat1 or suz12 suppresses the migratory and invasive properties induced by TGF-b. Finally, we demonstrated that malat1 or suz12 knockdown inhibits tumor metastasis in animal models. Conclusion: These data suggest thatmalat1 is an importantmediator of TGF-b–inducedEMT, and suggest that malat1 inhibition may represent a promising therapeutic option for suppressing bladder cancer progression. Clin Cancer Res; 20(6); 1531–41. 2014 AACR. Introduction Human bladder cancer is one of the most common cancers worldwide (1, 2). The majority of bladder cancers are urothelial cell carcinomas evolved from the epithelial lining of the bladder wall (3, 4). The urothelial carcinomas are noninvasive tumors that commonly recur but rarely progress. Invasive bladder tumors are more aggressive. Patients with invasive cancer have amuch worse prognosis, with a 50% 5-year survival (5). The advances in suitable therapy for the purpose of increasing survival rate have been limited because the molecular mechanisms causing metastasis are not entirely known. Revealing the underlying mechanism of bladder cancer metastasis is indispensable for developing effective therapy. Long noncoding RNAs (lncRNA) are a class of noncoding RNA longer than 200 nucleotides with no protein-coding capacity (7). Through regulating gene expression by a variety of mechanisms, including transcription, posttranscriptional processing, genomic imprinting, chromatin modification, and the regulation of protein function, lncRNAs have been shown to play important regulatory roles in diverse biologic processes such as development, cell growth, and tumorigenesis (8–10). HOTAIR expression level is higher in tumor tissues and HOTAIR overexpression is correlated with the presence of cancer metastasis (6, 7). Forced expression ofHOTAIR in cancer cells leads to altered histone H3 lysine 27 (H3K27) methylation and abnormal gene expression, and increases cancer invasiveness and metastasis in a manner dependent on polycomb repressive complex 2 (PRC2; ref. 6). Suz12 or EZH2 functions as a H3K27 methyltransferase to selectively repress gene expression when comprising the PRC2 (8). Suz12 is also required for E-cadherin repression by the Snail1 transcription factor (9). In cancer cells, suz12 inhibition prevents the ability of Snail1 to downregulate Ecadherin and partially suppresses E-cadherin (9). The means by which PRC2 targets specific chromatin regions is currently unclear, but lncRNAs have been shown to interact with PRC2 and facilitate its recruitment to the promoters of some target genes (8, 10). Authors' Affiliation: Department of Renal Transplantation and Urology, Shanghai First People's Hospital, Shanghai Jiaotong University, Shanghai, China Note: Supplementary data for this article are available at Clinical Cancer Research Online (http://clincancerres.aacrjournals.org/). Corresponding Author: Yu Fan, Department of Renal Transplantation and Urology, Shanghai First People's Hospital, Shanghai Jiaotong University, 100HainingRoad, Shanghai 200080, China. Phone: 86-21-63240090; Fax: 86-21-63240090; E-mail: [email protected] doi: 10.1158/1078-0432.CCR-13-1455 2014 American Association for Cancer Research. Clinical Cancer Research www.aacrjournals.org 1531 on October 16, 2017. © 2014 American Association for Cancer Research. clincancerres.aacrjournals.org Downloaded from Published OnlineFirst January 21, 2014; DOI: 10.1158/1078-0432.CCR-13-1455