Zhou Q, Abraham A D, Li L, Babalmorad A, Bagby S, Arcaroli J J, Hansen R J, Valeriote F A, Gustafson D L, Schaack J, Messersmith W A, LaBarbera D V
Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
Oncogene. 2016 Sep 22;35(38):4990-9. doi: 10.1038/onc.2016.29. Epub 2016 Mar 7.
Aberrant T-cell factor (TCF) transcription is implicated in the majority of colorectal cancers (CRCs). TCF transcription induces epithelial-mesenchymal transition (EMT), promoting a tumor-initiating cell (TIC) phenotype characterized by increased proliferation, multidrug resistance (MDR), invasion and metastasis. The data presented herein characterize topoisomerase IIα (TopoIIα) as a required component of TCF transcription promoting EMT. Using chromatin immunoprecipitation (ChIP) and protein co-immunoprecipitation (co-IP) studies, we show that TopoIIα forms protein-protein interactions with β-catentin and TCF4 and interacts with Wnt response elements (WREs) and promoters of direct target genes of TCF transcription, including: MYC, vimentin, AXIN2 and LEF1. Moreover, both TopoIIα and TCF4 ChIP with the N-cadherin promoter, which is a new discovery indicating that TCF transcription may directly regulate N-cadherin expression. TopoIIα N-terminal ATP-competitive inhibitors, exemplified by the marine alkaloid neoamphimedine (neo), block TCF activity in vitro and in vivo. Neo effectively inhibits TopoIIα and TCF4 from binding WREs/promoter sites, whereas protein-protein interactions remain intact. Neo inhibition of TopoIIα-dependent TCF transcription also correlates with significant antitumor effects in vitro and in vivo, including the reversion of EMT, the loss of TIC-mediated clonogenic colony formation, and the loss of cell motility and invasion. Interestingly, non-ATP-competitive inhibitors of TopoIIα, etoposide and merbarone, were ineffective at preventing TopoIIα-dependent TCF transcription. Thus, we propose that TopoIIα participation in TCF transcription may convey a mechanism of MDR to conventional TopoIIα inhibitors. However, our results indicate that TopoIIα N-terminal ATP-binding sites remain conserved and available for drug targeting. This article defines a new strategy for targeted inhibition of TCF transcription that may lead to effective therapies for the treatment of CRC and potentially other Wnt-dependent cancers.
异常的T细胞因子（TCF）转录与大多数结直肠癌（CRC）有关。TCF转录诱导上皮-间质转化（EMT），促进具有增殖增加、多药耐药（MDR）、侵袭和转移等特征的肿瘤起始细胞（TIC）表型。本文提供的数据表明拓扑异构酶IIα（TopoIIα）是促进EMT的TCF转录的必需成分。通过染色质免疫沉淀（ChIP）和蛋白质免疫共沉淀（co-IP）研究，我们发现TopoIIα与β-连环蛋白和TCF4形成蛋白质-蛋白质相互作用，并与Wnt反应元件（WRE）以及TCF转录直接靶基因的启动子相互作用，这些基因包括：MYC、波形蛋白、AXIN2和LEF1。此外，TopoIIα和TCF4都能与N-钙黏蛋白启动子进行ChIP，这是一个新发现，表明TCF转录可能直接调节N-钙黏蛋白的表达。以海洋生物碱新两性霉素（neo）为例的TopoIIα N端ATP竞争性抑制剂，在体外和体内均可阻断TCF活性。Neo能有效抑制TopoIIα和TCF4与WRE/启动子位点的结合，而蛋白质-蛋白质相互作用保持完整。Neo对TopoIIα依赖性TCF转录的抑制也与体外和体内显著的抗肿瘤作用相关，包括EMT的逆转、TIC介导的克隆集落形成的丧失以及细胞运动性和侵袭能力的丧失。有趣的是，TopoIIα的非ATP竞争性抑制剂依托泊苷和美巴龙在阻止TopoIIα依赖性TCF转录方面无效。因此，我们提出TopoIIα参与TCF转录可能将MDR机制传递给传统的TopoIIα抑制剂。然而，我们的结果表明TopoIIα N端ATP结合位点保持保守且可用于药物靶向。本文定义了一种靶向抑制TCF转录的新策略，这可能为CRC以及潜在的其他Wnt依赖性癌症的治疗带来有效的疗法。
