Topoisomerase IIα mediates TCF-dependent epithelial-mesenchymal transition in colon cancer.
Zhou Q, Abraham AD, Li L, Babalmorad A, Bagby S, Arcaroli JJ, Hansen RJ, Valeriote FA, Gustafson DL, Schaack J, Messersmith WA, LaBarbera DV. Topoisomerase IIα mediates TCF-dependent epithelial-mesenchymal transition in colon cancer. Oncogene. 2016 Sep 22;35(38):4990-9.
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.
Medical Subject Headings
Antigens, Neoplasm; Cell Line, Tumor; Cell Proliferation; Chromatin Immunoprecipitation; Colonic Neoplasms; DNA Topoisomerases, Type II; DNA-Binding Proteins; Epithelial-Mesenchymal Transition; Gene Expression Regulation, Neoplastic; Humans; Neoplasm Invasiveness; Neoplasm Metastasis; Neoplasm Proteins; Protein Interaction Maps; Transcription Factor 7-Like 2 Protein; beta Catenin