Abstract It has been proposed that by silencing tumor suppressor genes, DNA methylation plays an important function in cancer initiation and progression. DNA hypomethylating agents are being developed as anti-cancer agents. However, this approach causes unrestricted hypomethylation, which could potentially activate tumor-promoting mechanisms. Therefore a strategy capable of inducing hypomethylation of selected genes is needed. Towards this goal, we designed a strategy to induce demethylation of a coordinated gene program by using Ten-eleven translocation (TET1) dioxygenase, which converts 5 -methylcytosine to 5-hydroxymethylcytosine. We constructed a fusion gene TET1-DBD containing the catalytic domain of TET1 and the DNA binding domain of Snail, the transcription factor that regulates epithelial-to-mesenchymal transition (EMT). We hypothesized that this fusion gene will bind to promoters targeted by Snail, induce hypomethylation, reactivate gene expression, and block EMT. To test this hypothesis, we used TET1-DBD and measured induction of EMT in an ovarian (SKOV3) and breast cancer (MCF10A) model driven by TGF-β. Genome-wide DNA methylation was assessed by Reduced Representation Bisulfite Sequencing (RRBS) to measure the downstream targets of TET1-DBD. TET1-DBD increased mRNA and protein expression levels of E-cadherin in transfected cells and prevented TGF-β induced expression of fibronectin and vimentin in MCF10A and SKOV3 cells. RRBS analysis demonstrated hypomethylation of genes targeted by Snail-DBD. Our results suggest that TET1-DBD selectively binds to and hypomethylates promoters of genes targeted by Snail, resulting in inhibition of the EMT program. We propose a novel approach to induce selective promoter hypomethylation and to block key oncogenic processes by using TET1 fused to a transcription factor “carrier”. Citation Format: HAO HUANG, Qing Yu, Maooj Kandpal, Ramana V. Davuluri, Daniela Matei. Pathway-directed DNA demethylation as an epithelial to mesenchymal targeting strategy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1396.
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