EHMT2 epigenetically suppresses Wnt signaling and is a potential target in embryonal rhabdomyosarcoma
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Agency for Science, Technology and Research (A*STAR), Singapore
- KK Women and Childrens Hospital, Singapore
Abstract
Wnt signaling is down-regulated in embryonal rhabdomyosarcoma (ERMS) and contributes to the block of differentiation. Epigenetic mechanisms leading to its suppression are unknown and could pave the way towards novel therapeutic modalities. We demonstrate that EHMT2 suppresses canonical Wnt signaling by activating expression of the Wnt antagonist DKK1. Inhibition of EHMT2 expression or activity in human ERMS cell lines reduced DKK1 expression and elevated canonical Wnt signaling resulting in myogenic differentiation in vitro and in mouse xenograft models in vivo. Mechanistically, EHMT2 impacted Sp1 and p300 enrichment at the DKK1 promoter. The reduced tumor growth upon EHMT2 deficiency was reversed by recombinant DKK1 or LGK974, which also inhibits Wnt signaling. Consistently, among thirteen drugs targeting chromatin modifiers, EHMT2 inhibitors were highly effective in reducing ERMS cell viability. Our study demonstrates that ERMS cells are vulnerable to EHMT2 inhibitors and suggest that targeting the EHMT2-DKK1-b-catenin node holds promise for differentiation therapy.
Data availability
ChIP-Seq data has been deposited in GEO under the accession number GSE125960.RNA-Seq data been deposited in GEO under the accession number GSE142975.
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EHMT2 epigenetically suppresses Wnt signaling and is a potential target in embryonal rhabdomyosarcomaNCBI Gene Expression Omnibus, GSE125960.
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EHMT2 epigenetically suppresses Wnt signaling and is a potential target in embryonal rhabdomyosarcomaNCBI Gene Expression Omnibus, GSE142975.
Article and author information
Author details
Funding
National Medical Research Council (NMRC/OFIRG/0073/2018)
- Ernesto Guccione
- Reshma Taneja
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: All animal procedures used in this study were approved by the Institutional Animal Care and Use Committee (IACUC) at the National University of Singapore under the protocol # R18-0208.
Copyright
© 2020, Pal et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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EHMT2 epigenetically suppresses Wnt signaling and is a potential target in embryonal rhabdomyosarcoma
eLife 9:e57683.
https://doi.org/10.7554/eLife.57683
Further reading
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- Chromosomes and Gene Expression
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- Chromosomes and Gene Expression
- Structural Biology and Molecular Biophysics
Type II nuclear receptors (T2NRs) require heterodimerization with a common partner, the retinoid X receptor (RXR), to bind cognate DNA recognition sites in chromatin. Based on previous biochemical and overexpression studies, binding of T2NRs to chromatin is proposed to be regulated by competition for a limiting pool of the core RXR subunit. However, this mechanism has not yet been tested for endogenous proteins in live cells. Using single-molecule tracking (SMT) and proximity-assisted photoactivation (PAPA), we monitored interactions between endogenously tagged RXR and retinoic acid receptor (RAR) in live cells. Unexpectedly, we find that higher expression of RAR, but not RXR, increases heterodimerization and chromatin binding in U2OS cells. This surprising finding indicates the limiting factor is not RXR but likely its cadre of obligate dimer binding partners. SMT and PAPA thus provide a direct way to probe which components are functionally limiting within a complex TF interaction network providing new insights into mechanisms of gene regulation in vivo with implications for drug development targeting nuclear receptors.
