Screen For Small Molecule Inhibitors Of PRC2 And The Mechanism Of The Inhibitors’ Anti-cancer Function

Cancer is an enemy of human health and a main cause of human death. Common cancer treatment methods are chemotherapy, radiation therapy and surgical resection. These methods often cause enormous suffering to patients because of their damage to normal tissues and their side effects. Thus, specific and effective targeted cancer therapies arouse great interest among people. Searching for specific targets in cancers and developing inhibitors of these targets are gaining more and more concerns among researchers in this field. With the development of epigenetics, the relationship between epigenetics and cancer is being revealed. Furthermore, some scientists hold the view that we are now entering an era of epigenetic cancer therapy.Polycomb repressive complex 2 (PRC2) is a main epigenetic repressor, which repressing transcription through trimethylation of H3K27 (H3K27me3). Also, PRC2 plays a part in tumorigenesis, development and/or maintenance of adult tissue specificity. The pivotal role of PRC2 in cancer makes it a therapeutic target for epigenetic cancer therapy. As PRC2’s function dependents on the complex formed by its core components, a group blocks the interaction of EZH2(enhancer of zeste homolog 2) and EED(embryonic ectoderm development) with a synthetic peptide that can bind to EED. The peptide can inhibit PRC2 activity and the proliferation of some PRC2-dependent cancer cells. However, natural compounds targeting the EZH2 EED interaction to disable PRC2 complex are scarcely reported. Here, we reported the screening and identification of natural compounds which could disrupt the EZH2-EED interaction. Firstly, freshly expressed and purified recombinant protein EED was immobilized as ligand in the CM5 sensor chip of the bio-molecular interaction analyzer Biacore 3000. Then we use Biacore 3000 to screen for natural compounds that bind to EED from the Natural Products Library. Then the competitive co-immunoprecipitation assay was performed to identify disrupts which could block the EZH2-EED interaction in vitro. One of these compounds, wedelolactone, binds to EED with a high affinity(Kd= 2.82 μM), blocks the EZH2-EED interaction in vitro. Further, we examined its effect on the degradation of PRC2 core components and PRC2 target and cancer-related genes. We found that wedelolactone could induce the degradation of PRC2 core components and modulate the expression of detected PRC2 downstream targets and cancer-related genes. Lastly, we examined its function on the proliferation, apoptosis, cell cycle and migration of PRC2-depedent cancer cells. Our results showed that wedelolactone could inhibit the proliferation and migration, induce apoptosis and cell cycle arrest of PRC2-dependent cancer cells.Taken together, wedelolactone and its derivatives which target the EZH2-EED interaction could be candidates for the treatment of PRC2-dependent cancer.