Bidirectional Effects of EZH2 Inhibitor in Endometriosis

Endometriosis is a complex disorder that afflicts many women with chronic pelvic pain and infertility. It is believed that polycomb group of proteins, such as enhancer of zeste homolog 2 (EZH2), which plays a major role in cancer, also might contribute to the etiology of endometriosis. We and others have shown upregulation of EZH2 in human endometriotic tissues. However, the factors responsible for this upregulation is unknown. This study hypothesizes that the components of peritoneal fluid (PF) plays a dynamic role in epigenetic pathways in endometriosis. To test this hypothesis we measured EZH2 expression and activity (activation of H3K27me3) in endometrial cells. Ishikawa (human endometrial) cells were treated with 1% PF from IRB‐approved and consented women with and without endometriosis (n=6–8/group age and cycle matched). A subset of cells was also treated with various concentrations of GSK126 (5 nM to 10 μM) either before or after PF treatment. Real‐time PCR was used to analyze EZH2 expression in these treated cells. Our results showed bidirectional effects of GSK126 on EZH2 and H3k27me3 expression, depending on the order of the drug treatment (before or after 24 hours of PF treatment) and the source of the PF (control vs endo). When cells were treated with endo PF, there was a 2–3 fold induction in EZH2 expression when cells were treated with endo PF compared to the media control. Surprisingly, there was a dose dependent increase in EZH2 mRNA expression with GSK126 pre‐treatment followed by the PF treatments. Almost a 9‐fold increase in EZH2 expression was observed when cells were pre‐treated with 2.5 μM GSK126 followed by control PF (*p<0.05), whereas pretreatment of GSK followed by endo PF had no such effects on EZH2 expression. However, when cells were pre‐treated with PF followed by the drug the EZH2 expression levels went down. Western blot of EZH2 and H3K27me3 showed similar findings. When MTT assay was performed to examine cell viability under the above experimental conditions, no significant changes in viability was observed at the 48 or 96 hour time points. These results suggest for an intermediate pathway modulated by the PF components that might be at play. The current studies are investigating the possible role for ARID1A mutation in the bidirectional effect of the EZH2 inhibitors in endometriosis.Support or Funding InformationPhRMA Foundation Pre Doctoral Fellowship in Pharmacology/ToxicologyThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.