EZH2 promotes the expression of LPA1 by mediating microRNA-139 promoter methylation to accelerate the development of ovarian cancer

Background It has been known that ovarian cancer (OC) is a leading cause for women mortality globally. We aimed to analyze the underlying mechanism supporting that enhancer of zeste homolog 2 (EZH2) affected the development of OC via the involvement of microRNA-139 (miR-139)/transforming growth factor beta (TGF-[beta])/lysophosphatidic acid-1 (LPA1) axis. Methods High expression patterns of EZH2 and miR-139 and low LPA1 expression pattern in OC were evaluated using RT-qPCR and immunoblotting, while their correlation was assessed by the Spearman's rank and Pearson's correlation coefficient. Subsequently, dual-luciferase reporter gene assay was applied to validate the binding relationship between miR-139 and LPA1, while H3K27me enrichment was assessed by ChIP assay. After that, the effects of altered expression of EZH2, miR-194, or LPA1 on the cell biological functions and the expression pattern of TGF-related factors were evaluated. Results We found that EZH2 repressed the miR-139 expression pattern by recruiting H3K27me3 to promote miR-139 promoter methylation, while silencing of EZH2 suppressed in vitro cancer progression by increasing miR-139. LPA1 was a target of miR-139, and could activate the TGF-[beta] signaling pathway, which hastened the OC progression. miR-139-targeted inhibition of LPA1 and LPA1-activated TGF-[beta] signaling pathway were evidenced to be critical mechanisms underlying the effects of EZH2 on OC cells. Lastly, silencing of EZH2 inhibited the xenograft growth in vivo. Conclusions EZH2 could down-regulate miR-139 expression pattern by recruiting H3K27me3 to promote the miR-139 promoter methylation and activate the TGF-[beta] pathway by up-regulating LPA1, which contributed to the progression of OC. The current study may possess potentials for OC treatment. Keywords: Ovarian cancer, Tumor growth, Enhancer of zeste 2 polycomb repressive complex 2 subunit, microRNA-139