Anti-EZH2 monoclonal antibody, clone FQS0418 Knockout Validated

Background Gastric cancer (GC) is a leading cause of cancer-related mortality worldwide, because of the low efficacy of current therapeutic strategies. Estrogen-related receptor gamma (ERR gamma) was previously showed as a suppressor of GC. However, the mechanism and effective therapeutic method based on ERR gamma is yet to be developed. Methods The expression levels of ERR gamma, EZH2, and FOXM1 were detected by immunohistochemistry, qRT-PCR, and western blot. The regulatory mechanisms of ERR gamma and FOXM1 were analyzed by ChIP, EMSA, and siRNA. The effects of EZH2 inhibitor (GSK126) or/and ERR gamma agonist (DY131) on the tumorigenesis of gastric cancer cell lines were examined by cell proliferation, transwell migration, wound healing, and colony formation assays. Meanwhile, the inhibitory effects of GSK126 or/and DY131 on tumor growth were analyzed by xenograft tumor growth assay. Results The expression of ERR gamma was suppressed in tumor tissues of GC patients and positively correlated with prognosis, as opposed to that of EZH2 and FOXM1. EZH2 transcriptionally suppressed ERR gamma via H3K27me3, which subsequently activated the expression of master oncogene FOXM1. The combination of GSK126 and DY131 synergistically activated ERR gamma expression, which subsequently inhibited the expression of FOXM1 and its regulated pathways. Synergistic combination of GSK126 and DY131 significantly inhibited the tumorigenesis of GC cell lines and suppressed the growth of GC xenograft. Conclusion The FOXM1 signaling pathway underlying the ERR gamma-mediated gastric cancer suppression was identified. Furthermore, combined treatment with EZH2 inhibitor and ERR gamma agonist synergistically suppressed GC progression by inhibiting this signaling pathway, suggesting its high potential in treating GC patients.

The majority of women diagnosed with epithelial ovarian cancer eventually develop recurrence, which rapidly evolves into chemoresistant disease. Persistence of ovarian cancer stem cells (OCSC) at the end of therapy may be responsible for emergence of resistant tumors. In this study, we demonstrate that in OCSC, the tumor suppressor disabled homolog 2-interacting protein (DAB2IP) is silenced by EZH2-mediated H3K27 trimethylation of the DAB2IP promoter. CRISPR/Cas9-mediated deletion of DAB2IP in epithelial ovarian cancer cell lines upregulated expression of stemness-related genes and induced conversion of non-CSC to CSC, while enforced expression of DAB2IP suppressed CSC properties. Transcriptomic analysis showed that overexpression of DAB2IP in ovarian cancer significantly altered stemness-associated genes and bioinformatic analysis revealed WNT signaling as a dominant pathway mediating the CSC inhibitory effect of DAB2IP. Specifically, DAB2IP inhibited WNT signaling via downregulation of WNT5B, an important stemness inducer. Reverse phase protein array further demonstrated activation of noncanonical WNT signaling via C-JUN as a downstream target of WNT5B, which was blocked by inhibiting RAC1, a prominent regulator of C-JUN activation. Coadministration of EZH2 inhibitor GSK126 and RAC1 inhibitor NSC23766 suppressed OCSC survival in vitro and inhibited tumor growth and increased platinum sensitivity in vivo. Overall, these data establish that DAB2IP suppresses the cancer stem cell phenotype via inhibition of WNT5B-induced activation of C-JUN and can be epigenetically silenced by EZH2 in OCSC. Targeting the EZH2/DAB2IP/C-JUN axis therefore presents a promising strategy to prevent ovarian cancer recurrence and has potential for clinical translation. Significance: These findings show that combining an epigenetic therapy with a noncanonical WNT signaling pathway inhibitor has the potential to eradicate ovarian cancer stem cells and to prevent ovarian cancer recurrence.