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Genome methylation defines EZH2 inhibitor resistance in neuroblastoma [I]

ABSTRACT: EZH2 is a H3K27 methylase and a target of cancer epigenetic treatments. We recently reported the oncogenic roles and NTRK1 (TRKA) epigenetic regulation by EZH2 in the MYCN-amplified aggressive neuroblastomas (NB) (Li et al., ONCOGENE, 2018). Here, we investigated the effects and function of small molecule EZH2 inhibitor (EZH2i) on aggressive NB model cell lines. We examined the antitumor effects of EZH2i using WST assay and colony formation assay. By EZH2i treatments, suppression of proliferation was observed in SK-N-SH and SK-N-BE cells (sensitive cells) dose-dependently, whereas it was not observed in IMR32 and NGP cells (resistant cells). FACS analysis showed apoptosis and G0/G1 cell cycle arrest in sensitive cells. Transcriptome analysis and GSEA indicated significant changes were observed in the gene set related to cell cycle arrest and differentiation in the sensitive cells. We selected genes induced at mRNA level by EZH2i only in the sensitive cells and confirmed tumor suppressor function in NB cells. Almost of the EZH2i-induced gene promoters were marked by H3K27me3 in MYCN-amplified NB cell lines. Interestingly, a part of the EZH2i-induced gene promoters have CpG islands and methylated in NB tumor samples registrated in databases. Further, combination of EPZ6438 and 5-aza-deoxycitide, resulted in effective suppression of proliferation in the EPZ6438-resistant 3 NB cell lines. Transcriptome/methylome analysis of the EPZ6438 and 5-aza-deoxycitide-treated NB cells revealed the combinational epigenetic regulation of the tumor suppressors and oncogene expression. Finally, methylome analysis of the promoter regions, e.g. VSTM2L, GPNMB, and TIMP3 CpG islands can be biomarkers of EPZ6438-registancy in unfavorable NB patients. These responsible CpG island methylation as biomarkers for the application of EZH2i/DNMTi combination therapy.

ORGANISM(S): Homo sapiens

PROVIDER: GSE143713 | GEO | 2022/08/01

REPOSITORIES: GEO

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Project description:Hepatocellular carcinoma (HCC) is the most common primary liver malignancy with cases increasing dramatically in the USA. Developing more effective targeted therapies for HCC is an urgent need. The FDA-approved DNA methyltransferase inhibitors (DNMTis) 5-azacytidine (5-aza-CR, Vidaza) and 5-aza-2’-deoxycytidine (5-aza-CdR, Decitabine) represented the first clinical breakthrough to target aberrant cancer epigenomes. However, the clinical efficacies of DNMTis are still limited, in part due to an “epigenetic switch” mechanism, in which a large group of genes demethylated by DNMTi treatment remain silenced by Polycomb Repressive Complex 2 (PRC2) occupancy. Overexpression of PRC2 subunits, especially EZH2, is correlated with poor patient survivor in HCC. In this study, we tested the combination of 5-Aza-CdR and the EZH2 inhibitor (EZH2i) GSK-126 in human HCC cell lines (SNU398, HepG2, and SNU475) on DNA methylation, nucleosome accessibility, and gene expression profiles. Compared with single agent treatments, all cell lines showed increased sensitivity after receiving both drugs concomitant with prolonged anti-proliferative changes and sustained reactivation of nascently silenced genes. The increased number of up-regulated genes, including tumor suppressors, were correlated with prolonged anti-proliferation effects and nucleosome accessibility but negatively correlated with gene promoter DNA methylation. Detailed epigenome analyses reveal a mechanistic rationale in which the combination treatment of 5-aza-CdR with an EZH2 inhibitor (EZH2i) activates demethylated promoters that are repressed by PRC2 occupancy. Furthermore, about 13.6% to 31% of genes down-regulated by DNA methylation in primary HCC tumors can be reactivated through this combination treatment scheme in vitro. Finally, combination treatment also exacerbates viral mimicry activation as well as leukocyte, lymphocyte and T cell mediated immunity, while most those genes or pathways were downregulated in over 50% of primary HCC tumors in TCGA dataset. Conclusion: we have linked the anti-tumor effects of DNMTi and EZH2i combination treatments to detailed epigenetic alterations in HCC cells, identified potential therapeutic targets and provided a rationale for combination treatment efficacy in HCC patients.

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Genome methylation defines EZH2 inhibitor resistance in neuroblastoma [I]

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