In the present study, we found that EZH1 depletion in MYCN-amplified neuroblastoma cells resulted in significant cell death as well as xenograft inhibition. EZH1 depletion decreased the level of H3K27me1; the interaction and protein stabilization of MYCN and EZH1 appear to play roles in epigenetic transcriptional regulation. Transcriptome analysis of EZH1-depleted cells resulted in downregulation of the cell cycle progression-related pathway. In particular, Gene Set Enrichment Analysis revealed downregulation of reactome E2F-mediated regulation of DNA replication along with key genes of this process, TYMS, POLA2, and CCNA1. TYMS and POLA2 were transcriptionally activated by MYCN and EZH1-related epigenetic modification. Treatment with the EZH1/2 inhibitor UNC1999 also induced cell death, decreased H3K27 methylation, and reduced the levels of TYMS in neuroblastoma cells. Previous reports indicated neuroblastoma cells are resistant to 5-fluorouracil (5-FU) and TYMS (encoding thymidylate synthetase) has been considered the primary site of action for folate analogues. Intriguingly, UNC1999 treatment significantly sensitized MYCN-amplified neuroblastoma cells to 5-FU treatment, suggesting that EZH inhibition could be an effective strategy for development of a new epigenetic treatment for neuroblastoma.

中文翻译：

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Polycomb EZH1 与 MYCN 协同调节神经母细胞瘤细胞的细胞周期/5-氟尿嘧啶敏感性

在本研究中，我们发现MYCN扩增的神经母细胞瘤细胞中的 EZH1 耗竭导致显着的细胞死亡和异种移植抑制。EZH1 耗尽降低了 H3K27me1 的水平；MYCN 和 EZH1 的相互作用和蛋白质稳定性似乎在表观遗传转录调控中发挥作用。EZH1 耗尽细胞的转录组分析导致细胞周期进程相关通路的下调。特别是，基因集富集分析揭示了反应组 E2F 介导的 DNA 复制调节以及该过程的关键基因TYMS、POLA2和CCNA1的下调。TYMS和POLA2被 MYCN 和 EZH1 相关的表观遗传修饰转录激活。用 EZH1/2 抑制剂 UNC1999 治疗也诱导细胞死亡，降低 H3K27 甲基化，并降低神经母细胞瘤细胞中TYMS的水平。以前的报告表明神经母细胞瘤细胞对 5-氟尿嘧啶 (5-FU) 具有抗性，TYMS（编码胸苷酸合成酶）被认为是叶酸类似物的主要作用部位。有趣的是，UNC1999 处理使 MYCN 扩增的神经母细胞瘤细胞对 5-FU 处理显着敏感，表明 EZH 抑制可能是开发神经母细胞瘤新表观遗传治疗的有效策略。