Genome-wide Profiling of H3K27ac binding in human MCF-7 cell lines. Genome-wide Profiling of H3K27ac binding in human MCF-7 cell lines

The histone methyltransferase EZH2 has been shown to function as a multifaceted molecule which can switch from a transcriptional repressor to an activator inducing a subset of genes that promote oncogenesis, including breast cancer. TfR-1, a key mediator in iron absorption, is highly expressed in a variety of tumors and associated with tumor grade, tumor stage and prognosis of patients. However, the known regulation mechanism of TfR-1 mainly remains on post-transcriptional level. To figure out whether TfR-1 expression is under epigenetic control, we examined the influence of EZH2 depletion and inhibition on TfR-1 expression in different subtypes of breast cancer cells. We discovered that EZH2 context-dependently modulates TfR-1 level and manipulates cellular iron uptake. Moreover, we identified TfR-1 as an NF-κB target gene which is positively regulated by EZH2 via constructing a complex with p65-p50 and transcription factor AP-1 in ER- cells. Inversely, TfR-1 is repressed by EZH2 and ER through histone methylation on its promoter in ER+ cells. These findings demonstrated an additional role of EZH2 in promoting breast cancer progression through iron homeostasis regulation and underscore the need for developing context-specific strategy for therapeutic targeting of epigenetic inhibition in breast cancer. Overall design: Examination of H3K27ac modification in MCF-7 cancer cell lines

组蛋白甲基转移酶EZH2（histone methyltransferase EZH2）作为一种多功能分子，已被证实可在转录抑制因子与转录激活因子之间切换，能够诱导包括乳腺癌在内的多种促肿瘤发生相关基因的表达。转铁蛋白受体1（TfR-1，transferrin receptor 1）是铁吸收过程中的关键介导因子，在多种肿瘤中呈高表达状态，且与患者的肿瘤分级、肿瘤分期及预后密切相关。然而，目前已知的TfR-1调控机制主要局限于转录后水平。为明确TfR-1的表达是否受表观遗传调控，我们检测了EZH2敲低与抑制对不同亚型乳腺癌细胞中TfR-1表达的影响。研究发现，EZH2可通过情境依赖性方式调控TfR-1的水平，并影响细胞的铁摄取能力。此外，我们在雌激素受体阴性细胞（ER- cells，estrogen receptor negative cells）中证实，TfR-1是核因子κB（NF-κB）的靶基因，EZH2可通过与p65-p50及转录因子AP-1形成复合物，对其进行正向调控。与之相反，在雌激素受体阳性细胞（ER+ cells，estrogen receptor positive cells）中，EZH2与雌激素受体可通过对TfR-1启动子区域进行组蛋白甲基化，从而抑制其表达。本研究结果揭示了EZH2通过调控铁稳态促进乳腺癌进展的额外功能，同时强调了针对乳腺癌表观遗传抑制治疗需开发情境特异性策略的必要性。实验整体设计：检测MCF-7癌细胞系中的H3K27乙酰化修饰（H3K27ac modification）