缺氧/HDAC3诱导的组蛋白标志H3K4Ac去乙酰化在上皮细胞间质转化和肿瘤转移中的作用

Metastasis causes most cancer deaths. Epithelial-mesenchymal transition (EMT) induced by hypoxia is an important mechanism to mediate tumor progression and metastasis in epithelial-derived malignant tumors. Molecular mechanisms to coordinately regulate hypoxia-induced EMT remain elusive. We recently demonstrated that HIF-1α-induced histone deacetylase 3 (HDAC3) is essential for hypoxia-induced EMT and metastatic phenotypes. Change of specific chromatin state (deacetylation of acetylated histone H3K4 (H3K4Ac)) is associated with EMT. H3K4Ac is the specific histone mark regulated by HDAC3, which are assigned to most, if not all, of the known EMT marker genes (Mol Cell, 2011). It will be critical to comprehensively screen these H3K4Ac-labeled genes and test whether they behave as EMT marker genes. Using a FaDu cell line from human pharyngeal squamous cell carcinoma, we've got the gene set precipitated by anti-H3K4Ac antibody and regulated by hypoxia through ChIP-sequencing approach. Preliminary bioinformatics analysis showed that, a considerable part of these genes are closely related with EMT phenotype and tumor metastasis. The purpose of this project is to identify these genes, assign their functions related to hypoxia-induced EMT and tumor metastasis, clarify molecular mechanisms to coordinately regulate hypoxia-induced EMT, and explore new approaches based on these new EMT mark genes or regulatory genes for tumor diagnosis and treatment.

肿瘤转移是导致恶性肿瘤患者死亡的首要因素。肿瘤内部缺氧激活缺氧诱导因子1（HIF-1）进而诱导上皮细胞间质转化（EMT），是促进肿瘤侵袭、引发转移的一个重要机制，但其分子调控机制尚不清楚。最近我们证实，组蛋白去乙酰化酶3（HDAC3）是HIF-1α的直接靶基因，其介导的基因启动子上组蛋白标志H3K4Ac的去乙酰化具有EMT标志基因特异性（Mol Cell，2011）。我们以上皮来源的人头颈癌细胞系为模型，通过染色质免疫沉淀测序技术，全面筛选了被H3K4Ac标记并受缺氧调节的基因，初步的生物信息学分析显示，该群基因与EMT和肿瘤转移密切相关。本课题旨在从该群基因中筛选出新的EMT关键基因，并结合动物模型及临床头颈癌样本，明确其在EMT和肿瘤发展与转移中的生物学功能及临床意义，阐明其调控EMT的分子机制，探索新EMT关键分子作为临床恶性肿瘤诊断的分子标志物或治疗靶标的可能性。

缺氧激活缺氧诱导因子 1 (HIF-1)进而诱导上皮细胞间质转化(Epithelial-Mesenchymal Transition，EMT)，是促进肿瘤侵袭、引发转移的一个重要机制。缺氧/HIF-1α激活的组蛋白去乙酰化酶3（HDAC3）可介导EMT标志基因启动子上组蛋白标记 H3K4Ac 的去乙酰化。本项目使用常氧或乏氧处理的FaDu细胞系，应用ChIP-seq方法，获取组蛋白标记H3K4Ac在人头颈癌细胞全基因组中的定位图谱，发现H3K4Ac主要位于基因转录起始点（Transcription starting site, TSS）附近。结合RNA测序获得的缺氧诱导的基因表达数据和HDAC3基因沉默细胞株，我们最终获得10个启动子附近被H3K4Ac标记并受到HDAC3调节的基因，如BMI1、GLI1、SMO、FOXF1、SIRT2等。过表达GLI1、SMO或SIRT2促进了头颈癌细胞的迁移和浸润，而基因沉默则发挥抑制作用。临床头颈癌组织样本的统计分析结果显示，GLI1/SMO在原发灶中共表达与转移相关，有望成为临床头颈癌治疗和预后的候选分子标志物。

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