长链非编码 RNA HOTAIRM1 通过上调 HOXA1 并将 G9a/EZH2/Dnmts 从 HOXA1 基因上隔离，从而促进胶质母细胞瘤中肿瘤的生长和侵袭。
Over-expressed lncRNA HOTAIRM1 promotes tumor growth and invasion through up-regulating HOXA1 and sequestering G9a/EZH2/Dnmts away from the HOXA1 gene in glioblastoma multiforme.
机构信息
China National Clinical Research Center for Neurological Diseases, Beijing Tian Tan Hospital, Capital Medical University, 6 Tiantan Xili, Dongcheng District, Beijing, 100050, China.
Department of Histology and Embryology of Basic Medicine College, Jilin University, Changchun, Jilin Province, China.
出版信息
J Exp Clin Cancer Res. 2018 Oct 30;37(1):265. doi: 10.1186/s13046-018-0941-x.
BACKGROUND
Glioblastoma multiforme (GBM) is the common primary brain tumor classified the most malignant glioma. Long non-coding RNAs (LncRNAs) are important epigenetic regulators with critical roles in cancer initiation and progression. LncRNA HOTAIRM1 transcribes from the antisense strand of HOXA gene cluster which locus in chromosome 7p15.2. Recent studies have shown that HOTAIRM1 is involved in acute myeloid leukemia and colorectal cancer. Here we sought to investigate the role of HOTAIRM1 in GBM and explore its mechanisms of action.
METHODS
The expressions of HOTAIRM1 and HOXA1 in GBM tissues and cells were determined by qRT-PCR, and the association between HOTAIRM1, HOXA1 transcription and tumor grade were analyzed. The biological function of HOTAIRM1 in GBM was evaluated both in vitro and in vivo. Chromatin immunoprecipitation (ChIP) assay and quantitative Sequenom MassARRAY methylation analysis were performed to explore whether HOTAIRM1 could regulate histone and DNA modification status of the HOXA1 gene transcription start sites (TSS) and activate its transcription. ChIP and RNA-ChIP were further performed to determine the molecular mechanism of HOTAIRM1 in epigenetic regulation of the HOXA1 gene.
RESULTS
HOTAIRM1 was abnormally up-regulated in GBM tissues and cells, and this up-regulation was correlated with grade malignancy in glioma patients. HOTAIRM1 silencing caused tumor suppressive effects via inhibiting cell proliferation, migration and invasion, and inducing cell apoptosis. In vivo experiments showed knockdown of HOTAIRM1 lessened the tumor growth. Additionally, HOTAIRM1 action as regulating the expression of the HOXA1 gene. HOXA1, as an oncogene, it's expression levels were markedly elevated in GBM tissues and cell lines. Mechanistically, HOTAIRM1 mediated demethylation of histone H3K9 and H3K27 and reduced DNA methylation levels by sequester epigenetic modifiers G9a and EZH2, which are H3K9me and H3K27me specific histone methyltransferases, and DNA methyltransferases (DnmTs) away from the TSS of HOXA1 gene.
CONCLUSIONS
We investigated the potential role of HOTAIRM1 to promote GBM cell proliferation, migration, invasion and inhibit cell apoptosis by epigenetic regulation of HOXA1 gene that can be targeted simultaneously to effectively treat GBM, thus putting forward a promising strategy for GBM treatment. Meanwhile, this finding provides an example of transcriptional control over the chromatin state of gene and may help explain the role of lncRNAs within the HOXA gene cluster.
背景
多形性胶质母细胞瘤（GBM）是最恶性的神经胶质瘤中常见的原发性脑肿瘤。长链非编码 RNA（lncRNA）是重要的表观遗传调控因子，在癌症的发生和发展中起着关键作用。LncRNA HOTAIRM1 从 HOXA 基因簇的反义链转录，该基因位于染色体 7p15.2。最近的研究表明，HOTAIRM1 参与了急性髓细胞白血病和结直肠癌。在这里，我们试图研究 HOTAIRM1 在 GBM 中的作用，并探讨其作用机制。
方法
通过 qRT-PCR 检测 GBM 组织和细胞中 HOTAIRM1 和 HOXA1 的表达，并分析 HOTAIRM1、HOXA1 转录与肿瘤分级的关系。通过体外和体内实验评估 HOTAIRM1 在 GBM 中的生物学功能。进行染色质免疫沉淀（ChIP）实验和定量 Sequenom MassARRAY 甲基化分析，以探讨 HOTAIRM1 是否可以调节 HOXA1 基因转录起始位点（TSS）的组蛋白和 DNA 修饰状态并激活其转录。进一步进行 ChIP 和 RNA-ChIP 实验，以确定 HOTAIRM1 在 HOXA1 基因的表观遗传调控中的分子机制。
结果
HOTAIRM1 在 GBM 组织和细胞中异常上调，且这种上调与胶质瘤患者的恶性程度相关。HOTAIRM1 沉默通过抑制细胞增殖、迁移和侵袭，并诱导细胞凋亡，发挥肿瘤抑制作用。体内实验表明，敲低 HOTAIRM1 可减轻肿瘤生长。此外，HOTAIRM1 作为调节 HOXA1 基因表达的作用。HOXA1 作为一种癌基因，在 GBM 组织和细胞系中表达水平显著升高。在机制上，HOTAIRM1 通过募集表观遗传修饰剂 G9a 和 EZH2 ，将组蛋白 H3K9 和 H3K27 的去甲基化以及 DNA 甲基化水平降低，H3K9me 和 H3K27me 是特异性组蛋白甲基转移酶，DNA 甲基转移酶（DnmTs）远离 HOXA1 基因的 TSS。
结论
我们通过表观遗传调控 HOXA1 基因，研究了 HOTAIRM1 促进 GBM 细胞增殖、迁移、侵袭和抑制细胞凋亡的潜在作用，这可以同时作为有效治疗 GBM 的靶点，从而为 GBM 的治疗提出了有前途的策略。同时，这一发现为基因染色质状态的转录控制提供了一个范例，并可能有助于解释长链非编码 RNA 在 HOXA 基因簇中的作用。
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