脑胶质瘤SHG-44细胞MGMT基因甲基化状态及其与细胞对烷化剂药物耐药性关系的研究

目的探讨人脑胶质瘤SHG-44细胞O（6）-甲基鸟嘌呤DNA甲基转移酶（MGMT）基因启动子甲基化状态与其蛋白表达以及细胞对烷化剂药物耐药性的相关性。方法取处于对数生长期的人脑胶质瘤SHG-44和U251细胞,分别加入5-氮-2＇脱氧胞苷（5-Aza-CdR）培养6d后收集细胞,同时以未加5-Aza-CdR的正常培养细胞作为对照。提取细胞基因组DNA,采用甲基化特异性PCR（MSP）检测MGMT基因的甲基化状态,并利用蛋白质印迹方法检测MGMT蛋白的表达。将收集的细胞分为3组,分别加入浓度为125、100、75、50、25、15、10μg／ml的尼莫司汀（ACNU）和50、25、15、10、5、2．5、1μg/ml的替莫唑胺（TMZ）以及等量的完全培养液（阴性对照）,采用噻唑蓝（MTT）法分别检测细胞对烷化剂药物的敏感性,以细胞存活50％时所对应的药物浓度（IC50值）作为衡量细胞对药物敏感性的指标,实验重复3次。结果正常培养的SHG-44细胞MGMT基因启动子呈甲基化状态,MGMT蛋白表达缺失,对ACNU和TMZ的IC50值分别为30、11μg／ml,表现为对烷化剂药物敏感;用5-Aza-CdR处理后,SHG-44细胞MGMT基因启动子成功脱甲基化,MGMT蛋白恢复表达,其对ACNU和TMZ的IC50值分别升高了2．5和3．1倍（均P〈0．05）,对烷化剂药物的敏感性发生逆转。而正常培养和5-Aza-CdR处理的U251细胞MGMT基因启动子均呈未甲基化状态,都能表达MGMT蛋白,并且均表现为对ACNU和TMZ烷化剂药物耐药。结论MGMT基因甲基化状态能稳定地反映细胞诱导MGMT蛋白表达的能力,并有可能成为预测肿瘤组织对烷化剂化疗药物敏感性的分子标记。     

miR-130b在胶质瘤对替莫唑胺耐药中的作用

目的:探讨微小RNA-130b(microRNA-130b,miR-130b)在胶质瘤细胞中的表达及其调控体外胶质瘤细胞对替莫唑胺(temozolomide,TMZ)耐药中的作用。方法:利用RT-qPCR法检测miR-130b在胶质瘤细胞株U251、SHG-44和U87中的表达水平;计算TMZ对不同胶质瘤细胞株(U251、SHG-44和U87)的半数抑制浓度(IC_(50));通过不同浓度梯度的TMZ作用于体外U251细胞,从而获得相对稳定的对TMZ耐药的U251(U251/TMZ resistance,U251/TR)细胞,计算TMZ对U251/TR细胞的IC_(50)及耐药指数(resistance factor,RF);使用miR-130b模拟物(miR-130b mimics)和miR-130b抑制物(miR-130b inhibitor)瞬时转染体外胶质瘤细胞;CCK-8法检测体外胶质瘤细胞的活力;流式细胞术检测胶质瘤细胞凋亡;通过生物信息学工具分析miR-130b可能的靶基因,萤光素酶报告基因实验测定萤光素酶活性;电泳迁移率变动分析检测核因子κB(nuclear factor-κB,NF-κB)的活性;Western blot法测定肿瘤坏死因子α(tumor necrosis factor-α,TNF-α)、Bcl-2、X连锁凋亡抑制蛋白(X-linked inhibitor of apoptosis protein,XIAP)和survivin蛋白在胶质瘤细胞中的表达水平。结果:TMZ对不同胶质瘤细胞株(U251、SHG-44和U87)的IC_(50)分别为54.8、94.8和149.6μmol/L;TMZ对U251/TR细胞的IC_(50)为(446.5±61.3)μmol/L,其RF为8.1;转染miR-130b mimics可明显增强TMZ对U251/TR细胞的生长抑制和凋亡诱导作用;转染miR-130b inhibitor可显著抑制TMZ对U251/TR细胞的生长抑制和凋亡诱导作用;萤光素酶报告基因实验验证TNF-α是miR-130b的直接作用靶点;与mimics NC组相比,转染miR-130b mimics后U251/TR细胞中的NF-κB活性及TNF-α、Bcl-2、XIAP和survivin蛋白表达均明显下调;与inhibitor NC组相比,转染miR-130b inhibitor后U251细胞中的NF-κB活性及TNF-α、Bcl-2、XIAP和survivin蛋白表达均显著上调(P0.05);NF-κB抑制剂Bay 11-7082可增强TMZ对U251/TR细胞凋亡的诱导作用。结论:miR-130b在耐药型胶质瘤细胞中表达下调,并通过靶向调控TNF-α/NF-κB通路增强TMZ对体外胶质瘤细胞的作用。     

Zeste基因增强子同源物2通过调控Wnt/β-catenin信号通路影响脑胶质瘤细胞凋亡

目的:探讨zeste基因增强子同源物2(EZH2)通过调控Wnt/β-catenin信号通路对脑胶质瘤细胞凋亡的影响。方法:以RT-q PCR和Western blot检测胶质瘤U87、H4和U251细胞及正常人脑星形细胞(NHA)中EZH2的表达水平。在H4细胞中转染EZH2 siRNA和siRNA control,MTT测定细胞活力,流式细胞术测定细胞凋亡,分光光度计法检测caspase-3的活性,Western blot检测Wnt/β-catenin信号通路中关键蛋白β-连环蛋白(β-catenin)和下游靶分子c-Myc的蛋白表达。用Wnt/β-catenin信号通路激活剂处理转染EZH2 siRNA的H4细胞,流式细胞术测定细胞凋亡,Western blot测定β-catenin和c-Myc的表达。结果:胶质瘤U87、H4和U251细胞中EZH2的mRNA和蛋白水平均明显高于NHA(P0.05),并且H4细胞中EZH2 mRNA和蛋白水平高于U87和U251细胞(P0.05)。EZH2 siRNA可以明显下调H4细胞中EZH2的mRNA和蛋白水平。EZH2表达下调后的H4细胞从48 h开始细胞活力降低,并且细胞凋亡率也明显升高,细胞中caspase-3活性也明显升高(P0.05),同时EZH2表达下调还可以抑制β-catenin和c-Myc的表达。Wnt/β-catenin信号通路的激活剂可以减少EZH2诱导的H4细胞凋亡,降低细胞中caspase-3的活性。结论:EZH2在脑胶质瘤细胞中过度表达,下调其表达可以通过抑制Wnt/β-catenin信号通路的激活而诱导胶质瘤细胞凋亡。     

LRIG1 enhances the radiosensitivity of radioresistant human glioblastoma U251 cells via attenuation of the EGFR/Akt signaling pathway

The radiotherapy as a local and regional modality is widely applied in treatment of glioma, but most glioblastomas are commonly resistant to irradiation treatment. It remains challengeable to seek out efficient strategies to conquer the resistance of human glioblastoma cells to radiotherapy. Leucine-rich repeats and immunoglobulin-like domains protein 1 (LRIG1) is a newly discovered tumor suppressor which involved in regulation of chemosensitivity in various human cancer cells. In the present study, we established a radioresistant U251 cell line (U251R) to investigate the role of LRIG1 in regulation of radiosensitivity in human glioblastoma cells. Significantly decreased expression level of LRIG1 and enhanced expression of EGFR and phosphorylated Akt were detected in U251R cells compared with the parental U251 cells. U251R cells exhibited an advantage in colony formation ability, which accompanied by remarkably reduced X-ray-induced γ-H2AX foci formation and cell apoptosis. LRIG1 overexpression significantly inhibited the colony formation ability of U251R cells and obviously enhanced X-ray-inducedγ-H2AX foci formation and cell apoptosis. In addition, up-regulated expression of LRIG1 suppressed the expression level of EGFR and phosphorylated Akt protein. Our results demonstrated that LRIG1 expression was related to the radiosensitivity of human glioblastoma cells and may play an important role in the regulation of cellular radiosensitivity of human glioblastoma cells through the EGFR/Akt signaling pathway.     

MiR-16 modulate temozolomide resistance by regulating BCL-2 in human glioma cells

Temozolomide (TMZ) with radiotherapy is the current standard of care for newly diagnosed glioma. However, glioma patients who are treated with the drug often develop resistance to it and some other drugs. Recently studies have shown that microRNAs (miRNAs) play an important role in drug resistance. In present study, we first examined the sensitivity to temozolomide in six glioma cell lines, and established a resistant variant, U251MG/TR cells from TMZ-sensitive glioma cell line, U251MG. We then performed a comprehensive analysis of miRNA expressions in U251MG/TR and parental cells using cancer microRNA PCR Array. Among the downregulated microRNAs was miR-16, members of miR-15/16 family, whose expression was further validated by qRT-PCR in U251MG/TR and U251MG cells. The selective microRNA, miR-16 mimics or inhibitor was respectively transfected into U251MG/TR cells and AM38 cell. We found that treatment with the mimics of miR-16 greatly decreased the sensitivity of U251MG/TR cells to temozolomide, while sensitivity to these drugs was increased by treatment with the miR-16 inhibitor. In addition, the downregulation of miR-16 in temozolomide-sensitive AM38 cells was concurrent with the upregulation of Bcl-2 protein. Conversely, overexpression of miR-16 in temozolomide-resistant cells inhibited Bcl-2 expression and decreased temozolomide resistance. In conclusion, MiR-16 mediated temozolomide-resistance in glioma cells by modulation of apoptosis via targeting Bcl-2, which suggesting that miR-16 and Bcl-2 would be potential therapeutic targets for glioma therapy.     

Targeting Aurora kinase B attenuates chemoresistance in glioblastoma via a synergistic manner with temozolomide

BackgroundRecent studies have demonstrated that aberrant expression or activation of kinases results in oncogenesis of a wide range of cancers including GBM. Inhibition of kinases expression induces a reduction of therapy resistance. In this study, we investigate the underlying mechanism by which glioblastoma (GBM) cells acquire resistance to Temozolomide (TMZ) through Aurora kinase B (AURKB) thus to identify novel therapeutic targets and prognostic biomarkers for GBM.MethodsAURKB was identified as a key candidate kinase-encoding gene in chemoresistance regulation by using kinome-wide bioinformatic analysis. Afterwards, the potential biological functions of AURKB in oncogenesis and chemoresistance were investigated by lentivirus-dependent silencing of AURKB combined with qRT-PCR, western blot and in vivo intra-cranial xenograft mice models. Additionally, immunohistochemistry (IHC) assays were performed to explore the clinical significance of AURKB in glioma patients. Lastly, Chou-Talalay method was used to confirm the synergistic effect of TMZ combined with AURKB inhibitor.ResultsAURKB was among the most significantly up-regulated kinase-coding genes in TMZ resistant GBM cells according to database GSE68029, moreover, an increased expression of AURKB was closely associated with poor prognosis in glioma and GBM patients. AURKB knock-down resensitized U87 resistant cells to TMZ both in vitro and in vivo. Additionally, the combination of TMZ and Hesperadin, a specific AURKB inhibitor, significantly suppressed the proliferation of TMZ resistant GBM cells thus dramatically prolonged the survival of xenograft mice viaa synergistic effect with TMZ.ConclusionElevated AURKB expression was strongly correlated to TMZ resistant acquisition and poor prognosis, furthermore, targeting AURKB would be a potential therapeutic target for GBM patients.     

Expression of complement membrane regulators membrane cofactor protein (CD46), decay accelerating factor (CD55), and protectin (CD59) in human malignant gliomas.

Gliomas are malignant brain tumors, which, despite recent progress in surgical and radiological treatment, still have a poor prognosis. Since gliomas apparently resist immunological clearance mechanisms, we became interested in examining bow gliomas resist killing by the human complement system. The resistance of human cells to complement-mediated damage is, in large part, mediated by specific inhibitors of complement:membrane cofactor protein (CD46), decay-accelerating factor (CD55), and protectin (CD59). In the present study we examined the expression of complement regulators in 14 human glioma tumors and in 7 glioma cell lines (U251, U87, HS683, U373, U138, U118, and H2). Protectin was found to be strongly expressed by all glioma tumors and cell lines. Northern blotting analysis demonstrated the typical pattern of four to five protectin mRNAs in the glioma cells. Except for blood vessels, the expression of decay-accelerating factor was weak or absent in the tumors in situ, whereas in the cell lines its expression varied, ranging from negative to intermediate. Membrane cofactor protein was moderately expressed by all the cell lines but only weakly in the tumors. Cell-killing experiments demonstrated that the glioma cell lines were exceptionally resistant to C-mediated lysis. Five of the seven cell lines (U373, HS683, U118, U138, and H2) resisted complement lysis under conditions where most other cell lines were sensitive to killing. Neutralization experiments using specific monoclonal antibodies indicated that protectin was functionally the most important complement regulator in the glioma cells. The killing of the U87 and U251 cells could be significantly increased by a blocking anti-protectin monoclonal antibody, whereas for the other cell lines only moderate or no response was observed. The H2 cell line resisted killing by all antibodies and by complement. These results show that protectin is the most important complement regulator on human glioma cells. The exceptional complement resistance of some glioma cell lines suggests that they may utilize other, hitherto less well characterized, mechanisms to resist complement killing.     

Micro-RNA29b enhances the sensitivity of glioblastoma multiforme cells to temozolomide by promoting autophagy

To explore whether or not aberrant expression of miR-29b in glioblastoma multiforme (GBM) cells was associated with temozolomide (TMZ) resistance and to elucidate potential underlying mechanisms. Upregulation of miR-29 in GBM cells was achieved by transfecting miR-29b mimics. Changes in cell viability were measured by using CCK-8 assays. Flow cytometry and TUNEL assays were used to quantify the number of apoptotic cells. The expression levels of apoptosis-related proteins as well as autophagy-associated proteins, and the expression levels of both apoptotic and autophagic genes were determined by Western blotting. Autophagy flux was monitored by transfecting mRFP-GFP-LC3 adenovirus. We halted autophagy by introducing Atg 5-specific siRNA or the autophagy inhibitor Bafilomycin A1 (Baf-A1). We also employed a GBM xenograft mice model to confirm the role of miR-29b in vivo. miR-29b overexpression induced inhibition of cell viability, and also induced apoptosis and autophagy in U251 and U87MG cells. Furthermore, upregulation of miR-29b was able to potentiate the level of antitumor activity of TMZ against tested cells. We also found that autophagy induced by miR-29b, at least partially, contributed to the increase of TMZ sensitivity in GBM cells. As was evidenced by blockade of autophagy, the application of Atg 5 siRNA or Baf-A1 was able to significantly reverse these effects. Consistent with observations in vitro, findings of in vivo assessment also confirmed that overexpression of miR-29b was able to effectively halt tumor growth and enhance the antitumor activity of TMZ. miR-29b potentiates TMZ sensitivity against GBM cells by inducing autophagy and the combined use of miR-29 mimic and TMZ might represent a potential therapeutic strategy for GBM patients.     

诺帝对恶性胶质瘤细胞株U87MG生物学行为的影响及差异表达蛋白质组分析

目的观察诺帝对人恶性胶质母细胞瘤细胞株U87MG及其移植瘤生物学行为的影响,分析和鉴定诺帝诱导U87MG细胞分化时高表达的差异蛋白质。方法采用自行研制的化合物诺帝（纯度为99．87％）诱导U87MG细胞分化,再用U87MG细胞原位移植瘤模型裸鼠腹腔注射诺帝,观察肿瘤生长情况和胶质纤维酸性蛋白（GFAP）表达改变。应用蛋白质双向电泳和PDQuest7．1软件对比分析诺帝诱导分化前后表达的差异蛋白质,采用基质辅助激光解析离子化飞行时间质谱进行鉴定并分析其功能。结果诺帝能显著抑制U87MG细胞体外增殖和原位移植瘤的生长（P〈0．01）并诱导其分化,U87MG细胞体外分化后高表达的差异蛋白质包括增殖相关基因A、交替拼接因子3、真核转录启动因子5A、丝切蛋白1、13半乳糖苷酶结合凝集素、甘油醛-3-磷酸脱氢酶、α烯醇化酶和一种未知蛋白。结论诺帝对人胶质母细胞瘤细胞株U87MG具有诱导分化的作用,其过程涉及多种蛋白质的表达改变,其中大部分蛋白质表达下调,这些蛋白质参与细胞增殖、代谢、分化、凋亡及基因转录的调控。     

格列本脲对胶质母细胞瘤活性及细胞内酸碱平衡的影响

目的:探讨格列本脲对胶质母细胞瘤活性及细胞内酸碱变化的影响。方法:使用不同浓度的格列本脲(Glib)处理人胶质瘤细胞株U251和U87,通过CCK-8法筛选有效剂量;随后将实验分成对照组和药物处理组,划痕实验检测细胞迁移情况,细胞p H指示荧光探针检测细胞内p H变化,Western blot测定内向整流钾离子通道4.1(Kir4.1)和单羧酸转运蛋白1(MCT1)的表达情况。结果:CCK-8法检测结果显示,Glib作用于U251细胞和U87细胞48 h的半数抑制浓度(IC50)分别为400.20μmol/L和553.70μmol/L,且在100~1 600μmol/L的浓度区间范围内,Glib抑制U251细胞活力,在50~1 600μmol/L的浓度区间范围内,Glib抑制U87细胞活力,两者均呈浓度依赖性(P0.05);与对照组相比较,Glib不仅能够抑制细胞迁移(P0.05),抑制作用与药物浓度呈正相关(P0.05),而且使实验组细胞内荧光强度减弱(P0.05),提示随着药物浓度的增高,细胞内p H值逐渐下降(P0.05);实验组细胞的Kir4.1和MCT1蛋白含量明显降低,均有浓度依赖性(P0.05)。结论:Glib在一定剂量范围内通过下调Kir4.1和MCT1表达诱导细胞内环境酸化,抑制胶质瘤细胞生长。     

MGMT表达与替莫唑胺治疗多形性胶质母细胞瘤耐药的关系

多形性胶质母细胞瘤是中枢神经系统最常见的恶性肿瘤,而且在胶质瘤中恶性程度最高.替莫唑胺为治疗多形性胶质母细胞瘤的新型烷化剂类口服化疗药物,研究表明替莫唑胺的耐药机制与O6-甲基鸟嘌呤-DNA甲基转移酶(MGMT)的表达相关.了解多形性胶质母细胞瘤应用替莫唑胺治疗的耐药性与MGMT表达的相关性对临床治疗很有帮助.     

EZH1 and EZH2 cogovern histone H3K27 trimethylation and are essential for hair follicle homeostasis and wound repair

Polycomb protein group (PcG)-dependent trimethylation on H3K27 (H3K27me3) regulates identity of embryonic stem cells (ESCs). How H3K27me3 governs adult SCs and tissue development is unclear. Here, we conditionally target H3K27 methyltransferases Ezh2 and Ezh1 to address their roles in mouse skin homeostasis. Postnatal phenotypes appear only in doubly targeted skin, where H3K27me3 is abolished, revealing functional redundancy in EZH1/2 proteins. Surprisingly, while Ezh1/2-null hair follicles (HFs) arrest morphogenesis and degenerate due to defective proliferation and increased apoptosis, epidermis hyperproliferates and survives engraftment. mRNA microarray studies reveal that, despite these striking phenotypic differences, similar genes are up-regulated in HF and epidermal Ezh1/2-null progenitors. Featured prominently are (1) PcG-controlled nonskin lineage genes, whose expression is still significantly lower than in native tissues, and (2) the PcG-regulated Ink4a/Inkb/Arf locus. Interestingly, when EZH1/2 are absent, even though Ink4a/Arf/Ink4b genes are fully activated in HF cells, they are only partially so in epidermal progenitors. Importantly, transduction of Ink4b/Ink4a/Arf shRNAs restores proliferation/survival of Ezh1/2-null HF progenitors in vitro, pointing toward the relevance of this locus to the observed HF phenotypes. Our findings reveal new insights into Polycomb-dependent tissue control, and provide a new twist to how different progenitors within one tissue respond to loss of H3K27me3.     

Upregulation of tissue inhibitor of metalloproteinases (TIMP)-2 promotes matrix metalloproteinase (MMP)-2 activation and cell invasion in a human glioblastoma cell line

Local invasiveness is a characteristic feature of glioblastoma that makes surgical resection nearly impossible and accounts in large part for its poor prognosis. To identify mechanisms underlying glioblastoma invasion and motility, we used Transwell invasion chambers to select for a more potently invasive subpopulation of U87MG human glioblastoma cells. The stable population of tumor cells (U87-C1) obtained through this in vitro selection process were three times more invasive than parental U87MG cells and demonstrated faster monolayer wound healing and enhanced radial motility from cell spheroids. This enhanced invasiveness was associated with an 80% increase in matrix metalloproteinase 2 (MMP-2) activation. No differences in expression levels of pro-MMP-2, membrane-type matrix metalloproteinase I (MT1-MMP), or integrin alphavbeta3 (mediators of MMP-2 activation) were detected. However, U87-C1 cells exhibited two-fold elevation of tissue inhibitor of metalloproteinases (TIMP)-2 mRNA and protein relative to parental cells. Exogenous addition of comparable levels of purified TIMP-2 to parental U87MG cells increased MMP-2 activation and invasion. Similarly, U87MG cells engineered to overexpress TIMP-2 at the same levels as U87-C1 cells also demonstrated increased MMP-2 activation, indicating that an increase in physiological levels of TIMP-2 can promote MMP-2 activation and invasion in glioblastoma cells. However, exogenous administration or recombinant overexpression of higher amounts of TIMP-2 in U87MG cells resulted in inhibition of MMP-2 activation. These results demonstrate that the complex balance between TIMP-2 and MMP-2 is a critical determinant of glioblastoma invasion, and indicate that increasing TIMP-2 in glioblastoma patients may potentially cause adverse effects, particularly in tumors containing high levels of MT1-MMP and MMP-2.     

Knockdown of microRNA-127 reverses adriamycin resistance via cell cycle arrest and apoptosis sensitization in adriamycin-resistant human glioma cells

The aim of this study was to investigate signaling pathways for reversal of microRNA-127-mediated multi-drug resistance (MDR) in gliomas cells. Adriamycin-resistant glioma cell lines U251/adr and U87-MG/adr were established and we found that anti-microRNA-127 markedly reduced microRNA-127 expression levels in a time-dependent manner, leading to distinct inhibition of cell proliferation and increased apoptosis and the content of intracellular Rh123. Silencing of microRNA-127 significantly increased the sensitivity of U251/ADR and U87-MG/adr cells to adriamycin, compared to cells transfected with negative control siRNA. Silencing of microRNA-127 also significantly reduced the mRNA and protein expression levels of MDR1 and MRP1, which are major ATP-binding cassette (ABC) transporter linked to multi-drug resistance in cancer cells. And Runx2, p53, bcl-2 and survivin, which are important role in cell apoptosis, also markedly changed after microRNA-127 silencing. In addition, down-regulating microRNA-127 decreased the level of phosphorylated-Akt. Our data indicate that down-regulation of micorRNA-127 can trigger apoptosis and overcome drug resistance of gliomas cells. Therefore, this resistance of adriamycin in gliomas can be cancelled by silencing expression of microRNA-127.     

MIR‐137 Suppresses Growth and Invasion,is Downregulated in Oligodendroglial Tumors and Targets CSE1L

MicroRNA‐137 (miR‐137) expression has been reported to be decreased in astrocytic tumors in two expression profiling studies but its role in the pathogenesis of oligodendroglial tumors is still limited. In this study, we demonstrate that miR‐137 expression is significantly downregulated in a cohort of 35 oligodendroglial tumors and nine glioma cell lines compared with normal brains. Lower miR‐137 expression is associated with shorter progressive‐free survival and overall survival. Restoration of miR‐137 expression in an oligodendroglial cells TC620, and also glioblastoma cells of U87 and U373 significantly suppressed cell growth, anchorage‐independent growth, as well as invasion. Demethylation and deacetylation treatments resulted in upregulation of miR‐137 expression in TC620 cells. In silico analysis showed that CSE1 chromosome segregation 1‐like (yeast) (CSE1L) is a potential target gene of miR‐137. Luciferase reporter assay demonstrated that miR‐137 negatively regulates CSE1L by interaction between miR‐137 and complementary sequences in the 3′ UTR of CSE1L. Immunohistochemistry revealed that CSE1L is upregulated in oligodendroglial tumors. Knockdown of CSE1L resulted in similar outcomes as overexpressing miR‐137 in oligodendroglioma cells and glioblastoma cells. Overall, our data suggest that miR‐137 regulates growth of glioma cells and targets CSE1L, providing further understanding in the tumorigenesis of gliomas.     

重组腺病毒介导的转录因子Runx3在神经胶质瘤细胞中的表达及其亚细胞定位

目的:制备含有融合Flag标签的Runx3基因的复制缺陷型重组腺病毒,感染神经胶质细胞瘤U251,观察外源Runx3在细胞中的表达及亚细胞定位.方法:用PCR的方法扩增Runx3基因,并将Flag标签蛋白的编码基因与RUNX3基因进行融合,构建腺病毒穿梭载体pShuttle-CMV-Runx3,经Kpn Ⅰ/Xho Ⅰ双酶切鉴定并测序.利用电转化方法将经Pme Ⅰ线性化的pShuttle-CMV-Runx3穿梭载体导入BJ5183重组细菌,获取重组腺病毒质粒Ad-Runx3,再将经Pac Ⅰ线性化的Ad-Runx3重组病毒骨架质粒转染293A包装细胞,包装并扩增病毒.利用该病毒感染神经胶质细胞瘤U251,用免疫印迹法观察外源Runx3在细胞中的表达,用间接免疫荧光法观察其在细胞内的定位.结果:构建并包装表达Runx3蛋白的重组腺病毒,用重组腺病毒感染U251细胞后,经免疫印迹和间接免疫荧光法检测,可见外源导入的Runx3蛋白在细胞核内的特异性定位.结论:成功制备了含有融合Flag标签的转录因子Runx3基因的重组腺病毒,感染U251细胞,在细胞中观察到该分子表达后定位于细胞核中,为研究Runx3在神经胶质瘤发生中的作用奠定了实验基础.     

A key role for EZH2 and associated genes in mouse and human adult T-cell acute leukemia

In this study, we show the high frequency of spontaneous γδ T-cell leukemia (T-ALL) occurrence in mice with biallelic deletion of enhancer of zeste homolog 2 (Ezh2). Tumor cells show little residual H3K27 trimethylation marks compared with controls. EZH2 is a component of the PRC2 Polycomb group protein complex, which is associated with DNA methyltransferases. Using next-generation sequencing, we identify alteration in gene expression levels of EZH2 and acquired mutations in PRC2-associated genes (DNMT3A and JARID2) in human adult T-ALL. Together, these studies document that deregulation of EZH2 and associated genes leads to the development of mouse, and likely human, T-ALL.     

miR-124 and miR-137 inhibit proliferation of glioblastoma multiforme cells and induce differentiation of brain tumor stem cells

Background

Glioblastoma multiforme (GBM) is an invariably fatal central nervous system tumor despite treatment with surgery, radiation, and chemotherapy. Further insights into the molecular and cellular mechanisms that drive GBM formation are required to improve patient outcome. MicroRNAs are emerging as important regulators of cellular differentiation and proliferation, and have been implicated in the etiology of a variety of cancers, yet the role of microRNAs in GBM remains poorly understood. In this study, we investigated the role of microRNAs in regulating the differentiation and proliferation of neural stem cells and glioblastoma-multiforme tumor cells.

Methods

We used quantitative RT-PCR to assess microRNA expression in high-grade astrocytomas and adult mouse neural stem cells. To assess the function of candidate microRNAs in high-grade astrocytomas, we transfected miR mimics to cultured-mouse neural stem cells, -mouse oligodendroglioma-derived stem cells, -human glioblastoma multiforme-derived stem cells and -glioblastoma multiforme cell lines. Cellular differentiation was assessed by immunostaining, and cellular proliferation was determined using fluorescence-activated cell sorting.

Results

Our studies revealed that expression levels of microRNA-124 and microRNA-137 were significantly decreased in anaplastic astrocytomas (World Health Organization grade III) and glioblastoma multiforme (World Health Organization grade IV) relative to non-neoplastic brain tissue (P < 0.01), and were increased 8- to 20-fold during differentiation of cultured mouse neural stem cells following growth factor withdrawal. Expression of microRNA-137 was increased 3- to 12-fold in glioblastoma multiforme cell lines U87 and U251 following inhibition of DNA methylation with 5-aza-2'-deoxycytidine (5-aza-dC). Transfection of microRNA-124 or microRNA-137 induced morphological changes and marker expressions consistent with neuronal differentiation in mouse neural stem cells, mouse oligodendroglioma-derived stem cells derived from S100β-v-erbB tumors and cluster of differentiation 133+ human glioblastoma multiforme-derived stem cells (SF6969). Transfection of microRNA-124 or microRNA-137 also induced G1 cell cycle arrest in U251 and SF6969 glioblastoma multiforme cells, which was associated with decreased expression of cyclin-dependent kinase 6 and phosphorylated retinoblastoma (pSer 807/811) proteins.

Conclusion

microRNA-124 and microRNA-137 induce differentiation of adult mouse neural stem cells, mouse oligodendroglioma-derived stem cells and human glioblastoma multiforme-derived stem cells and induce glioblastoma multiforme cell cycle arrest. These results suggest that targeted delivery of microRNA-124 and/or microRNA-137 to glioblastoma multiforme tumor cells may be therapeutically efficacious for the treatment of this disease.     

Snail plays an oncogenic role in glioblastoma by promoting epithelial mesenchymal transition

Background: The factors affecting glioblastoma progression are of great clinical importance since dismal outcomes have been observed for glioblastoma patients. The Snail gene is known to coordinate the regulation of tumor progression in diverse tumors through induction of epithelial mesenchymal transition (EMT); however, its role in glioblastoma is still uncertain. Therefore, we aimed to further define its role in vitro. Methods and results: The small interfering RNA (siRNA) technique was employed to knock down Snail expression in three glioblastoma cell lines (KNS42, U87, and U373). Specific inhibition of Snail expression increased E-cadherin expression but decreased vimentin expression in all cell lines. In addition, inhibition of the expression of Snail significantly reduced the proliferation, viability, invasion, and migration of glioblastoma cells as well as increased the number of cells in the G1 phase. Conclusions: Knockdown of Snail suppresses the proliferation, viability, migration, and invasion of cells as well as inhibits cell cycle progression by promoting EMT induction. The findings suggest that expression of this gene facilitates glioblastoma progression. Therefore, these results indicate the clinical significance of Snail for use as a potential therapeutic target for glioblastoma.