抑制组蛋白去乙酰化酶与DNA甲基转移酶活性对胶质瘤恶性表型的影响

目的:探讨阻断组蛋白去乙酰化酶与DNA甲基转移酶的活性后对胶质瘤恶性表型的抑制作用.方法:选择丙戊酸(VPA)为组蛋白去乙酰化酶抑制剂,5-氮杂-2'-脱氧胞苷(Aza)为DNA甲基转移酶抑制剂.将U251胶质瘤细胞分为对照组、VPA治疗组、Aza治疗组和VPA+Aza联合治疗组.采用四唑盐(MTT)比色法分析肿瘤细胞增殖活性,流式细胞术分析细胞周期,Annexin V-FITC染色检测细胞凋亡,2D Matrigel、3D Matrigel、Transwell法检测胶质瘤细胞侵袭能力,并建立U251细胞裸鼠皮下移植瘤模型,进行肿瘤局部多点注射上述药物治疗,治疗24 d,每4天测量肿瘤体积.结果:与对照组比较,在治疗2d后各治疗组肿瘤细胞的增殖均出现明显抑制,S期和G2/M期细胞比例减少,诱导细胞周期阻滞于G0/G1期,治疗组细胞凋亡率明显下降,侵袭和运动迁移能力均明显下降,各治疗组鼠移植瘤体积增长较对照组明显减缓,与对照组相比差异均有统计学意义(P＜0.05).以上结果均以VPA+Aza联合治疗组最为显著.结论:联合阻断DNA甲基转移酶和组蛋白去乙酰化酶活性可抑制胶质瘤表观遗传学特征,抑制胶质瘤恶性表型.     

丙戊酸对人脑胶质母细胞瘤细胞株抑制增殖及诱导凋亡作用研究

目的研究丙戊酸(2-propylpentanoic acid,VPA)体外对人脑胶质母细胞瘤细胞株增殖抑制、诱导细胞周期阻滞及促进凋亡的作用,为临床治疗提供理论依据。方法 MTT比色法检测VPA对胶质母细胞瘤细胞株的杀伤作用;流式细胞术检测其对细胞周期及凋亡的影响作用;Western blot法检测乙酰化组蛋白H3(acetyl-Histone H3)、乙酰化组蛋白H4(acetyl-histone H4)表达量变化情况。结果 VPA对胶质瘤母细胞瘤细胞株SF295、U87具有抑制增殖作用,诱导细胞周期阻滞于G2/M期,乙酰化组蛋白H3、H4表达量呈时间依赖性增加。大剂量可以诱导出现凋亡。结论 VPA能够在体外抑制胶质瘤细胞生长,诱导细胞周期阻滞及促进细胞凋亡,其机制可能与促进组蛋白乙酰化有关。     

新型组蛋白去乙酰化酶抑制剂致U251细胞周期阻滞、凋亡及其机制的研究

目的探讨新型组蛋白去乙酰化酶抑制剂(HDACi)2,2,3,3-四甲基环丙酰硫脲(TCCT)诱导人脑胶质瘤U251细胞周期阻滞、凋亡及其作用机制。方法以不同药物浓度与U251细胞共同培养48 h后,采用MTT法检测药物作用48 h后肿瘤细胞的增殖。药物作用24 h后,采用RT-PCR检测肿瘤细胞的p21WAF1/CIP1与Cyclin D1 mRNA的表达,Western blot检测HDAC3、HDAC4、Cyclin D1与p21WAF1/CIP1蛋白的表达,PI单染法分析细胞周期,Annexin V-PI双染法检测肿瘤细胞凋亡。结果 TCCT对U251细胞增殖具有明显抑制作用,药物干预48 h时的IC50为(0.461±0.108)mmol·L-1,并呈现剂量依赖性。TCCT药物干预24 h后U251细胞p21WAF1/CIP1mRNA表达上调,Cyclin D1 mRNA下调;组蛋白去乙酰化酶3(HDAC3)和组蛋白去乙酰化酶4(HDAC4)表达下调,Cyc-lin D1蛋白表达弱下调,p21WAF1/CIP1蛋白表达上调;S期细胞比例明显提高(P<0.05);细胞凋亡率明显增高(P<0.01)。结论 TCCT对U251细胞增殖有明显的抑制作用,引起肿瘤细胞S期阻滞和凋亡。其作用机制可能与其下调HDAC3、HDAC4表达,促进组蛋白乙酰化,而影响p21WAF1/CIP1和Cyclin D1的基因、蛋白的表达有关。     

丙戊酸钠逆转组蛋白低乙酰化水平对肝癌细胞侵袭转移的体外实验研究

目的探讨丙戊酸钠(VPA)逆转组蛋白低乙酰化水平对体外培养的人肝癌细胞系SMMC-7721细胞体外侵袭、转移能力的影响及其可能的作用机制。方法流式细胞仪(FCM)分析不同浓度VPA对SMMC-7721细胞凋亡及细胞周期的影响;分别采用划痕试验,Transwell侵袭小室和细胞-基质黏附试验测定细胞体外迁移、侵袭和黏附能力;Western blot观察不同浓度VPA处理后HPA和PCNA蛋白的表达变化。结果 VPA诱导SMMC-7721细胞凋亡,阻滞细胞于G2/M期,抑制细胞增殖。VPA试验组细胞的侵袭、迁移能力以及黏附能力均显著低于对照组(P<0.05)。随浓度和时间增加,VPA能明显降低HPA和PCNA蛋白表达。结论 VPA可通过逆转染色体组蛋白低乙酰化水平,显著抑制肝癌细胞增殖,降低肝癌细胞侵袭、迁移和黏附能力。下调HPA和PCNA表达可能是其发挥作用的主要机制之一。     

Effect of reversing low-level histone acetylation with VPA on metastasis of hepatocellular carcinoma in vitro

目的 探讨丙戊酸钠(VPA) 逆转组蛋白低乙酰化水平对体外培养的人肝癌细胞系SMMC-7721细胞体外侵袭、转移能力的影响及其可能的作用机制.方法 流式细胞仪(FCM)分析不同浓度VPA对SMMC-7721细胞凋亡及细胞周期的影响;分别采用划痕试验,Transwell侵袭小室和细胞-基质黏附试验测定细胞体外迁移、侵袭和黏附能力;Western blot观察不同浓度VPA处理后HPA和PCNA蛋白的表达变化.结果 VPA诱导SMMC-7721细胞凋亡,阻滞细胞于G2/M期,抑制细胞增殖.VPA试验组细胞的侵袭、迁移能力以及黏附能力均显著低于对照组(P<0.05).随浓度和时间增加,VPA能明显降低HPA和PCNA蛋白表达.结论 VPA可通过逆转染色体组蛋白低乙酰化水平,显著抑制肝癌细胞增殖,降低肝癌细胞侵袭、迁移和黏附能力.下调HPA和PCNA表达可能是其发挥作用的主要机制之一.     

组蛋白去乙酰化酶抑制剂抗肿瘤作用研究进展

组蛋白去乙酰化酶(histone deacetylase, HDAC)在肿瘤发生和发展的多个环节中扮演着非常重要的角色,如肿瘤抑癌基因沉默、细胞分化、血管生成、细胞迁移、细胞周期异常、信号传导及细胞附着等。组蛋白去乙酰化酶抑制剂(histone deacetylase inhibitors, HDACIs)可以靶向组蛋白去乙酰化酶调控组蛋白的乙酰化,进而调控关键的抑制肿瘤蛋白和原癌基因,是极具潜力的抗肿瘤药物。HDACIs已经在血液/淋巴系统肿瘤治疗方面取得了一定成果,目前已经有2种HDACIs：SAHA(suberoylanilide hydroxamic acid)和FK228被批准用于治疗皮肤T细胞淋巴癌,当前大量的临床试验正在挖掘HDACIs在实体瘤治疗方面的潜力。尽管目前基于细胞的研究发现HDACIs可以诱导肿瘤细胞凋亡,细胞周期抑制,细胞分化,抑制血管生成和自噬等,但HDACIs发挥抗肿瘤活性的分子机制仍未阐明,其对实体瘤的临床治疗效果及相关治疗策略有待进一步确证。     

组蛋白去乙酰化酶抑制剂抗血管新生机制的体内研究

目的 探讨组蛋白去乙酰化酶(HDAC)抑制剂对白血病细胞移植瘤血管新生的影响及其机制.方法 12只裸鼠均分为对照组和丙戊酸钠(VPA)用药组.建立Kasumi-1细胞裸鼠移植瘤模型,应用HDAC抑制剂VPA体内用药.RT-PCR和免疫组化检测血管内皮生长因子(VEGF)及其受体(VEGFR) mRNA或蛋白的表达;染色质免疫共沉淀法检测VEGF基因启动子区域染色质内组蛋白H3乙酰化程度的变化.结果 与对照组比较,VPA用药组VEGF及VEGFR2 mRNA和蛋白表达水平明显减少,启动子区域染色质内组蛋白H3的乙酰化程度明显升高.结论 VPA作为HDAC抑制剂,通过提高组蛋白的乙酰化程度,进而抑制血管新生相关因子及受体的表达,阻碍白血病的血管新生.     

基于蛋白质组学的组蛋白表观遗传酶抑制剂研究进展

组蛋白作为真核生物体细胞染色质上核小体的重要组成部分,其上发生的如乙酰化和甲基化等能够调控表观遗传的翻译后修饰,在肿瘤疾病发生、发展的过程中发挥了重要的作用。与此同时,靶向干预甲基转移酶和去乙酰化酶的药物开发,为肿瘤疾病提供了新的治疗策略。基于生物质谱技术的蛋白质组学,可解析疾病进展过程中药物作用下组蛋白修饰的全景变化,进而为揭示药物作用及其耐药机制,研究新型药物联用策略提供重要支持。本文重点介绍了包括甲基转移酶抑制剂和去乙酰化酶抑制剂在内的多种组蛋白修饰酶抑制剂的蛋白质组学研究进展和现状,有助于了解蛋白质组学在组蛋白表观遗传酶抑制剂方面的最新研究,为蛋白质组学在更多表观遗传酶及其特异性抑制剂的研究中提供新线索。     

DAPT抑制人胶质瘤细胞增殖的体内外实验研究

目的研究Notch信号通路抑制剂DAPT对人胶质瘤细胞增殖的影响。方法应用不同剂量DAPT处理胶质瘤细胞系U251,噻唑蓝（MTT）比色试验检测细胞增殖,流式细胞仪检测细胞周期,建立人胶质瘤裸鼠模型,观察肿瘤生长情况。结果DAPT呈剂量依赖性抑制U251细胞增殖,在浓度为0．25μmol／L时即有抑制作用,浓度为5．00μmol／L抑制效果更明显;随DAPT浓度增大G0／G1期细胞比率明显增多（P〈0．01）,而S期细胞比率明显减少（P〈0．01）,使细胞周期阻滞于G0／G1期;用药6周后DAPT处理组裸鼠皮下肿瘤体积明显缩小,平均瘤重对照组为（2．23±0．54）g,DAPT组为（0．97±0．29）g（P〈0．01）,抑瘤率为56．50％。结论DAPT通过阻断Notch信号通路,在体内外有效地抑制人胶质瘤细胞的增殖,提示抑制Notch信号通路的活性可能对胶质瘤的治疗起到一定的作用。     

在治疗肿瘤领域中组蛋白去乙酰化酶抑制剂的研究进展

近年来在治疗肿瘤领域中组蛋白去乙酰化酶（HDAC）抑制剂的研究已成为热点。组蛋白乙酰化转移酶（HAT）与组蛋白去乙酰化酶（HDAC）之间保持的动态平衡调控着有序的基因表达, HDAC表达过度造成乙酰化的失衡会形成肿瘤,而HDAC抑制剂可诱导肿瘤细胞分化、细胞周期停滞和凋亡,抑制肿瘤的生成。HDAC抑制剂是很有前途的新型癌症靶向治疗药物。本文将重点阐述HDAC抑制剂的作用机制以及在肿瘤治疗领域中的研究进展。     

应用丙戊酸钠调节组蛋白乙酰化修饰抑制肝癌细胞增殖的作用及机制

目的观察应用组蛋白脱乙酰酶抑制剂丙戊酸钠调节染色体组蛋白低乙酰化水平对肝癌细胞增殖的作用，并进一步检测Cyctin A、Cyclin D1、Cyclin E、P21^Waf/cip1蛋白及mRNA表达变化，探讨其分子作用机制。方法应用0．75～4．0mmol／L丙戊酸钠作用于肝癌细胞系HepG2细胞后，MTT法检测细胞生长抑制、细胞克隆形成试验观察克隆形成率、碘化丙啶标记流式细胞术检测细胞周期、间接免疫荧光法分析Cyclin A、Cyclin D1、Cyclin E、P21^Waf/cip1蛋白表达，RT—PCR检测分析Cyclin A、Cyclin D1、Cyclin E、P21^Waf/cip1 mRNA表达。结果0．75～4．0mmol／L丙戊酸钠作用24、48、72、96h，观察组出现了时间-剂量依赖趋势的生长抑制，同时细胞克隆形成率显著降低，对照组细胞增殖周期G1、S、M期所占比例未见明显改变，而观察组则随药物浓度、作用时间的不同而出现不同程度的细胞增殖周期G1期阻滞，G1期比例由55．4％～82．8％不等，差异有统计学意义（P〈0．01）。观察组Cyclin A、Cyclin D1蛋白及mRNA表达均被明显下调而P21^Waf/cip1蛋白、mRNA表达则被明显上调，与对照组比较差异均有统计学意义（均P〈0．01）；而Cyclin E蛋白和mRNA表达变化则未见明显差异（P〉0．05）。结论通过应用特异性组蛋白脱乙酰酶抑制剂调节组蛋白乙酰化修饰可明显抑制肝癌细胞生长、抑制细胞克隆形成、阻滞细胞增殖周期于G1期；丙戊酸钠作为组蛋白脱乙酰酶抑制剂可明显抑制肝癌细胞增殖，其作用机制是通过上调P21^Waf/cip1 mRNA蛋白表达，下调Cyclin D1、Cyclin A mRNA蛋白表达分别和／或协同实现。     

Chromatin modifying agents - the cutting edge of anticancer therapy

Chromatin modifying compounds are emerging as the next generation of anticancer therapies. By altering gene expression they could be able to correct uncontrolled proliferation and, in certain cases, aberrant apoptotic pathways, which are hallmarks of malignant cells. The modulation of gene expression is regulated via chromatin remodelling processes that include DNA methylation and chromatin modifications. The identification of aberrant methylation of genes and dysregulated histone acetylation status in cancer cells provides a basis for novel epigenetic therapies. Currently available chromatin modifying agents, a group that includes DNA methyltransferase and histone deacetylase inhibitors, exert anticancer effects by reactivating tumour suppressor genes, inhibiting proliferation and inducing apoptosis. It is anticipated that massive parallel sequencing will identify new epigenetic targets for drug development.     

胶质瘤表观遗传学治疗的研究进展

表观遗传修饰改变与胶质瘤的发生、发展有密切关系,DNA甲基化、组蛋白修饰和非编码RNA等多种表观遗传修饰的异常改变是胶质瘤发生、发展的根本驱动因素。由于表观遗传学变化是可逆的,参与表观遗传修饰的基因和蛋白质已成为胶质瘤治疗中的新靶点,因此,靶向表观遗传调控因子的小分子抑制剂在胶质瘤的治疗中具有广泛的应用前景。综述靶向表观遗传调控因子的小分子抑制剂在胶质瘤治疗中的研究进展,以期为相关研究提供参考。     

The effects of selected inhibitors of histone modifying enzyme on C6 glioma cells

BackgroundAberrant epigenetic histone modifications are implicated in cancer pathobiology, therefore histone modifying enzymes are emerging targets for anti-cancer therapy. There is a few evidence for deregulation of the histone modifying enzymes in glioblastomas. Glioma treatment is a clinical challenge due to its resistance to current therapies.MethodsThe effect of selected inhibitors on epigenetic modifications and viability of glioma C6 cells were studied using immunofluorescence and MTT metabolism test.ResultsWe found that VPA and TSA increase histone H4 acetylation in glioma cells, while chaetocin and BIX01294 at low concentrations reduce H3K9me3, and 3DZNep decreases H3K27me3. Long-term treatment with some epigenetic inhibitors affects viability of glioma cells.ConclusionsWe established the concentrations of selected inhibitors which in C6 glioma cells inhibit the enzyme activity, but do not decrease cell viability, hence allow to study the role of histone modifications in C6 glioma biology.     

Valproic acid inhibits angiogenesis in vitro and in vivo

Valproic acid (VPA) is a widely used antiepileptic agent that is undergoing clinical evaluation for anticancer therapy. We assessed the effects of VPA on angiogenesis in vitro and in vivo. In human umbilical vein endothelial cells, therapeutically relevant concentrations of VPA (0.25 to 1 mM) inhibited proliferation, migration, and tube formation. VPA 1 mM inhibited endothelial cell proliferation by 51 +/- 5%, migration by 86 +/- 11%, and tube formation by 82 +/- 3%. These changes were preceded by the hyperacetylation of histone H4, indicating the inhibition of histone deacetylase (HDAC), and a decreased expression of the endothelial nitric-oxide synthase (eNOS). The inhibition of endothelial cell tube formation by VPA was prevented by addition of the nitric oxide donor (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA NONOate). The anticonvulsive active VPA derivative 2-ethyl-4-methylpentanoic acid, which does not inhibit HDAC, did not affect endothelial cell proliferation, tube formation, or eNOS expression. VPA was also found to inhibit angiogenesis in vivo in the chicken chorioallantoic membrane assay and in a Matrigel plug assay in mice. Embryos from VPA-treated mice showed disturbed vessel formation. These results indicate that therapeutic plasma levels of VPA inhibit angiogenesis by a mechanism involving a decrease in eNOS expression preceded by HDAC inhibition.     

Epigenetic modifications in valproic acid-induced teratogenesis

Exposure to the anticonvulsant drug valproic acid (VPA) in utero is associated with a 1-2% increase in neural tube defects (NTDs), however the molecular mechanisms by which VPA induces teratogenesis are unknown. Previous studies demonstrated that VPA, a direct inhibitor of histone deacetylase, can induce histone hyperacetylation and other epigenetic changes such as histone methylation and DNA demethylation. The objective of this study was to determine if maternal exposure to VPA in mice has the ability to cause these epigenetic alterations in the embryo and thus contribute to its mechanism of teratogenesis. Pregnant CD-1 mice (GD 9.0) were administered a teratogenic dose of VPA (400 mg/kg, s.c.) and embryos extracted 1, 3, 6, and 24 h after injection. To assess embryonic histone acetylation and histone methylation, Western blotting was performed on whole embryo homogenates, as well as immunohistochemical staining on embryonic sections. To measure DNA methylation changes, the cytosine extension assay was performed. Results demonstrated that a significant increase in histone acetylation that peaked 3 h after VPA exposure was accompanied by an increase in histone methylation at histone H3 lysine 4 (H3K4) and a decrease in histone methylation at histone H3 lysine 9 (H3K9). Immunohistochemical staining revealed increased histone acetylation in the neuroepithelium, heart, and somites. A decrease in methylated histone H3K9 staining was observed in the neuroepithelium and somites, METHYLATED histone H3K4 staining was observed in the neuroepithelium. No significant differences in global or CpG island DNA methylation were observed in embryo homogenates. These results support the possibility that epigenetic modifications caused by VPA during early mouse organogenesis results in congenital malformations.     

Grape seed proanthocyanidins reactivate silenced tumor suppressor genes in human skin cancer cells by targeting epigenetic regulators

Grape seed proanthocyanidins (GSPs) have been shown to have anti-skin carcinogenic effects in in vitro and in vivo models. However, the precise epigenetic molecular mechanisms remain unexplored. This study was designed to investigate whether GSPs reactivate silenced tumor suppressor genes following epigenetic modifications in skin cancer cells. For this purpose, A431 and SCC13 human squamous cell carcinoma cell lines were used as in vitro models. The effects of GSPs on DNA methylation, histone modifications and tumor suppressor gene expressions were studied in these cell lines using enzyme activity assays, western blotting, dot-blot analysis and real-time polymerase chain reaction (RT-PCR). We found that treatment of A431 and SCC13 cells with GSPs decreased the levels of: (i) global DNA methylation, (ii) 5-methylcytosine, (iii) DNA methyltransferase (DNMT) activity and (iv) messenger RNA (mRNA) and protein levels of DNMT1, DNMT3a and DNMT3b in these cells. Similar effects were noted when these cancer cells were treated identically with 5-aza-2′-deoxycytidine, an inhibitor of DNA methylation. GSPs decreased histone deacetylase activity, increased levels of acetylated lysines 9 and 14 on histone H3 (H3-Lys 9 and 14) and acetylated lysines 5, 12 and 16 on histone H4, and reduced the levels of methylated H3-Lys 9. Further, GSP treatment resulted in re-expression of the mRNA and proteins of silenced tumor suppressor genes, RASSF1A, p16^INK4a and Cip1/p21. Together, this study provides a new insight into the epigenetic mechanisms of GSPs and may have significant implications for epigenetic therapy in the treatment/prevention of skin cancers in humans.     

Apoptotic effect in the glioma cells induced by specific protein extracted from Okinawa Habu (Trimeresurus flavoviridis) venom in relation to oxidative stress.

Okinawa Habu (Trimeresurus flavoviridis) venom is well known for its toxic efficacy, from which one kind of specific protein, Okinawa Habu apoxin protein-1 (OHAP-1) has been extracted. The purpose of this study was to investigate whether OHAP-1 could induce apoptosis in some glioma cells, and if so, to elucidate the possible mechanism involved. Three malignant glioma cell lines were tested. The malignant glioma cell lines were rat C6 and human RBR 17T, U251. OHAP-1 inhibited growth of all cell lines. Whether or not the apoptosis had been induced was determined by using DNA gel electrophoresis, DNA flow cytometry and TUNEL assay. After OHAP-1 treatment, DNA fragmentation, an increase in the percentage of subdiploid DNA content, and TUNEL positive cells were found in the C6, RBR17T, and U251 cells. Furthermore, OHAP-1 showed L-amino acid oxidase (LAAO) activity. In order to study the mechanism of apoptosis induced by OHAP-1, the changes of intracellular reactive oxygen species (ROS) were measured using flow cytometry, and the expression of p53 protein was examined using immunohistochemistry. OHAP-1 was found to generate ROS and increase the expression of p53 protein in glioma cells. The inhibiting effect of OHAP-1 on three tested cells was reversed when an antioxidant of either catalase or reduced glutathione (GSH) was added; its apoptotic effect correspondingly became weaker. In this study, the apoptotic effect of OHAP-1 on some malignant glioma cells was confirmed, and it could be that this effect might be mediated through promoting the generation of intracellular ROS and p53 protein expression in glioma cells. It was suggested that OHAP-1 is promising as a potential candidate for clinical tumor therapy.