DNA甲基转移酶DNMT1在子宫内膜癌中的表达

抑癌基因启动子区CpG岛甲基化与基因失活有关是诸多恶性肿瘤发生过程中的重要分子事件而有研究表明肿瘤组织中DNA甲基转移酶活性及表达量的异常导致此过 甲基化现象。在子宫内膜癌中国内外专家亦发现抑癌基因启动子区的CpG岛过甲基化及基因失活为一频发分子事件。本研究旨在探讨子宫内膜 癌中DNA甲基转移酶的表达状况以揭示子宫内膜癌中诸多抑癌基因甲基化基因调控发生的可能机制为开辟临床治疗子宫内膜癌的新思路提供实验依据。     

三种DNA甲基转移酶在肝细胞癌组织中的表达及其临床意义

目的:探讨肝细胞癌组织中三种甲基转移酶(DNMT)蛋白表达的差异及其临床意义.方法:收集38例肝癌标本,取癌区组织各3块,制作组织芯片,应用免疫组化SP法分析肝癌组织中DNMT蛋白的表达,并分析其与肝癌各临床、病理参数间的关系.结果:在38例肝癌组织中,DNMT1、DNMT3a和DNMT3b蛋白的表达阳性率分别为55.3%、48.5%和65.8%.DNMT蛋白质着色主要分布在细胞核,散在分布于胞浆.DNMT1蛋白质表达与门脉癌栓和肿瘤无包膜等参数显著相关;组织中DNMT1表达与DNMT3b表达具有相关性,二者同时表达与门脉癌栓和肿瘤无包膜等参数显著相关.但三种DNMT蛋白的阳性表达与患者的年龄、性别、肿瘤分化程度和淋巴结转移无显著相关性(P>0.05).结论:肝细胞癌组织中存在三种DNMT蛋白的过表达,DNMT1和DNMT3b的高表达与门脉癌栓和肿瘤无包膜等参数显著相关,二者协同作用可能在肝癌的发生和发展中起重要作用.     

DNA甲基转移酶在妇科肿瘤中的研究进展

大量研究表明，许多种类的肿瘤细胞都有异常的DNA甲基化行为，抑癌基因常常被过量地甲基化而失去活性，而基因的DNA序列并不发生改变。DNA甲基化是由DNA甲基转移酶（DNMT）催化并维持的。DNMT通过调节细胞内甲基化过程而参与肿瘤的发生与发展，在有5′端调控区胞嘧啶．鸟嘌呤（CpG）岛甲基化异常参与的肿瘤细胞中常表现为过度表达，其活性增高是肿瘤细胞具有特征的早期分子改变。     

DNA 甲基转移酶在肿瘤发病机制中的研究进展

DNA甲基化是表观遗传学的主要形式,而DNA甲基转移酶（ DNMTs）是DNA甲基化的主要调节酶,DNA甲基转移酶的激活参与了肿瘤的发生和发展过程,同时伴有肿瘤抑制基因的高甲基化沉默和低表达,是病人预后不良的标志;DNA甲基转移酶3b（ DNMT3b）的多态性及吸烟所致的DNMTs表达的改变是肿瘤发生的危险因素,靶向DNMTs治疗由于其细胞毒性小,是当前研究的一个热点。本文就DNA甲基转移酶在肿瘤发病机制中的作用做一综述。     

DNA甲基转移酶在肿瘤发病机制中的研究进展北大核心CSCD

0引言 与经典的遗传学不同,表观遗传学是指在DNA序列未发生异常改变的前提下,基因的功能发生了叮遗传的信息变化,并最终导致了表型的改变。DNA甲基化是表观遗传学修饰的主要形式之一,而DNA甲基转移酶（DNA methyltransferase,DNMT）则是DNA甲基化的主要调节酶。本文就DNMT在肿瘤中的研究进展作一综述。     

DNA甲基转移酶基因在MDS患者中的表达及其临床意义

研究DNA甲基转移酶（DNA methyltransferase,DNMT）基因在骨髓增生异常综合征（MDS）患者中的表达及其与抑癌基因p15INK4B甲基化状态的相关性,并进一步探讨其与临床预后的关系。方法：采用SYBR Green I实时定量逆转录聚合酶链反应（Real-time RT-PCR）方法对48例初治MDS患者和20例正常人骨髓进行DNMT1、DNMT3A、DNMT3B mRNA水平检测;采用甲基化特异性PCR（MSP-PCR）方法检测48例初治MDS患者和20例正常人p15INK4B基因的甲基化状态。结果：低危组MDS患者3种DNMTs mRNA与正常对照组相比,表达水平差异均无统计学意义（P>0.05）;高危组MDS患者3种DNMTs mRNA表达显著高于低危组和正常对照组（P均<0.01）;MDS患者DNMTs mRNA表达水平与p15INK4B基因甲基化程度呈正相关。12例高危MDS患者接受了地西他滨治疗,另外15例高危MDS患者接受了IA/DA联合化疗,地西他滨组疗效与联合化疗组比较差异无统计学意义（P>0.05）。结论：DNMTs基因的异常高表达,导致细胞周期调控相关的p15INK4B等抑癌基因启动子CpG岛过甲基化失活,在MDS患者由低危向高危转变乃至进展为急性髓系白血病（AML）过程中,起着至关重要的作用,DNMTs mRNA表达水平可以作为一种判断MDS预后的指标。     

DNA甲基转移酶在肿瘤形成中的研究进展

DNA甲基化是基因表达调控中重要的调节方式之一，可通过影响癌基因和抑癌基因的表达以及基因组的稳定性而参与肿瘤形成。DNA甲基化是由DNA甲基转移酶（DNMT）催化发生并维持的，并认为DNMT活性增高是肿瘤细胞具有特征的早期分子改变，因而受到越来越多的学者关注。     

DNA甲基转移酶3B4过表达与肾透明细胞癌的关系

  目的  探究DNA甲基转移酶（DNA methyltransferase,DNMT）在肾透明细胞癌（clear cell renal cell carcinoma,ccRCC）发生发展中的机制。  方法  收集2012年1月至12月15例内蒙古科技大学包头医学院第一附属医院术前均未结予放化疗并行肾癌根治术患者的组织标本,均经病理证实为ccRCC。应用实时定量PCR、蛋白印迹、联合亚硫酸氢钠限制酶分析法和甲基化特异PCR等方法检测ccRCC组织中DNMT的mRNA表达,及ccRCC组织中整体甲基化（global methylation）水平和抑癌基因RASSF1A甲基化和表达水平。  结果  ccRCC组织中DNMT3B4的mRNA表达增加,同时其蛋白含量也相应增加。ccRCC患者癌组织中DNA重复序列Alu的甲基化水平0.106±0.04较癌旁组织中0.115±0.03低,差异具有统计学意义（P < 0.05）。而肿瘤抑制基因RASSF1A启动子区域发生高甲基化,其mRNA和蛋白的表达均降低。  结论  DNMT3B4基因过表达可能与染色体不稳定以及RASSF1A基因低表达有关,在ccRCC的发生发展中可能扮演着重要的角色。      

5-脱氧杂氮胞苷抑制肝癌细胞DNA 甲基转移酶转录

 目的　明确 5- Aza- cd R对 DNA MTase转录水平的抑制作用。方法　用 5× 1 0 -7M的5- AZa- cd R处理肝癌细胞株 SMMC- 772 1和 H2和 Hep G2 ,就用 RT- PCR技术检测经药物处理前后 2株肝癌细胞 DNA MTase m RNA表达水平。结果　经 5- Aza- cd R处理后 ,2株肝癌细胞 DNAMTase m RNA表达量显著下降。结论　 5- Aza- cd R能抑制肝细胞 DNA MTase转录 ,是其抗肿瘤作用的重要机制之一.     

基于TALE技术的哈萨克族食管上皮DNA甲基转移酶1高表达细胞株模型的构建

目的：构建哈萨克族食管上皮细胞DNA甲基转移酶1（DNMT1）高表达细胞株模型。方法：将构建的WV0133、WV0132和WV072质粒转染至哈萨克族食管上皮细胞,利用嘌呤霉素对DNMT1高表达细胞进行筛选,并通过荧光显微镜、实时荧光定量PCR（qPCR）和Western blot法检测细胞转染情况和目的基因DNMT1的表达情况。结果：WV0133和WV0132质粒转染组细胞DNMT1 mRNA表达水平是正常细胞组的1.786倍和2.721倍,DNMT1蛋白表达水平是正常细胞组的2.734倍和3.100倍,均显著高于正常细胞组（P<0.01）。其中,WV0132质粒转染组细胞DNMT1 mRNA和蛋白表达水平较高。结论：成功构建了哈萨克族食管上皮DNMT1高表达细胞株模型,为深入研究食管癌的发生机制提供了研究工具。     

Aberrant DNA methyltransferase 1 expression in clear cell renal cell carcinoma development and progression

Objective： To better understand the contribution of dysregulated DNA methyltransferase 1 （DNMT1） expression to the progression and biology of clear cell renal cell carcinoma （ccRCC）. Methods： We examined the differences in the expression of DNMT1 in 89 ecRCC and 22 normal tissue samples by immunohistochemistry. In addition, changes in cell viability, apoptosis, colony formation and invading ability of ccRCC cell lines （786-0 and Caki-1） were assessed after transfection with DNMT1 siRNA. Results： We found DNMT1 protein was significantly higher expressed in ccRCC than that of in no-tumor tissues （56.2% and 27.3%, respectively, P=0.018）. The expression of DNMT1 was strongly associated with ccRCC tumor size, tumor pathology stage, histological grading, lymph node metastasis, vascular invasion, recurrence and prognosis. Moreover, knockdown of DNMT1 expression significantly inhibited ccRCC cell viability, induced apoptosis, decreased colony formation and invading ability. Conclusions： Expression of DNMTI protein is increased in ccRCC tissues, and DNMT1 expression is associated with poor prognosis of patients. Experiments in vitro further showed DNMT1 played an essential role in proliferation and invasion of renal cancer cells. Moreover, targeting this enzyme could be a promising strategy for treating ccRCC, as evidenced by inhibited cell viability, increased apoptosis, decreased colony formation and invading ability.     

DNA methyltransferase expression and DNA hypermethylation in human hepatocellular carcinoma

Aberrant DNA methylation and increased expression of DNA methyltransferases (DNMTs) are features of tumor cells. To investigate roles for DNMTs during hepatocarcinogenesis, we examined DNMT expression at both the mRNA and protein level in hepatocellular carcinomas (HCCs) and paired non-neoplastic liver tissues, along with measuring the DNA methylation status of five tumor suppressor genes. Expression of DNMT1, DNMT3a and DNMT3b mRNA was detected in 33.3, 59.3, and 55.6% of HCCs and 40.7, 22.2, and 0% of non-neoplastic liver tissues, respectively. DNMT1 and DNMT3a were immunoreactive in 100 and 48% of HCCs and 52 and 0% of non-neoplastic liver tissues. The DNMT3a mRNA expression profile showed significant correlation with its immunoreactivity (P=0.022). DNA methylation status of five tumor suppressor genes, HIC-1, p16, RASSF1A, p53, and RB1 was detected in 85.2, 48.1, 44.4, 22.2, and 0% of HCCs, respectively. There was no significant correlation between DNMT mRNA expression and DNA methylation (P>0.05). DNMT immunoreactivity was also not associated with DNA methylation except HIC-1 (P=0.036) and p53 methylation (P=0.009). Despite the lack of correlation between DNA methylation status and DNMT expression, the frequency of hypermethylation of tumor suppressor genes remained relatively high in HCCs, suggesting that regional DNA hypermethylation is involved in hepatocarcinogenesis and that there may be other mechanisms for increasing DNA methylation.     

Association of the SUV39H1 histone methyltransferase with the DNA methyltransferase 1 at mRNA expression level in primary colorectal cancer

This study was aimed at investigating the involvement of the SUV39H1 histone methyltransferase on the epigenetic change of euchromatic promoter in colorectal cancer. We retrospectively analyzed the mRNA levels of SUV39H1 and the promoter methylation of the p14(ARF), p16(INK4a) and HLTF genes as well as the mRNA levels of DNA methyltransferase 1 (DNMT1) in fresh frozen tissues from 219 colorectal cancer patients. The mRNA levels of the SUV39H1 and DNMT1 were assessed via quantitative real-time PCR and the methylation profiles of the CpG islands were determined using methylation-specific PCR. The mRNA levels of SUV39H1 and DNMT1 were elevated in 25% and 42% of 219 colorectal cancers, respectively. The hypermethylation of the p14(ARF), p16(INK4a) and HLTF genes occurred in 36%, 51% and 34% of the patients. The elevated mRNA levels of SUV39H1 were not associated with the hypermethylation of the 3 genes. However, the mRNA levels of DNMT1 were significantly different between patients with elevated mRNA levels of SUV39H1 and those without (1.62 +/- 0.84, 0.91 +/- 0.81, respectively; p = 0.007). Patients with elevated mRNA levels of SUV39H1 showed a higher prevalence of DNMT1 elevation than those without (61 vs. 35%, p = 0.0008). Patients with an elevated mRNA level of SUV39H1 had a 2.71 (95% CI = 1.09-4.48, p = 0.002) times greater risk of an elevated mRNA level of DNMT1, after controlling for age and gender. In conclusion, the present study suggests that SUV39H1 is significantly associated with DNMT1, but not with euchromatic promoter methylation in colorectal cancer.     

CO2对宫颈癌Hela细胞CDK9基因表达的影响

目的研究C02对宫颈癌Hela细胞株CDK9基因表达的影响,分析其在癌细胞生长与转移中的作用。方法将宫颈癌Hela细胞株随机分为3组：A组Hela细胞株在压力为8mmHg的纯C02下通气4h,培养24h;B组Hela细胞株在压力为8mmHg的纯C02下通气4h,培养120h;C组Hela细胞株未进行C02处理,细胞株置于常规细胞培养箱中培养120h。采用RT-PCR法检测A、B、C组宫颈癌Hela细胞CDK9mRNA的表达。结果A、B组与C组比较,A、B组CDK9mRNA的相对表达量明显下调（P〈0．05）;B组与A组比较,B组CDK9mRNA的相对表达量比A组下调更显著（P〈0．01）。结论宫颈癌Hela细胞CDK9基因在C02作用下受抑制出现表达下调,且随C02作用时间越长,CDK9基因相对表达量降低越明显。     

Decrease of DNA methyltransferase 1 expression relative to cell proliferation in transitional cell carcinoma

In many common cancers such as transitional cell carcinoma (TCC), specific genes are hypermethylated, whereas overall DNA methylation is diminished. Genome-wide DNA hypomethylation mostly affects repetitive sequences such as LINE-1 retrotransposons. Methylation of these sequences depends on adequate expression of DNA methyltransferase I (DNMT1) during DNA replication. Therefore, DNMT1 expression relative to proliferation was investigated in TCC cell lines and tissue as well as in renal carcinoma (RCC) cell lines, which also display hypomethylation, as indicated by decreased LINE-1 methylation. Cultured normal uroepithelial cells or normal bladder tissue served as controls. In all tumor cell lines, DNMT1 mRNA as well as protein was decreased relative to the DNA replication factor PCNA, and DNA hypomethylation was present. However, the extents of hypomethylation and DNMT1 downregulation did not correlate. Reporter gene assays showed that the differences in DNMT1 expression between normal and tumor cells were not established at the level of DNMT1 promoter regulation. Diminished DNMT1:PCNA mRNA ratios were also found in 28/45 TCC tissues but did not correlate with the extent of DNA hypomethylation. In addition, expression of the presumed de novo methyltransferases DNMT3A and DNMT3B mRNAs was investigated. DNMT3B overexpression was observed in about half of all high-stage TCC (DNMT3B vs. tumor stage, chi(2): p = 0.03), whereas overexpression of DNMT3A was rarer and less pronounced. Expression of DNMT3A and DNMT3B in most RCC lines was higher than in TCC lines. Our data indicate that DNMT1 expression does not increase adequately with cell proliferation in bladder cancer. This relative downregulation probably contributes to hypomethylation of repetitive DNA but does not determine its extent alone.     

直肠癌患者组蛋白甲基转移酶hSETD1A表达水平的临床预后价值

背景与目的:组蛋白修饰是非常重要的表观遗传修饰形式,组蛋白甲基化修饰酶基因的异常表达与多种疾病及癌症的发生、发展有关。探讨直肠癌患者肿瘤组织的组蛋白甲基转移酶hSETD1A表达水平与临床预后的相关性。方法:选取2012年1月-2014年6月福建省肿瘤医院有详细临床资料和预后随访信息的直肠癌患者肿瘤组织切除标本141例及癌旁组织标本50例。采用免疫组织化学法检测h SETD1A的表达情况,分析其与直肠癌临床病理学特征(年龄、性别、肿瘤大小、T分期、淋巴结转移、神经累及等参数)及预后的关系。结果:肿瘤组织中h SETD1A的阳性表达率明显高于癌旁组织(75.2%vs26.0%,P<0.001)。此外,其阳性率的高低还与患者性别及肿瘤分化程度的不同相关(P=0.009)。而与年龄、肿瘤大小、T分期、淋巴结转移、TNM分期、神经累及、脉管癌栓、血清癌胚抗原(carcinoembryonic antigen,CEA)及CA19-9水平无关。生存分析结果显示,h SETD1A阳性组的5年生存率明显低于h SETD1A阴性组(64.4%vs 76.5%,P=0.036)。多因素COX回归分析显示,h SETD1A表达和T分期、淋巴结转移状况(N分期)是直肠癌的独立预后因素。结论:肿瘤组织hSETD1A的表达水平与直肠癌患者的预后密切相关。     

Targeting DNA methyltransferase in cancer

DNA methyltransferase is an enzyme responsible for generating and maintaining DNA methylation patterns. DNA methylation patterns control different genome functions, thus they are an important component of the epigenetic information. It has been recently postulated that DNA methyltransferase plays an important role in oncogenesis and that it is a candidate target for anticancer therapy. This commentary discusses the possible mechanisms through which DNA methyltransferase participates in oncogenesis and the rationale for targeting it in cancer.