巢式MSP法检测恶性血液病细胞株p16基因启动子甲基化状态的研究

本研究应用改进的甲基化特异性PCR（MSP）法，即巢式甲基化特异性PCR法检测6种肿瘤细胞株p16基因启动子的甲基化状态效率，探讨其在筛选p16基因启动子高甲基化的肿瘤细胞株，及将其作为研究基因甲基化与表达关系的理想细胞模型中的应用。6种肿瘤细胞株基因组DNA经碱变性后以亚硫酸盐修饰，再用巢式甲基化特异性聚合酶链反应扩增，分析检测其p16启动子区CpG岛的甲基化状态。结果表明：CA46、U266都有不同程度的p16基因启动子区甲基化，而Molt4、K562、HL-60、Jurkat的p16基因启动子区均未甲基化。结论：用巢式甲基化特异性PCR可以准确的检测出恶性血液病细胞株p16基因的甲基化状态，方法简单，灵敏且重复性强，可以广泛用于筛选各种p16基因启动子区甲基化的恶性血液病细胞株以及恶性血液病诊断。     

错配杂交化学发光法定量检测p16基因过甲基化

目的建立一种基于错配杂交化学发光检测p16基因启动子区过甲基化的定量分析方法。方法用亚硫酸氢钠修饰基因组DNA,所有未甲基化的胞嘧啶都被转变为尿嘧啶,而甲基化的胞嘧啶则不发生变化。设计合成1对不含CpG位点的引物,同时扩增甲基化或非甲基化目的DNA片段,用2条分别与甲基化及非甲基化CpG位点互补的寡核苷酸探针与扩增产物进行杂交及化学发光检测,通过探针杂交信号强度比确定样品DNA中甲基化的p16基因的比例。结果错配杂交化学发光法具有较好的精密度(CV=5·2%~6·4%)和灵敏度(2·5×10-4pmol),检测已知混合样品的p16基因甲基化率分别为0%、23%、52%、70%及93%,与实际结果一致。结论本研究建立的错配杂交化学发光法是一种检测快速、操作简便的p16基因甲基化的定量检测方法。     

多发性骨髓瘤患者p16基因结构改变及启动子区甲基化的研究

目的探讨p16基因结构及启动子区CPG岛甲基化在多发性骨髓瘤(MM)发病中的作用.方法利用PCR-单链构象多态性、甲基化特异性PCR(MSP)技术研究骨髓瘤细胞株U266、LP1、KM3及MM患者p16基因结构改变及启动子区CPG岛甲基化状态.结果KM3细胞株为p16基因外显子2的同源缺失;U266、LP1细胞株及55.56%MM患者的p16基因启动子区存在CPG岛甲基化现象,p16基因甲基化与MM分期无关(P>0.05).结论p16基因甲基化在MM中较为常见,这可能为MM的治疗提供借鉴.     

DNA甲基转移酶在骨髓瘤细胞株中的表达异常及其意义

本研究旨在探索多发性骨髓瘤细胞株U266 DNA甲基转移酶(DNMT)活性、基因表达情况并分析其生物学意义。用ELISA方法检测U266细胞DNMT活性,用半定量RT-PCR技术分析DNMT 1、3a、3b mRNA在U266细胞中的表达,体外用不同浓度去甲基化化合物异硫氰酸苯己酯(phenyl hexyleisothiocyanate,PHI)处理U266细胞,分析DNMT活性变化及DNMT1、3a、3b在瘤细胞中的表达改变。结果表明,骨髓瘤细胞U266中DNMT总活性升高,DNMT1、3a、3b mRNA均高表达,不同浓度PHI处理U266细胞后,细胞增殖抑制,DNMT活性亦被显著抑制,DNMT1、DNMT3a以及DNMT3b mRNA表达下降并呈浓度依赖性。结论:DNMT活性及其表达增高是骨髓瘤细胞特征之一,当DNMT活性或mRNA表达抑制时瘤细胞发生凋亡,因此DNMT可作为骨髓瘤治疗的新靶点。     

多发性骨髓瘤患者骨髓单个核细胞与U266细胞中ICSBP/IRF8基因表达沉默的初步研究

本研究旨在探讨多发性骨髓瘤(MM)细胞株U266和MM患者骨髓单个核细胞(MM-BMMNC)中干扰素调节因子8(ICSBP/IRF8)的表达,及DNA甲基化与ICSBP/IRF8表达沉默的关系。选取U266细胞株及10例MM患者MM-BMMNC,同时提取10例正常人骨髓单个核细胞(N-BMMNC)为对照。用荧光定量PCR测定ICSBP/IRF8的表达(利用2-ΔΔCT进行计算);利用甲基化特异性PCR检测ICSBP/IRF8启动子序列甲基化程度(以目的基因ICSBP/IRF8与内参照β-actin表达量的比值作为结果)。结果发现,与N-BMMNC相比,ICSBP/IRF8在U266细胞和MM-BMMNC中表达低下,且ICSBP/IRF8启动序列CpG岛甲基化程度明显增高,差异均具有统计学意义(P<0.05)。结论:MM-BMMNC和U226细胞中ICSBP/IRF8基因表达沉默,ICSBP/IRF8启动序列CpG岛甲基化程度较正常显著增高,说明DNA甲基化可能造成了ICSBP/IRF8表达沉默。结果初步提示ICSBP/IRF8与MM的发生和发展机制可能有密切联系。     

砷剂诱导多发性骨髓瘤细胞socs-1基因去甲基化作用的研究

本研究探讨三氧化二砷（As2O3）对人多发性骨髓瘤细胞株U266、RPMI8226细胞内socs-基因甲基化状态的影响。用MTT法观察As2O3对骨髓瘤细胞增殖情况的影响，采用甲基特异性PCR法检测As2O3作用前后骨髓瘤细胞株U266、RPMI8226 socs-1基因的甲基化状态，以实时定量PCR技术定量检测细胞株给药前后socs-1基因mRNA的表达变化，流式细胞技术检测As2O3诱导的骨髓瘤细胞的凋亡情况。结果表明：人骨髓瘤细胞株U266、RPMI8226均存在不同程度的socs-1基因CpG岛甲基化，socs-1基因不表达的现象。As2O3作用72小时后socs-1基因甲基化程度明显减弱或消失，socs—1基因在mRNA水平上表达明显增强，与各野生型细胞株相比，差异具有显著性P〈0．05），且细胞生长抑制明显，早期、晚期细胞凋亡比率明显升高，并呈现剂量依赖性。结论：As：03可诱导socs—1基因甲基化状态的改变，使基因表达上调，恢复其活性，这为进一步阐明As2O3诱导骨髓瘤细胞凋亡的可能机制和As2O3治疗多发性骨髓瘤的可能机制提供新的思路和新的研究方向。     

多发性骨髓瘤细胞中胰岛素样生长因子结合蛋白7的基因表达及甲基化调控

目的:研究多发性骨髓瘤细胞株U266中胰岛素样生长因子结合蛋白7(IGFBP7)的表达及甲基转移酶抑制剂5-氮杂-2'-脱氧胞苷(5-aza-dc)对其增殖的影响。方法:体外培养多发性骨髓瘤细胞株U266,并以健康查体者的骨髓单个核细胞(N-BMMNC)作为正常对照,提取RNA,采用实时RT-PCR检测IGFBP7的表达,提取细胞DNA甲基化修饰后采用甲基化特异性PCR(MSP)分析其CpG岛的甲基化状态,不同浓度的甲基转移酶抑制剂5-aza-dc(5、10和20μmol/L)处理U266细胞株,在48 h收集细胞,用实时RT-PCR和蛋白印迹法检测各组IGFBP7 mRNA和蛋白表达,流式细胞术检测药物处理前后各组细胞的细胞凋亡及细胞周期。结果:U266细胞IGFBP7 mRNA表达较正常骨髓细胞降低;MSP检测显示U266 IGFBP7的启动子CpG岛明显甲基化;不同浓度的5-aza-dc处理U266细胞株48 h后,IGFBP7的mRNA表达呈剂量依赖性增高(r=0.952,P0.05),IGFBP7蛋白表达呈剂量依赖性增高(r=0.983,P0.05);随着药物浓度增高,U266在G_0/G_1期细胞逐渐增多(r=0.966),细胞凋亡率逐渐增加(r=0.958)。结论:U266细胞中IGFBP7 mRNA较N-BMMNC低表达,与CpG岛的异常甲基化相关,5-aza-dc可以使U266细胞中IGFBP7mRNA和蛋白表达恢复,并通过阻滞细胞周期和诱导细胞凋亡发挥其对U266细胞的生长抑制作用     

诱导子宫内膜癌细胞DNA错配修复及肿瘤增殖抑制基因启动子CpG岛去甲基化修饰的研究

目的：研究在用5-杂氮-2’脱氧胞苷（5-Aza-CdR）诱导体外培养的人子宫内膜癌细胞株HEC-1-A中,DNA错配修复基因hMLH1、hMSH2及细胞周期调控基因p16启动子CpG岛的去甲基化,及对于该细胞的增殖抑制作用。方法：体外培养人子宫内膜癌细胞株HECq—A;利用MTT比色法检测5-Aza-CdR对于HEG-1-A的增殖抑制的影响;利用流式细胞术（FCM）分析药物处理前后HE（2-1-A的细胞周期;利用重亚硫酸盐处理及甲基化特异性PCR（MS-PCR）检测hMLH1、hMSH2及p16基因启动子cpG岛的甲基化修饰;提取药物处理前后HE（2-1-A细胞的总蛋白,利用Westernblotting检测hMLH1、hMSH2及p16蛋白的表达情况。结果：5-Aza-CdR对于人子宫内膜癌细胞株HED-1-A体外增殖抑制呈明显的剂量依赖性[IG50,为（0．71±0．05）μmol·L1];FCM分析显示HEC-1-A细胞在5Aza-CdR处理前后均呈现明显的细胞周期差异,并且药物组细胞表现为G0／G1期（P〈0．05）阻滞。MS-PCR分析5-Aza-CdR显示著诱导hMLH1、hMSH2基因启动子CpG岛的去甲基化修饰。Westernblotting检测发现IC50剂量的5-AzaCdR处理HEC-1-A细胞前后,hMLH1、hMSH2及p16的表达量为（111．30±3．17）％、（76．99±1．19）％和（97．63±1．28）％明显高于空白对照组（P〈0．05）,提示该药物有提高上述蛋白表达的作用。结论：5-AzaCdR可诱导人子宫内膜癌细胞株HEC-1-A中,hMLH1、hMSH2及p16启动子CpG岛的去甲基化修饰,从而有效抑制该细胞的体外增殖。     

巢式MSP检测砷剂诱导人多发性骨髓瘤U266细胞系p16基因去甲基化及转录

本研究探讨用高灵敏度的DNA甲基化检测方法及DNA克隆测序分析法检测三氧化二砷(As2O3)的去甲基化作用,并对其可能的去甲基化作用机制进行分析。采用巢式甲基特异性PCR法(nested-methylation specificPCR,n-MSP)、DNA克隆测序分析法检测As2O3作用前后U266细胞株p16基因甲基化状态,应用RT-PCR检测p16、DNA甲基转移酶1(DNMT1)、DNMT3A、DNMT3B基因mRNA的表达,以生长曲线、MTT法、集落形成实验检测As2O3对骨髓瘤细胞生长和增殖的抑制作用。利用流式细胞仪DNA含量分析法探讨As2O3对多发性骨髓瘤细胞系U266周期的影响。结果表明:①未处理组U266细胞基因组DNA的胞嘧啶保持不变,而经As2O3作用的U266细胞基因组DNA的胞嘧啶均已变为胸腺嘧啶,这说明U266细胞存在p16基因甲基化,As2O3作用后p16基因异常甲基化的现象被逆转;②未处理组细胞p16基因不表达,As2O3作用72小时后p16基因表达增强,0.5μmol/L组、1.0μmol/组和2.0μmol/组p16基因表达阳性条带灰度值与β-肌动蛋白比值分别为(0.22±0.10)、(0.59±0.11)、(0.68±0.09),阳性对照灰度比值为(0.77±0.13),差异有非常显著的统计学意义(P<0.01);③与未处理组相比,As2O3作用72小时后甲基转移酶(DNMT)1、DNMT3A、DNMT3B的表达下降并呈浓度依赖性;④与对照组相比,3组不同浓度As2O3均能明显抑制骨髓瘤细胞生长,G0-G1期细胞增加。结论:As2O3可能通过抑制甲基转移酶(DNMT1)、DNMT3A、DNMT3B和(或)直接对p16基因去甲基化,使p16基因表达上调,恢复其活性,从而实现其对细胞周期的调控功能,将细胞阻滞于G0-G1期,抑制骨髓瘤细胞的增长。     

表没食子儿茶素没食子酸酯对人急性单核细胞白血病细胞株U937的作用及机制研究

本研究探讨表没食子儿茶素没食子酸酯(EGCG)对人急性单核细胞白血病细胞株U937的作用。采用磺酰罗丹明B(SRB)法检测EGCG对U937细胞增殖的影响;采用流式细胞术检测EGCG对U937细胞周期的影响;采用RT-PCR、Westren blot法分别检测p16mRNA、蛋白的表达;采用nMSP法检测U937细胞p16甲基化状态变化;采用RT-PCR法检测DNA甲基转移酶1(DNMT1)、DNMT3A、DNMT3B基因mRNA的表达。结果表明:EGCG可以剂量依赖性和时间依赖性地抑制U937细胞增殖(r=0.71),且呈剂量依赖性诱导G0/G1期细胞阻滞;EGCG可以呈剂量依赖性上调U937细胞p16mRNA、蛋白的表达;EGCG可以呈剂量依赖性减弱U937细胞p16甲基化程度;EGCG可以剂量依赖性地下调U937细胞DNMT3A、DNMT3B mRNA表达,而对DNMT1mRNA的表达无影响。结论:EGCG在体外通过抑制DNMT3A、DNMT3B和(或)直接使异常高甲基化的p16启动子CpG岛DNA去甲基化,恢复p16mRNA水平和蛋白水平的表达,调控U937细胞阻滞于G0/G1期,抑制U937细胞的增长。     

A new dimethyl sulfoxide-based method for gene promoter methylation detection

The identification of gene promoter methylation is a useful tool for the molecular diagnosis of human diseases. We have developed a new PCR-based technique for detecting the methylation status of CpG islands of gene promoters. This new method, named methyl-sensitive dimethyl sulfoxide-PCR (Ms-DMSO-PCR), is based on the finding that methylated and unmethylated DNAs show a different sensitivity to the amount of DMSO used in the PCR reaction. For the amplification of methylated DNA, more DMSO is required in comparison to unmethylated DNA. This finding resulted in the development of a simple PCR screening of CpG islands with addition of DMSO in the range from 0 to 8% (v/v), and the same pair of primers is sufficient for distinguishing hyper- or hypomethylated gene promoters from normally methylated sequences. This new technique is a one-step procedure and does not require any modifications of DNA or expensive equipment. Therefore, Ms-DMSO-PCR has the potential to be widely used for clinical applications as well in basic research.     

Microarray-based method to analyze methylation status of E-cadherin gene in leukemia

BACKGROUND: Aberrant DNA methylation of the CpG sites of the tumor suppressor gene is closely associated with carcinogenesis. Recently, several studies have indicated the aberrant methylation of E-cadherin gene could be a potential marker for leukemic patients. METHOD: We used bisulfite-modified DNA as a template for PCR amplification, resulting in conversion of unmethylated, but not methylated, cytosine into thymine within CpG islands of interest. The amplified product containing a pool of DNA fragments with altered nucleotide sequences was then hybridized with an oligonucleotide-based microarray. Five sets of oligonucleotide probes were designed to detect the methylation patterns of E-cadherin gene CpG islands in leukemia samples. The results were further validated by methylation-specific PCR (MSP). RESULTS: We found that all leukemia samples were methylated at different levels within the target sequences. The specific regions (the CpG sites #16-19 and #20-22) were revealed as hotspots for methylation in leukemic patients. These results showed that the microarray assay could successfully detect methylation changes of E-cadherin gene in leukemia quantitatively. CONCLUSION: The oligonucleotide-based microarray can be a quick and reliable tool to map methylation status in CpG islands. This established microarray could be potentially useful for clinical researches and diagnosis.     

造血系统肿瘤WT1基因启动子区域DNA甲基化及其调控的研究

目的 应用聚合酶链反应（PCR）的实验方法研究白血病细胞系中WT1基因启动了区域的DNA甲基化水平，及其与WT1基因表达的关系。方法 ①采用RT-PCR技术及甲基化特异性PCR（Methylation-spectific PCR，MSP）技术检测8226、HL-60、Jurkat、KG-1及Raji等血液系统肿瘤细胞系中WT1基因mRNA表达水平及其启动子区域的DNA甲基化状态；②以5-杂氮脱氧胞嘧啶（5-aza-CdR）对U937细胞系进行去甲基化处理，并观察WT1基因表达水平的改变。结果 ①HL-60、K562、KG-1、NB4及SHI-1细胞系中WT1表达水平高，而8226、Jurkat、Raji、U266和U937细胞系WT1表达水平则极低，同时检测到在8226、Jurkat、Raji、U266和U937这5个细胞系存和WT1基因启动子区域DNA高甲基化；②经去甲基化处理后，U937细胞系的WT1基因表达水平较未处理者上升，同时伴随着WT1启动子区域DNA甲基化水平的下降和未甲基化水平的升高。结论 WT1基因启动子区域DNA高甲基化是抑制其表达的机制之一。     

DNA甲基化对TIG1基因在急性白血病中表达的影响

本研究探讨急性白血病细胞中抑癌基因T1G1的表达及其甲基化状态。应用实时荧光定量PCR（real—timeQuantitativePCR，RT—QT—PCR）的方法，检测53例急性白血病（acuteleukemia，AL）患者及20例正常对照者（nom—alcontrols，NC）的TIG1表达情况，并通过甲基化特异性PCR（methylation—sepecificPCR，MS—PCR）检测TIGl基因的甲基化状态。应用去甲基化试剂处理KG-1a、U937和I（562细胞株，观察其基因转录水平和甲基化状态之间的关系。结果表明，TIG1mRNA在NC中高表达，而在AL患者中低表达；AL患者中TIG1的异常甲基化率高达75％（40／53例），而在正常标本中不发生甲基化；在初治AL中，发生甲基化的患者TIGj的表达水平明显低于未甲基化的患者；Kg-1a、U937和K562细胞株TIG1基因启动子CpG岛均存在过甲基化，应用去甲基化试剂处理后，TIG1基因启动子CpG岛甲基化程度降低，T1G1的表达都得到了恢复，并且TIG1的表达随着5-Aza—CdR浓度增加而增高。结论：TIG1基因表达的减少与急性白血病的发病有关，而甲基化是导致TIG1基因转录沉默的重要机制之一。     

Dynamic DNA methylation change in the CpG island region of p15 during human myeloid development

We examined the kenetics of p15 methylation and expression during myeloid development. We treated human cord blood CD34+ cells with either GM-CSF alone or in combination with stem cell factor and followed methylation at this locus using bisulfite genomic sequencing. CD34+ cells were found to be either fully methylated or completely unmethylated at 27 CpG dinucleotide sites in exon 1 and at 18 CpG sites in the promoter region of the p15 gene. A time-course study showed that the percentage of the allelic methylation of p15 CpG island increased to approximately 50% to 60% until 7 days after cytokine stimulation, then decreased to less than 10% after 21 days. The methylation was also observed in bone marrow CD34+ cells exposed to GM-CSF. p15 expression varied inversely with methylation. Expression was negligible or at low levels until 14 days, after which it increased substantially. The frequency of myeloid colony-forming cells in the progeny decreased and myeloid-specific markers increased in the later stages. Based on our observations on cells grown with GM-CSF and 5-aza-2'-deoxycytidine, DNA methylation of the p15 promoter region CpG island appears to be associated with proliferation rather than differentiation of normal human myeloid progenitors.     

In-tube DNA methylation profiling by fluorescence melting curve analysis.

BACKGROUND: Most PCR assays for detection of 5-methylcytosine in genomic DNA entail a two-step procedure, comprising initial PCR amplification and subsequent product analysis in separate operations that usually require manual transfer. These methods generally provide information about methylation of only a few CpG dinucleotides within the target sequence. METHODS: An in-tube methylation assay is described that integrates amplification of bisulfite-treated DNA and melting analysis by using a thermal cycler coupled to a fluorometer (LightCycler). DNA melting curves were acquired by measuring the fluorescence of a double-stranded DNA-binding dye (SYBR Green I) during a linear temperature transition. RESULTS: Analysis of a region comprising 11 CpG sites at the SNRPN promoter CpG island showed that the melting temperature (T(m)) differed by approximately 3 degrees C between unmethylated and fully methylated alleles. This assay could easily distinguish patients with Prader-Willi syndrome or Angelman syndrome from individuals without these conditions. Melting curve analysis also allowed resolution of methylation "mosaicism" at the p15(Ink4b) promoter in bone marrow samples from patients with acute myeloid leukemia (AML). AML samples representing pools of heterogeneously methylated p15(Ink4b) alleles showed broadened melting peaks with overall T(m)s between those of the unmethylated and fully methylated alleles. CONCLUSIONS: Integration of PCR and fluorescence melting analysis may be useful for simple and cost-effective detection of aberrant methylation patterns.     

A microarray to analyze methylation patterns of p16(Ink4a) gene 5'-CpG islands

OBJECTIVES: Aberrant DNA methylation of the CpG site is among the earliest and most frequent alterations in cancer. Several studies suggest that aberrant methylation on the CpG sites of the tumor suppressor gene is closely associated with carcinogenesis. However, large-scale analysis of candidate genes has so far been hampered by the lack of high throughput approach for analyzing methylation patterns. The aim of this study was to develop a new method to analyze methylation patterns of p16(Ink4a) gene. DESIGN AND METHODS: We selected a 336 bp segment of the 5' untranslated region and the first exon of the p16(Ink4a) gene, as the target sequence, which include the most densely packed CpG fragment of the islands containing 32 CpG sites. A set of oligonucleotide probes was designed to assemble a DNA microarray to discriminate the methylation patterns of several adjacent CpG sites. RESULTS: Methylation patterns of human p16(Ink4a) gene were mapped and the results were validated by bisulphite DNA sequencing. A good reproducibility was observed in several parallel experiments. CONCLUSIONS: The methylation oligonucleotide microarray can be applied as a useful and powerful tool to map methylation patterns in multiple CpG island sites.