CpG island methylator phenotype in adenocarcinomas from the digestive tract:Methods,conclusions,and controversies

Over the last two decades, cancer-related alterations in DNA methylation that regulate transcription have been reported for a variety of tumors of the gastrointestinal tract. Due to its relevance for translational research, great emphasis has been placed on the analysis and molecular characterization of the CpG island methylator phenotype(CIMP), defined as widespread hypermethylation of CpG islands in clinically distinct subsets of cancer patients. Here, we present an overview of previous work in this field and also explore some open questions using crossplatform data for esophageal, gastric, and colorectal adenocarcinomas from The Cancer Genome Atlas. We provide a data-driven, pan-gastrointestinal stratification of individual samples based on CIMP status and we investigate correlations with oncogenic alterations, including somatic mutations and epigenetic silencing of tumor suppressor genes. Besides known events in CIMP such as BRAF V600 E mutation, CDKN2 A silencing or MLH1 inactivation, we discuss the potential role of emerging actors such as Wnt pathway deregulation through truncating mutations in RNF43 and epigenetic silencing of WIF1. Our results highlight the existence of molecular similarities that are superimposed over a larger backbone of tissue-specific features and can be exploited to reduce heterogeneity of response in clinical trials.

CpG island methylator phenotype and Helicobacter pylori infection associated with gastric cancer

AIM： To investigate the association between the CpG island methylator phenotype （CIMP） and serum Helico- bacter pylori （H. pylori） levels for clinical prediction of gastric cancer （GC） progression. METHODS： We analyzed the serum ClMP status of 75 patients with GC using a methylation marker panel and a methylation-specific polymerase chain reaction. Serum samples from 40 healthy persons were examined at the same time. The genes examined were APC, WIF-1, RUNX-3, DLC-1, SFRP-1, DKK and E-cad. H. pylori infec- tion in serum was assayed with an anti-H, pylori immu- noglobulin G antibody test and a rapid urease test. RESULTS： The frequencies of high-level methylation in GC tissues for the seven genes were： 48% for APC, 57.33% for WIF-1, 56% for RUNX-3, 50.67% for DLC-1, 52% for SFRP-1, 54.67% for DKK, and 48% for E-cad.The frequencies in GC serum were 30.67% for APC, 34.67% for WIF-1, 37.33% for RUNX-3, 29.33% for DLC-1, 33.33% for SFRP-1, 32% for DKK, and 26.67% for E-cad. CIMP＋ （defined as ≥ 3 methylated genes） was associated with 47 （62.67%） GC tissue samples and 44 （58.67%） GC serum samples. CIMP＋ was not associated with non-neoplastic mucosal tissues or the serum of healthy persons. Of the 75 GC cases, 51 （68%） were H. pylori＋, and 24 （32%） were H. pylori-. Of the 51 H. pylori＋ cases, 36 were CIMP＋ and 15 were CIMP-. In contrast, for the 24 H. pylori- cases, 11 were CIMP＋, and 13 were CIMP-. The difference was signifi- cant between the H. pylori＋ and H. pylori- groups χ2 = 4.27, P 〈 0.05）. Of the 51 H. pylori＋ GC patients, 34 were CIMP＋ and 17 were CIMP-, while among the 24 H. pylori- GC cases, 10 were CIMP＋ and 14 were CIMP-. The difference was significant between the H. pylori＋ and H. pylori- groups （χ2 = 4.21, P 〈 0.05）. A 2-year follow-up showed significant difference in the rates of metastasis and recurrence between H. pylori＋/CIMP＋ cases and the H. pylori＋/CIMP- cases or CIMP- cases associated with H. pylori assayed in serum （P 〈 0.05）. However, there were no significant differences in sur- vival rates between the two groups. CONCLUSION： H. pylori＋/CIMP＋ cases are associ- ated with higher rates of metastasis and recurrence thanH, pylori＋/CIMP- cases. Serum may be useful for examining CIMP status.

CpG island methylator phenotype in plasma is associated with hepatocellular carcinoma prognosis

AIM： To evaluate the clinical significance of CpG island methylator phenotype （CIMP） in plasma and its association with hepatocellular carcinoma （HCC） progress. METHODS： CIMP status of 108 HCC patients was analyzed using a methylation marker panel in tumor tissues and plasma with methylation-specific polymerase chain reaction. Fifteen samples of non-neoplastic liver tissues and 60 of plasma from healthy persons were examined simultaneously. Examined genes included APC, WIF-1, RUNX-3, DI C-1, SFRP-1, DKK and E-cad.26/108, 24.07% in plasma; WIF-1, 53/108, 49.07% in tissue and 35/108, 32.41% in plasma; RUNX-3, 52/108, 48.14% in tissue and 42/108, 38.89% in plasma; DIC-1, 38/108, 35.18% in tissue and 23/108, 21.30% in plasma; SFRP-1, 40/108, 37.04% in tissue and 31/108, 28.7% in plasma; DKK, 39/108, 36.1% in tis- sue and 25/108, 23.14% in plasma; and E-cad, 37/108, 34.3% in tissue and 18/108, 16.67% in plasma. CIMP＋ （≥3 methylated genes） was detected in 68 （60.2%） tumor tissue samples and 62 （57.4%） plasma samples. CIMP was not detected in non-neoplastic liver tissues or plasma of healthy persons. CIMP status in tumor tissues differed significantly in gender, hepatitis B surface antigen, alpha-fetoprotein, and tumor-node- metastasis stage （P 〈 0.05）. Similar results were obtained with plasma samples （P 〈 0.05）. There was no difference in CIMP status in age, presence of hepatitis C virus antibody, cirrhosis, number of nodes, number of tumors, tumor size, or Edmondson-Steiner stage. A one-year follow-up found that the metastatic rate and recurrence rate in the CIMP＋ group were significantly higher than in the CIMP- group as assessed with plasma samples （P 〈 0.05）. CONCLUSION： Plasma DNA can be a reliable sample source for CIMP analysis. CIMP in plasma may serve as a molecular marker of late-stage and poor-prognosis HCC.

Extramural vascular invasion and response to neoadjuvant chemoradiotherapy in rectal cancer: influence of the CpG island methylator phenotype

To identify whether CpG island methylator phenotype (CIMP) is predictive of response to neoadjuvant chemoradiotherapy (NACRT) and outcomes in rectal cancer. METHODSPatients undergoing NACRT and surgical resection for rectal cancer in a tertiary referral centre between 2002-2011 were identified. Pre-treatment tumour biopsies were analysed for CIMP status (high, intermediate or low) using methylation specific PCR. KRAS and BRAF status were also determined using pyrosequencing analysis. Clinical information was extracted from case records and cancer services databases. Response to radiotherapy was measured by tumour regression scores determined upon histological examination of the resected specimen. The relationship between these molecular features, response to NACRT and oncological outcomes were analysed. RESULTSThere were 160 patients analysed with a median follow-up time of 46.4 mo. Twenty-one (13%) patients demonstrated high levels of CIMP methylation (CIMP-H) and this was significantly associated with increased risk of extramural vascular invasion (EMVI) compared with CIMP-L [8/21 (38%) vs 15/99 (15%), P = 0.028]. CIMP status was not related to tumour regression after radiotherapy or survival, however EMVI was significantly associated with adverse survival (P < 0.001). Intermediate CIMP status was significantly associated with KRAS mutation (P = 0.01). There were 14 (9%) patients with a pathological complete response (pCR) compared to 116 (73%) patients having no or minimal regression after neoadjuvant chemoradiotherapy. Those patients with pCR had median survival of 106 mo compared to 65.8 mo with minimal regression, although this was not statistically significant (P = 0.26). Binary logistic regression analysis of the relationship between EMVI and other prognostic features revealed, EMVI positivity was associated with poor overall survival, advanced “T” stage and CIMP-H but not nodal status, age, sex, KRAS mutation status and presence of local or systemic recurrence. CONCLUSIONWe report a novel association of pre-treatment characterisation of CIMP-H with EMVI status which has prognostic implications and is not readily detectable on pre-treatment histological examination.

Nucleosome Positions and Differential Methylation Status of Various Regions within MLH1 CpG Island

Objective： To determine the relationship between nucleosome positions and formation of differential methylation of the reported region A, B, C, and D within the MLH1 CpG island. Methods： Methylation of the MLH1 promoter was analyzed by combined of bisulfite restriction assay. Chromatin of RKO and MGC803 cells were extracted and digested by MNase. Mononucleosomal DNA fragment was isolated and used as templates for detection of nucleosomal distribution by a battery of quantitative PCRs covering the full MLH1 promoter region. Results： The MLH1 was methylated in RKO and unmethylated in MGC803. At the region B, where methylation of CpG sites did not correlated with transcription of this gene well, qPCR product of the M-3 （-599nt ～ -475nt） fragment was amplified in both RKO and MGC803 cells. However, at the region C and D within the core promoter, where methylation of CpG sites correlated with loss of MLH1 transcription well, the M-7 （-257nt ～ -153nt） and M-8 （-189nt ～ -71nt） fragments were amplified remarkably only in RKO cells. Conclusion： Nucleosome may be the basic unit for both CpG methylation and methylation-related regulation of gene transcription. Methylation status of CpG sites within the same nucleosome may be homogeneous; between different nucleosomes, homogeneous or heterogeneous.

Hypermethylation of CpG island in O^6-methylguanine-DNA methyltransferase gene was associated with K-rasG to A mutation in colorectal tumor

AIM: To investigate the functions of promoter hypermethylation of O6-methylguanine-DNA methyltransferase (MGMT) gene in colorectal tumorigenesis and progression.METHODS: The promoter hypermethylation of MGMT gene was detected in 27 sporadic colorectal adenomas,62 sporadic colorectal carcinomas and 20 normal colorectal mucosa tissues by methylation-specific PCR. At the same time, the expression of MGMT protein was carried out in the same samples using immunohistochemistry. Mutantallele-specific amplification was used to detect K-rasG to A point mutation in codon 12.RESULTS: None of the normal colorectal mucosa tissues showed methylated bands. Promoter hypermethylation was detected in 40.7% (11 of 27) of adenomas and 43.5% (27 of 62) of carcinomas. MGMT proteins were expressed in nucleus and cytoplasm of normal colorectal mucosa tissues. Loss of MGMT expression was found in 22.2% (6 of 27) of adenomas and 45.2% (28 of 62) of carcinomas. The difference between them was significant (P = 0.041). In the 6 adenomas and 28 carcinomas losing MGMT expression, 5 and 24 cases presented methylation,respectively (P = 0.027, P＜0.001). Thirteen of the 19 colorectal tumors with K-rasG to A point mutation in codon 12 had methylated MGMT(P = 0.011). The frequencies of K-rasG to A point mutation were 35.3% (12 of 34) and 12.7% (7 of 55) in tumors losing MGMT expression and with normal expression, respectively.CONCLUSION: Promoter hypermethylation and loss of expression of MGMT gene were common events in colorectal tumorigenesis, and loss of expression of MGMT occurs more frequently in carcinomas than in adenomas in sporadic patients. Hypermethylation of the CpG island of MGMT gene was associated with loss of MGMT expression and K-ras G to A point mutation in colorectal tumor. The frequency of K-ras G to A point mutation was increased in tumors losing MGMT expression. It suggests that epigenetic inactivation of MGMT plays an important role in colorectal neoplasia.

Hypermethylation of promoter 5'CpG island of p16 gene in glioma tissue and plasma

Objective: To explore the clinical significance of methylation status of promoter CpG island of p16 gene in glioma tissue and plasma. Methods: Methylation specific polymerase chain reaction (MSP) was used to determine the methylation status of the promoter for p16 gene within glioma tissue and plasma. Immunohistochemical method (SP) was used to analyze the expressions of p16 and Ki-67 proteins. Results: Hypermethylation was found in 17/40 (42.5%) of brain gliomas, in com-parison with 11/40 (27.5%) plasma specimens (χ2 = 1.9780, P = 0.1596). Loss of p16 expression was associated (P = 0.0229) with hypermethylation of CpG island of promoter regions. Hypermethylation of p16 gene CpG island was significantly related to the increase of malignant grade of brain glioma (Tissue: χ2 = 11.4288, P = 0.0007; Plasma: χ2 = 8.9439, P = 0.0028). The Ki-67 index increased significantly (P < 0.05) in brain gliomas methylated in contrast to those unmethylated. Conclusion: P16 hypermethylation may be one of the major mechanisms of tumorigenesis of gliomas. Methylated tumor-specific DNA may be as a plasma biomarker for prognosis in patients with glioma.

CpG Island Definition and Methylation Mapping of the T2T-YAO Genome

Precisely defining and mapping all cytosine(C)positions and their clusters,known as CpG islands(CGIs),as well as their methylation status,are pivotal for genome-wide epigenetic studies,especially when population-centric reference genomes are ready for timely application.Here,we first align the two high-quality reference genomes,T2T-YAO and T2T-CHM13,from different ethnic backgrounds in a base-by-base fashion and compute their genome-wide density-defined and position-defined CGIs.Second,by mapping some representative genome-wide methylation data from selected organs onto the two genomes,we find that there are about 4.7%–5.8%sequence divergency of variable categories depending on quality cutoffs.Genes among the divergent sequences are mostly associated with neurological functions.Moreover,CGIs associated with the divergent sequences are significantly different with respect to CpG density and observed CpG/expected CpG(O/E)ratio between the two genomes.Finally,we find that the T2T-YAO genome not only has a greater CpG coverage than that of the T2T-CHM13 genome when whole-genome bisulfite sequencing(WGBS)data from the European and American populations are mapped to each reference,but also shows more hyper-methylated CpG sites as compared to the T2T-CHM13 genome.Our study suggests that future genome-wide epigenetic studies of the Chinese populations rely on both acquisition of high-quality methylation data and subsequent precision CGI mapping based on the Chinese T2T reference.

人类胎盘基因CpG岛甲基化水平与自然流产的相关性

目的探讨人类胎盘基因CpG岛甲基化水平与孕妇自然流产的相关性。方法选取接受常规产前检查的孕妇55例为研究对象,其中25例自然流产(流产组),30例正常分娩(对照组)。收集入组孕妇的临床资料及人类胎盘组织样本。比较2组临床一般资料。分析相关胎盘基因的甲基化水平对孕妇自然流产结局的预测价值。采用Logistic回归分析法分析孕妇自然流产的影响因素。结果2组在孕妇年龄、流产儿/新生儿出生体质量、孕妇妊娠天数和流产儿/新生儿性别方面比较,差异有统计学意义(P<0.05)。MECP2-1、MECP2-4、HSD11B2、MECP2-3和MECP2-2基因甲基化与自然流产相关。流产组的MECP2-1、MECP2-4、HSD11B2和MECP2-3基因甲基化率高于对照组,差异有统计学意义(P<0.05)。MECP2-1、MECP2-4、HSD11B2、MECP2-3和MECP2-2的曲线下面积(AUC)分别为0.773、0.737、0.700、0.663和0.627。Logistic回归分析结果显示,MECP2-1是孕妇发生流产的独立影响因素(P<0.05)。结论MECP2-1、MECP2-4、HSD11B2、MECP2-3和MECP2-2基因甲基化水平和孕妇的自然流产结局有关。MECP2-1基因是自然流产发生的独立影响因素。

The Most Redundant Sequences in Human CpG Island Library Are Derived from Mitochondrial Genome

An altered pattern of epigenetic modifications, such as DNA methylation and histone modification, is critical to many common human diseases, including cancer. Recently, mitochondrial DNA （mtDNA） was reported to be associated with tumorigenesis through epigenetic regulation of methylation patterns. One of the promising approaches to study DNA methylation and CpG islands （CGIs） is sequencing and analysis of clones derived from the physical library generated by methyl-CpG-binding domain proteins and restriction enzyme MseI. In this study, we observed that the most redundant sequences of 349 clones in a human CGI library were all generated from the human mitochondrial genome. Further analysis indicated that there was a 5,845-bp DNA transfer from mtDNA to chromosome 1, and all the clones should be the products of a 510-bp MseI fragment, which contained a putative CGI of 270 bp. The 510-bp fragment was annotated as part of cytochrome c oxidase subunit II （COXII）, and phylogenetic analysis of homologous sequences containing COXII showed three DNA transfer events from mtDNA to nuclear genome, one of which underwent secondary transfer events between different chromosomes. These results may further our understanding of how the mtDNA regulates DNA methylation in the nucleus.

Predicted methylation landscape of all CpG islands on the human genome

CpG island methylation plays important role in various biological processes. To investigate methylation landscape of all CpG islands on the human genome, we develop a model for predicting the CpG island methylation status. This model outperforms other existing methods. We apply the model on the whole human genome and predict the landscape of DNA methylation of all CpG islands. Based on the methylation profile, we find that about 31% of CpG islands are methylation-prone and CpG islands located in promoter regions are seldom methylated. There is no significant difference in the CpG island methylation level between R and G bands among the chromosomes. The occupancy of RNA polymerase II is significantly higher in methylation-resistant promoter CpG islands, indicating that genes with such promoter CpG islands tend to be more active.

启动子上的增强子和CpG岛在转基因沉默和位置效应中的作用

目的探讨哺乳动物细胞表达载体启动子上增强子和CpG岛调控元件在转基因沉默和位置效应中的作用。方法应用带增强子的八聚体结合转录因子4(OCT4)基因启动子、带CpG岛的性别决定区Y框蛋白2(SOX2)基因启动子、带增强子和CpG岛的巨细胞病毒(CMV)基因启动子以及不含近端增强子和CpG岛的NANOG基因启动子构建哺乳动物细胞表达载体,并分别转染中国仓鼠卵巢细胞株CHO-K1细胞和人胚胎肾细胞(HEK293)。应用Image J软件中Mean算法计算OCT4、SOX2、CMV和NANOG基因启动子在CHO-K1细胞和HEK293细胞介导的增强绿色荧光蛋白(EGFP)表达的荧光强度,应用Image J软件中Mininum、Maxentropy、Mean 3种算法分别计算OCT4、SOX2、CMV和NANOG基因启动子4种载体稳定转染CHO-K1细胞后形成的多个单细胞克隆混合生长样品在同一个样本中最大荧光强度的细胞、大于平均荧光强度的所有细胞和最小荧光强度的所有细胞的EGFP平均荧光强度;应用有限稀释法从G418筛选后获得的稳定转染的多个单克隆混合的CHO-K1细胞中,分别筛选含EGFP的pE-C1、pE-Oct4、pE-Sox2、pE-Nanog质粒稳定转染CHO-K1细胞的单克隆细胞,每个质粒载体随机筛选3个单克隆细胞,应用Image J软件分析EGFP平均荧光强度;应用酶联免疫吸附法检测转染第20、30天CHO-K1细胞中EGFP蛋白表达水平,应用实时荧光定量聚合酶链式反应法检测转染第20、30天CHO-K1细胞中EGFP mRNA表达水平。结果SOX2基因启动子在CHO-K1细胞和HEK293细胞中介导表达的EGFP平均荧光强度比较差异无统计学意义(t=0.770,P>0.05)。OCT4、CMV、NANOG基因启动子在CHO-K1细胞中介导表达的EGFP平均荧光强度显著高于HEK293细胞(t=7.000、11.100、4.900,P<0.05)。SOX2基因启动子于转染第20、30天在CHO-K1细胞中介导表达的EGFP蛋白水平比较差异无统计学意义(t=0.330,P>0.05)。CMV基因启动子于转染第20天在CHO-K1细胞中介导表达的EGFP蛋白水平显著低于转染第30天(t=3.770,P<0.05);OCT4基因启动子于转染第20、30天在CHO-K1细胞中介导表达的EGFP蛋白水平比较差异无统计学意义(t=2.500,P>0.05);NANOG基因启动子于转染第20、30天在CHO-K1细胞中介导表达的EGFP蛋白表达水平比较差异无统计学意义(t=0.014,P>0.05)。转染第20天与转染第30天SOX2、CMV、NANOG基因启动子在CHO-K1细胞中介导表达的EGFP平均荧光强度值比较差异均无统计学意义(t=0.130、0.830、0.210,P>0.05);转染第30天,OCT4基因启动子在CHO-K1细胞中介导表达的EGFP平均荧光强度值显著低于转染第20天(t=5.750,P<0.05)。SOX2、CMV、OCT4、NANOG基因启动子在CHO-K1细胞中介导表达的EGFP蛋白水平比较差异无统计学意义(F=4.070,P>0.05)。CMV、OCT4、NANOG基因启动子在CHO-K1细胞中介导的EGFP mRNA相对表达量显著高于SOX2基因启动子(t=5.440、5.000、5.740,P<0.05);CMV、OCT4基因启动子在CHO-K1细胞中介导的EGFP mRNA相对表达量显著高于NANOG基因启动子(t=3.220、4.270,P<0.05);CMV基因启动子在CHO-K1细胞中介导的EGFP mRNA相对表达量高于OCT4基因启动子,但差异无统计学意义(t=1.270,P>0.05)。SOX2基因启动子介导表达的EGFP在转录水平和转录后水平差异最大(t=16.900,P<0.05);NANOG基因启动子介导表达的EGFP在转录水平和转录后水平差异次之(t=14.930,P<0.05);OCT4和CMV基因启动子介导表达的EGFP在转录水平和转录后水平差异最小(t=2.060、0.430,P>0.05)。应用Mininum、Maxentropy、Mean 3种算法计算OCT4基因启动子在多克隆下介导表达的EGFP的荧光强度比较差异无统计学意义(F=3.720,P>0.05),SOX2、CMV和NANOG基因启动子在多克隆下介导EGFP表达的荧光强度比较差异均有统计学意义(F=516.400、428.500、28.120,P<0.05)。不同单克隆细胞中的差异分析显示,4种载体在不同单克隆细胞中介导表达的EGFP荧光强度值的标准误差相比,从高到低依次为NANOG基因启动子在不同单克隆细胞中介导表达的EGFP荧光强度值标准误差、SOX2基因启动子在不同单克隆细胞中介导表达的EGFP荧光强度值标准误差、OCT4基因启动子在不同单克隆细胞中介导表达的EGFP荧光强度值标准误差、CMV基因启动子在不同单克隆细胞中介导表达的EGFP荧光强度值标准误差,且OCT4基因启动子与SOX2、CMV基因启动子在单克隆细胞中介导表达的EGFP平均荧光强度比较差异有统计学意义(t=3.070、4.360,P<0.05)。结论带CpG岛的启动子能在转录后克服转基因沉默效应,带增强子的启动子具有克服位置效应的作用;二者的恰当组合可用于设计在哺乳动物细胞中高效稳定表达的启动子。

DNA methylation in poultry:a review

As an important epigenetic modification,DNA methylation is involved in many biological processes such as animal cell differentiation,embryonic development,genomic imprinting and sex chromosome inactivation.As DNA methylation sequencing becomes more sophisticated,it becomes possible to use it to solve more zoological problems.This paper reviews the characteristics of DNA methylation,with emphasis on the research and application of DNA methylation in poultry.

绵羊清道夫受体A基因启动子克隆及序列分析

为了分析绵羊清道夫受体A(scavenger receptor A,SRA)基因的启动子序列特征,试验根据UCSC数据库和NCBI数据库预测的绵羊SRA基因启动子序列设计特异性引物,以绵羊肺组织基因组DNA为模板进行SRA基因启动子序列PCR扩增、测序,然后对序列进行生物信息学分析,包括预测启动子活性区域、转录因子结合位点、TATA box及CpG岛。结果表明:利用根据UCSC数据库预测的SRA基因启动子序列设计的引物未扩增出目的片段,利用NCBI数据库预测的SRA基因启动子序列设计的引物扩增得到了绵羊SRA基因启动子序列,大小约为1200 bp,与NCBI预测序列的相似性为99%,其中第577位碱基发生了突变(G→A);含有1个潜在活性区域(aaaaatgagctcacattcattttttttttcttaactggc);存在干扰素调节因子(interferon regulatory factor,IRF)1、IRF2、c-Jun、CCAAT增强子结合蛋白(CCAAT enhancer binding protein,C/EBP)、活化蛋白1(activator protein 1,AP-1)、核因子κB(nuclear factor kappa-B,NF-κB)转录因子结合位点,其中IRF1和c-Jun的结合位点出现频率较高;不存在TATA box和CpG岛,只存在3个CpG位点。说明SRA基因的表达可能受IRF1和c-Jun等相关转录因子的调控,不受甲基化的影响。

ABO基因启动子CpG岛甲基化与白血病的相关性

近年来研究发现ABO血型与许多疾病的发生发展相关,某些肿瘤导致A、B血型物质减少的现象已日益引起关注。本研究探讨ABO基因启动子CpG岛甲基化与白血病的相关性。采用流式细胞仪和激光共聚焦显微镜检测了不同血型的健康人群和各种血液病患者外周血红细胞表面ABH抗原的相对含量,用PCR和MSP-PCR分别检测血液病患者和健康人ABO基因启动子DNA序列和CpG岛甲基化,以及ABO基因启动子-102位点的甲基化。结果发现,白血病患者均出现不同程度的A、B抗原减少;通过对比检测健康人和患者的ABO基因启动子序列,未发现有序列的不同,说明启动子序列高度保守;利用重亚硫酸盐对DNA样本进行修饰后,通过对健康人和患者的ABO基因启动子序列进行扩增和测序,发现健康人和再生障碍性贫血患者在ABO基因启动子的CpG岛区没有甲基化的位点,而急性髓性白血病(AML)、急性淋巴细胞白血病(ALL)、慢性粒细胞白血病(CML)和部分骨髓增生异常综合征(MDS)患者在位置为-102、-101、-100、-99和-97位置的C碱基均有甲基化的现象。结论:甲基化是造成白血病患者AB抗原下降的原因;-102、-101、-100、-99和-97这几个甲基化位点有可能是白血病的特异性表现;针对-102位点检测结果提示-102位点是否甲基化有可能作为白血病鉴别诊断中一个有意义的分子标识物。

CpG岛甲基化表型及OPCML基因甲基化与肝细胞癌发生的关系

背景与目的:CpG岛甲基化表型(CpGislandmethylatorphenotype,CIMP)涉及到多个基因启动子同时甲基化,具有肿瘤特异性,与多种肿瘤的发生或预后相关,但有关肝癌CPG岛甲基化表型的研究罕见报道。OPCML(opioid-bindingprotein/celladhesionmolecule-like)基因目前多为针对上皮性卵巢癌的研究,被认为是卵巢癌的候选抑癌基因。本研究旨在探讨CIMP及OPCML基因与肝癌的发生是否有关。方法:运用甲基化特异性PCR方法检测50例肝细胞癌组织及48例癌旁组织中OPCML、p15、SOCS-1、GST-p、RAR-b、p16、p73、p14、MGMT和hMLH1基因的甲基化状况。结果:肝癌组织甲基化率普遍比相应癌旁组织甲基化率高:OPCML(70.0%vs.64.6%)、p15(58.0%vs.50.0%)、SOCS-1(78.0%vs.50.0%)、GST-p(56.0%vs.27.1%)、RAR-b(30.0%vs.6.3%)、p16(26.0%vs.14.6%)、p73(16.0%vs.0%)、p14(36.0%vs.27.1%)、MGMT(16.0%vs.10.4%)和hMLH1(18.0%vs.4.2%)。SOCS-1,GST-p,RAR-b,p16和p73基因甲基化率在肝癌组与癌旁组差异有显著性(P<0.05),其它基因两组之间的甲基化率差异无显著性。CIMP阳性组(同时具有≥3个位点甲基化)复发时间较早,1年无瘤生存率为18.2%,而CIMP阴性组(具有<3个位点甲基化)复发时间较晚,1年无瘤生存率为75.0%(P<0.05)。结论:肝癌中存在着CpG岛甲基化表型(CIMP),CIMP可作为肝癌患者预后判断的指标之一;OPCML基因甲基化可能在肝癌的发生中发挥重要的作用。

血液系统恶性肿瘤致ABO基因甲基化状态异常的影响及分析

目的检测血液系统恶性肿瘤患者和健康献血员ABO基因启动子区CpG岛甲基化状态,分析ABO基因甲基化与血液系统恶性肿瘤的相关性,初步探讨ABO基因甲基化状态异常在血液系统恶性肿瘤中的临床意义。方法收集2020年7月至2023年3期间送检至血液中心6例血液系统恶性肿瘤患者标本和20例健康献血员标本作为研究对象。应用血型血清学技术检测ABO血型抗原情况,应用亚硫酸氢盐测序法(BSP)检测ABO基因启动子CpG岛甲基化状态。结果血液系统恶性肿瘤患者中有2例出现ABO抗原减弱,而健康对照组均未检测出ABO抗原减弱现象;经亚硫酸氢盐转化测序法检测病例组(n=6)和对照组(n=20)标本ABO基因甲基化状态,发现血液系统恶性肿瘤患者(甲基化率73.08%)ABO基因甲基化率显著高于随机选取的对照组样本(甲基化率38.08%),差异有统计学意义(P<0.001)。结论罹患血液系统恶性肿瘤与ABO血型抗原减弱相关联,且ABO基因启动子区CpG岛甲基化与血液系统恶性肿瘤的发生相关,这为探索血液系统恶性肿瘤ABO血型抗原减弱的分子机理提供了理论依据。

人原发性肝癌中p16基因表达及CpG岛甲基化状态的研究

目的 进一步探讨人原发性肝癌中 p16基因 m RNA转录水平变化与其基因启动子区 Cp G岛甲基化的关系 ,及其在肝癌发生中的意义。方法 采用狭缝印迹杂交检测 2 0例人原发性肝癌及相应的癌旁、远癌组织及 2例正常人肝组织中 p16基因 m RNA表达水平 ,以甲基化特异性 PCR分析各组织中 p16基因启动子区 Cp G岛的甲基化状况 ,并进行统计分析。结果 2 0例人原发性肝癌中 14例 (70 % ) p16 m RNA水平比远癌组织显著降低 ;13例 (6 5 % )显示 p16基因启动子区 Cp G岛甲基化 ,其中 84 .6 % (11例 )伴 p16 m RNA转录水平降低。结论 人原发性肝癌中存在高频率的 p16基因表达失活 ,其主要机制可能是启动子区 Cp G岛甲基化抑制了基因的转录 ,在人原发性肝癌的发生发展中有重要作用。其临床诊断和治疗意义有待进一步深入研究。

胃癌E-cadherin基因启动子CpG岛甲基化的研究

背景与目的:目前认为CpG岛甲基化导致转录抑制是恶性肿瘤发生的重要机制之一。E-cadherin能抑制肿瘤细胞的浸润和转移,被公认为是浸润、转移抑制基因。低分化胃癌常表现有E-cadherin基因失活。我们通过检测胃癌及癌旁组织中E-cadherin基因启动子CpG岛甲基化水平,初步探讨胃癌的发病机制。方法:采用特异性甲基化PCR(MSP)法检测51例胃癌组织及37例癌旁组织中的E-cadherin基因启动子CpG岛甲基化水平,采用免疫组织化学染色法检测E-cadherin表达。结果:健康对照组织中未检测到CpG岛甲基化,4例(10.8%)癌旁组织检测到CpG岛甲基化,32例(62.7%)胃癌组织中检测到CpG岛甲基化。低分化腺癌(72.2%,26/36)CpG岛甲基化显著高于高分化腺癌(33.3%,6/15)(P<0.01),T1/T2期(55.6%,10/18)与T3/T4期胃癌(66.7%,22/33)的CpG岛甲基化率无显著性差异(P>0.05)。32例CpG岛甲基化胃癌中27例(84.5%)E-cadherin表达下调,19例非甲基化胃癌中5例(26.3%)E-cadherin表达下调。未发现E-cadherin基因CpG岛甲基化与幽门螺杆菌感染有关。结论:胃癌、尤其是低分化腺癌广泛存在E-cadherin基因启动子CpG岛甲基化,启动子CpG岛甲基化可能参与胃癌的早期过程,E-cadherin基因CpG岛甲基化与幽门螺杆菌感染无相关关系。

食管鳞状细胞癌中Smad4基因CpG岛甲基化状态分析

目的:探讨食管鳞状细胞癌(esophageal squamous cell carcinoma,ESCC)中Smad4(mothers against decapentaplegic homolog4)基因启动子区及第一外显子区的CpG岛甲基化状态及其与Smad4蛋白、TGF-β1蛋白表达之间的相关性。方法:128例ESCC组织标本采集自河北医科大学第四医院2004-2008年的手术病例,每例患者均取癌旁正常黏膜组织作对照。分别应用甲基化特异性PCR(methylmion specific PCR,MSP)、RT-PCR和免疫组织化学法检测ESCC组织及相应癌旁组织中Smad4基因CpG岛的甲基化情况、Smad4 mRNA和Smad4蛋白表达情况,应用免疫组织化学法检测TGF-β1的蛋白表达情况。结果:ESCC组织中Smad4基因启动子区CpG岛甲基化率为5.5%(7/128),第一外显子5′非翻译区CpG岛甲基化率为30.5%(39/128);相应癌旁正常黏膜组织均未检测到这两个位点的甲基化(P<0.05);ESCC组织中Smad4甲基化率显著高于癌旁正常组织(P<0.05)。ESCC组织中Smad4 mRNA及蛋白表达显著低于癌旁正常组织(P<0.05),且与Smad4甲基化相关。TGF-β1蛋白在ESCC组织中的表达率(66.4%)显著高于相应癌旁正常组织(21.9%,P<0.01),且随ESCC分期的增高和分化程度的降低而升高(P<0.05)。Smad4和TGF-β1蛋白在ESCC中的表达呈明显的负相关(P<0.01)。结论:Smad4基因CpG岛甲基化及TGF-β1的过表达可能是ESCC发生机制之一,其中Smad4基因第一外显子5′非翻译区CpG岛比启动子区CpG岛更易发生甲基化,从而导致Smad4基因沉默。