DNA甲基化与肺癌

DNA异常甲基化是人类肿瘤中常见的改变。发生在启动子区的CpG岛的异常甲基化是基因失活的最常见机制。某些基因甲基化与肺癌发生密切相关,且是肺癌发生中的早期事件。     

肺癌E-cadherin基因启动子CpG岛甲基化的研究

目的检测肺癌组织、相应的癌旁组织及正常肺组织中E-cadherin基因启动子CpG岛甲基化水平，探讨肺癌的发病机制。方法采用甲基化特异性PCR技术检测22例肺癌组织、相应的癌旁组织和9例正常肺组织中E-cad-herin基因启动子CpG岛甲基化水平。结果肺癌中E-cadherin基因启动子CpG岛完全甲基化率为13.6%（3/22），部分甲基化率为27.3%（6/22），总甲基化率为40.9%（9/22），显著高于相应癌旁组织中该基因的甲基化率9.1%（2/22）。9例正常肺组织中该基因未发生甲基化。此外，E-cadherin基因启动子CpG岛异常甲基化与患者性别、年龄无关，甲基化的发生率随着肿瘤的分期早晚有上升的趋势。结论E-cadherin基因启动子CpG岛的异常甲基化是肺癌发生中的常见分子事件，可能参与了肺癌的发生发展过程。     

CDKN2/p16基因5′-CpG岛SmaI位点甲基化与肺癌的关系

目的　研究CDKN2 /p16基因 5′端调控序列CpG岛甲基化的状态与肺癌发生发展的关系。方法　采用对甲基化敏感的核酸内切酶SmaⅠ ,酶切基因组DNA的方法 ,对 89例肺癌标本和 10例正常肺组织的CDKN2 /p16基因进行Southern杂交分析。结果　 89例肺癌中 ,CDKN2 /p16基因甲基化者 15例 ,甲基化频率为 16 .9%。 42例p16蛋白阴性的肺癌患者中 ,有 12例发生甲基化 ,甲基化频率为 2 8.6 % ;另有 47例p16蛋白阳性患者中仅有 3例发生甲基化。 10例正常肺组织中均未发现CDKN2 /p16基因有甲基化现象。结论　CDKN2 /p16基因 5′端CpG岛甲基化是该基因失活的重要机制 ,是肺癌细胞区别于正常细胞的分子事件之一 ,可能参与肺癌的发生发展过程     

DNA甲基化与肺癌关系研究进展

DNA异常甲基化是一种表观遗传改变,常发生在启动子区的CpG岛.某些基因甲基化与肺癌发生密切相关,且是肺癌发生中的早期事件.可能发生在肺癌早期,可以通过去甲基化药物发生逆转.     

肺癌患者组织样品中p16基因的异常甲基化

目的 分析肺癌患者组织样品中p16基因启动子区域异常甲基化的改变情况,评价该指标作为辅助临床诊断的分子标记物的价值。方法 运用甲基化特异性PCR技术,检测51例原发性肺癌患者的肿瘤组织、外周血血浆和痰标本中p16基因启动子区域的异常甲基化改变。结果 在43例肿瘤组织、36例血浆和39例痰标本中检测到了p16基因异常甲基化。凡在肿瘤组织检出p16基因甲基化阳性的病例,其血浆和(或)痰标本也为阳性;而肿瘤组织p16基因甲基化阴性的病例,其血浆和痰标本也为阴性。将血浆和痰标本的p16甲基化分析与痰细胞学检查相结合,可以发现92．2％的肺癌病例。结论 利用半巢式甲基化特异性PCR进行的血浆和痰标本p16基因甲基化分析,有可能成为辅助肺癌诊断的分子生物学指标。     

肺癌患者外周血血浆中p16基因异常甲基化的检测

目的 分析肺癌患者外周血血浆中p16基因启动子区异常甲基化发生情况,探讨血浆中p16基因异常改变作为肺癌临床辅助诊断分子生物学标志物的可能性。方法 利用半巢式甲基化特异性PCR技术,检测了137例肺癌患者血浆和112例相对应肿瘤组织DNA p16基因的异常甲基化情况。结果 在血浆和肿瘤组织中的p16基因甲基化检出率分别为75．2％和80．4％;其中鳞癌、腺癌、腺鳞癌和小细胞肺癌患者血浆标本的阳性率分别为77．9％,65．1％,75．1％和91．7％。血浆DNAp16基因甲基化仅在肿瘤组织存在同样甲基化的病例中被检出。血浆和肿瘤组织中,p16基因的甲基化异常改变与肿瘤的分期、分型无明显相关性。结论 分析血浆DNA的p16基因异常甲基化有可能成为辅助肺癌诊断的有效方法之一。     

p16基因与肺癌关系研究进展

肿瘤抑癌基因p16对于肺癌的早期诊断非常重要,启动子的异常甲基化、第二号外显子的纯合子缺失、基因点突变、蛋白及mRNA的缺失表达都与肺癌的发生关系密切,且与肺癌的基因治疗、药物靶向治疗有关.     

肿瘤表观遗传学研究的新视点-WIF-1基因的甲基化

肿瘤抑制基因的异常甲基化在肿瘤的发生、发展中扮演着重要角色,其甲基化状态可作为肿瘤早期诊断、评价转移和评估预后的重要分子标记,而且抑癌基因的去甲基化亦可为肿瘤提供一种新的治疗方法.候选的抑癌基因WIF-1是Wnt蛋白的内源性分泌型拮抗因子,研究发现其可在多种人类肿瘤中因基因过度甲基化而导致Wnt信号途径的异常激活,促进肿瘤的发生.     

肺癌中FHIT基因异常甲基化及其蛋白表达的意义

目的：检测肺癌组织FHIT蛋白表达及基因异常甲基化，探讨其在肺癌发生发展中的作用。方法：应用免疫组化SP法和甲基化特异性PCR（MSP）检测肺癌组织与癌旁组织（n=60）中FHIT蛋白表达和基因异常甲基化情况，并对基因甲基化扩增产物进行测序，对60例患者随访调查。结果：FHIT蛋白在癌旁组织的阳性表达明显高于癌组织，二者差异存在统计学意义（76．7％vs50．0％，P〈0．05）；FHIT基因异常甲基化在癌组织中的发生率明显高于癌旁组织，二者差异存在统计学意义（68．3％vs35．0％，P〈0．001）；FHIT基因甲基化的发生率在FHIT蛋白阴性患者中高于阳性表达者（83．3％vs53．5％，P〈0．05）；FHIT蛋白表达及基因甲基化发生率均与性别、年龄、吸烟状况、组织学类型、大体分型、TNM分期及淋巴结转移无关（P〉0．05）；FHIT蛋白阳性表达患者生存率高于阴性表达者（P〈0．05），FHIT蛋白是影响无瘤生存时间的危险因素（P〈0．001）。结论：肺癌中FHIT基因异常甲基化频繁发生，FHIT蛋白表达明显下调，FHIT在肺癌的发生发展中可能具有重要的作用，FHIT蛋白可以作为判断患者预后的重要指标。     

肺癌相关抑癌基因甲基化研究进展

肺癌是全球发病率最高的恶性肿瘤之一,它分为两种:小细胞肺癌(SCLC)和非小细胞肺癌(NSCLC)。在临床中80%~85%为NSCLC,SCLC属于内分泌细胞来源的肿瘤,仅占15%~20%。肺癌的发生是多因素多阶段的过程,涉及基因和基因外的多种改变,基因改变指本身结构的异常,方式有点突变、基因缺失、扩增、重排等;基因外(epigenetic)改变即表遗传学改变主要指DNA分子中胞嘧啶发生甲基化,引起基因表达异常,但不改变DNA序列和基因产物。DNA的甲基化在细胞的癌变过程中扮演着重要的角色,是当前分子生物学的研究热点之一。近年研究表明,肿瘤细胞的甲基化…     

Combined Effects Methylation of FHIT,RASSF1A and RARβ Genes on Non-Small Cell Lung Cancer in the Chinese Population

Epigenetic modifications of tumour suppressor genes are involved in all kinds of human cancer. Aberrant promoter methylation is also considered to play an essential role in development of lung cancer, but the pathogenesis remains unclear.We collected the data of 112 subjects, including 56 diagnosed patients with lung cancer and 56 controls without cancer. Methylation of the FHIT, RASSF1A and RAR-β genes in DNA from all samples and the corresponding gene methylation status were assessed using the methylation-specific polymerasechain reaction (PCR, MSP). The results showed that the total frequency of separate gene methylation was significantly higher in lung cancer compared with controls (33.9-85.7 vs 0 %) (p<0.01).Similar outcomes were obtained from the aberrant methylation of combinations of any two or three genes (p<0.01). There was a tendency that the frequency of combinations of any two or three genes was higher in stageⅠ+Ⅱ than that in stage Ⅲ+Ⅳ with lung cancer. However, no significant difference was found across various clinical stages and clinic pathological gradings of lung cancer (p>0.05).These observations suggest that there is a significant association of promoter methylation of individual genes with lung cancer risk, and that aberrant methylation of combination of any two or three genes may be associated with clinical stage in lung cancer patients and involved in the initiation of lung cancer tumorigenesis. Methylation of FHIT, RASSF1A and RARβ genes may be related to progression of lung oncogenesis.     

Identification of GABRA1 and LAMA2 as new DNA methylation markers in colorectal cancer

Aberrant methylation of CpG islands in the promoter region of genes is a common epigenetic phenomenon found in early cancers. Therefore conducting genome-scale methylation studies will enhance our understanding of the epigenetic etiology behind carcinogenesis by providing reliable biomarkers for early detection of cancer. To discover novel hypermethylated genes in colorectal cancer by genome-wide search, we first defined a subset of genes epigenetically reactivated in colon cancer cells after treatment with a demethylating agent. Next, we identified another subset of genes with relatively down-regulated expression patterns in colorectal primary tumors when compared with normal appearing-adjacent regions. Among 29?genes obtained by cross-comparison of the two gene-sets, we subsequently selected, through stepwise subtraction processes, two novel genes, GABRA1 and LAMA2, as methylation targets in colorectal cancer. For clinical validation pyrosequencing was used to assess methylation in 134 matched tissue samples from CRC patients. Aberrant methylation at target CpG sites in GABRA1 and LAMA2 was observed with high frequency in tumor tissues (92.5% and 80.6%, respectively), while less frequently in matched tumor-adjacent normal tissues (33.6% for GABRA1 and 13.4% for LAMA2). Methylation levels in primary tumors were not significantly correlated with clinico-pathological features including age, sex, survival and TNM stage. Additionally, we found that ectopic overexpression of GABRA1 in colon cancer cell lines resulted in strong inhibition of cell growth. These results suggest that two novel hypermethylated genes in colorectal cancer, GABRA1 and LAMA2, may have roles in colorectal tumorigenesis and could be potential biomarkers for the screening and the detection of colorectal cancer in clinical practice.     

Livin与Fas-FasL在肺癌中的表达及意义

凋亡抑制因子Livin和Fas-FasL具有抑制细胞凋亡作用.研究表明Livin在肺癌中过度表达,并促进肿瘤发生发展,Fas-FasL在肺癌中也异常表达.Livin与Fas-FasL的异常表达可能在肺癌变中起协调作用,并有望成为诊断和基因治疗的新靶点.     

Assessing abnormal gene promoter methylation in paraffin-embedded sputum from patients with NSCLC

Aberrant methylation of CpG islands is an important pathway for regulation of gene expression. Recent data suggest that epigenetic abnormalities may occur very early in lung carcinogenesis. We studied the promoters of the four genes, HOX A9, p16(INK4a) (p16), MAGE A1 and MAGE B2 by methylation-specific PCR in matched normal tissue, tumour, and cytological negative sputum samples obtained from 22 patients with non-small cell lung cancer (NSCLC). We further report methylation abnormalities in sputum samples from 56 smokers with differential cytology readouts (negative, inflammatory changes, suspicious, and cancer). Our method was successfully performed on formalin-fixed and paraffin-embedded (FFPE) samples, and was fit to study only few cells obtained by a convenient non-invasive sputum collection and handling. The promoters of MAGE A1 and MAGE B2 had abnormal methylation patterns in, respectively, 50% and 41% of the cytologically negative sputum samples from NSCLC patients, whereas methylation abnormalities of p16 was observed in 27% of negative sputum samples. Interestingly, 95.5% (21 of 22) of the cytologically negative sputum samples from NSCLC patients had abnormal methylation in at least one of the four genes indicating a high sensitivity of this marker system. Moreover, a higher frequency of methylation abnormalities was observed in sputum samples from smokers with high cytological grade compared to low cytological grade. We conclude that the identification of abnormal gene methylation of a limited number of markers in FFPE sputum samples is feasible and may be investigated as a potential system for population-based screening of early stages of lung cancer.     

Quantitative promoter methylation analysis of multiple cancer-related genes in renal cell tumors

Background  

Aberrant promoter hypermethylation of cancer-associated genes occurs frequently during carcinogenesis and may serve as a cancer biomarker. In this study we aimed at defining a quantitative gene promoter methylation panel that might identify the most prevalent types of renal cell tumors.