错配修复基因启动子甲基化与胰腺癌发生的关系

目的通过对胰腺癌错配修复基因启动子甲基化及蛋白表达的检测与微卫星不稳定性的分析,探讨胰腺癌发病的分子机制。方法从35例胰腺癌病人的正常胰腺组织、癌组织中提取DNA;MSP法检测hMLH1及hMSH2基因启动子甲基化状态;SSCP法检测标本中微卫星不稳定性发生情况;免疫组化法检测错配修复基因hMLH1及hMSH2在胰腺癌中的表达情况。结果35例胰腺癌中hMLH1启动子甲基化发生率为60％（21／35）,正常组织中未发现甲基化,两者之间有统计学差异（P〈0.05）;而对于hMSH2仅有1例胰腺癌出现启动子甲基化;35例胰腺癌中微卫星高度不稳定7例,低度不稳定14例,稳定11例,正常组织中没有出现微卫星不稳定,两者之间有统计学差异（P〈0.05）;在微卫星不稳定的21例胰腺癌组织中有19例（90％）出现hMLH1启动子甲基化现象,微卫星稳定的ll例胰腺癌组织中仅有2例（6％）出现hMLH1启动子甲基化。hMLH1启动子甲基化在微卫星不稳定胰腺癌组织中常为缺失表达或低表达,在微卫星稳定胰腺癌组织中呈正常表达。hMSH2无论在MSI-H或MSI-L胰腺癌与正常胰腺组织中均无缺失表达,仅部分低表达。结论胰腺癌组织中错配修复基因的缺陷主要是hMLH1启动子甲基化,与胰腺癌微卫星不稳定性及蛋白表达缺失有关,在胰腺癌发生过程中起重要作用,是胰腺癌发生的重要机制之一。     

胰腺癌中微卫星不稳定性与错配修复基因表达的相关性研究

本研究检测35例胰腺癌标本中的5个微卫星位点，用单链构象多态性（SSCP）法对标本进行微卫星不稳定（MSI）分析，进一步检测胰腺癌及正常胰腺组织中hMSH2和hMLHl的蛋白表达及启动子CpG岛甲基化状态，分析MSI与胰腺癌错配修复基因表达之间的联系，探讨MSI致癌的可能机制。     

结直肠癌环氧化酶-2、错配修复酶-1微卫星不稳定与基因调控的关系

目的 检测临床手术切除42例结直肠癌及相应正常组织环氧化酶-2(COX-2)、错配修复酶-1(hMLH1)微卫星不稳定状态(MSI)及二种基因启动子甲基化,探讨它们与结直肠癌发生的关系.方法 采用聚合酶链反应(PCR)技术检测5个位点的MSI状态;甲基化特异性PCR(MSP)方法检测结直肠癌及正常组织COX-2、hMLH1二种基因启动子CpG岛甲基化状态.结果 42例结直肠癌中MSI总检出率为42.86%(18/42),5个位点的MSI检出率差异无统计学意义(P＞0.05).COX-2和hMLH1基因启动子CpG岛甲基化在42例结直肠癌中分别有13例和15例.MSI-H组中COX-2基因启动子CpG岛甲基化8例,且有6例结直肠癌同时出现hMLH1和COX-2基因启动子CpG岛甲基化.结论 MSI结直肠癌hMLH1基因启动子CpG岛甲基化率高于MSS结直肠癌,hMLH1基因启动子CpG岛甲基化有助于判断肿瘤类型.     

膀胱移行细胞癌微卫星不稳定性表达及机理探讨

目的 探讨微卫星不稳定性在膀胱移行细胞癌的表达及其作用机制。方法 用PCR方法分析35例膀胱移行细胞癌尿沉渣标本中微卫星不稳定性表达;用RT-PCR方法监测5种人类错配修复基因在膀胱癌细胞系mRNA转录水平的表达;用PCR方法检测膀胱癌细胞系BIU-87中错配修复基因hMLH1的启动子区域出现异常甲基化。结果 35例膀胱癌患者尿沉渣中,有31例（88.6%)可检出微卫星不稳定性表现;5种人的错配修复基因在BIU-87膀胱癌细胞系中有hMLH1和hMSH2表达缺失,而在正常近曲小管细胞系中都有表达;BIU-87细胞错配修复基因hMLH1的启动子区域出现异常甲基化,应用去甲基化剂处理后可检测到hMLH1的启动子区域的表达,再次去除去甲基化剂后叠不能检测hMLH1的启动子区域。结论 微卫星不稳定性与错配修复基因表达有关。甲基化对膀胱癌细胞系BIU-87错配修复基因hMLH1的表达具有调控作用。     

散发性结直肠癌CpG岛甲基子表型和基因组遗传学不稳定性的关系

目的探讨散发性结直肠癌CpG岛甲基子表型和基因组不稳定性的关系。方法对采用甲基化特异性PCR的方法对71例散发性结直肠癌组织进行P14^ARF、hMLH1、P16^INK4a、MGMT和MINT1共5个基因启动子甲基化的检测,确定CpG岛甲基子表型;选择BAT25和BAT26两个位点进行微卫星不稳定检测和流式细胞术检测分析倍体类型;分析散发性结直肠癌中CpG岛甲基子表型和微卫星不稳定、染色体不稳定的关系。结果全组结直肠癌组织中CpG岛甲基子表型的阳性率为21.1%（15/71）;微卫星不稳定的阳性率为9.9%（7/71）;异倍体的阳性率为73.5%（50/68）。CpG岛甲基子表型阳性者,微卫星不稳定的阳性率高于阴性者（20.0%vs7.1%）,但差异无统计学意义（P=0.158）。hMLH1基因启动子甲基化阳性者微卫星不稳定的比例为57.1%,高于阴性者的4.7%（P=0.001）。CpG岛甲基子表型阳性者二倍体的比例高于阴性者（61.5%vs.18.2%,P=0.003）。结论CpG岛甲基子表型阳性的散发性结直肠癌具有显著的二倍体倾向,多基因同时甲基化和染色体不稳定可能是两种相互独立的基础性发病机制。     

微卫星不稳定结直肠癌hMLH1和hMSH2及hMSH6种系突变与hMLH1启动子甲基化检测

目的探究微卫星不稳定（MSI）结直肠癌患者的hMLH1、hMSH2和hMSH6种系突变特征和hMLH1启动子甲基化状态。方法对前瞻性收集的34例MSI结直肠癌患者检测其hMLH1、hMSH2和hMSH6种系突变，并研究其肿瘤的hMLH1启动子甲基化状态。结果34例MSI结直肠癌中。共检测到MLH1基因启动子的甲基化19例（55．9％）。19例MSI—H结直肠癌中检测到MLH1基因的甲基化14例（73．7％）；15例MSI—L结直肠癌检测到MLH1基因的甲基化5例（33．3％）；两组差异有统计学意义（P〈0．05）。全组共发现8个hMSH2和hMSH6基因的突变，其中hMSH6基因突变3个，hMSH2基因突变5个。结论中国人MSI结直肠癌错配修复基因突变（未测到MLH1基因突变）和MLH1基因启动子的甲基化检出率可能有别于国外MSI结直肠癌。     

散发性结直肠癌微卫星不稳定与hMHL1和hMSH2基因突变的研究

目的:探讨散发结直肠癌组织微卫星不稳定性与错配修复基因hMHL1和hMSH2蛋白表达的关系。方法:结直肠癌患者病理标本和正常肠壁组织(距肿瘤边缘10cm取材各40例)。选取微卫星位点(D2S123、BAT-26、D17S261、D17S799)进行PCR,PCR产物行毛细管电泳法检测。用免疫组化染色方法分析错配修复基因hMHL1和hMSH2在肿瘤组织的蛋白表达情况。结果:1)4个位点(D2S123、BAT26、D17S261、D17S799)的微卫星不稳定性检出率分别为:12.5%、17.5%、10%、7.5%。总的微卫星不稳定率为9/40(22.5%)。MSI-H表达为7例,均表现BAT26位点不稳定。MSI-L表达2例。2)所有标本错配修复基因hMSH2检测均正常表达。错配修复基因hMHL1表达阴性11份,结肠比直肠hMLH1蛋白的阴性表达率高(P0.01)。3)hMLH1表达阴性,是出现MSI的重要分子因素,hMLH1不表达和MSI相关显著(P0.01)。结论:1)错配修复基因突变引起微卫星不稳定性是散发性结肠癌发生的重要机制;2)部分微卫星不稳定性是由错配修复基因hMLH1不表达引起,其余的微卫星不稳定性可能涉及到其它错配修复基因。     

膀胱移行细胞癌中DNA错配修复基因hMLH1、hMSH2和hMSH3启动子区甲基化状态研究

目的探讨DNA错配修复基因启动子区CpG岛甲基化状态及其在膀胱移行细胞癌（BTCC）中的表达。方法应用MSP技术检测膀BTCC中hMLH1、hMSH2和hMSH3基因启动子区甲基化状态,RT-PCR法检测其mRNA表达水平。结果36例BTCC组织中hMSH1、hMSH2的甲基化阳性率分别为38.9％（14／36）、52.8％（19／36）,所有标本中均未发现有hMSH3启动子甲基化。hMLH1、hMSH2、hMSH3 mRNA在BTCC中表达率分别为47.2％（17／36）、38.9％（14／36）、16.7％（6／36）,在正常组织中分别为22.2％（8／36）、63.9％（23／36）、0％（0／36）,差异均有统计学意义（P〈0.01）,并且随肿瘤病理分级的增加呈下降趋势（P〈0.05）,均与临床分期不相关（P〉0.05）。结论hMLH1、hMSH2和hMSH3基因启动子异常甲基化可能导致该基因转录表达失活,使其mRNA表达减少甚至缺失,这可能是导致BTCC发生、发展的原因之一。     

胰腺癌SOCS-1基因异常甲基化研究

目的：探索人类胰腺癌中SOCS—1基因是否由于异常甲基化而表达抑制；查询此现象在胰腺癌的发生、发展中的意义。方法：采集25例胰腺导管腺癌病人的肿瘤标本及5例对应的正常胰腺组织，运用甲基化特异性PCR反应研究胰腺癌组织中SOCS—1基因CpG岛甲基化状态，同时运用实时定量PCR分析SOCS—1基因的表达。结果：25例胰腺导管腺癌病人中有9例（36％）SOCS—1基因呈CpG岛甲基化，而正常组织则无SOCS—1基因CpG岛甲基化；SOCS—1基因CpG岛甲基化组的SOCS—1基因表达量与无SOCS—1基因CpG岛甲基化组相比，其基因相对表达量明显减少（P〈0．05），证明SOCS—1基因CpG岛甲基化可以抑制SOCS—1基因表达。与病人临床病理特征相结合比较．发现SOCS—1基因CpG岛甲基化与年龄、性别、肿瘤体积、肿瘤分化程度及TNM分期等因素无关。结论：在胰腺导管腺癌中存在SOCS—1基因CpG岛甲基化，且由于CpG岛甲基化而促使基因表达抑制。SOCS—1基因CDG岛甲基化在胰腺癌的发生、发展中可能具有一定的作用。     

hMLH1/hMSH2基因启动子变异在遗传性非息肉病性结直肠癌发生中的作用

目的 探讨hMLH1及hMSH2基因启动子变异在遗传性非息肉病性结直肠癌(HNPCC)发生中的作用。方法 PCR法扩增25例HNPCC患、20例散发性结直肠癌和10例非肿瘤患的hMLH1及hMSH2基因启动子序列，对PCR产物进行测序。对发现携带突变患的肿瘤标本进行hMLH1及hMSH2基因表达研究和微卫星不稳定(MSI)检测，同时用测序方法检测该患hMLH1及hMSH2基因编码序列的改变。结果55例检测样本中，C3．1及C3．2发现hMLH1启动子在-342位和-337位2处A插入变异，免疫组化检测该患hMLH1表达阴性，肿瘤MSI检测为MSI—H，而编码序列的检测未发现异常。结论 hMLH1／hMSH2基因启动子种系突变可能导致该基因的不表达，从而导致HNPCC结直肠癌的发生。错配修复基因编码序列正常的HNPCC患中可能存在该基因启动子突变。     

Genetic analysis of hMLH1 in transitional cell carcinoma of the urinary tract: promoter methylation or mutation

PURPOSE: Loss of DNA mismatch repair due to diminished expression or mutation of hMLH1 is associated with genomic instability followed by cancer. We performed genetic analyses of hMLH1 to determine whether hMLH1 alterations have a role in urothelial tumorigenesis. MATERIALS AND METHODS: We examined genomic DNA from 118 sporadic transitional cell carcinomas, including 83 bladder and 35 renal pelvis or ureter cases, for aberrant promoter methylation and mutation in the hMLH1 gene. Immunohistochemical reactivity to hMLH1 protein and genome instability in these transitional cell carcinomas were also studied. RESULTS: Two of the 118 cases (1.7%) had microsatellite instability and hMLH1 promoter methylation with loss of or reduced hMLH1 protein expression. A single transitional cell carcinoma (0.8%) without microsatellite instability had an hMLH1 missense mutation with a C-to-T transition, resulting in the substitution Arg217 --> Cys. Immunostaining with antihMLH1 antibody was found in this transitional cell carcinoma. CONCLUSIONS: To our knowledge these findings provide the first in vivo evidence for the type and frequency of possible involvement of promoter methylation and mutation of hMLH1 in sporadic urothelial transitional cell carcinoma. They also suggest that hMLH1 alterations may not account for many cases of sporadic transitional cell carcinoma tumorigenesis.     

Phenotype of microsatellite-stable colorectal carcinomas with CpG island methylation

A distinctive pathway of colorectal carcinogenesis termed CpG island methylator phenotype is characterized by extensive DNA methylation in colorectal carcinoma (CRC) cells but not in nonneoplastic mucosa. Many CRCs with CpG island methylator phenotype have methylation of the hMLH1 mismatch repair gene and consequently have high levels of microsatellite instability (MSI-H). MSI-H confers distinctive clinical-pathologic features, but the phenotype of microsatellite-stable CRC with methylation has not been characterized in detail. We therefore examined the clinical-pathologic features of 87 sporadic microsatellite-stable CRCs that had been characterized for methylation of p16, p14, MGMT, hMLH1, MINT1, MINT2, and MINT31. Regression analyses of each clinical-pathologic characteristic were run against the individual and aggregated methylation markers to evaluate and quantify associations. CpG island methylation was associated with right-sided carcinoma (odds ratio = 6.9, P = 0.03). Paucity of gland formation, indicating poor differentiation, was strongly associated with methylation (beta = -42.6, P = 0.0008), as were presence of cribriform glands (beta = 34.3, P = 0.02) and lack of corkscrew/serrated glandular pattern (beta = -32.5, P = 0.03). Our epigenotype-phenotype correlation study shows that microsatellite-stable CRC with CpG island methylation have a distinctive pathologic phenotype with both similarities to and differences from MSI-H tumors.     

Prognostic value of hMLH1 methylation and microsatellite instability in pancreatic endocrine neoplasms

BACKGROUND: The aberrant promoter methylation of the mismatch repair gene, hMLH1, is associated with microsatellite instability (MSI) in cancer cells and often is associated with a favorable prognosis. METHODS: Pancreatic endocrine neoplasms (PENs) were obtained from 48 patients who underwent surgical resection. Methylation-specific polymerase chain reaction was used to detect methylation in the hMLH1 promoter. Tumor MSI at loci BAT26, BAT25, D2S123, D5S346, and D17S250 was determined with microsatellite polymerase chain reaction. RESULTS: Hypermethylation of the hMLH1 promoter was present in 11 of 48 PENs (23%). Five of the 11 hMLH1-methylated PENs were found to be microsatellite unstable, and MSI was restricted to PENs with hMLH1 hypermethylation. Tumor recurrence at 2 years after surgical resection was significantly less common among the hMLH1-methylated PENs (11%), compared with the unmethylated PENs (35%; P=.038). Patients with hMLH1-methylated PENs experienced improved 5-year survival (100%) compared with patients with unmethylated tumors (56%; P=.010). Likewise, MSI-positive PENs were associated with improved survival compared with MSI-negative tumors (100% vs 59%; P=.017) at 5 years. CONCLUSION: As in hereditary nonpolyposis colorectal cancer in which MSI is associated with improved survival, methylation of hMLH1 leads to MSI in PENs and affords a favorable prognosis.     

Promoter hypermethylation: an important epigenetic mechanism for hMLH1 gene inactivation in head and neck squamous cell carcinoma.

OBJECTIVE: The hMLH1 gene is one of the mismatch DNA repair genes. Inactivation of the hMLH1 gene has been implicated in the tumorigenesis of many types of human cancers. In most sporadic forms of human cancers, promoter hypermethylation is responsible for hMLH1 gene inactivation. Lack of hMLH1 protein expression has been found in a subset of head and neck squamous cell carcinomas (HNSCCs). The purpose of this study was to investigate whether promoter hypermethylation causes hMLH1 gene inactivation in HNSCCs. STUDY DESIGN: hMLH1 protein expression was determined by immunohistochemical staining in 62 cases, whereas hMLH1 gene promoter methylation was analyzed by methylation-sensitive restriction enzyme digestion, followed by polymerase chain reaction, in 35 cases of HNSCCs. RESULTS: Sixteen (26%) of 62 cases of HNSCCs showed near-complete loss of hMLH1 protein expression on immunohistochemical staining. Twelve (92%) of 13 cases that were negative for the hMLH1 protein displayed promoter hypermethylation, whereas 17 (77%) of 22 cases positive for the protein were free of promoter methylation. CONCLUSIONS: Promoter hypermethylation may be an important mechanism for hMLH1 gene inactivation in a subset of HNSCCs.     

乳腺癌WWOX基因表达缺陷的意义及其与CpG岛甲基化的关系

目的 研究WWOX蛋白在乳腺癌组织和细胞系中的表达变化,分析其与WWOX基因启动子和第一外显子CpG岛甲基化的关系.方法 应用免疫组织化学染色检测乳腺癌组织和细胞系中WWOX蛋白表达,采用甲基化特异性PCR(methylation-specific PCR,MSP)分析乳腺癌组织和细胞系中WWOX基因CpG岛甲基化状况.结果 32.2%的乳腺癌组织和5.4%正常乳腺组织中WWOX蛋白表达缺失,差异有统计学意义(P＜0.01).乳腺癌组织WWOX表达异常与绝经后状态(P＜0.01)关系密切.Ⅰ、Ⅱ、Ⅲ期患者中WWOX蛋白表达缺失的比例分别为23.1%、28.6%和46.2%.55%的乳腺癌组织WWOX启动子CpG岛甲基化扩增,45%的乳腺癌组织WWOX第一外显子CpG岛甲基化扩增,癌旁组织中未出现CpG岛甲基化扩增.MDA-MB-231细胞WWOX基因CpG岛完全甲基化,而MCF-7细胞无甲基化产物扩增.结论 乳腺癌中广泛存在着WWOX基因CpG岛甲基化,是WWOX表达缺陷的重要机制,并且可能通过性激素受体信号途径在乳腺癌的发生、发展中发挥作用.