DNA错配修复蛋白(MLH1,PMS2,MSH2,MSH6)与人类神经管畸形(NTDs)关联性的初步研究

目的通过观察神经管畸形(Neural Tube Defects,NTDs)患儿与正常胎儿脑组织中DNA错配修复(mis-match repair,MMR)蛋白MLH1、PMS2、MSH2及MSH6的表达情况,探讨MMR系统与NTDs发生机理间可能存在的联系。方法 NTDs患儿脑组织及正常胎儿脑组织各15例,运用免疫组化方法检测各病例中MLH1、PMS2、MSH2及MSH6蛋白表达情况。结果 NTDs组MLH1阳性率中位数为1.44%,正常组为(41.96±11.01)%,中位数为43.95%;NTDs组PMS2阳性率为(25.48±16.46)%;正常组为(43.36±7.86)%。NTDs组中两种蛋白较正常组明显下降,组间存在统计学差异(P0.01)。但NTDs组中MSH2及MSH6阳性率分别为(43.56±18.67)%、(32.26±23.18)%;正常组中为(45.87±8.49)%、(35.15±10.68)%。两种蛋白组间比较无统计学差异,P值分别为0.6516和0.5387。结论首次报道NTDs中可能存在一种或多种特定MMR蛋白表达异常,推测MMR系统表达异常可能在NTDs发生过程中起到重要作用。     

结直肠癌中错配修复基因表达与临床病理及Pgp、GSTπ、TopoⅡ、Ki-67表达的关系研究

目的：探讨结直肠癌错配修复基因(MLH1,PMS2,MSH2,MSH6)免疫组化表达特点及其与临床病理的关系,以及错配修复基因(MLH1,PMS2,MSH2,MSH6)与结直肠癌中P-糖蛋白(Pgp)、谷胱甘肽-S-转移酶(GSTπ)、DNA拓扑异构酶Ⅱ(TopoⅡ)、细胞增殖抗原Ki-67免疫组化表达关系。方法：回顾性分析2014年2月至2015年12月我院收治的93例结直肠癌患者的临床病理资料,采用免疫组织化学法,检测癌组织中错配修复基因(MLH1,PMS2,MSH2,MSH6)、Pgp、GSTπ、TopoⅡ、Ki-67的表达,分析其表达特点。采用多个样本率(或构成比)的比较(即：R×C表的χ2检验),分析结直肠癌错配修复基因(MLH1,PMS2,MSH2,MSH6)与临床病理的关系及其与Pgp、GSTπ、TopoⅡ、Ki-67免疫组化表达关系。利用Pearson相关分析法分析MLH1、PMS2、MSH2、MSH6与Ki-67表达相关性。结果：错配修复基因MLH1、PMS2、MSH2、MSH6表达缺失阳性率分别占14.0%、17.2%、10.8%、11.8%,Pgp(?)、Pgp (+)、Pgp (++)、Pgp (+++)表达率分别占3.2%、25.8%、51.6%、19.3%。GSTπ(?)、GSTπ(+)、GSTπ(++)、GSTπ(+++)表达率分别占3.3%、16.7%、56.7%、23.3%。TopoⅡ阴性表达及IV级表达未见,TopoⅡⅠ级、Ⅱ级、Ⅲ级表达率分别占19.3%、77.4%、3.2%。Ki-67表达<10%(+)、10-50%(+)、>50%(+)分别占1.3%、25%、50%。错配修复基因MLH1、PMS2、MSH2、MSH6缺失表达与患者的性别、年龄、病理分化、TNM分期无统计学差异(P>0.05)。MSH2缺失表达与发病部位无统计学差异(P>0.05)。MLH1、PMS2、MSH6基因缺失表达与发病部位有一定差异性(P<0.05),发生左半结肠的缺失表达阳性率分别为：10.7%、10.7%、7.1%,右半结肠缺失表达阳性率分别为28.6%、35.7%、25%,直肠缺失表达阳性率为5.4%、8.1%、5.4%。MLH1、PMS2、MSH2、MSH6缺失表达与Pgp、GSTπ、TopoⅡ的表达无统计学差异(P>0.05)。MLH1、PMS2、MSH2、MSH6缺失表达与Ki-67表达有一定差异性(P<0.05), Ki-67<10%(+)的MLH1、PMS2、MSH2、MSH6缺失表达率为62.5%,Ki-6710%~50%(+)的MLH1、PMS2、MSH2、MSH6缺失表达率分别为21.1%、0、10.5%、5.3%,Ki-67>50%(+)的MLH1、PMS2、MSH2、MSH6缺失表达率分别为6.1%、4.1%、8.2%、6.1%。MLH1、PMS2、MSH2、MSH6缺失表达与Ki-67表达呈负相关(相关系数分别为r=?0.969、r=?0.464、r=?0.143、r=?0.344, P<0.05)。结论：错配修复基因MLH1、PMS2、MSH6基因缺失表达发生右半结肠几率相对较高,其次依次是左半结肠、直肠。MLH1、PMS2、MSH2、MSH6缺失表达与Ki-67表达呈负相关。     

658例结直肠癌错配修复蛋白的表达及其与临床病理特征的关系北大核心CSCD

目的探讨错配修复（mismatch repair,MMR）蛋白MLH1、MSH2、MSH6和PMS2在结直肠癌中的表达情况及其与患者临床病理特征之间的关系。方法收集中国医科大学附属盛京医院2016年1月至2017年1月间658例连续的结直肠癌病例,患者中男性409例,女性249例;年龄20-92岁,平均年龄（63±5）岁。采用免疫组织化学EnVision法检测结直肠癌组织中MLH1、MSH2、MSH6和PMS2蛋白表达缺失的情况,和MLH1蛋白表达缺失的结肠癌病例中的BRAF突变,分析MMR蛋白表达缺失与结直肠癌患者临床病理特征之间的关系。结果658例结直肠癌有44例（6．7％）发生MMR蛋白表达缺失,MLH1、MSH2、MSH6、PMS2蛋白表达缺失率分别为4．1％（27／658）、2．3％（15／658）、2．4％（16／658）、4．3％（28／658）。MMR蛋白表达缺失以MLH1与PMS2表达联合缺失（61．4％,27／44）、MSH2与MSH6表达联合缺失（34．1％,15／44）为主;PMS2和MSH6蛋白表达单独缺失的各有1例（2．3％,1／44）。进行BRAF V600E检测的27例MLH1蛋白缺失的病例中有7例（25．9％）为BRAF阳性,提示该7例患者可能存在因BRAF基因突变导致的MLH1蛋白表达缺失,属于散发型结直肠癌。结直肠癌组织中MMR蛋白表达缺失与肿瘤浸润深度、淋巴结转移、脉管癌栓、临床分期以及肿瘤血行转移无关（P〉0．05）,与更低程度的肿瘤组织分化、组织学类型和发病部位以及肿瘤浸润淋巴细胞数目增加显著相关（P〈0．01）：其中MLH1、PMS2蛋白表达缺失与组织学类型相关（P=0．049,P=0．013）,常伴黏液腺癌分化;MLH1、PMS2蛋白表达缺失多发生于右半结肠（P=0．006,P=0．002）;MSH2与MSH6蛋白表达缺失的患者发病年龄相对较小（P=0．014,P=0．023）;MSH2与PMS2蛋白表达缺失与性别相关,MSH2蛋白缺失多发生于女性（P=0．048）,PMS2蛋白表达缺失多发生于男性（P=0．031）。结论MMR蛋白缺失结直肠癌患者发病年龄低,组织分化程度低,发生部位多位于右半结肠,癌组织常伴有黏液腺癌分化。     

中国人家族性结直肠癌错配修复基因大片段变异分析

目的分析中国人家庭性结直肠癌错配修复基因大片段变异的特点。方法 采用多重连接探针扩增技术，分析32例具有家庭史结直肠癌、20例散发性结直肠癌患者错配修复基因MSH2的16个外显子、MLH1的19个外显子及7个其它基因外显子的拷贝数。研究工作包括：（1）双盲法分析阴性和阳性对照样本，完成方法学可靠性检验；（2）分析结直肠癌患者外周血细胞DNA，筛查MSH2和MLH1基因大片段变异。结果 多重连接探针扩增技术分析系统稳定检出阳性对照样本的DNA大片段缺失；在3/32（9.4%）具有家庭聚集性结直肠癌患者中检出遗传性MSH2基因DNA大片段缺失。而在20例散发性结直肠癌患者未检出这类突变。结论 中国人家族性结直肠癌患者中错配修复基因的大片段变异是频发事件，对此类患者的遗传检测应包含错配修复基因大片段变异的筛查。     

DNA错配修复基因MSH2和MLH1单核苷酸多态性与食管癌发生风险相关性研究

目的:探讨DNA错配修复基因MSH2和MLH1单核苷酸多态性对于食管癌易感性的潜在作用。方法:采用医院为基础的病例-对照研究方法,应用PCR-RFLP检测包括正常对照132例,食管癌患者169例MSH2c.2063TG和MLH1IVS14-19AG两个基因多态性位点的基因型。通过Logistic回归分析计算出比值比(OR)和95%置信区间(95%CI),估计不同基因型频率分布与食管癌发生风险的关系。结果:MSH2c.2063TG携带突变等位基因个体发生食管癌的风险是非携带者的3.24倍。MLH1IVS14-19AG突变等位基因携带者发生食管癌风险是非携带者的1.58倍。对MSH2和MLH1基因交互作用分析发现两突变基因型携带者发生食管癌风险大大增加并具有显著的统计学意义。结论:DNA错配修复基因MSH2c.2063G突变等位基因和MLH1IVS14-19G突变等位基因可能在促成食管癌发生过程起到一定作用。     

DNA错配修复基因MSH3和MSH6在肠道肿瘤发生中共同起着抑制作用

人类遗传性非息肉型结肠癌 ( HNPCC)是常染色体显性遗传疾病 ,HNPCC病人的肿瘤存在着DNA错配修复缺陷。近年来对错配修复基因MSH2、MLH1、PMS2研究的比较多 ,但对 MSH6和 MSH3的研究相对比较少。已有文章表明MSH6突变的小白鼠有肿瘤易感的表型 ,为研究MSH3的作用 ,作者设计了 MSH6和 MSH3突变的小白鼠 ,并核查它们的表现型。实验中作者发现 MSH3- /-的小白鼠的细胞提取物有能力修复单个核苷酸错配和单个核苷酸插入与缺失错配 ,但不能修复更大段的插入和缺失错配。而 MSH6- /-细胞提取物不能修复碱基错配 ,但能有效地修复…     

MLH1、MSH2、MSH6和PMS2蛋白在结直肠癌中的表达及在Lynch综合征筛查中的意义

目的探讨错配修复(mismatch repair,MMR)蛋白MLH1、MSH2、MSH6和PMS2在结直肠癌中的表达及其临床意义。方法采用免疫组化En Vision两步法检测102例结直肠癌组织中MLH1、MSH2、MSH6和PMS2蛋白表达缺失情况,分析蛋白表达缺失与结直肠癌临床病理特征的关系,并对其中20例进行微卫星不稳定(microsatellite instability,MSI)检测。结果 102例结直肠癌有15例(14.7%)发生MMR蛋白表达缺失,MLH1、MSH2、MSH6、PMS2蛋白表达缺失率分别为12.7%(13/102)、3.9%(4/102)、4.9%(5/102)、10.8%(11/102)。结直肠癌标本中MLH1、MSH2、MSH6、PMS2的蛋白表达缺失与患者性别、年龄、肿瘤大小、浸润深度、淋巴结转移无关(P0.05);MLH1与PMS2蛋白表达缺失与组织学分化高低相关(P0.05)。进行MSI检测的10例MMR蛋白缺失病例中有2例(2.0%)为高频微卫星不稳定(microsatellite instability-high,MSI-H),其余8例为微卫星稳定(microsatellite stability,MSS);另10例无MMR蛋白缺失的病例微卫星状态均为低频微卫星不稳定(microsatellite instability-low,MSI-L)/MSS。结论免疫组化检测MLH1、MSH2、MSH6和PMS2的缺失可以用于Lynch综合征的初筛,对结直肠癌患者行MMR免疫组化检测和MSI联合检测可提高Lynch综合征的诊断率。     

DNA错配修复基因甲基化在肝细胞癌发生发展中的作用

目的探讨DNA错配修复基因(MMR)hMLH1,hMSH2和hMSH3甲基化在肝细胞癌(HCC)发生发展中的作用。方法采用甲基化特异性聚合酶链反应(MSP)法对38例新鲜HCC组织,相应非肿瘤肝组织,2例正常的捐肝组织及6种肝癌细胞系的hMLH1,hMSH2和hMSH3基因启动子CpG岛甲基化进行检测;培养6种肝癌细胞系,MSP法检测加入5-aza-2‘-deoxycytidine前后hMSH2基因在HCC中的甲基化状态改变;逆转录．聚合酶链反应(RT-PCR)方法检测加入5-aza-2’-deoxycytidine前后hMSH2在肝癌细胞株中的mRNA表达改变。结果HCC标本中13．2％(5／38)发生了hMLH1启动子甲基化,68．4％(26／38)发生了hMSH2启动子甲基化;相应的非肿瘤肝组织中hMLH1,hMSH2启动子甲基化阳性率分别为2．6％(1／38),55．3％(21／38);2例正常肝组织中未发现甲基化;6株肝癌细胞系中有5株发生了hMSH2启动子甲基化,而未发现有MLH1启动子甲基化。所有标本中均未发现有hMSH3启动子甲基化。5-aza-2‘-deoxycytidine处理细胞株后,可部分或完全逆转hMSH2启动子甲基化,各细胞株的mRNA均有不同程度的表达增加。结论hMSH3基因启动子CpG岛甲基化与HCC的发生发展关系不大。hMSH2基因甲基化与mRNA表达密切相关,是基因表达调节的一种重要方式。hMLH1和hMSH2基因启动子CpG岛的高甲基化在HCC中是一个常见的基因改变,DNA错配修复基因尤其是hMSH2基因启动子甲基化在HCC的发生中起了重要作用,是早期事件,其可能为临床诊断HCC提供新的检测指标。     

CDH1基因启动子甲基化在上皮性卵巢癌转移方面的研究

目的探讨CDH1基因启动子甲基化对上皮性卵巢癌转移的影响。方法采用免疫组织化学方法检测38例正常卵巢上皮和80例上皮性卵巢癌组织中E-钙黏附素（E-cadherin）表达;应用甲基化特异的PCR（MSP）检测上述组织中CDH1基因启动子区甲基化;应用5-氮-2＇-脱氧胞苷（5-aza-CdR）使SKOV3细胞去甲基化,观察SKOV3细胞体外侵袭性的改变,并通过RT-PCR检测CDH1基因的改变。结果E-cadherin在正常卵巢组织中表达明显高于上皮性卵巢癌（P〈0．05）。34例CDH1基因启动子区甲基化全部出现在卵巢癌组织中,有淋巴结转移组织中甲基化明显高于无淋巴结转移者（P〈0．05）,而CDH1基因启动子区有甲基化的卵巢癌组织中E-cadherin表达明显降低（P〈0．05）。经5-Aza-CdR处理后的SKOV3细胞体外侵袭性降低（P〈0．01）,CDH1基因的表达明显上调（P〈0．01）。结论E-cadherin表达降低与上皮性卵巢癌转移关系密切,CDH1基因启动子区甲基化可能是导致E-cadherin蛋白表达减低的重要原因之一,因此启动子区甲基化与上皮性卵巢癌转移有关。     

DENV2感染外周血单个核细胞增加TNF-α基因启动子区域CpG位点的甲基化水平

 目的：检测正常人外周血单个核细胞（PBMC）感染2型登革病毒（DENV2）后肿瘤坏死因子α（TNF-α）基因启动子区域CpG位点的甲基化水平。
方法：采用亚硫酸氢盐测序PCR法检测DNA甲基化水平。结果：TNF-α基因启动子区域为-294 bp到+58 bp,覆盖11个散在CpG位点;PCR反应后取PCR产物进行琼脂糖凝胶电泳分析显示,扩增序列大小与理论预测相符合;PBMC感染DENV2 0 h和6 h 在11个甲基化位点中有2个处于甲基化状态,感染12 h有6个甲基化位点甲基化。0 h、6 h和12 h的平均甲基化率分别为103%、121%和255%,且0 h和12 h及6 h和12 h的甲基化率差异有统计学意义。结论：PBMC感染DENV2后会引起TNF-α基因启动子区域的甲基化水平增加。     

Redundant DNA methylation in colorectal cancers of Lynch-syndrome patients

Lynch syndrome is an inherited disease resulting predominantly in colorectal cancer (CRC). The crucial cause is DNA mismatch repair (MMR) malfunction that is associated mostly with MLH1 or MSH2 germline mutations. A significant hallmark of repair defects is a high level of instability in microsatellites (MSI-H). In many sporadic unstable CRCs, the MLH1 gene is inactivated by promoter hypermethylation in addition to extensive promoter methylation in many tumor-suppressor genes known as CpG island methylation phenotype (CIMP). To investigate the possible role of epigenetic alterations in causing MMR deficiency and thereby Lynch syndrome, we evaluated the MLH1 specific and global hypermethylation in hereditary CRCs. Of 22 Lynch-syndrome-related CRCs, 18 (81.8%) demonstrated various levels of DNA methylation; of these, 14 (63.6%) and 4 (18.2%) were methylated in distal and both distal and proximal regions of the MLH1 promoter, respectively. However, only 7/18 (38.9%) of results were confirmed by bisulfite sequencing. Similar methylation patterns in tumors and frequently in matched normal DNA were found in twelve and four patients with MLH1 and MSH2 alterations documented by the absence of protein or presence of germline mutation, respectively. Moreover, the same results were observed in five stable CRCs. None of 22 Lynch-syndrome-related tumors presented CIMP in contrast to 3/10 (30%) stable carcinomas. The rather randomly distributed weak methylation patterns in hereditary CRCs indicate that epigenetic events are redundant in Lynch-syndrome etiology, in contrast to the widespread DNA methylation in sporadic unstable CRCs. These methylation-profile differences can lead to more effective molecular diagnosis of Lynch syndrome.     

Relationship of mismatch repair proteins and survivin in colon polyps and carcinomas

Mismatch repair genes (MMR) play an essential role in DNA repair. MMR mutations predominantly in MLH1, MSH2, MSH6, PMS2, and rarely in PMS1, may cause the production of abnormally short or inactivated proteins. The antiapoptotic protein survivin functions in the inhibition of apoptosis, regulation of cell division and also enhances angiogenesis. Both MMRP and survivin are considered to be powerful prognostic parameters. This study was designed to determine the relationship between MMRP and survivin in colon lesions. The study included 113 cases of colon carcinoma and 51 cases of colon polyps. Survivin expression and MMRP status were assessed by immunohistochemistry. In each section, expression, intensity of immunostaining and percentage of labeled cells were analyzed. In carcinomas, immunoreaction was detected in 100/113 cases for MLH1 (88.5%), 112/113 cases for MSH2 (99.1%), 110/113 cases for MSH6 (97.3%), and 103/113 cases for PMS2 (91.2%). Survivin was shown in 47/113 cases (41.6%). The statistical analysis confirmed a significant correlation between the expression of MMRP and survivin in the assessed parameters. All 51 polyp samples were positive for MLH1, MSH2, MSH6 and PMS2. Only 8 of those (15.7%) were positive for survivin. Statistically significant differences were observed between the expression of MMRP and survivin. In conclusion, this study revealed that MMRP may suppress the antiapoptotic function of survivin through p53 inactivation of its promoter in grade 1 and grade 2 colon carcinomas.     

How and when to search for microsatellite instability in colorectal cancer in 2008?

Hereditary non polyposis colorectal cancer or Lynch syndrome is due to germline mutation of one the DNA mismatch repair genes. This mutation is associated with an unstable phenotype in tumor DNA characterized by new microsatellite alleles that are absent in matching normal DNA. Besides the Bethesda reference panel, a new panel of 5 mononucleotide microsatellites (BAT25, BAT26, NR21, NR24, NR27) has been proposed, which is more sensitive and faster to use in a multiplex PCR assay. In tumor cells, immunohistochemistry detects the loss of expression of either MLH1, MSH2, MSH6 or PMS2 protein, corresponding to the mutated gene. Immunohistochemistry guides germline analysis, except for MLH1 extinction which may correspond to either MLH1 germline mutation or methylation of MLH1 promoter resulting in inactivation. The latter is mostly due to aging and is often associated to the V600E BRAF gene mutation in tumor DNA. Combination of these 3 somatic analyses should reduce indications of germline mutation analysis in Lynch syndrome.     

Granular dot-like staining with MLH1 immunohistochemistry is a clone-dependent artefact

Immunohistochemistry (IHC) for DNA mismatch repair proteins MLH1, PMS2, MSH2, and MSH6 is used for microsatellite instability (MSI) screening in colorectal carcinoma (CRC) and endometrial carcinoma (EC). Loss of PMS2, with retained MLH1 staining occurs in germline mutations of PMS2 gene, and is an indication for genetic testing. We report a pitfall of immunohistochemical interpretation in an EC, initially regarded as MLH1-positive and PMS2-negative. Review of the MLH1-IHC (M1-clone) revealed a granular, dot-like, nuclear staining. On repeating the MLH1-IHC with a different clone (ES05-clone), complete negativity was noted, and on molecular testing, MLH1 promotor methylation was detected. The dot-like pattern was therefore adjudged a clone-dependent artefact. On reviewing the archived MLH1-IHC slides, we observed the same dot-like pattern in two CRCs; in both cases the M1-clone had been used. Awareness of this artefact may prevent reporting errors, and unnecessary referrals for germline mutation testing.     

PMS2 expression decrease causes severe problems in mismatch repair

PMS2 is one of the four susceptibility genes in Lynch syndrome (LS), the most common cancer syndrome in the world. Inherited mutations in DNA mismatch repair (MMR) genes, MLH1, MSH2, and MSH6, account for approximately 90% of LS, while a relatively small number of LS families segregate a PMS2 mutation. This and the low cancer penetrance in PMS2 families suggest that PMS2 is only a moderate or low‐risk susceptibility gene. We have previously shown that even a partial expression decrease in MLH1, MSH2, or MSH6 suggests that heterozygous LS mutation carriers have MMR malfunction in constitutive tissues. Whether and how PMS2 expression decrease affects the repair capability is not known. Here, we show that PMS2 knockdown cells retaining 19%, 33%, or 53% of PMS2 expression all have significantly reduced MMR efficiency. Surprisingly, the cells retaining expression levels comparable to PMS2 mutation carriers indicate the lowest repair efficiency.