脑胶质瘤患者组织和血清MGMT、hMLH1和hMSH2基因启动子甲基化状态检测

目的 探讨脑胶质瘤患者组织和血清中MGMT、hMLH1和hMSH2基因启动子CpG岛甲基化发生率及相关性.方法 甲基化特异性PCR(MSP)检测39例脑胶质瘤组织样本及32例预处理的脑胶质瘤血清样本中MGMT、hMLH1和hMSH2基因启动子区的甲基化状态.结果 脑胶质瘤组织MGMT、hMLH1和hMSH2基因启动子区甲基化发生率分别为46.2 %、10.3 % 和20.5 %,肿瘤组织中至少有一种基因甲基化的发生率为64.1 % (25/39);在脑胶质瘤患者外周循环血液中检测到了相关基因甲基化系列,并且与组织中基因甲基化发生率明显相关.结论 MGMT、hMLH1和hMSH2基因启动子甲基化是脑胶质瘤发生过程中常见的分子事件,血清中相关基因DNA甲基化检测有可能为脑胶质瘤诊断和个体化化疗提供一种稳定的无创性检测指标.     

乳腺癌发生过程中NOEY2基因启动子区甲基化及mRNA表达

目的 探讨乳腺癌发生过程中抑癌基因NOEY2启动子区甲基化状态及其对mRNA表达的影响。方法 应用甲基化特异性PCR及双亚硫酸钠基因测序技术检测MCF10模型中乳腺增生细胞系MCF10A、癌前细胞系MCF10AT、导管内癌细胞系MCFIODCIS．com、浸润癌细胞系MCF10CA1a、MCF10CA1d、MCF10CA1h及正常乳腺组织中NOEY2基因启动子区CpG岛Ⅰ甲基化状态,然后用RT-PCR和实时PCR技术检测上述样品的mRNA表达水平。结果 MCF10模型的增生细胞系、癌前细胞系、导管内癌细胞系、浸润癌细胞系均发生该基因启动子区CpG岛Ⅰ高度甲基化;与正常乳腺组织相比,上述细胞系mRNA表达显著减少。结论 NOEY2基因启动子区高度甲基化及相应的mRNA表达减少是乳腺癌发生过程中的早期事件,与乳腺癌发生有关,可能成为早期诊断乳腺癌的潜在分子生物学标记。     

5-aza-2dC诱导白血病细胞分化及对Annexin A1/A2表达和甲基化状态的影响

目的：观察甲基化转移酶抑制剂5-杂氮-2’-脱氧胞苷(5-aza-2’-deoxycitydine, 5-aza-2dC)对人急性髓系白血病细胞系HL-60细胞分化及对膜联蛋白A1/A2(Annexin A1/A2)表达和甲基化状态的影响。 方法：瑞氏染色和流式细胞术检测5-aza-2dC对HL-60细胞分化的影响;RT-PCR法检测药物处理HL-60细胞前后Annexin A1和A2基因mRNA的表达水平;甲基化特异性PCR(methylation-specific PCR,MSP)检测药物处理HL-60细胞前后Annexin A1和A2基因启动子区域CpG岛的甲基化水平。 结果：5-aza-2dC处理后HL-60细胞的髓系分化抗原CD11b的表达增强,细胞向成熟分化,且在0.5 μmol/L时其促分化作用最明显;Annexin A1和A2基因在HL-60细胞中低表达,0.5 μmol/L 5-aza-2dC处理HL-60细胞72 h后,Annexin A1和A2基因mRNA表达水平明显上调,而其启动子区域CpG岛甲基化水平明显降低。结论：5-aza-2dC具有促进白血病细胞分化的作用,Annexin A1和A2基因启动子去甲基化可能与5-aza-2dC诱导白血病细胞分化有关。     

胃癌中Cav-1的异常表达及其调控机制

目的：检测胃癌(gastric cancer, GC)细胞系及其组织标本中小凹蛋白-1(Cav-1)的表达,并探讨基因甲基化对Cav-1表达的影响。方法应用甲基化特异性PCR(methylation specific PCR, MSP)技术检测胃癌细胞株(AGS、MKN45、BGC-823)及104例胃癌及相应癌旁组织中Cav-1基因的甲基化状态,应用RT-PCR技术检测胃癌细胞株中Cav-1 mRNA的表达,应用免疫组化法检测胃癌组织中Cav-1的表达。结果甲基化抑制剂5-aza-2’-deoxycytidine(5-Aza-Dc)处理细胞株后,AGS中Cav-1 mRNA由阴性表达恢复为阳性表达,MKN45及BGC-823中Cav-1 mRNA在处理前后均呈阳性;用组蛋白去乙酰化酶抑制剂曲古抑菌素A( trichostatin A,TSA)分别处理3株细胞,处理前后Cav-1 mRNA表达均无明显变化。 MSP检测结果显示,AGS细胞株可扩增出甲基化条带,5-Aza-Dc处理后,甲基化条带消失,MKKN45及BGC-823处理前后均无甲基化条带扩出。胃癌组织中Cav-1基因甲基化率为29．8%(31/104),明显高于癌旁组织(P=0．000);癌组织中Cav-1基因高甲基化与患者淋巴结转移及上消化道肿瘤家族史(upper gastrointestinal cancers, UGIC)相关(P<0．05),与病理分级及临床分期无关(P>0．05);胃癌组织中Cav-1的阳性率为51．9%(54/104),明显低于癌旁组织,差异有统计学意义(P=0．000),且癌组织中Cav-1表达与其基因高甲基化状态明显相关(P=0．000)。结论 Cav-1在胃癌组织中表达下调,并且基因启动子区CpG岛的高甲基化状态可能是引起其表达下调的机制之一。     

雌激素受体α阴性乳腺癌雌激素受体α基因启动子区CpG岛甲基化和肼苯哒嗪去甲基化作用

目的 检测雌激素受体(ER)α阴性乳腺癌细胞株MDA-MB-231和MDA-MB-435细胞及ERα阴性乳腺癌组织中ERα基因启动子区CpG岛甲基化状态;探索肼苯哒嗪能否作为去甲基化药物恢复ERα基因表达。方法应用特异性聚合酶链反应(MSP)检测乳腺癌细胞株MDA-MB-231和MDA-MB-435细胞和20例ERα阴性乳腺癌组织ERα基因3个启动子区A、B、CpG岛甲基化情况,肼苯哒嗪处理上述两种乳腺癌细胞,逆转录(RT)-PCR检测不同启动子调控下ERα基因异型体(isoform)ERα-A、ERα-B、ERα-C mRNA和ERα基因公共编码区mRNA表达。结果MDA-MB-231和MDA-MB-435细胞启动子区ERα-A、ERα-B均存在CpG岛甲基化,ERα-C无甲基化,20例ERα阴性乳腺癌组织中,13例(65％)ERα-A、10例(50％)ERα-B CpG岛甲基化阳性。其中9例ERα-A、ERα-BCpG岛甲基化均阳性(45％),仅1例(5％)ERα-C存在CpG岛甲基化。肼苯哒嗪处理上述两种细胞后,检测到ERα-A、ERα-B mRNA和公共编码区mRNA表达。结论乳腺癌组织和细胞ERα基因表达沉默可能与ERα基因启动子区A、B甲基化有关,且肿瘤分期愈晚,甲基化程度愈高。肼苯哒嗪能作为去甲基化药物诱导ERα基因表达。     

宫颈鳞状细胞癌组织中hMSH2启动子甲基化及蛋白表达的研究

目的检测宫颈鳞癌组织中hMSH2启动子甲基化及蛋白表达，探讨hMSH2在宫颈鳞癌发生、发展中的作用。方法采用甲基化特异性PCR方法和免疫组织化学方法分别检测正常宫颈组织、宫颈鳞癌组织中hMSH2启动子甲基化状况及蛋白表达。结果正常组织中未见hMSH2启动子甲基化，其蛋白表达为阳性表达；宫颈鳞癌组织中可见启动子甲基化，蛋白表达也表现异常或缺失。结论错配修复基因的正常表达是保证基因稳定的重要因素，hMSH2启动子区域甲基化及蛋白表达缺失在宫颈鳞状细胞癌的发生、发展过程中起一定作用。     

结直肠癌中胰岛素样生长因子结合蛋白-相关蛋白1表达上调与其5′CpG岛低甲基化的相关性

目的 探讨胰岛素样生长因子结合蛋白-相关蛋白1(IGFBP-rP1)在结直肠癌中的表达改变并分析其与该基因5′CpG岛甲基化改变的关系.方法 采用半定量逆转录聚合酶链反应(RT-PCR)和甲基化特异性聚合酶链反应(MSP)检测46例结直肠癌组织和配对的正常黏膜中IGFBP-rP1基因的表达水平及5′CpG岛的甲基化状况,并通过T-A克隆、测序加以验证.不表达IGFBP-rP1基因的结肠癌细胞株LoVo和SW620经去甲基化药物5-氮-2′-脱氧胞苷(5-aza-2′-deoxycytidine,5-aza-dC)处理后,分别用RT-PCR和MSP检测IGFBP-rP1表达改变和甲基化状况.结果 mRNA水平上,IGFBP-rP1在结直肠癌组织中的表达水平高于配对的正常黏膜(P<0.01).在46例结直肠癌组织中,28例(60.9%)可检测到IGFBP-rP1基因5′CpG岛发生甲基化,而在配对的正常黏膜中,37例(80.4%)可检测到,二者差异有统计学意义(P<0.05).IGFBP-rP1基因的表达和甲基化水平之间存在负相关(P<0.05).5-aza-dC处理后,两株细胞均出现IGFBP-rP1基因的再表达,MSP法检测证实基因发生了去甲基化.结论 IGFBP-rP1基因的表达水平与5′CpG岛甲基化水平之间存在负相关.DNA甲基化是结直肠癌中IGFBP-rP1表达调控的一种机制.IGFBP-rP1低甲基化引起的基因表达上调可能与结直肠癌的发生发展有关.     

126例子宫内膜癌中Lynch综合征的初步筛查

目的探讨hMSH2、hMSH6、hMLH1、hPMS2蛋白缺失情况和hMLH1基因启动子甲基化状态及Lynch综合征患者的家系分析,初步进行Lynch综合征相关子宫内膜癌筛查。方法采用免疫组化SP法检测126例子宫内膜癌中hMSH2、hMSH6、hMLH1、hPMS2蛋白表达,并用甲基化特异性PCR检测hMLH1蛋白表达缺失病例的hMLH1基因启动子甲基化状态。结果免疫组化结果显示22%(28/126)的病例出现MMR蛋白缺失表达,其中12例hMLH1~-/hPMS2~-、6例hPMS2~-、4例hMSH2~-/hMSH6~-,hMSH6~-和hMLH1~-各3例,以hMLH1和hPMS2蛋白缺失表达为主。甲基化特异性PCR检测有hMLH1蛋白表达缺失的15例子宫内膜癌中hMLH1基因启动子甲基化状态,证实9例存在hMLH1基因启动子甲基化,提示其为子宫内膜癌的散发性病例。结论对子宫内膜癌患者行MMR蛋白免疫组化SP法染色,结合甲基化特异性PCR检测hMLH1基因启动子甲基化状态,是初步筛查Lynch综合征的有效策略。     

散发性乳腺癌及乳腺不典型导管增生组织BRCA1基因启动子区甲基化分析

目的 了解散发性乳腺癌及癌旁增生组织、乳腺不典型导管增生组织BRCA1基因启动子区甲基化状态,探讨其与乳腺癌发生的关系.方法 采用甲基化特异性PCR(MSP)结合巢式PCR技术,研究23例散发性乳腺癌及其癌旁增生组织、6例乳腺不典型导管增生组织及5例健康成人女性外周血淋巴细胞中BRCA1基因启动子区甲基化状态.结果 5例健康成人女性外周血淋巴细胞均表现BRCA1基因启动子区甲基化阴性;23例原发性乳腺癌组织中,BRCA1基因启动子区CpG岛甲基化率为65.22%(15/23);癌旁增生组织检出CpG岛甲基化者11例,甲基化率为47.83%(11/23),且均为癌组织阳性患者;6例乳腺不典型导管增生组织中,BRCA1基因启动子区CpG岛甲基化阳性者2例,甲基化率为33.33%(2/6);统计学检验结果表明,乳腺癌、癌旁增生组织之间,BRCA1基因启动子区甲基化阳性率无显著差异.结论 BRCA1基因启动子区CpG 岛甲基化是散发性乳腺癌发生过程中的早期事件,可能在乳腺癌发生中和乳腺增生病癌变过程中起重要生物学作用.     

肝癌细胞中HLA I类重链基因表达与启动子区域甲基化的相关性

目的:研究肝癌细胞株中DNA甲基化与HLAI类分子异常表达的相关性。方法:应用MSP技术对相关细胞系的HLA I类分子重链A、B、C位点启动子区域CpG岛的甲基化状态进行分析,Real-time PCR检测HLAI类分子重链mRNA水平的表达情况,Western blot检测RNA干扰后HLAI类分子重链表达情况。结果:在8株肝癌细胞系中HLA I类分子重链A、C位点启动子区域CpG岛存在甲基化;将启动子区域的DNA甲基化与相关基因表达数据相比较显示二者没有关联性;在RNA干扰DNA甲基化转移酶3a或3b的肝癌细胞系SMMC7721中,比较基因干扰前后HLA I类分子重链蛋白表达无显著变化。结论:在研究的肝癌细胞系中DNA甲基化没有参与调控肝癌中HLA I类分子的异常表达。     

Alterations of DNA mismatch repair proteins and microsatellite instability levels in gastric cancer cell lines

Alterations in DNA mismatch repair (MMR) proteins result in microsatellite instability (MSI), increased mutation accumulation at target genes and cancer development. About one-third of gastric cancers display high-level microsatellite instability (MSI-High) and low-level microsatellite instability (MSI-Low) is frequently detected. To determine whether variations in the levels of MMR proteins or mutations in the main DNA MMR genes are associated with MSI-Low and MSI-High in gastric cancer cell lines, the MSI status (MSI-High, MSI-Low or MS-Stable (MSS)) of 14 gastric cancer lines was determined using multiple clone analysis with a panel of five microsatellite markers. Protein levels of hMLH1, hMSH2, hMSH6, hPMS2 and hPMS1 were determined by Western blot. Sequence analysis of hMLH1 and hMSH2 was performed and the methylation status of the hMLH1 promoter was examined. The cell lines SNU1 and SNU638 showed MSI-High, decreased to essentially absent hMLH1 and hPMS2 and reduced hPMS1 and hMSH6 protein levels. The hMLH1 promoter region was hypermethylated in SNU638 cells. The MKN28, MKN87, KATOIII and SNU601 cell lines showed MSI-Low. The MMR protein levels of cells with MSI-Low status was similar to the levels detected in MSS cells. A marked decrease in the expression levels of MutL MMR proteins (hMLH1, hPMS2 and hPMS1) is associated with high levels of MSI mutations in gastric cancer cells. Gastric cancer cell lines with MSI-Low status do not show significant changes in the levels of the main DNA MMR proteins or mutations in the DNA mismatch repair genes hMSH2 and hMLH1. These well-characterized gastric cancer cell lines are a valuable resource to further our understanding of DNA MMR deficiency in cancer development, progression and prognosis.     

Immunohistochemical expression of mismatch repair genes (hMSH2 and hMLH1) in hepatocellular carcinoma in Egypt

Egypt has the highest prevalence rate of hepatitis C virus (HCV) infection in the world. HCV contributes to the development of about 70% of hepatocellular carcinoma (HCC) cases. Understanding the molecular basis of hepatocarcinogenesis is important for planning the therapeutic regimen for HCC patients. To clarify the possible role of mismatch repair (MMR) genes in HCV-related HCC, we studied 50 HCV-related HCC specimens (28 of which were with adjacent non-cancerous cirrhotic liver tissue, ANCLT) and 30 specimens of chronic liver disease (CLD) with no evidence of HCC. All cases were examined immunohistochemically to demonstrate the protein expression of hMSH2 and hMLH1. Thirty-two (64%) and 35 (70%) of the HCC cases revealed reduced expression of hMSH2 and hMLH1, respectively. Reduced expression of both the proteins was obtained in 26 (52%) of the HCC cases. The expression of hMSH2 and hMLH1 was reduced in 53.6% and 64.3% of ANCLT cases, respectively, with no significant difference between HCC and ANCLT. All 30 specimens of CLD had preserved expression of hMSH2 and hMLH1. Multivariate analysis showed that the reduced expression of hMSH2 or hMLH1 was significantly associated with higher grades of the tumor (p = 0.002 and 0.02, respectively).The relationships of these MMR genes with other clinicopathologic factors were not significant. Reduced expression of hMSH2 and hMLH1 in both HCC and ANCLT suggests that this event occurs at early stages of HCV-related hepatocarcinogenesis. Moreover, the significant association between reduced expression of both MMR genes and poor histologic grades of the tumor claims that these proteins are involved in the process of cancer progression.     

Correlation of methylation of the hMLH1 promoter with lack of expression of hMLH1 in sporadic gastric carcinomas with replication error.

Recent studies have demonstrated that the majority of sporadic colorectal carcinomas with replication error (RER) do not harbor mutations of the hMLH1 and hMSH2 genes that account for about 70% of hereditary nonpolyposis colon cancer. Despite the absence of mutations of the hMLH1 gene, the majority of RER-positive sporadic colorectal carcinomas lack hMLH1 protein expression, which have been reported to be related to hypermethylation of the promoter region of hMLH1 gene. High frequency of microsatellite instability (MSI) has been observed in about 15% of sporadic gastric carcinomas. The relationship of tumor MSI, methylation of promoter regions of hMLH1 or hMSH2, and expression of corresponding gene products has not been studied in gastric carcinomas as thoroughly as in colorectal carcinomas. We explored the relationship between methylation of hMLH1 or hMSH2 promoter regions and its protein expression in both RER-positive and RER-negative gastric carcinomas. Of 93 cases, 20 cases comprised the RER+ group (MSI-H tumors) and the remainder comprised the RER- group (7 cases, MSI-L; 66 cases, MSS). By immunohistochemistry absence of hMLH1 protein expression was limited entirely to the RER+ group (20 of 20, 100%). All 93 cases showed hMSH2 protein expression. Nineteen (95%) of 20 RER+ tumors harbored hypermethylation of the hMLH1 promoter region whereas only four cases (5.5%) of the 73 RER- tumors did. Hypermethylation of the hMSH2 promoter region was not observed in either the RER+ group or the RER- group. These results suggest that hypermethylation of the hMLH1 promoter region may be the principal mechanism of gene inactivation in sporadic gastric carcinomas with a high frequency of MSI.     

hMLH1 Promoter Hypermethylation Is an Early Event in Human Endometrial Tumorigenesis

It has recently been suggested that silencing of the hMLH1 gene by promoter hypermethylation is the mechanism underlying the presence of the microsatellite instability (MSI) phenotype in sporadic colon and endometrial carcinomas. To determine whether hMLH1 promoter hypermethylation is a relatively early event in endometrial tumorigenesis we evaluated endometrial hyperplasia (EH) characterized as simple, complex, and atypical (the direct precursor of endometrial carcinoma) for hMLH1 aberrant methylation. In addition, we studied the hMLH1, hMSH2, hMSH3, and hMSH6 promoter methylation and MSI status of those endometrial carcinomas with synchronous hyperplasias and those without them. We found that 11 of 12 (91%) cases of endometrial carcinoma (EC) displaying MSI had hMLH1 promoter hypermethylation, whereas aberrant methylation of any of the other mismatch repair genes was not observed. All 15 cases of EC without MSI were unmethylated at hMLH1. Abnormal methylation of hMLH1 was also present in 8 of 116 (7%) cases of EH and was restricted primarily to the atypical endometrial hyperplasia (AEH) type with coexisting endometrial carcinoma. In this set, half of EH methylated at hMLH1 displayed MSI, whereas none of the unmethylated EH had MSI. Our data suggest that hypermethylation of hMLH1 can be an early event in the pathogenesis of EC, preceding the development of an apparent MSI phenotype in a subset of cases.     

Immunohistochemical detection of hMLH1 and hMSH2 proteins in vulvar carcinoma

The immunohistochemical (IHC) detection of MMR proteins is an accurate and rapid method to predict the presence of defective DNA MMR genes. MMR protein expression could also serve as a prognostic indicator of human cancers. The results of many studies demonstrate the usefulness of IHC tests with monoclonal antibodies MSH2 and MLH1 in screening the microsatellite sequence instability within both spontaneous and hereditary malignant neoplasms. The aim of our study was to perform an IHC estimation of the hMLH1 and hMSH2 expression in a subset of vulvar carcinomas according to HPV 16/18 status. The level of MMR proteins was further analyzed in relation to histoclinical features of the disease in either HPV-positive or -negative cancers. We identified archival diagnostic phase tissue specimens from 46 cases of vulvar cancer. From the same paraffin blocks containing material from the margin of surgical section during vulvectomy, normal epithelial tissue fragments were collected and designated as the control group. The characteristic of the lesion was examined in comparison with the presence of HPV DNA. Identification of the HPV 16/18 types was performed using PCR. IgG1 monoclonal antibodies detecting those epitopes characteristic for hMLH1 and hMSH2 were used in the study. In the analyzed cases of vulvar cancer, we have observed increased expression of proteins of both hMSH2 and hMLH1 genes compared to the control group. A comparison of the hMLH1 and hMSH2 protein expression levels showed that hMSH2 expression was higher than that of hMLH1 in the case of vulvar carcinomas. The performed analysis of correlation between individual parameters did not reveal statistically significant relationship with both the gradient and status of HPV 16/18. hMSH2 and hMLH1 were definitely interrelated.     

Reduced expression of hMLH1 and hMSH2 gene products in high-grade hepatocellular carcinoma

We performed an immunohistochemical analysis of 2 major DNA mismatch repair proteins, human Mut L homologue-1 (hMLH1) and human Mut S homologue-2 (hMSH2), in hepatocellular carcinoma (HCC) using 33 biopsied and 58 surgically resected specimens, as well as 30 samples from non-cancerous livers. In well-differentiated HCCs, the immunoreactivity for these antigens was well preserved, and the staining intensity was stronger compared to the surrounding liver tissues. However, among 41 moderately-differentiated and 9 poorly-differentiated HCCs of the resected cases, hMLH1- and hMSH2-positive cells were significantly reduced in 19 (38%) and 9 (18%) cases, respectively. In 9 resected tumors, the expression of both of these antigens was reduced. Moreover, in 41 tumors of differing histological grades, 10 and 5 tumors for hMLH1 and hMSH2, respectively, contained a less-differentiated area with a reduced number of immunoreactive cells. The samples from non-cancerous biopsied liver and fetal autopsy tissue were well immunostained for both hMLH1 and hMSH2. We confirmed in this series that the hMLH1 and hMSH2 defect did commonly occur in high-grade HCCs, and that it might play a role in tumor progression.     

Pharmacological unmasking microarray approach-based discovery of novel DNA methylation markers for hepatocellular carcinoma

DNA methylation is one of the main epigenetic mechanisms and hypermethylation of CpG islands at tumor suppressor genes switches off these genes. To find novel DNA methylation markers in hepatocellular carcinoma (HCC), we performed pharmacological unmasking (treatment with 5-aza-2'-deoxycytidine or trichostatin A) followed by microarray analysis in HCC cell lines. Of the 239 promoter CpG island loci hypermethylated in HCC cell lines (as revealed by methylation-specific PCR), 221 loci were found to be hypermethylated in HCC or nonneoplastic liver tissues. Thirty-three loci showed a 20% higher methylation frequency in tumors than in adjacent nonneoplastic tissues. Correlation of individual cancer-related methylation markers with clinicopathological features of HCC patients (n = 95) revealed that the number of hypermethylated genes in HCC tumors was higher in older than in younger patients. Univariate and multivariate survival analysis revealed that the HIST1H2AE methylation status is closely correlated with the patient's overall survival (P = 0.022 and P = 0.010, respectively). In conclusion, we identified 221 novel DNA methylation markers for HCC. One promising prognostic marker, HIST1H2AE, should be further validated in the prognostication of HCC patients.     

启动子DNA甲基化调节胃癌中PDX1基因表达

目的明确PDXl启动子DNA甲基化,探讨启动子甲基化对PDXl在胃癌中表达的调节作用。方法收集3例胃癌活检组织,免疫组化检测PDXl蛋白表达：吉西他滨处理3株胃癌细胞,RT—PCR检测不同药物剂量和作用时间下PDXlmRNA表达;构建PDXl报告基因,检测启动子活性及吉西他滨处理前后启动子活性的变化;甲基化特异性PCR（MSP）检测3株胃癌细胞和8对配对胃癌组织中PDXl启动子甲基化状态。结果免疫组化结果显示胃癌中PDXl表达低于正常胃黏膜;RT—PCR显示吉西他滨使PDXlmRNA重获表达,且随剂量和时间依赖性。F383有最强启动子活性,吉西他滨显著增加了PDXl启动子活性（P〈0．05）。F383在AGS、BCG823、SGC7901中呈DNA完全甲基化状态;87．5％的胃癌组织出现F383部分甲基化,12．5％出现完全甲基化。癌旁正常组织仅有37．5％出现F383部分甲基化,未出现完全甲基化,两者比较有显著性差异（P〈0．05）。结论PDXl启动子存在DNA高甲基化,抑制了胃癌中PDXl的表达。     

散发性结直肠癌hMLH1和hMSH2蛋白表达

目的　研究hMLH1及hMSH2两种错配修复 (mismatchrepair,MMR)蛋白在散发性结直肠癌中的表达变化并评估其可能的临床意义。方法　应用EnVision免疫组化两步法检测 1 1 1例散发性结直肠癌中hMLH1和hMSH2的蛋白表达变化 ,采用Kaplan Meier曲线、Log rank检验分析hMLH1蛋白表达变化与患者生存率之间的关系。 结果　 1 1 1例散发性结直肠癌中 ,hMLH1失表达有 1 9例 ,占 1 7 1 % (1 9/ 1 1 1 ) ,hMSH2失表达有 2例 ,占 1 8% (2 / 1 1 1 ) ,两者之和占总散发性结直肠癌病例的 1 8 9% (2 1 / 1 1 1 )。hMLH1或hMSH2蛋白失表达与患者肿瘤部位、组织学类型密切相关。近端结肠、低 -未分化腺癌及黏液腺癌中MMR异常表达比例高 (P <0 0 5 ) ,而与患者年龄、性别、肿瘤大体类型、肿块大小、浸润深度、淋巴结转移与否以及患者的Dukes分期均无显著性相关 (P >0 0 5 )。癌组织中hMLH1正常表达及失表达患者的 5年生存率分别为 6 9 5 7%及73 6 8% ,8年生存率分别为 5 3 5 8%及 73 6 8% ,8年生存率差别较明显 ,然差别无统计学显著性 (P >0 0 5 )。结论　一定比例的散发性结直肠癌中存在MMR基因的缺陷 ,其中hMLH1所起的作用远远大于hMSH2 ,hMLH1失表达与否可能成为有意义的远期生存预后指标