实时荧光定量PCR和甲基化特异性PCR检测结直肠癌APC、MLH1基因甲基化状态

背景：启动子区甲基化致肿瘤抑制基因失活在结直肠癌的发生、发展中起重要作用,检测肿瘤相关基因的甲基化状态,可能为寻找新的结直肠癌诊断、预后相关标记物提供依据.目的：比较实时荧光定量PCR（FO-PCR）与甲基化特异性PCR（MSP）检测基因甲基化状态的差异.方法：以FQ-PCR检测66例结直肠癌组织和20例癌旁组织中与结直肠癌的发生、发展相关的抑癌基因APC和错配修复基因MLH1的甲基化状态,同时以MSP检测结直肠癌组织中APC基因的甲基化状态.结果：根据FQ-PCR结果,结直肠癌组织中APC、MLH1基因甲基化阳性率显著高于癌旁组织（48.5%和54.5%对0%和0%,P=0.000）.FQ-PCR和MSP可检出的甲基化阳性对照DNA最低浓度分别为0.015 ng/μl和1.5 ng/μl,两者对APC基因甲基化状态的检测结果差异有统计学意义（P＜0.05）.结论：在DNA甲基化的检测手段中,FQ-PCR的敏感度优于MSP.     

胃癌患者血清RASSF1A基因启动子区甲基化检测

Ras相关结构域家族1A（RASSF1A）基因是近年发现的新型抑癌基因，其启动子区甲基化可能与胃肠道肿瘤的发生、发展密切相关。目的：检测胃癌患者血清RASSF1A基因启动子区甲基化情况，探讨其在胃癌早期诊断和预后评估中的可能作用。方法：以甲基化特异性聚合酶链反应（MSP）检测47例胃腺癌患者、30例胃良性病变患者和30名健康对照者的血清RASSF1A基因启动子区甲基化情况，其中16例胃腺癌患者同时留取手术切除癌组织、癌旁组织标本以及术前、术后血标本行对照研究。结果：胃腺癌患者血清RASSF1A基因启动子区甲基化率为34．0％（16／47），显著高于胃良性病变患者（3.3％，1／30）和健康对照者（0％）（P〈0．01）。16例胃腺癌组织中5例（31．2％）检测到RASSF1A基因启动子区甲基化，其中4例（80．0％）术前、术后血清标本均检测到RASSF1A基因启动子区甲基化。血清RASSF1A基因启动子区甲基化与胃癌患者性别、年龄、肿瘤分化程度、有无转移以及血清癌胚抗原（CEA）水平均无相关性。结论：血清RASSF1A基因启动子区甲基化检测可望为胃癌的早期诊断和预后判断提供依据。     

结肠癌中心和边缘组织增殖能力的差异及相关基因的表达

目的探索结肠癌组织不同区域肿瘤细胞是否存在增殖能力的差异，且这种区域性差异和多重抑痛基因p16及其可变读码框架pl4基因的表达情况及其甲基化状态的相关性。方法免疫组化法测定癌块不同区域增殖蛋自Ki67和P16、P14的表达差异，激光显微切割技术结合甲基化特异性PCR、巢式逆转录PCR观察同一癌块不同区域癌细胞p16及p14基因甲基化状态的改变及其mRNA的表达情况。结果在42份癌组织标本的中心，增殖蛋自Ki67均呈强阳性表达，而P16和P14蛋白表达缺失；在癌组织标本的边缘．有13份Ki67表达阳性（30．1％）。不同区域癌细胞的增殖能力差异有统计学意义（P〈0．05）．且与年龄、性别、Dukes分期、p14的表达无关，但与p16的表达显著相关（X^2=25．37，P〈0．01）。且p16基因的甲基化状态和mRNA的表达也存在明冠的区域性差异（P〈0．05）。结论人结肠癌组织中存在肿瘤细胞增殖能力的区域性差异，在癌组织边缘肿瘤细胞侵袭力增强的同时增殖能力下降，癌边缘区P16基因去甲基化后的再表达可能是这一细胞事件的分子原因。     

质子泵抑制剂治疗对Barrett食管APC基因启动子区甲基化的影响

背景：Barrett食管（BE）是食管腺癌的癌前病变,与食管腺癌的发生密切相关,已成为近年来的研究热点。目的：观察质子泵抑制剂（PPI）埃索美拉唑对BE患者抑癌基因APC表达及其启动子区甲基化的影响。方法：以甲基化特异性聚合酶链反应（PCR）和实时荧光定量PCR观察69例BE患者APC基因启动子区甲基化阳性率和APCmRNA表达在埃索美拉唑治疗前后的变化。分析治疗前APC基因启动子区甲基化状态与BE临床病理特征的关系。结果：埃索美拉唑治疗前,APC基因启动子区甲基化阳性率显著高于治疗后（42．0％对17．4％,P=0．007）。治疗前．长段BE的APC甲基化阳性率显著高于短段BE（46．8％对31．8％,P=0．032）;内镜下食管炎洛杉矶分类A级和B级者的APC甲基化阳性率显著低于C级和D级（19．0％对52．1％,P=0．046）;Ⅰ、Ⅱ、Ⅲ型BE间APC甲基化阳性率无明显差异（P=0．061）。埃索美拉唑治疗后,BE上皮APCmRNA表达量较治疗前显著增加（19．5±0．4对6．5±2．3,P=0．000）。结论：埃索美拉唑可抑制BE患者APC基因启动子区甲基化,增加抑癌基因APC表达。     

DNA甲基转移酶1蛋白在人胃癌黏膜组织中的表达及其临床意义

背景：肿瘤组织存在DNA甲基化紊乱．包括与细胞增殖周期密切相关的癌基因低甲基化和抑癌基因高甲基化等。DNA甲基转移酶（Dnmt）参与甲基化的形成（主要是Dnmt3a和Dnmt3b）和维持（主要是Dnmt1），但目前对胃癌Dnmt蛋白的表达情况仍知之甚少，更缺乏其与肿瘤生物学行为和临床参数关系的研究。目的：探讨癌区、癌旁和外周正常黏膜组织中Dnmt1蛋白表达的差异及其临床意义。方法：收集38例胃癌患者标本，取癌区、癌旁和外周正常黏膜组织各1．2块，应用免疫组化SP法分析各黏膜组织中Dnmt1蛋白的表达．并探讨其与胃癌浸润和转移的关系。结果：在38例胃癌黏膜组织中，Dnmt1蛋白的表达阳性率为81．6％，显著高于相应癌旁（39．5％）和正常黏膜组织（10．5％）（P〈0．001）。阳性切片中可见Dnmt1蛋白表达弥散分布于肿瘤或腺体的细胞质和细胞核，染色较均匀。Dnmt1蛋白表达与胃癌患者的年龄、肿瘤分化程度和有无淋巴结转移无明显相关性（P〉0．05），与性别呈一定的相关性（P=0．007）。结论：Dnmtl蛋白过表达在人胃癌的发生和发展中起一定作用。     

胃癌3号染色体短臂抑癌基因CpG岛甲基化表型研究

背景:3号染色体短臂(3p)抑癌基因CpG岛甲基化表型(CIMP)涉及的甲基化异常见于多种类型的癌症中,但与胃癌的关系迄今仍未阐明。目的:研究胃癌中3p抑癌基因启动子区CIMP的临床意义。方法:采用甲基化特异性PCR(MSP)法检测100例胃癌组织及其对应癌旁组织中hOGG1、VHL、RAR-B、hMLH1、SEMA3B、RASSF1A、BLU和FHIT共8个抑癌基因启动子区CpG岛甲基化状态。以每份样本中含有4个及以上甲基化基因定义为高CIMP水平(CIMP-H)。分析CIMP-H与胃癌临床病理特征的关系。结果:胃癌组织中VHL(P=0.030)、hMLH1(P0.001)、SEMA3B(P=0.003)、RASSF1A(P0.001)和FHIT(P0.001)基因甲基化阳性率显著高于癌旁组织。胃癌组织和对应癌旁组织中CIMP-H发生率分别为44.0%和4.0%,差异有统计学意义(P0.001)。胃癌组织CIMP-H与肿瘤分化程度呈显著负相关(P=0.004),与淋巴结转移呈显著正相关(P=0.005),而与性别、年龄、肿瘤部位、肿瘤直径、浸润深度和TNM分期均无关(P0.05)。结论:3p CIMP异常状态可能在胃癌形成早期已发生,并影响肿瘤分化,导致淋巴结转移。     

多基因甲基化的检测在肝癌早期诊断中的价值

目的检测肝癌患者癌组织中p14、p15、p16、RB基因启动子异常甲基化状况,探讨其在肝癌诊断中的价值。方法采用甲基化特异性PCR（MSP）方法检测44例肝癌组织及其相对应41例肝硬化组织、44例癌旁组织中p14、p15、p16、RB的甲基化状况。对所得结果进行卡方检验,Fisher精准概率分析。结果肝硬化组织中p14、p15、p16、RB 4种基因的甲基化检出率分别为17.1%（7/41）、28.9%（11/41）、36.6%（15/41）和7.3%（3/41）;肝癌组织中4种基因的甲基化检出率分别为34.1%（15/44）,56.8%（25/44）,70.5%（31/44）和27.3%（12/44）。癌旁组织中检测出p16甲基化阳性产物4例,p15阳性产物1例。癌组织和肝硬化组织中4种基因的甲基化率明显高于癌旁组织（P〈0.05）;不同年龄、性别、肿瘤分化程度和临床分期的肝癌患者各个基因甲基化率没有明显差异。结论 p14、p15、p16、RB基因甲基化在肝癌中频发;多基因甲基化的联合检测在肝癌的早期诊断中有一定的价值。     

乳腺癌组织中p16基因甲基化与p16、ER蛋白表达的相关性及意义

目的探讨p16基因甲基化在乳腺癌发生、发展中的作用。方法应用甲基化特异性PCR（MSP）联合测序检测58份乳腺癌及其癌旁组织中p16基因甲基化状态,应用免疫组化sP法检测p16及ER蛋白表达情况,对各指标间关系行Spearman相关分析。结果p16基因在乳腺癌中甲基化率为29,3％（17／58）,有淋巴结及远处转移者显著高于无转移者（P〈0．05）;p16甲基化及非甲基化者p16蛋白表达阻性（失表达）率分别为82．4％（14／17）、43．9％（18／41）,ER蛋白失表达率分别为76．5％（13／17）、24．4％（10／41）,P均〈0．05。结论p16基因甲基化在乳腺癌发生、发展中具有重要作用,机制可能与调节p16和ER蛋白表达有关。     

胃癌p16基因启动子异常甲基化的临床意义

目的 观察胃癌组织中p16基因启动子区异常甲基化状态,并探讨其甲基化改变与临床特征的关系.方法 采用甲基化特异的聚合酶链反应检测胃癌组织及相应癌旁正常组织中p16基因启动子区甲基化状态.结果 胃癌组织p16基因的异常甲基化率显著高于相应的癌旁正常组织(P＜0.01).胃癌组织中该基因的异常甲基化与患者年龄、性别、肿瘤大小、病理分期、组织分化程度、肿瘤浸润深度及淋巴结转移等临床特征无显著相关性.结论 p16基因启动子区的异常甲基化是胃癌发生发展中的频繁事件,在胃癌的发生中具有肿瘤特异性.     

APC基因异常甲基化在上皮性卵巢癌中的检测及临床意义

目的探讨结肠腺瘤性息、肉病基因（APC）异常甲基化在上皮性卵巢癌发生、发展中的作用及临床意义。方法采用甲基化特异性PCR法检测63例上皮性卵巢癌组织原发灶、41例相应的盆腹腔转移灶、10例癌旁卵巢组织及20例正常卵巢组织中APC基因启动子区甲基化状态。结果上皮性卵巢癌组织原发灶及相应的盆腹腔转移灶中APC基因启动子区异常甲基化发生率分别显著高于正常卵巢组织（P〈0．05）。APC基因启动子区甲基化与上皮性卵巢癌临床分期、分化程度及病理类型无关。结论APC基因启动子区异常甲基化与上皮性卵巢癌发生、发展密切相关。     

Germline promoter hypermethylation of tumor suppressor genes in gastric cancer

AIM: To explore germline hypermethylation of the tumor suppressor genes MLH1, CDH1 and P16^INK4a in suspected cases of hereditary gastric cancer (GC).METHODS: A group of 140 Chinese GC patients in whom the primary cancer had developed before the age of 60 or who had a familial history of cancer were screened for germline hypermethylation of the MLH1, CDH1 and P16^INK4a tumor suppressor genes. Genomic DNA was extracted from peripheral blood leukocytes and modified by sodium bisulfite. The treated DNA was then subjected to bisulfite DNA sequencing for a specific region of the MLH1 promoter. The methylation status of CDH1 or P16^INK4a was assayed using methylation-specific PCR. Clonal bisulfite allelic sequencing in positive samples was performed to obtain a comprehensive analysis of the CpG island methylation status of these promoter regions.RESULTS: Methylation of the MLH1 gene promoter was detected in the peripheral blood DNA of only 1/140 (0.7%) of the GC patient group. However, this methylation pattern was mosaic rather than the allelic pattern which has previously been reported for MLH1 in hereditary non-polyposis colorectal cancer (HNPCC) patients. We found that 10% of the MLH1 alleles in the peripheral blood DNA of this patient were methylated, consistent with 20% of cells having one methylated allele. No germline promoter methylation of the CDH1 or P16^INK4a genes was detected.CONCLUSION: Mosaic germline epimutation of the MLH1 gene is present in suspected hereditary GC patients in China but at a very low level. Germline epimutation of the CDH1 or P16^INK4a gene is not a frequent event.     

Downregulation of retinoic acid receptor-β2expression is linked to aberrant methylation in esophageal squamous cell carcinoma cell lines

AIM: To study the role of hypermethylation in the loss ofretinoic acid receptorβ2(RARβ2) in esophageal squamous cell carcinoma (ESCC).METHODS: The role of hypermethylation in RAR,β2 gene silencing in 6 ESCC cell lines was determined by methylationspecific PCR (MSP), and its methylation status was compared with RARβ2 mRNA expression by RT-PCR. The MSP results were confirmed by bisulfite sequencing of RARβ2promoter regions. RESULTS: Methylation was detected in 4 of the 6 cell lines, and the expression of RARβ2was markedly downregulated in 3 of the 4 methylated cell lines. The expression of RARβ2was restored in one RARβ2-downregulated cell line with the partial demethylation of promoter region of RARβ after 5aza-2'-deoxycytidine (5-aza-dc) treatment.CONCLUSION: The methylation of the 5' region may play an important role in the downregulation of RARβ2 in someESCC cell lines, suggesting that multiple mechanisms contribute to the loss of RARβ2expression in ESCC cell lines. This study may have clinical applications for treatment and prevention of ESCC.     

RASSF1A gene promoter methylation in esophageal cancer specimens

SUMMARY. RASSF1A is frequently inactivated by promoter methylation in human cancers. To understand the involvement of the RASSF1A gene in esophageal squamous cell cancer (ESCC), we investigated the methylation of the RASSF1A gene in primary ESCC to define the frequency of this epigenetic aberration and its clinicopathological significance. Methylation-specific polymerase chain reaction (MSP) was used to detect RASSF1A gene methylation in DNA from 55 cases of ESCC. Methylation of the RASSF1A gene was found in 13 of 55 (24%) cases of primary ESCC. No association was found between the promoter methylation of the RASSF1A gene in primary ESCC and age, gender, localization, invasion depth, or tumor stage. Association was found with tumor differentiation. There was no correlation with its prognosis. In conclusion, it was suggested that an inactivation of the RASSF1A gene due to promoter methylation was associated with de-differentiation of the tumor in ESCC.     

Aberrant methylation of multiple tumor suppressor genes in aging liver, chronic hepatitis, and hepatocellular carcinoma

Aberrant DNA methylation is an important epigenetic alteration in hepatocellular carcinoma (HCC). However, the molecular processes underlying the methylator phenotype and the contribution of hepatitis viruses are poorly understood. The current study is a comprehensive methylation analysis of human liver tissue specimens. A total of 176 liver tissues, including 77 pairs of HCCs and matching noncancerous liver and 22 normal livers, were analyzed for methylation. Methylation of 19 epigenetic markers was quantified, and the results were correlated with different disease states and the presence or absence of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections. Based on methylation profiles, the 19 loci were categorized into 3 groups. Normal liver tissues showed methylation primarily in group 1 loci (HIC-1, CASP8, GSTP1, SOCS1, RASSF1A, p16, APC), which was significantly higher than group 2 (CDH1, RUNX3, RIZ1, SFRP2, MINT31) and group 3 markers (COX2, MINT1, CACNA1G, RASSF2, MINT2, Reprimo, DCC) (P < 0.0001). Noncancerous livers demonstrated increased methylation in both group 1 and group 2 loci. Methylation was significantly more abundant in HCV-positive livers compared with normal liver tissues. Conversely, HCC showed frequent methylation at each locus investigated in all 3 groups. However, the group 3 loci showed more dense and frequent methylation in HCV-positive cancers compared with both HBV-positive cancers and virus-negative cancers (P < 0.0001). CONCLUSION: Methylation in HCC is frequent but occurs in a gene-specific and disease-specific manner. Methylation profiling allowed us to determine that aberrant methylation is commonly present in normal aging livers, and sequentially progresses with advancing stages of chronic viral infection. Finally, our data provide evidence that HCV infection may accelerate the methylation process and suggests a continuum of increasing methylation with persistent viral infection and carcinogenesis in the liver.     

The Ras effector RASSF2 is a novel tumor-suppressor gene in human colorectal cancer

BACKGROUND & AIMS: Activation of Ras signaling is a hallmark of colorectal cancer (CRC), but the roles of negative regulators of Ras are not fully understood. Our aim was to address that question by surveying genetic and epigenetic alterations of Ras-Ras effector genes in CRC cells. METHODS: The expression and methylation status of 6 RASSF family genes were examined using RT-PCR and bisulfite PCR in CRC cell lines and in primary CRCs and colorectal adenomas. Colony formation assays and flow cytometry were used to assess the tumor suppressor activities of RASSF1 and RASSF2. Immunofluorescence microscopy was used to determine the effect of altered RASSF2 expression on cell morphology. Mutations of K- ras , BRAF, and p53 were identified using single-strand conformation analysis and direct sequencing. RESULTS: Aberrant methylation and histone deacetylation of RASSF2 was associated with the gene's silencing in CRC. The activities of RASSF2, which were distinct from those of RASSF1, included induction of morphologic changes and apoptosis; moreover, its ability to prevent cell transformation suggests that RASSF2 acts as a tumor suppressor in CRC. Primary CRCs that showed K- ras /BRAF mutations also frequently showed RASSF2 methylation, and inactivation of RASSF2 enhanced K- ras -induced oncogenic transformation. RASSF2 methylation was also frequently identified in colorectal adenomas. CONCLUSIONS: RASSF2 is a novel tumor suppressor gene that regulates Ras signaling and plays a pivotal role in the early stages of colorectal tumorigenesis.     

Promoter methylation profile in gallbladder cancer

Background Methylation in the promoter region of genes is an important mechanism of inactivation of tumor suppressor genes. Our objective was to analyze the methylation pattern of some of the genes involved in carcinogenesis of the gallbladder, examining the immunohistochemical expression of proteins, clinical features, and patient survival time. Methods Twenty cases of gallbladder cancer were selected from the frozen tumor bank. The DNA extracted was analyzed by means of a methylation-specific polymerase chain reaction test for the CDKN2A (p16), MLH1, APC, FHIT, and CDH1 (E-cadherin) genes. Morphological and clinical data and follow-up information were obtained. Results All cases were in an advanced stage: histologically moderate or poorly differentiated tumors (95%). Methylation of the promoter area of genes was observed in 5%, 20%, 30%, 40%, and 65% of cases, and an altered immunohistochemical pattern (AIP) in 5%, 35%, 21%, 25%, and 66% for the MLH1, CDKN2A, FHIT, APC, and CDH1 genes, respectively. The Kappa concordance index between methylation of the promoter area and AIP for the MLH1 and CDH1 genes was very high (K > 0.75) and substantial for APC (K > 0.45). No correlation was found between survival time and the methylation of the genes studied. Conclusions The high frequency of gene methylation (with the exception of MLH1) and the high agreement between AIP and methylation of the gene promoter area for the MLH1, APC, and CDH1 genes suggest that the inactivation of tumor suppressor genes and of the genes related to the control of cellular proliferation through this mechanism is involved in gallbladder carcinogenesis.     

胃癌维甲酸信号通路相关基因启动子区协同高甲基化的研究

背景：启动子区高甲基化与胃癌中多种抑癌基因表达沉默密切相关。目的：探讨维甲酸信号通路相关基因维甲酸受体B（RAR13）、细胞维生素A结合蛋白1（CRBP1）和他扎罗汀诱导基因1（TIG1）启动子区高甲基化与胃癌的关系。方法：以甲基化特异性聚合酶链反应（MSP）检测40例胃癌标本、10例正常胃黏膜标本和6株胃癌细胞株的RAR13、CRBPI和TIG1基因启动子区甲基化状态，分析i者甲基化状态的相关性及其与胃癌1晦床病理特征的关系。以逆转录聚合酶链反应（RT—PCR）检测胃癌细胞株RAR13、CRBP1和TIG1mRNA表达。结果：40例胃癌组织的RAR13、CRBPI和TIG1基因甲基化率分别为45．0％、32．5％和57．5％，10例正常胃黏膜组织均未检测到上述基因甲基化（P〈0．05）。胃癌组织中RAR13的甲基化状态与CRBP1和TIG1的甲基化状态显著相关（P〈0．05），但三者的甲基化状态与胃癌临床病理特征无相关性。启动子区高甲基化胃癌细胞株相应基因mRNA表达缺失或减弱。结论：胃癌组织常发生维甲酸信号通路相关基因RAR13、CRBP1和TIG1启动子区高甲基化，高甲基化可能是相应基因转录失活的重要原因。