妇科肿瘤与APC基因启动子甲基化研究进展

腺瘤性结肠息肉病（APC）基因是Wnt信号转导通路重要的抑癌基因,其启动子区域的异常甲基化可影响APC基因mRNA的转录和APC蛋白的表达,导致Wnt信号转导通路异常。近年来在妇科肿瘤的多项研究中发现了APC基因启动子区域异常甲基化,其与肿瘤的发生、发展有关。现就APC基因启动子甲基化与妇科肿瘤的研究进展进行综述。     

结直肠锯齿状病变h-MLH1基因甲基化状态和蛋白表达意义研究

目的：通过研究结直肠锯齿状病变组织中h-MLH1基因启动子区CpG岛甲基化及蛋白表达,探讨h-MI．H1启动子甲基化状态与蛋白表达相关性及在锯齿状癌变通路中的作用,并分析hMLH1基因在不同年龄层段甲基化程度。方法：收集北京军区总医院病理科2007-0101-201212-31诊断为锯齿状病变标本225例,其中包括96例增生性息肉（hyperplasticpolyp,HP）、61例广基（无蒂）锯齿状腺瘤/息肉（sessileserratedadenoma／polyp,SSA／P）和68例传统锯齿状腺瘤（traditionalserratedadenoma,TSA）;同时收集同院同期的54例管状腺瘤（tubularadenoma,TA）、69例结直肠癌（colorectaIcancer,CRC）和42例正常结直肠黏膜组织作为对照。应用Taqman探针qPCR（MethyLight）方法检测各组织中h-MLH1基因CpG岛甲基化状态,同时采用免疫组织化学方法检测其蛋白表达水平,其中随机抽取锯齿状病变116例（HP52例、SSA／P41例、TSA23例）、TA20例、CRC24例和正常结直肠黏膜组织24例,并将其甲基化状态与相应的蛋白表达水平及临床病理学资料进行统计学分析。结果：正常、TA、HP、SSA／P、TSA和CRC组织中,MLH1基因启动子CpG岛甲基化阳性表达率分别为9．24％（4／42）、40．74％（22／54）、22．92％（22／96）、45．90％（28／61）、61．76％（42／68）和52．17％（36／69）。HP组与正常、SSA／P、TSA及CRC组之间比较,正常组与SSA／P及TSA组之间比较,差异均有统计学意义,P〈0．05;其余各组之间比较,差异均无统计学意义,P〉0．05。正常、TA、HP、SSA／P、TSA和CRC组织中,h-MLH1蛋白阳性表达率分别为100％（24／24）、80．00％（16／20）、98．08％（51／52）、75．61％（31／41）、69．57％（16／23）和70．83％（17／24）。正常组与HP、SSA／P、TSA、TA、CRC组之间比较,差异均有统计学意义,P％0．05;其余各组之间比较,差异均无统计学意义,P〉0．05。TA、SSA／P和TSA组中,hMLH1基因甲基化与其蛋白表达差异均有统计学意义（P〈o．05）,且呈负相关,相关系数．y分别为-0．553、-0．497、和-0．473。TA、HP、SSA／P和TSA组中,h-MLH1基因甲基化与年龄差异均有统计学意义（P〈0．05）,且呈正相关,相关系数7分别为0．475、0．289、0．450和0．575。结论：结直肠锯齿状病变组织中h-MLH1基因甲基化可能导致其蛋白表达下调,与锯齿状病变的发生和发展密切相关,同时,h-MLH1基因甲基化又可能与年龄相关,随年龄增长,甲基化程度越高。     

Molecular detection of p16 promoter methylation in the serum of colorectal cancer patients

Assays based on the molecular detection of genetic changes in serum have been shown as potential diagnostic tools for colorectal cancer. We examined the methylation status of p16 in colorectal cancers using methylation-specific PCR (MSP). Forty-four of 94 (47%) cancer DNA exhibited abnormal promoter methylation of p16 gene while no corresponding normal DNA exhibited such methylation. Subsequently, we examined whether aberrant methylation could be detected in corresponding serum DNA, and found that 13 of 44 (30%) patients with p16 promoter methylation in tumor DNA demonstrated abnormal methylation in their serum DNA. Moreover, abnormal methylation was found in the serum of patients in all clinical stages, suggesting that early colorectal cancer could be detected using the MSP method.     

结直肠癌组织EGFR表达与淋巴结及肝转移相关性的Meta分析

目的:分析研究表皮生长因子(EGFR)在中国结直肠癌患者癌组织中的表达与淋巴结转移及肝脏转移的相关性。方法:利用万方、维普、CNKI、PubMed、Web of Science和EMBASE数据库,以结直肠癌、结直肠肿瘤、大肠癌、EG-FR、表皮生长因子受体为关键词,检索2000-2012年公开发表的关于结直肠癌患者癌组织中EGFR的表达与淋巴结转移及肝脏转移关系的文献,对文献进行筛选和评价,符合标准的文献用Revman 5.0软件进行Meta分析。结果:EG-FR表达与淋巴结转移相关文献入选17篇,共2 092例患者,淋巴结转移患者1 040例,523例EGFR阳性,无淋巴结转移者1 052例,327例EGFR阳性,异质性检验提示各研究结果间存在异质性(χ2=43.48,P=0.000 2,I2=63%),采用随机效应模型进行合并OR=3.17,95%CI=2.19～4.60,合并效应量的检验结果显示z=6.08,差异有统计学意义(P<0.01),提示有淋巴结转移的患者,癌组织中EGFR的表达高于无淋巴结转移者;EGFR表达与肝转移相关文献入选4篇,共385例患者,其中肝转移患者154例,90例EGFR阳性,无肝转移者231例,65例EGFR阳性,异质性检验存在异质性(χ2=14.44,P=0.002,I2=79%),采用随机效应模型进行合并,OR=3.99,95%CI=1.04～15.36,合并效应量的检验结果显示z=2.01,差异有统计学意义(P=0.04),提示有肝转移的患者,癌组织中EGFR的表达显著高于无肝转移者。结论:在中国结直肠癌患者中,发生淋巴结转移和肝转移的患者癌组织中EGFR的表达明显升高,EGFR检测对筛选高危转移者具有重要意义。     

Molecular detection of p16 promoter methylation in the serum of recurrent colorectal cancer patients

We previously proved that p16 promoter methylation present in the tumors of colorectal cancer patients can be detected in the serum of those same patients using methylation-specific PCR (MSP). To seek the possibility that this technique could be applied to the monitoring of cancer recurrence, we examined the p16 methylation using MSP. We detected tumor DNA in the serum of 31 of 45 (69%) patients with recurrent colorectal cancer. No methylation was found in serum DNA of 50 patients with colorectal cancers whose corresponding tumor DNA had no methylation in p16 promoter. These results suggested that MSP might be a sensitive and useful method to detect recurrent colorectal cancer in serum.     

Regulation of MLH1 mRNA and protein expression by promoter methylation in primary colorectal cancer: a descriptive and prognostic cancer marker study

Background

In colorectal cancer MLH1 deficiency causes microsatellite instability, which is relevant for the patient’s prognosis and treatment, and its putative heredity. Dysfunction of MLH1 is caused by sporadic gene promoter hypermethylation or by hereditary mutations as seen in Lynch Syndrome. The aim of this study was to determine in detail how DNA methylation regulates MLH1 expression and impacts clinical management.

Methods

Colorectal cancer samples were collected from 210 patients. The laboratory methods used to study these samples included methylation specific multiplex ligation-dependent probe amplification (MS-MLPA), real-time quantitative PCR (qPCR), and immunohistochemistry (IHC).

Results

We found that the MLH1 mRNA and protein expression levels were highly related. MS-MLPA was successful in tumors from 195 patients. In these tumors, hypermethylation was observed in promoter regions A (n?=?57), B (n?=?30), C (n?=?28), and D (n?=?47), and in intron 1 (n?=?25). The promoter region C and intron 1 methylation levels were found to be excellently suited for discriminating between low and high gene expression levels, whereas those of promoter regions A, B and D were less specific. Hypermethylation in any region (n?=?77) served as an independent prognostic factor (hazard ratio 0.56, 95 % confidence interval 0.36–0.89, p?=?0.01).

Conclusions

MLH1 inactivation through hypermethylation was found to be related to improved survival. Hypermethylation in promoter region C and intron 1 served as the most specific markers for this inactivation.     

大肠癌组织DCC基因启动子甲基化及表达水平相关性研究

目的:探讨结直肠癌缺失基因 (DCC)在大肠癌组织中的表达特征及其与启动子甲基化的相关性.方法:分别采用免疫组织化学和甲基化特异性PCR (MSP)方法检测71例大肠癌及其相应癌旁组织中DCC蛋白的表达情况及DCC基因启动子甲基化状态.结果:大肠癌组织中DCC蛋白表达水平 (35/71, 49.3%) 显著低于癌旁正常组织 (34/39, 87.2%, P<0.001),且与临床Duke分期相关,P=0.023;大肠癌组织中DCC基因启动子甲基化发生率 (54/71, 76.1%)高于癌旁正常组织 (14/39, 35.9%, P<0.001)和癌旁炎性组织 (10/22, 45.5%, P=0.007),且直肠癌患者DCC基因启动子甲基化发生率 (28/31, 90.3%)高于结肠癌患者 (27/40, 67.5%, P=0.022);大肠癌组织中DCC蛋白失表达组甲基化发生率 (34/36, 94.4%)显著高于DCC蛋白表达组 (20/35, 57.1%, P<0.001).结论:DCC基因启动子甲基化可能是大肠癌中DCC失表达的主要机制之一.     

肝细胞癌中APC基因启动子甲基化及蛋白表达的研究

目的:探讨肝细胞癌中APC基因启动子甲基化状态及蛋白表达的临床意义.方法:应用甲基化特异性聚合酶链反应(MSP)和免疫组织化学方法检测61例HCC及相应的癌旁肝组织中APC基因启动子甲基化状态和蛋白表达水平,分析甲基化与临床资料及蛋白表达的关系.结果:癌组织及癌旁组织中APC基因启动子甲基化阳性率分别为26.23%和11.47%(P<0.05).癌与癌旁组织APC蛋白表达无统计学差异(P>0.05).APC基因启动子甲基化与临床分期、门脉癌栓、术后复发、肝外转移、肿瘤大小、肿瘤分化、肿瘤个数及血清AFP值无关.APC基因启动子甲基化与蛋白表达无相关性.结论:APC启动子区甲基化可能参与了肝癌的发生,但在HCC的发展中的作用仍需进一步研究.     

肝细胞癌中APC基因启动子甲基化及蛋白表达的研究

目的：探讨肝细胞癌中APC基因启动子甲基化状态及蛋白表达的临床意义。方法：应用甲基化特异性聚合酶链反应（MSP）和免疫组织化学方法检测61例HCC及相应的癌旁肝组织中APC基因启动子甲基化状态和蛋白表达水平,分析甲基化与临床资料及蛋白表达的关系。结果：癌组织及癌旁组织中APC基因启动子甲基化阳性率分别为26.23%和11.47%（P〈0.05）。癌与癌旁组织APC蛋白表达无统计学差异（P〉0.05）。APC基因启动子甲基化与临床分期、门脉癌栓、术后复发、肝外转移、肿瘤大小、肿瘤分化、肿瘤个数及血清AFP值无关。APC基因启动子甲基化与蛋白表达无相关性。结论：APC启动子区甲基化可能参与了肝癌的发生,但在HCC的发展中的作用仍需进一步研究。     

Molecular mechanisms of hepatic metastasis in colorectal cancer

BACKGROUND: Colorectal cancer currently accounts for 11% of all cancers in the United States and is the second leading cause of cancer-related death, with the majority of deaths attributable to hepatic metastases. Many new studies are elucidating the complex molecular factors involved in this event, which could be used to generate clinically applicable screening and therapeutic tools. METHODS: An initial Pubmed and Medline literature search using keywords such as, molecular factor, colorectal cancer, hepatic metastasis/es, and main headings, such as angiogenesis, was reviewed. Since there are many molecular factors involved in this process not all could be included in this review. The list of discussed gene products was limited to the most studied factors, identified by the number of references in the literature search, and additional recently discovered gene products with in-vivo evidence of strong metastasis association. RESULTS: Twenty molecular factors were identified and included in the discussion of this review article. The molecular factors were separated into four groups based on their function, they are: proteolysis, adhesion, angiogenesis, and cell survival. All factors have a promising role as a screening or therapeutic target. CONCLUSION: This review has identified the many recent advances in elucidating the pathways involved in colorectal cancer hepatic metastasis. By better understanding the many complex molecular events involved in metastasis, novel screening and therapeutic tools may be developed with the ultimate goal of preventing metastasis and increasing patient survival.     

K-ras mutations and RASSF1A promoter methylation in colorectal cancer

Human cancer is characterized by genetic and epigenetic alterations. In this study we provide evidence for the interruption of Ras signaling in sporadic colorectal cancer (CRC) by either genetic activation of the K-ras oncogene or epigenetic silencing of the putative tumor suppressor gene RASSF1A. Paraffin embedded tumor tissue samples from 222 sporadic CRC patients were analysed for K-ras codon 12 and codon 13 activating mutations and RASSF1A promoter hypermethylation. Overall, K-ras mutations were observed in 87 of 222 (39%) and RASSF1A methylation was observed in 45 of 222 (20%) of CRCs. Mutation of K-ras alone was detected in 76 of 222 (34%) CRCs. RASSF1A promoter methylation with wild-type K-ras was observed in 34 of 222 (15%) CRCs. In 101 of 222 (46%) CRCs neither K-ras mutations nor RASSF1A methylation was observed and 11 of 222 (5%) CRCs showed both K-ras mutations and RASSF1A methylation. These data show that the majority of the studied CRCs with K-ras mutations lack RASSF1A promoter methylation, an event which occurs predominantly in K-ras wild-type CRCs (P=0.023, Chi-square test).     

脑胶质瘤O6-甲基鸟嘌呤-DNA甲基转移酶启动区甲基化及其表达异质性的研究

目的研究脑胶质瘤组织不同部位O6-甲基鸟嘌呤-DNA甲基转移酶（MGMT）启动区甲基化状态及其表达的差异性。方法在54例脑胶质瘤组织的中心和周边部位分别获取标本,共获得92份标本,采用巢式甲基化特异性PCR（MSP）进行MGMT启动区甲基化状态的检测,同时采用免疫组织化学方法进行MGMT蛋白表达的检测。结果 38例胶质瘤中获得了肿瘤两个不同部位MG-MT启动区甲基化的状态,其中24例胶质瘤MGMT启动区甲基化的状态是一致的,占总数的63.2%（24/38）。在29例胶质瘤患者中获得了肿瘤两个不同部位MGMT蛋白表达的情况,其中10例胶质瘤MGMT蛋白表达是一致的,占总数的34.5%（10/29）。两总体一致性概率间差值的95%置信区间为（5.6%和51.8%）,两者的差异有统计学意义。巢式MSP和免疫组化都获得检测结果的标本有77份,在61份MGMT启动区甲基化标本中,25份MGMT蛋白表达阴性,14份蛋白表达可疑阳性,18份蛋白表达阳性,4份蛋白表达强阳性。在16份MGMT启动区非甲基化标本中,2份MGMT蛋白表达阴性,2份蛋白表达可疑阳性,9份蛋白表达阳性,3份蛋白表达强阳性,MGMT启动区甲基化状态与蛋白表达呈负相关（r=-0.318,P=0.005）。结论脑胶质瘤MGMT蛋白表达在同一肿瘤的不同部位存在明显的异质性。虽然脑胶质瘤MGMT启动区甲基化的状态在同一肿瘤的不同部位存在一定的异质性,但是大多数脑胶质瘤MGMT启动区甲基化的状态在同一肿瘤的不同部位是一致的。脑胶质瘤MGMT启动区甲基化状态的一致性优于蛋白表达的一致性。脑胶质瘤MGMT启动区甲基化,MGMT蛋白表达较少,MGMT启动区非甲基化,MGMT蛋白表达较多。     

TWIST1 and TWIST2 promoter methylation and protein expression in tumor stroma influence the epithelial-mesenchymal transition-like tumor budding phenotype in colorectal cancer

Tumor budding in colorectal cancer is likened to an epithelial-mesenchymal transition (EMT) characterized predominantly by loss of E-cadherin and up-regulation of E-cadherin repressors like TWIST1 and TWIST2. Here we investigate a possible epigenetic link between TWIST proteins and the tumor budding phenotype. TWIST1 and TWIST2 promoter methylation and protein expression were investigated in six cell lines and further correlated with tumor budding in patient cohort 1 (n = 185). Patient cohort 2 (n = 112) was used to assess prognostic effects. Laser capture microdissection (LCM) of tumor epithelium and stroma from low- and high-grade budding cancers was performed. In colorectal cancers, TWIST1 and TWIST2 expression was essentially restricted to stromal cells. LCM results of a high-grade budding case show positive TWIST1 and TWIST2 stroma and no methylation, while the low-grade budding case was characterized by negative stroma and strong hypermethylation. TWIST1 stromal cell staining was associated with adverse features like more advanced pT (p = 0.0044), lymph node metastasis (p = 0.0301), lymphatic vessel invasion (p = 0.0373), perineural invasion (p = 0.0109) and worse overall survival time (p = 0.0226). Stromal cells may influence tumor budding in colorectal cancers through expression of TWIST1. Hypermethylation of the tumor stroma may represent an alternative mechanism for regulation of TWIST1.     

肺癌E-cadherin基因启动子CpG岛甲基化与蛋白表达的关系及其意义

背景与目的：目前认为CpG岛甲基化导致转录抑制是恶性肿瘤发生的重要机制之一.E-cadherin能抑制肿瘤细胞的浸润和转移,被公认为是浸润、转移抑制基因.本研究检测肺癌组织中E-cadherin基因启动子CpG岛甲基化的状况,并探讨基因异常甲基化与蛋白表达的关系及其意义.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-cadherin基因启动子CpG岛甲基化的状况.采用免疫组化S-P法相应检测了E-cadherin蛋白的表达.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） （P＜0.05）.9例正常肺组织中未检测到此基因的甲基化（0/9）.22例癌组织中E-cadherin蛋白表达减弱或缺失率59.1%（13/22）,显著高于相应癌旁组织蛋白表达减弱缺失率27.3%（6/22）.肺癌组织中发生甲基化者蛋白表达率及强度明显低于未甲基化者.结论：肺癌组织中存在E-cadherin基因启动子CpG岛的异常甲基化,E-cadherin基因启动子CpG岛的异常甲基化可能是E-cadherin蛋白表达下调的主要原因.     

结直肠癌肝转移的发生机制

结直肠癌的发病率及死亡率在全世界以每年递增的趋势发展着,而其主要的死亡原因是肝转移。这一事件引起了众多学者的关注,大量研究也从各方面对其机理进行了论证。我们应用PubMed和MedLine,以及中国期刊网全文数据库(CNKI)两大文献检索文库,用"结直肠癌"、"肝转移"、"分子机制"等关键词进行检索,总结了近十年间有关结直肠癌的研究,试图提供一个结直肠癌肝转移的基本框架。本文中重点分析一些可能控制此事件的关键分子,对8类13项分子指标,包括基质金属蛋白酶、尿激酶型纤溶酶原激活剂受体、整合素、骨桥蛋白、肿瘤坏死因子相关凋亡诱导配体、干扰素-β、胰岛素样生长因子Ⅰ型受体、核基质蛋白、血管上皮生长因子、过氧化物酶体增殖物激活受体、胰岛素样生长因子、细胞外信号调节激酶和蛋白酶活化受体等与结直肠癌之间的关系进行了总结和分析,以期为寻找治疗和预测结直肠癌肝转移的新靶点提供新思路。     

血浆RNF180启动子甲基化及其蛋白表达在胃癌诊断中的价值

  目的  探讨血浆RNF180基因启动子甲基化及其蛋白表达在胃癌临床诊断中的价值。  方法  采用甲基化特异性PCR法(MSP)和ELISA法检测各组患者血浆中RNF180甲基化状态和RNF180蛋白表达情况,并分别将其与各临床病理指标进行统计学分析。  结果  MSP结果显示胃癌患者血浆中RNF180基因启动子甲基化率为62.75%,健康者为21.88%,其差异具有统计学意义(P < 0.01)。RNF180甲基化阳性率与肿瘤大小、临床分期、分化程度、淋巴结转移以及远处转移密切相关(P < 0.05)。ELISA结果显示胃癌血浆RNF180蛋白水平(23.22±1.36) μg/mL明显低于对照健康组(34.25±2.44) μg/mL,差异具有统计学意义(P < 0.01)。胃癌血浆RNF180蛋白表达水平与临床病理特征无统计学意义(P>0.05)。  结论  胃癌患者血浆RNF180基因表达存在高甲基化率,而RNF180蛋白表达明显下降,提示血浆RNF180基因甲基化可作为一种微创的检测方法在临床胃癌诊断中有潜在的应用价值。      

胃癌组织hMLH1启动子甲基化是造成其蛋白表达降低的主要原因

目的：通过研究胃癌中错配修复基因hMLH1启动子区5CpG岛甲基化及蛋白表达情况，探讨hMLH1启动子Ⅸ甲基化对蛋白表达的影响及在胃癌发病中的作用。方法：收集诊断明确且未经放化疗的胃癌手术切除标本41例及同病例癌旁黏膜。应用免疫组化SP法检测标本hMLH1蛋白表达情况。应用甲基化特异性PCR（MSP）榆测标本hMLH1启动子区甲基化情况。结果：胃癌组与癌旁组，hMLH1蛋白阳性表达率分别为58．54％（24／41）和80．49％（33／41）（P〈0．05）；启动子甲基化率分别为80．49％（33／41）和24．39％（10／41）（P〈0．05）；完全甲基化率分别为41．46％（17／41）和19．51％（8／41）（P〈0．05）；部分甲基化率分别为39．02％（16／41）和4．88％（2／41）（P〈0．05）。无论胃癌组织还是癌旁组织，完全甲基化病例均出现hMLH1蛋白表达缺失，部分甲基化病例和启动子未甲基化病例均有hMLH1蛋白表达。hMLHI基因启动子甲基化率与胃癌患者性别、年龄、癌组织分化程度、浸润深度和淋巴结转移均无明显相关性（P〉0．05）。结论：hM—LH1基因启动子甲基化是导致hMLH1蛋白表达降低的主要原因；胃黏膜hMLH1蛋白表达降低有助于胃癌的预警。     

APC promoter hypermethylation contributes to the loss of APC expression in colorectal cancers with allelic loss on 5q

INTRODUCTION: Germ-line mutations of the APC gene are associated with familial adenomatous polyposis, and somatic mutations occur frequently in sporadic colorectal cancer. However, to abrogate APC function, both alleles must be inactivated. Recently, it has been demonstrated that epigenetic modification of the APC promoter influences APC silencing. Here we examined the influence of APC methylation on APC expression in tumors with and without LOH at the APC locus. MATERIAL AND METHODS: 137 sporadic colorectal cancer specimens were investigated for LOH at the 5q locus. The methylation status of the APC promoter was determined by methylation-specific PCR. APC expression was performed by immunohistochemistry. RESULTS: Expression was reduced or lost in 110 of 137 (80%) tumors and LOH at 5q was found in 13 of 132 (10%) tumors. There was no difference in 5q LOH between tumors with or without intact APC expression. Vice versa, there was no difference in the APC expression in tumors with 5q LOH. Aberrant APC promoter methylation was detected in 33 of 118 (28%) tumors investigated. Of the tumors with 5q LOH for which methylation data were available, 4 of 11 (36%) were methylated versus 28 of 105 (27%) of those without LOH. No difference in methylation was observed in tumors without 5q LOH and normal APC expression and those without 5q LOH and reduced or missing APC expression. Importantly, none of the tumors with 5q LOH and normal APC staining were aberrantly methylated, whereas 50% of the cancers with LOH at 5q and reduced or absent staining were hypermethylated. CONCLUSIONS: This report suggests that tumors with 5q LOH and reduced APC expression are more frequently hypermethylated at the APC promoter compared to those tumors with 5q LOH and normal APC expression. The association among APC promoter methylation status, 5q LOH, and reduced or lost APC expression suggests that de novo methylation plays an important role as a "second hit" in silencing APC expression in colorectal neoplasia.