胃癌相关抑癌基因甲基化研究进展

DNA甲基化是一种表观遗传修饰,它与肿瘤的发生关系密切。DNA甲基化是基因表达调控的一种方式。抑癌基因启动子高甲基化可以使其表达失活,导致肿瘤发生。胃癌的发生与多基因异常表达密切相关,其中抑癌基因甲基化是胃癌发生发展的重要机制之一。     

Expression of BRCA1 protein in benign, borderline, and malignant epithelial ovarian neoplasms and its relationship to methylation and allelic loss of the BRCA1 gene

BRCA1 is a putative tumour suppressor gene responsible for a hereditary ovarian cancer syndrome. To clarify the possible involvement of BRCA1 in the development of sporadic ovarian neoplasms, this study analysed the immunohistochemical expression of BRCA1 protein in normal ovarian surface epithelium and 119 epithelial ovarian tumours (19 benign, 24 borderline, and 76 malignant tumours). Loss of heterozygosity (LOH) of BRCA1 was examined using three microsatellite markers to analyse the relationship between BRCA1 expression and alterations of the BRCA1 gene. Methylation of the BRCA1 promoter was also analysed by methylation-specific PCR. In ovarian carcinomas showing heterogeneous expression of BRCA1 protein in the same tumour, LOH and methylation status were analysed using microdissection techniques. Finally, the relationship of BRCA1 expression or its genetic alteration to clinicopathological parameters and patient survival was analysed. Ovarian surface epithelial cells expressed BRCA1 protein. Decreased expression of BRCA1 was found in 16% of benign tumours, 38% of borderline tumours, and 72% of carcinomas. LOH of BRCA1 was demonstrated in no benign tumours, 15% of borderline tumours, and 66% of carcinomas. Methylation of BRCA1 was not detected in benign or borderline tumours, but was present in 31% of carcinomas. Reduced expression of BRCA1 correlated with the presence of gene methylation. The frequency of BRCA1 methylation and LOH was higher in serous carcinomas than in other types. In one of the three serous carcinomas that showed heterogeneous expression of BRCA1, BRCA1-positive borderline-like tumour cells were LOH-positive and methylation-negative, whereas adjacent BRCA1-negative carcinoma cells were LOH-positive and methylation-positive. The prognosis of carcinoma patients did not correlate with BRCA1 expression or genetic status. These findings suggest that reduced expression of BRCA1 protein along with genetic and epigenetic changes of the BRCA1 gene play an important role in the development of sporadic ovarian carcinomas, particularly those of serous histology.     

DNA甲基化及其调控与肿瘤

表观遗传学是调控肿瘤发生的重要机制之一,其最为常见的方式是甲基化。DNA甲基化通过调节基因的表达影响胚胎发育及肿瘤发生。癌基因启动子区的低甲基化导致其转录激活,抑癌基因启动子区的高甲基化导致其转录抑制,这两者是肿瘤形成的重要途径。     

BRCA1基因复杂甲基化模式

应用体外甲基化酶M-SssI处理和甲基化敏感单链构象分析法(Methylation-sensitivesingle-strand conformation     

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.     

软组织平滑肌肉瘤中肿瘤抑制基因p15,p16的表达

目的：探讨p15,p16蛋白在软组织平滑肌肉瘤（LMS）及平滑肌瘤（LM）的表达情况及其意义,方法：采用免疫组织化学方法检测38例LMS及20例LM标本的p15,p16蛋白表达情况,结果：在LMS,p15,p16的阴性率分别为18．42％及42．1％,二者差异有显著性。p15在LM的阴性率为60％,高于LMS。38例LMSp15和p16总异常率为52．6％,其中Ⅰ级LMS异常率显著高于Ⅱ、Ⅲ级。随访15例LMS,复发死亡组p15和p16异常率达75％,高于无复发组。结论：在LMSp16表达缺失比p15缺失更为常见,p15的缺失在LM在比在LMS常见,LMS的发生发展及预后p15及p16共同失活有关。     

改进的甲基化特异PCR法及在抑癌基因p16检测中的应用

目的　介绍一种 Ｃｐ Ｇ 岛甲基化分析方法,即甲基化特异的 Ｐ Ｃ Ｒ（ ｍ ｅｔｈｙｌａｔｉｏｎ ｓｐｅｃｉｆｉｃ ｐｏｌｙｍ ｅｒａｓｅ ｃｈａｉｎ ｒｅａｃｔｉｏｎ , Ｍ Ｓ Ｐ） 法以及对该法的改进。方法　用亚硫酸氢盐修饰被测 Ｄ Ｎ Ａ 后,再进行甲基化与非甲基化特异的 Ｐ Ｃ Ｒ 扩增,并对 Ｍ Ｓ Ｐ 法进行改进。应用该法分析了颌面部鳞癌中ｐ１６ 基因５′ Ｃｐ Ｇ 岛甲基化状态。结果　发现一些颌面部鳞癌组织中有ｐ１６ 基因５′ Ｃｐ Ｇ 岛的甲基化。采用加热变性代替强碱变性,用透析法脱盐,以及用限制酶 Ｔａｑ Ⅰ取代 Ｂｓｔ Ｕ Ｉ来判断甲基化与非甲基化的扩增片段等均取得了良好的效果。结论　 Ｍ Ｓ Ｐ 法是一种较为简便、灵敏和具特异性的甲基化检测方法,改进后该方法更加简便可行。     

急性白血病p53基因P1启动子区域DNA甲基化研究

目的：通过检测急性白血病（AL）中p53基因P1启动子异常甲基化，探讨p53基因异常甲基化在急性白血病中的意义。方法:分别使用限制性内切酶MspⅠ、HpaⅡ、EcoRⅡ、BstNⅠ酶切提取基因组DNA，然后分别使用酶切后产物及基因组DNA为模板进行PCR扩增。产物电泳后在凝胶成像分析系统内观测电泳条带及摄像；部分标本的电泳条带经凝胶回收纯化后进行测序。结果:急性白血病患者p53基因第一启动子甲基化阳性率为38.7％，而急性淋巴细胞白血病（ALL）与急性非淋巴细胞白血病(ANLL)患者分别为45.5％、35.0％。正常对照标本中未检测到p53基因的异常甲基化。p53基因甲基化情况在急性白血病病人与正常人之间经过统计学检验，P<0.05；但急性淋巴细胞白血病与急性非淋巴细胞白血病患者之间无显著差异，P>0.05。分析急性白血病患者p53基因甲基化与患者临床资料之间的关系，其中，p53基因异常甲基化与肝脾淋巴结是否肿大之间的关系经统计学分析P<0.05。结论:①部分急性白血病患者存在p53基因第一启动子异常甲基化，正常对照中未检测到p53基因的甲基化；②p53基因第一启动子在急性淋巴细胞白血病与急性非淋巴细胞白血病均可发生异常甲基化，两者之间发生甲基化的概率无统计学差异；③p53基因异常甲基化与肝脾淋巴结肿大有显著差异，但p53基因异常甲基化与急性白血病治疗效果及预后的关系尚不能确定，须进一步研究确定。     

Semaphorin-3F functions as a tumor suppressor in colorectal cancer due to regulation by DNA methylation

Semaphorin-3F (SEMA3F) is a member of the class III semaphorin family, and is seen as a candidate tumor suppressor gene. The aims of this study were to evaluate the effect of SEMA3F in colorectal cancer (CRC) patients, and to explore the mechanism for that SEMA3F suppresses tumor progression and metastasis. The expression levels of SEMA3F in the colorectal cancer tissues and corresponding non-tumor colorectal tissues were determined by Western blotting and real-time quantitative PCR (qRT-PCR). In addition, we evaluate the effects of SEMA3F on CRC cell migration and colony formation in vitro. Subsequently, quantitative methylation-specific PCR (qMSP) was used to detect the DNA methylation status in the CpG islands of SEMA3F gene promoter in normal colon and colorectal cancer cell lines, colorectal cancer tissues and corresponding non-tumor colorectal tissues. We found that SEMA3F was downregulated in the protein (P < 0.01) and mRNA (P < 0.001) levels in CRC tissues as compared to matched adjacent non-tumor tissues. Moreover, MSP assay showed high levels of SEMA3F gene promoter methylation in the CpG islands in some CRC cell lines and tissue samples. Furthermore, SEMA3F expression was reactivated in CRC cell lines after treatment with 5-Aza-CdR, demethylation of SW620 cells resulted in cell colony formation and invasion inhibition. These findings suggest DNA methylation of promoter CpG island-mediated silencing of the tumor suppressor SEMA3F gene plays an important role in the carcinogenesis of CRC.     

软组织平滑肌肉瘤中p16基因的甲基化检测

目的 探讨软组织平滑肌肉瘤（ＬＭＳ）中p16基因ＩＮＫ４Ａ的甲基化状态及其与p16表达的关系。方法 应用ＭＳＰ法检测３８例软组织平滑肌肉瘤,１０例平滑肌瘤及５例正常平滑肌组织中p16基因ＩＮＫ４Ａ的甲基化状态,用免疫组织化学ＳＰ方法检测p16蛋白表达情况。结果 ３８例ＬＭＳ中９例发生异常甲基化,异常甲基化率为２３.7%（９／３８）。其中,７例p16蛋白表达阴性,２例p16蛋白弱阳性,在p16蛋白表达阴性的ＬＭＳ中,异常甲基化率为５０％（７／１４）。结论 p16基因第一外显子启动子区５‘CpG岛的异常甲基化是导致p16基因失活、蛋白缺如的重要基因外机制,并可能参与肿瘤的发生。     

原发胃癌中p16和p15基因表达及甲基化异常

为检测胃癌组织中抑癌基因p16,p15及其启动子区甲基化状态和P16、P15蛋白表达情况。选择p16、p15基因及启动子区域，用PCR－SSCP、MSP（甲基化特异的PCR）和测序法对100例胃癌患者的癌组织、癌旁正常组织和5例正常组织进行检测，同时用免疫组化法检测了癌组织和正常对照组织的P16和P15的表达。结果发现癌组织p16和p15基因启动子区甲基化率显著高于癌旁正常组织和正常对照；胃癌组织中，71％的病例P16表达阴性，54％的病例具有p16基因启动子区的高甲基化，无突变和纯合缺失检出；11％的病例P15表达阴性，9％的病例具有p15基因启动子区的高甲基化，p15异常与低分化胃癌有关，p15基因内含子1和外显子1内各发现1例DNA序列改变；癌组织中p16和p15基因启动子区甲基化与其蛋白表达密切相关。结果显示p16基因启动子区域高甲基化是胃癌中p16基因失活的关键因素之一，并在胃癌的发生发展中发挥重要作用；p15基因启动子区域高甲基化在胃癌中起一定作用。     

启动子区域甲基化状态对THP-1细胞肿瘤坏死因子α分泌的影响

目的: 探讨肿瘤坏死因子α( TNF-α )基因启动子区域散在CpG双核苷酸结构甲基化状态对蛋白分泌和基因表达的影响。方法: 检测人单核细胞系THP-1细胞在脂多糖(LPS)刺激状态下,不同时点TNF-α的表达和其基因启动子区域的甲基化状态。采用ELISA法测定细胞培养液上清TNF-α水平;采用重亚硫酸盐转化基因测序法测定DNA甲基化状态。结果: 受到LPS刺激后,THP-1细胞迅速产生 TNF-α ,在4 h达到高峰后快速下降。 TNF-α 基因启动子-344 bp到转录起始位点(TSS)区域内,存在11个散在CpG双核苷酸结构。未受到LPS刺激时均处于甲基化状态;刺激4 h后,有4个处于甲基化状态;刺激8 h后,有9个处于甲基化状态。未刺激与刺激4 h之间,刺激4 h与刺激8 h之间,甲基化率比较均有显著差异(P＜0.01,P<0.05)。结论: 未受到LPS刺激时,THP-1细胞 TNF-α 基因启动子区域甲基化水平较高;LPS刺激后,其该区域甲基化水平降低。该变化与TNF-α表达分泌相关。     

Strategies for recruitment of relatives of BRCA mutation carriers to a genetic testing program in the Bahamas

The prevalence of BRCA1 and BRCA2 mutations among unselected breast cancer patients in the Bahamas is 23%. It is beneficial to advise relatives of mutation carriers that they are candidates for genetic testing. Women who test positive are then eligible for preventive interventions, such as oophorectomy. It is not clear how often relatives of women with a mutation in the Bahamas wish to undergo genetic testing for the family mutation. Furthermore, it is not clear how best to communicate this sensitive information to relatives in order to maximize patient compliance. We offered genetic testing to 202 first‐degree relatives of 58 mutation carriers. Of 159 women who were contacted by the proband or other family member, only 14 made an appointment for genetic testing (9%). In contrast, among 32 relatives who were contacted directly by the genetic counselor, 27 came for an appointment (84%). This study suggests that for recruitment of relatives in the Bahamas, direct contact by counselor is preferable to using the proband as an intermediary.     

Contribution of the BRCA1 and BRCA2 mutations to breast cancer in Tunisia

Hereditary breast cancer accounts for 3–8% of all breast cancers, with mutations in the BRCA1 and BRCA2 genes responsible for up to 30% of these. To investigate the prevalence of BRCA1 and BRCA2 gene mutations in breast cancer patients with affected relatives in Tunisia, we studied 36 patients who had at least one first degree relative with breast and/or ovarian cancer Thirty-four 34 patients were suggestive of the BRCA1 mutation and two were suggestive of the BRCA2 mutation, based on the presence of male breast cancer detected in their corresponding pedigrees. Four mutations in BRCA1 were detected, including a novel frame-shift mutation (c.211dupA) in two unrelated patients and three other frameshift mutations – c.4041delAG, c.2551delG and c.5266dupC. Our study is the first to describe the c.5266dupC mutation in a non-Jewish Ashkenazi population. Two frameshift mutations (c.1309del4 and c.5682insA) were observed in BRCA2. Nineteen percent (7/36) of the familial cases had deleterious mutations of the BRCA1 or BRCA2 genes. Almost all patients with deleterious mutations of BRCA1 reported a family history of breast and/or ovarian cancer in the index case or in their relatives. Our data are the first to contribute to information on the mutation spectrum of BRCA genes in Tunisia, and we give a recommendation for improving clinical genetic testing policy.     

非小细胞肺癌中窖蛋白1基因的蛋白表达和甲基化及其意义

目的 检测窖蛋白1(Car-1)在非小细胞肺癌(NSCLC)中的蛋白表达以及启动子的甲基化状况,探讨Cav-1基因在NSCLC中的作用及其临床意义.方法 应用免疫组织化学(sP法)和量子点Qd600染色检测123例NSCLC组织、17例良性病变肺组织中Cav一1蛋白表达和亚细胞定位.亚硫酸氢钠处理DNA,甲基化特异性PCR(MSP)检测Cav-1基因启动子区域的甲基化水平.结果 Cav-1蛋白在肺支气管黏膜上皮细胞、肺泡上皮细胞、毛细血管内皮细胞、成纤维细胞、平滑肌细胞的胞质和胞膜高表达.癌旁组织(对照)组和肺癌组中Cav-1蛋白的阳性率分别为17/17、43.1%(53/123),两组间差异有统计学意义(P=0.001);Cav-1蛋白在NSCLC不同的组织学类型(P=0.552)和分化程度(P=0.160)中差异均无统计学意义.Cav-1蛋白阳性率与NSCLC的TNM分期(P=0.001)以及淋巴结转移(P=0.001)均相关.在40例Cav-1蛋白表达为阴性的肺癌组织和12例癌旁肺组织,MSP法均未检测到Cav-1因启动子区域的甲基化.结论 Cav-1蛋白失表达的机制可能与启动子区是否甲基化无关.Cav-1蛋白高表达预示NSCLC恶化进展和高侵袭性.     

人脑神经胶质瘤中p16、p21~(WAF1/CIP1)蛋白表达的研究

目的　探讨 p16、p2 1WAF1/CIP1两种抑癌基因与人脑神经胶质瘤恶性程度的关系。方法　采用SABC免疫组织化学方法对 6 4例人脑胶质瘤组织及 8例正常脑组织标本中p16和 p2 1WAF1/CIP1表达情况进行检测 ,并进行相关分析。结果　①p16和 p2 1WAF1/CIP1阳性表达率在人脑胶质瘤中分别为 4 5 .3%和 6 4 .1%与正常脑组织中的表达情况差异显著 (P <0 0 5 ) ;②p16蛋白和 p2 1WAF1/CIP1蛋白阳性表达率均随着胶质瘤的恶性程度的增高而降低 ,差异显著 (P <0 0 1) ,且呈负相关关系 ;③p16蛋白和 p2 1WAF1/CIP1蛋白可协同表达 ,且在正常脑组织和脑胶质瘤各分级中 p16蛋白和 p2 1WAF1/CIP1蛋白协同表达率差异显著 (P <0 0 5 ) ,并呈负相关关系。结论　p16与p2 1WAF1/CIP1蛋白的阳性表达率及协同表达率可在一定程度上反映胶质瘤细胞的恶性程度 ,可作为判断其恶性程度的有效指标