BRCA1基因的功能及其上游调控序列结构功能特征

乳腺癌易感基因1(BRCA1)是一种与家族性乳腺癌、家族性卵巢癌密切相关的抑癌基因.但其在散发性乳腺癌中尚未见突变的报道,而在散发性乳腺癌中其表达下降,说明其转录调控异常可能参与散发性乳腺癌的发生.本文拟对BRCA1功能及上游调控区结构功能特征作一综述.     

乳腺癌组织BRCA1、BRCA2基因区域杂合性缺失的研究

目的　研究乳腺癌组织BRCA1、BRCA2基因区域的杂合性缺失 (LOH)情况。方法　采用聚合酶链式反应(PCR)和聚丙烯酰胺凝胶电泳 ,对 30例散发性乳腺癌和 2例姐妹乳腺癌进行LOH的检测 ,同时还采用G显带法对姐妹乳腺癌患者的外周血淋巴细胞染色体畸变情况进行分析。结果　在散发性乳腺癌中 ,BRCA1、BRCA2基因区域的杂合性缺失率分别为 6 12 %和 5 77% ;姐妹二人乳腺癌组织在BRCA2基因区域的D13S173位点处存在LOH ,且她们的外周血淋巴细胞发生了大量的稳定性和非稳定性畸变 ,畸变率远远高于自发畸变率。结论　乳腺癌易感机理在东西方种族有可能存在差异 ,应深入进行研究     

家族性与散发性乳腺癌BRCA1与FANCD2基因相关性的研究

目的:探讨乳腺癌组织BRCA1与FANCD2基因表达,明确BRCA1基因与FANCD2基因之间的相关性.方法:选取104例乳腺癌手术标本,其中家族性乳腺癌52例,散发性乳腺癌52例.采用SP免疫组化法检测BRCA1和FANCD2在家族和散发性乳腺癌组织中的表达.结果:在家族性乳腺癌组织中,BRCA1蛋白阳性表达37例(71.2％),FANCD2蛋白阳性表达18例(34.6％),两组差异有统计学意义,P＜0.05.在散发性乳腺癌组织中,BRCA1蛋白阳性表达19例(36.5％),FANCD2蛋白阳性表达27例(51.9％),两组差异无统计学意义.结论:BRCA1和FANCD2基因表达与乳腺癌的发生和发展存在一定相关性,FANCONI/BRCA 通路的抑制,可能是乳腺癌,尤其是家族性乳腺癌发生发展以及形成的原因之一.     

新疆维吾尔族女性散发性乳腺癌组织中BRCA1、C-erBb-2的表达分析及其临床意义

背景与目的:维吾尔族有着不同于汉族的遗传背景,目前国内对维吾尔族女性散发性乳腺癌组织中BRCA1、C-erBb-2的研究少有报道.本研究旨在探讨BRCA1、C-erBb-2在新疆维吾尔族女性散发性乳腺癌中的表达特点及其临床意义.方法:应用组织芯片技术及免疫组织化学方法榆测190例新疆维吾尔族女性乳腺癌组织中BRCA1、C-erBb-2的表达,以100例汉族女性乳腺癌及30例维吾尔族女性乳腺良性肿瘤患者作为对照,分析二者表达的特点和相关性及其与临床病理参数间的关系.结果:新疆维吾尔族、汉族女性散发性乳腺癌组织和维吾尔族女性良性乳腺疾病组织中BRCA1表达阳性率分别为62.1%、28.9%和86.7%,维、汉两民族女性乳腺癌组间差异有统计学意义(P<0.05);维吾尔族女性与汉族女性散发性乳腺癌组织中C-erBb-2的阳性表达差异无统计学意义(26.0%:22.0%,P>0.05);蛋白表达相关分析显示维、汉两民族女性乳腺癌组织中C-erBb-2的表达和BRCA1的表达呈负相关关系(P<0.05);维吾尔族女性散发性乳腺癌组织中BRCA1阳性表达与肿瘤分期、淋巴结转移情况有关(P<0.05);C-erBb-2在肿瘤大小、肿瘤分期、淋巴结转移情况、PR状况方面其阳性表达之问差异有统计学意义(P<0.05).结论:新疆地区维、汉女性散发性乳腺癌及维吾尔族女性乳腺良性肿瘤组织中BRCA1和C-erBb-2表达均存在显著差异,且维、汉女性乳腺癌组织中BRCA1的阳性表达显示有种族差异性,临床常规联合监测BRCA1和C-erBb-2,有助于指导患者合理治疗和评价预后.     

新疆维汉妇女散发性乳腺癌组织中HER-2BRCA1和BRCA2蛋白表达及其相关性研究

目的:探讨HER-2、BRCA1和BRCA2在新疆地区维、汉妇女散发性乳腺癌中的表达及其之间表达相关性.方法:采用组织芯片、免疫组化方法检测各100例新疆地区维、汉妇女散发性乳腺癌组织中及30例维吾尔族妇女乳腺良性肿瘤组织中HER-2、BRCA1和BRCA2的表达,分析其表达之间的相关性及其与临床病理参数间关系.结果:HER-2、BRCA1和BRCA2蛋白在新疆维、汉族妇女散发性乳腺癌组织中的表达分别为35.0%、49.0%、50.0%和22.0%、26.0%、26.0%,在维吾尔族妇女良性乳腺疾病组织中表达分别为100%、86.7%和83.3%,均存在显著差异(P<0.05).蛋白表达相关分析显示维吾尔族妇女乳腺癌组织中,HER-2、BRCA1和BRCA2表达间不存在相关性.而汉族妇女乳腺癌组织中当HER-2和BRCA2均阴性表达时,BRCA1失表达率最高,存在显著正相关(r=0.344,P<0.01).蛋白表达与临床病理资料分析表明:相对于汉族妇女乳腺癌,BRCA1蛋白表达缺失在新疆维吾尔族妇女早发性乳腺癌中明显增加,并且随患者腋窝淋巴结转移数目增多、分期增加而显著增加(P<0.05).HER-2表达在绝经和非绝经组间其阳性表达存在显著差异(P<0.05),BRCA2蛋白表达与各参数均无关.结论:新疆地区维、汉妇女散发性乳腺癌及维吾尔族妇女乳腺良性肿瘤组织中HER-2、BRCA1和BRCA2表达均存在显著差异,维族妇女乳腺癌组织中BRCA1、BRCA2和HER-2蛋白均独立表达,而汉族妇女乳腺癌组织中BRCA1、BRCA2表达存在明显相关性,尤其当HER-2阴性表达时.BRCA1失表达提示肿瘤恶性程度较高和预后较差,可能在乳腺良恶性病变转化及乳腺癌的发生过程中具有重要作用,结合HER-2、BRCA2的表达状况,可以做为判断乳腺癌患者预后的重要指标之一,有助于指导病人治疗方案的改进和合理性选择.     

中国湖南家族性和早发性乳腺癌BRCA1和BRCA2基因突变分析

背景与目的:BRCA1和BRCA2基因是已经证实的乳腺癌遗传易感基因,与家族性及早发性乳腺癌密切相关.本研究旨在分析中国湖南省家族性和早发性乳腺癌中BRCA1和BRCA2基因的突变位点及携带情况.方法:以来自湖南地区的50例家族性和早发性乳腺癌(发病年龄≤35岁)为研究对象,其中26例(52%)有乳腺痛家族史.由静脉血提取基因组DNA,对BRCA1和BRCA2基因的全部编码序列进行扩增.突变分析由变性高效液相色谱分析(DHPLC)进行预筛,之后进行DNA测序证实.结果:在50例乳腺癌患者中发现有5种致病性突变,其中2种为新发现突变--BRCA2基因无义突变2372C>G和移码突变2808delACAA.BRCA1基因中发现一种已报道的无义突变220C>T;其他两种为已报道的BRCA2移码突变位点1796delTTTAT和6275delTT.我们还发现4个未知功能的突变位点(UV)及11个基因多态性位点.湖南家族性乳腺癌中BRCA1突变率4%低于BRCA2突变率16%. 结论:在中国湖南人群中,BRCA2基因的突变对于遗传性乳腺癌的发生可能具有较重要意义:新发现的2个突变位点可能是中国人群中的特有突变;湖南地区BRCA1在家族性乳腺癌中突变率明显低于国内外报道,而BRCA2突变发生率与西方国家相近,但明显高于国内其他地区,这可能是中国湖南人群中的特有特征.     

散发性乳腺癌患者BRCA1基因突变分析

目的：探讨BRCA1基因突变在散发性乳腺癌发生和发展中的作用及在乳腺癌临床诊断和治疗中的应用前景。方法：应用PCR-SSCP和直接测序法检测30例散发性乳腺癌和15例正常乳腺组织中RRCA1基因外显子2、11和20的突变情况。结果：15例正常乳腺组织在3个外显子上郜未显示电泳异常．30例乳腺癌中有6例在外显子2上显示电泳条带异常．其中4例经测序证实有突变，1例在外显子2上，3例在内含子拼接区。BRCA1基因突变率在初诊年龄、临床分期和肿瘤体积上差异无统计学意义．但与肿瘤转移密切相关。结论：BRCA1基因突变与散发性乳腺癌的发生和发展密切相关，该基因突变筛查可作为一种预后指标。     

人鼻咽癌紫杉醇耐药细胞系与其亲代细胞系比较基因组杂交研究

目的:比较基因组杂交(comparative genomic hybridization,CGH)是一种在荧光原位杂交(fluorescence in situ hybridization,FISH)技术上发展起来的用于检测两个基因组间相对DNA拷贝数的改变(缺失或扩增),并将这些变化在染色体上进行定位的分子细胞遗传学方法.为了解鼻咽癌紫杉醇耐药细胞(CNE1/Taxol,HNE2/Taxol,5-8F/Taxol)与亲代细胞(CNE1,HNE2,5-8F)在基因组DNA水平上可能存在的差异,以及这种差异在肿瘤获得性耐药产生中的意义,采用CGH技术对鼻咽癌紫杉醇耐药细胞与亲本细胞的基因组DNA进行检测和分析.方法:三株鼻咽癌紫杉醇耐药细胞采用大剂量冲击与剂量逐渐递加相结合的方法诱导而成.采用集落形成实验测定药物的敏感性,利用比较基因组杂交技术(CGH)对耐药细胞和其亲本细胞的基因组DNA进行检测和分析,比较耐药细胞与亲本细胞在染色体扩增与缺失上的共同点和差异.结果:三株鼻咽癌紫杉醇耐药细胞耐药指数分别为8.43、8.27和5.26.鼻咽癌亲本细胞存在广泛的染色体改变,主要表现在3q21-qter,5p13-pter,12和20q11-qter的共同扩增以及10q11-qter,18和X染色体的共同缺失,从亲本细胞系诱导的三株鼻咽癌紫杉醇耐药细胞系表现为3q21-qter,5p13-pter,12,20q11-qter和8q21-qter的共同扩增,无明显共同缺失区域.与亲本细胞共同扩增区域相比,其中最有意义的是8q21-qter区域在三株耐药细胞中出现了新的共同扩增.结论:3q21-qter,5p13-pter,12和20q11-qter的共同扩增以及10q11-qter,18和X染色体的共同缺失可能与鼻咽癌的发生有关,而8q21-qter染色体扩增可能与鼻咽癌获得性紫杉醇耐药相关,对这些区域的进一步研究,有可能为肿瘤发生及耐药机制研究提供新的线索.     

卵巢癌顺铂耐药细胞系及其亲代细胞的比较基因组杂交研究

目的：探讨人卵巢癌顺铂耐药细胞株COC1/DDP及其药物敏感细胞株COC1在基因组DNA水平上可能存在的差异,以及这种差异在肿瘤耐药性产生中的意义.方法：采用比较基因组杂交技术分析COC1和COC1/DDP两组癌细胞间基因组的不平衡,即DNA丢失或扩增.结果：COC1细胞系具有广泛的染色体改变,染色体出现扩增的有1p21-31、2q14-24、3q25-29、8q22-24、12p11-12、19p12q12、20q12-13,出现缺失的染色体有4、13q22-31、18q12-21.COC1/DDP细胞系也有较广泛的染色体改变,出现扩增的有6q21-24、17q21-25、18q21-23,出现缺失的有10q11-22、16q12-22、17p11-12.结论：卵巢癌耐药及亲本细胞中存在着广泛的染色体变异,其中6q、17q、18q、10q、16q、17p中的一些已知或未知基因可能参与COC1/DDP耐药性的产生.     

原发性肺癌肿瘤组织染色体变异比较基因组杂交分析

目的：分析原发性肺癌肿瘤组织染色体异常变化，了解肺癌组织染色体畸变规律。方法：应用比较基因组杂交技术分析55例原发性肺癌患者肿瘤组织染色体结果：原发性肺鳞癌常见染色体扩增区是2q、5p、11q、22q，常见缺失区是1p、4q、5q、6q、8p、9p、10q、11p、13q、18q、21q。肺腺癌常见扩增区是5p、8q、11q，常见缺失区是10p、19。腺鳞癌、肺泡细胞癌、小细胞癌等染色体变化各有不同。结论：原发性肺癌存在广泛的遗传物质不平衡现象．不同病理分型的染色体基因扩增和缺失可能是其发生、发展的基础。     

Amplification of the BRCA2 pathway gene EMSY in sporadic breast cancer is related to negative outcome.

DNA amplification at band q13 of chromosome 11 is common in breast cancer, and CCND1 and EMS1 remain the strongest candidate genes. However, amplification patterns are consistent with the existence of four cores of amplification, suggesting the involvement of additional genes. Here we present evidence strongly suggesting the involvement of the recently characterized EMSY gene in the formation of the telomeric amplicon. EMSY maps at 11q13.5, 100 kb centromeric to the GARP gene, which has been mapped within the core of the distal amplicon. The EMSY protein was shown to interact with BRCA2 and has a role in chromatin remodeling. This makes EMSY a strong candidate oncogene for the 11q13.5 amplicon. DNA amplification was studied in a total of 940 primary breast tumors and 39 breast cancer cell lines. Amplification profiles were consistent with the EMSY-GARP locus being amplified independently of CCND1 and/or EMS1. EMSY RNA expression levels were studied along with those of five other genes located at 11q13.5 by real-time quantitative PCR in the 39 cell lines and a subset of 65 tumors. EMSY overexpression correlated strongly with DNA amplification in both primary tumors and cell lines. In a subset of 296 patients, EMSY amplification was found by both uni- and multivariate analyses to correlate with shortened disease-free survival. These data indicate that EMSY is a strong candidate oncogene for the 11q13.5 amplicon.     

Genomic instability of human mammary epithelial cells overexpressing a truncated form of EMSY

The EMSY gene encodes a protein that interacts with Brca2 and is amplified in some sporadic cases of human breast cancer. To examine whether overexpression of EMSY would mimic the chromosome instability phenotype that is associated with the loss of Brca2 function, we constructed a lentiviral vector (Lenti-EMSY/GFP) that encodes a truncated form of the Emsy protein, including its Brca2-interacting domain, and green fluorescent protein (GFP) and used it to transduce human telomerase-immortalized human breast epithelial (184-hTert) cells, which have a nearly normal karyotype. At passage 5 after transduction, 39 (26%) of 150 EMSY/GFP-transduced metaphase cells contained at least one structural chromosomal abnormality compared with 19 (13%) of 150 GFP-transduced metaphase cells (P = .003, chi-square test); at passage 10, the corresponding frequencies were 42% and 15%, respectively (P < .001). Mitomycin C also produced a severalfold higher frequency of chromosome breaks in the EMSY/GFP-transduced cells than in the control cells. These results support the hypothesis that EMSY overexpression can play a role in the genesis of human breast cancer.     

Molecular-cytogenetic analysis of HER-2/neu gene in BRCA1-associated breast cancers

The BRCA1 tumor suppressor gene and the HER-2/neu oncogene are located in close proximity on the long arm of chromosome 17 (17q11-21). Absence of BRCA1 or functional overexpression of the HER-2/neu gene presumably contributes to the somatic phenotype of breast cancer in premenopausal women, characterized by unfavorable prognostic features such as high tumor grade, hormone receptor negativity, and high proliferation rate. To examine whether amplification of HER-2/neu contributes to the aggressive biology of BRCA1-associated tumors, we have performed fluorescence in situ hybridization on formalin-fixed paraffin-embedded breast tumor tissue sections from 53 BRCA1 mutation carriers and 41 randomly selected, age-matched sporadic breast cancer cases. Although BRCA1-associated and sporadic tumors were equally likely (19% versus 22%) to exhibit HER-2/neu amplification [defined as a ratio of HER-2/neu copies to chromosome 17 centromere (CEP17) copies > or = 2], 6 (15%) of the sporadic tumors were highly amplified (defined as a ratio greater-than-or-equal 5) versus none of the BRCA1-associated tumors (P = 0.048). HER-2 protein overexpression as measured by immunohistochemical analysis was not observed among the BRCA1-associated cases (P = 0.042). Four of 21 (19%) sporadic tumors exhibited strong membranous staining of HER-2 (intensity level of 3+) as compared with 0 of 39 BRCA1-associated tumors. Our data suggest that a germ-line mutation in the BRCA1 tumor suppressor gene is associated with a significantly lower level of HER-2/neu amplification. Thus, it is possible that BRCA1-associated and HER-2/neu-highly amplified tumors progress through distinct molecular pathways, and the aggressive pathological features of BRCA1-associated tumors appear unrelated to amplification of the adjacent HER-2/neu oncogene.     

Loss of heterozygosity in sporadic breast tumours at the BRCA2 locus on chromosome 13q12-q13.

Loss of heterozygosity (LOH) on chromosome 13 occurs on 25-30% of breast tumours. This may reflect the inactivation of the retinoblastoma susceptibility gene RB1. However, recently another candidate tumour-suppressor gene has been identified on chromosome 13 by linkage analysis, the breast cancer susceptibility gene BRCA2. To investigate the involvement of BRCA2 in sporadic breast cancer 200 breast tumours were tested for LOH on chromosome band 13q12-q14, using 11 highly polymorphic microsatellite markers. LOH was found in 65 tumours, which all showed simultaneously loss of BRCA2 and RB1. Of 12 breast tumour cell lines tested with polymorphic microsatellite markers, seven showed a contiguous region of homozygosity on 13q12-q14, suggesting LOH in the tumour from which the cell line had been derived. One cell line showed homozygosity in the BRCA2 region and heterozygosity at RB1. This is the only indication that BRCA2 is a distinct target for LOH on chromosome 13 in addition to RB1.     

The function of EMSY in cancer development

EMSY was first reported to bind BRCA2 and to inactivate the function of BRCA2, leading to the development of sporadic breast and ovarian cancers. The function of EMSY may also be involved in DNA damage repair, genomic instability, and chromatin remolding. Recent studies have shown that amplification of EMSY was also associated with other cancers such as prostate and pancreatic cancers and linked to tumor phenotypes and clinical outcomes. By reviewing literatures published since 2003, here, we have summarized the recent advances of EMSY in cancer development.     

Expression of EMSY,a Novel BRCA2-link Protein,is Associated with Lymph Node Metastasis and Increased Tumor Size in Breast Carcinomas

Background: The EMSY gene encodes a BRCA2-binding partner protein that represses the DNA repairfunction of BRCA2 in non-hereditary breast cancer. Although amplification of EMSY gene has been proposed tohave prognostic value in breast cancer, no data have been available concerning EMSY tissue expression patternsand its associations with clinicopathological features. Materials and Methods: In the current study, we examinedthe expression and localization pattern of EMSY protein by immunohistochemistry and assessed its prognosticvalue in a well-characterized series of 116 unselected breast carcinomas with a mean follow up of 47 monthsusing tissue microarray technique. Results: Immunohistochemical expression of EMSY protein was detected in76% of primary breast tumors, localized in nuclear (18%), cytoplasmic (35%) or both cytoplasmic and nuclearsites (23%). Univariate analysis revealed a significant positive association between EMSY expression and lymphnode metastasis (p value=0.045) and larger tumor size (p value=0.027), as well as a non-significant relation withincreased risk of recurrence (p value=0.088), whereas no association with patients’ survival (log rank test, pvalue=0.482), tumor grade or type was observed. Conclusions: Herein, we demonstrated for the first time theimmunostaining pattern of EMSY protein in breast tumors. Our data imply that EMSY protein may have impacton clinicipathological parameters and could be considered as a potential target for breast cancer treatment.     

EMSY links breast cancer gene 2 to the 'Royal Family'

Although the role of the breast cancer gene 2 (BRCA2) tumor suppressor gene is well established in inherited breast and ovarian carcinomas, its involvement in sporadic disease is still uncertain. The recent identification of a novel BRCA2 binding protein, EMSY, as a putative oncogene implicates the BRCA2 pathway in sporadic tumors. Furthermore, EMSY's binding to members of the 'Royal Family' of chromatin remodeling proteins may lead to a better understanding of the physiological function of BRCA2 and its role in chromatin remodeling.     

Characterisation of amplification patterns and target genes at chromosome 11q13 in CCND1-amplified sporadic and familial breast tumours

Amplification of chromosomal region 11q13, containing the cell cycle regulatory gene CCND1, is frequently found in breast cancer and other malignancies. It is associated with the favourable oestrogen receptor (ER)-positive breast tumour phenotype, but also with poor prognosis and treatment failure. 11q13 spans almost 14 Mb and contains more than 200 genes and is affected by various patterns of copy number gains, suggesting complex mechanisms and selective pressure during tumour progression. In this study, we used 32 k tiling BAC array CGH to analyse 94 CCND1-amplified breast tumours from sporadic, hereditary, and familial breast cancers to fine map chromosome 11q13. A set containing 281 CCND1-non-amplified breast tumours was used for comparisons. We used gene expression data to further validate the functional effect of gene amplification. We identified six core regions covering 11q13.1-q14.1 that were amplified in different combinations. The major core contained CCND1, whereas two cores were found proximal of CCND1 and three distal. The majority of the CCND1-amplified tumours were ER-positive and classified as luminal B. Furthermore, we found that CCND1 amplification is associated with a more aggressive phenotype within histological grade 2 tumours and luminal A subtype tumours. Amplification was equally prevalent in familial and sporadic tumours, but strikingly rare in BRCA1- and BRCA2-mutated tumours. We conclude that 11q13 includes many potential target genes in addition to CCND1.