中国上海家族性乳腺癌BRCA1和BRCA2基因的突变

目的研究上海地区家族性乳腺癌中BRCA1／BRCA2基因的突变位点及携带情况。方法研究对象来自35个汉族家族性乳腺癌家系，家系中至少有一个一级亲属乳腺癌患病史。共35例患者，其中13例发病年龄≤加岁。由静脉血提取基因组DNA，对BRCA1／BRCA2基因的全部编码序列进行扩增。扩增产物突变分析先由变性高效液相色谱分析进行筛查，之后进行DNA直接测序证实。结果在BRCA1基因中发现有4个突变位点，其中2个为新发现位点——拼接点突变（IVS17-1G〉T；IVS21＋1G〉C）；另两个为已报道的致病突变位点——移码突变（1100delAT；5640delA）。BRCA2基因的1个致病突变位点位于11号外显子上，为移码突变（5802delAATT）。另外，共发现有12个新的单核苷重复多态位点，都未引起氨基酸编码改变；其中，8个在BRCA1基因上，4个在BRCA2基因上。在家族性乳腺癌中，BRCA1突变频率（11．4％）高于BRCA2基因（2．9％）。结论新发现的2个BRCA1基因的拼接点突变可能是中国上海人群家族性乳腺癌的特有突变位点；在我国上海地区人群中，BRCA1基因突变起着比BRCA2基因更大的作用；该研究丰富了中国人群中BRCA基因的突变谱，并为未来的临床基因检测提供了筛查模式。     

山东半岛地区家族性和早发性乳腺癌BRCA2基因突变研究

目的 研究山东半岛地区家族性和早发性乳腺癌中乳腺癌易感基因BRCA2的突变位点及携带情况.方法 应用PureGene DNA纯化系统提取52例家族性和早发性乳腺癌患者的外周血单核细胞DNA,对BRCA2基因的全部编码序列及内含子和外显子拼接区进行扩增,扩增产物用变性高效液相色谱进行初筛,对发现异常片段经重新扩增后进行DNA测序证实.结果 在52例乳腺癌患者中发现3个(5.8%)BRCA2的致病性突变(2001delTTAT,4099＞T,5873C＞A).其中,家族性乳腺癌突变率达到12%(3/25),在单纯早发性乳腺癌病例中未发现致病性突变.结论 在家族性乳腺癌患者中,BRCA2基因突变可能具有重要作用,在此人群中有必要进行相关的基因检测.     

CYP19A1基因 R264C在中国上海BRCA1/2基因突变阴性的遗传倾向乳腺癌中的作用

目的研究CYP19A1基因R264C的（C→T）单核苷酸多态性基因型在上海地区BRCA1／BR-CA2基因突变阴性的遗传倾向乳腺癌人群中的分布及其与乳腺癌发病风险的相关性。方法对114例无BRCA1／2突变的家族性／早发性乳腺癌患者和121名正常对照者进行CYP19A1基因第7外显子的聚合酶链反应扩增，随后进行DNA直接测序鉴定其R264C的单核苷酸多态性基因型，比较基因型分布和发病风险的关系；危险度比值比（odd ratio，OR）及95％可信区间（confidence interval，CI）应用非条件Logistie回归分析计算。结果CYP19A1基因R264C多态的CC、CT、TT基因型在病例组中的分布频率分别为84（77．8％），22（20．4％），2（1、8％）；在对照组的分布频率分别为87（77．7％），24（21、4％），1（0．9％）；在研究的总人群中，CT基因型的频率为20．9％（46／220），TT基因型的频率为1．4％（3／220）。以CC基因型为参照，CT或TT基因型没有显著性地提高乳腺癌的发病危险，其中携带CT基因型风险为（OR=1．16，95％CI：0．53。2．55），携带TT基因型风险为（OR=1．44，95％CI：0．12-17．15）；经过月经状态和身体质量指数分层，也未能发现其与乳腺癌发病的相关性。结论CYP19A1基因R264C的单核苷酸多态性在中国汉族人群中的分布有别于其他种族，有其自身的分布特点；R264C可能与上海地区中国汉族人群乳腺癌发生的遗传易感性无关，尚不足作为低外显率的乳腺癌易感基因位点，不建议作为未来临床基因筛查的候选指标。     

中国乳腺癌患者BRCA1基因的频发突变5589del8

目的研究在中国大陆乳腺癌人群中是否存在BRCAI／2基因突变的“热点”。方法研究对象为来自全国4个乳腺癌医疗中心的177例家族性和早发性乳腺癌患者和426例散发性乳腺癌患者,根据前期研究中已发现的BRCAI／2基因突变位点,应用变性高效液相色谱分析和DNA测序技术对这些患者进行已知位点的突变检测。结果在前期研究的70例家族性和早发性乳腺癌患者和本研究的177例患者（共247例）中,共发现3例BRCAl5589del8突变的携带者,在426例散发性乳腺癌患者中也发现了2例BRCAl5589del8突变的携带者。单倍型分析的结果显示这5例患者具有相近甚至相同的单倍型。结论BRCAl5589del8突变是中国人群中BRCAl基因的频发突变,它是否是中国人群中的“始祖突变”仍需进一步研究证实。     

忻州地区耳聋患者常见耳聋基因GJB2、GJB3和线粒体DNA 12S rRNA 1555A〉G相关性分析

目的通过对忻州地区83例耳聋患者常见基因GJB2、GJB3和线粒体DNA 12S rRNA 1555A〉G测序分析,从分子水平研究该地区人群聋病的遗传病因和特点,为临床防聋治聋提供策略、依据。方法收集忻州地区83例耳聋患者外周血样本,提取DNA后对目的基因扩增并进行测序分析。结果83例耳聋患者中GJB2基因检测到57例发生突变,9个突变位点,与编码连接蛋白的非综合症耳聋突变数据库（http：／／davinci．crg．OS／deafneSS／index．php？Seccion=mut_db＆db=nonsynd）比对,8个位点已见报道,其中包括3个多态位点c．79G〉A、c．341A〉G、c．368C〉A和5个致病位点c．235delC、c．30-35delC、c．109G〉A、c．176-c．191dell6和c．299-c．300delAT,其中,c．79G〉A和c．341A〉G是主要突变方式,携带率为30．12％（42／174）和23．49％（39／166）。新发现1例未见报道的突变位点c．186C〉T;患者均未检测出GJB3和线粒体DNA12SrRNA1555A〉G基因突变位点。结论通过对忻州地区常见耳聋基因突变位点的研究,了解忻州地区该基因突变谱,为后续国内耳聋基因型分布提供数据支持,同时也为耳聋的早期诊断、治疗提供理论依据。     

小睑裂综合征家系的FOXL2基因突变研究

目的 对小睑裂综合征家系患者的FOXL2基因突变进行研究，寻找突变位点。方法 设计FOXL2基因特异性引物进行PCR扩增，然后测序，并对突变位点进行克隆后测序。结果 在一个类型尚不明确的家系中2例患者FOXL2基因PCR扩增后测序发现951—953（delc），克隆后多克隆位点测序亦证实951—953（delC）。所有正常人均未发现突变。951—953（delC）引起238位S后出现移码突变，终止密码子提前，蛋白截短。结论 951－953（delC）致蛋白截短，可能是导致小睑裂综合征的原因。经查新验证．951－953（delC）是一个新的突变位点，国内外未见报道。     

一个遗传性非综合征型耳聋家系的突变分析

目的分析一个遗传性非综合征型耳聋家系的突变，并探讨缝隙连接蛋白beta2(gap junction protein beta 2，GJB2)基因235delC突变是否会加重线粒体A1555G突变导致的非综合征型耳聋症状。方法对一个母系遗传性非综合征型耳聋核心家系72个成员取外周血提取DNA，经聚合酶链反应扩增后，利用Alw26Ⅰ限制性内切酶酶切及直接测序验证，对其线粒体DNA突变进行研究；利用ApaⅠ限制性内切酶酶切及直接测序验证，筛查核心家系中GJB2基因235delC突变情况，并对GJB2基因235delC和线粒体A1555G突变的关系进行研究。结果在27名母系成员中均发现具有线粒体A1555G突变，呈母系遗传；具有耳聋表型的为21人(77．8％)，家族外显率高；所筛查的包括配偶在内的72名个体中，仅3例具有GJB2基因235delC杂合子突变，且均出现在母系成员中，但3例的耳聋表型却不同。结论线粒体A1555G突变是本家系耳聋遗传易感性的基础，在该家系中GJB2基因的235delC杂合子突变未加重线粒体A1555G突变导致的非综合征型耳聋。     

中国广东人CYP2F1基因遗传多态性研究

目的检测广东地区正常人群和鼻咽癌患者中细胞色素P450酶系CYP2F1基因的多态性，并分析该基因遗传多态性与鼻咽癌易感性的关联。方法采用直接测序法检测40例鼻咽癌患者全血标本中CYP2F1基因全部10个外显子的多态性变化。对于等位基因频率较高的多态性位点，进一步采用错配聚合酶链反应．限制性片段长度多态性检测368例鼻咽癌患者和344名正常对照人群中该位点的等位基因频率。结果在40例鼻咽癌样本中，共检测到CYP2F1基因的35个单核苷酸多态性。其中，10个单核甘酸引起编码的氨基酸改变，1个移码突变，15～16bp之间插入C引起移码突变（15-16ins C），该等位基因频率为25％。但病例-对照分析却未能显示该位点突变与鼻咽癌易感的相关性（P〉0．05）。结论中国广东人的CYP2F1基因遗传多态性位点较多，但暂未发现与鼻咽癌的易感性关联的单一多态位点，多个多态性位点或不同基因多态性位点的协同互补作用可能才是鼻咽癌发生发展的关键影响因素。     

维吾尔族和汉族散发性乳腺癌患者BRCA1/2基因突变的检测

目的探讨新疆维吾尔族和汉族散发性乳腺癌患者乳腺癌易感基因1/2(BRCA1/2)突变情况及与临床病理参数的关系。方法采用PCR和DNA直接测序法,对新疆地区230例散发性乳腺癌患者(维吾尔族、汉族各115例)石蜡组织进行BRCA1基因第2、11(11A和11B)、20号外显子和BRCA2基因第11号部分外显子,共5对引物进行突变检测。结果 230例乳腺癌患者中,BRCA基因突变率为6.96%(16/230),其中1例BRCA1基因-5 382位点的突变及7例新发突变位点;维吾尔族和汉族患者中BRCA基因突变检出率分别为7.83%(9/115)和6.09%(7/115);BRCA基因突变组发病年龄均≤50岁;突变组16例患者中绝经前患者(13例)的突变率明显高于绝经后患者(3例)(P0.05)。结论 BRCA1基因突变可能与新疆地区散发性乳腺癌发生相关。     

中国乳腺癌患者BRCA1基因突变的研究

目的　在中国乳腺癌患者 BRCA1基因外显子 2、2 0和 11部分序列中寻找突变位点 ,探讨其与乳腺癌发病的关系。方法收集 86例无血缘关系的乳腺癌患者 ,用聚合酶链反应 -双链四色荧光标记的方法 ,分析 BRCA1基因的外显子 2和 2 0的全长序列和外显子 11的部分序列。结果　外显子 2、2 0和 11的序列中均未发现有突变 ,仅在外显子 11A的序列上有一个 C/ T多态 ,基因型频率高达 4 2 %。对这个高频单核苷酸多态 (single nucleotide ploymorphism,SNP)位点 ,先作了 Hardy- Weinberg检测 ,P>0 .0 5 ,确定这个 SNP的频率不受杂合性缺失的影响。再进行 χ2检测 ,与正常对照组进行比较 ,P>0 .1,两者差异无显著性。结论　这个高频 SNP位点与乳腺癌的发生无显著相关 ;在中国人群中没有发现其他乳腺癌患者人群中普遍存在的这几个突变热点 ,说明外显子 2、2 0和 11上的这部分序列对中国人群的乳腺癌发生影响不大。     

BRCA1 mutations in Algerian breast cancer patients: high frequency in young, sporadic cases

Breast cancer rates and median age of onset differ between Western Europe and North Africa. In Western populations, 5 to 10 % of breast cancer cases can be attributed to major genetic factors such as BRCA1 and BRCA2, while this attribution is not yet well defined among Africans. To help determine the contribution of BRCA1 mutations to breast cancer in a North African population, we analysed genomic DNA from breast cancer cases ascertained in Algiers. Both familial cases (at least three breast cancers in the same familial branch, or two with one bilateral or diagnosed before age 40) and sporadic cases less than 38 years of age were studied. Complete sequencing plus quantitative analysis of the BRCA1 gene was performed. 9.8 % (5/51) of early-onset sporadic and 36.4 % (4/11) of familial cases were found to be associated with BRCA1 mutations. This is in contrast 10.3 % of French HBOC families exhibiting a BRCA1 mutation. One mutation, c.798_799delTT, was observed in two Algerian families and in two families from Tunisia, suggesting a North African founder allele. Algerian non-BRCA1 tumors were of significantly higher grade than French non-BRCA tumors, and the age at diagnosis for Algerian familial cases was much younger than that for French non-BRCA familial cases. In conclusion, we observed a much higher frequency of BRCA1 mutations among young breast cancer patients than observed in Europe, suggesting biological differences and that the inclusion criterea for analysis in Western Europe may not be applicable for the Northern African population.     

The contribution of founder mutations to early-onset breast cancer in French-Canadian women

In an ethnically‐homogeneous population, it is valuable to identify founder mutations in cancer‐predisposing genes. Founder mutations have been found in four breast‐cancer‐predisposing genes in French‐Canadian breast cancer families. The frequencies of the mutant alleles have been measured neither in a large series of unselected breast cancer patients from Quebec, nor in healthy controls. These estimates are necessary to measure their contribution to the hereditary burden of breast cancer in Quebec and to help develop genetic screening policies which are appropriate for the province. We studied 564 French‐Canadian women with early‐onset invasive breast cancer who were treated at a single Montreal hospital. Patients had been diagnosed at age 50 or less, and were ascertained between 2004 and 2008. We screened all 564 patients for nine founder mutations: four in BRCA1, three in BRCA2 and one each in PALB2 and CHEK2. We also studied 6433 DNA samples from newborn infants from the Quebec City area to estimate the frequency of the nine variant alleles in the French‐Canadian population. We identified a mutation in 36 of the 564 breast cancer cases (6.4%) and in 35 of 6443 controls (0.5%). In the breast cancer patients, the majority of mutations were in BRCA2 (54%). However, in the general population (newborn infants), the majority of mutations were in CHEK2 (54%). The odds ratio for breast cancer to age 50, given a BRCA1 mutation, was 10.1 (95% CI: 3.7–28) and given a BRCA2 mutation was 29.5 (95% CI: 12.9–67). The odds ratio for breast cancer to age 50, given a CHEK2 mutation, was 3.6 (95% CI: 1.4–9.1). One‐half of the women with a mutation had a first‐ or second‐degree relative diagnosed with breast or ovarian cancer. Thus, it can be concluded that a predisposing mutation in BRCA1, BRCA2, CHEK2 or PALB2 is present in approximately 6% of French‐Canadian women with early‐onset breast cancer. It is reasonable to offer screening for founder mutations to all French‐Canadian women with breast cancer before age 50. The frequency of these mutations in the general population (0.5%) is too low to advocate population‐based screening.     

Chromosomal radiosensitivity of breast cancer with a CHEK2 mutation

Recently, multiple studies have shown that a sequence variant in CHEK2 (CHEK2 1100delC) plays a role in the susceptibility to breast cancer. This mutation should confer about a twofold increased breast cancer risk in women and a 10-fold increased risk in men. Because the CHEK2 gene plays a critical role in DNA damage repair and the CHEK2 1100delC variant confers susceptibility to breast cancer, we investigated if patients carrying the CHEK2 1100delC mutation are characterized by an enhanced chromosomal radiosensitivity. To this end, familial breast cancer patients, sporadic breast cancer patients, and healthy women, considered in our previously studied to determine their chromosomal radiosensitivity with the G2 and G0-MN assay, were all tested in present study for the presence of the CHEK2 1100delC variant. The 1100delC variant was detected in none of the 100 healthy individuals, in 1 of 100 (1%) unselected breast cancer patients and in 3 of 78 (3.8%) breast cancer patients with a family history of breast cancer. The breast cancer patients with the CHEK2 1100delC genotype had a mean radiation-induced yield of chromatid breaks that was not significantly different from that of the healthy control group. Although the mean yield of micronuclei (MN) was significantly higher compared to the healthy control group, this higher mean MN yield was due to a single patient who had a very high number of MN compared to the parallel control. Our data suggest that breast cancer patients with a CHEK2 1100delC mutation are in general not characterized by a distinct enhanced chromosomal radiosensitivity. These conclusions are, however, very preliminary, because of the small numbers of CHEK2 1100delC breast cancer patients studied.     

Homozygosity for a CHEK2*1100delC mutation identified in familial colorectal cancer does not lead to a severe clinical phenotype

It has recently been suggested that the frequency of the germline CHEK2*1100delC mutation is higher among breast cancer families with colorectal cancer, although the mutation does not seem to be significantly associated with familial colorectal cancer. Five hundred and sixty-four familial colorectal tumours were studied for expression of CHEK2 using tissue microarrays and an antibody against the NH2-terminal SQ regulatory domain of the CHEK2 protein. Normal colonic tissue from patients whose tumours showed loss of CHEK2 expression was investigated further using fragment and sequence analysis for the presence of a CHEK2*1100delC mutation and five other (R117G, R137Q, R145W, I157T, and R180H) known germline variants in CHEK2. Twenty-nine tumours demonstrated loss of expression for CHEK2. Analysis of matched normal colonic tissue from these patients revealed germline CHEK2*1100delC mutation in three cases. In two of these, the mutation was heterozygous but, interestingly, the third patient proved to be homozygous for the deletion, using six different primer pair combinations. None of the other tested germline variants were identified. No CHEK2*1100delC mutations were found in patients whose tumours stained positive. Homozygosity for the CHEK2*1100delC mutation appears not to be lethal in humans. No severe clinical phenotype was apparent, although the patient died from colonic carcinoma at age 52 years. This observation is in line with recent knockout mouse models, although in the latter, cellular defects in apoptosis and increased resistance to irradiation seem to exist. It is also concluded that CHEK2 protein abrogation is not caused by the CHEK2 germline variants R117G, R137Q, R145W, I157T, and R180H in familial colorectal cancer.     

Absence of CHEK2*1100delC mutation in families with hereditary breast cancer in North America

The CHEK2*1100delC mutation has been reported to confer a twofold increased risk of breast cancer among carriers. The frequency of the mutation varies among populations. The highest frequency has been described in Northern and Eastern European countries; the frequency may be much lower in North America. In this study, our aim was to determine the frequency of CHEK2*1100delC in members of breast cancer families who tested negative for a deleterious mutation in BRCA1/2 at the University of Michigan Comprehensive Cancer Center. We genotyped 102 members from 90 families for CHEK2*1100delC. Most of these families had several cases of breast cancer or ovarian cancer (or both), as well as multiple members with other cancer types in a single lineage. No CHEK2*1100delC mutations were detected in any of the 102 individuals, including 51 women diagnosed with breast cancer at an early age (<45 years), 8 women with bilateral breast cancer, 3 men with breast cancer, and 8 women with ovarian cancer. Our data are consistent with the reported very low frequency of CHEK2*1100delC mutations in North American populations (compared with Northern Europe), rendering CHEK2*1100delC such an unlikely culprit in BRCA1/2 negative families that routine testing of these families appears unwarranted.     

A recurrent CHEK2 p.H371Y mutation is associated with breast cancer risk in Chinese women

The association between the CHEK2 and breast cancer risk in Chinese women is unknown. Here, we screened the full CHEK2 coding sequence in 118 Chinese familial breast cancer cases who are negative for mutations in BRCA1 and BRCA2, one recurrent mutation, CHEK2 c.1111C>T (p.H371Y), was identified in five index cases in this cohort. Functional analysis suggested that CHEK2 p.H371Y was a pathogenic mutation that resulted in decreased kinase activity. We further screened the CHEK2 p.H371Y mutation in 909 unselected breast cancer cases and 1,228 healthy individuals. The frequencies of the CHEK2 p.H371Y in familial and unselected breast cancer cases and controls were 4.24% (5/118), 1.76% (16/909), and 0.73% (9/1228), respectively. The p.H371Y mutation was significantly associated with increased breast cancer risk in unselected breast cancer (odds ratio [OR] 2.43, 95% confidence interval [CI] 1.07–5.52, P = 0.034). Our results indicate that the recurrent mutation, p.H371Y, confers a moderate risk of breast cancer in Chinese women. Hum Mutat 32:1–4, 2011. © 2011 Wiley‐Liss, Inc.     

Mutations predisposing to breast cancer in 12 candidate genes in breast cancer patients from Poland

A number of genes other than BRCA1 and BRCA2 have been associated with breast cancer predisposition, and extended genetic testing panels have been proposed. It is of interest to establish the full spectrum of deleterious mutations in women with familial breast cancer.We performed whole‐exome sequencing of 144 women with familial breast cancer and negative for 11 Polish founder mutations in BRCA1, CHEK2 and NBS1, and we evaluated the sequences of 12 known breast cancer susceptibility genes. A truncating mutation in a breast cancer gene was detected in 24 of 144 women (17%) with familial breast cancer. A BRCA2 mutation was detected in 12 cases, a (non‐founder) BRCA1 mutation was detected in 5 cases, a PALB2 mutation was detected in 4 cases and an ATM mutation was detected in 2 cases. Polish women with familial breast cancer who are negative for founder mutations in BRCA1, CHEK2 and NBS1 should be fully screened for mutations in BRCA1, BRCA2 and PALB2. The PALB2 founder mutation c.509_519delGA should be included in the panel of Polish founder mutations.     

Inherited association of breast and colorectal cancer: limited role of CHEK2 compared with high-penetrance genes

We assessed the association between breast cancer (BC) and colorectal cancer (CRC) from referral pattern to the Regional Genetics Service including molecular analysis. Hospital computer records and/or department referral books were used to identify cases referred to the Regional Genetic Service during a 16-year period (1990-2005 inclusive). All files were reviewed along with associated demographic data, risk assessments, referral details and results from mutation testing. Families were assessed for hereditary breast and colorectal cancer (HBCC) criteria, and all families with eligible individuals were tested for the 1100delC mutation in CHEK2. A total of 8,612 families were identified. One hundred and sixteen of 1,631 (7.5%) families with a primary referral for CRC fulfilled the criteria for HBCC, whereas only 68/6981 (1%) BC referrals fulfilled these criteria. Blood samples were obtained from 113 individuals from 83/184 families. Only 1/113 (1%) has screened positive for the CHEK2 mutation, whereas 14 (17%) families segregate BRCA1/2 mutations and at least 7 (8.5%) carry MLH1/MSH2 mutations. HBCC syndrome, if it exists as a separate entity, is not likely to be due to CHEK2 mutations. Many families are explicable by existing high-penetrance genes, and further work is necessary to elucidate whether the remainder is due to chance or as yet undiscovered genes.     

Tumour characteristics and prognosis of breast cancer patients carrying the germline CHEK2*1100delC variant

Background: The germline CHEK2*1100delC variant has been associated with breast cancer in multiple case families where involvement of BRCA1 and BRCA2 has been excluded.

Methods: We have investigated the tumour characteristics and prognosis of carriers of this germline variant by means of a prospective cohort study in an unselected cohort of 1084 consecutive patients with primary breast cancer. Data were collected for 34 patients with a germline CHEK2*1100delC mutation and for 102 patients without this mutation, stratified by age and date of diagnosis of the first primary breast cancer (within 1 year).

Results: Carriers developed steroid receptor positive tumours (oestrogen receptor (ER): 91%; progesterone receptor (PR): 81%) more frequently than non-carriers (ER: 69%; PR: 53%; p = 0.04). Mutation carriers more frequently had a female first or second degree relative with breast cancer (p = 0.03), or had any first or second degree relative with breast or ovarian cancer (p = 0.04). Patients with the CHEK2 variant had a more unfavourable prognosis regarding the occurrence of contralateral breast cancer (relative risk (RR) = 5.74; 95% confidence interval (CI) 1.67 to 19.65), distant metastasis-free survival (RR = 2.81; 95% CI 1.20 to 6.58), and disease-free survival (RR = 3.86; 95% CI 1.91 to 7.78). As yet, no difference with respect to overall survival has been found at a median follow up of 3.8 years.

Conclusion: We conclude that carrying the CHEK2*1100delC mutation is an adverse prognostic indicator for breast cancer. If independently confirmed by others, intensive surveillance, and possibly preventive measures, should be considered for newly diagnosed breast cancer cases carrying the CHEK2*1100delC variant.