Association of the BRCA1 promoter polymorphism rs11655505 with the risk of familial breast and/or ovarian cancer

Germline mutations in the BRCA1 tumor suppressor gene predispose affected individuals to breast cancer; however, incomplete cancer penetrance and the presence of phenocopies in BRCA1 families also indicate genetic and environmental modifiers of breast cancer risk. In this study, we have tested the single nucleotide polymorphism rs1655505 of the BRCA1 promoter, as candidate for the modifier of breast cancer risk. The polymorphic variants were genotyped in BRCA1-negative (729), familial breast and/or ovarian cancer cases (FBOC), including cases with a reported maternal history (154), nonfamilal (sporadic) cases (600), hereditary breast/ovarian cases with BRCA1 mutations (190) and population controls (1,590) from Central Poland. An association with the risk of FBOC was observed for the minor (T) allele and (TT) genotype (T: p = 0.006, OR = 1.40, 95 % CI = 1.10–1.79; TT: p = 0.001, OR = 2.23, 95 % CI = 1.37–3.62) in female cases with a reported maternal history, specifically in women with the onset of disease after 50 years of age (T: p = 0.004, OR = 1.77, 95 % CI = 1.20–2.62; TT: p = 0.001, OR = 3.7, 95 % CI = 1.62–8.46). The presented evidence suggests a need to conduct larger studies on the association between genetic variations at the BRCA1 promoter and the breast cancer risk, according to maternal/paternal lineage.     

BRCA1 promoter methylation in sporadic breast tumors: relationship to gene expression profiles

BRCA1 is a tumor suppressor gene that functions in DNA repair. Basal-like tumors are a distinctive subtype of breast cancer defined by gene expression profiles. Hereditary BRCA1 breast tumors and basal-like sporadic tumors have a similar phenotype and gene expression signature, suggesting involvement of BRCA1 in the pathogenesis of sporadic basal-like cancer. This study evaluates the role of BRCA1 in sporadic breast tumorigenesis. BRCA1 protein expression and promoter methylation are compared to tumor histopathology and gene expression profiles. We find BRCA1 protein expression correlates with tumor mitotic rate, consistent with normal cell-cycle regulation of the BRCA1 gene. Methylation is found in 21% of tumors and is associated with lower BRCA1 protein, but not with specific pathologic features. Basal-like tumors, defined by hierarchical clustering of gene expression, have infrequent BRCA1 methylation and high levels of BRCA1 protein expression consistent with their high mitotic rate. Tumors with BRCA1 promoter methylation are present in all expression clusters; however, a subgroup of ER-positive high-grade tumors has a significantly greater number of BRCA1 methylated tumors. Absence of BRCA1 promoter methylation and high levels of BRCA1 expression in basal-like sporadic tumors suggest alternate explanations for the phenotypic similarities of these tumors to hereditary BRCA1 tumors.     

散发性乳腺癌组织中BRCA1基因启动子甲基化与蛋白表达的相关性

目的：探讨BRCA1基因启动子甲基化对BRCA1蛋白表达的影响,及与散发性乳腺癌发病之间的关系。方法：甲基化特异性PCR（MSP）法检测51例散发性乳腺浸润导管癌和10例乳腺良性组织的BRCA1基因启动子甲基化状态,SP法检测BRCA1蛋白表达水平。结果：10例乳腺良性组织中均未检测到BRCA1启动子的异常甲基化,BRCA1蛋白在细胞核均阳性表达,其中70％（7／10）为强阳性表达。在51例散发性乳腺浸润性导管癌组织中检测到7例（13．73％）BRCAl启动子发生异常甲基化,其余44例（86．27％）未检测到BRCA1启动子甲基化。7例BRCA1启动子甲基化的组织均未见BRCA1蛋白细胞核阳性表达（0／7）,仅有1例BRCA1蛋白细胞质表达;44例未检测到BRCA1启动子甲基化的浸润性导管癌中,30例（68．18％）BRCA1蛋白在细胞核阳性表达,14例（31．82％）BRCA1蛋白在细胞核阴性表达。BRCA1启动子甲基化与BRCA1蛋白核低表达密切相关,X^2=11．9591,P=0．0005;BRCA1蛋白的表达在乳腺良性组织与癌组织之间差异有统计学意义,X^2=4．5879,P=0．032。结论：乳腺癌易感基因BRCA1启动子甲基化可抑制BRCA1蛋白表达,并影响其参与散发性乳腺癌的发生发展过程。     

散发性乳腺癌中 DNMT3a、3b 表达及其与 BRCA1基因启动子甲基化和蛋白表达的相关性

目的:探讨DNMT3a、3b蛋白表达与散发性乳腺癌BRCA1基因启动子甲基化状态及蛋白表达的相关性。方法:收集乳腺肿瘤组织及相关临床资料。采用免疫组化法检测200例散发性乳腺癌与25例乳腺纤维腺瘤组织中DNMT3a、3b蛋白的表达情况。甲基化特异性PCR检测108例散发性乳腺癌中BRCA1基因启动子甲基化状态。结果:与乳腺纤维腺瘤相比,乳腺癌组织中DNMT3a表达水平显著增高(P=0.037),DNMT3b表达水平增加不显著(P=0.478)。乳腺癌中BRCA1基因启动子存在甲基化。DNMT3a、3b过表达与乳腺癌病程晚期(TNMⅢ-Ⅳ期)显著相关(P=0.064,P=0.007);DNMT3a与BRCA1基因甲基化正相关(r=0.222,P=0.021),与BRCA1蛋白负相关(r=-0.172,P=0.022)。BRCA1蛋白表达与乳腺癌患者OS和DFS显著相关(P=0.025,P=0.027),DNMT3a表达与散发性乳腺癌OS和DFS存在一定的相关性(P=0.052,P=0.091)。结论:DNMT3a、3b高表达与乳腺癌侵袭转移、病程进展、预后相关。DNMT3a可能参与催化BRCA1基因启动子甲基化导致BRCA1蛋白表达下调的过程。抑制DNMT3a、3b蛋白可能有利于散发性乳腺癌的预防和治疗。     

BRCA1 expression status in relation to DNA methylation of the BRCA1 promoter region in sporadic breast cancers.

To understand the biological role of BRCA1 in sporadic breast cancers, the relationship between DNA methylation of the BRCA1 promoter region and BRCA1 expression was studied using molecular biological and immunohistochemical methods. Furthermore, BRCA1 expression was compared with the expression of various cell cycle regulatory proteins and the morphological nuclear grade of cancer cells. Of 32 sporadic breast cancers investigated in this study, 10 (31%) revealed DNA methylation of the BRCA1 promoter region. The expression of BRCA1 was observed in the nuclei of cancer cells and 18 (56%) of 32 cancers were positive for BRCA1 immunoreactivity. Breast cancers with BRCA1 methylation lacked BRCA1 expression, except for only three cancers, and there was a significant inverse relationship between BRCA1 methylation and its expression in sporadic breast cancers (P = 0.043). Compared with the expression of various cell cycle regulatory proteins, breast cancers with BRCA1 methylation showed decreased expression of estrogen receptor (P = 0. 016) and p27 (P = 0.018) and increased expression of p21 (P = 0.011). Furthermore, breast cancers without BRCA1 expression or with BRCA1 methylation had a tendency to contain nuclei with higher grade. These findings indicate that BRCA1 methylation might greatly influence its expression and BRCA1 expression might play an important role in cell cycle regulation and influence the grade of malignancy of sporadic breast cancers.     

BRCA1 promoter methylation in peripheral blood cells is associated with increased risk of breast cancer with BRCA1 promoter methylation

BRCA1 promoter methylation reportedly plays an important part in the pathogenesis of human breast cancer. In the present study, we investigated whether or not BRCA1 promoter methylation in peripheral blood cells (PBCs) can serve as a risk factor for developing breast cancer. The association of BRCA1 promoter methylation in PBCs with breast cancer risk was examined in a case–control study (200 breast cancer patients and 200 controls). BRCA1 promoter methylation in PBCs and breast tumors was determined with a methylation-specific quantitative PCR assay. BRCA1 promoter methylation in PBCs was seen in 43 (21.5%) of the breast cancer patients and in 27 (13.5%) of the controls. The odds ratio for breast cancer adjusted for other epidemiological risk factors was 1.73 (1.01–2.96) and was statistically significant (P = 0.045). When breast tumors were classified into those with and without BRCA1 promoter methylation, the odds ratio was 0.84 (0.43–1.64) (P = 0.61) for BRCA1 promoter methylation-negative and 17.78 (6.71–47.13) (P < 0.001) for BRCA1 promoter methylation-positive breast tumors. BRCA1 promoter methylation in PBCs is significantly associated with risk of breast cancer with BRCA1 promoter methylation. This seems to indicate that BRCA1 promoter methylation in PBCs may constitute a novel risk factor for breast cancer with BRCA1 promoter methylation.     

散发性乳腺癌患者血浆BRCA1基因启动子异常甲基化的检测

目的:探讨散发性乳腺癌组织及外周血浆中BRCA1基因启动子异常甲基化状况及其在散发性乳腺癌诊断中的价值。方法:用甲基化特异PCR方法对散发性乳腺癌患者癌组织、癌旁组织及相应血浆进行BRCA1异常甲基化检测。结果:93例散发性乳腺癌组织中,BRCA1基因启动子异常甲基化率为29%(27/93),相应血浆中BRCA1的甲基化检出率为24.7%(23/93),而癌旁组织、正常对照血浆未检出甲基化,只检出未甲基化的BRCA1。血浆中甲基化改变与肿瘤组织甲基化状况显著相关(P<0.05);BRCA1异常甲基化与髓样癌和粘液腺癌的组织分型显著相关(P<0.05),也与肿瘤淋巴结转移显著相关(P<0.005);但与散发性乳腺癌患者年龄(绝经与否)及肿瘤分级无显著的相关性(P>0.05)。结论:血浆BRCA1基因异常甲基化改变的检测在散发性乳腺癌的特异诊断、组织分型和淋巴结恶性转移等方面有一定的应用价值。     

BRCA1 promoter methylation status does not predict response to tamoxifen in sporadic breast cancer patients

The purpose of this study is to investigate whether BRCA1 promoter methylation is associated with poorer outcome in sporadic breast cancer cases treated with tamoxifen. BRCA1 promoter methylation was determined by bisulfite pyrosequencing in two groups of sporadic breast cancer patients, systemically untreated (N = 497) and treated with adjuvant tamoxifen (N = 497). Associations of BRCA1 promoter methylation with clinopathological characteristics and the effect of BRCA1 promoter methylation on time to first recurrence (TTR) and overall survival (OS) were examined. No significant differences were observed between BRCA1 promoter methylation and clinopathological characteristics in untreated and tamoxifen-treated groups. Cut point analysis did not find any promising cut point for BRCA1 promoter methylation that would differentially influence TTR and OS in untreated and tamoxifen-treated group. Using the median (2.53 %) and an arbitrary value of 10 % as a cut point for methylation, we still found no significant effect of BRCA1 promoter methylation on TTR and OS in untreated and tamoxifen-treated group. Despite data suggesting that BRCA1 levels impact estrogen receptor response to tamoxifen, our results indicate that BRCA1 promoter methylation is not associated with poorer outcome in sporadic breast cancer cases treated with tamoxifen.     

散发性乳腺癌中MTA1表达与ERα甲基化关系的研究

目的:通过甲基化特异性PCR和免疫组化研究女性散发性乳腺癌中ERα基因启动子区甲基化和MTA1蛋白表达的相关性。方法:甲基化PCR研究102例散发性乳腺癌ERα启动子甲基化情况,免疫组化研究其MTA1蛋白表达情况。结果:乳腺癌组织中ERα启动子甲基化率为37.3%,乳腺癌组织中MTA1表达率为29.4%,高于其在癌旁正常乳腺组织中的表达(P<0.05),MTA1表达和ERα启动子甲基化均与乳腺肿瘤大小、TNM分期及淋巴结转移相关(P<0.05),且乳腺癌中ERα启动子甲基化与MTA1阳性表达呈正相关(P<0.05)。结论:女性散发性乳腺癌中ERα基因启动子甲基化与MTA1表达升高密切相关,其在乳腺癌发展过程中可能起重要作用。     

Novel BRCA1 deleterious mutation (c.1918C>T) in familial breast and ovarian cancer syndrome who share a common ancestry

Mutations in breast cancer susceptibility (BRCA) genes lead to defects in DNA repair processes resulting in elevated genome instability and predisposing to breast and ovarian cancer. We report a novel mutation (c.1918C>T) in the exon 11 of the BRCA1 gene that consists of a nonsense mutation that causes a stop codon downstream in the 640 position of the protein. The mutation was present in two Spanish unrelated families and was associated with four breast cancer cases, including two bilateral breast cancer (one of them synchronous). The median age/mean age (range) was 48.5/44.25 years (27–53). This finding led us to perform haplotype analysis in all family carriers. Four highly polymorphic microsatellite markers were used (17-3858, 17-3930, D17S855, D17S1326) to establish whether or not all these families had a common ancestor. This analysis showed that all mutation carriers of these families had a common haplotype. None of the noncarriers of the mutation or of the 24 healthy controls showed this haplotype. Therefore, the c.1918C>T mutation carriers from these two families allows us to assert that all analyzed mutation carriers share a common ancestry.     

Haplotype analysis of common variants in the BRCA1 gene and risk of sporadic breast cancer

IntroductionTruncation mutations in the BRCA1 gene cause a substantial increase in risk of breast cancer. However, these mutations are rare in the general population and account for little of the overall incidence of sporadic breast cancer.MethodWe used whole-gene resequencing data to select haplotype tagging single nucleotide polymorphisms, and examined the association between common haplotypes of BRCA1 and breast cancer in a nested case-control study in the Nurses'' Health Study (1323 cases and 1910 controls).ResultsOne haplotype was associated with a slight increase in risk (odds ratio 1.18, 95% confidence interval 1.02–1.37). A significant interaction (P = 0.05) was seen between this haplotype, positive family history of breast cancer, and breast cancer risk. Although not statistically significant, similar interactions were observed with age at diagnosis and with menopausal status at diagnosis; risk tended to be higher among younger, pre-menopausal women.ConclusionsWe have described a haplotype in the BRCA1 gene that was associated with an approximately 20% increase in risk of sporadic breast cancer in the general population. However, the functional variant(s) responsible for the association are unclear.     

BRCA1基因启动子甲基化在三阴性乳腺癌中的表达及其临床意义

目的:评估三阴性乳腺癌（TNBC）患者中乳腺癌易感基因1（BRCA1）甲基化的表达及与患者预后的关系。方法:收集在我院甲乳科治疗的乳腺癌患者手术切除标本524例,应用联合亚硫酸氢钠限制性内切酶分析法,观察BRCA1启动子甲基化状态。应用定量逆转录聚合酶链反应评估BRCA1 mRNA表达,应用免疫组织化学法评估BRCA1蛋白表达。结果:共有157（30.0%）例TNBC患者,有25（4.77%）例存在BRCA1启动子甲基化,所有BRCA1启动子甲基化的肿瘤均为TNBC。TNBC患者中,BRCA1启动子甲基化患者的BRCA1 mRNA水平显著低于BRCA1启动子未甲基化患者［（0.019±0.005） vs （0.095±0.013）,P<0.001］,免疫组化分析未在BRCA1启动子甲基化患者中检测出BRCA1蛋白表达。BRCA1启动子甲基化患者的总生存率（OS）显著低于非甲基化患者（logrank P=0.038）。BRCA1蛋白低表达患者的OS与RFS均低于高表达组,但差异没有统计学意义（分别logrank P=0.526,P=0.467）。结论:BRCA1启动子甲基化导致了BRCA1表达的下降,并与TNBC患者较差预后相关。BRCA1启动子甲基化是一种促成BRCA1功能丧失的重要机制。     

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 3 0例散发性乳腺癌和 15例正常乳腺组织中BR CA1基因外显子 2、11和 2 0的突变情况。结果 :15例正常乳腺组织在 3个外显子上都未显示电泳异常 ,3 0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。     

BRCA1 promoter methylation is associated with increased mortality among women with breast cancer

Promoter-CpG island hypermethylation has been proposed as an alternative mechanism to inactivate BRCA1 in the breast where somatic mutations of BRCA1 are rare. To better understand breast cancer etiology and progression, we explored the association between BRCA1 promoter methylation status and prognostic factors as well as survival among women with breast cancer. Promoter methylation of BRCA1 was assessed in 851 archived tumor tissues collected from a population-based study of women diagnosed with invasive or in situ breast cancer in 1996–1997, and who were followed for vital status through the end of 2002. About 59% of the tumors were methylated at the promoter of BRCA1. The BRCA1 promoter methylation was more frequent in invasive cancers (P = 0.02) and among premenopausal cases (P = 0.05). BRCA1 promoter methylation was associated with increased risk of breast cancer-specific mortality (age-adjusted HR 1.71; 95% CI: 1.05–2.78) and all-cause mortality (age-adjusted HR 1.49; 95% CI: 1.02–2.18). Neither dietary methyl intakes in the year prior to the baseline interview nor the functional polymorphisms in one-carbon metabolism were associated with BRCA1 methylation status. Our study is the first epidemiological investigation on the prognostic value of BRCA1 promoter methylation in a large population-based cohort of breast cancer patients. Our results indicate that BRCA1 promoter methylation is an important factor to consider in predicting breast cancer survival. This work was supported by grants from the National Institutes of Health (CA109753 to JC; DK55865 to SZ) and in part by grants from Department of Defense (BC031746), National Cancer Institute and the National Institutes of Environmental Health and Sciences (UO1CA/ES66572, UO1CA66572, P30CA013696, P30ES09089 and P30ES10126); and by the University of North Carolina Clinical Nutrition Research Unit (DK56350) and Center for Environmental Health and Susceptibility (ES10126). Xu, X. is a recipient of the Predoctoral Traineeship Award (W81XWH-06-1-0298) of Department of Defense Breast Cancer Research Program.     

Association of PHB 1630 C>T and MTHFR 677 C>T polymorphisms with breast and ovarian cancer risk in BRCA1/2 mutation carriers: results from a multicenter study

Background:

The variable penetrance of breast cancer in BRCA1/2 mutation carriers suggests that other genetic or environmental factors modify breast cancer risk. Two genes of special interest are prohibitin (PHB) and methylene-tetrahydrofolate reductase (MTHFR), both of which are important either directly or indirectly in maintaining genomic integrity.

Methods:

To evaluate the potential role of genetic variants within PHB and MTHFR in breast and ovarian cancer risk, 4102 BRCA1 and 2093 BRCA2 mutation carriers, and 6211 BRCA1 and 2902 BRCA2 carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2 (CIMBA) were genotyped for the PHB 1630 C>T (rs6917) polymorphism and the MTHFR 677 C>T (rs1801133) polymorphism, respectively.

Results:

There was no evidence of association between the PHB 1630 C>T and MTHFR 677 C>T polymorphisms with either disease for BRCA1 or BRCA2 mutation carriers when breast and ovarian cancer associations were evaluated separately. Analysis that evaluated associations for breast and ovarian cancer simultaneously showed some evidence that BRCA1 mutation carriers who had the rare homozygote genotype (TT) of the PHB 1630 C>T polymorphism were at increased risk of both breast and ovarian cancer (HR 1.50, 95%CI 1.10–2.04 and HR 2.16, 95%CI 1.24–3.76, respectively). However, there was no evidence of association under a multiplicative model for the effect of each minor allele.

Conclusion:

The PHB 1630TT genotype may modify breast and ovarian cancer risks in BRCA1 mutation carriers. This association need to be evaluated in larger series of BRCA1 mutation carriers.     

Constitutional methylation of the BRCA1 promoter is specifically associated with BRCA1 mutation-associated pathology in early-onset breast cancer

Women carrying germline mutations in BRCA1 are at a substantially elevated risk of breast cancer and their tumors typically have distinctive morphologic features. We hypothesized that constitutional methylation of the BRCA1 promoter region could give rise to such breast cancers in women. We selected 255 women diagnosed with breast cancer before the age of 40 years for whom BRCA1 germline mutations had not been identified. Of them, 52 had five or more of nine BRCA1 mutation-associated morphologic features (group 1), 39 had four (group 2), and 164 had three or less (group 3). The prevalence of detectable BRCA1 promoter methylation in peripheral blood DNA decreased from 31% to 10% to 5% across groups 1-3, respectively (P = 0.000002), and was significantly greater than the 4% frequency in unaffected controls (P = 0.004). Peripheral blood methylation was associated with a 3.5-fold (95% CI, 1.4-10.5) increased risk of having early onset breast cancer. Methylation was consistently mosaic in the peripheral blood where the estimated allelic frequency of BRCA1 promoter methylation ranged from 0.1% to 17%. Group 1 women, but not group 3 women, with detectable methylation of peripheral blood DNA had high levels of BRCA1 promoter methylation of their tumor DNA, indicating that constitutional BRCA1 methylation strongly predisposes toward the development of BRCA1 methylated tumors that then have features resembling BRCA1 mutated tumors. Screening peripheral blood for BRCA1 promoter methylation might thus predict early-onset breast cancers. This raises the possibility of chemoprevention or other intervention to diminish the risk of developing breast cancer in these women.