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。     

A role for BRCA1 in sporadic breast cancer

To test the hypothesis that altered expression of BRCA1 protein may play an important role in sporadic breast cancer development, 50 randomly selected primary breast cancers (frozen sections, 5 years' median follow-up) were immunolabelled with two monoclonal BRCA1 antibodies (MS110 and MS13). MS110 labelling was exclusively nuclear showing no relation to outcome or tumour pathology. Western blotting demonstrated crossreactivity, suggesting antibody nonspecificity. MS13 labelling was predominantly cytoplasmic. Intense labelling predicted decreased overall survival (P=0.012), disease-free survival (P=0.029), oestrogen receptor negativity (P=0.0004) and c-erbB-2 overexpression (P=0.006). Western blotting detected a 110 kDa molecule consistent with BRCA1 delta11b splice variant. BRCA1 protein is postulated to function as a tumour suppressor. We demonstrate cytoplasmic localisation in sporadic breast cancer suggesting excess delta11b splice variant production, reduced production of full-length BRCA1 and thus postulate reduced tumour suppressor activity. BRCA1 protein appears to have a significant role in both sporadic and hereditary breast cancers.     

Epigenetic silencing and deletion of the BRCA1 gene in sporadic breast cancer

Introduction  

BRCA1 or BRCA2 germline mutations increase the risk of developing breast cancer. Tumour cells from germline mutation carriers have frequently lost the wild-type allele. This is predicted to result in genomic instability where cell survival depends upon dysfunctional checkpoint mechanisms. Tumorigenic potential could then be acquired through further genomic alterations. Surprisingly, somatic BRCA mutations are not found in sporadic breast tumours. BRCA1 methylation has been shown to occur in sporadic breast tumours and to be associated with reduced gene expression. We examined the frequency of BRCA1 methylation in 143 primary sporadic breast tumours along with BRCA1 copy number alterations and tumour phenotype.     

Chromosome 5 imbalance mapping in breast tumors from BRCA1 and BRCA2 mutation carriers and sporadic breast tumors

Comparative genomic hybridization (CGH) analysis has shown that chromosome 5q deletions are the most frequent aberration in breast tumors from BRCA1 mutation carriers. To map the location of putative 5q tumor suppressor gene(s), 26 microsatellite markers covering chromosome 5 were used in loss of heterozygosity (LOH) analysis of breast tumors from BRCA1 (n = 42) and BRCA2 mutation carriers (n = 67), as well as in sporadic cases (n = 65). High-density array CGH was also used to map chromosome 5 imbalance in 10 BRCA1 tumors. A high LOH frequency was found in BRCA1 tumors (range 19-82%), as compared to BRCA2 and sporadic tumors (ranges 11-44% and 7-43%, respectively). In all, 11 distinct chromosome 5 regions with LOH were observed, the most frequent being 5q35.3 (82%), 5q14.2 (71%) and 5q33.1 (69%) in BRCA1 tumors; 5q35.3 (44%), 5q31.3 (43%) and 5q13.3 (43%) in BRCA2 tumors and 5q31.3 (43%) in sporadic tumors. Array CGH analysis confirmed the very high frequency of 5q deletions, including candidate tumor suppressor genes such as XRCC4, RAD50, RASA1, APC and PPP2R2B. In addition, 2 distinct homozygous deletions were identified, spanning regions of 0.7-1.5 Mbp on 5q12.1 and 5q12.3-q13.1, respectively. These regions include only a few genes, most notably BRCC3/DEPDC1B (pleckstrin/G protein interacting and RhoGAP domains) and PIK3R1 (PI3 kinase P85 regulatory subunit). Significant association (p < or = 0.05) was found between LOH at certain 5q regions and factors of poor prognosis, including negative estrogen and progesterone receptor status, high grade, large tumor size and high portion of cells in S-phase. In conclusion, our results confirm a very high prevalence of chromosome 5q alterations in BRCA1 tumors, pinpointing new regions and genes that should be further investigated.     

BRCA1 dysfunction in sporadic basal-like breast cancer

Basal-like breast cancers form a distinct subtype of breast cancer characterized by the expression of markers expressed in normal basal/myoepithelial cells. Breast cancers arising in carriers of germline BRCA1 mutations are predominately of basal-like type, suggesting that BRCA1 dysfunction may play a role in the pathogenesis of sporadic basal-like cancers. We analysed 37 sporadic breast cancers expressing the basal marker cytokeratin 5/6, and age- and grade-matched controls, for downregulation of BRCA1. Although BRCA1 promoter methylation was no more common in basal-like cancers (basal 14% vs controls 11%, P=0.72), BRCA1 messenger RNA expression was twofold lower in basal-like breast cancers compared to matched controls (P=0.008). ID4, a negative regulator of BRCA1, was expressed at 9.1-fold higher levels in basal-like breast cancer (P<0.0001), suggesting a potential mechanism of BRCA1 downregulation. BRCA1 downregulation correlated with the presence of multiple basal markers, revealing heterogeneity in the basal-like phenotype. Finally, we found that 63% of metaplastic breast cancers, a rare type of basal-like cancers, had BRCA1 methylation, in comparison to 12% of controls (P<0.0001). The high prevalence of BRCA1 dysfunction identified in this study could be exploited in the development of novel approaches to targeted treatment of basal-like breast cancer.     

Somatic mutations in the BRCA1 gene in Chinese women with sporadic breast cancer

Recent studies suggested that breast cancer patients who carry a BRCA1 germline mutation benefit from poly (ADP-ribose) polymerase (PARP) inhibitors; therefore, it would be of great interest to detect BRCA1 somatic mutations in sporadic breast cancers. In this study, we detected BRCA1 somatic mutations in tumor cDNA from 144 Chinese women with sporadic breast cancer by using polymerase chain reaction (PCR)-direct sequencing assay. In total, eight BRCA1 alterations (three nonsense mutations and five missense mutations) were identified in this cohort of 144 sporadic breast cancers. We further confirmed that 5 out of 144(3.5%) sporadic breast cancer cases carried a BRCA1 somatic mutation, including two novel nonsense mutations (c.191_212del22 and c.2963C>G) resulting in a truncated protein and three missense mutations (c.114G>T, c.925A>C, and c.824G>A). The two cases with BRCA1 somatic truncating mutations also contained a TP53 somatic mutation in the tumors. Our study suggested that a small subset of sporadic breast cancers do harbor BRCA1 somatic mutations; these patients who carry a BRCA1 somatic mutation may be potential candidates for treatment with PARP inhibitors.     

First description of a sporadic breast cancer in a woman with BRCA1 germline mutation

We describe the case of a woman carrying a germline pathogenic BRCA1 mutation diagnosed with a breast cancer overexpressing HER2. Clinical presentation of the tumor, HER2-positivity, genomic profile and loss of the mutated BRCA1 allele in tumor evidence that BRCA1 is not inactivated in this breast cancer. It represents the first biological demonstration for the existence of a sporadic HER2-positive breast cancer independent from BRCA loss of function in a woman carrier of a deleterious BRCA1 mutation. In a context where targeted therapies based on BRCA loss of function in the tumor are developed, such case could have direct implications.     

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。     

Somatic mutations in the BRCA1 gene in Chinese sporadic breast and ovarian cancer.

Inherited mutations in the BRCA1 gene confer increased susceptibility to breast and ovarian cancer. Its role in sporadic carcinogenesis is not well defined. Somatic mutations in breast cancers have not been reported and to date there are only three reports of somatic mutations in sporadic ovarian cancers. To investigate the contribution of BRCA1 mutations to sporadic breast and ovarian cancer in the Chinese population, we analysed 62 samples from Chinese women using the protein truncation test. There were 40 cases of breast cancer under age 50 and 22 cases of ovarian cancer, all unselected for family history. There was no age selection for the ovarian cancers. We found two somatic BRCA1 mutations in exon 11, one in a breast cancer and the other in an ovarian cancer, both of which result in truncated proteins. Our results indicate that somatic BRCA1 mutations, like somatic mutations in the BRCA2 gene, though very rare, can be found in both breast and ovarian cancers and support a tumor suppressor function for BRCA1 in sporadic tumors.     

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.     

Are estrogen receptor-positive breast cancers in BRCA1 mutation carriers sporadic?

There is a strong association between BRCA1 mutation carrier status and estrogen receptor-negative breast cancer. This has led to the idea that estrogen receptor-positive breast cancers in BRCA1 mutation carriers may be incidental or sporadic in nature and not as a direct result of BRCA1 dysfunction. A recent paper in Breast Cancer Research challenges this view.     

BRCA1/2 mutation status influences somatic genetic progression in inherited and sporadic epithelial ovarian cancer cases

Metaphase comparative genomic hybridization was used to analyze the spectrum of genetic alterations in 141 epithelial ovarian cancers from BRCA1 and BRCA2 mutation carriers, individuals with familial non-BRCA1/2 epithelial ovarian cancer, and women with nonfamilial epithelial ovarian cancer. Multiple genetic alterations were identified in almost all tumors. The high frequency with which some alterations were identified suggests the location of genes that are commonly altered during ovarian tumor development. In multiple chromosome regions, there were significant differences in alteration frequency between the four tumor types suggesting that BRCA1/2 mutation status and a family history of ovarian cancer influences the somatic genetic pathway of ovarian cancer progression. These findings were supported by hierarchical cluster analysis, which identified genetic events that tend to occur together during tumorigenesis and several alterations that were specific to tumors of a particular type. In addition, some genetic alterations were strongly associated with differences in tumor differentiation and disease stage. Taken together, these data provide molecular genetic evidence to support previous findings from histopathological studies, which suggest that clinical features of ovarian and breast tumors differ with respect to BRCA1/2 mutation status and/or cancer family history.     

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.     

A haplotype-based case-control study of BRCA1 and sporadic breast cancer risk

Rare, highly penetrant germ line mutations in BRCA1 strongly predispose women to a familial form of breast and ovarian cancer. Whether common variants (either coding or noncoding) at this locus contribute to the more common form of the disease is not yet known. We tested common variation across the BRCA1 locus in African American, Native Hawaiian, Japanese, Latino, and White women in the Multiethnic Cohort Study. Specifically, 28 single nucleotide polymorphisms (SNPs) spanning the BRCA1 gene were used to define patterns of common variation in these populations. The majority of SNPs were in strong linkage disequilibrium with one another, indicating that our survey captured most of the common inherited variation across this gene. Nine tagging SNPs, including five missense SNPs, were selected to predict the common BRCA1 variants and haplotypes among the non-African American groups (five additional SNPs were required for African Americans) and genotyped in a breast cancer case-control study nested in the Multiethnic Cohort Study (cases, n = 1,715; controls, n = 2,502). We found no evidence for significant associations between common variation in BRCA1 and risk of breast cancer. Given the large size of our study population and detailed analysis of the locus, this result indicates either that common variants in BRCA1 do not substantially influence sporadic breast cancer risk, or that unmeasured heterogeneity in the breast cancer phenotype or unmeasured interactions with genetic or environmental exposures obscure our ability to detect any influence that may be present.     

Contralateral breast cancer in BRCA1 and BRCA2 mutation carriers.

PURPOSE: To estimate the risk of contralateral breast cancer in BRCA1 and BRCA2 carriers after diagnosis and to determine which factors are predictive of the risk of a second primary breast cancer. PATIENTS AND METHODS: Patients included 491 women with stage I or stage II breast cancer, for whom a BRCA1 or BRCA2 mutation had been identified in the family. Patients were followed from the initial diagnosis of cancer until contralateral mastectomy, contralateral breast cancer, death, or last follow-up. RESULTS: The actuarial risk of contralateral breast cancer was 29.5% at 10 years. Factors that were predictive of a reduced risk were the presence of a BRCA2 mutation (v BRCA1 mutation; hazard ratio [HR], 0.73; 95% CI, 0.47 to 1.15); age 50 years or older at first diagnosis (v 相似文献   

散发性乳腺癌BRCA1和BRCA2基因突变分析

目的探讨散发性乳腺癌患者BRCA1及BRCA2基因突变与健康人的差异。方法应用聚合酶链反应-单链构象多态性（PCR-SSCP）分析方法,对83例散发性乳腺癌患者（乳腺癌组）与86例健康人（健康对照组）的血液标本,针对BRCA1和BRCA2基因,选择4个突变发生率较高的外显子[BRCA1中的第5、11（11A、11B）、18外显子,BRCA2中的第11外显子]共5对引物进行突变检测,并应用限制性片段长度多态性（RFLP）方法对具有单核苷酸多态的碱基位点作单核苷酸多态性定性分析。成组设计的定性资料比较采用χ^2检验。结果部分散发性乳腺癌患者和健康人BRCA1基因第5外显子的cDNA 273和287（C→G和A→T）,第11外显子的2430、2532、2630、2685、3191、3232和3667、3876（T→C、T→C、T→G、T→C→G、A→G、A→G和C→A）以及第18外显子的5206和5214（T→A和C→T）碱基位点处存在单个碱基的变化,散发性乳腺癌患者的BRCA1基因突变率高于健康人（14．5％比2．3％,P〈0．05）;应用RFLP方法证实cDNA 2430、2630（T→C、T→G）碱基位点的变化为单核苷酸多态（SNP）;散发性乳腺癌患者与健康人2430（T→C）碱基位点等位基因频数分布不相同,但差异无统计学意义（P〉0．05）。结论散发性乳腺癌患者BRCA1基因突变较常见,而BRCA2的突变十分罕见。     

乳腺癌易感基因BRCA1和BRCA2的突变检测及其临床意义

乳腺癌易感基因BRCA1、BRCA2在家族性和遗传性乳腺癌中突变率较高.现就其功能、检测及临床应用方面的研究进展作一综述.     

Predictors of contralateral breast cancer in BRCA1 and BRCA2 mutation carriers

Purpose:

The objective of this study was to estimate the risk of contralateral breast cancer in BRCA1 and BRCA2 carriers; and measure the extent to which host, family history, and cancer treatment-related factors modify the risk.

Patients and methods:

Patients were 810 women, with stage I or II breast cancer, for whom a BRCA1 or BRCA2 mutation had been identified in the family. Patients were followed from the initial diagnosis of cancer until contralateral mastectomy, contralateral breast cancer, death, or last follow-up.

Results:

Overall, 149 subjects (18.4%) developed a contralateral breast cancer. The 15-year actuarial risk of contralateral breast cancer was 36.1% for women with a BRCA1 mutation and was 28.5% for women with a BRCA2 mutation. Women younger than 50 years of age at the time of breast cancer diagnosis were significantly more likely to develop a contralateral breast cancer at 15 years, compared with those older than 50 years (37.6 vs 16.8% P=0.003). Women aged <50 years with two or more first-degree relatives with early-onset breast cancer were at high risk of contralateral breast cancer, compared with women with fewer, or no first-degree relatives with breast cancer (50 vs 36% P=0.005). The risk of contralateral breast cancer was reduced with oophorectomy (RR 0.47; 95% CI 0.30–0.76; P=0.002).

Conclusion:

The risk of contralateral breast cancer risk in BRCA mutation carriers declines with the age of diagnosis and increases with the number of first-degree relatives affected with breast cancer. Oophorectomy reduces the risk of contralateral breast cancer in young women with a BRCA mutation.