DNA methylation profiling to assess pathogenicity of BRCA1 unclassified variants in breast cancer

Germline pathogenic mutations in BRCA1 increase risk of developing breast cancer. Screening for mutations in BRCA1 frequently identifies sequence variants of unknown pathogenicity and recent work has aimed to develop methods for determining pathogenicity. We previously observed that tumor DNA methylation can differentiate BRCA1-mutated from BRCA1-wild type tumors. We hypothesized that we could predict pathogenicity of variants based on DNA methylation profiles of tumors that had arisen in carriers of unclassified variants. We selected 150 FFPE breast tumor DNA samples [47 BRCA1 pathogenic mutation carriers, 65 BRCAx (BRCA1-wild type), 38 BRCA1 test variants] and analyzed a subset (n=54) using the Illumina 450K methylation platform, using the remaining samples for bisulphite pyrosequencing validation. Three validated markers (BACH2, C8orf31, and LOC654342) were combined with sequence bioinformatics in a model to predict pathogenicity of 27 variants (independent test set).  Predictions were compared with standard multifactorial likelihood analysis. Prediction was consistent for c.5194-12G>A (IVS 19-12 G>A) (P>0.99); 13 variants were considered not pathogenic or likely not pathogenic using both approaches. We conclude that tumor DNA methylation data alone has potential to be used in prediction of BRCA1 variant pathogenicity but is not independent of estrogen receptor status and grade, which are used in current multifactorial models to predict pathogenicity.     

Purification and characterisation of a soluble N-terminal fragment of the breast cancer susceptibility protein BRCA1

The BRCA1 gene encodes a large multidomain protein of 1863 residues, mutations in which lead to breast cancer. Studies to elucidate the mechanisms by which BRCA1 prevents tumour formation have been restricted by the size of the protein. Unable to purify large amounts of the full-length protein, we have identified a fragment of BRCA1, amino acid residues 230-534, that when cloned into the expression vector pET 22b and expressed in Escherichia coli is found predominantly in the soluble portion of the cell lysate. The resulting protein was purified to homogeneity and studies reveal that BRCA1 230-534 binds specifically to four-way junction DNA when compared to duplex and single-stranded DNA.     

BRCA1 epigenetic inactivation predicts sensitivity to platinum-based chemotherapy in breast and ovarian cancer

Germline mutations in the BRCA1 or BRCA2 genes are associated with an increased risk of breast and ovarian cancer development. Both genes are involved in DNA repair, and tumors harboring genetic defects in them are thought to be more sensitive to DNA-damaging agents used in chemotherapy. However, as only a minority of breast and ovarian cancer patients carry BRCA1 or BRCA2 mutations, few patients are likely to benefit from these pharmacogenetic biomarkers. Herein, we show that, in cancer cell lines and xenografted tumors, BRCA1 CpG island promoter hypermethylation-associated silencing also predicts enhanced sensitivity to platinum-derived drugs to the same extent as BRCA1 mutations. Most importantly, BRCA1 hypermethylation proves to be a predictor of longer time to relapse and improved overall survival in ovarian cancer patients undergoing chemotherapy with cisplatin.     

BRCA1 epigenetic inactivation predicts sensitivity to platinum-based chemotherapy in breast and ovarian cancer

Germline mutations in the BRCA1 or BRCA2 genes are associated with an increased risk of breast and ovarian cancer development. Both genes are involved in DNA repair, and tumors harboring genetic defects in them are thought to be more sensitive to DNA-damaging agents used in chemotherapy. However, as only a minority of breast and ovarian cancer patients carry BRCA1 or BRCA2 mutations, few patients are likely to benefit from these pharmacogenetic biomarkers. Herein, we show that, in cancer cell lines and xenografted tumors, BRCA1 CpG island promoter hypermethylation-associated silencing also predicts enhanced sensitivity to platinum-derived drugs to the same extent as BRCA1 mutations. Most importantly, BRCA1 hypermethylation proves to be a predictor of longer time to relapse and improved overall survival in ovarian cancer patients undergoing chemotherapy with cisplatin.     

Role of BRCA1 and BRCA2 gene mutations in epithelial ovarian cancer in Indian population: a pilot study

Ovarian cancer is a silent killer as most patients have non-specific symptoms and usually present in advanced stage of the disease. It occurs due to certain genetic alterations and mutations namely founder mutations, 187delAG and 5385insC in BRCA1 and 6174delT in BRCA2 which are associated with specific family histories. These highly penetrant susceptibility genes responsible for approximately half of families containing 2 or more ovarian cancer cases account for less than 40% of the familial excess malignancy risk. The remaining risk may be due to single nucleotide polymorphisms (SNPs) which are single base change in a DNA sequence with usual alternatives of two possible nucleotides at a given position. Preliminary study involving 30 women with histologically proven epithelial ovarian cancer was conducted and their detailed genetic analysis was carried out. Regions of founder mutations on BRCA1 and BRCA2 were amplified and sequenced using primers designed based on 200 bp upstream and downstream regions of the mutation sites. Five sequence variants in BRCA1 were identified of which three novel sequence variants were found in 23 patients while in BRCA2, one novel sequence variant was found. The three founder mutations 187delAG, 5385insC in BRCA1 and 6174delT in BRCA2 were not seen in any of the subjects.     

RADS1和BRCA1在结直肠癌中的表达及临床意义

目的观察结直肠癌中RAD51和BRCA1基因的表达,探讨二者与结直肠癌发生发展及治疗的关系。方法收集结直肠癌癌灶及癌旁正常组织各42例,采用免疫组织化学法及逆转录一聚合酶链反应（reverse transeription-PCR,RTPCR）检测标本组织中RAD51、BRCA1蛋白和mRNA的表达水平。分析RAD51、BRCA1在结直肠癌中的表达水平与临床病理特征的关系以及二者之间的相互关系。结果在结直肠癌组织中RAD51（33例,78．6％）、BRCA1（30例,71．4％）的表达较癌旁正常组织RAD51（7例,16．7％）、BRCA1（18例,42．9％）高（P〈0．05）;结直肠癌中RAD51mRNA（0．51±0．26）和BRCA1 mRNA（O．70±0．96）的值较两者在正常组织中mRNA（0．10±0．22）高（P〈0．01）;两者蛋白及mRNA的表达水平与性别、年龄、分化程度、TNM分期等均无统计学差异（P〉0．05）;BRCA1与RAD51在结直肠癌中的表达水平成明显正相关（蛋白：r=0．731,P〈0．01mRNA：r=0．572,P〈0．01）。结论BRCA1与RAD51在结直肠癌组织中高表达,且二者的表达水平呈明显正相关;BRCAl与RAD51的表达异常可能与结直肠癌的发生发展有关。     

Triple negative breast cancer: microRNA expression profile and novel discriminators according to BRCA1 status

Triple-negative breast cancer (TNBC) represents 15% of breast carcinomas. More than 80% of women with a breast cancer associated with a breast cancer type 1 (BRCA1) mutation develop a TNBC. microRNAs (miRNAs) play critical roles in diverse biological processes and are aberrantly expressed in several human neoplasms including breast cancer, where they function as actors of tumor onset, behavior, and progression. However, an extensive microRNA profile has not yet been determined for TNBC. Taqman low-density arrays (TLDAs) were used to screen the expression level of 667 miRNAs in TNBC versus normal breast tissues. Our TLDA results revealed 20 differentially expressed miRNAs among which 14 (10 upregulated and four downregulated) were confirmed by an individual quantitative real-time polymerase chain reaction. Interestingly, a novel link between BRCA1 status and miRNA expression level was identified through miR-96 and miR-10b that were very important discriminators between TNBC with mutated BRCA1 and TNBC with wild type BRCA1. This study promises discoveries of new pathological pathways at work in this dreadful disease and clearly warrants validation in large prospective studies with the aim of identifying novel biomarkers for diagnosis and targets for clinical interventions.     

Reproductive factors and breast cancer risk among BRCA1 or BRCA2 mutation carriers: Results from ten studies

Although reproductive factors are among the most well-established risk factors for breast cancer in the general population, it is still a matter for debate whether these factors act as risk modifiers among BRCA1 or BRCA2 mutation carriers. This meta-analysis is the first to be performed to determine the relationship between reproductive factors and breast cancer risk among BRCA1 and BRCA2 mutation carriers. We searched the PubMed database up to February 2013. A total of ten studies met the inclusion criteria. The results showed that the reproductive factors may be associated with breast cancer risk only among BRCA1 mutation carriers. No association was found between parity and breast cancer risk. Compared with women at the youngest age in the first-birth category, women in the oldest age category were at a 38% lower risk of breast cancer (RR = 0.62, 95%CI = 0.45–0.85). Breastfeeding for at least 1 or 2 years was associated with a 37% reduction in breast cancer risk (RR = 0.63, 95%CI = 0.46–0.86). Women at the oldest age in the menarche category were at a 34% lower risk of breast cancer (RR = 0.66, 95%CI = 0.53–0.81) than women in the youngest age category. However, none of the reproductive factors were associated with breast cancer risk among BRCA2 mutation carriers. In conclusion, late age at first birth, breastfeeding, and late age at menarche protect against breast cancer in BRCA1 mutation carriers only. Further studies are needed to explore the mechanisms.     

BRCA1-hapoinsufficiency: Unraveling the molecular and cellular basis for tissue-specific cancer

Over the past 20 years tremendous progress has been made in understanding the function of BRCA1 gene products. Yet one question still remains: why is mutation of BRCA1 typically associated with preferential development of breast and ovarian cancers and not tumors in other tissues? Here we discuss recent evidence documenting the effect of BRCA1-haploinsufficiency in different cells and tissues and synthesize a model for how mutations in a single BRCA1 allele in human cells might preferentially confer increased cancer risk in breast epithelial cells.     

晚期非小细胞肺癌组织中BRCA1、STMN1、RRM1的表达及其临床意义

目的：探讨晚期非小细胞肺癌（NSCLC）组织中DNA修复基因家族成员BRCA1、STMN1、RRM1的表达及其临床意义。方法：回顾性分析本院2009年1月至2012年1月86例经组织学或细胞学证实的IIIB／IV期非小细胞肺癌患者,以分支DNA-液相芯片法检测肿瘤标本的BRCA1、STMN1、RRM1基因mRNA表达,并对检测结果应用SPSS13．0进行统计分析。结果：BRCA1中高表达与患者的性别无明显相关性（x毫0．1003,P=0．7514）,STMN1中高表达与肿瘤的分化程度相关（卡方=18．3002,P=0．000）。分析基因mRNA的表达情况与患者的化疗有效率,提示BRCA1中高表达患者完全缓解0例、部分缓解23例、稳定17例、进展16例,低表达患者分别为0例、12例、14例、4例（P〉0．05）,而STMN1表达阳性患者与阴性患者的临床疗效分别为0例、14例、21例、16例和0例、21例、10例、4例（P〈0．05）;RRM1表达阳性患者与阴性患者的临床疗效分别为0例、17例、19例、20例和0例、18例、12例、0例（P〈0．05）。结论：通过对BRCA1、STMN1、RRM1基因mRNA表达的个体化治疗靶标检测,对患者的预后以及化疗疗效有一定的预测价值。