Loss of heterozygosity in BRCA1 and BRCA2 markers and high‐grade malignancy in breast cancer

Loss of heterozygosity (LOH) in loci of the 17q21 and 13q1213 regions can collaborate in the inactivation of BRCA1, BRCA2, and possibly other genes implicated in the pathogenesis of breast carcinomas. We investigate allelic losses in microsatellites of the BRCA1 and BRCA2 regions, and their correlations with seven pathologic parameters in 140 breast carcinomas. Those cases showing LOH in the region of the RB gene, 13q14, were excluded from the study. The LOH analysis was performed by amplifying DNA by PCR, using four markers of the 17q21 region (D17S856, D17S855, D17S1323, and D17S1327) and four markers of the 13q1213 region (D13S290, D13S260, D13S310, and D13S267). LOH in the BRCA1 region was found in 47% of tumors, correlating significantly with estrogen receptor content (p = 0.025), progesterone receptors (p = 0.004), higher grade (p = 0.0008), peritumoral vessel invasion (p = 0.001), and lymph node metastases (p = 0.002). When we excluded the cases with LOH in the BRCA2 region and those not informative for it, the significance disappeared. In the BRCA2 region, a rate of LOH of 51% was found; it correlated significantly with estrogen receptor content (p = 0.002), progesterone receptors (p =0.03), peritumoral vessel invasion (p = 0.005), higher grade (p =0.002), and lymph node metastases (p = 0.001). When cases with BRCA1 losses and those not informative were excluded, again the significance disappeared. Concomitant losses in the BRCA1 and BRCA2 regions were found in 32% of cases, correlating significantly with lymph node metastases (p = 0.0002), estrogen receptor content (p = 0.003), progesterone receptors (p = 0.001), histologic grade (p =0.01), and peritumoral vessel invasion (p = 0.0004). These results suggest that concomitant losses in both regions could have a functional effect, influencing the presence of a poor tumor pathophenotype in breast carcinomas.     

Are the hereditary forms of BRCA1 and BRCA2 breast cancer sensitive to estrogens?

There is emerging evidence from clinical and experimental data that familial breast cancers, including BRCA1 and BRCA2 related forms, could be in fact estrogen-sensitive. Interactions between BRCA1 gene expression and estrogens have been reported. On one hand, BRCA1 expression could be induced by estradiol in experimental models. On the other hand, recent studies indicate that BRCA 1 interacts with and regulates the activity of estrogen receptor ERalpha. Endogenous or exogenous estrogens, such as oral contraceptive, may also increase the risk of breast cancer in BRCA1 mutation carriers in clinical studies. Conversely, prophylactic oophorectomy and anti-estrogens may decrease the risk of familial breast cancer. Prospective studies are thus required to estimate the potential benefits of estrogen suppression therapies for prevention or adjuvant treatment of familial breast cancer. Oral contraception and hormonal replacement therapy after menopause should be used with caution in BRCA1 or BRCA2 mutation carriers.     

Incidence of BRCA1 and BRCA2 mutations in 54 Chilean families with breast/ovarian cancer, genotype–phenotype correlations

Summary Our aim was to analyze the incidence of mutations in BRCA1 and BRCA2 genes in 54 families with breast/ovarian cancer. Families were selected from three Institutions following the standard criteria for hereditary breast/ovarian cancer. PCR amplification of all exons was performed, followed by SSCP, heteroduplex, PTT and sequencing analysis. We identified eight truncation mutations, three in the BRCA1 gene and five in the BRCA2 gene. Three of these mutations have not been reported previously by other groups: 308insA in one family, 3936 C>T in two families, for BRCA1, and 4970insTG in one family for BRCA2. In addition two families having Ashkenazi Jewish ancestors present the well known mutations 185delAG and 6174delT. Interestingly, 5 out of 11 families have mutations recurrent in Spanish families. Among the 54 families selected, seven have breast and ovary cancer cases, and only two presented a mutation in BRCA1 or BRCA2 genes. Other cancers as prostate and stomach are frequent among relatives carrying the mutation. Five cases of very early onset (<31 years old) breast cancer were detected. The frequencies of BRCA1 (0.074) and BRCA2 (0.13) mutations in our families is low but similar to the incidence found in other populations, like in Spain. Since is widely known that risk factors that modulate the development of breast cancer such as lifestyle risk factors, geographic location, country of origin and socioeconomic status, besides a familial history of breast cancer our findings suggest that the history of colonization and immigrations is very relevant when studying hereditary factors associated to breast cancer.     

MDM2 SNP309 accelerates breast and ovarian carcinogenesis in BRCA1 and BRCA2 carriers of Jewish–Ashkenazi descent

A functional single nucleotide polymorphism in the promoter of the MDM2 gene, SNP309 (T>G), was recently found to accelerate tumorigenesis in early onset cancer cases. The SNP309 G-allele, introduces an SP1 site in the MDM2 promoter, resulting in enhanced MDM2 expression and activity. Thus, the G-allele of MDM2 SNP309 may represent a cancer predisposing allele. In this report, we assessed the role of SNP309 as a modifier of mutant BRCA1/BRCA2 alleles in inherited breast and ovarian cancer cases among Ashkenazi–Jewish (AJ) women. We genotyped several subsets of AJ women: 138 healthy women, 140 affected BRCA1/2 mutation carriers, 120 asymptomatic BRCA1/2 mutation carriers and 187 sporadic breast cancer patients. The frequency of GG genotype of SNP309 was similar among the different groups. Interestingly, we found almost three times higher frequency of the GG genotype among BRCA1/2 carriers diagnosed with breast and/or ovarian cancer at or under the age of 51 years compared with carriers diagnosed with cancer above the age of 51 years (allele frequency, P = 0.019). The GG genotype was significantly associated with breast and ovarian cancer risk among BRCA1/2 carriers diagnosed before 51 years of age (OR, 3.93; 95% CI, 1.41–10.90, P = 0.009). No significant difference in frequency of the GG genotype was observed between early and late onset non-carrier cancer patients and no association with risk, OR, 1.30; 95% CI 0.69–2.47, P = 0.419). These data suggest that MDM2 SNP309 acts as a modifier of mutant BRCA1/2 mutant alleles in AJ and may accelerate breast and ovarian carcinogenesis in genetically predisposed individuals.     

Inherited predisposition to breast cancer: after the BRCA1 and BRCA2 genes,what next?

Germline mutations of the breast cancer predisposing known genes, BRCA1 and BRCA2, with an autosomal dominant transmission explain only a part of the familial aggregation of breast cancer. Mainly involved in families with cases of ovarian cancer or male breast cancer, they account for a small proportion of families where only female breast cancer cases are observed. A third predisposing gene, called BRCA3, has been sought for a long time but without success. Recently, genetic epidemiology studies have shown evidence for non-mendelian inheritance. The familial residual risk non due to BRCA1 or BRCA2 genes could be explain by a polygenic model, corresponding to the multiplicative effects of several genes, more frequent in population but conferring moderate risks of cancer. The identification of these low penetrance genes is the challenge over the next years. We present here a focusing of recent knowledge on breast cancer predisposing genes, the perspectives of research and their implications in the practice of genetic counselling.     

BRCA1 and ТР53 Gene-Mutations: Family Predisposition and Radioecological Risk of Developing Breast Cancer

Frequencies of polymorphisms of genes BRCA1 and ТР53 in breast cancer (BC) patients with a BC family history and radiation history were assessed and compared in the Semey region of Kazakhstan. The study included 60 women directly irradiated by the activities of the Semipalatinsk test site with a calculated effective equivalent dose of 500 mSv and their first generation descendants (group BC+Her+Exp); 65 women with family BC and absence of radiological history - the effective equivalent dose due to anthropogenic sources not exceeding 50 mSv (group BC+Her-Exp). The comparison group consisted of 65 women patients with breast cancer without family and radiological history (BC-Her-Exp). The control group comprised 60 women without breast cancer and without family and radiological history (nonBC). We carried out the genotyping of the polymorphisms c.2311T>C, c.4308T>C and 5382insC of the BRCA1 gene and rs1042522 of the ТР53 gene. The frequency of the polymorphism c.2311T>C was significantly higher in patients of the group BC+Her+Exp than in healthy women, and of the polymorphism 5382insC in BC+Her+Exp compared to all other groups. The frequency of the rs1042522 polymorphism of ТР53 was significantly higher in all groups of patients with breast cancer compared with the control group. Differences between groups of women with breast cancer were significant only in BC+Her+Exp vs. BC+Her-Exp. Combinations of polymorphisms of the genes BRCA1 and TP53 predominated in women with a family and radiological history.     

乳腺癌组织BRCA1,BRCA1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     

Baseline and post prophylactic tubal–ovarian surgery CA125 levels in BRCA1 and BRCA2 mutation carriers

The aim of this study was to determine whether BRCA1 and BRCA2 mutation carriers have different baseline CA125 levels compared with non-carriers, and whether a significant difference in pre- and post-operative CA125 levels exists in BRCA mutation carriers undergoing risk-reducing bilateral salpingo-oophorectomy (RRBSO). The study also considered whether CA125 measurements should continue in unaffected BRCA mutation carriers after RRBSO. 383 Eligible women were identified through retrospective review of the BRCA Carrier Clinic at The Royal Marsden NHS Foundation Trust, London, UK. These women all had CA125 levels measured as they were either a carrier or at risk of a BRCA1 or BRCA2 mutation. Of these, 76 went on to have a negative predictive test for their familial mutation and so are classed as ‘non-carriers’. 133 BRCA1 and 87 BRCA2 carriers had RRBSO, with a further 26 BRCA1 carriers, 28 BRCA2 carriers and one non-carrier developing ovarian cancer. The remaining 21 BRCA1 and 28 BRCA2 carriers did not have RRBSO or develop ovarian cancer in the time of study follow-up. CA125 levels were measured as surveillance or as part of pre-RRBSO care. CA125 measurement post-RRBSO was continued in 48 BRCA1 and 40 BRCA2 carriers. In 154 BRCA1 mutation carriers, the median baseline (i.e. before RRBSO and with no clinical signs of ovarian cancer) CA125 level was 9.0 U/ml (range 2–78) and was 10.0 U/ml (range 1–43) in 115 BRCA2 mutation carriers. When compared with the 75 non-carriers (median baseline CA125 10.0 U/ml; range 2–52), there was no significant difference between the BRCA1, BRCA2 and non-carrier groups. There was a significant reduction in CA125 from pre- to post-RRBSO in 48 BRCA1 carriers (p = 0.04) but no significant difference in 40 BRCA2 mutation carriers (p = 0.5). Out of a total of 220 mutation carriers who underwent RRBSO, two had an incidental ovarian cancer found on histopathology and another developed primary peritoneal cancer during the follow-up period. Our study is the first to compare initial serum CA125 levels in BRCA1 and BRCA2 mutation carriers with those of non-carriers. Our study found no significant difference between the three groups. A drop in CA125 levels after RRBSO in BRCA1 carriers supports the finding of earlier studies, but differed in that the fall was not seen in BRCA2 carriers. The finding of only one case of post-operative peritoneal cancer in 220 carriers undergoing RRBSO supports the discontinuation of post-RRBSO serum CA125 monitoring in BRCA mutation carriers.     

Are BRCA1- and BRCA2-related breast cancers associated with increased mortality?

There has been contradictory evidence as to whether BRCA1 associated breast cancers have a poorer prognosis than non-BRCA1 cancers. In this issue of Breast Cancer Research Robson and colleagues provide further evidence for poorer survival in BRCA1 carriers and show that it could be attributed to failure to treat small node-negative grade 3 breast cancers with chemotherapy. There still remains little evidence for a survival difference for BRCA2 related breast cancers. Although the high contralateral breast cancer risk is confirmed by this study there is no real evidence for an increase in ipsilateral recurrence or new primary breast cancers in mutation carriers up to the 10-year point.     

BRCA2 inhibition enhances cisplatin‐mediated alterations in tumor cell proliferation,metabolism, and metastasis

Tumor cells have unstable genomes relative to non‐tumor cells. Decreased DNA integrity resulting from tumor cell instability is important in generating favorable therapeutic indices, and intact DNA repair mediates resistance to therapy. Targeting DNA repair to promote the action of anti‐cancer agents is therefore an attractive therapeutic strategy. BRCA2 is involved in homologous recombination repair. BRCA2 defects increase cancer risk but, paradoxically, cancer patients with BRCA2 mutations have better survival rates. We queried TCGA data and found that BRCA2 alterations led to increased survival in patients with ovarian and endometrial cancer. We developed a BRCA2‐targeting second‐generation antisense oligonucleotide (ASO), which sensitized human lung, ovarian, and breast cancer cells to cisplatin by as much as 60%. BRCA2 ASO treatment overcame acquired cisplatin resistance in head and neck cancer cells, but induced minimal cisplatin sensitivity in non‐tumor cells. BRCA2 ASO plus cisplatin reduced respiration as an early event preceding cell death, concurrent with increased glucose uptake without a difference in glycolysis. BRCA2 ASO and cisplatin decreased metastatic frequency in vivo by 77%. These results implicate BRCA2 as a regulator of metastatic frequency and cellular metabolic response following cisplatin treatment. BRCA2 ASO, in combination with cisplatin, is a potential therapeutic anti‐cancer agent.     

Assessing ‘radiosensitivity’ with kinetic profiles of γ-H2AX, 53BP1 and BRCA1 foci

Background and purpose

DNA repair assays to identify radiosensitive patients have had limited clinical implementation due to long turn-around times or limited specificity. This study evaluates γ-H2AX-Irradiation Induced Foci (IRIF) kinetics as a more rapid surrogate for the ‘gold standard’ colony survival assay (CSA) using several known DNA repair disorders as reference models.

Materials and methods

Radiosensitive cells of known and unknown etiology were studied. γ-H2AX-IRIFs were quantified over 24 h, and the curves were fitted by combining logarithmic growth and exponential decay functions. Fitted values that differed from radionormal controls were considered aberrant and compared to CSA results.

Results

We observed 87% agreement of IRIF data with the CSA for the 14 samples tested. Analysis of γ-H2AX-IRIF kinetics for known repair disorders indicated similarities between an RNF168^−/− cell line and an RS cell of unknown etiology. These cell lines were further characterized by a reduction in BRCA1-IRIF formation and G2/M checkpoint activation.

Conclusions

γ-H2AX-IRIF kinetics showed high concordance with the CSA in RS populations demonstrating its potential as a more rapid surrogate assay. This method provides a means to globally identify defective DNA repair pathways in RS cells of unknown etiology through comparison with known DNA repair defects.     

Is no news good news? Inconclusive genetic test results in BRCA1 and BRCA2 from patients and professionals' perspectives

Background

Women from families with a high risk of breast or ovarian cancer in which genetic testing for mutations in the BRCA1/2 genes is inconclusive are a vulnerable and understudied group. Furthermore, there are no studies of the professional specialists who treat them - geneticists, genetic counsellors/nurses, oncologists, gynaecologists and breast surgeons.

Methods

We conducted a small qualitative study that investigated women who had developed breast cancer under the age of 45 and who had an inconclusive BRCA1/2 genetic diagnostic test (where no mutations or unclassified variants were identified). We arranged three focus groups for affected women and their close female relatives - 13 women took part. We also interviewed 12 health professionals who were involved in the care of these women.

Results

The majority of the women had a good grasp of the meaning of their own or a family member's inconclusive result, but a few indicated some misunderstanding. Most of the women in this study underwent the test for the benefit of others in the family and none mentioned that they were having the test purely for themselves. A difficult issue for sisters of affected women was whether or not to undertake prophylactic breast surgery. The professionals were sensitive to the difficulties in explaining an inconclusive result. Some felt frustrated that technology had not as yet provided them with a better tool for prediction of risk.

Conclusions

Some of the women were left with the dilemma of what decision to make regarding medical management of their cancer risk. For the most part, the professionals believed that the women should be supported in whatever management decisions they considered best, provided these decisions were based on a complete and accurate understanding of the genetic test that had taken place in the family.     

A gene-environment interaction between occupation and BRCA1/BRCA2 mutations in male breast cancer?

The association of male breast cancer (MBC) with a positive breast cancer (BC) family history and with BRCA1/2 germ-line mutations points to a genetic component; a relationship with occupation has also been reported. Recently, we identified pathogenetic BRCA1/2 mutations in a population-based series of Italian MBC patients: here in, we investigated interactions between a carrier status for BRCA1/2 mutations and occupation using a case-case design and estimating case-only odds ratios (CORs). Truck-driving was the most frequent occupation (3/4 BRCA-related cases and 2/19 unrelated cases). An interaction between carrier status and working as a truck-driver emerged, when we classified MBC cases as "ever/never-held" this job title (COR 25.5; 95% Confidence Limits (CL): 1.1-1,412.5) or according to truck-driving as the "longest-held" work (COR 54.0; 95% CL: 1.6-2,997.5). The possible modifying effect on MBC risk in subjects carrying BRCA1/2 germ-line mutations of an occupation characterised by exposure to chemicals such as polycyclic aromatic hydrocarbons (PAH) that are capable of inducing DNA damage, may provide clues to the role of environmental exposures in modifying BC risk in mutation carriers in both genders.