Prevalence of BRCA1 and BRCA2 gene mutations in patients with early-onset breast cancer

Genetic, functional, and histopathological evaluation of two C-terminal BRCA1 missense variants

BACKGROUND

The vast majority of BRCA1 missense sequence variants remain uncharacterized for their possible effect on protein expression and function, and therefore are unclassified in terms of their pathogenicity. BRCA1 plays diverse cellular roles and it is unlikely that any single functional assay will accurately reflect the total cellular implications of missense mutations in this gene.

OBJECTIVE

To elucidate the effect of two BRCA1 variants, 5236G>C (G1706A) and 5242C>A (A1708E) on BRCA1 function, and to survey the relative usefulness of several assays to direct the characterisation of other unclassified variants in BRCA genes.

METHODS AND RESULTS

Data from a range of bioinformatic, genetic, and histopathological analyses, and in vitro functional assays indicated that the 1708E variant was associated with the disruption of different cellular functions of BRCA1. In transient transfection experiments in T47D and 293T cells, the 1708E product was mislocalised to the cytoplasm and induced centrosome amplification in 293T cells. The 1708E variant also failed to transactivate transcription of reporter constructs in mammalian transcriptional transactivation assays. In contrast, the 1706A variant displayed a phenotype comparable to wildtype BRCA1 in these assays. Consistent with functional data, tumours from 1708E carriers showed typical BRCA1 pathology, while tumour material from 1706A carriers displayed few histopathological features associated with BRCA1 related tumours.

CONCLUSIONS

A comprehensive range of genetic, bioinformatic, and functional analyses have been combined for the characterisation of BRCA1 unclassified sequence variants. Consistent with the functional analyses, the combined odds of causality calculated for the 1706A variant after multifactorial likelihood analysis (1:142) indicates a definitive classification of this variant as "benign". In contrast, functional assays of the 1708E variant indicate that it is pathogenic, possibly through subcellular mislocalisation. However, the combined odds of 262:1 in favour of causality of this variant does not meet the minimal ratio of 1000:1 for classification as pathogenic, and A1708E remains formally designated as unclassified. Our findings highlight the importance of comprehensive genetic information, together with detailed functional analysis for the definitive categorisation of unclassified sequence variants. This combination of analyses may have direct application to the characterisation of other unclassified variants in BRCA1 and BRCA2.

Chromosomal radiosensitivity in BRCA1 and BRCA2 mutation carriers

PURPOSE

The chromosomal radiosensitivity of a selected group of familial breast cancer patients carrying a mutation in BRCA1 (n=11) or BRCA2 (n=9) and a group of healthy mutation carriers (n=12) was investigated and compared to a reference group of breast cancer patients without a BRCA1/2 mutation (n=78) and a group of healthy women carrying no mutation (n=58).

MATERIALS AND METHODS

The chromosomal radiosensitivity was assessed with the G2 and the G0-micronucleus (MN)-assay on fresh blood samples and on Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines. For the MN-assay, lymphocytes were exposed in vitro to 3.5 Gy and 2 Gy 60Co gamma-rays at a high dose rate (HDR) or low dose rate (LDR). 70-h post-irradiation cultures were arrested and micronuclei were scored in 1000 binucleate cells. For the G2-assay lymphocytes were irradiated in vitro with a dose of 0.4 Gy 60Co gamma-rays after 71h incubation. Cultures were arrested 90 min after irradiation and chromatid breaks were scored in 50 metaphases.

RESULTS

The group of breast cancer patients with a BRCA1 or 2 mutation was on average more radiosensitive than the control group, but not different from breast cancer patients without a BRCA mutation. The radiation response of healthy BRCA1/2 carriers was not significantly different from the control group and also not different from relatives without a BRCA mutation. Comparing the radiation response in EBV cell lines derived from breast cancer patients with or without a BRCA1 mutation revealed no significant difference.

CONCLUSIONS

Our results reveal that chromosomal radiosensitivity observed in breast cancer patients heterozygous for BRCA1 or 2 mutations, could not be demonstrated in healthy BRCA1/2 mutation carriers. This suggests that mutations in BRCA1 or 2 genes are not playing a main role in chromosomal radiosensitivity, this although BRCA1 and 2 are both involved in DNA repair/signalling processes.

Comparison of genomic abnormalities between BRCAX and sporadic breast cancers studied by comparative genomic hybridization

Very little is known about the chromosomal regions harbouring genes involved in initiation and progression of BRCAX-associated breast cancers. We applied comparative genomic hybridization (CGH) to identify the most frequent genomic imbalances in 18 BRCAX hereditary breast cancers and compared them to chromosomal aberrations detected in a group of 27 sporadic breast cancers. The aberrations observed most frequently in BRCAX tumours were gains of 8q (83%), 19q (67%), 19p (61%), 20q (61%), 1q (56%), 17q (56%) and losses of 8p (56%), 11q (44%) and 13q (33%). The sporadic cases most frequently showed gains of 1q (67%), 8q (48%), 17q (37%), 16p (33%), 19q (33%) and losses of 11q (26%), 8p (22%) and 16q (19%). Losses of 8p and gains 8q, 19 as well as gains of 20q (with respect to ductal tumours only) were detected significantly more often in BRCAX than in sporadic breast cancers. Analysis of 8p-losses and 8q-gains showed that these aberrations are early events in the tumorigenesis of BRCAX tumors. The findings of this report indicate similarities between BRCAX and BRCA2 tumours, possibly suggesting a common pathway of disease. These findings need confirmation by more extensive studies because only a limited number of cases were analysed and there are relatively few reports published.

Differential association of BRCA1 and BRCA2 genes with some breast cancer-associated genes in early and late onset breast tumors

BACKGROUND

Accumulating evidence indicating more aggressive features of breast carcinoma (BC) in young women than their older counterparts have raised the question of whether these differences are present at the genetic level.

METHODS

For this purpose, we performed a comparative analysis of the frequency of deletions of BRCA1, BRCA2, BRCAX, TP53, ATM, and RB1 and amplification of Cyclin D1 and also studied the interrelation and prognostic significance of these genetic alterations in 30 early onset (< or =40 years) and 33 late onset (>40 years) cases of BC. These gene alterations were also studied in 11 other types of breast lesions.

RESULTS

A differential pattern of alterations (deletion/amplification) was observed in the two age groups, with the sequence in younger women being BRCA1 (72%), TP53 (71%), ATM (64%), BRCA2 (62%), RB1 (60%), Cyclin D1 (43%), and BRCAX (24%) and that in the older group being TP53 (66%), RB1 (63%), BRCA1 (56%), ATM (53%), BRCA2 (45%), Cyclin D1 (24%), and BRCAX (23%). Similar, differential correlations were also seen with several clinicopathological parameters, prognosis, and combinations of alterations among these genes in the two age groups.

CONCLUSIONS

Differential frequencies and interrelationships of genetic alterations and prognoses in these two age groups indicate that the molecular pathways for the development of tumors in both age groups may not be similar, though the ultimate effect is deregulation of cell cycle checkpoints and defects in the DNA repair pathway.

Knowledge, Attitudes, and Utilization of BRCA1/2 Testing among Women with Early-Onset Breast Cancer

A total of 2,400 questionnaires were mailed to members of two mid-Atlantic breast cancer awareness/support groups to investigate the association between attitudes, knowledge, and use of BRCA1/2 testing among women with early-onset breast cancer. Of the 493 (21%) questionnaires returned, 406 respondents had a diagnosis of breast cancer, of whom 248 were diagnosed prior to age 50 and included in the analyses. Eighty-three percent (206/248) of these women had heard of BRCA1/2 testing and 12.5% (31/248) had undergone BRCA1/2 testing. Among women who had heard of BRCA1/2 testing, women who had been tested were younger (p = 0.03), more likely to have a college education (p = 0.03), more likely to have a family member who had undergone BRCA1/2 testing (p = 0.005), and had greater knowledge, more positive attitudes, and fewer negative attitudes about BRCA1/2 testing (p = 0.02, p = 0.004, and p = 0.004, respectively). In this sample, knowledge regarding BRCA1/2 testing is high, but uptake of genetic testing is low. Lack of information regarding how genetic testing might alter health-care decisions and fear about the genetic testing procedure, its costs, and possible false-positive results are associated with low uptake of genetic testing. Further education regarding these specific points may enhance the use of genetic testing.

Polygenic inherited predisposition to breast cancer

The known breast cancer predisposing genes account for only about 20% of inherited susceptibility. Epidemiological analyses suggest that much of the remaining 80% is explained by the combined effect of many individually weak genetic variants, rather than by further rare, highly penetrant mutations. In the near term, identification of variants may indicate new pathways or mechanisms in breast cancer development. The polygenic model implies a wide distribution of risk in the population. In the longer term, it may be possible to construct individual risk profiles to guide public health interventions. The search for genetic variants has so far proved difficult. A key unanswered question is the "genetic architecture" of predisposition-that is, strong or weak alleles, common or rare. We describe a genome-wide scan designed to provide a first-pass answer to this question.

An Autosome-Wide Scan for Linkage Disequilibrium–Based Association in Sporadic Breast Cancer Cases in Eastern Finland: Three Candidate Regions Found

Breast cancer is the most common of cancers among women in industrialized countries. Many of breast cancer risk factors are known, but the majority of the genetic background is still unknown. Linkage disequilibrium–based association is a powerful tool for mapping disease genes and is suitable for mapping complex traits in founder populations. We report the results of a two-stage, autosome-wide scan for LD with breast cancer. Our aim was to identify genetic risk factors for sporadic breast cancer in an eastern Finnish population. Our case-control set is from the province of northern Savo in the late-settlement area of eastern Finland. This population is relatively young and genetically homogeneous. We used 435 autosomal microsatellite markers spaced by an average of 10 cM in a set of 49 breast cancer cases and 50 controls. In the first-stage scan, we found 21 markers in LD with breast cancer (Ps = 0.003-0.046, Fisher's exact test). In the second-stage scan with markers flanking 21 positive loci, four significant markers were found (Ps = 0.013-0.046, Fisher's exact test). Haplotype analysis using global score method with two, three, or four markers also revealed four positive marker combinations (simulated P for global score = 0.003-0.021). Our results suggest breast cancer–associated regions on 3p26, 11q23, and 22q13.1 in an eastern Finnish population.

Dog star rising: the canine genetic system

Purebred dogs are providing invaluable information about morphology, behaviour and complex diseases, both of themselves and humans, by supplying tractable populations in which to map genes that control those processes. The diversification of dog breeds has led to the development of breeds enriched for particular genetic disorders, the mapping and cloning of which have been facilitated by the availability of the canine genome map and sequence. These tools have aided our understanding of canine population genetics, linkage disequilibrium and haplotype sharing in the dog, and have informed ongoing efforts of the need to identify quantitative trait loci that are important in complex traits.

Young age: an independent risk factor for disease-free survival in women with operable breast cancer

Background

The incidence of breast cancer in young women (age < 35) is low. The biology of the disease in this age group is poorly understood, and there are conflicting data regarding the prognosis for these women compared to older patients.

Methods

We retrospectively analyzed 2040 consecutive primary invasive breast cancer patients who underwent surgical procedures at our institution between 1990 and 1999. The younger age group was defined as patients aged <35 years at the time of diagnosis. The clinicopathological characteristics and treatment outcomes were compared between younger and older age groups.

Results

A total of 256 (12.5%) patients were aged <35. There was a significantly higher incidence of nuclear grade 3 and medullary histological-type tumors in younger patients compared to older patients. Axillary lymph node status, T stage, histological grade, c-erbB2 expression and estrogen receptor status did not differ significantly between the two age groups. Younger patients had a greater probability of recurrence and death at all time periods. Although there was no significant difference in disease-free survival between the two age groups in lymph node-negative patients, the younger group showed worse prognosis among lymph node-positive patients (p < 0.001). In multivariate analysis, young age remained a significant predictor of recurrence (p = 0.010).

Conclusion

Young age (<35) is an independent risk factor for relapse in operable breast cancer patients.

Finding prostate cancer susceptibility genes

Prostate cancer is a heterogeneous disease with multiple loci contributing to susceptibility. Traditionally, genome-wide scans using high-risk families have utilized stratification by number of affected individuals, family history of other cancers, or family age at diagnosis to improve genetic homogeneity. In addition to locus heterogeneity, for later onset diseases such as prostate cancer, a major limitation to mapping efforts is that key parental DNA samples are rarely available. The lack of available samples from upper generations reduces inheritance information, and as a result, the standard 10-cM genome scan does not provide full power to detect linkage. To increase the ability to find disease-associated loci, much denser genome-wide scans must be undertaken in multiple ethnic groups. In addition, new ways of defining homogenous subsets of families need to be developed.

The BOADICEA model of genetic susceptibility to breast and ovarian cancer

Several genes conferring susceptibility to breast and ovarian cancer, notably BRCA1 and BRCA2, have been identified. The majority of the familial aggregation of breast cancer is, however, not explained by these genes. We have previously derived, using segregation analysis, a susceptibility model (BOADICEA, Breast and Ovarian Analysis of Disease Incidence and Carrier Estimation Algorithm) in which susceptibility to these genes is explained by mutations in BRCA1 and BRCA2 together with a polygenic component reflecting the joint multiplicative effect of multiple genes of small effect on breast cancer risk. Here, we consider the predictions made by this model. The overall familial risks of breast cancer predicted by this model are close to those observed in epidemiological studies. The predicted prevalences of BRCA1 and BRCA2 mutations among unselected cases of breast and ovarian cancer are also consistent with observations from population-based studies. These predictions are closer to the observed values than those obtained using the Claus model and BRCAPRO. The predicted mutation probabilities and cancer risks in individuals with a family history (FH) can differ markedly from those predicted by other models. We conclude that this model provides a rational basis for risk assessment in individuals with a FH of breast or ovarian cancer.

Breast Cancer Surveillance in Women with Hereditary Risk Due to BRCA1 or BRCA2 Mutations

Women with germline mutations in BRCA1 or BRCA2 are known to be at substantially elevated risk for breast cancer. With increasing acceptance of genetic testing, significant numbers of mutation carriers are being identified, but evidence-based guidelines for the management of women at hereditary risk are lacking. This article reviews the most commonly recommended modalities employed in breast cancer surveillance for women at increased risk. It is apparent that the standard techniques of breast self-examination, clinical breast examination, and mammography are suboptimal for the identification of hereditary breast cancer. At least half of the cancers in this population appear to be detected by physical examination in the intervals between routine radiographic surveillance. Host factors (eg, breast density) and tumor features (rapid proliferative rates) likely contribute to the relative insensitivity of mammography. These factors may be mitigated by the deployment of screening techniques for breast cancer such as ultrasound and magnetic resonance imaging. However, the effect of incremental screening on either stage at diagnosis or breast cancer mortality has not been defined. In addition, the impact of the relatively limited specificity of these techniques on the quality of life (QOL) of women at risk has not been studied. Further research is needed to evaluate the effect of incremental radiographic screening on outcomes, to delineate the best way to integrate the different modalities in terms of sequencing and frequency, and to identify interventions that will minimize the impact of intensive surveillance programs on the QOL of the women engaged in them.

Young age and outcome for women with early-stage invasive breast carcinoma

BACKGROUND

Patients with invasive breast carcinoma who are ages 35-40 years or younger at the time of diagnosis have been found in several studies to have worse prognosis and higher local failure rates after breast-conserving therapy (BCT) compared with older patients. However, it is uncertain whether specific clinical, pathologic, or treatment factors affect these results, or whether mastectomy yields a better outcome.

METHODS

Articles addressing how patient age at the time of diagnosis affects treatment outcome were identified through the MEDLINE and CancerLit databases and the reference lists of relevant articles.

RESULTS

Young age was found to remain an independent risk factor for worse outcome after either BCT or mastectomy. Limited evidence did not demonstrate a superior outcome with mastectomy compared with BCT. Recent studies of BCT still reported young age to be associated with higher local recurrence rates compared with that for older patients, but their interpretation was hampered by inadequate margin assessment for ductal carcinoma in situ. Adjuvant chemotherapy has been found to improve local control rates substantially for young patients after BCT.

CONCLUSIONS

To the authors' knowledge, there are insufficient data to determine whether young patients have superior long-term outcome if treated by mastectomy compared with BCT, or whether having truly uninvolved margins abrogates their increased risk of local failure after BCT. When meticulous attention is given to surgical techniques and margin status, it appears that young age at the time of diagnosis need not be a contraindication to BCT.

A new scoring system for the chances of identifying a BRCA1/2 mutation outperforms existing models including BRCAPRO

PURPOSE

To develop a simple scoring system for the likelihood of identifying a BRCA1 or BRCA2 mutation.

METHODS

DNA samples from affected subjects from 422 non-Jewish families with a history of breast and/or ovarian cancer were screened for BRCA1 mutations and a subset of 318 was screened for BRCA2 by whole gene screening techniques. Using a combination of results from screening and the family history of mutation negative and positive kindreds, a simple scoring system (Manchester scoring system) was devised to predict pathogenic mutations and particularly to discriminate at the 10% likelihood level. A second separate dataset of 192 samples was subsequently used to test the model's predictive value. This was further validated on a third set of 258 samples and compared against existing models.

RESULTS

The scoring system includes a cut-off at 10 points for each gene. This equates to >10% probability of a pathogenic mutation in BRCA1 and BRCA2 individually. The Manchester scoring system had the best trade-off between sensitivity and specificity at 10% prediction for the presence of mutations as shown by its highest C-statistic and was far superior to BRCAPRO.

CONCLUSION

The scoring system is useful in identifying mutations particularly in BRCA2. The algorithm may need modifying to include pathological data when calculating whether to screen for BRCA1 mutations. It is considerably less time-consuming for clinicians than using computer models and if implemented routinely in clinical practice will aid in selecting families most suitable for DNA sampling for diagnostic testing.

Breast cancer genetics: unsolved questions and open perspectives in an expanding clinical practice

Breast cancer is the most common cause of cancer death in the United Kingdom, with a lifetime risk of one in nine in women. Only 5-10% of all cancers is thought to be due to strongly penetrant inherited predisposing genes, such as BRCA1 and BRCA2. However, other less penetrant genes, including some autosomal recessive genes, are likely to be of etiological importance in other families. This review addresses the current knowledge of breast cancer susceptibility genes and explores the possibilities for future developments. Features of tumor pathology, prognosis, and the scope for targeted treatments in mutation carriers are discussed, and the management of known carriers and those at increased risk for developing breast cancer are evaluated. Genetic testing for cancer susceptibility may become widely available in the future, and has important ethical and management implications.

Cancer genetics in primary care

The cloning of two major breast cancer susceptibility genes, BRCA1 and BRCA2, in 1994 and 1995 and the subsequent development of commercial genetic testing has brought hereditary cancer genetics into the public eye. In addition to DNA-based genetic testing, new strategies and treatments have been developed to provide accurate assessment of cancer risk and to reduce the chances of cancer developing in the future. This increasing scientific and public attention has prompted some cancer patients and their families to find out whether they "have the cancer gene" and has placed more responsibility on primary care clinicians to identify people who should be referred for specialized services of hereditary cancer genetics.

Penetrances of breast and ovarian cancer in a large series of families tested for BRCA1/2 mutations

Accurate estimates of breast and ovarian cancer penetrance in BRCA1/2 mutation carriers are crucial in genetic counseling. Estimation is difficult because of the low frequency of mutated alleles and the often-uncertain mechanisms of family ascertainment. We estimated the penetrances of breast and ovarian cancers in carriers of BRCA1/2 mutations by maximizing the retrospective likelihood of the genetic model, given the observed test results, in 568 Italian families screened for germline mutations. The software BRCAPRO was used as a probability calculation tool in a Markov Chain Monte Carlo approach. Breast cancer penetrances were 27% (95% CI 20-34%) at age 50 years and 39% (27-52%) at age 70 in BRCA1 carriers, and 26% (0.18-0.34%) at age 50 and 44% (29-58%) at age 70 in BRCA2 carriers, and ovarian cancer penetrances were 14% (7-22%) at age 50 and 43% (21-66%) at age 70 in BRCA1 carriers and 3% (0-7%) at age 50 and 15% (4-26%) at age 70 in BRCA2 carriers. The new model gave a better fit than the current default in BRCAPRO, the likelihood being 70 log units greater; in addition, the observed numbers of mutations in families stratified by gene and by cancer profile were not significantly different from those expected. Our new penetrance functions are appropriate for predicting breast cancer risk, and for determining the probability of carrying BRCA1/2 mutations, in people who are presently referred to genetic counseling in Italy. Our approach could lead to country-customized versions of the BRCAPRO software by providing appropriate population-specific estimates.

A breast cancer prediction model incorporating familial and personal risk factors

Many factors determine a woman's risk of breast cancer. Some of them are genetic and relate to family history, others are based on personal factors such as reproductive history and medical history. While many papers have concentrated on subsets of these risk factors, no papers have incorporated personal risk factors with a detailed genetic analysis. There is a need to combine these factors to provide a better overall determinant of risk. The discovery of the BRCA1 and BRCA2 genes has explained some of the genetic determinants of breast cancer risk, but these genes alone do not explain all of the familial aggregation of breast cancer. We have developed a model incorporating the BRCA genes, a low penetrance gene and personal risk factors. For an individual woman her family history is used in conjuction with Bayes theorem to iteratively produce the likelihood of her carrying any genes predisposing to breast cancer, which in turn affects her likelihood of developing breast cancer. This risk was further refined based on the woman's personal history. The model has been incorporated into a computer program that gives a personalised risk estimate.

The Breast Cancer Family Registry: an infrastructure for cooperative multinational, interdisciplinary and translational studies of the genetic epidemiology of breast cancer

INTRODUCTION

The etiology of familial breast cancer is complex and involves genetic and environmental factors such as hormonal and lifestyle factors. Understanding familial aggregation is a key to understanding the causes of breast cancer and to facilitating the development of effective prevention and therapy. To address urgent research questions and to expedite the translation of research results to the clinical setting, the National Cancer Institute (USA) supported in 1995 the establishment of a novel research infrastructure, the Breast Cancer Family Registry, a collaboration of six academic and research institutions and their medical affiliates in the USA, Canada, and Australia.

METHODS

The sites have developed core family history and epidemiology questionnaires, data dictionaries, and common protocols for biospecimen collection and processing and pathology review. An Informatics Center has been established to collate, manage, and distribute core data.

RESULTS

As of September 2003, 9116 population-based and 2834 clinic-based families have been enrolled, including 2346 families from minority populations. Epidemiology questionnaire data are available for 6779 affected probands (with a personal history of breast cancer), 4116 unaffected probands, and 16,526 relatives with or without a personal history of breast or ovarian cancer. The biospecimen repository contains blood or mouthwash samples for 6316 affected probands, 2966 unaffected probands, and 10,763 relatives, and tumor tissue samples for 4293 individuals.

CONCLUSION

This resource is available to internal and external researchers for collaborative, interdisciplinary, and translational studies of the genetic epidemiology of breast cancer. Detailed information can be found at the URL http://www.cfr.epi.uci.edu/.

Incidence of BRCA1 and BRCA2 Mutations in Young Korean Breast Cancer Patients

Purpose

The prevalence of BRCA-associated breast carcinoma in the Korean population has not been evaluated extensively.

Methods

Sixty Korean women who developed breast cancer by age 40 years were studied. Lymphocyte specimens from peripheral blood were processed for BRCA1 and BRCA2 by complete sequencing. Family history through three generations was obtained. Available paraffin-embedded tissue blocks were processed for immunohistochemical staining.

Results

In the cohort of 60 patients, nine patients with 11 deleterious mutations (six in BRCA1 and five in BRCA2) and seven missense mutations of unknown significance were found. Two patients had deleterious mutations in both BRCA1 and BRCA2 (double mutant). One half of the mutations were novel, and no founder mutations were observed in this cohort. Most of the BRCA-associated patients had no family history of breast and/or ovarian cancer. The expression of HER-2/neu, cyclin D1, and hormone receptors was less common, and p53 overexpression was more common in BRCA-associated tumors.

Conclusion

The prevalence of BRCA1 and BRCA2 mutations in Korean women with breast cancer at a young age was high. However, the penetrance, as evidenced by the low frequency of breast and ovarian cancers in family members, appears to be low. These data suggest that there may be different genetic and etiologic factors affecting transmission and penetrance of the BRCA genes in Korean patients with breast cancer diagnosed at a young age.

Epidemiology of breast cancer among BRCA mutation carriers: an overview

Mutations in BRCA1 and BRCA2 have been associated with an increased lifetime risk of breast and ovarian cancers. Many of the well-recognized risk factors and risk modifiers in other women appear to operate similarly in BRCA mutation carriers. However, current evidence suggests that BRCA-related breast cancer risk is positively associated with pregnancy and parity, while smoking may reduce the risk. The incidence of BRCA1-related breast cancer is high before the age of 35 years and oral contraceptive use for 5 or more years is associated with increased risk of this disease among women carrying BRCA1 mutations.

Prevalence of BRCA1 and BRCA2 mutations in Korean breast cancer patients

The incidence of breast cancer in Korea has been increasing in recent years, such that it is now the most common female cancer. Breast cancer in Korea is characterized by an earlier age of onset than in Western countries, suggesting that it would be related with genetic background. We assayed germline mutations in the BRCA genes to evaluate their genetic pathology in Korean breast cancer patients. The study subjects consisted of 173 patients at clinically higher risk and 109 unselected patients. Germline mutations in the entire coding sequences of the BRCA1 and BRCA2 genes were analyzed by Conformation-Sensitive Gel Electrophoresis (CSGE), and any aberrantly-sized band was sequenced. BRCA mutations were present in 12.7% of the high risk patients, compared with 2.8% of the unselected patients. Among high risk patients, mutations were most prevalent in patients with a family history of breast or first-degree ovarian cancer (22.1%), followed by those with male breast cancer (20%), bilateral breast cancer (20%), multiple organ cancer including breast (13%) and younger breast cancer patients (aged<35 yr) (8.1%). Moreover, BRCA mutations were detected in 34.8% of patients having two high risk factors. These findings suggest that BRCA gene mutation analysis should be performed on Korean patients with high-risk factors for breast cancer.

Kin-cohort estimates for familial breast cancer risk in relation to variants in DNA base excision repair, BRCA1 interacting and growth factor genes

BACKGROUND

Subtle functional deficiencies in highly conserved DNA repair or growth regulatory processes resulting from polymorphic variation may increase genetic susceptibility to breast cancer. Polymorphisms in DNA repair genes can impact protein function leading to genomic instability facilitated by growth stimulation and increased cancer risk. Thus, 19 single nucleotide polymorphisms (SNPs) in eight genes involved in base excision repair (XRCC1, APEX, POLD1), BRCA1 protein interaction (BRIP1, ZNF350, BRCA2), and growth regulation (TGFss1, IGFBP3) were evaluated.

METHODS

Genomic DNA samples were used in Taqman 5'-nuclease assays for most SNPs. Breast cancer risk to ages 50 and 70 were estimated using the kin-cohort method in which genotypes of relatives are inferred based on the known genotype of the index subject and Mendelian inheritance patterns. Family cancer history data was collected from a series of genotyped breast cancer cases (N = 748) identified within a cohort of female US radiologic technologists. Among 2,430 female first-degree relatives of cases, 190 breast cancers were reported.

RESULTS

Genotypes associated with increased risk were: XRCC1 R194W (WW and RW vs. RR, cumulative risk up to age 70, risk ratio (RR) = 2.3; 95% CI 1.3-3.8); XRCC1 R399Q (QQ vs. RR, cumulative risk up to age 70, RR = 1.9; 1.1-3.9); and BRIP1 (or BACH1) P919S (SS vs. PP, cumulative risk up to age 50, RR = 6.9; 1.6-29.3). The risk for those heterozygous for BRCA2 N372H and APEX D148E were significantly lower than risks for homozygotes of either allele, and these were the only two results that remained significant after adjusting for multiple comparisons. No associations with breast cancer were observed for: APEX Q51H; XRCC1 R280H; IGFPB3 -202A>C; TGFss1 L10P, P25R, and T263I; BRCA2 N289H and T1915M; BRIP1 -64A>C; and ZNF350 (or ZBRK1) 1845C>T, L66P, R501S, and S472P.

CONCLUSION

Some variants in genes within the base-excision repair pathway (XRCC1) and BRCA1 interacting proteins (BRIP1) may play a role as low penetrance breast cancer risk alleles. Previous association studies of breast cancer and BRCA2 N372H and functional observations for APEX D148E ran counter to our findings of decreased risks. Due to the many comparisons, cautious interpretation and replication of these relationships are warranted.

Prevention and genetic testing for breast cancer: variations in medical decisions

The discovery linking the genes BRCA1&2 to familial breast cancer played an important role in the clinical practice of geneticists and physicians. The availability of genetic tests for BRCA gene mutations prompted cancer geneticists to give information about genetic risk and to assess many women with a personal or family history of breast or ovarian cancer to inform them of preventive measures. These consist mainly of breast self-examination, mammography screening, chemoprevention and prophylactic surgery (mastectomy, oophorectomy). This paper examines clinical practices related to hereditary breast cancer testing and introduces a number of results from a survey carried out, between 1996 and 1998, in three clinics located in Montreal (Quebec, Canada), Marseilles (France) and Manchester (Great Britain). Results show substantial differences in the way cancer geneticists deal with environmental risk factors, breast and ovarian cancer testing, and chemoprevention and prophylactic surgery. Differences across cities persist in the multivariate analysis, suggesting that attitudes towards preventive measures may be partially explained by cultural factors. Different dimensions of culture are discussed including the social representation of health and risk, the interpretation of scientific evidence and the role of innovation leadership.

Referral for cancer genetics consultation: a review and compilation of risk assessment criteria

BACKGROUND

There have been many papers on the diagnostic criteria for specific hereditary cancer susceptibility syndromes and the likelihood that an individual has a germline mutation in one of the various cancer susceptibility genes. To assist health care professionals in deciding when a cancer genetics consultation is appropriate, available reports were critically reviewed in order to develop a single set of risk assessment criteria.

METHODS

The criteria were based on a comprehensive review of publications describing diagnostic criteria for hereditary cancer syndromes and risk to first degree relatives of cancer patients. Priority was given to diagnostic criteria from consensus statements (for example, those from the National Comprehensive Cancer Network). Expert opinion from study personnel was then used to adopt a single set of criteria from other publications whenever guidelines differed.

RESULTS

Based on family history, a set of criteria was developed to identify patients at risk for a hereditary cancer susceptibility syndrome, patients with moderate risk who might benefit from increased cancer surveillance, and patients who are at average risk. The criteria were applied to 4360 individuals who provided their cancer family history between July 1999 and April 2002, using a touch screen computer system in the lobby of a comprehensive cancer centre. They categorised an acceptable number of users into each risk level: 14.9% high risk, 13.7% moderate risk, and 59.6% average risk; 11.8% provided insufficient information for risk assessment.

CONCLUSIONS

These criteria should improve ease of referral and promote consistency across centres when evaluating patients for referral to cancer genetics specialists.

BRCA1 and BRCA2 Mutations in Women from Shanghai China

Little is known about the frequency of germ-line mutations in the breast cancer susceptibility genes BRCA1 and BRCA2 among Asian populations. We investigated the distribution of BRCA1 and BRCA2 germ-line mutations and polymorphisms in a cohort of women from Shanghai, China. Study subjects totaled 1306, and included 645 women with breast cancer, 342 women with benign breast disease, and 319 unaffected controls, born between 1924 and 1958, selected from women enrolled in a randomized trial of Breast Self-Examination in Shanghai, China. Women were selected without regard to family history of breast or ovarian cancer. All of the coding regions and exon-intron boundaries were screened. Data were analyzed with respect to age at diagnosis, and family history of breast and ovarian cancer. The prevalence of known disease-associated mutations in women with breast cancer was 1.1% each, for BRCA1 and BRCA2. Among breast cancer cases with a family history of breast or ovarian cancer, 8.1% and 2.7% carried likely BRCA1 and BRCA2 disease-associated mutations, respectively. Overall, these results suggest that inherited susceptibility to breast cancer due to germ-line BRCA1/2 mutations among women with a family history of breast cancer is comparable between women from Shanghai and Caucasian women of Western European descent. Most alterations observed appear unique to the Chinese population, suggesting a resource that will be useful for assessing risk among both Chinese women and United States women of Chinese descent.

Implications of the age range in a population-based BRCA1 testing program with eligibility based on family history of breast and ovarian cancer

The current options available to BRCA1 mutation carriers can be classified as either cancer risk reduction or increased disease surveillance. Risk reduction might be preferable to young women. Increased surveillance might be more attractive to women when their cancer risk is highest. The aim of this report is to estimate the sensitivity, specificity and ability to detect carriers for a population-based BRCA1 testing program with eligibility based on family history of cancer, and examine the effect of age on the program's performance. A computer model was used to simulate the incidence of breast and ovarian cancer in a woman's family, based on her BRCA1 mutation carrier status. Age-specific estimates of the sensitivity and specificity for family history as an indicator of mutation status were applied to local population figures. Sensitivity of the program increased with the age of the proband and the size of her family. Sensitivity ranged from 0.33 for 20-year-olds with small families, to 0.98 for 60-year-olds with large families. Specificity was greater than 0.95, regardless of a woman's age or family size. If 0.12% of people carry a BRCA1 mutation, a province-wide testing program for people aged 20-69 with referrals based only on family history would have a sensitivity of 0.55. Only 2% of the genetic test results would be positive. The acceptability of a genetic testing program depends on its sensitivity and specificity, and on the options available to women who are found to carry a mutation. Compared with variation due to family size, the program sensitivity and specificity does not differ substantially amongst the various age groups.

Significant proportion of breast and/or ovarian cancer families of French Canadian descent harbor 1 of 5BRCA1 andBRCA2 mutations

In 1998, we reported that a significant proportion of breast and/or ovarian cancer families of French Canadian descent harbor specific germline mutations in BRCA1 or BRCA2 attributed to common founders. Here we report the frequency of previously described mutations (n = 7) and 13 mutations identified in French Canadian families since 1998, in a new group of families (n = 88). Four of the previously described mutations, 4446C>T, 2953delGTAinsC, 8765delAG and 6085C>T, account for 72% and 69% of mutation-positive families in previously (n = 81) and recently ascertained groups, respectively. Only 2 of 13 recently identified mutations were found in more than 1 family: 3875delGTCT (n = 2) and 3398delAAAAG (n = 4). The 2 groups (ascertained pre- and post-gene discovery) did not differ significantly when distribution of mutations based on cancer syndrome phenotype and age of diagnosis or number of breast cancer cases were compared. Five common mutations accounted for a significant proportion (84%) of all mutation-positive families. The age of diagnosis of female breast cancer in mutation-negative families was significantly higher than that of the mutation-positive families (p<0.0001). The total number of cases of cancer per family was significantly lower in mutation-negative than mutation-positive families (p<0.001). Our results define a new mutation panel for screening BRCA1/2 mutations and the phenotype of mutation-positive families harboring the common mutations in the French Canadian population.

Hereditary breast cancer in Jews

A family history of breast cancer poses higher risks for Jewish versus non-Jewish women, particularly for early-onset breast cancer. This appears to be due in large part to the high prevalence (2.5%) of three BRCA1 and BRCA2 founder mutations in Ashkenazi Jews. About 4 to 8% of non-Jewish male breast cancer cases versus 19% of Jewish male breast cancer cases carry germline BRCA mutations. Jewish women are disproportionately impacted by BRCA mutations throughout life, with a 10% carrier rate for breast cancer diagnosed at any age and a 21 to 30% carrier rate for breast cancer diagnosed by age 40. Comparable rates in non-Jewish populations are 6.1% for breast cancer diagnosed before age 50. Lifetime penetrance estimates based on genotyping of probands have ranged widely in Jewish and non-Jewish populations. However, a study of 1008 Jewish women with breast cancer which extended genotyping to relatives found high penetrance rates with considerably smaller standard errors. This study and studies of early-onset incident breast cancer in non-Jews have found that at least half of high-risk cases would be missed by family history screening alone. While the carrier rate in non-Jewish populations is too low to consider genetic screening, the carrier rate in Ashkenazi Jews is high and genetic screening poses fewer technical barriers. The high genetic attributable cancer risks of Ashkenazi BRCA founder mutations, the sobering lethality of ovarian and early onset breast cancers, and the increasing clarity about effectiveness of medical interventions make imperative further dialogue and research to keep guidelines for genetic screening up to date.

Risk Estimation for Healthy Women from Breast Cancer Families: New Insights and New Strategies

Risk estimation in breast cancer families is often estimated by use of the Claus tables. We analyzed the family histories of 196 counselees; compared the Claus tables with the Claus, the BRCA1/2, the BRCA1/2/ models; and performed linear regression analysis to extend the Claus tables with characteristics of hereditary breast cancer. Finally, we compared the Claus extended method with the Claus, the BRCA1/2, and the BRCA1/2/u models. We found 47% agreement for Claus table versus Claus model; 39% agreement for Claus table versus BRCA1/2 model; 48% agreement for Claus table versus BRCA1/2/u model; 37% agreement for Claus extended method versus Claus model; 44% agreement for Claus extended model versus BRCA1/2 model; and 66% agreement for Claus extended method versus BRCA1/2/u model. The regression formula (Claus extended method) for the lifetime risk for breast cancer was 0.08 + 0.40 (*) Claus Table + 0.07 (*) ovarian cancer + 0.08 (*) bilateral breast cancer + 0.07 (*) multiple cases. This new method for risk estimation, which is an extension of the Claus tables, incorporates information on the presence of ovarian cancer, bilateral breast cancer, and whether there are more than two affected relatives with breast cancer. This extension might offer a good alternative for breast cancer risk estimation in clinical practice.

The effect of disease penetrance, family size, and age of onset on family history with application to setting eligibility criteria for genetic testing

The concept of family history of disease has been used as a surrogate for genetic susceptibility in many epidemiological studies and has also been important as a criterion for selecting individuals for genetic testing. However, little is known about the precise interplay between the true genetic model (genotype-specific penetrances, age of onset distribution), life expectancy, and reproductive patterns in determining the level of family history. In order to address these questions, we performed a simulation study to address these relationships. Factors examined were the age-, sex-, and genotype-specific penetrance of the disease and the distribution of the number of offspring per family. When considering the average number of affected individuals among first-degree relatives of mutation positive probands, penetrance-related factors accounted for 64% of the variance in the average number of affected first-degree relatives, and 58% of the variance in the number of affected first- or second-degree relatives. In general, the average proportion of mutation-positive probands with at least one affected first-degree relative was low, especially for a sex-limited disease, ranging between 20% and 46%, depending on the lifetime penetrance in mutation carriers. Lack of family history among first-degree relatives of mutation positive probands is not necessarily unexpected even for loci conferring relatively high lifetime risk. In selecting probands for genetic testing, we found that under a wide variety of conditions, criteria based on the number of affected among first- and second-degree relatives were superior to those based on first-degree family history alone.

Familial breast cancer: an investigation into the outcome of treatment for early stage disease

The purpose of this study was to retrospectively compare the outcomes of treatment in 304 women with familial and sporadic breast cancer to clarify the options for the primary management of familial breast cancer. The majority of women were consecutively ascertained on the basis of either breast cancer diagnosed at age < 40 years or bilateral breast cancer. In addition, known BRCA1 mutation carriers were identified through the genetics services in participating centres. These patients were subdivided into those with a significant family history of breast cancer or known BRCA1 mutation (FH+) and those with no significant family history (FH-). There were no significant differences in age, surgical treatment or adjuvant treatment between the two groups, but there were significantly more women whose nodal status was unknown in the FH+ group. Ipsilateral recurrence occurred in 22.2% of FH+ patients compared with 24.1% of FH- patients (p = 0.774) who underwent breast conserving surgery. There was a striking excess of contralateral breast cancers in the FH+ group (35.9% v 16%, p = 0.0007), with a cumulative risk of contralateral cancer of 36% at 10 years. This was reflected in a non-significant trend toward worse relapse free survival in the FH+ group (p = 0.0563), but no difference was observed in overall survival between the two patient groups (p = 0.142). Similarly, for patients with known BRCA1 mutations, contralateral recurrence occurred more frequently, but other outcomes were not significantly different from the FH- group. Breast conserving treatment is not associated with an increased risk of local recurrence in women with familial breast cancer and the prognosis of these women appears to be similar to that of young women with apparently sporadic breast cancer. However, the risk of contralateral breast cancer is significant in the FH+ group and should be considered in planning primary treatment and follow up.

Racial meanings and scientific methods: changing policies for NIH-sponsored publications reporting human variation

Conventional wisdom holds that race is socially constructed and not based on genetic differences. Cutting-edge genetic research threatens this view and hence also endangers the pursuit of racial equality and useful public health research. The most recent incarnation of racial genetics is not due to scientific discoveries about population differences per se, but follows from how the United States and other governments have organized racial categories. This article explains tensions in U.S. government guidelines and publications on the study of human genetic diversity, points out the absence of any compelling public health benefits that might justify this research, introduces conceptual tools for addressing the complicated heuristic and policy problems posed by medical population genetics, and offers two policy proposals to remedy the current problems.

Mutational analysis of BARD1 in familial breast cancer patients in Japan

Since BRCA1,which is a breast cancer susceptibility gene, form heterodimers with BARD1, it is speculated that BARD1 mutations might affect the function of BRCA1, contributing to breast carcinogenesis. Thus, in the present study, we have conducted mutational analysis of BARD1 in familial breast cancer patients (n=60) who were tested negative for both BRCA1 and BRCA2 germline mutations. We have been unable to show any clearly deleterious mutations but identified four missence mutations (Ser/Cys 241, Arg/Ser 378, Asn/Ser 470, Val/Met 507), one silent mutation (His/His 506), and one frameshift (in-frame) mutation (1139del21bp). Of these six mutations, one (Asn/Ser 470) was considered as a putative germline mutation since such a mutation was not observed in any of the healthy controls (n=152) but the other five mutations were considered as common genetic polymorphisms since they were frequently observed in the healthy controls. These genetic polymorphisms were further analyzed in their association with breast cancer risk by a case-control study using the population-based breast cancers (n=143) and healthy controls (n=155), which showed that carriers of the variant allele Met at codon 507 are significantly associated with the increased risk of breast cancer (adjusted odds ratio=2.05, 95% confidential interval=1.01-4.16) in postmenopausal women and that the other genetic polymorphisms are not associated with breast cancer risk. These results suggest that BARD1 mutations are responsible for, if any, a very small number of familial breast cancers. Genetic polymorphism of BARD1 (Val/Met 507) could be useful in the selection of postmenopausal women at a high risk for developing breast cancer.

Familial Breast Cancer: Scope for More Susceptibility Genes?

PURPOSE

The familial risk of female breast cancer is somewhat less than 2.0 when a first-degree relative is diagnosed with breast cancer, but it is not known to what extent heritable or environmental factors explain the familial clustering. Such data would be valuable for prevention and gene identification strategies.

EXPERIMENTAL DESIGN

We used the nation-wide Swedish Family-Cancer Database on 10.2 million individuals and 190,000 mothers' and 26,000 daughters' breast cancers to calculate familial standardised incidence ratios (SIRs), for all invasive breast cancers in daughters, who were 0-66 years old. Over 5500 familial breast cancers were recorded.

RESULTS

The familial SIR for all invasive breast cancer was 1.71 by breast cancer in the mother only, 1.95 by breast cancer in a sister only, and 2.75 by breast cancer in both a mother and sister. The SIRs did not change when adjustments were done for period, age at first birth, parity, socio-economic status and region. Age difference between sisters showed a small variation in risk for breast cancer but the highest SIR was found for those whose age difference was from 6 to 10 years. Half sisters showed an excess of familial risks exactly half of full sisters, the SIR being 1.44.

CONCLUSIONS

These data suggest that familial aggregation of breast cancer is mainly due to heritable causes. Because the known susceptibility genes only explain about a quarter of the familial aggregation, the remaining majority offers a challenge to new genomic approaches.

Prevalence of BRCA1 and BRCA2 germline mutations in young breast cancer patients: a population-based study

Our aim was to estimate the prevalence of mutations in the BRCA1 and BRCA2 genes among unselected incident cases of breast cancer in young women. We identified 158 incident breast cancer cases diagnosed before age 46 years in predefined geographic areas in Girona and Tarragona, Spain, during 1995-1997. Of these, 136 (86%) provided information on family history of cancer and were screened for BRCA1 and BRCA2 mutations. Nine of the 136 (6.6%) were found to carry BRCA deleterious mutations (MUT) (1 BRCA1 and 8 BRCA2), and 20 were detected with rare BRCA variants of unknown significance (UV). Both MUT and US BRCA alterations were more frequent in younger patients: 7 (11.6%) MUT and 12 (19.3%) UV carriers were found in the group of 62 patients younger than 40 years, whereas 2 (2.7%) MUT and 9 (12%) US carriers were identified in the group of 74 patients aged 40-45. Family history of breast and ovarian cancers suggestive of hereditary condition (at least 2 first- or second-degree relatives affected with breast cancer or at least 1 relative affected with ovarian cancer or early-onset breast cancer) was absent for 5 of 9 MUT carriers. This suggests that BRCA screening policies based on family history of cancer would miss a considerable proportion of BRCA mutations. Mutations in the BRCA1 and BRCA2 genes explain at least 10% of breast cancer cases diagnosed before age 40 years. The contribution of these genes to early-onset breast cancer is likely to be even higher given that certain UV cases might be disease-associated.

Different Expressivity of BRCA1 and BRCA2: Analysis of 179 Italian Pedigrees with Identified Mutation

Mutations in BRCA1 and BRCA2 show different expressivity with respect to cancer risk, and allelic heterogeneity may be present in both genes. We collected 179 pedigrees with identified germline mutation (104 BRCA1 and 75 BRCA2), ascertained in six collaborating centers of the Italian Consortium for Hereditary Breast and Ovarian Cancer. Significant heterogeneity was detected for several variables, and a logistic regression model including age of diagnosis in the proband, presence of ovarian cancer in the family, presence of prostate or pancreatic cancer in the family, and presence of male breast cancer in the family proved to be effective in predicting the presence of a mutation in a gene rather than the other. Excess of familial aggregation of both breast and ovarian cancer was observed in both genes. Proportion of ovarian cancer was increased in the 5' portion of BRCA1, and presence of prostate or pancreatic cancer in a family was correlated with presence of ovarian cancer in BRCA2.

Roles of BRCA1 and BRCA2 in homologous recombination, DNA replication fidelity and the cellular response to ionizing radiation

Inheritance of one defective copy of either of the two breast cancer susceptibility genes, BRCA1 and BRCA2, predisposes individuals to breast and ovarian cancers. Current progress in determining the function of these genes suggests that they participate in a common pathway to facilitate orderly homologous recombination and thereby maintain genomic integrity. As a consequence of this defect in homologous recombination, tumors that arise in BRCA carriers are likely to be more sensitive to ionizing radiation. This review summarizes recent investigations about the nature of the defect in DNA repair, and highlights the unanswered questions about the tumor suppressor paradox of BRCA genes. The unsolved mystery is the other genetic changes that must occur to turn a BRCA-deficient cell from a nonviable cell into a tumor cell capable of endless growth.

Log odds of carrying an Ancestral Mutation in BRCA1 or BRCA2 for a Defined personal and family history in an Ashkenazi Jewish woman (LAMBDA)

Introduction

Ancestral mutations in BRCA1 and BRCA2 are common in people of Ashkenazi Jewish descent and are associated with a substantially increased risk of breast and ovarian cancer. Women considering mutation testing usually have several personal and family cancer characteristics, so predicting mutation status from one factor alone could be misleading. The aim of this study was to develop a simple algorithm to estimate the probability that an Ashkenazi Jewish woman carries an ancestral mutation, based on multiple predictive factors.

Methods

We studied Ashkenazi Jewish women with a personal or family history of breast or ovarian cancer and living in Melbourne or Sydney, Australia, or with a previous diagnosis of breast or ovarian cancer and living in the UK. DNA samples were tested for the germline mutations 185delAG and 5382insC in BRCA1, and 6174delT in BRCA2. Logistic regression was used to identify, and to estimate the predictive strength of, major determinants.

Results

A mutation was detected in 64 of 424 women. An algorithm was developed by combining our findings with those from similar analyses of a large study of unaffected Jewish women in Washington. Starting with a baseline score, a multiple of 0.5 (based on the logistic regression estimates) is added for each predictive feature. The sum is the estimated log odds ratio that a woman is a carrier, and is converted to a probability by using a table. There was good internal consistency.

Conclusions

This simple algorithm might be useful in the clinical and genetic counselling setting. Comparison and validation in other settings should be sought.

BRCA1 gene in breast cancer

The BRCA1 gene was identified and cloned in 1994 based its linkage to early onset breast cancer and breast-ovarian cancer syndromes in women. While inherited mutations of BRCA1 are responsible for about 40-45% of hereditary breast cancers, these mutations account for only 2-3% of all breast cancers, since the BRCA1 gene is rarely mutated in sporadic breast cancers. However, BRCA1 expression is frequently reduced or absent in sporadic cancers, suggesting a much wider role in mammary carcinogenesis. Since BRCA1 was cloned in 1994, its molecular function has been the subject of intense investigation. These studies have revealed multiple functions of the BRCA1 that may contribute to its tumor suppressor activity, including roles in: cell cycle progression, several highly specialized DNA repair processes, DNA damage-responsive cell cycle check-points, regulation of a set of specific transcriptional pathways, and apoptosis. Many of these functions are linked to protein:protein interactions involving different portions of the 1,863 amino acid (aa) BRCA1 protein. BRCA1 functions in cell cycle progression and the DNA damage response appear to be regulated by distinct and specific phosphorylation events, but the molecular pathways activated by these phosphorylations are only beginning to be unraveled. In addition, the reason that BRCA1 mutation carriers develop specific tumor types (breast and ovarian cancers in women and possibly prostate cancers in men) is not clearly understood. Elucidation of the precise molecular functions of the BRCA1 gene product will greatly enhance our understanding of the pathogenesis of hereditary as well as sporadic mammary carcinogenesis.

Allelic loss in breast cancer

Breast cancer is the most prevalent cancer type in women and allelic loss constitutes one of the commonest genetic alterations in mammary neoplasias. Frequent detection of Loss of Heterozygosity indicates genes with putative tumour suppressor activity in breast carcinomas. Imbalance between two alleles might also be related with increased expression of an oncogene within a locus. Loci exhibiting frequent allelic loss in breast cancer have been detected, spread throughout the genome, and may contain genes with potential significance in breast carcinogenesis. Loss of Heterozygosity patterns in breast cancer give evidence for multiple clonality of the disease, and that accumulation of such lesions is probably implicated in disease development. Studies on deletions of known breast cancer genes suggest interactions with other common genetic events during disease initiation and progression. Allelic loss has been repeatedly associated with adverse characteristics and poor outcome in breast neoplasms. Detection of allelic loss in the serum of breast cancer patients and in premalignant breast lesions could herald the potential for diagnosis of the disease at an early, and thus curable, stage.

Markers of genetic susceptibility in human environmental hygiene and toxicology: the role of selected CYP, NAT and GST genes

Inherited genetic traits co-determine the susceptibility of an individual to a toxic chemical. Special emphasis has been put on individual responses to environmental and industrial carcinogens, but other chronic diseases are of increasing interest. Polymorphisms of relevant xenobiotic metabolising enzymes may be used as toxicological susceptibility markers. A growing number of genes encoding enzymes involved in biotransformation of toxicants and in cellular defence against toxicant-induced damage to the cells has been identified and cloned, leading to increased knowledge of allelic variants of genes and genetic defects that may result in a differential susceptibility toward environmental toxicants. "Low penetrating" polymorphisms in metabolism genes tend to be much more common in the population than allelic variants of "high penetrating" cancer genes, and are therefore of considerable importance from a public health point of view. Positive associations between cancer and CYP1A1 alleles, in particular the *2C I462V allele, were found for tissues following the aerodigestive tract. Again, in most cases, the effect of the variant CYP1A1 allele becomes apparent or clearer in connection with the GSTM1 null allele. The CYP1B1 codon 432 polymorphism (CYP1B1*3) has been identified as a susceptibility factor in smoking-related head-and-neck squameous cell cancer. The impact of this polymorphic variant of CYP1B1 on cancer risk was also reflected by an association with the frequency of somatic mutations of the p53 gene. Combined genotype analysis of CYP1B1 and the glutathione transferases GSTM1 or GSTT1 has also pointed to interactive effects. Of particular interest for the industrial and environmental field is the isozyme CYP2E1. Several genotypes of this isozyme have been characterised which seem to be associated with different levels of expression of enzyme activity. The acetylator status for NAT2 can be determined by genotyping or by phenotyping. In the pathogenesis of human bladder cancer due to occupational exposure to "classical" aromatic amines (benzidine, 4-aminodiphenyl, 1-naphthylamine) acetylation by NAT2 is regarded as a detoxication step. Interestingly, the underlying European findings of a higher susceptibility of slow acetylators towards aromatic amines are in contrast to findings in Chinese workers occupationally exposed to aromatic amines which points to different mechanisms of susceptibility between European and Chinese populations. Regarding human bladder cancer, the hypothesis has been put forward that genetic polymorphism of GSTM1 might be linked with the occurrence of this tumour type. This supports the hypothesis that exposure to PAH might causally be involved in urothelial cancers. The human polymorphic GST catalysing conjugation of halomethanes, dihalomethanes, ethylene oxide and a number of other industrial compounds could be characterised as a class theta enzyme (GSTT1) by means of molecular biology. "Conjugator" and "non-conjugator" phenotypes are coincident with the presence and absence of the GSTT1 gene. There are wide variations in the frequencies of GSTT1 deletion (GSTT1*0/0) among different ethnicities. Human phenotyping is facilitated by the GST activity towards methyl bromide or ethylene oxide in erythrocytes which is representative of the metabolic GSTT1 competence of the entire organism. Inter-individual variations in xenobiotic metabolism capacities may be due to polymorphisms of the genes coding for the enzymes themselves or of the genes coding for the receptors or transcription factors which regulate the expression of the enzymes. Also, polymorphisms in several regions of genes may cause altered ligand affinity, transactivation activity or expression levels of the receptor subsequently influencing the expression of the downstream target genes. Studies of individual susceptibility to toxicants and gene-environment interaction are now emerging as an important component of molecular epidemiology.

Similar contributions of BRCA1 and BRCA2 germline mutations to early-onset breast cancer in Germany

This study was undertaken to investigate the prevalence of BRCA1 and BRCA2 germline mutations in 91 German patients unselected for family history, who were diagnosed with breast cancer before the age of 41 years. Clinical information and blood samples were obtained from all patients. A comprehensive BRCA1 and BRCA2 mutational analysis was performed using the protein truncation assay and single-strand conformational polymorphism analysis followed by DNA sequencing of variant signals detected by these assays. Five different deleterious germline mutations including four frameshift mutations and one missense mutation were identified, three in BRCA1 (3.3%) and two mutations (2.2%) in BRCA2. Both BRCA2 mutations are novel and might be specific for the German population. An additional BRCA1 missense mutation previously described and classified as an unknown variant was found. This mutation was also detected in two breast cancer patients of family P 328 and not in 140 healthy controls suggesting that it is disease associated. In addition, one common polymorphism and five novel intronic sequence variants with unknown significance were found. Our findings show that mutations in BRCA1 and BRCA2 may contribute similarly to early-onset breast cancer in Germany. Given current constraints on health-care resources, these results support the notion that BRCA1 and BRCA2 mutation screening may have the strongest impact on health-care when targeted to high-risk populations.

Subsequent primary malignancies after endometrial carcinoma and ovarian carcinoma

BACKGROUND

Population-based data on subsequent neoplasms after women are diagnosed with endometrial and ovarian carcinomas are limited, particularly regarding specific histologic tumor types.

METHODS

The nationwide Swedish Family-Cancer Database of 10.2 million individuals, which includes 19,128 invasive endometrial carcinomas and 19,440 ovarian carcinomas, was used to calculate standardized incidence ratios (SIRs) and 95% confidence intervals (95% CIs) for second primary carcinomas. SIRs were calculated for specific follow-up periods. Data on histopathologic types also were used.

RESULTS

An excess of subsequent malignancies after women were diagnosed with endometrial carcinoma was noted at 11 sites. The highest SIRs were recorded for synchronous or metasynchronous ovarian carcinomas (SIR, 55.77; 95% CI, 48.82-63.43) and carcinomas of the small intestines (SIR, 14.71; 95% CI, 4.64-34.59). Primary ovarian carcinoma was followed by an increased risk of developing endometrial carcinoma, and the risks of developing many other malignancies also were increased after women were diagnosed with endometrial carcinoma, including intestinal malignancies, renal cell carcinoma, bladder carcinoma, squamous cell skin carcinoma, connective tissue malignancies, and leukemia. When ovarian endometrioid histology was diagnosed synchronously with primary endometrial carcinoma, the SIR was 140; when endometrial carcinoma was the subsequent neoplasm, the SIR was 87. A small familial component was found in the cooccurrence of endometrial carcinoma and ovarian carcinoma.

CONCLUSIONS

The current data show a strong clustering of endometrial carcinomas and ovarian carcinomas, particularly involving tumors of endometrioid morphology. The patterns of second neoplasms also suggest that hereditary nonpolyposis colorectal carcinoma may contribute to the association between endometrial and ovarian malignancies. Increased risks for connective tissue tumors and leukemia may signal a response to treatment, and an increased risk for squamous cell skin carcinoma may signal a depressed immune function.

Use of genetic testing and prophylactic mastectomy and oophorectomy in women with breast or ovarian cancer from families with a BRCA1 or BRCA2 mutation

PURPOSE

To analyze the use of genetic testing, prophylactic mastectomy, and oophorectomy among women with breast and/or ovarian cancer from families with a BRCA1 or BRCA2 mutation.

PATIENTS AND METHODS

We examined prospectively the use of BRCA1/BRCA2 testing in all women with a primary breast or ovarian cancer from a consecutive series of 112 high-risk families in which a BRCA1/BRCA2 mutation eventually was identified. The rate of prophylactic bilateral and contralateral mastectomy and prophylactic oophorectomy was analyzed in the women who carried a BRCA1/BRCA2 mutation and who had no metastatic disease at the time of the genetic test disclosure. We examined predictors for genetic test uptake and prophylactic surgery using univariate and multivariate analysis.

RESULTS

Overall, 192 of 220 women (87%) with primary tumors underwent genetic testing. Eleven of these 192 tested women (6%) appeared not to carry the family-specific BRCA1/BRCA2 mutation. Genetic testing occurred significantly more frequently at ages younger than 50 years (P =.04) and in persons with multiple primary tumors (P =.02). Among eligible women, 35 of 101 (35%) requested bilateral or contralateral mastectomy, and 47 of 95 (49%) requested oophorectomy. Women aged younger than 50 years and women who developed their first tumor after the initial identification of a BRCA1/BRCA2 mutation in the family were significantly (both P =.01) more likely to opt for prophylactic bilateral or contralateral mastectomy.

CONCLUSION

In a clinical setting, we show a high demand for BRCA1/BRCA2 testing and for prophylactic surgery by women with breast and/or ovarian cancer from high-risk families.

Average risks of breast and ovarian cancer associated with BRCA1 or BRCA2 mutations detected in case Series unselected for family history: a combined analysis of 22 studies

Germline mutations in BRCA1 and BRCA2 confer high risks of breast and ovarian cancer, but the average magnitude of these risks is uncertain and may depend on the context. Estimates based on multiple-case families may be enriched for mutations of higher risk and/or other familial risk factors, whereas risk estimates from studies based on cases unselected for family history have been imprecise. We pooled pedigree data from 22 studies involving 8,139 index case patients unselected for family history with female (86%) or male (2%) breast cancer or epithelial ovarian cancer (12%), 500 of whom had been found to carry a germline mutation in BRCA1 or BRCA2. Breast and ovarian cancer incidence rates for mutation carriers were estimated using a modified segregation analysis, based on the occurrence of these cancers in the relatives of mutation-carrying index case patients. The average cumulative risks in BRCA1-mutation carriers by age 70 years were 65% (95% confidence interval 44%-78%) for breast cancer and 39% (18%-54%) for ovarian cancer. The corresponding estimates for BRCA2 were 45% (31%-56%) and 11% (2.4%-19%). Relative risks of breast cancer declined significantly with age for BRCA1-mutation carriers (P trend.0012) but not for BRCA2-mutation carriers. Risks in carriers were higher when based on index breast cancer cases diagnosed at <35 years of age. We found some evidence for a reduction in risk in women from earlier birth cohorts and for variation in risk by mutation position for both genes. The pattern of cancer risks was similar to those found in multiple-case families, but their absolute magnitudes were lower, particularly for BRCA2. The variation in risk by age at diagnosis of index case is consistent with the effects of other genes modifying cancer risk in carriers.