The risk of cancer associated with specific mutations of BRCA1 and BRCA2 among Ashkenazi Jews

Medical implications of understanding complex disease traits

The application of genetic mapping to human disease gene identification has led to the definition of many linkages and a few disease genes in complex traits over the past two years. Its application has also increased to include aspects of pharmacogenetics relating to pharmacokinetics and pharmacodynamics.

Low incidence of BRCA1 mutations among Italian families with breast and ovarian cancer

Most familial breast or ovarian cancers are thought to be due to highly penetrant mutations in the predisposing genes BRCA1 and BRCA2. The cloning of these genes has opened a new era for the genetic counseling of women with a family history of breast or ovarian cancer. To estimate the incidence of detectable BRCA1 mutations and to define the eligibility criteria for genetic testing in the Italian population, a total of 53 patients belonging to 46 families clustering multiple cases of breast and/or ovarian cancer were investigated. Seven families presented with ovarian cancer only, 16 had both ovarian and breast cancers, and 23 were characterized by breast cancer only. Using a combination of protein truncation test (PTT) and single strand conformational polymorphism (SSCP) analysis followed, when necessary, by direct sequencing, we found 8 distinct mutations, 2 of these not reported before. Five frameshift and 2 nonsense mutations led to a truncated protein. One mutation was a missense substitution involving a cysteine in the zinc finger domain. One variant creating an ETS binding site in intron I was found but its role was not defined. The percentage of families carrying mutations was 17%. Among the families characterized by ovarian cancer only and by breast and ovarian cancer, the percentage of BRCA1 mutations was 57% and 12.5%, respectively. In contrast, the percentage of altered BRCA1 in families with only breast cancers was 9%. In the 46 Italian families studied, BRCA1 mutations were detected in fewer kindreds than those previously hypothesized based on linkage analysis, especially when these were characterized by breast cancers only. Our results indicate that families with a low number of cancer patients should be referred for BRCA1 genetic testing mainly when ovarian cancer is present.

Current policies for surveillance and management in women at risk of breast and ovarian cancer: a survey among 16 European family cancer clinics. European Familial Breast Cancer Collaborative Group

The recent isolation of breast cancer predisposing genes (BRCA1 and BRCA2) allows the identification of carriers within affected families. These carriers have a 50-85% risk of developing breast or ovarian cancer and need careful follow-up. The purpose of this study was to evaluate the management and screening protocols implemented in high risk families at various family cancer clinics in Europe. A questionnaire was mailed to the members of the European Familial Breast Cancer Collaborative Group (n = 30) requesting information on the following issues: indication for surveillance of breasts and ovaries, the recommended protocol, coordination of the screening examination, prophylactic surgery, the specific management of breast cancer in a mutation carrier and the use of oestrogen. 16 centres from nine countries responded. Most centres recommend surveillance of the breasts if the lifetime risk exceeds 15-20%. The surveillance protocol that is generally advised comprises monthly self breast examination, examination by a specialist every 6 months and annual mammography, all starting from an age between 25 and 35 years. Surveillance of the ovaries is recommended in BRCA1 and BRCA2-mutation carriers, in members from breast/ovarian cancer families and in some centres in 'breast cancer only' families with an early onset of breast cancer. The recommended protocol includes gynaecological examination, sonography and estimation of CA-125 at yearly intervals starting from the age 30-35 years. Prophylactic mastectomy is considered for proven mutation carriers in some centres. Most centres consider prophylactic oophorectomy in mutation carriers and some centres also consider it for members of breast/ovarian cancer families. This survey provides insight into the guidelines for surveillance and management of familial breast cancer used at various family cancer clinics in Europe; this insight may contribute to the appropriate management of these high risk women. It should be emphasised that most recommendations are based on experts' opinion rather than on any specific studies.

Population-based study of risk of breast cancer in carriers of BRCA2 mutation

BACKGROUND

Estimates of an 80-90% risk of breast cancer for carriers of germline mutations in the BRCA1 and BRCA2 genes are based on studies of families at high risk of breast cancer. Risk estimates for a population are possible if the mutation status of a representative sample of that population can be assessed. In Iceland, one common founder BRCA2 mutation occurs in 0.6% of the population. Iceland has a population-based cancer registry and a large collection of pedigrees, and estimation of cancer risk in mutation carriers is therefore possible.

METHODS

We studied 575 breast-cancer patients, 541 women and 34 men unselected for family history of breast cancer. Data on cancer in first-degree relatives were available from the cancer registry. Risk of cancer was estimated by comparing the history of cancer in first-degree relatives of carriers and non-carriers.

FINDINGS

56 (10.4%) of the 541 women and 13 (38%) of the 34 men carried the 999del5 mutation. The estimated risk of breast cancer at age 50 for all female carriers of the 999del5 mutation was 17.0% (95% CI 9.1-25.9) and 37.2% (22.4-53.9) at age 70.

INTERPRETATION

The results of our population-based study show that the mean risk of breast cancer in carriers of mutation in BRCA2 is lower than previously suggested. Individual risk assessment will, however, have to take account of family history.

Testing for the BRCA1 and BRCA2 breast-ovarian cancer susceptibility genes: a decision analysis

OBJECTIVE

The authors developed a Markov decision model to evaluate the health implications of testing for mutations in the BRCA1 and BRCA2 breast-ovarian cancer susceptibility genes. Prophylactic measures considered included various combinations of immediate and delayed bilateral mastectomy and oophorectomy or taking no action.

METHODS

The model incorporated the likelihood of developing breast and/or ovarian cancer, survival, and quality of life. Parameter values were taken from public databases, the published literature, and a survey of cancer experts. Outcomes considered were additional life expectancy and quality-adjusted life years (QALYs). Results are reported for 30-year-old cancer-free women at various levels of hereditary risk.

RESULTS AND CONCLUSIONS

The vast majority of women will not benefit from testing because their pre-test risks are low and surgical prophylaxis is undesirable. However, women who have family histories of early breast and/or ovarian cancer may gain up to 2 QALYs by allowing genetic testing to inform their decisions.

Screening and clinical implications for BRCA1 and BRCA2 mutation carriers

In this article, we review the history of testing for mutations in breast cancer susceptibility genes and discuss the current state of testing for mutations in BRCA1 and BRCA2 in different clinical settings including at-risk individuals and cancer patients. The risk of breast cancer. other associated malignancies and prognosis in carriers of these mutations are reviewed. A final section includes discussion of current recommendations for surveillance and the need for further research to identify environmental and genetic factors which modify the risk of developing cancer in mutation carriers.

Patient regrets after bilateral prophylactic mastectomy

BACKGROUND

The discovery of a cadre of breast cancer susceptibility genes has resulted in an increase in the number of women seeking information about prophylactic breast surgery, but virtually no large-scale prospective databases exist to assist women considering prophylactic mastectomy.

METHODS

The authors constructed a National Prophylactic Mastectomy Registry comprised of a volunteer population of 817 women from 43 states who have undergone prophylactic mastectomy.

RESULTS

In the registry, 370 women had undergone bilateral prophylactic mastectomy. Twenty-one (5%) women expressed regrets about the procedure. The median follow-up was 14.6 years (mean 14.8 years; range 0.2-51 years). Those with regrets were subsetted into those with major (n = 10) or minor (n = 7) regrets. Regrets were more common in those women with whom discussion about prophylactic mastectomy was initiated by a physician (19/255), compared with patients who initiated the discussion themselves (2/108; P < .05).

CONCLUSIONS

The overall satisfaction rate of 95% reported here may be explained by the voluntary nature of this registry. The most important factor that predicts an unfavorable outcome following bilateral prophylactic mastectomy is a physician-initiated discussion.

The genetics of inherited breast cancer

The isolation of BRCA1 and BRCA2 has greatly increased our understanding of the genetics of inherited breast and ovarian cancer although the functions of these genes are not yet fully understood. We will discuss the current state of knowledge about the function of BRCA1 and BRCA2 and summarize the cancer risks in women carrying a BRCA1 or BRCA2 mutation. We review the evidence for gene-gene and gene-environment interaction in modifying that risk, and discuss the contribution of BRCA1 and BRCA2 and other high penetrance genes to both inherited and sporadic breast cancer.

Overestimation of hereditary breast cancer risk

OBJECTIVE

To find out how women with breast or ovarian cancer rate their chances of carrying hereditary factors for these cancers and to determine the extent to which they overestimate their risk.

SUMMARY BACKGROUND DATA

BRCA1 and BRCA2 are genes that cause breast and ovarian cancer when they are inherited in families. Testing for disease-associated mutations in these genes is now available commercially. Previous studies have shown that women overestimate their chances of carrying mutations. However, women's perceptions of risk have not been compared to objective estimates or to actual BRCA1 and BRCA2 testing results.

METHODS

This study examines estimates of carrying BRCA1 and BRCA2 mutations among women participating in a randomized trial comparing alternative precounseling educational materials. Estimates were provided by participants in a baseline mailed survey. Estimates given by participants were compared to those given by an expert panel and by a statistical model. Testing was offered free of charge and was done in an academic laboratory using standard techniques. Baseline estimates of participating women were compared to the estimates of the expert panel, to the carrier probability provided by the statistical model, and to actual testing results.

RESULTS

Women who have a personal history of breast or ovarian cancer significantly overestimate their risk of carrying hereditary factors for breast and ovarian cancer. Self-estimates exceeded the estimates of experts and a statistical model. One hundred women completed testing, and 21 mutations in BRCA1 or BRCA2 were found. Many test-negative women also overestimated their hereditary risk. Some women with a high carrier probability were negative for BRCA1 and BRCA2 mutations.

CONCLUSIONS

Overestimation of hereditary factors is common among affected women with a family history of cancer. Pretest education and counseling should reduce these high-risk perceptions. Better estimates of carrier probability will direct more intensive clinical services and research.

Absence of 185delAG mutation of the BRCA1 gene and 6174delT mutation of the BRCA2 gene in Ashkenazi Jewish men with prostate cancer

Epidemiological studies have demonstrated a clustering of breast and prostate cancers in some families. Moreover, there is an increase in the number of cases of prostate cancer in families with inherited mutations of the breast cancer susceptibility gene BRCA1. We assessed the role of BRCA1 and BRCA2 in prostate cancer. We tested for the BRCA1 185delAG frameshift mutation, found in 0.9% of Ashkenazi Jews, and the BRCA2 6174delT mutation, found in 1% of Ashkenazi Jews, in Ashkenazi Jewish men with prostate cancer. We studied 60 Ashkenazi men with prostate cancer. A family history was obtained by interview or a self-report questionnaire. Histological confirmation of diagnosis was obtained for all subjects. Ethnic background was confirmed for all subjects by self-report or interview. Mutations of BRCA1 and BRCA2 were detected by amplification of lymphocyte DNA from peripheral blood according to standard polymerase chain reaction (PCR) and dot blot procedures. Patients' ages ranged from 55 to 80 years (mean +/- s.d. 70 +/- 5.25). There were six men with a family history of prostate cancer; three of these had a father with prostate cancer. Five of the men had a family history of breast cancer, in a mother, a sister or an aunt. None of the men had a family history of both breast and prostate cancer. None of the 60 men carried the 185delAG BRCA1 or 6174delT BRCA2 mutations. Of 268 Ashkenazi Jewish women with sporadic breast cancer, tested in an unrelated study, 16 carried either the 185delAG mutation of BRCA1 or the 6174delT mutation of BRCA2. There was a significant difference in the incidence of the BRCA1 and BRCA2 mutations in the breast and prostate cancer cases (P = 0.05, two-tailed Fisher's exact test). The contribution of germline BRCA1 and BRCA2 mutations to prostate cancer incidence is probably small and could be limited to specific subgroups.

Ethics of predictive DNA-testing for hereditary breast and ovarian cancer

The recent identification of gene mutations involved in hereditary cancers increasingly allows for predictive DNA-testing. There is an urgent need to analyse the ethical issues involved. This article concentrates on the ethics of predictive testing for mutations in the breast (and ovarian) cancer genes BRCA1 and -2. Using international guidelines for presymptomatic DNA-testing for Huntington disease and the Li-Fraumeni syndrome as a model, a provisional protocol, which entails four parts is presented: (i) inclusion and exclusion criteria; (ii) preparing for the test; (iii) informing about the results of the test; (iv) post-test counselling and evaluation. The importance of an integral education of both doctors and the public is stressed.

Recommendations for medical management of hereditary breast and ovarian cancer: the French National Ad Hoc Committee

BACKGROUND AND PURPOSE

Almost 10% of breast and ovarian cancers are familial, and the majority are linked to BRCA1 and BRCA2 germline mutations. Despite uncertainty about the management of female gene carriers, consensus guidelines have been established to assist practitioners and consultees in making health care decisions.

METHODOLOGY

The Ad Hoc Committee was composed of 14 experts appointed by the French National Institute for Health and Medical Research, all of whom attended eleven workshops at which more than 3500 articles were systematically analyzed. Five additional experts critically analysed the first version of the report. CRITERIA AND DECISION PROCESS: On a probability scale of the risk of developing breast or ovarian cancers, two thresholds were defined for use in determining whether an intervention would be worthwhile. The first is the threshold above which an intervention can be envisaged or recommended, and the second is the one below which an intervention can be ruled out; between the two, the decision has to be made on a case-by-case basis. SCREENING AND PREVENTIVE STRATEGIES ANALYZED: With respect to breast cancer: 1) hormonal interventions; 2) primary prevention (diet, family planning and chemoprevention); 3) screening (breast self-examination, clinician breast examination, tumor markers, imaging); 4) prophylactic mastectomy. With respect to ovarian cancer: 1) hormonal stimulation; 2) screening (clinical screening, ultrasound and tumor markers); 3) prophylactic oophorectomy.

MAIN CONCLUSIONS

For each strategy the following points were addressed: the information to be given to the consultee, the procedure and the indications. In addition, the committee's opinion about BRCA1 and BRCA2 mutation screening is that population-based, or even large-scale, implementation are not justified. Although no scientific evidence is available, the committee feels that specific management is indispensable and advocates the use of defined and evaluated procedures, and participation in clinical trials.

A family with three germline mutations in BRCA1 and BRCA2

Several cancer genetics centres offer testing for specific BRCA1 and BRCA2 mutations to Ashkenazi Jewish individuals with a family history of breast and ovarian cancers. Testing involves screening for three common mutations found in this population, namely BRCA1 185delAG, 5382insC and BRCA2 6174delT (Struewing et al., Nat Genet 1995: 11: 198-200; Roa et al., Nat Genet 1996: 14: 185-187; Oddoux et al., Nat Genet 1996: 14: 188-190). We have identified a large Ashkenazi Jewish kindred (W9170) with ten cases of breast cancer and four cases of ovarian carcinoma. Initially, mutation analysis for this family identified a BRCA1 185delAG mutation in the proband diagnosed with three separate primary cancers of the breast, ovary and colon. Another individual in this family diagnosed with two primary cancers of the ovary and breast, was identified as having a second mutation, BRCA1 5382insC. Subsequent work found that two sisters (cousins of the proband), both diagnosed with carcinoma of the breast, had a third mutation, BRCA2 6174delT. These three mutations have previously been found to be more common in the Ashkenazi Jewish population (References as above). The identification of all three mutations in one family, raised new implications for the manner in which testing and counselling should be offered. In our opinion, Ashkenazi Jewish individuals in breast-ovarian cancer families should be offered complete testing for the three common Ashkenazi Jewish mutations regardless of previous identification of one of these mutations in the family.

The APCI1307K allele and cancer risk in a community-based study of Ashkenazi Jews

Mutations in APC are classically associated with familial adenomatous polyposis (FAP), a highly penetrant autosomal dominant disorder characterized by multiple intestinal polyps and, without surgical intervention, the development of colorectal cancer (CRC). APC is a tumour-suppressor gene, and somatic loss occurs in tumours. The germline T-to-A transversion responsible for the APC I1307K allele converts the wild-type sequence to a homopolymer tract (A8) that is genetically unstable and prone to somatic mutation. The I1307K allele was found in 6.1% of unselected Ashkenazi Jews and higher proportions of Ashkenazim with family or personal histories of CRC (ref. 2). To evaluate the role of I1307K in cancer, we genotyped 5,081 Ashkenazi volunteers in a community survey. Risk of developing colorectal, breast and other cancers were compared between genotyped I1307K carriers and non-carriers and their first-degree relatives.

Down-regulation of BRCA1 and BRCA2 in human ovarian cancer cells exposed to adriamycin and ultraviolet radiation

Germ-line mutations of the BRCA1 and BRCA2 genes predispose women to develop cancers of the breast and ovary, but the biologic functions of these genes remains unclear. We have investigated the responses of the BRCA1 and BRCA2 gene products to cytotoxic agents in 3 human ovarian cancer cell lines: SK-OV-3 (which contains a p53 deletion mutation), CAOV-3 (which over-expresses a mutant p53) and PA-1 (which expresses wild-type p53). In screening studies, we determined the effects of 7 different agents on BRCA1 and BRCA2 expression. We found that Adriamycin (ADR) and ultraviolet (UV)radiation significantly down-regulated BRCA1 and BRCA2 mRNA expression in SK-OV-3 cells. On the other hand, camptothecin, nitrogen mustard, taxol, vincristine and etoposide had no effect on BRCA1 or BRCA2 mRNA levels at doses that yielded degrees of cytotoxicity similar to or greater than ADR. The down-regulation of BRCA1 and BRCA2 mRNAs was dose and time dependent; significant down-regulation was first observed at 8-16 hr after exposure to ADR. BRCA1 protein levels were also down-regulated following treatment of SK-OV-3 cells with ADR. Similar results were observed in CAOV-3 and PA-1 cells treated with ADR, and this finding could not be directly attributed to ADR-induced changes in the cell cycle distribution. The ADR doses required for significant decreases of BRCA1 and BRCA2 were about 10-15, 5-10 and 2 microM, respectively, for SK-OV-3, CAOV-3 and PA-1; the IC50 doses for loss of cell viability (determined by Trypan blue dye exclusion) were 23, 14 and 0.4 microM, respectively. Thus, at equitoxic doses of ADR, PA-1 cells were more resistant to down-regulation of BRCA1 and BRCA2 than SK-OV-3 or CAOV-3. Our findings suggest that 1) BRCA1 and BRCA2 expression in human ovarian cancer cell lines is selectively down-regulated by 2 DNA-damaging agents (ADR and UV radiation); 2) these responses are not due to non-specific cytotoxicity; and 3) the BRCA1 and BRCA2 responses may be dependent, in part, on the p53 functional status of the cells. We speculate that the down-regulation of BRCA1 and BRCA2 may be part of a cellular survival response activated by certain forms of DNA damage.

Frequency and carrier risk associated with common BRCA1 and BRCA2 mutations in Ashkenazi Jewish breast cancer patients

Based on breast cancer families with multiple and/or early-onset cases, estimates of the lifetime risk of breast cancer in carriers of BRCA1 or BRCA2 mutations may be as high as 85%. The risk for individuals not selected for family history or other risk factors is uncertain. We determined the frequency of the common BRCA1 (185delAG and 5382insC) and BRCA2 (6174delT) mutations in a series of 268 anonymous Ashkenazi Jewish women with breast cancer, regardless of family history or age at onset. DNA was analyzed for the three mutations by allele-specific oligonucleotide hybridization. Eight patients (3.0%, 95% confidence interval [CI] 1.5%-5.8%) were heterozygous for the 185delAG mutation, two (0.75%, 95% CI 0.20-2.7) for the 5382insC mutation, and eight (3.0%, 95% CI 1.5-5.8) for the 6174delT mutation. The lifetime risk for breast cancer in Ashkenazi Jewish carriers of the BRCA1 185delAG or BRCA2 6174delT mutations was calculated to be 36%, approximately three times the overall risk for the general population (relative risk 2.9, 95% CI 1.5-5.8). For the 5382insC mutation, because of the low number of carriers found, further studies are necessary. The results differ markedly from previous estimates based on high-risk breast cancer families and are consistent with lower estimates derived from a recent population-based study in the Baltimore area. Thus, presymptomatic screening and counseling for these common mutations in Ashkenazi Jewish women not selected for family history of breast cancer should be reconsidered until the risk associated with these mutations is firmly established, especially since early diagnostic and preventive-treatment modalities are limited.

Optimization of PCR and electrophoresis conditions enhances mutation analysis of the BRCA1 gene

Single-strand confirmation polymorphism (SSCP) analysis on MDE gels has been extensively used to detect BRCA1 gene mutations. In screening a large cohort of ovarian cancer patients, our group was not completely satisfied with the standard published techniques. Although conventional primer sets usually amplified well, we were able to enhance band spread and resolution by varying the PCR and electrophoresis conditions for many of the individual exons. These alterations enhanced our ability to detect polymorphisms and mutations. When utilizing SSCP screening of a gene as large as BRCA1, no one set of conditions or even method may be optimal for all of the exons. Rather, a variety of different methods and conditions should be studied for each set of amplimers under analysis.

Assessment of the time-tradeoff values for prophylactic mastectomy of women with a suspected genetic predisposition to breast cancer

BACKGROUND

Female carriers of the breast-cancer-susceptibility genes BRCA1 and BRCA2 are at high risk for breast cancer (85%). They face the choice between prophylactic mastectomy (PM) and breast cancer screening. For this treatment choice, a shared-decision-making program was developed. In this program, the time tradeoff (TTO) was used to assess preferences for PM.

PURPOSE

Assessment of the feasibility, constant proportional tradeoff, and reliability of using the TTO for this purpose.

METHODS

Fifty-four women suspected to carry the BRCA1/2 mutation were provided with comprehensive relevant information. Their preferences for PM were assessed on two occasions. Discrepancies between preferences indicated by the two tests were resolved by testing a third time. The preferences assessed on the last occasion were used for individual decision analyses. In order to test constant proportional tradeoff, the TTO consisted of four items with different numbers of life years.

RESULTS

Forty-two women (78%) completed the TTO twice and nine women (17%) performed the test a third time. Three women (5%) completed the TTO only once. The mean TTO value for PM at the last replication was 0.69 (SD=0.30). Violations of constant proportional tradeoff were significant: the largest tradeoffs were recorded for the shortest durations. Pearson's correlation coefficient between the TTO values for the two last sessions was 0.96.

CONCLUSION

Assessment of individual preferences by the TTO in this patient group is feasible and reliable. Therefore, the TTO can be used in clinical settings to elicit treatment preferences of women proven or suspected to have a genetic predisposition to breast cancer.

The genetics of hereditary common cancers

Subsets of patients with common cancers belong to families in which the predisposition is inherited in a regular Mendelian fashion. Genes underlying these cancers are now recognized in colorectal cancer (APC, mismatch repair genes, LKB1) and in breast cancer (BRCA1, BRCA2) whereas, in prostate cancer, a locus in chromosome 1 (HPC1) has been proposed on the basis of linkage analysis. Major challenges are to determine the population incidence of these mutations, their penetrance, phenotypic expression, and the effects of modifier genes and epigenetic factors. Finally, the role of encoded proteins in carcinogenesis is a matter of major interest.

A new BRCA1 mutation in a Filipino woman with a family history of breast and ovarian cancer

Mutation of the BRCA1 gene in well-defined breast cancer families has been associated with an 87% lifetime risk for breast cancer and a 44% risk for ovarian cancer. Recent data indicate that the risk associated with these mutations is considerably lower, although still far greater than the risk for disease in the rest of the population. Approximately 81% of the mutations that have been identified have been frameshift (71%) or nonsense (10%) mutations, and either may result in a truncated protein. The protein truncation test (PTT) is often used to screen patients at high risk, because sequencing of this large (100 kb) gene with its 22 coding exons is an arduous task. The PTT was used to analyze genomic DNA and RNA from the peripheral blood of a 31-year-old Filipino woman with a poorly differentiated, stage 2A breast carcinoma and a family history of breast-ovarian cancer. PTT identified the wild-type protein fragment and an additional truncated protein fragment in the patient's sample. Subsequent direct sequencing of the appropriate coding region revealed a point mutation in exon 11 at nucleotide 2178, resulting in a C > T transition that caused a termination (stop codon) in amino acid 687. To our knowledge, this is the first report of mutation of the BRCA1 gene in a Filipino family, and this in-frame stop-codon mutation has not been reported previously.

Haplotype and phenotype analysis of nine recurrent BRCA2 mutations in 111 families: results of an international study

Several BRCA2 mutations are found to occur in geographically diverse breast and ovarian cancer families. To investigate both mutation origin and mutation-specific phenotypes due to BRCA2, we constructed a haplotype of 10 polymorphic short tandem-repeat (STR) markers flanking the BRCA2 locus, in a set of 111 breast or breast/ovarian cancer families selected for having one of nine recurrent BRCA2 mutations. Six of the individual mutations are estimated to have arisen 400-2,000 years ago. In particular, the 6174delT mutation, found in approximately 1% of individuals of Ashkenazi Jewish ancestry, was estimated to have arisen 29 generations ago (1-LOD support interval 22-38). This is substantially more recent than the estimated age of the BRCA1 185delAG mutation (46 generations), derived from our analogous study of BRCA1 mutations. In general, there was no evidence of multiple origins of identical BRCA2 mutations. Our study data were consistent with the previous report of a higher incidence of ovarian cancer in families with mutations in a 3.3-kb region of exon 11 (the ovarian cancer cluster region [OCCR]) (P=.10); but that higher incidence was not statistically significant. There was significant evidence that age at diagnosis of breast cancer varied by mutation (P<.001), although only 8% of the variance in age at diagnosis could be explained by the specific mutation, and there was no evidence of family-specific effects. When the age at diagnosis of the breast cancer cases was examined by OCCR, cases associated with mutations in the OCCR had a significantly older mean age at diagnosis than was seen in those outside this region (48 years vs. 42 years; P=.0005).

BRCA1 mutations in southern England

If genetic testing for breast and ovarian cancer predisposition is to become available within a public health care system there needs to be a rational and cost-effective approach to mutation analysis. We have screened for BRCA1 mutations in 230 women with breast cancer, all from the Wessex region of southern England, in order to establish the parameters on which to base a cost-effective regional mutation analysis strategy. Truncating mutations were detected in 10/155 (6.5%) consecutive cases selected only for diagnosis under the age of 40 (nine of these ten women had a strong family history of breast or ovarian cancer), 3/61 (4.9%) bilateral-breast cancer cases (all three mutations occurring among women for whom the first cancer was diagnosed under 40 years) and 8/30 (26.6%) breast cancer cases presenting to the genetics clinic (for whom a strong family history of breast and/or ovarian cancer was present). Ten different mutations were detected in 17 families, but three of these accounted for 10/17 (59%) of the families. The cost of screening the population for mutations in the entire BRCA1 gene is unacceptably high. However, the cost of screening a carefully selected patient cohort is low, the risk of misinterpretation much less and the potential clinical benefits clearer.

Studies on functional status of circulating lymphocytes in unaffected members from cancer families

That the inheritance of mutations in tumor susceptibility genes alone cannot determine risk for developing cancer is now well accepted. Immune functions have long been recognized as one of the important risk modifying factors in this regard. In an attempt to develop a multiparametric approach to identify high risk individuals from cancer families, we have examined NK cell function in unaffected members from familial breast cancer families. We have also carried out a parallel study of T lymphocyte functions in these individuals. Our studies demonstrate a significantly lower NK cell activity in members from cancer families. T lymphocyte activity also showed a similar trend, with the unaffected members demonstrating a notably lowered T lymphocyte function. In addition the data from patients reveals differential sensitivity of NK and T lymphocyte function to the disease phenotype. Implications of these observations are discussed.

Effect of smoking on breast cancer in carriers of mutant BRCA1 or BRCA2 genes

BACKGROUND

Smoking has carcinogenic effects, and possibly antiestrogenic effects as well, but it has not been found to be a risk factor for breast cancer in women in the general population. However, hereditary breast cancer is primarily a disease of premenopausal women, and interactions between genes and hormonal and environmental risk factors may be particularly important in this subgroup.

METHODS

We conducted a matched case-control study of breast cancer among women who have been identified to be carriers of a deleterious mutation in either the BRCA1 or the BRCA2 gene. These women were assessed for genetic risk at one of several genetic counseling programs for cancer in North America. Information about lifetime smoking history was derived from a questionnaire routinely administered to women who were found to carry a mutation in either gene. Smoking histories of case subjects with breast cancer and age-matched healthy control subjects were compared. Odds ratios for developing breast cancer were determined for smokers versus nonsmokers by use of conditional logistic regression for matched sets after adjustment for other known risk factors.

RESULTS

Subjects with BRCA1 or BRCA2 gene mutations and breast cancer were significantly more likely to have been nonsmokers than were subjects with mutations and without breast cancer (two-sided P = .007). In a multivariate analysis, subjects with BRCA1 or BRCA2 mutations who had smoked cigarettes for more than 4 pack-years (i.e., number of packs per day multiplied by the number of years of smoking) were found to have a lower breast cancer risk (odds ratio = 0.46, 95% confidence interval = 0.27-0.80; two-sided P = .006) than subjects with mutations who never smoked.

CONCLUSIONS

This study raises the possibility that smoking reduces the risk of breast cancer in carriers of BRCA1 or BRCA2 gene mutations.

Breast cancer susceptibility genes. BRCA1 and BRCA2

Mutations in the BRCA1 and BRCA2 genes lead to an increased susceptibility to breast, ovarian, and other cancers. It is estimated that 3%-8% of all women with breast cancer will be found to carry a mutation in 1 of these genes. Families with multiple affected first-degree relatives and patients with early-onset disease have been found to harbor mutations at a higher frequency. The BRCA1 and BRCA2 genes code for large proteins that bear no resemblance to other known genes. In the cell, they appear to act as tumor suppressor genes and play a role in the maintenance of genome integrity, although the precise function of these genes has yet to be discovered. A large number of distinct mutations have been found in cancer families around the world. The majority of the defined pathologic mutations result in premature truncation of the protein (frameshift and nonsense mutations). These mutations may substantially increase the risk for breast and ovarian cancer, but a precise risk estimate for each different mutation cannot be determined. Depending on the familial context, the risk of breast cancer associated with carrying a mutation has been estimated to range from 50% to 85%. The role of these genes in sporadic cancer remains unknown. Patients and physicians considering BRCA1 and BRCA2 genetic testing are faced with a difficult decision. The diversity of mutations and lack of general population data prevent accurate risk prediction. This is further complicated by the paucity of data on effective prevention strategies for those identified at higher risk. Thus, the nature of clinical testing for BRCA1 and BRCA2 continues to present challenges that reinforce the necessity of personal choice within the context of thorough genetic counseling.

Genetic identification of multiple loci that control breast cancer susceptibility in the rat

We have used a rat model of induced mammary carcinomas in an effort to identify breast cancer susceptibility genes. Using genetic crosses between the carcinoma-resistant Copenhagen (COP) and carcinoma-sensitive Wistar-Furth rats, we have confirmed the identification of the Mcs1 locus that modulates tumor number. We have now also identified two additional loci, Mcs2 and Mcs3. These three loci map to chromosomes 2, 7, and 1, respectively, and interact additively to suppress mammary carcinoma development in the COP strain. They are responsible for a major portion of the tumor-resistant phenotype of the COP rat. No loss of heterozygosity was observed surrounding the three loci. A fourth COP locus, Mcs4, has also been identified on chromosome 8 and acts in contrast to increase the number of carcinomas. These results show that mammary carcinoma susceptibility in the COP rat is a polygenic trait. Interestingly, a polymorphism in the human genomic region homologous to the rat Mcs4 region is associated with an increased breast cancer risk in African-American women. The isolation of the Mcs genes may help elucidate novel mechanisms of carcinogenesis, provide information important for human breast cancer risk estimation, and also provide unique drug discovery targets for breast cancer prevention.

Breast cancer genes and the surgeon

Two genes, called BRCA-1 and BRCA-2, have been identified that appear to be responsible for the majority of familial breast cancer syndromes. These genes now play a prominent role in the practice of the surgeon treating breast cancer. Additional genes, PTEN (Cowden disease), MSH1 or MLH2 (HNPCC), and p53 (Li-Fraumeni syndrome) are responsible for other breast cancer syndromes but have not yet entered the clinical arena on a large scale. The risk of breast and ovarian cancer by age 70 in a BRCA-1 mutation carrier is estimated at 55-75% and 16-26 %, respectively, overall, and as high as 87% and 44% in those with a strong family history. The cancer risks associated with BRCA-2 mutations appear to be somewhat lower than those of BRCA-1. BRCA mutations show a strong founder effect. This is best recognized in the Ashkenazi Jewish community, in which the incidence of one of three characteristic mutations is about 2%. In other ethnic groups the pattern of mutations is different, with over 100 distinct mutations throughout the genes having been described. Most mutations so far have been frame-shift or mis-sense mutations, although large deletions have also been described. Thus, in most situations, assessment of the whole coding sequence is required to confirm or exclude a mutation. Guidelines to suggest who is likely to be a mutation carrier are being clarified, but the appropriate management of someone who tests positive remains difficult. Prophylactic mastectomy and oophorectomy are likely to offer substantial gains in life expectancy to mutation carriers, especially for young women with a strong family history. Unfortunately, there are no currently available strategies to eliminate the risk of breast or ovarian cancer. The psychological impact of testing also remains poorly understood, and the danger of various forms of discrimination remain. These factors must be clearly understood by all parties prior to testing. The process of a dynamic, interactive informed consent--much more than a simple printed document--and also counseling are central to the testing process.

A missense mutation in the BRCA2 gene in three siblings with ovarian cancer

Inherited susceptibility to ovarian cancer has been associated with germline defects at several loci. The major known ovarian cancer susceptibility gene is BRCA1 on chromosome 17q, which confers a risk of approximately 60% by the age of 70 years. Truncating mutations in BRCA2 on chromosome 13q also predispose to ovarian cancer, although they confer a lower risk than mutations in BRCA1. We have studied the molecular basis of ovarian cancer predisposition in a Finnish family with three affected sisters. Analysis of polymorphic markers provided evidence against linkage to BRCA1, but the sibship was consistent with linkage to BRCA2. Conformation-sensitive gel electrophoresis was used to screen the entire coding sequence of BRCA2. A G to A transition at nucleotide 8702 was observed, which is predicted to convert glycine 2901 to aspartate in the encoded protein. This sequence variant was not detected in 220 cancer-free Finnish control individuals, or in several hundred cancer families of many nationalities previously screened for BRCA2 mutations. Taken together with the fact that this amino acid residue and the surrounding region of BRCA2 is identical in mouse and chicken, the data suggest that this alteration is a disease-causing BRCA2 missense mutation. Previously published data indicate that the risks of breast and ovarian cancer conferred by BRCA2-truncating mutations varies with the position of the mutation in the gene. The missense mutation reported here suggests that the BRCA2 domain including and surrounding glycine 2901 may be more important in preventing neoplastic transformation in ovarian epithelium than in breast epithelium.

Hereditary breast cancer

Genetic predisposition is responsible for 5-10% of all breast cancer, and a much larger percent of early-onset disease. Within the past few years, a number of genes associated with a high risk of breast cancer have been identified, including BRCA1, BRCA2, p53, and the Cowden disease gene PTEN/MMAC1. These genes appear to function as tumor suppressors, and although their mutation frequency in the general population is low, certain populations have a carrier frequency of up to 1% for particular BRCA1 and BRCA2 mutations. The isolation of these genes is likely to provide important insight into the pathogenesis of human cancer. The clinical application of these molecular discoveries raises controversial issues regarding presymptomatic testing for patients suspected of harboring cancer predisposing mutations.