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

Prevalence of founder BRCA1 and BRCA2 mutations in unselected French Canadian women with breast cancer

The frequency of BRCA1 and BRCA2 mutations in women with breast cancer varies according to the age at diagnosis, family history of cancer, and ethnicity/country of origin. We set out to estimate the frequency of seven previously described founder mutations in BRCA1 and BRCA2 in all eligible French Canadian women diagnosed with invasive breast cancer at one Montreal hospital over a 20-month period. One hundred and ninety-two patients were eligible and 127 (66.2%) provided blood for genetic testing. We identified 4 women who carried a founder mutation (3.1%, 95% confidence interval 0.9-7.9%) in this population. Interestingly, all the mutations were in BRCA2. The mean age at diagnosis for mutation carriers was 51.2 years (range 49.1-53.5). Two of these 4 cases were lobular invasive carcinomas and 2 were ductal carcinomas, histological grade 1 or 2. Despite a small tumor size (< or =20 mm), axillary nodal involvement was present in 3 women. Estrogen receptors were strongly expressed in all cases. Two of the 4 cases reported a strong family history of breast cancer, but a family history of site-specific breast cancer was a relatively poor indicator of the presence of BRCA2 mutations. The absence of BRCA1 mutations may be a result of chance, but may also reflect different geographical origins of the most common BRCA1 mutations within the French Canadian population.

Breast cancer genetics: what we know and what we need

Breast cancer results from genetic and environmental factors leading to the accumulation of mutations in essential genes. Genetic predisposition may have a strong, almost singular effect, as with BRCA1 and BRCA2, or may represent the cumulative effects of multiple low-penetrance susceptibility alleles. Here we review high- and low-penetrance breast-cancer-susceptibility alleles and discuss ongoing efforts to identify additional susceptibility genes. Ultimately these discoveries will lead to individualized breast cancer risk assessment and a reduction in breast cancer incidence.

A computer model to simulate family history of breast/ovarian cancer in BRCA1 mutation carriers

The BRCA1 gene and its relationship to family history of breast/ovarian cancer are difficult to study in a population because of practical and ethical issues. The paucity of information on BRCA1 in the general population was a major theme in a recent review of genetic testing in Canada. We develop a simulation model to mimic genetic inheritance and cancer incidence in the family of someone with a germline BRCA1 mutation. Given someone's age and family structure, our model simulates his or her family history in three steps: (1) determine which family members have the mutation, (2) determine the ages of family members and (3) determine which family members have breast/ovarian cancer. Each step involves random variation. Some parameters in our model are estimated using local (British Columbia, Canada) population data. The breast/ovarian cancer risk associated with BRCA1 mutations is estimated using values published in the literature. An example is provided to illustrate the model's application. The model incorporates results from genetics, demography and epidemiology, but requires several additional assumptions. Research to address these assumptions is recommended.

Germline mutations in BRCA1 and BRCA2 in breast-ovarian families from a breast cancer risk evaluation clinic

PURPOSE

Data from the Breast Cancer Linkage Consortium suggest that the proportion of familial breast and ovarian cancers linked to BRCA1 or BRCA2 may be as high as 98% depending on the characteristics of the families, suggesting that mutations in BRCA1 or BRCA2 may entirely account for hereditary breast and ovarian cancer families. We sought to determine what proportion of families with both breast and ovarian cancers seen in a breast cancer risk evaluation clinic are accounted for by coding region germline mutations in BRCA1 and BRCA2 as compared to a linkage study group. We also evaluated what clinical parameters were predictive of mutation status.

PATIENTS AND METHODS

Affected women from 100 families with at least one case of breast cancer and at least one case of ovarian cancer in the same lineage were screened for germline mutations in the entire coding regions of BRCA1 and BRCA2 by conformation-sensitive gel electrophoresis, a polymerase chain reaction-based heteroduplex analysis, or direct sequencing.

RESULTS

Unequivocal deleterious mutations were found in 55% (55 of 100) of the families studied. Mutations in BRCA1 and BRCA2 accounted for 80% and 20% of the mutations overall, respectively. Using multivariate analysis, the strongest predictors of detecting a mutation in BRCA1 or BRCA2 in this study group were the presence of a single family member with both breast and ovarian cancer (P <.0009; odds ratio [OR], 5.68; 95% confidence interval [CI], 2.04 to 15.76) and a young average age at breast cancer diagnosis in the family (P <.0016; OR, 1.69; 95% CI, 1.23 to 2.38).

CONCLUSION

These results suggest that at least half of breast/ovarian families evaluated in a high-risk cancer evaluation clinic may have germline mutations in BRCA1 or BRCA2. Whether the remaining families have mutations in noncoding regions in BRCA1, mutations in other, as-yet-unidentified, low-penetrance susceptibility genes, or represent chance clustering remains to be determined.

A single nucleotide polymorphism in the RAD51 gene modifies cancer risk in BRCA2 but not BRCA1 carriers

BRCA1 and BRCA2 carriers are at increased risk for both breast and ovarian cancer, but estimates of lifetime risk vary widely, suggesting their penetrance is modified by other genetic and/or environmental factors. The BRCA1 and BRCA2 proteins function in DNA repair in conjunction with RAD51. A preliminary report suggested that a single nucleotide polymorphism in the 5' untranslated region of RAD51 (135C/G) increases breast cancer risk in BRCA1 and BRCA2 carriers. To investigate this effect we studied 257 female Ashkenazi Jewish carriers of one of the common BRCA1 (185delAG, 5382insC) or BRCA2 (6174delT) mutations. Of this group, 164 were affected with breast and/or ovarian cancer and 93 were unaffected. RAD51 genotyping was performed on all subjects. Among BRCA1 carriers, RAD51-135C frequency was similar in healthy and affected women [6.1% (3 of 49) and 9.9% (12 of 121), respectively], and RAD-135C did not influence age of cancer diagnosis [Hazard ratio (HR) = 1.18 for disease in RAD51-135C heterozygotes, not significant]. However, in BRCA2 carriers, RAD51-135C heterozygote frequency in affected women was 17.4% (8 of 46) compared with 4.9% (2 of 41) in unaffected women (P = 0.07). Survival analysis in BRCA2 carriers showed RAD51-135C increased risk of breast and/or ovarian cancer with an HR of 4.0 [95% confidence interval 1.6-9.8, P = 0.003]. This effect was largely due to increased breast cancer risk with an HR of 3.46 (95% confidence interval 1.3-9.2, P = 0.01) for breast cancer in BRCA2 carriers who were RAD51-135C heterozygotes. RAD51 status did not affect ovarian cancer risk. These results show RAD51-135C is a clinically significant modifier of BRCA2 penetrance, specifically in raising breast cancer risk at younger ages.

A probability model for predicting BRCA1 and BRCA2 mutations in breast and breast-ovarian cancer families

Germline mutations in BRCA1 and BRCA2 genes predispose to hereditary breast and ovarian cancer. Our aim was to find associations between the clinical characteristics and positive mutation status in 148 breast cancer families in order to predict the probability of finding a BRCA mutation in a family. Several factors were associated with mutations in univariate analysis, whereas in multivariate analysis (logistic regression with backward selection) only the age of the youngest breast cancer patient and the number of ovarian cancer cases in a family were independent predictors of BRCA mutations. A logistic model was devised to estimate the probability for a family of harbouring a mutation in either BRCA1 or BRCA2. Altogether, 63 out of 148 families (43%) and 28 out of 29 (97%) mutation carrier families obtained probabilities over 10%. The mean probability was 55% for mutation-positive families and 11% for mutation-negative families. The models by Couch et al (1997) and Shattuck-Eidens et al (1997) previously designed for BRCA1 were also tested for their applicability to distinguish carrier families with mutations in either gene. The probability model should be a useful tool in genetic counselling and focusing the mutation analyses, and thus increasing also the cost-effectiveness of the genetic screening.

Germ line mutations associated with breast cancer susceptibility

Laboratory-based research in germ line mutations associated with breast cancer susceptibility is rapidly being integrated into clinical practice with profound implications. A Medline search was performed for all relevant articles published since 1990. Where appropriate, historical articles referenced in those identified were also reviewed. The results suggested that while mutations in the BRCA1 and BRCA2 genes are the most clinically relevant, much of the data on which clinical decisions are based must be interpreted with wide confidence intervals. Between 1 in 152 and 1 in 833 individuals carry such mutations. They account for less than 5% of all breast cancer, but up to 10% of cancers in those under the age of 40 years. Founder mutations are responsible for a larger proportion of breast cancer cases within certain inbred communities. Phenotypic expression and penetrance of different mutations is not currently predictable and estimates of penetrance are largely based on highly selected populations. BRCA1 mutations are more commonly associated with ovarian cancer than BRCA2 mutations. BRCA1 cancers tend to have more distinct pathological features and are usually oestrogen receptor (ER)-negative. To conclude, the evidence in this review suggests that caution should be exercised when translating scientific progress in breast cancer germ line genetics into clinical practice. Most of the available data are derived from studies on highly selected populations. The importance of other less penetrant, but more prevalent, germ line mutations may be realised in the future.

Involvement of BRCA1 and BRCA2 in breast cancer in a western Finnish sub-population

To date, two major familial breast cancer predisposition genes, BRCA1 and BRCA2, have been identified with hundreds of germ-line mutations, accounting for 5--10% of all breast cancer and 40--60% of all inherited breast cancer. Unexpectedly elevated incidence of breast cancer, especially in the older age classes, was observed in a Western Finnish region representing a relatively homogeneous population. This study was designed to test the hypothesis that there are inherited BRCA1 or BRCA2 mutations, which confer variable and/or age-dependent penetrance on carriers. Expecting a founder effect, we searched for geographical clustering of breast cancer cases and searched for associations between the affected phenotype and shared genomic segments in the BRCA1 and BRCA2 genomic regions. Our haplotype association study did not reveal any founder effects for either BRCA1 or BRCA2. However, there were two mutations prevalent in this geographical area with minor founder effects, BRCA2 T8555G and 999del5. This is one of the few geographically ascertained, population-based studies that indicate an overall frequency of BRCA1 and BRCA2 mutations at about 2--3% in all breast cancer cases. The geographical clustering of breast cancer cases was not explained by BRCA1 or BRCA2 genes.

Breast cancer mortality among Ashkenazi Jewish women in São Paulo and Porto Alegre, Brazil

BACKGROUND

Increased BRCA1 and BRCA2 germline mutation rates have been reported in Ashkenazi Jewish women in North America, Europe and Israel, and have been mentioned as possibly related to a higher incidence of breast and ovarian cancer among these communities. The present study was carried out with the aim of obtaining evidence on the magnitude of breast cancer as a cause of death among Ashkenazi women in Brazil.

METHODS

We reviewed all death certificates archived in the Jewish Burial Societies of São Paulo (1971-1997) and Porto Alegre (1948-1997), two of the main and oldest Jewish communities in Brazil. Breast cancer observed deaths were compared with expected deaths according to breast cancer mortality in the general population.

RESULTS

The observed ratios were approximately quite close to unity, suggesting a similar breast cancer mortality pattern among the Ashkenazi population and the general population in both cities. These results maintain similar behavior regardless of whether analyzed before or after the mid-1980s, when mammography came to be increasingly performed in Brazil. Cancer proportional mortality ratios were 1.04 (0.83-1.29) in São Paulo and 1.16 (0.84-1.57) in Porto Alegre before 1985, and 1.17 (1.00-1.44) and 1.21 (0.81-1.79), respectively, between 1985 and 1997. Some evidence of the maintenance of protective risk factors such as high parity has been observed among Ashkenazi women in São Paulo.

CONCLUSION

A quite similar breast cancer mortality pattern was observed between Ashkenazi Jewish women and the general population in São Paulo and Porto Alegre, Brazil. These results may suggest an environmental role on germ mutation expression reported in this ethnic group.

Acceleration of chromosomal instability by loss of BRCA1 expression and p53 abnormality in sporadic breast cancers

Correlation of chromosomal instability (CIN) with BRCA1 expression and p53 abnormality was studied in sporadic breast cancers since these genes are implicated in the double strand DNA repair and mitotic checkpoint, and loss of their function is speculated to result in the accumulation of CIN. CIN values (percentage of cells with non-modal chromosomes) were determined by fluorescence in situ hybridization of chromosomes 1, 11, and 17. BRCA1 expression was studied by immunostaining, and p53 abnormality was studied by immunostaining and polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP). CIN values of BRCA1 negative/p53 normal tumors (28.9+/-13.8, n=23) and those of BRCA1 positive/p53 abnormal tumors (27.0+/-2.3, n=3) were not significantly different from those of BRCA1 positive/p53 normal tumors (23.8+/-11.5, n=10). On the other hand, BRCA1 negative/p53 abnormal tumors (41.2+/-12.7, n=23) showed a significant (P<0.01) increase in CIN values than BRCA1 positive/p53 normal tumors. There was no significant association between CIN values and menopausal status, tumor size, histological grade, lymph node status, or estrogen receptor status. These results suggest that BRCA1 down-regulation and p53 abnormality work synergistically to induce CIN in breast cancers, and that clinico-pathological characteristics of breast cancers with high CIN still remain to be established.

BRCA1 mutations and clinicopathological features in a sample of Italian women with early-onset breast cancer

Breast cancer in young women is uncommon and often presents with unfavourable biopathological features. Although early age at onset could suggest a genetic susceptibility to cancer, the appropriateness of BRCA1 testing for women with early-onset breast cancer and modest family history (FH) is controversial. 40 Women diagnosed with breast cancer at the age of 35 years or less, unselected for FH, were screened for germ line BRCA1 mutations by automated sequencing of exons 2, 5, 6, 11, 13 and 20. Overall, deleterious mutations were evidenced in 6 (15%) patients. With regard to FH, mutations were detected in 14%, 11% and 29% of women with none, weak and strong FH, respectively. Large tumour size, grade 3, lack of oestrogen receptors and high proliferation rate were significantly more common in mutation carriers (MC). Our data support both the appropriateness of testing young breast cancer patients and the frequency of unfavourable features in BRCA1-related breast cancer. It is hypothesised that BRCA1 mutations partially justify the high rate of aggressive breast cancer in young patients and that combining age and breast cancer phenotype could help to identify probable MC.

Prevalence of BRCA1 in a hospital-based population of Dutch breast cancer patients

The prevalence of disease-related BRCA1 mutations was investigated in 642 Dutch breast cancer patients not selected for family history or age at diagnosis. They were tested for germline mutations in the BRCA1 gene using an assay which detects small deletions and insertions (DSDI), as well as the two major genomic founder deletions present in the Dutch population. Data on family history and bilateral breast cancer were obtained retrospectively. Ten protein truncating mutations were detected and one in-frame deletion with an unknown relation to disease risk. Four patients carried the Dutch founder deletion of exon 22. Based on these results the estimated prevalence of breast cancer in the general population in the Netherlands attributable to BRCA1 mutations is 2.1%. Under 40 years-of-age and under 50 years-of-age this prevalence is 9.5% and 6. 4%, respectively. All mutation carriers were under 50 years-of-age at diagnosis of the first breast cancer, and five did not have any relative with breast cancer. The proportions of bilateral breast cancer in the mutation carriers and non-carriers did not differ from each other. These data indicate that in the general Dutch breast cancer population the great majority of BRCA1 mutations will be found in women diagnosed under 50 years-of-age.

Founder BRCA 1 and 2 mutations among a consecutive series of Ashkenazi Jewish ovarian cancer patients

OBJECTIVE

The purpose of this study was to describe the incidence of the three Ashkenazi Jewish founder genetic BRCA 1 and 2 mutations among an unselected, consecutive group of Ashkenazi Jewish ovarian cancer patients.

MATERIALS AND METHODS

From 7/30/96 to 4/12/99, 92 Ashkenazi Jewish patients with histologically confirmed epithelial ovarian cancer had surgery. All of these patients had DNA extracted from 5-microm sections of their paraffin-embedded surgical specimen tissue blocks using the Qiagen QIAamp tissue extraction kit. A multiplex (triplex) polymerase chain reaction was performed to amplify fragments for the 185delAG, 5382insC, and 6174delT mutations. The products were hybridized with normal and mutant probes for each of the three mutations. All clinical data were collected retrospectively and statistical significance was evaluated using the chi(2) test or a two-tailed Fisher's exact test, depending on the sample size.

RESULTS

There were 23 patients positive for one of the three founder BRCA mutations. Fourteen patients were positive for the 185delAG mutation, 2 patients were positive for the 5382insC mutation, and 7 patients were positive for the 6174 delT mutation (61, 9, and 30%, respectively). This represented a 25% incidence (95% CI: 16-34%) of one of the three founder BRCA mutations among our 92 Ashkenazi Jewish ovarian cancer patients. None of the patients was positive for more than one mutation. There was no statistically significant difference in parity, histology, grade, or stage between the BRCA founder mutation positive and negative patients. The difference between the percentage of mutation carriers among patients with one affected first-degree relative (13/22 or 59%) compared to those without at least one affected first-degree relative (10/70 or 14%) was highly significant (P = 0.001).

CONCLUSIONS

Ashkenazi Jewish ovarian cancer patients represent a group with a high likelihood of being carriers of BRCA 1 and 2 genetic mutations, regardless of family history. As a result, all ovarian cancer patients who are of Ashkenazi Jewish descent should be counseled regarding BRCA 1 and 2 genetic screening, as well as the potential implications of these results for the patient as well as her relatives in terms of prognosis, screening, chemoprevention, and consideration of prophylactic surgical procedures.

Clinical management of BRCA1- and BRCA2-associated breast cancer

The recent discovery of the breast cancer-associated genes BRCA1 and BRCA2 has changed the clinical care provided to women at high risk of breast cancer. We will review what is currently known about the clinical management of patients who bear (or are suspected of bearing) mutations in either of these two genes. The issues related to establishing a diagnosis of inherited breast cancer, deciding which women are candidates for testing, the limitations of testing, and the predictive power of these tests are addressed. The prognostic features of cancers associated with a BRCA1 and BRCA2 mutation are reviewed. Further, guidelines for prophylaxis of women with a BRCA1 or BRCA2 mutation are given and recommendations are made for the care of mutation carriers with cancer.

Characteristics of BRCA1 mutations in a population-based case series of breast and ovarian cancer

Breast and ovarian cancers account for approximately 210000 newly diagnosed cases per year. More than half a million American women are estimated to be carriers of a breast cancer susceptibility gene. The purpose of this study was to assess the association of characteristics such as, age at diagnosis, race/ethnicity and family history of cancer with inherited BRCA1 mutations in a population-based sample of breast and ovarian cancer cases. No selection was made by race, age at diagnosis or positive family history of breast or ovarian cancer. The population under study was all breast cancer cases diagnosed in Orange County, CA, during the 1-year period beginning 1 March 1994 and all ovarian cancer cases diagnosed in Orange County during the 2-year period beginning 1 March 1994. This report focuses on the first consecutively ascertained 802 participating probands enrolled in the study, of which 9 were male breast cancer probands, 673 were female breast cancer probands and 120 were ovarian cancer probands. We observed 11 BRCA1 mutations or 1.6% (95% CI: 0.8-2.9) among the 673 female breast cancer probands and 4 BRCA1 mutations or 3.3% (95% CI: 0.8-8. 3) among the 120 ovarian cancer probands. No BRCA1 mutations were identified among the 98 non-white breast and ovarian cancer probands. The prevalence of BRCA1 mutations in non-Hispanic-white breast cancer cases below the age of 50 years was 2%. Positive family history of breast or ovarian cancers was significantly associated with BRCA1 mutation status among breast cancer probands. Similarly, positive family history of breast or ovarian cancer was significantly associated with BRCA1 mutation status among the ovarian cancer probands. In summary, we present results on the prevalence of BRCA1 mutations in a significantly larger sample of population-based breast and ovarian cancer cases than previously reported. The results indicate that, using a conservative approach to targeted genotyping of BRCA1, the frequency of mutations was consistent with those reported using similar methods of population-based case ascertainment.

Clinico-pathological characteristics of BRCA1- and BRCA2-related breast cancer

Approximately 2% to 5% of all breast cancers are hereditary, meaning that the cancer predisposition is carried as a monogenic trait. Several highly penetrant breast cancer predisposing genes have been identified. These discoveries will permit a refined description of breast cancer occurring as part of the different genetic syndromes. We reviewed the medical literature on the clinico-pathological features of breast cancer associated with the major breast cancer susceptibility genes BRCA1 and BRCA2. BRCA1-associated breast cancers are more frequently ductal invasive, high-grade carcinomas with an important lymphocytic infiltration. They are aneuploid, estrogen and progesterone receptors negative, and p53 positive. BRCA2-related breast cancers tend to be higher-grade tumors than are non-hereditary cases, although this association is less strong then for BRCA1 cases. These tumors exhibit substantially less tubule formation, but mitotic count and cellular pleomorphism do not differ significantly from those of sporadic cases. The overall pattern of the identified pathological characteristics suggests a carcinogenic pathway in BRCA1- and BRCA2-related breast cancers different from that found in sporadic cases. The probability of finding a BRCA1/2 germ-line mutation is partly determined by these characteristics. In addition, these features will likely influence the behavior of BRCA1/2-related breast cancer.

Novel germline mutations in the PTEN tumour suppressor gene found in women with multiple cancers

Germline mutations in PTEN can predispose people to Cowden syndrome (CS) and Bannayan-Ruvalcaba-Riley (BRR) syndrome, rare, autosomal dominantly inherited neoplastic disorders. To determine whether germline mutations in PTEN contribute to genetic predisposition to multiple primary tumours within the general population, we conducted a nested case-control study, among 32 826 members of the prospective Nurses' Health Study cohort; cases were women with more than one primary tumour at different anatomical sites. We screened all nine exons of PTEN and flanking intronic splice sites for all 103 eligible cases using SSCP and sequencing. We observed two novel germline heterozygous missense mutations in exon 5 in five of the cases; three were V119L and two were V158L. Neither mutation was observed in 115 controls free of diagnosed cancer (p = 0.02). Both mutants showed partial tumour suppressor activity when compared to wild type PTEN when transfected into a PTEN null breast cancer cell line. The phenotype was cell line specific suggesting that genetic background affects growth suppression activity of the mutants. These data provide evidence that germline mutations in PTEN may be a more frequent predisposing factor for cancers in women than previously suggested.

Establishment and characterization of a breast cell strain containing a BRCA1 185delAG mutation

OBJECTIVE

The aim of this study was to examine whether cells containing the heterozygous form of a BRCA1 185delAG mutation would exhibit abnormal growth or an altered response to DNA damage.

METHODS

A primary culture of human mammary epithelial cells (90P) was obtained from the nontumor breast tissue of a 35-year-old patient who had undergone a mastectomy for removal of a breast tumor. These cells were immortalized (90PE6E7) following retroviral infection with HPV-16 viral E6/E7. genes. Both the 90P cell strain and the cell line were characterized for their ability to grow in culture, form colonies in soft agar, and produce tumors in athymic nude mice compared to normal breast epithelial cells containing wild-type BRCA1. 90P cells were also analyzed for cellular response to gamma radiation and H(2)O(2).

RESULTS

These cells were confirmed to contain a frameshift mutation, 185delAG, of the BRCA1 gene. Despite being heterozygous for wild-type BRCA1, the 220-kDa full-size BRCA1 protein was abundantly expressed. 90P and 90PE6E7 cells grew at a similar rate and were anchorage dependent. 90PE6E7 also failed to form tumors in athymic nude mice. Finally, 90P cells exhibited a survival response similar to that of normal mammary epithelial cells to radiation damage and exposure to oxidative stress.

CONCLUSION

To our knowledge the 90P cells and the 90PE6E7 cells are the first characterized, non-tumor-derived breast epithelial cells that are heterozygous for the BRCA1 germline mutation 185delAG. Our conclusion is that these BRCA1 mutant cells appear to have growth and stress response characteristics similar to those of normal human breast cells, which is consistent with the hypothesis that loss of heterozygosity must occur to impair putative BRCA1 function.

Unravelling genetic data by arrayed primer extension

We have developed a method for arrayed primer extension (APEX) on an oligonucleotide microchip together with the 4-color fluoresence imaging equipment and supporting software, that allows analysis of the DNA sequence and changes in it. Mutation analysis of BRCA1 gene and single nucleotide polymorphism (SNP) chip for genotyping were used as a model system. Chip surface chemistry, template preparation and APEX reaction conditions were optimised and the assay is ready to be implemented in variety of DNA analysis from SNP testing to DNA resequencing.

Recent advances in breast cancer biology

Breast cancer remains the leading cause of death in American women 30 to 70 years of age, and research in the field of breast cancer continues at an explosive pace. Our understanding of the molecular basis of familial breast cancer has advanced significantly through investigation of the tumor suppressor gene BRCA1, as has our knowledge of the role of the ATM gene and predisposition to breast cancer in ataxia-telangiectasia carriers. In addition, progress has been made in understanding the role of HER-2/neu as a prognostic factor in breast cancer. In this review, some of the recent advances in breast cancer biology that are relevant to these areas of study are highlighted.

Penetrances of BRCA1 1675delA and 1135insA with respect to breast cancer and ovarian cancer

For genetic counseling and predictive testing in families with inherited breast-ovarian cancer, penetrances and expressions of the underlying mutations should be known. We have previously reported two BRCA1 founder mutations in the Norwegian population. Index cases for the present study were found two different ways: through a series of consecutive ovarian cancers (n=16) and through our family cancer clinic (n=14). Altogether, 20 of the patients had BRCA1 1675delA, and 10 had 1135insA. Their relatives were described with respect to absence/presence of breast and/or ovarian cancer. Of 133 living female relatives, 83 (62%) were tested for the presence of a mutation. No difference, in penetrance and expression, between the two mutations were found, whereas differences according to method of ascertainment were seen. The overall findings were that disease started to occur at age 30 years and that by age 50 years 48% of the mutation-carrying women had experienced breast and/or ovarian cancer. More ovarian cancers than breast cancers were recorded. Both penetrance and expression (breast cancer vs. ovarian cancer) were different from those in reports of the Ashkenazi founder mutations. Whether the reported differences reflect true differences and/or methodological problems is discussed. An observed excess of mutation carriers could not be accounted for by methodological problems; possible explanations were a "true" low penetrance or preferential segregation.

Prevalence and penetrance of BRCA1 and BRCA2 gene mutations in unselected Ashkenazi Jewish women with breast cancer

BACKGROUND

Approximately 2.0%-2.5% of Ashkenazi Jewish women carry one of three founding mutations in the BRCA1 and BRCA2 genes, and each mutation is associated with a high lifetime risk of invasive breast cancer. We investigated the extent to which these three mutations contribute to breast cancer incidence in the Ashkenazi Jewish population.

METHODS

We ascertained 457 Jewish women with prevalent cases of breast cancer who were unselected for age or family history of the disease; 412 of these women were tested for the three founder mutations (case patients). Control subjects consisted of 360 non-Jewish women with breast cancer (control patients) and 380 healthy Jewish women with no history of cancer (control subjects).

RESULTS

Mutations were found in 48 (11.7%) of 412 Jewish case patients. Forty-six of 48 mutations occurred in women with early-onset breast cancer (<50 years) or a history of ovarian or early-onset breast cancer in a first-, second-, or third-degree relative. The estimated penetrance to age 70 years for breast cancer was 59.9% for the BRCA1 gene mutations and 28.3% for the BRCA2 gene mutation. Compared with Jewish control subjects, the relative risk (RR) of breast cancer for first-degree relatives of mutation carriers was 5.16 (95% confidence interval [CI] = 3.14-8. 48), but risk was also increased for relatives of noncarriers (RR = 1.66; 95% CI = 1.18-2.33). The RR of prostate cancer for first-degree relatives of Jewish case patients was 3.36 (95% CI = 1. 49-7.56).

CONCLUSIONS

Approximately 12% of breast cancers in the Ashkenazi Jewish population are attributable to mutations in the BRCA1 or BRCA2 gene. Genetic testing may be useful when Jewish women with breast cancer are diagnosed before age 50 years or have a close relative with ovarian or early-onset breast cancer. An association between breast and prostate cancers was observed in our study population.

Genetic testing of breast and ovarian cancer patients: clinical characteristics and hormonal risk modifiers

OBJECTIVES

Carriers of the mutations 185delAG and 5382insC in the BRCA1 gene and 6174delT in the BRCA2 gene have a substantial life-time risk for breast and ovarian cancers (BC and OC). The aim of the study was to identify the clinical features and the hormonal risk modifiers in mutation carriers and the implication in suggested guidelines for treatment decisions in BRCA1/2 carrier patients.

STUDY DESIGN

Breast and/or ovarian cancer patients from the Oncology and Cancer Genetic clinics were tested for the three Ashkenazi founder mutations: 87 patients were identified as carriers of one of these mutations. Clinical presentation and age at onset were correlated with the mutations, in patients with bilateral BC or BC and OC, the length of time that elapsed between the diagnosis of the two cancers was recorded. We compared BC and OC patients with regard to ages at menarche, first pregnancy and menopause, number of pregnancies and deliveries, the use of oral contraceptives, hormonal replacement therapy and fertility treatments.

RESULTS

The carriers of the three BRCA1/2 Ashkenazi founder mutations did not differ in clinical presentation nor age at onset. Forty-three patients (74.1%) of 58 BC patients were diagnosed between the ages 30 and 50, only four (6.9%) patients were diagnosed after age 60. Of BC patients diagnosed before age 35, 63.6% developed second BC as compared to 25.5% of those diagnosed after age 35. Ovarian cancer was diagnosed after age 45 in 89.7% of the patients, only one patient was diagnosed under the age of 40. Oral contraceptives use was documented in 61.3% of BC patients as compared to 11.8% of OC patients. Other hormonal factors did not differ between the two groups.

CONCLUSIONS

The carriers of the three Ashkenazi founder mutations should be considered at the same risk for BC and for OC and treatment options should be the same. Mutation carriers diagnosed with BC before the age of 35 are at a very high risk for developing second breast cancer. Most ovarian cancers in carriers were diagnosed after age 45, and prophylactic oophorectomy should be postponed to the age of 45. Oral contraceptives might elevate the risk of BC in mutation carriers.

The prevalence of common BRCA1 and BRCA2 mutations among Ashkenazi Jews

Three founder mutations in the cancer-associated genes BRCA1 and BRCA2 occur frequently enough among Ashkenazi Jews to warrant consideration of genetic testing outside the setting of high-risk families with multiple cases of breast or ovarian cancer. We estimated the prevalence of these founder mutations in BRCA1 and BRCA2 in the general population of Ashkenazi Jews according to age at testing, personal cancer history, and family cancer history. We compared the results of anonymous genetic testing of blood samples obtained in a survey of >5,000 Jewish participants from the Washington, DC, area with personal and family cancer histories obtained from questionnaires completed by the participants. In all subgroups defined by age and cancer history, fewer mutations were found in this community sample than in clinical series studied to date. For example, 11 (10%) of 109 Jewish women who had been given a diagnosis of breast cancer in their forties carried one of the mutations. The most important predictor of mutation status was a previous diagnosis of breast or ovarian cancer. In men and in women never given a diagnosis of cancer, family history of breast cancer before age 50 years was the strongest predictor. As interest in genetic testing for BRCA1 and BRCA2 in the Jewish community broadens, community-based estimates such as these help guide those seeking and those offering such testing. Even with accurate estimates of the likelihood of carrying a mutation and the likelihood of developing cancer if a mutation is detected, the most vexing clinical problems remain.

Type 2 diabetes: evidence for linkage on chromosome 20 in 716 Finnish affected sib pairs

We are conducting a genome scan at an average resolution of 10 centimorgans (cM) for type 2 diabetes susceptibility genes in 716 affected sib pairs from 477 Finnish families. To date, our best evidence for linkage is on chromosome 20 with potentially separable peaks located on both the long and short arms. The unweighted multipoint maximum logarithm of odds score (MLS) was 3.08 on 20p (location, chi = 19.5 cM) under an additive model, whereas the weighted MLS was 2.06 on 20q (chi = 57 cM, recurrence risk,lambda(s) = 1. 25, P = 0.009). Weighted logarithm of odds scores of 2.00 (chi = 69.5 cM, P = 0.010) and 1.92 (chi = 18.5 cM, P = 0.013) were also observed. Ordered subset analyses based on sibships with extreme mean values of diabetes-related quantitative traits yielded sets of families who contributed disproportionately to the peaks. Two-hour glucose levels in offspring of diabetic individuals gave a MLS of 2. 12 (P = 0.0018) at 9.5 cM. Evidence from this and other studies suggests at least two diabetes-susceptibility genes on chromosome 20. We have also screened the gene for maturity-onset diabetes of the young 1, hepatic nuclear factor 4-a (HNF-4alpha) in 64 affected sibships with evidence for high chromosomal sharing at its location on chromosome 20q. We found no evidence that sequence changes in this gene accounted for the linkage results we observed.

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.