BRCA1 and BRCA2 proteins: roles in health and disease.
(9/929)
Between 5% and 10% of all breast cancer is hereditary, with patients having a strong family history of the disease. The remaining 90-95% of cases are classed as sporadic. Within the inherited group, 80-90% of cases are the result of germline mutations affecting two recently identified genes: BRCA1 and BRCA2. Since the sequencing of these genes, considerable research on the genetics of the mutation carriers has been performed, with less attention having been focused on the BRCA1 and BRCA2 proteins themselves. The structure and function of the protein products thus continues to hold mystery and might be the key to the full understanding of this complex disease. (+info)
Distinct molecular pathogeneses of early-onset breast cancers in BRCA1 and BRCA2 mutation carriers: a population-based study.
(10/929)
Breast cancers arising in women with and without a germline mutation in the BRCA1 or BRCA2 gene display different histological features, which suggests unique mechanisms of molecular pathogenesis: We used a molecular pathological analysis to define the genetic abnormalities relevant to these specific pathogeneses. Tumor material was studied from 40 women with breast cancer diagnosed before 40 years of age, sampled from a population-based study and stratified by BRCA1 and BRCA2 germline mutation status. Cases were not selected for family history or ethnic origin, and none were known to be genetically related. Thus, germline mutation itself is likely to impact on the molecular pathogenesis of these tumors, with no substantial influence due to modifying genetic or environmental factors. Breast cancers occurring in BRCA1 mutation carriers had significantly higher levels of p53 expression, including the preinvasive (carcinoma in situ) stage of disease, compared with cancers occurring in BRCA2 mutation carriers or women with no detectable germline mutation. These cancers also had a higher proliferation rate as measured by Ki-67 antibody. Expression of the prognostic factors c-erbB-2, cyclin D1, and estrogen receptor was significantly less common in BRCA1 mutation carriers. Lower levels of cyclin D1 were also found in cancers from BRCA2 mutation carriers compared with non-mutation carriers. Direct p53 mutation analysis revealed mutations in 18% of all of the early-onset breast cancers within the study and included rare insertion and deletional mutations in cancers from BRCA1 mutation carriers. Our data indicate that a BRCA1 breast cancer phenotype may be recognized by an exceptionally high proliferation rate and early and frequent p53 overexpression but infrequent selection for overexpression of several other prognostic factor proteins known to be involved in breast oncogenesis. In contrast, breast cancers arising in BRCA2 mutation carriers have a more heterogeneous phenotypic profile. (+info)
High frequency of BRCA1/2 germline mutations in 42 Belgian families with a small number of symptomatic subjects.
(11/929)
AIM: The initial risk assessments for BRCA1/2 mutation carriers and estimates of carrier frequencies were based on extended pedigrees with a large number of symptomatic subjects. When counselling based on BRCA gene mutation analysis was initiated, we faced requests for counselling mostly from members of small families with only two or three affected members. We report on the likelihood of finding a BRCA mutation in such small families. METHODS: In the first 100 families that came for oncogenetic counselling since September 1994, a BRCA1/2 gene mutation screen was initiated if there were two or more symptomatic first degree relatives, if one of them had ovarian cancer, or if one breast cancer was diagnosed before the age of 50 years. RESULTS: BRCA gene mutations were found and confirmed by sequencing in 14 out of 42 families (33%); 10 mutations were in the BRCA1 gene and four in the BRCA2 gene. Our findings indicate an increased probability of detecting a BRCA gene mutation when ovarian cancer occurred in the family. There is no increased probability of detecting a mutation with increasing numbers of breast cancers. Only 22% of the eligible presymptomatic family members opted for testing. The presymptomatic female carriers currently prefer breast surveillance rather than prophylactic surgery. CONCLUSION: BRCA1/2 gene mutation testing can be done with reasonable efficiency in the Belgian population when there are two symptomatic family members. The availability of testing does not lead to a high frequency of requests for testing by presymptomatic family members. (+info)
Novel p53 mutants selected in BRCA-associated tumours which dissociate transformation suppression from other wild-type p53 functions.
(12/929)
Inheritance of germ-line mutant alleles of BRCA1 and BRCA2 confers a markedly increased risk of breast cancer and we have previously reported a higher incidence of p53 mutations in these tumours than in grade matched sporadic tumours. We have now characterized these p53 mutants. The results of these studies identify a novel class of p53 mutants previously undescribed in human cancer yet with multiple occurrences in BRCA-associated tumours which retain a profile of p53-dependent activities in terms of transactivation, growth suppression and apoptosis induction which is close or equal to wild-type. However, these mutants fail to suppress transformation and exhibit gain of function transforming activity in rat embryo fibroblasts. These mutants therefore fall into a novel category of p53 mutants which dissociate transformation suppression from other wild-type functions. The rarity of these mutants in human cancer and their multiple occurrence in BRCA-associated breast tumours suggests that these novel p53 mutants are selected during malignant progression in the unique genetic background of BRCA1- and BRCA2-associated tumours. (+info)
Moral concerns of different types of patients in clinical BRCA1/2 gene mutation testing.
(13/929)
PURPOSE: Implementing predictive genetic testing for a severe and common chronic disease such as breast cancer may raise unique ethical problems. Here we report on moral concerns experienced by patients in the setting of genetic counseling based on BRCA1/2 gene testing. PATIENTS AND METHODS: Patients were members of breast or breast/ovarian cancer families in a consecutive series of 100 families who received counseling at a familial cancer clinic. The patients' moral concerns were identified using the grounded theory approach in the qualitative analysis of verbal transcripts of 45 counseling sessions. Included were sessions with patients who had breast and ovarian cancer, as well as their male and female relatives, before and after the specific BRCA1/2 gene mutation was identified in the family, and before and after those who opted for mutation analysis were informed of their carrier status. RESULTS: There is an association of BRCA1/2 gene mutation carrier status and specific topics of moral concern. The moral preoccupations of patients with breast and ovarian cancer (probable carriers) related to their being instrumental in the detection of the specific mutation segregating in the family. The preoccupations of possible carriers concerned their own offspring. Individuals who tested positive (proven carriers) were concerned with issues of confidentiality. Patients who tested negative (proven noncarriers) were concerned with helping siblings and other relatives. CONCLUSION: Knowledge of the moral concerns of subjects in the study sample may help health care providers be aware of the moral concerns of their own patients. This report may also contribute to the debate on predictive testing for familial adult-onset diseases from the patient's perspective. (+info)
Risk factors for detecting germline BRCA1 and BRCA2 founder mutations in Ashkenazi Jewish women with breast or ovarian cancer.
(14/929)
We ascertained 184 Ashkenazi Jewish women with breast/ovarian cancer (171 breast and 13 ovarian cancers, two of the former also had ovarian cancer) in a self-referral study. They were tested for germline founder mutations in BRCA1 (185delAG, 5382insC, 188del11) and BRCA2 (6174delT). Personal/family histories were correlated with mutation status. Logistic regression was used to develop a model to predict those breast cancer cases likely to be germline BRCA1/BRCA2 mutation carriers in this population. The most important factors were age at diagnosis, personal/family history of ovarian cancer, or breast cancer diagnosed before 60 years in a first degree relative. A total of 15.8% of breast cancer cases, one of 13 ovarian cancer cases (7.7%), and both cases with ovarian and breast cancer carried one of the founder mutations. Age at diagnosis in carriers (44.6 years) was significantly lower than in non-carriers (52.1 years) (p<0.001), and was slightly lower in BRCA1 than BRCA2 carriers. Thirty three percent of carriers had no family history of breast or ovarian cancer in first or second degree relatives. Conversely, 12% of non-mutation carriers had strong family histories, with both a first and a second degree relative diagnosed with breast or ovarian cancer. The predicted values from the logistic model can be used to define criteria for identifying Ashkenazi Jewish women with breast cancer who are at high risk of carrying BRCA1 and BRCA2 mutations. The following criteria would identify those at approximately 10% risk: (1) breast cancer <50 years, (2) breast cancer <60 years with a first degree relative with breast cancer <60 years, or (3) breast cancer <70 years and a first or second degree relative with ovarian cancer. (+info)
Increased level of exon 12 alternatively spliced BRCA2 transcripts in tumor breast tissue compared with normal tissue.
(15/929)
The breast cancer susceptibility gene BRCA2 is expressed in a wide range of tissues as an 11-kb mRNA transcript encoding a 3418-amino acid protein, which is involved in the response to DNA damage. To obtain a better molecular characterization of BRCA2 expression in breast tissue, we analyzed full-length BRCA2 mRNA by means of reverse transcriptase-PCR with a panel of primer pairs encompassing the entire cDNA sequence. We report the identification of an exon 12 alternatively spliced BRCA2 transcript (delta12-BRCA2) in normal human breast tissue, in a wide variety of other normal human tissues, and in several mouse tissues. The deletion observed in this transcript (96 bp) preserves the open reading frame, and translation of the transcript would result in a BRCA2 isoform lacking 32 amino acids between codons 2280 and 2311. The analysis of matched normal and primary tumor breast tissues from 12 patients showed that the expression level of the delta12-BRCA2 transcript was higher in 4 of 12 (33%) tumor tissues compared with their normal breast tissues. Overproduction of the delta12-BRCA2 variant was associated with steroid receptor-negative tumors (P = 0.0005). These data suggest that the mechanisms generating the BRCA2 mRNA variant exist in normal breast tissue and may be dysregulated in steroid receptor-negative breast tumor tissues. (+info)
Reduced Fhit expression in sporadic and BRCA2-linked breast carcinomas.
(16/929)
Evidence for alteration of the FHIT gene in a significant fraction of breast carcinomas has been reported, in apparent concordance with loss of heterozygosity (LOH) at chromosome region 3p14.2 in breast cancer and benign proliferative breast disease. A significantly higher frequency of LOH at the FHIT locus was reported for BRCA2-/- tumors, possibly due to misrepaired double-strand breaks at this common fragile region. To determine whether such genomic alterations lead to Fhit inactivation, we have assessed the level of Fhit expression by immunohistochemical detection in sporadic tumors and cancers occurring in BRCA2 999del5 carriers. To determine whether Fhit inactivation may have prognostic significance, we have also assessed expression of breast cancer markers and clinical features in sporadic tumors relative to Fhit expression. Of 40 consecutive sporadic breast carcinomas studied for tumor markers, 50% showed reduced Fhit expression. In these sporadic cancers, loss of Fhit expression was not correlated significantly with the presence or absence of other tumor markers. In a study of 58 sporadic and 34 BRCA2 999del5 Icelandic invasive cancers, there was a significant association of LOH at 3p14.2 with reduced expression of Fhit (P = 0.001); also the lower expression of Fhit and higher LOH at 3p14.2 in BRCA2 999del5 tumors relative to sporadic cancers was significant (P = 0.002). Thus, genetic alteration at the fragile site within the FHIT gene leads to loss of Fhit protein in a significant fraction of sporadic breast cancers and a much larger fraction of familial breast cancers with an inherited BRCA2 mutation, consistent with the idea that loss of BRCA2 function affects stability of the FHIT/FRA3B locus. (+info)