BRCA1 and BRCA2 proteins are expressed in milk fat globules.
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BRCA1 Protein↗
Biomedical subjects
Y J Bignon
Publications and source records attributed to Y J Bignon.
Prolactin-dependent up-regulation of BRCA1 expression in human breast cancer cell lines.
We report experimental evidence that BRCA1, a breast and ovarian cancer susceptibility gene, is up-regulated in response to prolactin (PRL) stimulation. Expression of the BRCA1 gene was monitored in 2 human breast cancer cell lines (MCF-7 and T-47D) and in the normal mammary epithelial cell line MCF10a. Using competitive RT-PCR, we have shown that PRL induced an increase in BRCA1 mRNA level in MCF-7 and T-47D cell lines at a dose resulting in the maximal enhancement of cell proliferation. The up-regulation was 12-fold in MCF-7 cells and 2-fold in T-47D cells. No increase in BRCA1 mRNA level was observed in the MCF10a cell line. The level of BRCA1 protein was quantified using an affinity chromatography strategy. At the protein level, PRL treatment induced a 4-fold increase of BRCA1 protein expression in MCF-7 and a 6-fold increase in T-47D cells, whereas BRCA1 protein expression was not affected by PRL in MCF10a.
Base Sequence↗
Quantification of BRCA1 protein in sporadic breast carcinoma with or without loss of heterozygosity of the BRCA1 gene.
In sporadic breast cancer, no mutations of the BRCA1 gene have been reported so far, whereas BRCA1 mRNA is markedly decreased in invasive breast cancer. To elucidate the contribution of the BRCA1 gene in sporadic breast cancer, we quantified the BRCA1 protein, using [125I] labeling of whole-cell proteins, lentil-lectin affinity chromatography, immunoprecipitation by anti-BRCA1 antibodies (C-20, D-20, I-20 and K-18), purification of the immune complex by protein A affinity chromatography and chromato-focusing. As loss of 1 allele may lead to a decreased expression of the gene, 10 tumors were previously checked for loss of heterozygosity (LOH) of the BRCA1 gene, using 3 intragenic microsatellite markers. Our results indicated that the BRCA1 gene product was decreased in the 4 tumors with LOH compared with matched normal breast tissues. Reduced amounts of BRCA1 protein were also detected in 3 of 6 tumors without LOH. Our quantitative method allowed us to demonstrate that the BRCA1 protein level was decreased in sporadic invasive breast carcinomas with or without LOH of the BRCA1 gene, implying multiple mechanisms of BRCA1 expression down-regulation in these tumors. Our data suggest that the amount of BRCA1 protein present may play an important role in human sporadic breast carcinoma.
BRCA1 Protein↗
Isolation, purification and quantification of BRCA1 protein from tumour cells by affinity perfusion chromatography.
A new procedure for the isolation, purification and quantification of the product of the oncosuppressor gene brca1 in breast tissues, was carried out. It involves internal cell protein [35S]methionine labelling followed by two perfusion chromatographies. The first one is heparin affinity chromatography, to purify all of the cell DNA-binding proteins. A subsequent specific immunoprecipitation of BRCA1 protein was performed with an antibody raised against BRCA1. The immune complex was isolated using the second chromatographic step, Protein A affinity chromatography. The amount of BRCA1 expressed by cells was expressed as a ratio, in percent, calculated as follows: 100x amount of labelled DNA-binding proteins (dpm) that bound specifically to the anti-BRCA1 polyclonal antibodies (K-18)/amount of whole labelled DNA-binding protein (dpm) purified on a heparin column. Applications to MCF7 and T-47D human breast tumour cell lines, which were treated or not using 2 mM sodium butyrate demonstrated an increase in BRCA1 protein expression.
BRCA1 Protein↗
High incidence of cancer in a family segregating a mutation of the ATM gene: possible role of ATM heterozygosity in cancer.
ATM mutations predispose cells to malignancy by promoting chromosomal instability. We have identified a family with multiple cancers that segregates a mutant allele of ATM, IVS61+2insTA, which causes skipping of exon 61 in the mRNA, as well as a previously undescribed polymorphism, IVS61+104C(54):T(46). The mutation was inherited by two sisters, one who developed breast cancer at age 39 and the second at age 44, from their mother, who developed kidney cancer at age 67. Molecular studies were undertaken to determine the role of the ATM gene in the development of cancer in this family. Studies of irradiated lymphocytes from both sisters revealed elevated numbers of chromatid breaks, typical of A-T heterozygotes. Studies on lymphoblastoid cell lines established from these individuals revealed abnormal p53 induction and apoptosis after DNA damage. Loss of heterozygosity (LOH) in the ATM region of chromosome 11q23.1 showed that the normal ATM allele was lost in the breast tumor of the older sister. LOH was not seen at the BRCA1 or BRCA2 loci. BRCA2 is not likely to be a cancer-predisposing gene in this family because each sister inherited different chromosomes 13 from each parent. The sisters share their maternal BRCA1 allele, although no mutation in this gene was detected in the family. Our findings suggest that haploinsufficiency at ATM may promote tumorigenesis, even though LOH at the locus supports a more classic two-hit tumor suppressor gene model.
Adult↗
ATM heterozygote cells exhibit intermediate levels of apoptosis in response to streptonigrin and etoposide.
Ataxia-telangiectasia (A-T) is a rare recessive disease characterised by cerebellar ataxia, immunodeficiency, sensitivity to ionising radiation and increased cancer risk. Heterozygotes have an increased risk of cancer and may comprise 1% of the population. In vitro, A-T heterozygote cell lines show radiosensitivity intermediate between normal and A-T homozygotes. Furthermore, in A-T homozygotes, hypersensitivity to chemical agents which cause DNA damage, similar to that produced by ionising radiation, has been observed. To investigate the chemosensitivity of A-T heterozygote cell lines, we used TUNEL to analyse the level of apoptosis after drug treatment with etoposide and streptonigrin. Our samples included four normal, eight A-T heterozygote and 10 A-T homozygote lymphoblastoid cell lines. All cell lines were exposed to drugs for 24 h, then cultivated in fresh media for 0 and 72 h. The levels of apoptosis increased significantly in all cell lines, with the greatest increase in homozygote cells and an intermediate increase in heterozygote cells (P values of < 0.01 for etoposide treatment and < 0.02 for streptonigrin treatment were obtained using the Kruskal-Wallis H-test). Our results indicate that A-T heterozygotes express intermediate sensitivity to etoposide and streptonigrin similar to that observed in response to ionising radiation.
Antineoplastic Combined Chemotherapy Protocols↗
Allelotype influence at glutathione S-transferase M1 locus on breast cancer susceptibility.
The influence of polymorphisms of the glutathione S-transferase gene GSTM1 in breast cancer susceptibility has been assessed in this study. Previous studies correlated the absence of the GSTM1 protein with an increased risk of developing some cancers, especially lung or bladder cancers, in heavy smokers. In this study, we determined GSTM1 polymorphisms in a population of 437 female controls from the west of France and 361 community breast cancer patients. Three distinct alleles of this gene exist: GSTM1*A, GSTM1*B and GSTM1*0 (deleted allele). Null subjects (GSTM1 null) are homozygous for this deletion. The comparative analysis of GSTM1 allelotypes in our two populations did not demonstrate a statistically significant difference in distribution (P = 0.22), although the null genotype was more frequent in cancer patients. However, breast cancer risk was increased in null subjects > or = 50 years of age compared with non-null subjects [odds ratio = 1.99 (1.19-3.32), P = 0.009], but not in null subjects < 50 years of age compared with non-null subjects (P = 0.86). Our results suggest that the GSTM1 null genotype may play a role in post-menopausal breast cancer development. They also point to a putative protective role of the A allele in the older female control group, especially in hemizygous subjects [odds ratio = 0.42 (0.23-0.77), P = 0.03].
Adult↗
European multicenter study on LOH of APOC3 at 11q23 in 766 breast cancer patients: relation to clinical variables. Breast Cancer Somatic Genetics Consortium.
High frequencies of loss of heterozygosity (LOH) in chromosome 11q22-qter have been observed in various malignancies, including breast cancer. Previous studies on breast carcinomas by Winqvist et al (Cancer Res 55: 2660-2664) have indicated that a survival factor gene is located in band 11q23, and that the highly informative microsatellite polymorphism at the APOC3 locus would be a suitable tool to perform more extensive LOH studies. In this European multicentre study, we have examined the occurrence of APOC3 LOH and evaluated the effect of LOH of this chromosomal subregion on the clinical behaviour of the disease in a cohort of 766 breast cancer patients in more detail. LOH for APOC3 was found in 42% of the studied tumours, but it was not found to be significantly associated with any of the studied clinical variables, including cancer-specific survival time or survival time after recurrent/metastatic disease. According to the present findings, the putative survival factor gene on 11q23 is not located close enough to the APOC3 gene, but apparently at a more proximal location.
Adult↗
Screening for microdeletions on the long arm of chromosome Y in 53 infertile men.
About 30% of couple infertilities are of male origin. They appear in some cases de novo and are considered idiopathic. The aim of our work was to evaluate, in these cases, the prevalence of microdeletions of the long arm of chromosome Y, within the AZF a, b and c regions using molecular biology techniques. Men with azoospermia or oligozoospermia resulting from hereditary, endocrine or obstructive causes, or with a constitutional cytogenetic abnormality were excluded. Fifty-three infertile men with azoospermia or oligozoospermia, as determined by a spermiogram, were studied. Of these, 34 were idiopathic and 7 exhibited a past history of genital infection or biological abnormalities, suggesting partial obstruction of the genito-urinary tract. A further 8 men had a varicocele and 11 cases with a history of cryptorchidism were also studied. Peripheral blood DNA was extracted from each patient, then amplified by multiplex PCR with STS genomic markers from the three Y chromosome AZF zones. PCR products were then analysed on agarose gels. In view of the difficulty of confirming the absence of a signal in molecular biology, each case suspected of having a deletion was checked by multiplex PCR through coamplification with the SRY marker. Five men with microdeletions of the long arm of the Y chromosome were diagnosed among the 53 patients. All of them included the AZFc zone and the intragenic DAZ gene markers. Furthermore, a larger Y chromosome deletion encompassing the 3 AZF zones was diagnosed, and confirmed by cytogenetic analysis. All Y chromosome microdeletions were observed in the 34 truly idiopathic azoospermia/oligozoospermia cases, corresponding to a proportion of 14.7% (or 9.4% considering the whole population of 53 infertile men). The relatively high proportion of microdeletions found in our series suggests the need for strict patient selection to avoid unnecessary screening for long arm Y chromosome microdeletions.
Adult↗
Four years analysis of cancer genetic clinics activity in France from 1994 to 1997: a survey on 801 patients. French Cooperative Network/Groupe Génétique et Cancer de la Fédération Nationale des Centres de Lutte Contre le Cancer.
AIM: In order to evaluate the characteristics and the evolution of cancer genetics activity in France, a survey was conducted at the national level during a period of 4 years from 1994 to 1997 through the French Cooperative Network, a multidisciplinary group formed to investigate inherited tumors. METHOD: A questionnaire was sent to all the 29 French non-specialized cancer genetic clinics to evaluate activity during a period of 4 consecutive weeks each year from 1994 to 1997. Items concerning the cancer genetic clinics, the consultees and the types of consultation were explored. RESULTS: A total number of 801 consultees were seen during the period of analysis. Some prominent characteristics of patients attending cancer genetic clinics were found. The majority of these are women (88%), and the mean age of consultees is 48 years. Fifty five percent of consultees are affected with cancer, and breast (personal and/or family history) is the most frequent site involved (63%). A genetic predisposition is certain or likely in about 53% of cases and unlikely in only 13% of consultations. The majority of consultations are devoted to new families (71%). The mean duration of consultations is 50 minutes, but 40% have a duration of at least 1 hour. Variations of several parameters during the 4 years period were observed and analyzed. Finally, since duration of consultations (more or equal to 1 hour) and personal or family history of breast/ovarian cancer appeared as pivotal elements in our study and consequently may affect the organization of clinics and the structuring as well as the evolution of cancer genetic activity in France, we analyzed more precisely the factors significantly associated with these 2 elements. CONCLUSION: Study compliance was fair (60% of centers) and these results give a good measure of cancer genetic activity in France. The variation of parameters from one year to another may reflect modifications in medical practice (medical orientation rather than research focus and content of cancer genetic clinics) and/or scientific breakthroughs in cancer genetics such as identification of genes predisposing to cancer.
Adult↗
p16 involvement in primary bladder tumors: analysis of deletions and mutations.
Different studies have proposed that genetic alterations leading to inactivation of a tumor suppressor gene on chromosome 9 is an important early event in bladder tumorigenesis. Recent reports have described the p16 gene as the main target. In order to better define its role, we studied 9p21 deletions by microsatellite analysis and its coding sequence. Forty-eight percent of the 44 samples we studied showed LOH surrounding p16. Three of these 44 samples displayed point mutations in p16 and three others were suspected of homozygous deletion. These results suggest that simultaneous loss of both p16 alleles, by point mutation or homozygous deletion, seems to be infrequent in bladder tumors.
Chromosomes, Human, Pair 9↗
Subcellular localization of BRCA1 protein in sporadic breast carcinoma with or without allelic loss of BRCA1 gene.
The localization of BRCA1 protein was studied in 49 sporadic breast carcinomas for which allelic losses of BRCA1 have been investigated. One group consisted of 15 breast carcinomas having one allelic loss of BRCA1 and the other group of 34 breast carcinomas with no allelic loss of BRCA1. The localization of BRCA1 in the 2 groups was performed using polyclonal antibodies (K-18; C-20; D-20; I-20) raised against BRCA1 and by comparing frozen and paraffin-embedded tissues. We show that no correlation was found between the expression of BRCA1 protein and allelic loss of BRCA1. But, the nuclear detection of BRCA1 in frozen samples was improved when compared to paraffinized ones.
Antibodies↗
Systematic sequencing of the BRCA-1 coding region for germ-line mutation detection in 70 French high-risk families.
Seventy French high-risk families were screened for germ-line BRCA-1 mutations. The BRCA-1 coding region and the exon-intron boundaries were sequenced, except when pre-screening by PTT revealed a truncated protein in exon 11. Germ-line BRCA-1 mutations were detected in 24% of families. The number of breast and ovarian cancers per family, a relative young age at ovarian cancer diagnosis, and the occurrence of breast and ovarian cancer in the same patient significantly predicted the presence of a BRCA-1 mutation. The low BRCA-1 mutation frequency suggested that some alterations were not detected and some families were probably BRCA-2 or BRCAx carriers.
Adult↗
Giant cell tumor of the sternum. Report of a case with a 17q isochromosome.
We report a case of giant cell tumor of the manubrium with radiological evidence of aggressiveness. Few cases of giant cell tumor of the sternum have been published. Extensive surgery offers the best hopes of recovery. Cytogenetic studies evidenced several clonal abnormalities including a 17q isochromosome. The TP53 suppressor gene is located at 17q13.1. Whether loss of one of the TP53 alleles may have contributed to the aggressive behavior of our patient's tumor is discussed.
Bone Neoplasms↗
[Mutation by deletion-insertion in BRCA-1 gene in three unrelated French breast/ovarian cancer families: possible implication of a mobile element].
A new type of mutation by deletion-insertion in BRCA-1 gene is found in three unrelated French breast/ovarian cancer families. Surprisingly, deletion and insertion occurred at the same nucleotide position at the end of exon 11 (3958del5ins4), thus generating a truncated protein. This original mutation consists in a deletion of 5 bp (CTCAG) and in an insertion of 4 different bp (AGGC). Here, we proposed two hypothesis to explain this phenomenom. The first hypothesis is the formation of a hairpin stem-loop structure comprising the mutational site and the sequence corresponding to the duplication insertion 2 nucleotides before the mutation. The second hypothesis, more speculative, consists in an abortive integration of a human mobile element as a human transposon (tigger 1) which involved a deletion of 5 bp during its excision and an insertion of 4 bases corresponding to the 5' extremity of the transposon.
Adult↗
Linkage analysis of 56 multiplex families excludes the Cowden disease gene PTEN as a major contributor to familial breast cancer.
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Breast Neoplasms↗
Marker segregation information in breast/ovarian cancer genetic counseling: is it still useful? Groupe Génétique et Cancer de la Fédération Nationale des Centres de Lutte Contre le Cancer.
The use of mutation screening of BRCA1 and BRCA2 genes as a genetic test is still to a certain extent limited and the oncogeneticist may want to use complementary approaches to identify at-risk individuals. In a series of 23 families with at least three breast or ovarian cancer cases, screened for mutations at BRCA1 and BRCA2 and typed for markers at both loci, we investigated the usefulness of marker segregation information at two levels: 1) to what extent can the indirect approach identify the mutation carrier status of screened cases and their first-degree relatives, and 2) in what way does it help to identify the gene implicated in a family in which neither BRCA1 nor BRCA2 mutation has been detected? Using the indirect approach, the carrier status of the screened case could be determined with quasi certainty in three families and with a high probability in eight families. This status could be inferred in unaffected first-degree relatives as almost certain in one family and as highly probable in six families. Fourteen mutations were found concurrently in our series. Among the nine mutation-negative families, we were able to conclude that a BRCA1 mutation most probably segregated in one and that a mutation other than BRCA1 and BRCA2 was probably involved in two families. Our results show that, in small families, little help is to be expected from linkage data and mutation screening is the only way of identifying the origin of a genetic predisposition in a family. Marker segregation information may be useful in some large breast/ovarian cancer families in which no BRCA1 or BRCA2 mutation has been detected.
BRCA1 Protein↗
Human bladder cancers and normal bladder mucosa present the same hot spot of heterozygous chromosome-9 deletion.
Loss of heterozygosity (LOH) on chromosome 9 is the most frequent genetic alteration in bladder cancer identified to date, suggesting the presence of key gene(s) for this pathology. In this study, we examined 44 bladder tumors and 21 normal bladder samples for LOH on both arms of chromosome 9. Sixteen microsatellite markers, 12 on the short arm (encompassing 9p21-22) and 4 on the long arm (encompassing 9q33-34), were chosen for their highly frequent alterations in bladder cancer. LOH for at least one marker was identified in 42 tumor samples (95.5%), and 14 tumors (32%) displayed LOH for all informative tested markers. Detailed analysis showed that 2 markers on chromosome 9p (D9S157 and D9S156) had the highest frequencies of allelic loss (about 70%), independent of tumor grade and stage. The same study was performed on the 21 normal bladder mucosa samples: 50% of informative cases presented a single specific LOH at the D9S156 locus. Normal samples showing LOH at this locus were therefore screened with 3 novel microsatellite markers in the 810-kb region incorporating D9S156. Using this marker, we found no further heterozygous loss in this region. This result allows different interpretations of the D9S156 loss in normal bladder mucosa, and suggests that D9S156 may be more an indicator of bladder epithelium impairment than a tumor-initiation marker. Similarly, this unexpected result calls in question the interpretation of LOH studies.
Aged↗