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Alvaro N A Monteiro

Publications and source records attributed to Alvaro N A Monteiro.

At least 19 recordsLinked to original sources
PubMed2026

Updated ENIGMA recommendations for reporting germline variants in cancer susceptibility genes and their translation into twenty languages.

Genetic testing for cancer susceptibility underpins precision cancer prevention and care. Gaps in the healthcare providers' genetic literacy and an ambiguous lexicon for variant description may hinder proper delivery and clinical application of consistently trustworthy test results. The Evidence-based Network for the Interpretation of Germline Mutant Alleles (ENIGMA) international consortium supports controlled terminology and recommends a framework for reporting germline variants in cancer susceptibility genes, using breast cancer as an exemplar. Moving forward towards terminological coherence across disciplines and borders, the ENIGMA Clinical Working Group launched a multinational effort to release consortium-approved translations of the published recommendations. The herein reported Vocabulary Translation Project offered an opportunity to reappraise and align the reference text to the recent BRCA1 and BRCA2 specifications to the American College of Medical Genetics and Genomics/Association for Molecular Pathology rules by the ENIGMA Variant Curation Expert Panel and to highlight country-specific differences in breast cancer risk assessment and management. The updated recommendations and their 20 translations are now provided as easy to handle documents, covering 11 of the most widely spoken languages in the world. They will contribute to minimised erroneous inferences, more informed decision-making, improved health outcomes and equity in the use of genetic testing for cancer predisposition and in translational oncology.

Humans↗
PubMed2006

Prevalence of BRCA1 and BRCA2 mutations in breast cancer patients from Brazil.

The contribution of BRCA1 and BRCA2 to breast cancer incidence in Brazil has not yet been explored. In order to estimate the proportion of breast cancers due to BRCA1 and BRCA2 mutations in Brazil, we conducted a study of unselected breast cancer patients from Rio de Janeiro, Brazil. We enrolled 402 women with breast cancer from a large public hospital and two private medical clinics in the city. A detailed family history was obtained from each patient and a blood sample was obtained for DNA analysis. Mutations in BRCA1 and BRCA2 were sought using a combination of techniques, but all mutations were confirmed by direct sequencing. Overall, nine mutations were identified (six in BRCA1 and three in BRCA2) representing 2.3% of the total. The most common mutation, 5382insC in BRCA1, was seen five times and accounted for 56% of all identified mutations. A second mutation, in BRCA2 (6633del5) was seen in two unrelated women. In summary, BRCA1 and BRCA2 mutations are not uncommon in Brazilian women with breast cancer. It appears that a small number of founder mutations may be predominant. Moreover, a small number of founder mutations may be prevalent in Brazil, raising the possibility that a rapid and inexpensive genetic test may be developed to screen for inherited susceptibility to breast cancer in Brazil.

Adult↗
PubMed2006

Functional assays for BRCA1 and BRCA2.

Genetic testing for the two major breast cancer susceptibility genes has now been available for several years with more than 70,000 people tested in the USA alone. While the current genetic testing identifies many sequence alterations there are problems with both sensitivity and specificity of the assay. In particular, the genetic testing is limited in its ability to determine which of the many missense mutations identified in BRCA1 and BRCA2 actually predispose to cancer and which are simply neutral alterations. Here we will focus on the limitations in test result interpretation and we will explore how biochemistry and cell biology can help to clarify these issues. Although we limit our discussion to genetic testing of BRCA1 and BRCA2, the problem is common to an expanding group of genes, including ATM and MSH2, in which germ-line missense mutations may also confer increased risk of cancer. Here we advocate the use of functional assays to complement genetic data in the analysis of unclassified missense mutations and propose a set of standards to conduct and interpret these assays.

BRCA1 Protein↗
PubMed2006

Long-term culture of cholangiocytes from liver fibro-granulomatous lesions.

BACKGROUND: Extensive bile duct proliferation is a key feature of the tissue reaction to clinical and experimental forms of liver injury. Experimental infection of mice by Schistosoma mansoni is a well-studied model of liver fibrosis with bile duct hyperplasia. However, the regulatory mechanisms of bile duct changes are not well understood. In this study we report the reproducible isolation of long-term cultures of cholangiocytes from mice livers with schistosomal fibrosis. METHODS: We have isolated a cholangiocyte cell line from Schistosoma-induced liver granulomas using a combination of methods including selective adhesion and isopyknic centrifugation in Percoll. RESULTS: The cell line was characterized by morphological criteria in optical and transmission electron microscopy, ability to form well differentiated ductular structures in collagen gels and by a positive staining for cytokeratin 18 and cytokeratin 19. To our knowledge, this is the first murine cholangiocyte cell line isolated from schistosomal fibrosis reported in the literature. CONCLUSION: After 9 months and 16 passages this diploid cell line maintained differentiated characteristics and a high proliferative capacity. We believe the method described here may be a valuable tool to study bile duct changes during hepatic injury.

Animals↗
PubMed2006

DNA damage response: determining the fate of phosphorylated histone H2AX.

Phosphorylation of histone H2AX at Serine 139 is one of the earliest events after DNA damage and is required for the retention of factors involved in repair at the site of the break. Intriguingly, H2AX phosphorylation spreads from the vicinity of the break to both directions spanning large chromosomal regions. Phosphorylated H2AX (also known as gamma-H2AX) then progressively disappears with kinetics that correlates with the completion of DNA repair. Despite intense investigation on the kinases and stimuli involved in gamma-H2AX formation, the mechanism of gamma-H2AX disappearance has remained obscure. Three recent papers shed light on this process and suggest that H2AX may serve as a signaling platform that integrates repair and cell cycle checkpoints.

Animals↗
PubMed2006

Cancer risk assessment at the atomic level.

A flurry of articles on the structure of different domains of BRCA1 and BRCA2 have not only shed light on the biology of these proteins but have also raised hopes that these data could eventually be used to infer cancer association for a large number of inherited missense mutations whose effect on protein function is unclear.

BRCA1 Protein↗
PubMed2006

Functional implications of BRCA1 for early detection, prevention, and treatment of breast cancer.

The tumor suppressor gene BRCA1 was positionally cloned in 1994. During the last 12 years, several lines of evidence have implicated BRCA1 in the maintenance of genome integrity, regulation of transcriptionn, and chromatin remodeling, suggesting that it has multiple biological roles. Germline mutations in BRCA1 confer a 56%-80% lifetime risk for breast cancer and a 15%-60% lifetime risk for ovarian cancer in women. And preliminary evidence suggests that BRCA1-linked breast and ovarian tumors behave differently from sporadic tumors, justifying a tailored approach to these cancers. Although several gaps still remain in our knowledge, it is possible to use information from basic research to illuminate clinical decisions and improve the prospects of mutation carriers. Along similar lines, genetic data derived from the clinical setting are also instrumental in determining which biochemical functions of BRCA1 contribute to its tumor suppressor actions. In this article, we explore the functional implications of BRCA1 for genetic testing (early detection), prevention, and therapy.

BRCA1 Protein↗
PubMed2004

BRCA1 in breast and ovarian cancer predisposition.

Women carrying one mutated BRCA1 allele are at increased risk of developing breast and ovarian cancer but tumor initiation requires the loss of the wild-type allele indicating that it is a tumor suppressor gene. In the 10 years since the cloning of BRCA1, a function for the gene product in the DNA damage response has been established. However, identifying the exact biochemical activities of BRCA1 has been a more difficult task. Our current understanding suggests that the molecular functions mediated by the terminal ends of BRCA1, which include an E3 ubiquitin ligase activity at the N-terminus and a protein-protein interaction surface at the C-terminus, are critical to the function of this protein in the response to DNA damage.

BRCA1 Protein↗
PubMed2004

TGF beta1 and PDGF AA override collagen type I inhibition of proliferation in human liver connective tissue cells.

BACKGROUND: A marked expansion of the connective tissue population and an abnormal deposition of extracellular matrix proteins are hallmarks of chronic and acute injuries to liver tissue. Liver connective tissue cells, also called stellate cells, derived from fibrotic liver have been thoroughly characterized and correspond phenotypically to myofibroblasts. They are thought to derive from fat-storing Ito cells in the perisinusoidal space and acquire a contractile phenotype when activated by tissue injury. In the last few years it has become evident that several peptide growth factors such as PDGF AA and TGF-beta are involved in the development of fibrosis by modulating myofibroblast proliferation and collagen secretion. The fact that during the development of chronic fibrosis there is concomitant deposition of collagen, a known inhibitory factor, and sustained cell proliferation, raises the possibility that stellate cells from chronic liver fibrosis patients fail to respond to normal physiologic controls. METHODS: In this study we address whether cells from fibrotic liver patients respond to normal controls of proliferation. We compared cell proliferation of primary human liver connective tissue cells (LCTC) from patients with liver fibrosis and skin fibroblasts (SF) in the presence of collagens type I and IV; TGF-beta, PDGF AA and combinations of collagen type I and TGF-beta or PDGF AA. RESULTS: Our results indicate that despite displaying normal contact and collagen-induced inhibition of proliferation LCTC respond more vigorously to lower concentrations of PDGF AA. In addition, we show that collagen type I synergizes with growth factors to promote mitogenesis of LCTC but not SF. CONCLUSIONS: The synergistic interaction of growth factors and extracellular matrix proteins may underlie the development of chronic liver fibrosis.

Cell Line↗
PubMed2004

Integrated evaluation of DNA sequence variants of unknown clinical significance: application to BRCA1 and BRCA2.

Many sequence variants in predisposition genes are of uncertain clinical significance, and classification of these variants into high- or low-risk categories is an important problem in clinical genetics. Classification of such variants can be performed by direct epidemiological observations, including cosegregation with disease in families and degree of family history of the disease, or by indirect measures, including amino acid conservation, severity of amino acid change, and evidence from functional assays. In this study, we have developed an approach to the synthesis of such evidence in a multifactorial likelihood-ratio model. We applied this model to the analysis of three unclassified variants in BRCA1 and three in BRCA2. The evidence strongly suggests that two variants (C1787S in BRCA1 and D2723H in BRCA2) are deleterious, three (R841W in BRCA1 and Y42C and P655R in BRCA2) are neutral, and one (R1699Q in BRCA1) remains of uncertain significance. These results provide a demonstration of the utility of the model.

Base Sequence↗
PubMed2004

Structure-based assessment of missense mutations in human BRCA1: implications for breast and ovarian cancer predisposition.

The BRCA1 gene from individuals at risk of breast and ovarian cancers can be screened for the presence of mutations. However, the cancer association of most alleles carrying missense mutations is unknown, thus creating significant problems for genetic counseling. To increase our ability to identify cancer-associated mutations in BRCA1, we set out to use the principles of protein three-dimensional structure as well as the correlation between the cancer-associated mutations and those that abolish transcriptional activation. Thirty-one of 37 missense mutations of known impact on the transcriptional activation function of BRCA1 are readily rationalized in structural terms. Loss-of-function mutations involve nonconservative changes in the core of the BRCA1 C-terminus (BRCT) fold or are localized in a groove that presumably forms a binding site involved in the transcriptional activation by BRCA1; mutations that do not abolish transcriptional activation are either conservative changes in the core or are on the surface outside of the putative binding site. Next, structure-based rules for predicting functional consequences of a given missense mutation were applied to 57 germ-line BRCA1 variants of unknown cancer association. Such a structure-based approach may be helpful in an integrated effort to identify mutations that predispose individuals to cancer.

BRCA1 Protein↗
PubMed2004

Understanding germ-line mutations in BRCA1.

Germ-line mutations in BRCA1 account for the majority of familial breast and ovarian cancer cases and development of cancer in individuals who carry such mutations requires somatic inactivation of the normal allele. BRCA1 is highly polymorphic with more than 1,200 distinct documented variants. Approximately 70% of reported variants lead to absence of full-length BRCA1 protein, through loss of expression or protein truncation, and are suspected to predispose to cancer. These include regulatory mutations, splice site alterations, large rearrangements, large and small deletions or insertions, and nonsense mutations. However, characterizing the remaining missense alterations as either deleterious (cancer-associated mutations) or neutral variants is more complex, as the functional significance of the respective amino acid substitution is not straightforward to evaluate. In addition, many missense variants have been identified only once in defined ethnic groups and represent alleles with very low frequency. Most often, little information is available about segregation of the variant with disease in families, and assessment of disease risk for low frequency alleles through association studies is problematic, requiring a large number of samples stratified and matched by ethnicity. The fact that a significant proportion of BRCA1 variants remain unclassified represents a gap in risk assessment, such that individuals undergoing genetic testing will receive noninformative test results. An approach for assessing the potential clinical significance of missense variants is to combine available genetic data with functional and structural studies. Here we review the available information on BRCA1 variants and explore ways in which we can analyze unclassified variants.

BRCA1 Protein↗
PubMed2004

Cancer variation associated with the position of the mutation in the BRCA2 gene.

Inherited mutations of the BRCA2 gene give rise to a multi-site cancer phenotype which includes breast cancer (in female and males), ovarian, pancreatic and prostate cancer, ocular and other melanomas, laryngeal, colon and stomach cancers. Interpretation of test results and risk assessment is therefore complex. It has been proposed that families with mutations in the ovarian cancer cluster region (OCCR) of exon 11 (nucleotides 3035-6629) express a higher ratio of ovarian to breast cancer, than families with mutations elsewhere in the BRCA2 gene. In this study we have investigated the presence of 7 types of cancer (ovary, male breast, pancreas, prostate, colon, stomach and melanoma) in first- and second-degree relatives of mutation-positive individuals in 440 families with a BRCA2 mutation. We reviewed histories of cancer in relatives among families with mutations distributed throughout the gene. Families with ovarian cancer were more likely to harbour mutations in the OCCR (nucleotides 3035-6629) than elsewhere in the gene (OR = 2.21; P = 0.0002). We also compared cancer risks according to ethnic group. Ashkenazi Jewish families with the 6174delT founder mutation were more likely to have a family member with ovarian cancer (OR = 1.58; P = 0.002) and less likely to have a family member with prostate cancer (OR = 0.62; P = 0.04) than were non-Jewish families. In contrast, a reduced presence of ovarian cancer was found in families of French-Canadian ancestry, compared to other ancestries (OR = 0.37; P = 0.0026). A high risk of male breast cancer was observed with the 6503delTT mutation (OR = 15.7; P = 0.023). Families of Polish ancestry had a reduced frequency of pancreatic cancer (OR = 0.0; P = 0.03) compared to families of other ethnic origins. In conclusion, both the position of mutation and the ethnic background of the family appear to contribute to the phenotypic variation observed in families with BRCA2 mutations.

BRCA2 Protein↗
PubMed2003

BRCA1: the enigma of tissue-specific tumor development.

Recent evidence indicates that BRCA1, a gene product associated with breast and ovarian cancer susceptibility, is an important component of the cellular response to DNA damage. Despite being expressed ubiquitously in adult tissues, germline mutations in BRCA1 predispose individuals to breast and ovarian tumors with only minor effects on the predisposition to cancer in other sites. The reason for this tissue specificity of BRCA1 carcinomas must be found if we are to understand fully why these tumors occur and to enable us to design efficient preventive and therapeutic regimens. Here I propose that tissue-specific rates of loss of heterozygosity in the BRCA1 locus could contribute to tissue specificity in tumor development.

BRCA1 Protein↗
PubMedDate not supplied

A naturally occurring allele of BRCA1 coding for a temperature-sensitive mutant protein.

Recent evidence suggests that the breast and ovarian cancer susceptibility gene product BRCA1 is involved in at least two fundamental cellular processes: transcriptional regulation and DNA repair. However, the mechanism of action of BRCA1 in either of these processes is still unknown. Here, we report the characterization of a disease-predisposing allele of BRCA1, identified in a family with several cases of ovarian cancer, coding for a protein that displays temperature-sensitive activity in transcriptional activation. The mutant protein differs from the wild type protein at a single amino acid, R1699W that occurs in a region at the N-terminal BRCT domain that is highly conserved among BRCA1 homologs. When the C-terminus of the mutant protein (aa 1560-1863) was fused to a heterologous GAL4 DNA-binding domain and expressed in yeast or mammalian cells, it was able to activate transcription of a reporter gene to levels observed for wild type BRCA1 at the permissive temperature (30 degrees C) but exhibited significantly less transcription activity at the restrictive temperature (37 degrees C or 39 degrees C). Our results indicate that the transcriptional activity of the R1699W mutant can be modulated as a function of temperature and provide a novel experimental approach which can be utilized to dissect the molecular mechanism(s) of BRCA1 in processes related to transcription.

Alleles↗
PubMedDate not supplied

Mutations in the BRCT domain confer temperature sensitivity to BRCA1 in transcription activation.

BRCA1 is a tumor suppressor gene and germ line mutations account for the majority of familial cases of breast and ovarian cancer. There is mounting evidence that BRCA1 functions in DNA repair and transcriptional regulation. A major hurdle to dissect the role of BRCA1 is the lack of molecular reagents to carry out biochemical and genetic experiments. Therefore, we used random mutagenesis of the C-terminus of BRCA1 (aa 1560-1863) to generate temperature-sensitive (TS) mutants in transcription activation. We obtained 11 TS mutants in transcription that localized primarily to the hydrophobic core of the BRCT-N domain of BRCA1. One of the mutants, H1686Q, also displayed temperature-dependent transcription activation in human cells. These conditional mutants represent valuable tools to assess the role of BRCA1 in transcription activation.

Amino Acid Sequence↗