Branca Maria Cavaco

University of Lisbon, Lisboa, Lisbon, Portugal

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Publications (43)216.42 Total impact

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    ABSTRACT: Activating germline mutations in the RET proto-oncogene are responsible for about 98 % of the familial forms of medullary thyroid carcinoma (MTC), which represent 25 % of all MTC cases. The search for germline mutations in this gene is important for the recognition of hereditary forms of MTC and further identification of at-risk relatives who may benefit from early clinical intervention. Genotype-phenotype correlations are well established for most disease-causing RET mutations, allowing risk stratification. The association of a new RET variant with the MTC phenotype and familial predisposition requires the assessment of its functional and clinical significance. The aim of this study was to evaluate the oncogenic potential of two newly identified RET germline variants associated with late-onset MTC. In vitro functional assays were designed to address the transforming potential of novel RET variants, through their expression in non-transformed cells, and comparing their effect with wild-type RET. The new variants were identified in codons 515 (p.C515W) and 636 (p.T636M) located, respectively, in exons 8 and 11, thus resulting in amino acid substitutions in the extracellular region of the tyrosine kinase receptor RET. Through functional assays, we observed increased cell growth and proliferation, loss of contact inhibition, and a stimulation of cell migration, suggesting that these new RET variants hold some relevant transforming potential. The transforming potential of these novel RET variants was of low-grade, when compared to that of RET MEN2A-causing mutation p.C634R, probably explaining the mild phenotype characterized by late onset and low clinical aggressiveness.
    Endocrine 03/2015; 49(2). DOI:10.1007/s12020-015-0559-0
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    ABSTRACT: Activating germline mutations in the RET proto-oncogene are responsible for about 98 % of the familial forms of medullary thyroid carcinoma (MTC), which represent 25 % of all MTC cases. The search for germline mutations in this gene is important for the recognition of hereditary forms of MTC and further identification of at-risk relatives who may benefit from early clinical intervention. Genotype-phenotype correlations are well established for most disease-causing RET mutations, allowing risk stratification. The association of a new RET variant with the MTC phenotype and familial predisposition requires the assessment of its functional and clinical significance. The aim of this study was to evaluate the oncogenic potential of two newly identified RET germline variants associated with late-onset MTC. In vitro functional assays were designed to address the transforming potential of novel RET variants, through their expression in non-transformed cells, and comparing their effect with wild-type RET. The new variants were identified in codons 515 (p.C515W) and 636 (p.T636M) located, respectively, in exons 8 and 11, thus resulting in amino acid substitutions in the extracellular region of the tyrosine kinase receptor RET. Through functional assays, we observed increased cell growth and proliferation, loss of contact inhibition, and a stimulation of cell migration, suggesting that these new RET variants hold some relevant transforming potential. The transforming potential of these novel RET variants was of low-grade, when compared to that of RET MEN2A-causing mutation p.C634R, probably explaining the mild phenotype characterized by late onset and low clinical aggressiveness.
    Endocrine 03/2015;
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    ABSTRACT: Context: Cell division cycle 73 (CDC73), encoding the protein parafibromin, is the most prevalent mutated gene in familial and sporadic parathyroid carcinoma (PC). Objective: Identify additional genetic abnormalities in PCs Design: Whole-exome sequencing was performed using DNA from seven pairs of matched PCs and one triplet containing double primary tumour and normal leukocyte. Somatic variants were confirmed using Sanger sequencing and recurrently mutated genes were assessed in 13 additional PCs as well as 40 parathyroid adenomas (PA). Results: PC had an average of 51 somatic variants/tumour (range 3 -176) with approximately 58% of variants occurring as non-synonymous single nucleotide variants. The importance of CDC73 in PC is reinforced with a remarkable preferential amplification of mutant CDC73 allele. Furthermore recurrent germ line and somatic mutations in prune homolog 2 [Drosophila] (PRUNE2) were found in PC and computationally predicted to be deleterious; in addition, recurrent mutations in kinase genes related to cell migration and invasion were found. PRUNE2 showed recurrent mutations in 18% (4/22) of PCs with additional screening in 40 PAs revealing only one rare missense polymorphism (Asp1677Asn). For the first time, the mutational signature associated with apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like (APOBEC)-catalyzed cytosine-to-uracil deamination is found in a subset of PC. Conclusion: This study outlines the genetic landscape of PC and attempts to characterize the mutational processes shaping the PC genome.
    Journal of Clinical Endocrinology &amp Metabolism 11/2014; 100(2):jc20143238. DOI:10.1210/jc.2014-3238
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    ABSTRACT: The familial forms of non-medullary thyroid carcinoma (FNMTC) represent approximately 5 % of thyroid neoplasms. Nine FNMTC susceptibility loci have been mapped; however, only the DICER1 and SRGAP1 susceptibility genes have been identified. The transcription factors NKX2-1, FOXE1, PAX8, and HHEX are involved in the morphogenesis and differentiation of the thyroid. Recent studies have identified NKX2-1 germline mutations in FNMTC families. However, the role of high-penetrant FOXE1 variants in FNMTC etiology remains unclear. The aim of this study was to investigate the role of FOXE1 germline mutations in the pathogenesis of FNMTC. We searched for molecular changes in the FOXE1 gene in the probands from 60 Portuguese families with FNMTC. In this series, we identified nine polymorphisms and one variant (c.743C>G, p.A248G) which was not previously described. This variant, which involved an amino acid residue conserved in evolution, segregated with disease in one family, and was also detected in an apparently unrelated case of sporadic NMTC. Functional studies were performed using rat normal thyroid cells (PCCL3) clones and human papillary thyroid carcinoma cell line (TPC-1) pools, expressing the wild type and mutant (p.A248G) forms of FOXE1. In these experiments, we observed that the p.A248G variant promoted cell proliferation and migration, suggesting that it may be involved in thyroid tumorigenesis. Additionally, somatic p.V600E BRAF mutations were also detected in the thyroid tumors of two members of the family carrying the p.A248G variant. This study represents the first evidence of involvement of a germline FOXE1 rare variant in FNMTC etiology and suggests that mutations in MAPK pathway-related genes may contribute to tumor development in these familial cases.
    Endocrine 11/2014;
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    ABSTRACT: The familial forms of non-medullary thyroid carcinoma (FNMTC) represent approximately 5 % of thyroid neoplasms. Nine FNMTC susceptibility loci have been mapped; however, only the DICER1 and SRGAP1 susceptibility genes have been identified. The transcription factors NKX2-1, FOXE1, PAX8, and HHEX are involved in the morphogenesis and differentiation of the thyroid. Recent studies have identified NKX2-1 germline mutations in FNMTC families. However, the role of high-penetrant FOXE1 variants in FNMTC etiology remains unclear. The aim of this study was to investigate the role of FOXE1 germline mutations in the pathogenesis of FNMTC. We searched for molecular changes in the FOXE1 gene in the probands from 60 Portuguese families with FNMTC. In this series, we identified nine polymorphisms and one variant (c.743C>G, p.A248G) which was not previously described. This variant, which involved an amino acid residue conserved in evolution, segregated with disease in one family, and was also detected in an apparently unrelated case of sporadic NMTC. Functional studies were performed using rat normal thyroid cells (PCCL3) clones and human papillary thyroid carcinoma cell line (TPC-1) pools, expressing the wild type and mutant (p.A248G) forms of FOXE1. In these experiments, we observed that the p.A248G variant promoted cell proliferation and migration, suggesting that it may be involved in thyroid tumorigenesis. Additionally, somatic p.V600E BRAF mutations were also detected in the thyroid tumors of two members of the family carrying the p.A248G variant. This study represents the first evidence of involvement of a germline FOXE1 rare variant in FNMTC etiology and suggests that mutations in MAPK pathway-related genes may contribute to tumor development in these familial cases.
    Endocrine 11/2014; 49(1). DOI:10.1007/s12020-014-0470-0
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    ABSTRACT: Introduction: Hypoparathyroidism is an entity associated with hypocalcemia, more frequently a consequence of neck surgery. An autoimmune etiology is rare and its diagnosis difficult to establish. Clinical report: 52 year-old woman, with irrelevant past medical history and no significant familial conditions, referred because of hypocalcemia and basal ganglia calcifications, detected in the course of investigation of myalgias. Besides hypocalcemia (4.6 mg/ dL), hyperphosphatemia (8.7 mg/dL), undetectable parathyroid hormone and low urinary calcium, phosphorus and magnesium were present. Molecular analysis of CaSR gene excluded germinal mutations. Anti-calcium sensing receptor antibodies (anti-CaSR) were present. The patient is asymptomatic and normocalcemic under treatment with calcium and vitamin D. Discussion: Although rare, hypocalcemia due to anti-CaSR hypoparathyroidism must be considered in the absence of previous neck surgery, hypocalcemic drugs, familial history or phenotype suggesting a genetic disorder. Low or undetectable parathyroid hormone excludes pseudohypoparathyroidism and anti-CaSR positivity establishes the diagnosis.
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    ABSTRACT: Context: Telomerase promoter mutations (TERT) were recently described in follicular cell-derived thyroid carcinomas (FCDTC) and seem to be more prevalent in aggressive cancers. Objectives: We aimed to evaluate the frequency of TERT promoter mutations in thyroid lesions and to investigate the prognostic significance of such mutations in a large cohort of patients with differentiated thyroid carcinomas (DTC). Design: Retrospective observational study. Setting and patients: We studied 647 tumors and tumor-like lesions. A total of 469 patients with FCDTC treated and followed in five University Hospitals were included. Mean follow-up (±SD) was 7.8±5.8 years. Main outcome measures: Predictive value of TERT promoter mutations for distant metastasization, disease persistence at the end of follow-up and disease-specific mortality. Results: TERT promoter mutations were found in 7.5% of papillary carcinomas (PTC), 17.1% of follicular carcinomas (FTC), 29.0% of poorly differentiated carcinomas and 33.3% of anaplastic thyroid carcinomas. Patients with TERT-mutated tumors were older (p<0.001) and had larger tumors (p=0.002). In DTC, TERT promoter mutations were significantly associated with distant metastases (p<0.001) and higher stage (p<0.001). Patients with DTC harboring TERT promoter mutations were submitted to more radioiodine treatments (p=0.009) with higher cumulative dose (p=0.004), and to more treatment modalities (p=0.001). At the end of follow-up, patients with TERT-mutated DTC were more prone to have persistent disease (p=0.001). TERT promoter mutations were significantly associated with disease-specific mortality [in the whole FCDTC (p<0.001)] in DTC (p<0.001), in PTC (p=0.001) and in FTC (p<0.001). After adjusting for age at diagnosis and gender, the HR was 10.35 (95%CI 2.01-53.24; p=0.005) in DTC and 23.81 (95%CI 1.36-415.76; p=0.03) in PTC. Conclusions: TERT promoter mutations are an indicator of clinically aggressive tumors, being correlated with worse outcome and disease-specific mortality in DTC. TERT promoter mutations have an independent prognostic value in DTC and, notably, in PTC.
    The Journal of Clinical Endocrinology and Metabolism 01/2014; 99(5):jc20133734. DOI:10.1210/jc.2013-3734
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    ABSTRACT: Background: Anaplastic thyroid carcinomas (ATC) are among the most lethal malignancies, for which there is no effective treatment. Objective: In the present study, we aimed to elucidate the molecular alterations contributing to ATC development, and to identify novel therapeutic targets. Design: We profiled the global gene expression of 5 ATC, and validated differentially expressed genes by quantitative RT-PCR in an independent set of tumors. In a series of 26 ATC, we searched for pathogenic alterations in genes involved in the most deregulated cellular processes, including the hot-spot regions of RAS, BRAF, TP53, CTNNB1 (β-catenin) and PIK3CA genes, and, for the first time, a comprehensive analysis of components involved in cell cycle [CDK inhibitors (CDKI): CDKN1A (p21(CIP1)); CDKN1B (p27(KIP1)); CDKN2A (p14(ARF), p16(INK4A)); CDKN2B (p15(INK4B)); CDKN2C (p18(INK4C))], cell adhesion (AXIN1) and proliferation (PTEN). Mutational analysis was also performed in 22 poorly differentiated thyroid carcinomas (PDTC). Results: Expression profiling revealed that ATC were characterized by under-expression of epithelial components, upregulation of mesenchymal markers and genes from TGF-β pathway, as well as, over-expression of cell cycle-related genes. In accordance, upregulation of the SNAI2 gene, a TGF-β-responsive mesenchymal factor, was validated. CDKN3, which prevents G1/S transition, was significantly upregulated in ATC and PDTC, and aberrantly spliced in ATC. Mutational analysis showed that most mutations were present in TP53 (42% of ATC; 27% of PDTC) or RAS (31% of ATC; 18% of PDTC). TP53 and RAS alterations showed evidence of mutual exclusivity (P=0.0354). PIK3CA, PTEN and CDKI mutations were present in 14-20% of PDTC, and in 10-14% of ATC. BRAF, CTNNB1 and AXIN1 mutations were rarely detected. Conclusion: Overall, this study identified crucial roles for TP53, RAS, CDKI, and TGF-β pathway, which may represent feasible therapeutic targets for ATC and PDTC treatment.
    The Journal of Clinical Endocrinology and Metabolism 01/2014; 99(3):jc20131512. DOI:10.1210/jc.2013-1512
  • Luis G. Sobrinho, Branca M. Cavaco, Hugo G. Ferreira
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    ABSTRACT: Objectivo O pseudohipoparatiroidismo tipo 1b (PHP1b) resulta de defeitos de metilação no locus materno do GNAS. É aceite que a hipocalcémia que se observa nestes casos resulta da consequente inactivação da hidroxilase 1α. Este estudo foi feito para caracterizar: 1) As relações entre as calcémias, fosfatémias e concentrações de PTH e de 1,25 dihidroxi vitamina D (1,25OH2D) nos doentes com PHP1b; 2) Se um modelo matemático do metabolismo do cálcio poderia reproduzir os dados observados. Doentes O estudo incluiu os casos de 139 doentes não medicados, extraidos da literatura, e que tinham medições simultâneas de Ca, P e PTH. Em 25 deles tinham também sido medidos os valores da 1,25OH2D. Resultados Os valores médios e o erro-padrão (SEM) foram: PTH = 43 pM (3,66); P = 2.16 mM (0,056); Ca = 1.69 mM (0,038); 1,25OH2D = 84 pM (10,9). Os valores da fosfatémia estavam fortemente correlacionados com os da calcémia (R = -0.590; p < 0.001) e com a idade age (R = -0.623; p < 0.001). Não se encontraram outras correlações significativas. O modelo matemático simulou com grande aproximação o padrão hormonal global do PHP 1b quando a depuração de fosfatos foi reduzida para 20%, a depuração de cálcio foi duplicada e resposta da 1α hidroxilase foi reduzida a 30%. Conclusões 1) As concentrações de1,25OH2D são normais na maior parte dos casos de PHP1b. Por consequência, não podem explicar a hipocalcémia; 2) A hipocalcémia só pode ser explicada pelo aumento da excreção fraccional de cálcio resultante da haplo-insuficiência do GNAS ao nível do túbulo distal; 3) O recurso a modelos matemáticos que simulam sistemas metabólicos complexos permite extrair, a partir de dados da rotina clínica, informações sobre fisiopatologia que não são acessíveis ao raciocínio intuitivo.
    01/2014; 9(1). DOI:10.1016/j.rpedm.2014.05.002
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    ABSTRACT: Familial non-medullary thyroid cancer (FNMTC) has been proposed as an aggressive clinical entity. To investigate potential distinguishing features as well as the biological and clinical aggressiveness of familial vs. sporadic papillary thyroid carcinoma (PTC), we assessed clinico-pathological characteristics, outcome measures and DNA ploidy. A matched-case comparative study. A series of patients with familial PTC (n=107) and two subgroups, one with ≥3 affected elements (n=32) and another including index cases only (n=61), were compared with patients with sporadic PTC (n=107), matched by age, gender, pTNM disease extension, and approximate follow-up duration. Histological variant, extrathyroidal extension, vascular invasion, tumour multifocality, and bilateral growth were evaluated. Ploidy pattern was analysed in available samples by DNA flow cytometry. The probabilities of disease-free and overall survival were estimated according to the Kaplan-Meier (K-M) method. No patient with familial PTC died of disease during follow-up (median, 72 months), contrarily to 5 patients (4.7%) (P=0.06) with sporadic PTC (median, 90 months). There was a significantly higher tumour multifocality in familial PTC (index cases subgroup) vs. sporadic PTC (P=0.035), and a trend, in the familial PTC cohort with ≥3 affected elements, to show more frequently extrathyroidal extension (P=0.054). No difference was observed in DNA ploidy status. The K-M analyses showed no significant differences between both entities in relation to disease-free or overall survival. Apart from multifocality, familial PTC appears to have similar clinical/prognostic behaviour when compared with sporadic forms of the disease.
    European Journal of Endocrinology 11/2013; DOI:10.1530/EJE-13-0865
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    ABSTRACT: OBJECTIVE: FOXE1 is a transcription factor required for thyroid differentiation and function. FOXE1 locus polymorphisms (chromosome 9q22.33) were recently associated with increased sporadic thyroid cancer risk. In this study, we aimed to investigate the association of FOXE1 variants with nonmedullary thyroid cancer (NMTC), in both sporadic and familial (FNMTC) cases from the Portuguese population. DESIGN AND METHODS: Nine variants located at the FOXE1 locus were sequenced in genomic DNA from 60 FNMTC probands and 80 patients with sporadic NMTC. Alleles were tested for association with thyroid cancer, against 130 healthy matched Portuguese controls. RESULTS: All variants were significantly associated with increased thyroid cancer risk when combining familial and sporadic cases (OR range=1.62-2.58). In particular, two reported risk variants were associated with the disease: rs965513 (allele A) with familial (OR=2.30, 95%CI=1.48-3.59, P=0.0002) and sporadic (OR=2.81, 95%CI=1.87-4.22, P<0.0001) NMTC; and rs1867277 (allele A) with the sporadic (OR=1.76, 95%CI=1.18-2.62, P=0.0052) and combined NMTC cases (OR=1.70, 95%CI=1.21-2.40, P=0.0022). Interestingly, we also identified association of FOXE1 polyalanine tract expansions (>14 alanines) with thyroid cancer risk, in both familial (OR=2.56, 95%CI=1.64-4.01, P<0.0001) and sporadic (OR=2.44, 95%CI=1.61-3.68, P<0.0001) cases. CONCLUSIONS: We found compelling evidence of association between FOXE1 variants and thyroid cancer risk in the Portuguese population. To our knowledge, this is the first study supporting the association of this locus with both sporadic and familial NMTC susceptibility. © 2012 Blackwell Publishing Ltd.
    Clinical Endocrinology 08/2012; 77(6). DOI:10.1111/j.1365-2265.2012.04505.x
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    07/2012; 7(2):84. DOI:10.1016/S1646-3439(12)70069-X
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    ABSTRACT: Germline mutations in the HRPT2 gene are associated with the hereditary hyperparathyroidism-jaw tumour syndrome (HPT-JT) and a subset of familial isolated hyperparathyroidism (FIHP). Somatic HRPT2 mutations are detected in sporadic parathyroid carcinomas and less frequently in cystic adenomas. The purpose of this study was to investigate the underlying HRPT2 defect in a young patient with symptomatic hyperparathyroidism due to an apparently sporadic parathyroid adenoma with cystic features. HRPT2 mutations in the patient's genomic and parathyroid tumour DNA were screened by PCR-based sequencing. Tumour loss of heterozygosity (LOH) at the HRPT2 locus was assessed with microsatellite markers. A large germline HRPT2 deletion was investigated by real-time quantitative PCR analysis (qPCR). Genomic DNA losses were also appraised by chromosomal comparative genomic hybridization (cCGH). No germline HRPT2 point mutation was detected by direct sequencing. A novel hemizygous HRPT2 somatic mutation (c.32delA) was identified in the tumour. Apparent constitutional homozygosity for HRPT2 flanking microsatellite markers, and absence of LOH at a distal marker, suggested a large germline deletion. Gene dose mapping by qPCR unveiled a de novo deletion of the whole HRPT2 gene and adjacent loci (<9·3 Mb in size). cCGH confirmed germline DNA loss involving the HRPT2 locus. We report the first large germline deletion of the HRPT2 gene, which was not detectable by conventional PCR-based sequencing methods. This finding emphasizes that qPCR should be implemented in HRPT2 molecular analysis, which may improve genetic assessment and clinical management of patients with FIHP and HPT-JT.
    Clinical Endocrinology 07/2011; 76(1):33-8. DOI:10.1111/j.1365-2265.2011.04184.x
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    ABSTRACT: The diagnosis of parathyroid carcinomas is often difficult. HRPT2 mutations have been identified in familial [hyperparathyroidism-jaw tumor (HPT-JT) syndrome] and sporadic parathyroid carcinomas, supporting that HRPT2 mutations may confer a malignant potential to parathyroid tumors. In this study, we report the clinical, histopathological, and genetic investigation of two unrelated cases, whom had apparently sporadic malignant parathyroid tumors, initially diagnosed as adenomas. In one case, the differential diagnosis was complicated by cervical seeding of parathyroid tumor cells. Genetic studies identified de novo HRPT2 germline mutations in cases 1 (c.518_521delTGTC [p.Ser174LysfsX27]) and 2 (c.226 C > T [p.Arg76X]), unveiling the hereditary HPT-JT syndrome in both patients. Furthermore, the identification of somatic mutations in the patients‟ parathyroid tumors provided evidence for complete inactivation of the HRPT2 gene, which was consistent with the tumor malignant features. The sensitivity of parafibromin immunostaining to detect HRPT2 mutations was limited. The present data suggests that patients with apparently sporadic parathyroid carcinomas, or parathyroid tumors with atypical histological features, should undergo molecular genetic testing, as it may detect germline HRPT2 mutations. Establishing the diagnosis of hereditary HPT-JT syndrome is relevant for clinical counseling and management of the carriers and their relatives.
    Endocrine Pathology 03/2011; 22(1):44-52. DOI:10.1007/s12022-011-9151-1
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    ABSTRACT: Sporadic medullary thyroid carcinomas (MTC) frequently harbor mutations in the RET protooncogene. We have earlier reported a series of 51 sporadic MTC with 64.7% of RET-positive and 35.3% of RET-negative cases. In the present study, we investigated the possible involvement of RAS and BRAF protooncogenes in the development of sporadic RET-negative MTC. We performed PCR amplification and sequencing analysis of the three mutational hotspots (codons 12, 13, and 61) of the H-, K-, and N-RAS genes, and of the mutational hotspot (codon 600) and exon 11 of the BRAF gene in 65 sporadic MTC, of which 40 were RET positive and 25 were RET negative. Somatic H-RAS and K-RAS mutations were detected in 14 of 25 (56.0%) and three of 25 (12.0%) of RET-negative sporadic MTC, respectively. On the other hand, only one of 40 (2.5%) RET-positive sporadic MTC had a RAS mutation, namely in H-RAS. One of the H-RAS mutations was novel (c.32_37dupCCGGCG). No mutations of N-RAS or BRAF were detected in all assessed tumor samples. Overall, our results showed that RAS mutations were present in 68.0% (17 of 25) of the RET-negative MTC and in only 2.5% of the RET-positive MTC (P < 0.0001), suggesting that activation of the protooncogenes RAS and RET represents alternative genetic events in sporadic MTC tumorigenesis.
    The Journal of Clinical Endocrinology and Metabolism 02/2011; 96(5):E863-8. DOI:10.1210/jc.2010-1921
  • Rute A Tomaz, Branca M Cavaco, Valeriano Leite
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    ABSTRACT: We detected false homozygosity at the NESP55 differentially methylated region of the imprinted GNAS locus while analyzing the segregation of single-nucleotide polymorphisms (SNPs) in families with pseudohypoparathyroidism type Ib (PHP-Ib). We hypothesized that differential methylation of NESP55 could affect polymerase chain reaction (PCR) amplification, resulting in allele dropout. We genotyped 10 normal controls for four SNPs in NESP55 differentially methylated region. SNPs were amplified by standard PCR conditions and with the addition of dimethyl sulfoxide. The methylated allele was identified by HpaII analysis, and haplotypes were confirmed using subcloning strategies. All SNPs were also genotyped in a PHP-Ib patient (P1), carrying methylation at both NESP55 alleles, and in an in vitro methylated control DNA (SSSI-N4). In the control samples, we identified allele dropout of the methylated allele in 85% of the amplifications, using standard PCR conditions. Addition of dimethyl sulfoxide to the PCR successfully prevented dropout in all cases. No amplification bias was observed for P1 and SSSI-N4 samples. For the first time, we report that differential methylation of imprinted regions can lead to preferential amplification of unmethylated alleles. Addition of coadjuvants to the PCR may facilitate amplification of both alleles, providing an accurate genotyping in cases with methylation-related diseases.
    Genetic Testing and Molecular Biomarkers 08/2010; 14(4):455-60. DOI:10.1089/gtmb.2010.0029
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    ABSTRACT: Patients with pseudohypoparathyroidism type Ib (PHP-Ib) present hypocalcemia and hyperphosphatemia, as a consequence of a resistance to PTH action, through its G-protein-coupled receptor, in the renal tubules. This resistance results from tissue-specific silencing of the G-protein alpha-subunit (G(s)α), due to imprinting disruption of its encoding locus--GNAS. In familial PHP-Ib, maternally inherited deletions at the STX16 gene are associated to a regional GNAS methylation defect. In sporadic PHP-Ib, broad methylation changes at GNAS arise from unknown genetic causes. In this study, we describe the clinical presentation of PHP-Ib in four Portuguese patients (two of whom were siblings), and provide further insight for the management of patients with this disease. The diagnosis of PHP-Ib was made after detection of GNAS imprinting defects in each of the cases. In the siblings, a regional GNAS methylation change resulted from a known 3.0 kb STX16 deletion. In the other two patients, the broad methylation defects at GNAS, which were absent in their relatives, resulted from genetic alterations that remain to be identified. We report the first clinical and genetic study of Portuguese patients with PHP-Ib. The genetic identification of a hereditary form of this rare disease allowed an early diagnosis, and may prevent hypocalcemia-related complications.
    Endocrine 06/2010; 37(3):408-14. DOI:10.1007/s12020-010-9321-9
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    J M Pita, A Banito, B M Cavaco, V Leite
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    ABSTRACT: Poorly differentiated thyroid carcinomas (PDTC) represent a heterogeneous, aggressive entity, presenting features that suggest a progression from well-differentiated carcinomas. To elucidate the mechanisms underlying such progression and identify novel therapeutic targets, we assessed the genome-wide expression in normal and tumour thyroid tissues. Microarray analyses of 24 thyroid carcinomas - 7 classic papillary, 8 follicular variants of papillary (fvPTC), 4 follicular (FTC) and 5 PDTC - were performed and correlated with RAS, BRAF, RET/PTC and PAX8-PPARG alterations. Selected genes were validated by quantitative RT-PCR in an independent set of 28 thyroid tumours. Unsupervised analyses showed that gene expression similarity was higher between PDTC and fvPTC, particularly for tumours harbouring RAS mutations. Poorly differentiated thyroid carcinomas presented molecular signatures related to cell proliferation, poor prognosis, spindle assembly checkpoint and cell adhesion. Compared with normal tissues, PTC had 307 out of 494 (60%) genes over-expressed, FTC had 137 out of 171 (80%) genes under-expressed, whereas PDTC had 92 out of 107 (86%) genes under-expressed, suggesting that gene downregulation is involved in tumour dedifferentiation. Significant UHRF1 and ITIH5 deregulated gene expression in PDTC, relatively to normal tissues, was confirmed by quantitative RT-PCR. Our findings suggest that fvPTC are possible precursors of PDTC. Furthermore, UHRF1 and ITIH5 have a potential therapeutic/prognostic value for aggressive thyroid tumours.
    British Journal of Cancer 10/2009; 101(10):1782-91. DOI:10.1038/sj.bjc.6605340
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    ABSTRACT: Screening of REarranged during Transfection (RET) gene mutations has been carried out in different series of sporadic medullary thyroid carcinomas (MTC). RET-positive tumours seem to be associated to a worse clinical outcome. However, the correlation between the type of RET mutation and the patients' clinicopathological data has not been evaluated yet. We analysed RET exons 5, 8, 10–16 in fifty-one sporadic MTC, and found somatic mutations in thirty-three (64.7%) tumours. Among the RET-positive cases, exon 16 was the most frequently affected (60.6%). Two novel somatic mutations (Cys630Gly, c.1881del18) were identified. MTC patients were divided into three groups: group 1, with mutations in RET exons 15 and 16; group 2, with other RET mutations; group 3, having no RET mutations. Group 1 had higher prevalence (P=0.0051) and number of lymph node metastases (P=0.0017), and presented more often multifocal tumours (P=0.037) and persistent disease at last control (P=0.0242) than group 2. Detectable serum calcitonin levels at last screening (P=0.0119) and stage IV disease (P=0.0145) were more frequent in group 1, than in the other groups. Our results suggest that, among the sporadic MTC, cases with RET mutations in exons 15 and 16 are associated with the worst prognosis. Cases with other RET mutations have the most indolent course, and those with no RET mutations have an intermediate risk.
    British Journal of Cancer 05/2009; 100(11):1777-83. DOI:10.1038/sj.bjc.6605056
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    ABSTRACT: Familial nonmedullary thyroid carcinoma (FNMTC) accounts for approximately 5% of all thyroid tumors. Genetic mapping studies have identified four different chromosomal regions predisposing to FNMTC: fPTC/PRN (1p13.2-1q22), NMTC1 (2q21), MNG1 (14q32), and TCO (19p13.2). Our objective was to map the gene predisposing to familial thyroid epithelial neoplasia in a large Portuguese family. The clinical screening of a Portuguese family identified 11 members affected with benign thyroid lesions and five affected with thyroid carcinomas. Linkage analysis excluded the involvement of the fPTC/PRN, NMTC1, MNG1, and TCO loci. To map the gene predisposing to thyroid epithelial neoplasia in this family, a genome-wide linkage analysis was conducted, using DNA samples from 17 family members and high-density single-nucleotide polymorphism arrays. A genome-wide significant evidence of linkage, to a single region on chromosome 8p23.1-p22 was obtained, with a maximum parametric haplotype-based LOD score of 4.41 (theta=0.00). Linkage analysis with microsatellite markers confirmed linkage to 8q23.1-p22, and recombination events delimited the minimal region to a 7.46-Mb span. Seventeen suggestive candidate genes located in the minimal region were excluded as susceptibility genes by mutational analysis. Allelic losses in the 8p23.1-p22 region were absent in seven thyroid tumors from family members, suggesting that the inactivation of a putative tumor suppressor gene may have occurred through other mechanisms. Our results present evidence for the existence of a novel familial thyroid epithelial neoplasia susceptibility locus on chromosome 8p23.1-p22, providing the basis for the identification of a gene for this disease.
    Journal of Clinical Endocrinology &amp Metabolism 10/2008; 93(11):4426-30. DOI:10.1210/jc.2008-0449

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1k Citations
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Institutions

  • 2014
    • University of Lisbon
      Lisboa, Lisbon, Portugal
  • 2005–2014
    • New University of Lisbon
      Lisboa, Lisbon, Portugal
  • 2002–2014
    • Instituto Português de Oncologia de Lisboa - IPO
      • Centro de Investigação de Patobiologia Molecular
      Lisboa, Lisbon, Portugal
  • 2007–2008
    • Instituto de Medicina Molecular
      Lisboa, Lisbon, Portugal
  • 2001–2006
    • University of Oxford
      • Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM)
      Oxford, England, United Kingdom
  • 1995–2006
    • Instituto Português de Oncologia
      Oporto, Porto, Portugal
  • 1999–2003
    • MRC Clinical Sciences Centre
      London Borough of Harrow, England, United Kingdom