RESUMO
A common mutation in the BRAF gene, comprising the T1799A nucleotide transversion, which leads to the V600E amino acid substitution in the BRAF protein, has been observed in about 50% of papillary thyroid carcinomas (PTCs). However, BRAF protein expression has been rarely examined in such tumors. Clinical studies have shown important associations between BRAF mutation and clinical parameters in PTC, such as progression, invasion, and recurrence. The aim of this study was to evaluate the association between BRAF protein overexpression and the BRAF V600E mutation in a group of PTC patients. The study group included 116 patients with PTC from Araújo Jorge Hospital, Goiânia, Goiás, Brazil. Immunohistochemistry was utilized to analyze BRAF protein expression. Presence of the BRAF V600E mutation was determined by polymerase chain reaction amplification and restriction fragment length polymorphism, and confirmed by direct sequencing. The chi-square test with Yates correction and the Fisher exact test were used for statistical analysis. BRAF overexpression was detected in 55 patients with PTC (47.4%) and the BRAF V600E mutation was observed in 74 patients (63.8%). In the studied group, significant associations were observed between the BRAF V600E mutation and BRAF protein overexpression (P = 0.0115), and also between BRAF overexpression and extra-thyroid extension of the tumor (P = 0.0111). This study demonstrated a significant association between BRAF overexpression and the BRAF V600E mutation in PTC, highlighting the importance of these molecular events in the process of PTC carcinogenesis.
Assuntos
Substituição de Aminoácidos , Carcinoma/genética , Mutação Puntual , Proteínas Proto-Oncogênicas B-raf/genética , Neoplasias da Glândula Tireoide/genética , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Sequência de Bases , Carcinoma/patologia , Carcinoma/cirurgia , Carcinoma Papilar , Análise Mutacional de DNA , Feminino , Expressão Gênica , Humanos , Metástase Linfática , Masculino , Pessoa de Meia-Idade , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , Estudos Retrospectivos , Câncer Papilífero da Tireoide , Neoplasias da Glândula Tireoide/patologia , Neoplasias da Glândula Tireoide/cirurgiaRESUMO
BRAF V600E is the most common mutation in cutaneous melanomas, and has been described in 30-72% of such cases. This mutation results in the substitution of valine for glutamic acid at position 600 of the BRAF protein, which consequently becomes constitutively activated. The present study investigated the BRAF V600E mutation frequency and its clinical implications in a group of 77 primary cutaneous melanoma patients treated in a cancer reference center in Brazil. Mutation analysis was accomplished by polymerase chain reaction, restriction fragment length polymorphism, and automated DNA sequencing. The chi-squared and Fischer exact tests were used for comparative analyses. The BRAF V600E mutation was detected in 54/77 (70.1%) melanoma subjects. However, no statistically significant association was found between the presence of the mutation and clinical or prognostic parameters. Our results demonstrated that the BRAF V600E mutation is a common event in melanomas, representing an important molecular target for novel therapeutic approaches in such tumors.
Assuntos
Melanoma/genética , Terapia de Alvo Molecular , Mutação/genética , Proteínas Proto-Oncogênicas B-raf/genética , Idoso , Brasil , Feminino , Humanos , Masculino , Melanoma/patologia , Pessoa de Meia-Idade , Quinases de Proteína Quinase Ativadas por Mitógeno/genética , Polimorfismo de Nucleotídeo Único , Neoplasias Cutâneas , Melanoma Maligno CutâneoRESUMO
Soft tissue sarcomas (STS) are tumors of mesodermal origin, comprising about 1% of all adult neoplasms. Management of such tumors is an important medical challenge. TP53 codon 72 polymorphism results in either the arginine or proline form of the p53 protein; several studies have investigated whether codon 72 polymorphisms are risk and prognostic factors for cancer. We investigated p53 codon 72 polymorphism (Arg72Pro) frequencies with respect to the susceptibility and the clinical outcome of patients with STS. A series of 100 STS were genotyped for the p53 Arg72Pro polymorphism using polymerase chain reaction. Genotype frequencies were compared to a group of 85 healthy donors (controls). Possible associations between polymorphic genotypes, clinicopathological factors and survival of STS patients were also investigated. Genotypic frequencies obtained for STS patients did not significantly differ from that obtained for controls. In the STS group, p53 codon 72 polymorphic variants were not significantly associated with gender, age, tumor size, clinical stage, tumor grade, histology, or nodal or distant metastasis. The five-year overall survival rate for the STS group was 48%; it was significantly affected by tumor grade, clinical stage, and nodal and distant metastasis. Soft tissue sarcoma patients with the Pro/Pro variant had a reduced survival rate (30%), when compared to the p53 Arg/Arg (45%) and the p53 Arg/Pro groups (55%). However, the differences between these groups were not significant (P = 0.44).
Assuntos
Códon/genética , Polimorfismo Genético , Sarcoma/genética , Proteína Supressora de Tumor p53/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Arginina/genética , Feminino , Frequência do Gene , Genes p53 , Predisposição Genética para Doença , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Prolina/genética , Adulto JovemRESUMO
The development of radiological and nuclear technologies and the deployment of nuclear weapons have made ionizing radiation one of the most studied human mutagens. Exposure to ionizing radiation produces DNA damage which can result in mutation and cancer, making the risk associated with human exposure a critical issue. In this paper we estimate the risk associated with radiation exposure for individuals exposed to 137Cs during the 1987 Goiânia radiological accident. Using combined regression slopes from both the in vivo hprt mutant frequency and micronucleus frequency data we estimated a doubling dose of 173 (+/-47) cGy for these two endpoints. This is in close agreement with the published estimates for low dose rate and chronic exposure to low-LET radiation. We obtained risk estimates of about 24-fold increase in dominant disorders in the post-exposure generation of the directly exposed population. No detectable increase was found in the population at large. The risk of carcinogenesis in the directly exposed population was found to be increased by a factor in the range of 1.4 to 1.5. The small sample size in this study requires a large element of caution with respect to risk estimates interpretation. Moreover, the doubling dose estimates prepared here are derived from lymphocytes. This somatic data may require additional considerations for both cancer and certainly germ-line events. Nevertheless, the risk of carcinogenesis and genetic harm for this population are good indicators of the potential genetic damage imposed by ionizing radiation to the Goiânia population.
Assuntos
Contaminação Radioativa do Ar , Mutação , Neoplasias Induzidas por Radiação/epidemiologia , Liberação Nociva de Radioativos , Medição de Risco , Brasil , Radioisótopos de Césio , Relação Dose-Resposta à Radiação , Humanos , Testes para Micronúcleos , Testes de Mutagenicidade , Radiação IonizanteRESUMO
We have examined the effects of ionizing radiation on somatic mutations in vivo, using the hprt clonal assay. The study was performed on blood samples obtained from children exposed during a radiological accident that happened in 1987, in Goiânia, Brazil. The group of children exposed to ionizing radiation includes six males and four females ranging in age from 6 to 14 years at the time of exposure. The radiation doses ranged from 15 to 70 cGy. A Brazilian control group, not exposed to ionizing radiation, was also analyzed under similar conditions. the mean hprt mutant frequency for the exposed group was 4.6 times higher than the control group, although the cloning efficiency from the exposed group was significantly reduced. Linear regression analysis of the mutant frequency and ionizing radiation dose did not show a significant relationship between these two parameters. However, a reliable inverse relationship was demonstrated when the regression analysis was performed with nonselective cloning efficiency and ionizing radiation dose. It was demonstrated that nonselective cloning efficiency diminishes as ionizing radiation dose increases. To correct mutant frequencies for clonal events, the clonal relationship between the hprt mutant clones was examined by T-cell receptor analysis. The majority of the mutants analyzed represented individual clones, thus validating the observed mutant frequencies.