RESUMO
OBJECTIVES: 1) To correlate the methylation status of the O6-methylguanine-DNA-methyltransferase (MGMT) promoter to its gene and protein expression levels in glioblastoma and 2) to determine the most reliable method for using MGMT to predict the response to adjuvant therapy in patients with glioblastoma. BACKGROUND: The MGMT gene is epigenetically silenced by promoter hypermethylation in gliomas, and this modification has emerged as a relevant predictor of therapeutic response. METHODS: Fifty-one cases of glioblastoma were analyzed for MGMT promoter methylation by methylation-specific PCR and pyrosequencing, gene expression by real time polymerase chain reaction, and protein expression by immunohistochemistry. RESULTS: MGMT promoter methylation was found in 43.1 percent of glioblastoma by methylation-specific PCR and 38.8 percent by pyrosequencing. A low level of MGMT gene expression was correlated with positive MGMT promoter methylation (p = 0.001). However, no correlation was found between promoter methylation and MGMT protein expression (p = 0.297). The mean survival time of glioblastoma patients submitted to adjuvant therapy was significantly higher among patients with MGMT promoter methylation (log rank = 0.025 by methylation-specific PCR and 0.004 by pyrosequencing), and methylation was an independent predictive factor that was associated with improved prognosis by multivariate analysis. DISCUSSION AND CONCLUSION: MGMT promoter methylation status was a more reliable predictor of susceptibility to adjuvant therapy and prognosis of glioblastoma than were MGMT protein or gene expression levels. Methylation-specific polymerase chain reaction and pyrosequencing methods were both sensitive methods for determining MGMT promoter methylation status using DNA extracted from frozen tissue.
Assuntos
Adolescente , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neoplasias Encefálicas/genética , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Glioblastoma/genética , Regiões Promotoras Genéticas/genética , Proteínas Supressoras de Tumor/genética , Neoplasias Encefálicas/metabolismo , Metilação de DNA , Metilases de Modificação do DNA/metabolismo , Enzimas Reparadoras do DNA/metabolismo , Expressão Gênica , Glioblastoma/metabolismo , Imuno-Histoquímica , Estimativa de Kaplan-Meier , Reação em Cadeia da Polimerase , Valor Preditivo dos Testes , Prognóstico , Estatísticas não Paramétricas , Fatores de Tempo , Proteínas Supressoras de Tumor/metabolismoRESUMO
Nesta palestra a pesquisadora apresenta alguns conceitos elucidativos sobre a genômica, a metodologia empregada - em que há uma inversão: não há uma hipótese inicial, o objetivo a ser perseguido é a coleta de dados-, as principais etapas, as características de um projeto Genoma, suas aplicações, para, no final, expôr o confronto com as estruturas clássicas de fazer ciência, de estar em uma universidade. Verifica-se assim que a genômica, por ser uma área muito nova, como a Gerontologia, ao contrário do que se pensa, enfrenta algumas dificuldades comuns: reconhecimento e financiamento.