RESUMEN
The p53 tumor suppressor gene is frequently mutated and the K-ras oncogene is occasionally mutated in primary specimens of human lung carcinomas. These mutated genes also cooperate in the immortalization and neoplastic transformation of rodent cells. To determine whether these mutations are necessary for maintenance of the immortalized and/or neoplastically transformed states of human bronchial epithelial cells, the p53 gene and regions of the ras (K-, H-, and N-) genes were sequenced in nine human lung carcinoma cell lines. Detection of p53 mutations by polymerase chain amplification and direct DNA sequencing was corroborated by p53 immunocytochemistry and coimmunoprecipitation of p53 with heat shock protein 70. p53 and ras genes were frequently, but not always, mutated in the carcinoma cell lines. These data are consistent with the hypothesis that multiple genetic changes involving both protooncogenes and tumor suppressor genes occur during lung carcinogenesis.
Asunto(s)
Genes p53/genética , Genes ras/genética , Proteínas de Choque Térmico/metabolismo , Neoplasias Pulmonares/genética , Mutación/genética , Proteína p53 Supresora de Tumor/metabolismo , Secuencia de Bases , Bronquios/citología , Bronquios/fisiología , Transformación Celular Neoplásica/genética , Células Epiteliales , Exones/fisiología , Humanos , Inmunohistoquímica , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patología , Datos de Secuencia Molecular , Pruebas de Precipitina , Unión Proteica , Células Tumorales Cultivadas , Proteína p53 Supresora de Tumor/genéticaRESUMEN
The extensive metabolizer phenotype of debrisoquine has been associated with increased risk of lung cancer, and it has been proposed that a molecular test for this phenotype is feasible. DNA restriction fragment length polymorphisms of the human debrisoquine 4-hydroxylase gene locus (CYP2D6), and the metabolic phenotype for debrisoquine have been studied in a group of healthy volunteers, a group of lung cancer patients and two control groups (chronic obstructive pulmonary disease patients and patients with cancers at sites other than the lung). Confirmation of four distinct XbaI allelic fragments (44, 29, 16/9 and 11.5 kb), previously identified among caucasians, was obtained. The 29 kb alleles were the most frequently observed in both poor and extensive metabolizers of debrisoquine. Alleles of 44 kb were found with approximately equal frequency among both poor and extensive metabolizers. The data are consistent with the hypothesis that the 11.5 and 44 kb fragments are associated with mutant alleles of the CYP2D6 gene, but the power of phenotype prediction by these alleles was less than that previously reported for a European (Swiss-German) population. Similarly, the data also show that 8% of 29 kb homozygotes are poor metabolizers (indicating that at least 28% of 29 kb fragments are also associated with mutant alleles) and are not therefore informative for predicting the debrisoquine phenotype. The 16/9 allele may represent either wild-type or mutant alleles. Restriction fragments of 44 kb were found more frequently among cancer patients and chronic obstructive pulmonary disease patients (30%) than among the healthy volunteer group (7%). Genotypes observed were not related to lung tumor histology. Furthermore, at least three EcoRI alleles were found to be in linkage disequilibrium with the 'mutant' 44 kb allele. These data suggest that the 44 kb allele can comprise three distinct haplotypes, in contrast to studies of a European population. These studies indicate that no single mutant CYP2D6 allele as determined by EcoRI appears to be associated with lung cancer, despite the findings that these patients are invariably of the extensive metabolizer phenotype.
Asunto(s)
Sistema Enzimático del Citocromo P-450/genética , Genes , Neoplasias Pulmonares/genética , Oxigenasas de Función Mixta/genética , Neoplasias/genética , Polimorfismo de Longitud del Fragmento de Restricción , Adenocarcinoma/enzimología , Adenocarcinoma/genética , Carcinoma de Células Pequeñas/enzimología , Carcinoma de Células Pequeñas/genética , Carcinoma de Células Escamosas/enzimología , Carcinoma de Células Escamosas/genética , Citocromo P-450 CYP2D6 , Debrisoquina/metabolismo , Desoxirribonucleasa EcoRI , Desoxirribonucleasas de Localización Especificada Tipo II , Femenino , Humanos , Enfermedades Pulmonares Obstructivas/enzimología , Enfermedades Pulmonares Obstructivas/genética , Neoplasias Pulmonares/enzimología , Masculino , Neoplasias/enzimología , Fenotipo , Valores de ReferenciaRESUMEN
The hypothesis that rare variable nucleotide tandem repeat alleles of the Ha-ras-1 polymorphism are an inherited predisposing factor in human lung carcinogenesis has been evaluated in an age, race, and smoking matched case-control study. Twenty-three different alleles were identified by their restriction fragment length in DNA isolated from peripheral blood lymphocytes and were categorized into three groups: common; intermediate; and rare. The frequencies of rare alleles in blacks with either squamous cell carcinoma, large cell carcinoma, or small cell carcinoma were found to be significantly higher than those among groups of control subjects that were comprised of chronic obstructive pulmonary disease patients and patients with cancer at sites other than the lung. A similar trend which did not reach statistical significance was observed in whites. These data are consistent with the hypothesis that inheritance of Ha-ras-1 rare restriction fragment length alleles represents a genetic risk factor for some human lung cancers. The biological basis of this observation remains to be clarified, and it is possible that ethnic variations in rare allele frequencies are responsible for the differences noted. However, the data suggest that further evaluation of the Ha-ras-1 polymorphism as a marker of individual lung cancer susceptibility is warranted.