ABSTRACT
Susceptibility to chemical carcinogens plays an important role in the development of most cancers. Several polymorphisms of human drug-metabolizing enzymes influence this individual susceptibility. The genes that encode the isoenzymes of the glutathione s-transferase (GST) system present a polymorphic inheritance. The GST mu 1 (GSTM1) and GST theta 1 (GSTT1) genes have a null allele variant in which the entire gene is absent. The null genotype for both enzymes has been associated with many different types of tumors. To look for the influence of the inheritance pattern of these enzymes on thyroid cancer risk, we used a triplex PCR that included beta-globin gene as a DNA quality control to compare 300 normal individuals of our population to 116 goiter patients. There were 49 cases of benign and 67 cases of malignant nodules: 50 papillary and 17 follicular carcinomas. Comparison between thyroid tumor specimens and normal corresponding samples of 35 cancer patients demonstrated identical patterns, suggesting that the GST system is not involved in the process of follicular dedifferentiation. There was no statistical difference between the prevalence of the deleted alleles in the normal individuals and in the goiter patients. However, papillary carcinoma patients (10%) and follicular carcinoma patients (17%) presented a higher prevalence of the null genotype than the normal population individuals (5%; P < 0.05). We found a 2.6 increased risk of thyroid cancer in individuals with the GSTT1 and GSTM1 combined null inheritance, suggesting that this genotype may be associated with an increased susceptibility to thyroid cancer.
Subject(s)
Carcinoma, Papillary, Follicular/epidemiology , Carcinoma, Papillary, Follicular/genetics , Glutathione Transferase/genetics , Thyroid Neoplasms/epidemiology , Thyroid Neoplasms/genetics , Adolescent , Adult , Aged , Biomarkers, Tumor/genetics , Brazil/epidemiology , Case-Control Studies , Female , Follow-Up Studies , Gene Expression Profiling , Genetic Predisposition to Disease/genetics , Genotype , Humans , Male , Middle Aged , Prospective Studies , Risk FactorsABSTRACT
We investigated the relationship between the level of c-myc mRNA and histologic aggressiveness in thyroid tumors obtained at surgery. In thyroid carcinomas, there was a positive correlation between these two parameters, while in benign tumors there was no correlation between cellularity and the expression of the proto-oncogene c-myc. These results might be useful in the prognosis of thyroid tumors and consequently helpful in the management of the patient.