Fas and Bcl-2 protein expression in thyrocytes of patients with nodular goiter

Objective: The relative expression of the apoptotic protein Fas and the ant i-apoptotic protein Bcl-2 were investigated in thyrocytes from patients wit h non-toxic nodular goiter (NTG. n=20) and Hashimoto's thyroiditis (HT, n=5 ), who underwent fine-needle aspiration biopsy for diagnostic reasons. on t he basis of the clinical and cytological findings, the patients with NTG we re sub-classified into the group of those with colloid nodules (n=9), degen erative nodules (n=6) and adenomatous nodules (n=5). Methods: Fine-needle biopsy aspirates were examined by immunocytochemistry for Fas and Bcl-2 expression, using specific monoclonal antibodies. For the evaluation of Fas and Bcl-2 immunoreactivity, an expression index, based o n the number of cells with positive staining, was used: grade I included sa mples with positive staining in <20% of cells; grade 2 included samples wit h 20-50% positive cells: and grade 3 included samples with >50% positive ce lls. Results: Fas protein expression was generally low (grade 1) in patients wit h nodular goiter, in contrast to patients with HT in whom high expression w as detected (grade 3). Only in aspirates from degenerative nodules (four ou t of six), and in which lymphocytes were also present, was Fas expressed at an intermediate level (grade 2). On the other hand, Bcl-2 protein was diff erentially expressed among the nodule subtypes. It was low in colloid and d egenerative nodules (grade 1) but high in adenomatous ones (grades 2 and 3) . Bcl-2 expression was also low in patients with HT (grade 1). Conclusion: It is concluded that in comparison to HT where there is up-regu lation of Fas and downregulation of Bcl-2 protein, Fas expression is low in human goiter, indicating low apoptotic activity. The regulation of Bcl-2 p rotein differs between adenomatous and colloid nodules, suggesting that thi s protein may play a role in the differentiation of thyroid nodules.