Expression of α-Klotho protein in human thyroid cancers - an immunohistochemical study. 
The α-Klotho protein was discovered as a gene controlling the process of aging, but further studies indicated that it also plays the role of a tumour suppressor.  Although numerous studies were performed on the role of the α-Klotho gene and protein in neoplasia, the data on α-Klotho protein expression in thyroid cancers are very scarce.  Our study presents the immunohistochemical investigation of α-Klotho expression in benign and malignant thyroid tumours.  The material included samples of benign (nodular hyperplasia, follicular adenoma), differentiated (follicular and papillary) cancers and aggressive thyroid cancers of low differentiation grade.  The samples were immunostained using two different monoclonal anti-α-Klotho antibodies.  From the two antibodies used in this study, one (EPR6856) reacted probably with the soluble form of Klotho and immunostained mostly the colloid filling thyroid follicles and intravascular or extravascular serum deposits.  The other (A-9 antibody) immunostained the follicular epithelium in benign thyroid lesions as well as the epithelial tumoural cells in differentiated thyroid (follicular and papillary cancers).  In the thyroid cancers of high malignancy, the immunostaining with A-9 anti-α-Klotho antibody was (except in one case) negative or very weak.  Our results indicate that lowered expression of a- Klotho is involved in the process of thyroid neoplasia.