Thymosin ß-10Gene Overexpression Correlated with the Highly Malignant Neoplastic Phenotype of Transformed Thyroid Cells in Vivo and in Vitro1

A subtractive thyroid cDNA library was constructed from two human thyroid carcinoma cell lines originating from an anaplastic carcinoma and a papillary thyroid carcinoma. The library was used to identify genes correlated with the progression to a highly malignant phenotype. The thymosin ß-10gene was isolated and found to be expressed at much higher levels in the anaplastic cell line than in the papillary cells. The thymosin ß-10gene was overexpressed in five carcinoma cell lines com pared with normal thyroid tissue and normal thyroid primary culture cells. The highest expression occurred in the most malignant cell lines. Thymosin ß-10gene expression was also increased in surgically removed human thyroid carcinomas and was highest in the anaplastic carcinomas. Thymosin ß-10gene expression was correlated with the degree of the malignant phenotype also in rat thyroid cells transfected with cellular and viral oncogenes of different tumorigenicity. These results show that thy mosin ß-10Overexpression is a general event of thyroid cell neoplastic transformation and suggest that the gene is involved in the progression of thyroid carcinogenesis. Finally, the thymosin ß-10gene was located on chromosome 2q37 by fluorescence in situ hybridization analysis.