Increased Type 3 Deiodinase Expression in Papillary Thyroid Carcinoma

Background: Thyroid hormone regulates a wide range of cellular activities, including the balance between cell proliferation and differentiation. The thyroid-hormone-inactivating type 3 deiodinase (DIO3, D3) has been shown to be reactivated in human neoplasias. Here, we evaluated DIO3 expression in human papillary thyroid carcinoma (PTC). Methods: Tumor and surrounding normal thyroid tissue were collected from 26 unselected patients with PTC. Clinical data were retrospectively reviewed in medical records. DIO3 mRNA levels were measured by real-time polymerase chain reaction and D3 activity by paper-descendent chromatography. Studies of DIO3 gene regulation were performed in a human PTC-derived cell line (K1 cells). BRAFV600E mutation was identified in DNA from paraffin-embedded tissues by direct sequencing. Immunohistochemistry analyses were performed using a specific human D3 antibody. Results: Increased D3 activity was detected in all 26 PTC samples analyzed as compared with adjacent thyroid tissue. The ...