Selenoprotein Expression in Hürthle Cell Carcinomas and in the Human Hürthle Cell Carcinoma Line XTC.UC1

Hurthle cell carcinomas (HTC) are characterized by mitochondrial amplification and enhanced oxygen metabolism. To clarify if defects in enzymes scavenging reactive oxygen species are involved in the pathogenesis of HTC, we analyzed selenium (Se)-dependent expression of various detoxifying selenoproteins in the HTC cell line XTC.UC1. Glutathione peroxidase and thioredoxin reductase activity was found both in cell lysates and conditioned media of XTC.UC1 cells and was increased by Na2SeO3. Western blot analysis demonstrated the presence of thioredoxin reductase both in cell lysates and conditioned media and of glutathione peroxidase 3 in conditioned media. Type I 5'-deiodinase, another selenoprotein that catalyzes thyroid hormone metabolism, was detectable only in cell lysates by enzyme assay and Western blot, and responded to stimulation by both Na2SeO3 and retinoic acid. A selenoprotein P signal was detected in conditioned media by Western blot, but was not enhanced by Na2SeO3 treatment. In situ hybridiza...