Defective mitochondrial ATP synthesis in oxyphilic thyroid tumors

Oxyphilic tumors (oncocytomas or Hurthle cell tumors) form a rare subgroup of thyroid tumors characterized by cells containing abundant mitochondria. The relationship between the mitochondrial proliferation and the pathogenes is of these tumors is unknown. We have assessed the expression of the mitoc hondrial ND2 and ND5 (subunits of the nicotinamide adenine dinucleotide deh ydrogenase complex) genes and the nuclear UCP2 (uncoupling protein 2) gene in 22 oxyphilic thyroid tumors and matched controls. The consumption of oxy gen in mitochondria from tumors was determined by polarography. ATP assays were used to explore the mitochondrial respiratory chain activity and the o xidative phosphorylation coupling in seven fresh thyroid tumors and control s. Adenosine triphosphate synthesis was significantly lower in all the tumo rs, compared with controls, suggesting that a coupling defect in oxidative phosphorylation may be a cause of mitochondrial. hyperplasia in oxyphilic t hyroid tumors.