Alteration of mitochondrial DNA in human oncocytomas

Oncocytoma, a benign solid tumor, occurs in a number of organs but most frequently in the kidneys. Its oncocytes display an intensely eosinophilic cytoplasm due to presence of numerous mitochondria. Mitochondrial DNA analysis of six renal cell oncocytomas and adjacent renal tissue was performed using five restriction endonucleases. In the Hinfl restriction pattern, an additional 40 bp band was noted. This new band was demonstrated in all oncocytomas but in none of the corresponding renal tissues or additionally tested renal carcinomas. By reisolating and hybridizing this band to the mitochondrial genome, its sequence was localized within the cytochrome c oxidase subunit I gene. The data suggest that a molecular alteration of mitochondrial DNA is specific for oncocytomas, and this constitutes the first observed mitochondrial DNA change in a human solid tumor.