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Mitochondrial complex I is deficient in renal oncocytomas

Helene Simonnet1, Jocelyne Demont, Kathy Pfeiffer

  • 1CGMC (Center of Molecular and Cell Genetics), Unit 5534 of the CNRS and the University Lyon 1 Claude Bernard, Villeurbanne, France. simonnet@univ-lyon1.fr

Carcinogenesis
|July 8, 2003
PubMed

Insights

Renal oncocytomas show a specific decrease in mitochondrial complex I, unlike malignant tumors. This deficiency may drive increased mitochondria and impaired ATP production in these benign kidney tumors.

Area of Science:

  • Nephrology
  • Mitochondrial Biology
  • Oncology

Background:

  • Renal oncocytomas are benign tumors with increased mitochondria, but the functionality of their oxidative phosphorylation (OXPHOS) system is unclear.
  • Previous studies noted increased mitochondrial DNA and OXPHOS complex activity, yet functional assessment was lacking.

Purpose of the Study:

  • To investigate the functional status of mitochondrial complex I in renal oncocytomas.
  • To differentiate mitochondrial alterations in oncocytomas from those in malignant renal tumors.

Main Methods:

  • Analysis of NADH dehydrogenase activity and protein content of mitochondrial complex I in oncocytomas.
  • Comparison of complex I alterations in oncocytomas with those in malignant renal tumors.
  • Assessment of complex I activity in peritumoral tissue.

Main Results:

  • Renal oncocytomas exhibit a specific decrease in mitochondrial complex I (NADH dehydrogenase) activity and protein content.
  • In contrast, malignant renal tumors show a parallel decrease in all respiratory chain complexes.
  • Complex I activity is also moderately reduced in tissue adjacent to oncocytomas.

Conclusions:

  • Complex I deficiency is a potential early event in oncocytoma development, triggering compensatory mitochondrial biogenesis.
  • Oncocytoma represents a third type of benign tumor linked to impaired mitochondrial ATP production.
  • The findings suggest oncocytomas arise from at least two sequential alterations affecting the mitochondrial respiratory chain.

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