Mitochondria play a vital role in cellular bioenergetics, providing energy via oxidative phosphorylation (OXPHOS) and metabolic intermediates. Aerobic ATP production is orchestrated by a multi-enzyme complex, which uses the electrons gained during oxidation of energy substrates to generate an electrochemical potential across the mitochondrial (mt) membrane that drives ATP synthase. Although there is evidence that mitochondrial function as well as mtDNA mutations might play a role in tumor formation and progression, combined analysis of mt-physiology and DNA alterations are lacking. We analyzed mitochondrial respiration using high-resolution respirometry (OROBOROS Oxygraph-2k). By applying various mitochondrial substrate-uncoupler-inhibitor combinations we dissected the contribution of mitochondrial electron transfer pathways to oxidative phosphorylation. Relative mtDNA copy numbers were determined by duplex qPCR, mtDNA mutations by next-generation sequencing (Ion Torrent Proton). Sequencing data were analyzed using our newly developed mtDNA-Server analysis pipeline (http://mtdna-server.uibk.ac.at). Significant differences in BE and CA tissue were found with respect to the respiratory capacities of Complex I- and Complex II-linked pathways (CI and CII). CA tissue exhibited lower CI-linked respiration which was compensated by higher CII-linked capacities. No correlation was found between mt-function and mtDNA copy number. A comparison of mtDNA sequence variations in BE and CA tissue revealed a significantly higher overall mutation rate in malignant tissue. Most interestingly, deleterious mutations in regions coding for Complex I components strongly correlated with a relative loss of CI-linked respiration in both CA and BE tissue. No statistically significant correlation of mt-mutation burden was found to tumor Gleason scores or patients serum PSA levels.
Funding: COMET K1 Center Oncotyrol Center for Personalized Medicine, K-Regio project MitoFit.
Presenting Author: Bernd Schöpf, Division of Genetic Epidemiology, Department of Medical Genetics, Medical University of Innsbruck, Schöpfstraße 4, 6020 Innsbruck, Austria. Email: Bernd.firstname.lastname@example.org