Targeting succinate:ubiquinone reductase potentiates the efficacy of anticancer therapy
Björn Kruspig1, Kadri Valter1, Belma Skender2
1Institute of Environmental Medicine, Division of Toxicology, Karolinska Institutet, Box 210, Stockholm, SE-171 77, Sweden.
Abstract:
Mitochondria play a pivotal role in apoptosis: permeabilization of the outer mitochondrial membrane and the release of pro-apoptotic proteins from the intermembrane space of mitochondria are regarded as the key event in apoptosis induction. Here we demonstrate how non-toxic doses of the mitochondrial Complex II inhibitor thenoyltrifluoroacetone (TTFA), which specifically inhibits the ubiquinone-binding site of succinate dehydrogenase (SDH), synergistically stimulated cell death, induced by harmless doses of cisplatin in a panel of chemoresistant neuroblastoma cell lines. Apoptotic cell death was confirmed by cytochrome c release from the mitochondria, cleavage of poly ADP-ribose polymerase, processing of caspase-3, which is an important executive enzyme in apoptosis, and caspase-3-like activity. Methyl malonate, an inhibitor of the SDHA subunit partially reversed apoptosis stimulated by TTFA in SK-N-BE(2) neuroblastoma cells (NB), indicating that sensitization requires oxidation of succinate. In contrast, in IMR-32 NB cells, the same concentrations of TTFA markedly suppressed cisplatin-induced apoptosis. Comparison of oxygen consumption in cisplatin-resistant SK-N-BE(2) and cisplatin-sensitive IMR-32 cells clearly demonstrated impaired Complex II activity in IMR-32 cells. We also found that in SK-N-BE(2) cells co-treatment with cisplatin and TTFA markedly stimulated formation of reactive oxygen species (ROS), whereas in IMR cells, cisplatin-mediated ROS production was attenuated by TTFA, which explains apoptosis suppression in these cells. Thus, functionally active SDH is a prerequisite for the ROS-mediated sensitization to treatment by TTFA.
Insights
Non-toxic doses of the mitochondrial Complex II inhibitor thenoyltrifluoroacetone (TTFA) synergistically enhance cisplatin-induced apoptosis in chemoresistant neuroblastoma cells. This sensitization requires functional succinate dehydrogenase (SDH) and is mediated by reactive oxygen species (ROS) production.
Area of Science:
- Cell Biology
- Biochemistry
- Cancer Research
Background:
- Mitochondria are central to apoptosis induction.
- Outer mitochondrial membrane permeabilization and pro-apoptotic protein release are key events.
- Chemotherapy resistance remains a significant challenge in neuroblastoma treatment.
Purpose of the Study:
- To investigate the synergistic effect of thenoyltrifluoroacetone (TTFA) and cisplatin on neuroblastoma cell death.
- To elucidate the role of succinate dehydrogenase (SDH) activity and reactive oxygen species (ROS) in this interaction.
- To explore potential strategies for overcoming chemoresistance in neuroblastoma.
Main Methods:
- Treatment of neuroblastoma cell lines with non-toxic doses of TTFA and cisplatin.
- Assessment of apoptosis via cytochrome c release, PARP cleavage, and caspase-3 activity.
- Inhibition of SDH with methyl malonate to assess succinate oxidation.
- Measurement of oxygen consumption and ROS production.
Main Results:
- TTFA synergistically enhanced cisplatin-induced apoptosis in chemoresistant SK-N-BE(2) cells, confirmed by apoptotic markers.
- Apoptosis sensitization by TTFA required succinate oxidation and was linked to increased ROS production.
- In contrast, TTFA suppressed cisplatin-induced apoptosis in cisplatin-sensitive IMR-32 cells, correlating with impaired Complex II activity and reduced ROS.
- Functionally active SDH is a prerequisite for TTFA-mediated ROS-dependent sensitization.
Conclusions:
- Non-toxic TTFA can sensitize chemoresistant neuroblastoma cells to cisplatin via ROS-mediated apoptosis.
- SDH activity and ROS production are critical determinants of TTFA's effect on cisplatin-induced cell death.
- Targeting mitochondrial Complex II offers a potential strategy to overcome chemoresistance in neuroblastoma.
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