Hypoxia/Reoxygenation-Induced Mitochondrial Reverse Electron Transfer: A Targetable Mechanism to Enhance...

Area of Science:

• Biochemistry
• Oncology
• Cell Biology

Background:

• Hypoxia-induced radioresistance is a significant challenge in non-small cell lung cancer (NSCLC) radiotherapy.
• Mitochondrial reverse electron transfer (RET) is a potential mechanism to overcome this resistance.

Purpose of the Study:

• To investigate if activating mitochondrial RET can enhance radiosensitivity in NSCLC by inducing oxidative stress.
• To explore the role of succinate metabolism in this process and its therapeutic potential.

Main Methods:

• Established an in vitro hypoxia/reoxygenation (H/R) model in A549 cells.
• Assessed reactive oxygen species (ROS), mitochondrial function, and metabolic alterations using various assays.
• Utilized mitochondrial inhibitors and dimethyl succinate (DM-S) to validate the RET mechanism.
• Evaluated radiosensitivity via clonogenic survival, apoptosis, and DNA damage markers (γ-H2AX).
• Conducted in vivo studies in tumor-bearing mice combining high oxygen, DM-S, and irradiation.

Main Results:

• H/R induced mitochondrial ROS via complex I-mediated RET, linked to high mitochondrial membrane potential and succinate accumulation.
• Exogenous DM-S amplified oxidative damage, DNA fragmentation, and mitochondrial disruption.
• Combination therapy significantly enhanced in vitro radiosensitivity, increasing apoptosis and reducing cell survival.
• In vivo, the combined treatment suppressed tumor growth, induced apoptosis, reduced hypoxia, and showed no toxicity.

Conclusions:

• Artificial activation of mitochondrial RET effectively enhances radiosensitivity in NSCLC.
• Succinate metabolism is a critical target for radiosensitization.
• Combining high oxygen with a succinate analog is a promising strategy for hypoxic NSCLC tumors.