Melatonin orchestrates tumor-selective reverse electron transport through mitochondrial Complex I in head and neck squamous cell carcinoma (HNSCC), eliciting site-specific bioenergetic disruption via modulation of NADH/ubiquinone oxidoreductase flux, thereby augmenting ROS-mediated activation of the intrinsic apoptotic cascade through redox-sensitive BAX oligomerization and cytochrome c efflux (Florido et al., 2022a). This evidence concerns the gene CYCS and head and neck squamous cell carcinoma.