Benzyl isothiocyanate induced mitochondrial dysfunction via ROS generation sensitizes head and neck squamous cell carcinoma to cisplatin and radiation

Accounting for nearly 4% of all cancer diagnoses and 2% of all cancer-related mortality in the United States, head and neck squamous cell carcinoma (HNSCC) originates from the squamous epithelial cells lining the mucosal surfaces of the oral cavity, pharynx, larynx, lips, and sinonasal tract. HNSCC is notable for its resistance to conventional therapy, with mitochondria serving as central mediators through multifaceted contributions, including the regulation of cellular signaling pathways, modulation of energy metabolism, and control of apoptotic responses. Although modulation of mitochondrial pathways has emerged as a potential therapeutic target, its role in HNSCC progression and treatment response remains incompletely understood. Benzyl isothiocyanate (BITC), a naturally derived bioactive compound found in cruciferous vegetables, selectively induces excessive reactive oxygen species (ROS) and depletes glutathione in cancer cells, leading to mitochondrial dysfunction and impaired bioenergetic flexibility. Building on the role of mitochondria in therapeutic resistance, we explored the effects of BITC in sensitizing paired primary and metastatic HNSCC cell lines isolated from two patients to cisplatin (CDDP) and radiotherapy (RT). Cell viability and caspase-3/7 activity were assessed at 72 hours on HNSCC cells pretreated for 1 hour with BITC, followed by 24 hours of cisplatin with or without the addition of 4 or 8 Gy radiation. Electron Paramagnetic Resonance (EPR) and glutathione (GSH) rescue assays were used to measure oxidative stress, identify different types of ROS produced, and investigate resistance mechanisms to therapy after up to 24 hours of BITC exposure. Real-time fluororespirometry was employed to evaluate the overall mitochondrial bioenergetic status, also following up to 24 hours of BITC exposure. In all four HNSCC lines, BITC treatment significantly increased sensitivity to both CDDP and RT by inducing apoptosis through Caspase-3/7 activation. BITC treatment effectively induced ROS, which was rescued by the addition of GSH. Within one hour, BITC exposure induced a pronounced decline in mitochondrial respiration and Bioenergetic Health Index (BHI), followed by a transient increase in respiration at 3-5 hours, suggesting metabolic reprogramming. However, by 24 hours, metabolic exhaustion culminated in cell death. Our findings demonstrate that BITC disrupts mitochondrial bioenergetics, limits metabolic adaptability, and increases the efficacy of standard-of-care therapies through excessive ROS production, supporting its potential as a novel adjuvant therapeutic strategy for HNSCC.