Non-thermal Plasma-Derived Reactive Oxygen Species Induces Cell Death in Radioresistant Head and Neck Cancer via the c-MET/STAT3 Pathway

Aims: Radiation therapy is a crucial treatment modality for head and neck squamous cell carcinomas (HNSCCs). However, acquired radiation resistance due to various mechanisms poses a major clinical challenge for therapeutic strategies. Intriguingly, reactive oxygen species (ROS) are versatile signaling molecules that promote various cellular functions at low concentrations but induce cell death at above-critical threshold levels. Results: Here, we found that radioresistant (RR) cancer cells exhibited reduced ROS levels and activation of the mesenchymal–epithelial transition factor/signal transducer and activator of transcription 3 (c-MET/STAT3) pathway. To target common vulnerabilities in RR cancers, we applied ROS enhancement therapy using nonthermal plasma-activated media (NTPAM), a novel approach that effectively inhibits the viability of RR cancer cells and is associated with inactivation of the c-MET/STAT3 pathway. Mechanistically, the downregulation of total c-MET is related to ROS-mediated lysosomal degradation. In addition, NTPAM suppressed tumor growth in a mouse model of RR cancer, concurrently reducing the levels of both the total and activated forms of c-MET and decreasing STAT3 phosphorylation. Innovations and Conclusions: These findings suggest that ROS enhancement therapy can overcome radiation resistance, thereby offering a compelling rationale for considering NTPAM as a stand-alone or complementary therapeutic approach for treating patients with HNSCCs. Antioxid. Redox Signal. 44, 182–196.