Boosting cancer immunotherapy: the immunogenic and therapeutic potential of non-thermal plasma in head and neck cancer

Ondertitel:the immunogenic and therapeutic potential of non-thermal plasma in head and neck cancer

Korte inhoud:The immune system remains one of the strongest defense mechanisms against cancer and immune-engaging therapies have therefore become a cornerstone of modern cancer management. However, despite clear successes, treatments like immune checkpoint inhibition (ICI) still face significant limitations, especially in solid tumors with a hostile and immune-deprived tumor microenvironment (TME). While precision medicine aims to overcome these hurdles through personalized approaches, strategies with a broad application potential still have their value, especially when they can enhance tumor immunogenicity. During my PhD, I investigated the immunomodulatory capacity of non-thermal plasma (NTP) with the purpose to incorporate it as a potent adjuvant for current treatment options. The generated reactive oxygen and nitrogen species (ROS/RNS) in NTP are reported to induce oxidative stress and immunogenic cell death (ICD), and thus hold potential to enhance tumor immunogenicity and improve both innate and adaptive immune recruitment. Before assessing therapeutic efficacy, rigorous experimental considerations were necessary. In research chapter 2, I demonstrated that fluorophore-induced phototoxicity alters intracellular redox homeostasis and increases cancer cell sensitivity to NTP, raising awareness for a major confounding factor for redox-based therapy research. This work highlights the importance of methodological optimization in fluorescence-based imaging studies, especially in the growing field of complex 3D tumor models and live-cell tracking. Building on previous research establishing NTP as a bona fide ICD inducer, I investigated in my research chapter 3 whether NTP could enhance the immunogenicity of conventional cisplatin (cis-diamminedichloroplatinum (II), CDDP) administration, a standard treatment for head and neck cancer squamous cell carcinoma (HNSCC) and many other tumor types. My findings reveal synergistic cytotoxic effects of NTP-CDDP combination therapy, with significant damage-associated molecular pattern release and cytokine modulation, underlining the robustness of the immune-stimulatory capacity of NTP. Moreover, the gold standard in vivo vaccination assay confirmed that NTP-CDDP enhances anti-tumor immunity, leading to nearly 40% protection against tumor rechallenge in a syngeneic mouse model. Despite the growing body of evidence for NTP’s immunomodulatory potential, few studies have considered relevant combination with current standard-of-care, a critical gap in the field preceding clinical introduction which was addressed here. While adaptive immunity remains a major focus in immunotherapy, innate immunity, particularly natural killer (NK) cells, play a crucial role in anti-cancer immunity. In research chapter 4, I explored NTP’s effects on tumor-associated NK cell ligands, demonstrating that oxidative stress induced by NTP modulates key immune checkpoints. Several inhibitory ligands, including TIGIT-axis markers and checkpoint CD73, were immediately downregulated, while MICA/B molecules as potent activators of NK cells, were upregulated 24 hours post-treatment. These findings suggest that NTP not only induces direct tumor cytotoxicity but also remodels the tumor immune landscape at various levels, making it a promising immune-modulating therapy. As future perspectives of this work, several concrete directions can be envisioned: (i) NTP’s therapeutic potential could extend beyond HNSCC, serving as an adjuvant strategy to enhance immunogenicity in other malignancies, such as non-small cell lung cancer and triple negative breast cancer, where ICI therapy faces challenges with low and variable response rates; (ii) combining NTP with other endoplasmic reticulum stress-inducing therapies may provide a dual, systemic-local, approach to disbalance cancer’s redox homeostasis, pushing tumor cells over their oxidative threshold while simultaneously triggering stress response pathways linked to ICD; (iii) fundamental questions remain regarding NTP’s immunomodulatory effects, particularly on key immune checkpoints (e.g., PD-1/PD-L1, CTLA-4, and LAG-3) and the direct influence on immune cells within the TME. These opportunities are further explored in review chapter 5, with a focus on intercellular communication via gap junctions. Herein, I provided an extensive overview of their complex role in cancer, demonstrating both pro- and anti-tumoral effects. In addition, the therapeutic potential of targeting gap junctions and their vulnerability to reactive species (ROS) is discussed, while also exploring combinatorial strategies, e.g. combining selective connexin or gap junction modulation with redox-based therapies like NTP, to enhance anti-cancer efficacy. Besides these research aspects, also technical advancement like treatment standardization and sophisticated application tools will be required to integrate NTP into clinical immunotherapy approaches. Taken together, in this thesis, I established NTP as a potent immunogenic adjuvant to standard cancer therapies, with broad implications for enhancing innate and adaptive immune responses. The ability of NTP to sensitize tumors to chemotherapy, modulate immune ligands, and improve anti-tumor immunity positions it as a promising candidate for clinical translation in an adjuvant setting for patients in high need of additional treatment options.

Jaar van publicatie:2025

Trefwoorden:Human medicine

Toegankelijkheid:Open