Nitric oxide in oncology: a two-faced Janus; [Оксид азота в онкологии: двуликий Янус]

Nitric oxide (NO) plays a significant role in the development of tumor processes, offering potential therapeutic options and serving as a target for influencing tumor growth. The aim of this review was to study the role of nitric oxide in the development of cancer, identify key signaling pathways in which NO is involved, mechanisms and methods of nitric oxide delivery in tumor therapy, as well as its impact as a therapeutic target. Results. Different isoforms of nitric oxide synthase (NOS) regulate nervous functions, vascular functions, and inflammatory processes. Elevated levels of induced nitric oxide synthase (iNOS) are associated with tumor development, and its inhibitors can suppress tumor growth. Research indicates that the effect of NO on tumors depends on the concentration and duration of exposure. Low concentrations stimulate the growth and metastases of tumor cells, whereas high concentrations exert an anti-tumor effect, enhancing therapy sensitivity. NO also impacts angiogenesis, metastases, and immune response. The application of NO in tumor treatment is challenging due to its short half-life and rapid diffusion. Developing various NO delivery methods, like gaseous NO and nanoparticles, holds promise for improving the effectiveness and control of distribution. Silicon and gold-based nanoparticles demonstrate potential for NO delivery, enhancing immune response and showing synergism with chemotherapy. Inhibitors of iNOS suppress tumor growth. Their combined usage with other agents, such as chemotherapy, displays promising results in tumor growth control. Further research and clinical trials are essential to determine optimal conditions for employing NO and iNOS inhibitors in cancer treatment. Overall, studying the influence of NO and iNOS on tumor processes represents a crucial area for developing novel treatment methods, underscoring the therapeutic potential of these molecules as agents and targets to enhance oncological outcomes. Conclusion. Nitric oxide and various isoforms of NOS, in particular induced NOS, play a vital role in the regulation of oncological processes. Research confirms the promise of nitric oxide in oncology as a potential antitumor agent. The use of iNOS inhibitors shows potential in controlling tumor growth, especially when combined with other drugs such as chemotherapy. In addition, the development of NO delivery methods is an area of active research that may improve the efficiency of NO distribution in the body and tumor. © Kaprin A.D. et al., 2024.