Targeting redox homeostasis in cancer: Inhibitors of Reactive Oxygen Species regulating cellular signalling pathways and their therapeutic implications.

Reactive oxygen species (ROS) function in a vital dual role in cellular homeostasis and disease processes, with special reference to cancer. Low to moderate ROS levels are signalling molecules that are involved in cell proliferation and survival, whereas high ROS levels cause oxidative damage leading to cell death. This review classifies known inhibitors based on targeting signalling pathways that lower ROS levels, highlighting their molecular mechanisms, including free radical scavenging, metal chelation, mitochondrial disruption, and enzyme modulation. The role of ROS in cancer is investigated through its pro-tumourigenic functions, e.g., genomic instability, metastasis, resistance to apoptosis and its antitumourigenic effect through ROS-mediated cell death and increased therapeutic sensitivity. Moreover, we also describe newly developed therapeutic techniques, including redox modulation, drug delivery by nanocarrier, and the notion of ROS threshold as a therapeutic window. Even with the promise of ROS-targeted therapies, clinical translation remains challenging, emphasising the importance of accurate in vivo quantification and tumour-specific intervention. In the end, this review cites the potential of ROS modulation as a therapeutic and yet also a risk, calling for precision-based intervention in cancer redox therapy.