Exploring How Reactive Oxygen Species Contribute to Cancer via Oxidative Stress

Cancer remains a major global health burden driven by genetic, metabolic, and microenvironmental alterations. Although reactive oxygen species (ROS) and oxidative stress have long been implicated in cancer biology, current understanding remains fragmented and, in several areas, conceptually disputed considering how ROS and oxidative stress thresholds determine the switch between tumor-promoting signaling and cytotoxic outcomes, and whether redox-based therapies can be safely and selectively applied across different cancer types. Moreover, existing studies often examine isolated pathways or single ROS, leaving unanswered the question of how spatial and temporal ROS dynamics and oxidative stress responses shape carcinogenesis, metastasis, and therapeutic resistance. This review moves beyond descriptive summarization by critically examining unresolved mechanistic gaps, including (i) how ROS and oxidative stress interact with epigenetic and metabolic reprogramming, (ii) the context-dependent role of ROS-driven oxidative stress within the tumor microenvironment and immune evasion, and (iii) why ROS-targeting and oxidative stress-modulating therapies have shown inconsistent clinical translation despite promising preclinical data. We highlight areas of consensus as well as conflicting evidence, synthesizing recent advances across multiple cancer types to clarify where ROS and oxidative stress function as drivers, modulators, or vulnerabilities. Finally, we outline emerging research priorities, such as real-time redox profiling, subtype-specific targeting strategies, and combination approaches, to guide the development of more precise and effective ROS- and oxidative-stress-based interventions.