The Dual Role of Oxidative Stress in Lung Cancer

Abstract

Reactive oxygen species (ROS) are produced by several endogenous and exogenous sources, and their levels are controlled by several antioxidants. Oxidative stress results from an imbalance between ROS production and removal by antioxidant mechanisms. The risk factors which are commonly associated with chronic diseases (e.g., cancer) interact with the cells through the formation of ROS. These factors include stress, cigarette smoking, air pollutants, radiation, and infection. The lung is considered a target organ continuously affected by exogenous and endogenous ROS. There is now increasing evidence that there is association between oxidative stress and lung cancer. Interestingly, it was found that ROS could not only promote tumorigenesis, but also they have anti-tumorigenic effect. This dual role of ROS in cancers (e.g., lung cancer) relies on their amount, type, and the site of their production. For example, moderate amount of ROS was associated with tumor cell survival, proliferation, angiogenesis, and metastasis. On the contrary, excessive amount of ROS could induce tumor cell death. Thus, it is essential to investigate the dual role of ROS in cancers, for the development of novel therapeutic approaches targeting redox regulatory mechanisms.