FIGURE 1.

Generation of reactive oxygen species (ROS) and their effects. Reactive oxygen species can be generated by multiple endogenous and exogenous factors, which, in turn, lead to various biological consequences. Low levels of ROS act as intracellular second messengers. Moderate levels of ROS are beneficial to cancer cells because they can increase cancer metabolism and growth signaling, and inhibit antioxidants, which contribute to oncogenesis. Conversely, high levels of ROS can lead to cell death induced by DNA damage