Redox Homeostasis and Cellular Antioxidant Systems: Crucial Players in Cancer Growth and Therapy

Figure 1

Redox homeostasis is a balance of ROS generation and elimination. Mitochondria, NAPH oxidase (NOX), and endoplasmic reticulum are the three major intracellular sources of ROS. Anion superoxide () is the principal form of ROS and can be rapidly converted into hydrogen peroxide (H₂O₂) by superoxide dismutase (SOD). H₂O₂ can be catalyzed to hydroxyl radical () in the presence of Fe²⁺ or Cu²⁺ ions or be converted to H₂O by catalase. The amount of H₂O₂ is decisive for the cell fate: low and intermediate levels of the peroxide stimulate loss of cell homeostasis and increased adaptation to stress leading to neoplastic transformation while high levels induce cell death.