Oncogenes, oncogenesis, and oxygen radicals.
The role that free radicals in general and oxygen radicals in particular play in carcinogenesis has attracted considerable attention in recent years. The oxygen radicals are undesirable but inevitable products of aerobic metabolism in the normal living cell. The cellular antioxidant defense system maintains an appropriate balance between necessary oxidative events and those that are excessive. When this critical balance cannot be maintained because of the overloading of the cellular redox system, oxygen radicals can induce cell damage. They can influence carcinogenesis by inducing DNA damage from direct oxidation or indirectly from DNA-binding products of lipid peroxidation. Oxygen radicals can induce conformational changes in the plasma membrane by lipid peroxidation and protein degradation, thus influencing membrane-associated cellular activities. They are capable of affecting membrane-bound protein kinases, growth factors and their receptors, and, therefore, signal transduction and oncogene activation. Thus, the oxygen radicals can have a major influence on oncogenes and oncogenesis.