Mitochondria, oxidative stress, cancer, and aging

In human cells, the main source of reactive oxygen species (ROS) and oxidative stress are mitochondria, the organelles where oxidative phosphorylation take place. Although ROS are an inevitable by-products of respiration, they do not necessarily have detrimental effects; low doses of ROS can have beneficial effects on cells, and their production can be finely regulated in mitochondria. Increasing ROS levels and products of the oxidative stress, which occur in aging and age-related disorders, are related to progressive dysfunction of mitochondria, due to damage to mitochondrial DNA or to oxidation and damage of mitochondrial proteins, and are also present in cancer. This chapter focuses on the regulation of ROS production in mitochondria and on the mechanisms that lead to its dysregulation in aging and cancer.