Oxidative stress and its role in cancer.

Reactive oxygen species (ROS) can damage lipids, nucleic acids, and proteins, thereby altering their functions. When a balance between production of ROS and antioxidative defense is disturbed, state of oxidative stress occurs. Oxidative stress leads to many diseases. There are few biomarkers that are used for better understanding how oxidative stress is involved in cancer pathophysiology. This review focuses on 8-hidroxy-2-deoxyguanosine (8-OHdG) and antioxidative enzymes as biomarkers for measurement of oxidative stress in different types of cancer. This review also deals with the product of lipid peroxidation, malondialdehyde (MDA), and across a variety of cancers. To address this aim, analysis of studies of breast, prostate, lung, colon, cervical, ovarian, brain, bladder, renal, thyroid cancer, and chronic lymphocytic leukemia has been conducted. In general, levels of antioxidative enzymes are mostly lower in cancer patients, while 8-OHdG and MDA are higher. Further research is needed, with focus on correlation levels of these biomarkers and advancement of the disease. Moreover, all studies explored the idea of those biomarkers as a useful tool in determining the levels of oxidative stress. Some of the studies proposed their potential in defining the stage of tumor progression.