ABSTRACT
Biomarkers are defi ned as cellular, biochemical or molecular alterations in biological media such as human tissues, cells, or fl uids (Hulka and Wilcosky 1988), that are objectively measured and evaluated as indicators of normal/pathogenic processes or pharmacological responses to therapies (Naylor 2003). Epidemiologists, physicians, and researchers are currently using biomarkers, in the diagnosis and management of pathologies, such as cancer, infections, immunological and genetic disorders (Hulka and Wilcosky 1988; Perera and Weinstein 2000; Naylor 2003). Blood, cerebrospinal fl uid, muscle, nerve, skin, and urine samples are employed to obtain information about healthy and diseased states. Several points must be considered before using biomarkers in clinical studies including potential measurement errors, bias, confounding, cost and acceptability (Mayeux 2004; Ioannidis 2011), and their validity is a complex process. Th erefore, the identifi cation of potential biomarkers provides a dynamic and outstanding tool to diagnose asymptomatic disease states and treat them accurately (Schulte 1992). Biomarkers of oxidative modifi cation of biomolecules have been examined in distinct disease states (Giustarini et al. 2009; Ziech et al. 2010). However, the clinical analyses of such biomarkers depend on the sample type (e.g., tissue, plasma, and urine), requirement of sample pretreatment, performance of analytical technique, and method to normalize concentration among diff erent biological samples, which are relevant factors to ensure reliable quantifi cation (Tamura et al. 2006). Oxidative stress is a common hallmark of a variety of diseases ranging from neurodegenerative disorders, diabetes and cancer. Th ere is a number of studies demonstrating an association with increased oxidative stress and carcinogenesis. However, the detection and/or use of biomarkers of oxidative stress in cancer treatment/diagnosis will only be relevant if the biomarkers detected can give us relevant information regarding the stage/malignancy of the cancer/tumor or the therapeutic outcome and prognosis to be expected. In this section we will only focus on those biomarkers of oxidative stress that have the potential to provide such information.
