Oxidative Stress and Carcinogenesis: Prevention by Antioxidative Phytochemicals Acting on Different Molecular Targets

摘要

Overproduction of reactive oxygen species (ROS) through endogenous or exogenous insults can cause oxidative stress. In carcinogenesis also, the unregulated or prolonged production of reactive species damages critical biomolecules and eventually results in several biological effects ranging from alterations in signal transduction and gene expression to mitogenesis, transformation, mutagenesis and cell death. ROS including hydroxyl radicals, superoxide anion, hydrogen peroxide and nitric oxide are very transient species due to their high chemical reactivity that leads to lipid peroxidation and oxidation of DNA and proteins which have been implicated in the etiology of a wide array of human diseases, including cancer. Oxidative stress can be ameliorated by the consumption of antioxidants containing fruits and vegetables which prevent chronic diseases including cancer by eliminating ROS. Both positive and negative correlations are seen between antioxidant and anticancer activity of these antioxidant phytochemicals. Many in vitro and in vivo studies of whole plant extracts and bioactive components have also proved their anti oxidative and anticancer effects on cancer cell lines and animal models. In particular, signal transduction pathways, including NF-κB, COX-2, cyclin dependent kinases, Bcl2 etc. are known to be activated by ROS, and they lead to the transcription of genes involved in cell growth regulatory pathways which in turn cause tumorigenesis. In this review we have primarily focused on the role of phytochemicals in the inhibition of the oxidative stress for the prevention of cancer by acting on different molecular targets.