Role of Oxidative Damage in Metal-Induced Carcinogenesis

Abstract

This chapter presents and discusses evidence of possible mechanistic involvement of oxidative DNA and protein damage in metal-induced carcinogenesis . Carcinogenic metals , e.g., Be, Cd, Cr, Co, Ni, and the metalloid As, are capable of generating various kinds of active oxygen and other reactive species in direct redox reactions with O2, O2 −●, H2O2, organic peroxides, and other cellular or tissue substrates, and/or indirectly—by inducing inflammation or unleashing physiological redox-active metals , Fe and Cu. The reactive species may damage all cell components, including DNA , RNA, free triphospho-nucleosides, proteins , and lipids, and exhaust cellular antioxidant defenses, e.g., deplete ascorbate. The damage may be aggravated by metal-assisted inhibition of DNA repair and histone demethylation systems. The association of oxidative damage with carcinogenesis is strongly supported by mutagenicity of DNA base products, strand breaks, apurinic sites, cross-links, and adducts typical for the attacking reactive species (oxygen-, carbon-, or sulfur-centered radicals), originating from oxidized amino acids and proteins , and 4-hydroxynonenal, a lipid oxidation product. Oxidative damage to nuclear proteins affects chromatin structure and gene expression, whereas such damage to regulatory proteins disturbs cell cycle and apoptosis. Thus, oxidative DNA damage may assist in the initiation while RNA and protein damage may facilitate the promotion and progression of cancer.