Molecular mechanisms of Cr(VI)-induced carcinogenesis.

Although Cr(VI)-containing compounds are well documented carcinogens, their mechanism of action is still not well understood. Recent studies have suggested that reduction of Cr(VI) to its lower oxidation states and related free radical reactions play an important role in Cr(VI)-induced carcinogenesis. This article summarizes recent studies from our laboratory on (a) the reduction of Cr(VI) by ascorbate, diol- and thiol-containing molecules, certain flavoenzymes, cell organelles, intact cells, and whole animals; (b) free radical production in both non-cellular and cellular systems; and (c) Cr(VI)-induced DNA damage, activation of nuclear transcription factor KB (NF-kappaB), activator protein-1, p53, hypoxia-inducible factor-1, vascular endothelial growth factor, tyrosine phosphorylation, apoptosis, cell growth arrest, and gene expression profile.